Climate-Responsive Design of Photovoltaic Façades in Hot Climates: Materials, Technologies, and Implementation Strategies

Abstract

With the intensification of global climate change, buildings in hot climate zones face increasing challenges related to high energy consumption and thermal comfort. Building integrated photovoltaic (BIPV) façades, which combine power generation and energy saving potential, require further optimization in their climate-adaptive design. Most existing studies primarily focus on the photoelectric conversion efficiency of PV modules, yet there is a lack of systematic analysis of the coupled effects of temperature, humidity, and solar radiation intensity on PV performance. Moreover, the current literature rarely addresses the regional material degradation patterns, integrated cooling solutions, or intelligent control systems suitable for hot and humid climates. There is also a lack of practical, climate specific design guidelines that connect theoretical technologies with real world applications. This paper systematically reviews BIPV façade design strategies following a climate zoning framework, summarizing research progress from 2019 to 2025 in the areas of material innovation, thermal management, light regulation strategies, and parametric design. A climate responsive strategy is proposed to address the distinct challenges of humid hot and dry hot climates. Finally, this study discusses the barriers and challenges of BIPV system applications in hot climates and highlights future research directions. Unlike previous reviews, this paper offers a multi-dimensional synthesis that integrates climatic classification, material suitability, passive and active cooling strategies, and intelligent optimization technologies. It further provides regionally differentiated recommendations for façade design and outlines a unified framework to guide future research and practical deployment of BIPV systems in hot climates.

1. Introduction

The construction sector constitutes a pivotal component within global energy systems, accounting for 40% of global final energy consumption during operational phases [1]. When considering embodied energy from material production and construction processes, this proportion escalates to 40% across the entire building lifecycle [2]. Notably, more than 50% of building energy consumption is allocated to maintaining optimal indoor thermal conditions through the mitigation of heating/cooling loads [3,4].

BIPV serve as a critical technological pathway for achieving nearly zero energy buildings (NZEBs) through solar energy utilization [5]. According to International Energy Agency (IEA) projections, photovoltaic technologies could supply approximately 25% of global electricity demand by 2050. BIPV systems have emerged as the optimal solar energy carrier, demonstrating dual functionality in reducing building energy consumption and enhancing indoor air quality through dynamic ventilation mechanisms [6]. BIPV is expected to play a significant role in achieving global energy sustainability, which is one of the strategic cornerstones of the United Nations Sustainable Development Goals [7]. Urban areas, while occupying merely 2% of Earth’s terrestrial surface, account for 70% of global energy resource consumption [8,9]. In metropolitan cores, high rise and super tall buildings have become dominant spatial solutions for land-use intensification. Glass curtain walls, favored for their lightweight properties and reduced structural load requirements, are extensively deployed in such vertical urban developments. Conventional BIPV research has predominantly focused on rooftop installations; however, the rooftop space of high-rise buildings is limited, with a significant portion occupied by mechanical, electrical, and plumbing equipment. As a result, the space available for PV installation on rooftops is restricted. In contrast, the potential of façade photovoltaics is increasingly highlighted [10,11,12] and has gradually gained widespread attention [13]. Recent advancements in BIPV technology have transformed building façades into renewable energy generation systems [14,15]. Beyond electricity generation, additional benefits can be achieved by considering the thermal behavior of BIPV systems and their impact on the building itself [16]. These added functionalities include façade protection, thermal and acoustic insulation, shading, and aesthetic enhancement [17]. The commercial landscape of BIPV is evolving rapidly, and it is expected that BIPV will soon be recognized as a primary building envelope material alongside traditional alternatives such as brick, wood, stone, and metal [18].

The global climate is experiencing a warming trend, with 2024 witnessing unprecedented heat waves sweeping across the world [19]. Many countries have been enveloped in extreme temperatures, continuously breaking historical records, while climate disasters, such as droughts and wildfires, have become more frequent. The tropical climate poses a series of climatic challenges for the adaptive reuse of buildings. In hot climate regions, buildings are inevitably sensitive to outdoor thermal conditions, leading to increased energy demand and reduced indoor thermal comfort [20,21]. The performance and reliability of photovoltaic systems are significantly affected by high temperatures and extreme climatic conditions [22].

As shown in

Table 1. Comparison of humid and dry hot climate characteristics (taking Singapore and the United Arab Emirates as examples).

Climate Characteristics	Humid Hot Climate (Singapore [24])	Dry Hot Climate (United Arab Emirates [25])
Temperature	The average temperature ranges from 23 to 33 °C There is a small diurnal temperature variation The high temperatures in summer are pronounced	During the summer, the average temperature can reach 39.4 °C, with extreme highs exceeding 45 °C In winter, the average temperature ranges from 23.3 °C to 25.3 °C There is a large diurnal temperature variation
Humidity	The annual average relative humidity is about 82%, and it is generally humid throughout the year	The annual average humidity is about 47%, and the air is dry
Precipitation	The average annual rainfall is 2113.3 mm	Annual precipitation is extremely low, the distribution of rainfall is uneven, and the evaporation rate is much higher than the amount of precipitation
Solar radiation intensity	The overall radiation intensity is moderately high The solar radiation fluctuates significantly due to cloud cover and humidity	There is abundant sunshine with high radiation intensity Solar radiation is consistently stable throughout the year
Availability of solar energy	It is susceptible to cloudy and rainy weather, which limits efficiency The coupled effects of heat and humidity need to be considered	Highly efficient and stable It is necessary to control the temperature rise in the components and the impact of dust accumulation on efficiency
Wind environment	Local monsoon effects influence building ventilation	The wind speed is relatively high, and dry, hot winds are common, which is conducive to heat dissipation Wind resistant design needs to be enhanced

, hot climates differ significantly. Arid and humid regions exhibit varying patterns in temperature range, humidity, precipitation, solar intensity, and wind dynamics. Elevated temperatures and relative humidity often accelerate material deterioration, promote mold growth, and increase energy demand—particularly for cooling and moisture control. In contrast to temperate zones, where energy efficiency efforts typically address heating, tropical regions demand context specific frameworks for adaptive building reuse and energy system transformation [23].

Glass surfaces represent the least thermally resistant component of the building envelope, allowing solar radiation to penetrate directly indoors and convert into sensible heat loads. The solar heat gain coefficient (SHGC) of conventional single pane glass can exceed 0.8, significantly increasing cooling loads. The extensive use of all glass façades may further exacerbate the thermal energy demand of indoor spaces, contradicting energy saving strategies [26]. Compared to conventional transparent glass, BIPV curtain walls exhibit superior thermal insulation and lower solar heat gain [27], effectively reducing cooling loads in buildings [28]. Consequently, BIPV curtain walls offer significant advantages in low latitude cities where air conditioning is the primary cooling method.

With ongoing advancements in materials science—such as perovskite photovoltaics and aerogel insulation [10,29,30,31]—as well as innovations in intelligent operation and maintenance [32,33], smart control, and low carbon technologies [34,35], glass architecture is undergoing a fundamental transformation in urban spatial ethics. Buildings are shifting from energy consumers to energy generating nodes, from enclosed containers to ecological interfaces [36]. PV façade glass modules, as functional components of advanced building envelopes, replace traditional façade materials, providing an attractive solution for both BIPV applications and highly glazed architecture [13,37].

1.1. State-of-the-Art of Photovoltaic Façade

Many scholars have currently focused on the research of photovoltaic façades: [38] summarized the latest advancements in solution processed thin film transparent photovoltaic (TPV), including perovskites, organics, and colloidal quantum dots, analyzing the pros and cons of emerging TPV based on material characteristics as well as aesthetic and power generation application requirements, and discussing promising TPV applications with a focus on agrivoltaics, smart windows, and façades. Reference [39] provides a comprehensive review of the impact of dust accumulation on the performance of PV systems and evaluates the effectiveness and economic feasibility of various cleaning methods. This research contributes to the efficient operation and long-term stability of PV modules, particularly in arid and desert regions. Reference [40] summarizes both static and dynamic control strategies for photovoltaic double skin façades (PV DSFs), offering a foundation for design and operation to support building sustainability goals. Reference [41] analyzes the performance optimization constraints and future directions of photovoltaic integrated shading devices (PVSDs), PV DSFs, and PV windows. Reference [42] reviews recent advancements and application cases of façade integrated PV technologies, emphasizing their critical role in enhancing building energy efficiency and achieving net zero emissions targets.

Although the energy efficiency optimization of BIPV systems has been extensively studied, most research has focused on a single climatic context, lacking systematic comparisons across diverse climate zones. The existing literature provides limited insight into the influence of climatic factors on photovoltaic performance, and comparative studies on system behavior in different climate types remain scarce [43]. In particular, there is a lack of synthesized strategies addressing climate adaptability of BIPV systems under hot climate conditions.

In contrast, this review distinguishes itself by integrating material durability, thermal regulation strategies, and intelligent system control within a climate zoning framework. It is, to our knowledge, the first review to systematically categorize BIPV façade strategies based on hot climate subtypes (humid vs. dry), and to synthesize cross disciplinary insights—including passive active cooling, lifecycle durability, and AI-based optimization—into a cohesive design reference. This approach bridges the gap between emerging technologies and their climate responsive architectural application.

1.2. The Aim of the Study

With the growing global emphasis on sustainable building design, the integration of PV technology into building façades has garnered significant attention [44]. Among these technologies, BIPV are particularly promising, as they not only generate renewable energy but also influence the thermal performance of buildings. In practical applications, BIPV design is closely linked to environmental and climatic conditions.

In hot climate regions, where solar radiation intensity and ambient temperatures are significantly high, BIPV façades present both opportunities and challenges. While they enhance on site energy generation, improper implementation may lead to excessive heat gain and thermal discomfort, potentially increasing cooling loads. Traditionally, energy efficiency strategies in hot climates have primarily focused on passive cooling techniques, such as shading, ventilation, and thermal insulation. However, as the dual functionality of BIPV—as both an energy generator and a building envelope modifier—gains recognition, establishing an integrated design framework becomes crucial. Recent studies have explored various PV façade configurations, considering factors such as ventilation strategies, material properties, and solar orientation. Despite these advancements, a comprehensive understanding of how to optimize BIPV façades for both thermal comfort and energy performance in hot climates remains incomplete.

To address these gaps, this review aims to consolidate and critically evaluate existing research on BIPV curtain wall design for hot climates by analyzing key design parameters, thermal performance strategies, and energy efficiency considerations across different climate zones. The objective is to establish a climate responsive design framework that supports both theoretical innovation and practical implementation.

Specifically, this review seeks to answer the following research questions:

• What are the critical material and encapsulation choices that enhance the thermal and functional durability of BIPV systems under hot arid and hot humid conditions?
• How do different passive and active cooling technologies compare in terms of energy performance, cost, and applicability across hot climate zones?
• What integrated design strategies (geometry, orientation, control systems) most effectively balance solar gain, indoor comfort, and electricity generation in tropical and desert cities?
• How can intelligent control and simulation tools be used to support dynamic optimization of BIPV systems in response to real time environmental conditions?

By addressing these targeted questions, this study aims to provide a structured, comparative understanding of the current knowledge base while outlining actionable pathways for future development.

2. Climate Responsive Principles and Characteristics in Hot Climates

2.1. Bioclimatic Design Principles

In the 1960s, growing concerns over environmental degradation led to the emergence of bioclimatic design as a recognized field of study. During this period, scholars such as Victor Olgyay began exploring the relationship between climate and architectural design. Olgyay proposed a design theory that emphasizes the integration of architecture with regional and climatic conditions, advocating human biothermal comfort as a fundamental principle of architectural design. His work focused on understanding the interactions between climate, geography, and human thermal perception [45].

The research, analysis, and implementation of bioclimatic architectural systems that contribute to reducing energy consumption are of critical importance. This involves considering both passive and active design strategies to achieve optimal building performance. Bioclimatic architecture represents an ecological shift in architectural paradigms, fundamentally integrating regional climatic factors with passive energy regulation mechanisms to reestablish the thermodynamic balance between buildings and their environment [46].

This design approach transcends traditional mechanistic construction thinking by incorporating climate parameters—such as solar radiation, atmospheric circulation, and temperature humidity fluctuations—into the spatial formation process as endogenous design variables. As illustrated by Ken Yeang’s Vertical Ecological Climates theory [47], the building envelope should function as a dynamic climatic buffer, actively responding to environmental variations.

As a fundamental component of bioclimatic design, passive solar technology operates as an energy potential utilization system based on the second law of thermodynamics. It enables passive energy conversion through the material properties of the building itself (e.g., the phase lag effect of thermally inert materials) and morphological topology (e.g., fluid dynamics optimization of wind guiding walls). Typical paradigms include the thermal storage and radiation coupling effect of Trombe walls and the cavity ventilation effect of double skin façades [48].

Olgyay’s bioclimatic design principles further emphasize that the effectiveness of such technologies depends on precise responses to the apparent motion of the sun. This requires dynamically adjusting the solar and thermal transmittance thresholds of shading components based on seasonal variations in solar declination.

The bioclimatic design methodology highlights the multidimensional synergy between climatic elements and building systems [49], with technical implementation structured into three levels of integration:

• Thermodynamic level—Delaying heat transfer through thermal resistance gradient distribution in the building envelope and latent heat storage using phase change materials;
• Optical level—Balancing visible light transmission and near-infrared radiation reflection by employing spectrally selective glazing, such as Low E glass;
• Fluid dynamics level—Enhancing the built environment’s wind performance through computational fluid dynamics (CFD) simulations, creating self-organized air convection cooling pathways.

This multi physics coupled design approach has been proven to reduce air conditioning loads by 56–72% [50]. Driven by carbon neutrality goals, the application of bioclimatic principles has extended beyond individual buildings to encompass urban heat island (UHI) mitigation. This systemic design strategy integrates key technical parameters, including thermodynamically optimized morphological topology (solar azimuth response coefficient ≥ 0.87), microclimate regulating landscape configurations (vegetation shading efficiency η ≥ 0.63), and climate adaptive construction using thermally inert materials (phase change temperature differential ΔT ≤ 3 °C). According to the 2022 UNEP report, the comprehensive implementation of bioclimatic design can reduce the life cycle carbon emissions of buildings by 42–58%, significantly outperforming current green building standards in terms of efficiency [51].

2.2. Energy Consumption Characteristics of Buildings in Hot Climates

The Köppen climate classification system employs quantitative relationships among temperature, precipitation, and vegetation to provide a scientific basis for climate adaptive building design. According to this system, hot climates primarily include the tropical climate type (A)—specifically, tropical rainforest (Af), tropical monsoon (Am), and tropical savanna (Aw/As)—as well as the arid climate type (B), which comprises tropical desert (BWh) and tropical steppe (BSh) climates (Figure 1).

As a representative city within the tropical rainforest climate (Af) zone, Singapore offers a valuable case study due to its combination of high ambient temperature, persistent humidity, and minimal seasonal variation (typical daily temperatures range from 23 °C to 32 °C). Its extremely high urban population density and intensive land-use have led to significant environmental challenges, including elevated building cooling loads and intensified UHI effects [5]. These factors make Singapore particularly sensitive to climate-induced energy demand and underscore the critical need for climate responsive façade technologies. Consequently, BIPV systems in such dense equatorial cities must simultaneously address issues of solar control, thermal regulation, and limited installable area, making them an ideal testing ground for integrated and adaptive design strategies.

Climate factors are critical determinants of building thermal performance and indoor comfort [53]. In hot climates, thermal loads dominated by radiation arise from strong solar radiation and the high absorptivity of building envelopes. The spatiotemporal heterogeneity, material sensitivity, and moisture heat coupling effects contribute to significant cooling energy consumption and thermal comfort challenges. Furthermore, high temperatures, intense solar radiation, dust, and high humidity are key environmental factors that affect the efficiency, lifespan, and overall performance of PV modules [54]. In such climates, solar radiation is the primary driving force behind building thermal loads, with intensities reaching 800–1100 W/m², leading to cooling loads accounting for 60–75% of the total—substantially higher than the 30–45% observed in temperate climates [55]. Solar radiation consists of direct, diffuse, and reflected components, with direct radiation contributing the highest proportion (approximately 70%–80%) and serving as the main source of building cooling loads [56].

Research on the performance of tropical buildings needs to consider the impact of changing weather conditions [57]. Buildings in hot climates exhibit pronounced diurnal variations in energy consumption. Solar radiation peaks at midday, reaching instantaneous values of up to 1000 W/m² [58], which results in cooling load peaks of 120–150 W/m—3–5 times greater than nighttime loads [59]. Moreover, thermal conduction exhibits a lag effect; for example, common concrete walls (with a thermal inertia index > 6.0 [60]) absorb significant solar radiation and store heat during the day, delaying the indoor temperature peak by 4–6 h [61] and markedly increasing nighttime air conditioning energy use [62]. Additionally, the solar radiation intensity incident on different building façades varies. In the afternoon, the sun’s low altitude produces a near vertical incidence on the west façade, enabling deep penetration of radiation; through conduction and long wave radiation, a heat flux density of 950 W/m² is transferred indoors—accounting for 38% of the total daily cooling load—whereas the north façade, receiving the least solar radiation, contributes only 12% [26].

Climate significantly influences the degradation rate of material performance. Compared to low temperature areas, PV modules in high temperature zones degrade more rapidly, with more pronounced discoloration and delamination of encapsulant materials (EVA) [63]. Moisture is the primary driver of performance deterioration in building envelopes, causing material functional decay through multiple damage pathways: it triggers electrochemical corrosion of metal components, promotes microbial growth, accelerates matrix cracking during freeze–thaw cycles, and induces stress related damage due to hygroscopic expansion. Moreover, increased moisture content in material pores leads to a decline in thermal performance, directly contributing to higher building energy consumption. The combined effect of heat and humidity in wet climates generates latent dehumidification loads, resulting in significantly higher air conditioning dehumidification energy consumption compared to dry regions [64]. In contrast, buildings in dry and hot areas commonly face issues related to high daytime temperature peaks and large diurnal temperature differences. In these regions, solar radiation is predominantly direct, with a high proportion of infrared radiation [65].

3. Sustainable Materials

The three main types of BIPV materials are monocrystalline silicon, polycrystalline silicon, and thin film coatings (such as CdTe, GaAs, and CIGS) [66], while some less common materials include non-silicon versions, such as DSSC, PSC, QDSC, and OPV [67,68]. In response to climatic conditions, transparent BIPV modules require multi-parameter optimization to achieve the proper balance between energy generation per unit area and energy savings. A highly customized, climate specific design that combines thermal (insulation U value), optical (visible light transmittance and solar heat gain), and electrical (Wp/m²) performance is necessary to ensure the broad acceptance of emerging BIPV technologies.

3.1. Semiconductor Materials

The thermal performance of photovoltaic façades is critically determined by their material composition [69]. In hot climate applications, the U value and Temperature Coefficient (TC) emerge as primary material indices governing indoor thermal environmental quality.

The performance of PV cells is primarily determined by key parameters, including the short circuit current density (Jsc), open circuit voltage (Voc), and fill factor (FF). Temperature fluctuations critically influence these parameters, thereby affecting overall solar cell efficiency. Reference [70] systematically investigated the temperature dependent performance (273 K–523 K) of solar cells fabricated from various semiconductor materials (e.g., Ge, Si, GaAs, InP, CdTe, and CdS). The study revealed that PV efficiency typically decreases with rising temperatures, a phenomenon notably attributed to the significant reduction in Voc, whereas Jsc exhibits a marginal increase.

The decline in overall efficiency is driven by the exponential growth of the reverse saturation current density under elevated temperatures. Substantial efficiency losses were observed at high temperatures; for instance, silicon-based cells demonstrated a reduction from 27.19% at 298 K to 15% at 423 K. These findings underscore the critical impact of thermal management on PV performance, particularly for materials like Si, where efficiency degradation correlates strongly with temperature induced increases in carrier recombination and leakage currents.

The TC, a critical metric quantifying the temperature sensitivity of PV device performance, enables the systematic evaluation of material suitability across climatic conditions. Materials with lower absolute TC values demonstrate superior thermal stability and are preferred for deployment in hot climates. As demonstrated in [71], outdoor testing under Hong Kong’s tropical conditions revealed minimal temperature induced degradation in thin film amorphous silicon (a Si) solar cells, where a temperature increase of 15.6 °C resulted in only a 0.29% reduction in conversion efficiency. Comparative TC analysis reveals distinct thermal responses among materials:

• PSC exhibits a TC range of 0.08% to 0.36% per K [72];
• CdTe exhibits a TC range of 0.24% to 0.26% per K [73];
• CIGS demonstrates a TC of 0.36% per K [74];
• Monocrystalline silicon (c Si) displays higher sensitivity, with a TC range of −0.45% to −0.50% per K [74];

PSC materials belong to the third generation of photovoltaic technologies. These materials achieve power conversion efficiencies (PCE) of approximately 23%, comparable to conventional silicon-based solar cells [75]. They offer additional advantages including tunable transparency, color variability, and mechanical flexibility [76]. PSC materials exhibit relatively stable bandgaps with rising temperature and show moderate temperature dependence in carrier mobility and lifetime. As a result, their photovoltaic performance degrades more slowly under short term thermal stress. Notably, PSCs demonstrate a temperature coefficient for maximum power output as low as −0.08 rel%/K, outperforming all previously reported photovoltaic technologies in this regard. However, a low temperature coefficient indicates short-term thermal tolerance, not long-term stability. Under prolonged exposure to high temperatures, PSC performance still tends to degrade. Addressing this limitation has become a key focus in efforts to scale PSCs commercially. For instance, a field study conducted in Cyprus—a high temperature, high irradiance region—tested 4 cm² mini modules over two years and found that the most stable modules retained approximately 78% of their initial PCE after one year [77].

While CdTe and CIGS demonstrate superior thermal stability due to their lower TC values, energy yield in real world applications depends on multiple factors. Notably, ref. [74] observed that c Si modules with a TC of −0.43% in Dubai’s desert climate outperformed CIGS counterparts by 13.6% in annual energy yield, despite c Si’s more pronounced efficiency degradation at elevated temperatures. This underscores that TC alone cannot dictate material selection; spectral response, long-term degradation rates, and site-specific installation conditions must be holistically evaluated.

The U value refers to the rate of heat transfer—by conduction, convection, and radiation—through a building element (either homogeneous or composite) due to the temperature difference between its two surfaces. Particular attention has been paid to thermal performance under Singapore’s tropical climate. Field measurements have shown that a BIPV curtain wall combined with Low E glazing yields the lowest U value and best thermal performance, suggesting that this combination is the most feasible energy saving solution for high window to wall ratio (WWR) façades in tropical climates like Singapore [78]. However, different BIPV technologies vary in their sensitivity to solar spectral components. Dye sensitized solar cells (DSCs) and organic solar cells (OSCs) rely primarily on the visible spectrum, resulting in relatively stable efficiency under various climatic conditions. In contrast, technologies such as copper indium gallium selenide (CIGS), monocrystalline silicon (c Si), and polycrystalline silicon (mc Si) show significantly reduced efficiency under cloudy conditions due to their greater dependence on infrared radiation [18].

Furthermore, the correlation between PV cell temperature and solar irradiance is stronger than its correlation with ambient air temperature [79]. In photovoltaic modules, unconverted absorbed solar radiation is one of the primary causes of cell temperature rise. The impact of temperature on PV module output characteristics varies under different irradiance levels. At low irradiance, temperature has a more significant effect on the Voc. However, as irradiance increases, the influence of temperature on Voc and peak power output gradually decreases, following a stepwise pattern. Nonetheless, under high irradiance conditions, the unconverted solar radiation is dissipated as heat, further exacerbating the temperature rise in the PV module.

3.2. Encapsulant Materials

Humidity ingress is a critical driver of PV module degradation. Encapsulant materials must simultaneously protect active components from moisture and oxygen while maintaining optical transparency, flexibility, and adhesion. In humid hot environments, prolonged exposure to heat and moisture accelerates the deterioration of encapsulant layers and electrical interconnects, making moisture resistance a pivotal performance metric for PV systems operating under such conditions. Encapsulation materials are known to be the most susceptible to aging in standardized photovoltaic modules [80]. Reference [81] identified temperature and humidity as synergistic degradation accelerators, revealing that at elevated temperatures (with relative humidity ≈ 50%), the degradation rate increases by approximately 12 fold compared to standard operating conditions. It mainly includes the following three key degradation pathways:

• Encapsulant Hydrolysis: EVA, a widely used encapsulant, undergoes hydrolysis to produce acetic acid, which corrodes metallic electrodes. In tropical (Class A) and humid subtropical (Cfa) climates, this process reduces module lifespans to below 20 years, significantly shorter than in arid regions (e.g., desert BWh climates) [82].
• Backsheet Permeability: Highly water soluble backsheet materials exacerbate moisture ingress, amplifying hydrolysis risks in encapsulants [83].
• Interfacial Delamination: Humidity induced weakening of interlayer adhesion promotes delamination, compromising mechanical integrity.

In actual operation, the temperature of photovoltaic modules can reach above 90 °C. Therefore, encapsulation materials with higher melting points and broader melting ranges provide greater stability for photovoltaic modules [84]. A simple and low-cost polymer–glass laminated encapsulation has been shown to effectively suppress perovskite outgassing decomposition. This approach enabled MA⁺ containing mixed perovskite devices to operate for over 1800 h under damp heat testing conditions of 85 °C and 85% relative humidity [85]. Measurements have shown that Polyolefin Elastomer (POE) materials, with superior hydrolysis resistance and chemical stability, exhibit higher reliability [86]. Long-term studies in humid and hot regions of China have proven that the optical losses caused by the yellowing of EVA (ethylene vinyl acetate) are a core factor in power degradation (due to a decrease in short circuit current). Backsheet cracking accelerates moisture ingress and induces corrosion, though it does not directly affect electrical performance. However, the weather resistance of the backsheet is a key factor in preventing mechanical performance degradation and ensuring the longevity of the materials [87].

Table 2. Performance comparison of three transparent encapsulation materials.

Materials	EVA [82,83,84,88,89]	POE [84,88,89]	TPO [84,88,89]
Moisture and heat resistance	Low	High	Middle
The melting temperature before aging	60–64 °C	71–75 °C	78–94 °C
The thermal degradation temperature of commercial encapsulation films	260 °C	370 °C	340 °C
The rate of crystallinity change during the 85 °C aging test	1% 1.5%	0% 0.5%	1 1.5%
Optical stability	Prone to yellowing	Maintains a light transmittance of over 90%	High light transmittance (with stable crystallinity)
Yellowness index	0.74 2.86	2.01 3.63	1.44 2.71
Situations of application	dry climates/short-term, low-cost applications	Humid and hot climate	Arid climate with high solar radiation
Advantages	Low cost and mature manufacturing process	High weather resistance and compatibility with double glass modules	High temperature resistance and anti-aging properties
Limitations	Humid heat lifetime is less than 20 years	UV absorbers need to be added	The cost is relatively high

presents a comparative analysis of three types of transparent encapsulation materials. As the demand for higher resistance to heat, humidity, and radiation increases, encapsulation technologies have been gradually optimized to adapt to extreme climate conditions.

In addition to material improvements, some researchers have explored innovative structural designs to enhance durability. For instance, ref. [90] proposed a dual layer edge sealing structure for thin film PV modules, which theoretically reduces moisture permeability by two orders of magnitude compared to conventional single layer EVA encapsulation. This innovation addresses the poor moisture resistance of EVA materials; however, its long-term performance remains to be validated.

4. Sustainable Technology

4.1. Cooling Technology

The efficiency and power output of PV cells are significantly influenced by temperature [91]. A 1 °C reduction in temperature can extend the lifespan of PV modules by approximately 7%, which is equivalent to about two years. However, in hot climates, high ambient temperatures and restricted natural convection result in low air-cooling efficiency. Additionally, thermal radiation between densely packed PV arrays leads to mutual heating, while the operation of PV panels further increases cell temperatures. Therefore, reliable cooling technologies are crucial for the development of BIPV in hot climates.

4.1.1. Passive Radiative Cooling (PRC)

PRC is a cooling strategy that cools objects without the need for electricity or resources [92]. PRC can be categorized into Daytime Radiative Cooling (DRC) and Nighttime Radiative Cooling (NRC), with DRC technology first realized in 2014 [93]. A fluorescent-based, passive, colorful radiative cooling material (PCRC) was developed, which utilizes fluorescence effects to convert absorbed ultraviolet visible light into long wavelength radiation. This reduces heat absorption while providing color, addressing issues such as glare and excessive cooling in winter commonly found in traditional white or silver radiative cooling materials. Field tests demonstrated that PCRCs performed comparably to DRCs in Australia’s hot and dry climate, particularly for orange materials. Passive cooling using a combination of heat pipes and radiative cooling has been applied to control PV temperatures in extreme desert environments [94]. In the Atacama Desert, this method lowered the average PV operating temperature by 2 °C in both summer and winter. This led to notable gains in conversion efficiency and total energy yield. The estimated LCOE was between $0.065 and $0.089 per kWh, offering a clear economic benefit.

Some studies have also focused on the development of adaptive radiative thermal management structures and materials capable of operating efficiently in both daytime and nighttime conditions. An innovative Rotatable Radiative Cooling Photovoltaic (RRC PV) system was proposed [95], which alternates between solar energy harvesting during the day and radiative cooling at night through rotational module adjustments. This system is particularly relevant for high density urban areas with limited building surfaces. Economic analysis indicates that in hot climates, the system has a relatively short payback period (PP) of approximately 5.2 years, making it suitable for buildings with high cooling demands.

A porous array polymethyl methacrylate film was introduced [96], capable of achieving a temperature reduction of approximately 5.5 °C even under strong solar radiation (~930 W/m²) and high relative humidity (~64%) in a hot and humid subtropical monsoon climate. This makes it an all climate PRC system.

Additionally, a UV resistant, acid resistant, anti-fouling, and thermally stable micro sandwiched structure film was developed [97]. This material offers high environmental stability, ease of fabrication, and a low cost of approximately $1.58/m². However, its radiative cooling performance remains constrained by humidity and wind-blown sand abrasion, while durability and shading from surrounding buildings pose additional challenges.

Existing DRC materials (e.g., PDMS and PET) rely on the 8–13 μm atmospheric transparency window to radiate heat into the cold outer space. However, water vapor exhibits strong absorption peaks in the mid infrared range, particularly at 6–8 μm and >14 μm, partially overlapping with the atmospheric window (8–13 μm). In hot and humid climates, high humidity leads to intense absorption of radiative cooling emissions by water vapor, significantly weakening PRC performance [98]. Studies indicate that DRC efficiency is positively correlated with solar radiation intensity but negatively correlated with wind speed and relative humidity. A field experiment conducted in Singapore also demonstrated that high solar radiation and high humidity during the day significantly reduced the performance of radiative coolers [99]. The absorption of the atmospheric window by water vapor poses a major challenge for the effective application of existing DRC technologies in humid climates.

To address this issue, future DRC materials could incorporate moisture resistant coatings to form composite structures. The use of hydrophobic nanocomposite materials, such as fluorinated Al₂O₃, could reduce water molecule adsorption while maintaining high emissivity. Research has shown that an Al₂O₃ coating achieves a temperature reduction of up to 6 °C in humid environments, outperforming PDMS [100].

Additionally, a multifunctional window has been proposed [101], integrating selective liquid absorption filters and solar cells, making it particularly suitable for commercial buildings in hot and humid climates. Simulations indicate that a 10 mm thick water/silver nanofluid absorption filter can effectively enhance the thermal mass of building windows, lower PV module operating temperatures, and improve key performance indicators.

PRC materials are required to operate under prolonged exposure to outdoor environments. During daytime cooling, these materials must withstand intense solar irradiation and frequent thermal expansion contraction cycles. Moreover, environmental factors such as dust and atmospheric aerosols can obstruct or scatter thermal radiation, while also potentially abrading the coating surface or inducing chemical corrosion (e.g., acid rain), which may degrade the functional layers [102]. To address these challenges, a TiO₂-based radiative cooling coating has been developed, exhibiting significant passive cooling performance under hot and humid conditions. The formulation incorporates PVDF and acrylic resins as binders, which enhance fouling resistance, environmental durability, pigment dispersion, and adhesion to various substrates. However, due to the high cost of PVDF (approximately USD 50 per kilogram), the economic feasibility of such coatings remains a concern and requires further improvement [103]. Overall, the long-term performance of PRC materials depends on the ability to maintain high surface cleanliness and resist environmental degradation.

In addition, effective thermal radiation requires PRC surfaces to face directly toward the sky. As a result, façade integrated PRC components can only be applied on unobstructed curtain walls, which restricts architectural flexibility. Applying PRC coatings or films on different substrates necessitates strong interfacial adhesion and weather resistance. Some emerging PRC coatings require high temperature curing or smooth substrates, which limits their compatibility with diverse building materials and complex geometries. Retrofitting existing buildings often involves additional structural reinforcement or HVAC integration, leading to high implementation costs. Recent market studies suggest that radiative cooling solutions are generally unsuitable for building retrofits, and require a comprehensive design approach tailored to the overall building environment [104].

Future research on DRC technologies should focus on quantifying the durability, maintenance costs, and carbon footprint of PRC materials in humid climates, conducting comprehensive life cycle assessments to evaluate long-term feasibility.

4.1.2. Double Skin Façade (DSF)

A DSF can function as an additional thermal insulation layer or thermal buffer zone, improving a building’s thermal performance. Existing DSF cavity ventilation modes include non-ventilated, naturally ventilated, mechanically ventilated, and hybrid ventilation systems, which integrate natural ventilation with mechanical HVAC systems. Proper ventilation design can reduce PV module temperatures, extending their lifespan to over 25 years [105]. Compared to natural ventilation, mechanical ventilation significantly enhances performance, with cavity width playing a crucial role [106].

In hot climates, integrating DSF with BIPV offers multiple benefits, including electricity generation, reduced off-site energy consumption, and improved indoor thermal comfort. Field measurements in Hong Kong’s hot climate demonstrated that a naturally ventilated thin film PV DSF maintains lower and more stable indoor temperatures compared to traditional curtain walls with internal shading devices [71].

A simulation study analyzed the impact of structure, orientation, air cavity depth, and PV coverage ratio on PV DSF performance. The results indicated that a south-facing orientation achieved optimal heat gain and power generation efficiency. Additionally, the PV coverage ratio was found to be inversely proportional to annual heat gain but had minimal impact on annual heat loss. Similarly, air cavity depth had little effect on annual energy performance [107].

Based on indoor comfort temperature levels in Australia, research investigated optimal ventilation modes and transparency levels, revealing that a naturally ventilated BIPV/T DSF with low visible light transmittance (VLT = 27%) PV glass provided superior indoor thermal comfort [108].

Some scholars have optimized air-cooled channels in DSFs. For instance, vertically installed fins in the PV wall air cooling channel enhanced heat collection efficiency and increased airflow velocity [109]. Additionally, adjusting the thickness or width of the fin cooled air channel further improved cooling efficiency [110].

However, some scholars have questioned the energy saving effectiveness of BIPV DSF systems. A study [111] proposed a control algorithm that adjusts DSF ventilation modes based on different climatic conditions. The building primarily relies on natural ventilation, activating mechanical cooling or heating only when natural ventilation fails to maintain the desired indoor temperature range. However, in a tropical savanna climate (Bangkok), this adaptive system did not show significant advantages over a fixed single mode ventilated BIPV T/DSF system. The high year-round temperatures and small indoor–outdoor temperature difference (<3 °C) in tropical climates significantly weaken natural ventilation driven convection, limiting its effectiveness.

Another study [112] verified that while ventilated air gaps in hot climates effectively reduce heat transfer, BIPV DSF systems generate insufficient electricity, and BIPV curtain walls have higher thermal transmittance. From an energy performance perspective, neither of these BIPV façade improvements could reduce cooling loads; instead, they increased overall building energy consumption, making them unsuitable for Mauritius’ climate.

A simulation study [113] was conducted on an open plan office building across all bioclimatic zones in Brazil to evaluate the impact of PV modules and fan assisted cavity ventilation on energy consumption. Results indicated that energy savings were lowest in hot regions.

To address these limitations, a study [114] proposed a novel exhaust ventilated photovoltaic façade system (EVPV HP) that integrates an air source heat pump to enhance outdoor air treatment and improve energy efficiency. The EVPV HP system demonstrated greater energy saving potential under high temperature and high solar radiation conditions.

4.1.3. Evaporative Cooling

The efficiency of evaporative cooling depends on the wet bulb temperature depression, which is the difference between the dry bulb and wet bulb temperatures. In hot and humid climates, where air humidity is near saturation (relative humidity often exceeds 60%), the evaporative driving force is extremely low. As a result, evaporative cooling performs exceptionally well in hot and dry climates but faces significant limitations in humid environments.

A study [115] developed an algorithm to control airflow velocity in the ventilation channels of an evaporative cooling façade system. Field experiments confirmed that this integrated control approach minimized façade surface temperatures while reducing performance discrepancies between arid and humid regions, achieving up to 21.8% annual cost savings in typical cities of the Arabian Gulf.

Nevertheless, high humidity increases the latent heat cost of dehumidification. One study [26] integrated a curtain wall with an evaporative cooler and a PVT system, demonstrating that while evaporative cooling reduced thermal energy demand in hot and humid climates, the additional energy required for dehumidification was not accounted for, potentially overestimating the actual energy savings.

An innovative passive cooling solution—the evaporative porous clay cooler—was proposed [116]. This system attaches water saturated porous clay to the back of PV panels, where water evaporation absorbs heat, thereby reducing PV temperatures. Experimental data showed that a 20 mm thick clay with 40% porosity could achieve a PV temperature reduction of 19.1 °C, significantly lowering electricity production costs and shortening the PP by 2.3 years. Further optimizations of this cooling system are planned, including [109]:

• Automatic water supply systems to maintain clay saturation, ensuring continuous evaporation;
• Optimized PV clay installation spacing to enhance natural ventilation, improving heat dissipation while preventing heat reabsorption by the building.

Hydrogel-based evaporative cooling, as introduced in [117], demonstrates strong potential in low-latitude climates, where high ambient temperatures and strong solar radiation accelerate water evaporation. The system achieved peak cooling capacities of 712 W/m² in Miami, 702 W/m² in Melbourne, and 693 W/m² in Singapore. However, increased daytime humidity can negatively impact evaporative performance, while higher nighttime humidity facilitates hydrogel rehydration. In arid zones, reliable water availability is essential to sustain long-term operational effectiveness.

Building integrated photovoltaic/thermal (BIPV/T) systems integrate PV modules into the building envelope while utilizing gas, liquid circulation media, or phase change materials (PCM) to recover and cascade excess heat from the PV back panel [118]. This technology not only actively regulates PV operating temperature through thermal energy recovery but also converts approximately 15–20% of the waste heat from conventional PV systems into usable thermal energy, significantly enhancing overall solar energy utilization efficiency [119].

A study [120] proposed a BIPV/T system combined with a water cooled wall, using air as the cooling medium to recover waste heat from PV modules for domestic hot water or heated air applications. Experimental results showed an average power generation efficiency of 12.6%, with the system supplying over 7 h of 35 °C hot water. This innovative design separates the water-cooling circuit from the PV modules, effectively preventing condensation-induced corrosion or pipe freezing in hot and humid climates, thus reducing maintenance costs. The system is particularly suitable for hot and arid regions with large diurnal temperature variations, though further assessments are required to evaluate the initial investment of the water-cooled wall heat exchanger and the long-term operational energy consumption, such as fan power consumption.

4.1.4. PCM

The integration of PCMs into building envelopes has reached technological maturity, offering enhanced thermal management solutions for energy efficient structures [121]. Leveraging their high latent heat capacity and near isothermal phase transition properties, PCMs effectively reduce heat transfer to indoor spaces while stabilizing interior temperatures [122].

Innovative PCM Integrated Systems:

• PV PCM Windows: Addressing limitations of conventional PCM windows (fixed phase transition, winter solar blockage) and PV windows (summer heat gain), ref. [123] proposed a modular multi-layer PV PCM window. This design achieves a SHGC of <0.30 and a U value of <2.50 W/(m²·K), delaying indoor temperature peaks by 10–30 min. Simultaneously, it generates more electricity than standard PV windows while maintaining illuminance levels compliant with national building codes;
• Ventilated PV CPCM Walls: [124] developed a ventilated wall system integrating composite PCMs (CPCMs) with air cavities. The ventilation layer mitigates PV module overheating (reducing operating temperatures by 4.9 °C), while CPCMs reduce indoor temperature peaks by about 2 °C compared with the common double hollow block walls, demonstrating adaptability to diverse climatic conditions.

The commonly used PCM can be classified into organic PCMs, Inorganic PCMs, eutectic PCMs, and composite PCMs. Material selection prioritizes PCMs with phase transition temperatures slightly exceeding local daily maximum temperatures. For instance, inorganic PCMs with melting points close to ambient temperature (such as sodium nitrite) reduces PV module temperatures by 8 °C in tropical regions, improving power conversion efficiency by 10% [125]. Ref. [126] proposed a hybrid system that combines thermoelectric generators (TEG) and microencapsulated phase change materials (mPCMs) to simultaneously utilize both solar light and heat. The study demonstrated that high-temperature environments are more conducive to generating a larger temperature difference, thereby enhancing the TEG power generation efficiency.

Table 3. A comparison of cooling technologies suitable for dry and humid climates.

Climate	Main Features	Applicable Cooling Technologies	Cooling Performance
Arid and hot climate	High temperature, low humidity, and strong solar radiation	Multilayer Structure DRC (Shading Assistance)	The cooler’s temperature is reduced to 10.4 °C lower than the ambient air, with a maximum cooling performance of 127 W/m2, and a net cooling power generated during the day of 14.3 W/m2.
		Fluorescent-based Colorful PRC	The performance of orange fluorescent PCRC is 2.7 °C lower than that of traditional white PRC. At night, the surface temperature of all PCRCs is 7–8 °C lower than the ambient temperature.
		Rotatable PRC	The maximum cooling energy is 14.45 kWh/m2 (in October).
		Evaporative Cooling (Control Algorithm)	The monthly average temperature on the south facing façade is reduced by 1–9 °C.
		Natural Ventilation DSF (Vertically Installed Heat Dissipation Fins)	The peak temperature and average temperature on the surface of the photovoltaic panels were reduced by 3.9 °C and 8.1 °C, respectively.
		Mechanical Ventilation for DSF	In the summer, the average photovoltaic temperature is 29.98 °C, which is 1.54 °C lower than that of the non-ventilated system.
Humid and hot climate	High temperature, high humidity, and strong solar radiation	Hydrophobic/Composite PRC materials	(with Al2O3 coating) The temperature of the photovoltaic module decreased from 63 °C to 58 °C, a significant reduction of 5 °C.
			(PDMS/PET Coating) During summer nights, PRC can reduce the temperature of photovoltaic panels by about 10 °C. After applying PDMS and PET coatings, the temperature is further reduced by approximately 1.35 °C and 1.15 °C, respectively.
			(With fluorosilane hydrophobic treatment) A temperature reduction of approximately 5.5 °C can still be achieved under hot and humid climatic conditions.
		PCM (LAF)	When using NF as a liquid absorption filter, the indoor window surface temperature is 25.25 °C.
		Naturally Ventilated DSF	The maximum indoor air temperature is 28.9 °C, which is 5 °C lower than that of a traditional façade with shading devices.
		BIPV/T Liquid Cooling and Recovery System (Water Cooled Wall)
		PCM (Mechanical Ventilation)	The delay in the peak of the interior surface temperature is 0.3–0.9 h, and the fluctuation of the indoor temperature is reduced by 1.1–2.4 °C.
		PCM (Humidity Adapted Inorganic/Composite PCM)	The instantaneous peak temperature of the photovoltaic module is reduced by 8 °C, which is equivalent to a decrease of approximately 12% in the temperature of the photovoltaic cells compared to the reference BIPV.
		Evaporative Cooling (Control Algorithm)	The monthly average temperature on the south facing façade is reduced by 1.5 °C.
		Dynamic PCM	The peak indoor temperature is reduced by 6.1–10.94 °C.

summarizes the climate adaptability of the aforementioned cooling technologies. Most cooling strategies are well suited for hot arid climates, whereas hot humid climates require dehumidification technologies to mitigate the adverse effects of moisture. Although technologies such as PRC, double skin façades (DSF), and evaporative cooling provide diverse cooling solutions for BIPV façades, they are often implemented independently, neglecting the integration with active building systems such as heating, ventilation, and air conditioning (HVAC) and building energy management systems (BEMS). This lack of coordination results in fragmented thermal load management, negatively impacting overall energy efficiency. The incorporation of energy recovery ventilation (ERV) systems, controlled ventilation rates, and high seasonal energy efficiency ratio (SEER) HVAC systems can optimize building energy performance [127]. Current research primarily focuses on laboratory testing and single technology optimization, while real world applications still face challenges related to system integration and control complexity.

4.2. Dimming Technologies

4.2.1. Color Technologies

In hot climates, the color selection of PV glass significantly influences a building’s thermal performance and energy efficiency. Research has shown that PV glass with varying levels of transparency has a minimal effect on the color quality of transmitted light, whereas different PV glass colors exhibit significant differences [128]. Based on the assumption that hue affects thermal perception, green and blue PV glass may create a cooler sensation for occupants. However, in regions with hot summers and mild winters, such as Guangzhou, low transparency PV glass considerably increases lighting energy consumption, leading to a rise in overall building energy demand. Among these, green PV glass with 20% transmittance has been identified as the least energy efficient PV glass type.

A comprehensive monitoring and data analysis of five differently colored BIPV modules under real operating conditions [129] has revealed the complex influence of color on module performance. The study found that darker colored modules (e.g., mahogany and forest green) exhibited higher efficiencies under standard test conditions. However, their performance degradation was more pronounced under real world conditions due to elevated operating temperatures. In contrast, lighter colored modules (e.g., white and patina green) demonstrated lower nominal efficiencies but experienced less temperature-induced performance loss.

Electrochromic (EC) glass, an emerging smart window technology, is actively being developed [130]. By controlling its optical properties via an electric field, EC glass can dynamically adjust its transmittance, optimizing both daylighting and thermal performance in buildings. For instance, a novel predictive control strategy has been proposed to optimize the operational state of EC glass [131]. EC windows using this strategy are suitable for most cities with high cooling energy demand. However, in regions with hot summers and mild winters, their energy saving potential is limited due to the overall high cooling season energy consumption.

Photovoltachromic (PVC) windows, which integrate electrochromic materials with dye sensitized solar cells, offer advantages over EC glass, which requires an external power source and complex control strategies. PVC windows are self-powered and can autonomously regulate their visible light transmittance in response to solar irradiance. By dynamically adjusting the SHGC, PVC windows reduce air conditioning energy consumption while maintaining uniform indoor illumination, thereby lowering the demand for artificial lighting. This makes them particularly suitable for high irradiance regions with strong cooling demand, especially for east and west facing façades [132].

A study [133] evaluated the visual comfort of photovoltaic façades in hot desert climates, including glare analysis and color comfort assessment. The material’s reflectance and transmittance range (10–90%) were identified as key parameters. Perovskite windows with 50–70% transmittance achieved an optimal balance between energy generation and glare control. In contrast, windows with 90% transmittance provided better color comfort but suffered from severe glare issues.

4.2.2. PVSD

Shading design is one of the most critical climate responsive strategies for hot regions. PVSD are particularly suited to hot climates due to their ability to optimize indoor thermal conditions. The “Xia style shading” design method, developed by Professor Xia Changshi—a Chinese architect who studied architecture in Germany and later taught at the School of Architecture at South China University of Technology—effectively integrates aesthetics and functionality. This method has been widely adopted in the Lingnan region of China.

A key aspect of shading design is determining the appropriate shading periods. According to the solar protection requirements of “Xia style shading”, the critical shading periods for the east, west, and south façades in Guangzhou are before 10:00 a.m. and after 4:00 p.m. from May to September, as well as at noon [134]. Notably, in low latitude regions within the tropics, direct sunlight from the south to the north occurs before 10:00 a.m. and after 4:00 p.m. between May and September. Fixed shading louvers alone cannot provide complete shading during these periods. Additionally, integrating PV façades with shading systems in urban environments presents multiple challenges, such as obstructions from surrounding buildings and self-shading effects. The design of PVSD must balance photovoltaic conversion efficiency, shading performance, and light transmittance.

Current PVSD research focuses on three key dimensions: morphological innovation, system integration optimization, and intelligent dynamic control, aiming to provide comprehensive shading solutions.

From a morphological perspective, simulation studies have explored the solar performance and efficiency of various foldable dynamic shading forms in Singapore [135]. Among these, the foldable square model consistently maintains high BIPV efficiency under all conditions. Hexagonal and octagonal central folding units, such as the triangular modules of the Al Bahar Towers, feature a centrifugal expansion mechanism that effectively blocks high angle solar radiation in low latitude regions. During the cooling season (April–October in Singapore), these designs can reduce solar heat gain through side windows by up to 30% while maintaining photovoltaic efficiency. For west facing façades, diagonally foldable square units with adjustable rotation angles (55°–76°) can dynamically block intense afternoon sunlight. Compared to static shading, dynamic adjustment can enhance photovoltaic power generation by 15–20%.

In India’s hot and humid climate, an innovative perforated fabric screen external shading device (ESD) was applied to fully glazed façades [136]. Simulation experiments demonstrated that this system reduced space cooling energy demand by 20% for a multi-story glass office building in Chennai. With dynamic adjustments, cooling energy savings could reach up to 24%. Similarly, simulation experiments conducted under university building conditions in Guangzhou, China, determined the optimal design parameters for PVSD applications [134]. Findings indicate that side shading at smaller angles yields higher energy generation benefits, while the key influencing factor for overhang shading is spacing. Under the same spacing conditions, overhang shading performs better in the horizontal direction than in the vertical direction.

For different building functions, researchers have proposed various integration strategies for PV façades and shading systems. Shading caused by upper layer PVSDs can lead to a reduction in photovoltaic electricity generation of up to 67%. A study conducted in Hong Kong [137] proposed three control strategies to mitigate this issue. When the PVSD was fixed at the annual optimal tilt angle of 65°, energy consumption was reduced by 25%. Monthly adjustment of the tilt angle further reduced energy consumption by 31.9%, while hourly dynamic adjustment achieved the highest reduction of 36.5%. A novel adaptive façade system, named SLICE (Solar Lightweight Intelligent Component for Envelopes), was proposed in [138]. This system autonomously adjusts the aperture of its shading components in response to increasing solar irradiance to maintain a consistent indoor illuminance level. When no occupants are detected, the shading elements fully deploy to maximize energy generation. However, a notable issue remains: the system experiences a sharp drop in battery voltage during high temperature periods in the afternoon, indicating that thermal management challenges must still be addressed. A study on office buildings in Ha’il, Saudi Arabia (hot desert climate), evaluated the energy performance and visual comfort of five PVSD configurations [139]. The best performing system was an unfilled egg crate PVSD, which achieved energy surplus at a conversion efficiency of 20% while ensuring good visual comfort. Additionally, a productive façade design tailored for residential spaces was proposed [140]. Simulation experiments integrated vertical farming with PV shading modules to improve indoor daylight and thermal comfort for residential buildings in Guangzhou, China. The system was capable of meeting 6–10% of the community’s electricity demand and 7.6–9.6% of its vegetable supply.

Bifacial photovoltaic (BiPVS) modules generate electricity from both the front and rear surfaces, with commercial products achieving efficiency levels exceeding 24% [141]. Compared to monofacial PV systems, BiPVS can increase power generation by 24.5% [142], and when installed vertically, they are less affected by dust and snow accumulation [143]. Studies have shown that BiPVS is particularly suitable for buildings with high cooling loads on specific façades and sufficient solar resources. Due to the stronger solar radiation on west-facing façades, west-oriented BiPVS installations offer greater energy savings. However, BiPVS can reduce indoor illuminance levels. Additionally, the shading structure’s simultaneous blockage of thermal radiation and convection results in no significant impact on the window glass surface temperature.

Two improvements have been proposed for vertically installed BiPVS: (1) introducing a gap between the PV module and the window to enhance natural convection cooling and (2) increasing the height of the BIPV system. In hot summer and mild winter climates, BiPVS achieves significant power generation gains, with a PP of 5.31 years, demonstrating high feasibility in hot climates. When applying PVSDs, special attention must be given to their impact on lighting energy consumption, as excessive shading may increase artificial lighting demand, offsetting cooling energy savings. In Guangzhou, low-positioned monofacial panels have been identified as the optimal PVSD type [144].

It is also crucial to consider the effects of façade material color, surface properties, and installation distance on the rear surface reflectance distribution. Variations in these factors can lead to current mismatch and hot spot risks. To ensure uniform rear surface reflectance, high reflectivity materials (such as white surfaces) should be prioritized, and installation distances should be maximized (>10 cm) to enhance reflected light mixing [145].

5. Parametric Design and Integration of Intelligent Systems

5.1. Key Design Parameters

A study [146] investigated five key design parameters of customized BIPV modules—geometric transparency degree (GTD), cell arrangement, cell cutting technology, glass type, and low emissivity (low E) coating type and position—and their impact on the “photo thermal electrical” performance of BIPV. Based on different climate regions and window to wall ratio (WWR) requirements, the study recommended various BIPV configurations. For instance, in hot and humid climates, insulated BIPV with a GTD below 46.0% can serve as an alternative to conventional double silver low E curtain walls.

The layout, orientation, tilt angle, size, shape, and overall design of PV systems should be optimized to maximize solar radiation utilization throughout the year [147]. The tilt angle of PV modules is the angle between their surface and the horizontal ground plane. Due to the Earth’s revolution around the Sun, the optimal tilt angle varies as the Sun’s position shifts between the Tropics of Cancer and Capricorn over the course of a year. Existing studies commonly use latitude-based empirical rules (e.g., tilt angle = latitude ± 15°) for PV system design.

A study in Saudi Arabia examined six locations to determine the optimal tilt and azimuth angles [148]. Results indicated that the optimal tilt angle is slightly higher than the local latitude, while the optimal azimuth angle, due to the asymmetrical distribution of daily solar radiation, ranges from 20° to 53° west of due south. Similarly, research in Egypt identified the best tilt angle for solar radiation collection systems [149]. With a fixed tilt, the recommended angle is approximately 28°–29°, slightly below the local latitude (29°). However, seasonally adjusted tilts—latitude +15° (≈45°) in winter and latitude 15° (≈15°) in summer—can balance efficiency and operational costs.

Tilt angle and panel spacing are often dynamically adjusted in combination. A study on a novel PV louver system found that changes in panel spacing had a greater impact on system performance than tilt angle variations [150]. A simulation-based study on PV integrated shading strategies in Colombo, Sri Lanka, suggested that a PV installation with a 30° tilt angle and a spacing to length ratio of 4 offers the best economic feasibility and significantly outperforms traditional vertical installations [151].

A parametric design approach [152] was used to balance power generation efficiency, shading effectiveness, and architectural aesthetics. The study found that for south facing façades in Hong Kong, an optimal PV shading tilt angle of 25°–30° with a spacing to length ratio (D/L) greater than 8 minimizes inter panel shading. In addition to optimizing power generation, BIPV design must also consider drainage and ventilation. Excessively large tilt angles can hinder natural ventilation, leading to higher module temperatures.

A comparative study on PV performance in Malaysia’s tropical climate revealed that east facing and west facing PV façades perform almost identically, with only minor differences due to solar radiation intensity, spectral effects, module temperature, and orientation-based heat gain [153]. Additionally, a novel multi-faceted PV curtain wall system was introduced, and simulations determined the optimal upper surface opening angles for different orientations in low latitude regions [154].

A study conducted in El Sharouk, the new city of Egypt, found that dust accumulation is a major factor affecting PV module performance in hot desert climates. Experimental measurements showed that without cleaning, both monocrystalline and polycrystalline PV modules experienced an average decline of up to 30% in photovoltaic conversion efficiency after 30 days of natural dust deposition. However, cleaning effectively restored the modules’ efficiency to their original levels [155]. The study further analyzed the coupled effects of different installation tilt angles on dust accumulation and cleaning efficiency. Results indicated that under clean conditions, PV modules with a 30° tilt angle achieved the highest output performance. Additionally, when the tilt angle was within the range of 15° to 30°, the system could maintain high power generation efficiency while mitigating dust accumulation effects, reducing cleaning frequency, and balancing system performance with maintenance costs.

The number of layers in a PV curtain wall significantly influences a building’s thermal performance; however, research in this area remains limited. A study conducted on a residential building in Iran assessed the effects of multi-layered windows, PV integrated walls, and green roofs on buildings’ thermal performance [156]. The findings revealed that the combination of triple glazed windows, phase change material (PCM) walls, and a green roof was more energy efficient than the combination of a double skin façade (DSF), PCM walls, and a green roof. In terms of reducing cooling loads, the triple glazed curtain wall outperformed the double skin façade.

Building curtain walls serve as the primary interface for architectural aesthetics; however, research on the integration of PV modules into curtain walls remains relatively limited. A study conducted in Singapore explored the design of PV integrated curtain wall systems and proposed a novel method for manufacturing tile-like colored PV modules. The study employed the Honeybee algorithm to calculate the shading area of the curtain wall, assess solar potential, and utilize a pixelated strategy to create dynamic patterns on the façade based on potential mapping [157].

Additionally, another study investigated the feasibility of building integrated photovoltaics (BIPV) in hot and humid climates, analyzing the optimal combination of PV shading components with different cell transparency levels [158]. From an urban microclimate perspective, research highlighted that the canyon height to width ratio (h/w) is a key factor influencing PV power generation. In open urban canyons (low h/w), increasing the BIPV window coverage effectively enhances energy generation while mitigating nighttime urban heat island effects. This suggests that low density, open block layouts are more suitable for deploying BIPV windows, as they reduce mutual shading between buildings [159].

PV power generation systems face multiple constraints in building integration due to their relatively low energy conversion density and strong dependence on solar radiation access. Factors such as building orientation, façade design, shading strategies, and obstructions from the surrounding environment significantly impact the efficiency and practical value of PV modules. For instance, a study [160] assessed the impact of different building types and structural characteristics on the available façade area for PV deployment in Saudi Arabia’s hot desert climate. The findings revealed that conventional BIPV products struggle to meet the diverse façade design requirements in the Middle East, highlighting the need for customized solutions. Similarly, another study [161] applied grey relational analysis to examine the effects of installation orientation, solar inclination angle, seasonal variations, geographic location, and shading on the carbon reduction potential of PV curtain walls. Among these factors, installation orientation was identified as the most critical determinant.

The influence of Window to Wall Ratio (WWR) on energy consumption is particularly significant in BIPV integrated buildings [132]. A sensitivity analysis of building envelope design parameters identified WWR and ventilation (V) as the two most influential design factors in hot climates, using Hong Kong as a case study [162]. A study on a university campus in Guangzhou, China, found that the WWR of south facing walls is among the most critical parameters affecting the building’s annual net energy consumption [163]. Another study explored the optimal combination of façade transparency and WWR for school buildings in tropical regions. The findings suggested that a BIPV system with low transparency photovoltaic materials achieves optimal visual health, comfort, and energy performance when the WWR is 25% and PV cell coverage is 30%. Conversely, for high transparency TPV materials, the ideal configuration is a WWR of 31.25% with a PV coverage of 50% [164]. However, a study on passive design strategies for Malaysian school buildings recommended reducing the WWR of operable windows by 30% [165].

A CdTe-based double skin ventilated façade was proposed [166], which allows mode switching to adapt to different climate conditions. Excessively high PV coverage increases lighting energy consumption, while increasing the depth of the ventilated cavity reduces cooling loads. For Haikou, China, the optimal design parameters were found to be a 70% WWR and a 15 cm cavity depth.

The performance of BIPV façades is significantly affected by orientation (as

Table 4. Optimal façades for photovoltaic buildings in different hot regions.

Climate Type (Köppen Classification)	Location	Latitude and Longitude (Approximate)	Optimal Orientation and Findings
Tropical desert climate (BWh)	Sharjah (United Arab Emirates)	25.3° N, 55.5° E	45° south of east: The vertical surface has the highest radiation conversion factor [109].
	Dubai (United Arab Emirates)	25.2° N, 55.3° E	South: Highest annual yield; West: Afternoon power generation peak matches the electricity demand (12:00 18:00) [74].
	Upington (South Africa)	28.4° S, 21.2° E	East–West: Power generation is 45–48% higher than north; due to arid and less cloudy conditions, annual power generation is 10% higher than in Nelspruit [169].
Tropical rainforest climate (Af)	Bandung (Indonesia)	6.9° S, 107.6° E	South: Best daylight performance throughout the year, with optimal integrated energy production and indoor lighting, despite the highest annual power generation being in the north direction [168].
	João Pessoa (Brazil)	7.1° S, 34.8° W	West and East: Annual power generation is 59% and 28% higher than north, respectively, challenging the traditional notion that north facing is optimal in regions south of the equator [167].
Subtropical monsoon climate (Cwa)	Guangzhou (China)	23.1° N, 113.3° E	West: Highest annual power generation, followed by south and east [10].
	Hong Kong (China)	22.3° N, 114.2° E	South: Optimal for winter and overall annual performance; East and West: Highest radiation in summer; North façade: Potential for diffuse power generation [27].

). While conventional studies suggest that north-facing façades are optimal in regions south of the equator, recent research has yielded contrasting results [167,168]. The optimal orientation for BIPV systems is highly region specific, as it is influenced by complex climatic factors.

High-density urban areas exhibit unique morphological characteristics and complex building shading relationships. Key parameters influencing solar energy potential include building footprint, plot ratio, building height, and building perimeter shape factor [170].

Existing parametric design methods primarily focus on building geometry and PV module placement, often lacking real time environmental feedback and intelligent optimization. Future research could integrate multi-objective evolutionary algorithms (MOEA) or reinforcement learning (RL) to develop adaptive optimization strategies for BIPV curtain walls in hot climates. This approach could enhance dynamic shading, heat dissipation, and power generation performance, ultimately improving the overall energy efficiency of BIPV systems.

5.2. Intelligent Control and Multi Objective Optimization

Traditional building envelopes are unable to adapt to dynamic environmental changes, leading to low daylighting efficiency and significant heat transfer issues. In contrast, responsive façade systems, through the collaboration of sensors, actuators, and control systems, can significantly enhance energy efficiency.

Multi-objective algorithms are widely applied in optimizing complex goals in building design. These algorithms can improve the accuracy of photovoltaic generation interval prediction, thereby enhancing the adaptability of power systems to dynamic environments and complex data [171]. This approach provides a compromise solution for residential buildings [172], balancing electricity pricing and temperature comfort. As shown in

Table 5. Application of multi-objective algorithms in the design of photovoltaic façades in hot climates.

System	Variables	Objectives	Optimal Parameters	Location/Climate
PVSD	Shading angle, length, and quantity.	Electricity generation; Indoor daylight quality; Radiant heating; Cooling load.	Using twice the number of shading panels, but with half the length. Increasing the photovoltaic area by 2.5 times only results in a system value increase of less than 25%.	Singapore/ Tropical rainforest climate (Af) [173]
	The installation location and width of PVSDs.	Distributed solar power generation; Effective shading duration; Area of PVSDs.	Horizontally installed at 0.7 m; Tilted installed at 0.9 m; Real-time rotating installed at 0.7 m.	Hong Kong/ Humid subtropical climate (Cwa) [174]
	Shading type; Photovoltaic location; Tilt angle; Distance from the blind to the window; Window height; Window width; Distance from the occupant to the window; Orientation.	Percentage improvement in the annual economic cost of the building; Percentage improvement in the daylight glare index.	The optimal installation orientation is south facing.	Bandar Abbas, Iran/Hot desert climate (BWh) [175]
Dynamic and static PVSD	The quantity and length of shading devices; Optimal angles at multiple dynamic frequencies.	Electricity generation; Solar heat gain; Daylighting conditions.	A shading device that is 0.5 m in length, with a total area equal to the window area, is the optimal universal design; The optimal static angle is 65°.	Singapore/ Tropical rainforest climate (Af) [176]
BiPVS	Number of photovoltaic modules; Module width; Module height; Distance from the module edge to the wall; Angle between the front surface of the module and the wall; Photovoltaic cell coverage rate; Window glass transmittance.	Useful indoor solar irradiance; Air conditioning energy consumption; PP.	The number of photovoltaic modules is 17; Module width is 1.0 m; Module height is 3.0 m; The angle between the front surface of the module and the wall is 115 degrees; The photovoltaic cell coverage rate is 98%; Window glass transmissivity is 0.89.	Shenzhen, China/ Subtropical monsoon climate (Cwa) [177]
BIPV envelope	Tilt angle; PV product type; WWR; PV placement.	Life Cycle Energy (LCE), Life Cycle Cost (LCC)	The tilt angle is 35°.	[178]
Urban block	Building type; Number of floors; Location of open space.	South facing first floor solar exposure duration; Total building energy consumption; Monthly load matching index.	A layout with lower heights to the south and higher heights to the north; Simple building types; Open space located at the southwest corner.	Hot summer and cold winter climate zone [179]

, in hot climate environments, numerous studies focus on optimizing parameters of photovoltaic façade components, particularly PVSD.

Research suggests that operational strategies can sometimes contribute more to energy savings than design factors [180]. One such strategy is demand response (DR), which optimizes the flexibility of electrical and thermal loads (heating and cooling) by leveraging the thermal inertia of building structures. DR allows temporary adjustments to indoor climate control without compromising thermal comfort. A study on BIPV optimization in Singapore demonstrated that DR can reduce the marginal cost of PV systems in hot and humid climates, leading to an increase in the optimal PV installation area [181]. This highlights the significant impact of DR on economic feasibility, environmental assessment, and system design.

Artificial intelligence (AI) has demonstrated significant potential in optimizing BIPV system performance, particularly in power output prediction, fault diagnosis, and long-term energy planning.

A study by [182] employed a hybrid deep learning model (LSTM DF FF) to predict BIPV system output power. Compared to traditional physical and statistical models, this AI-based approach improved prediction accuracy, even under high radiation conditions during summer. Such AI-driven technologies lay the foundation for intelligent operation and grid coordination of PV systems in hot climates.

Similarly, ref. [183] developed a solar radiation prediction model (BDAAI SIP) that integrates big data analytics and AI. By utilizing weather forecast data for long-term analysis, this model outperformed conventional prediction methods in terms of accuracy. BDAAI SIP enables reliable long-term solar radiation forecasting, which is crucial for solar power plant planning, operational management, and maintenance scheduling.

Beyond performance optimization, early fault detection and maintenance are critical for protecting capital investments in large-scale PV systems. AI has shown great promise in PV fault diagnosis, where [184] introduced a method combining deep transfer learning and airborne infrared thermal imaging to detect thermal anomalies in PV panels effectively. Additionally, ref. [185] experimentally validated a solar air conditioning system integrating PV cells and thermoelectric cooling technology. AI-based modeling and optimization significantly reduced building energy consumption, allowing the system to operate efficiently at night using battery storage. The study highlighted the high prediction accuracy of AI in solar energy applications, reinforcing its potential for future PV-integrated technologies.

Concentrated Photovoltaic (CPV) technology enhances photovoltaic conversion efficiency by focusing sunlight onto efficient multi junction solar cells using optical lenses or mirrors. This approach significantly boosts power output per unit area, achieving conversion efficiencies exceeding 30% [186].

CPV systems demonstrate greater advantages in hot climates [187]. The Center for Sustainable Technologies at Ulster University has developed an innovative Concentrating Photovoltaic/Thermal (CPV/T) glazing system. In low latitude regions, where solar altitude remains high throughout the year, the Total Internal Reflection (TIR) effect of concentrating lenses enhances solar flux on PV cells, making CPV particularly suitable for regions with high direct solar radiation, such as arid desert climates.

However, CPV systems require high-precision solar tracking to maintain optical efficiency. Most CPV installations depend on dual axis tracking mechanisms to stabilize solar concentration, increasing system complexity and maintenance costs [188].

Despite the challenges of high complexity and cost, dynamic intelligent PV systems remain a promising trend for future building-integrated façades. Integrating AI-driven control, the Internet of Things (IoT), and Digital Twin technologies will enable real time coordination between PV façade systems and Building Energy Management Systems (BEMS), significantly enhancing the dynamic balance between PV power generation and building energy consumption.

6. Limitations of the Current State and Future Directions

6.1. Limitations of the Current State

6.1.1. Limitations of Climate Zoning in BIPV Design

With the rapid development of urbanization, future urban construction and architectural design are moving towards a refined stage. However, traditional Köppen climate classification, based on annual temperature and precipitation, does not capture urban microclimate variations such as

• Urban Heat Island (UHI) intensity;
• Street canyon ventilation conditions;
• Local environmental parameters such as sandstorm frequency, UV radiation, and air pollution.

6.1.2. Overlooking Long-Term Stability in BIPV Materials

Current BIPV research predominantly emphasizes initial efficiency while overlooking long-term stability. The effects of humid and hot conditions (temperature 40 ± 2 °C, RH 85 ± 5%) and arid and hot conditions (daytime 45 °C, nighttime 15 °C) on material performance are often dynamically coupled. Current research is largely based on simulations or controlled laboratory experiments, with limited use of real-world performance monitoring. While accelerated aging tests have provided insights into the impacts of temperature, radiation, and humidity on PV modules, there remains a significant gap in field-based data and long-term performance evaluation, focusing primarily on the impacts of temperature, irradiance, and humidity on PV modules and their mitigation strategies. In reality, the relationship between climate change and the built environment is highly complex and intertwined. The dynamic, multifaceted interactions of complex climatic factors, such as diurnal temperature variations and windblown sand abrasion, are often neglected in existing research, resulting in significant biases in the assessment of material durability.

6.1.3. Cooling Technology Limitations in Hot Humid Climates

Cooling technologies such as PRC, evaporative cooling, and phase change materials often face limitations in practical applications, including the coupled effects of humidity and heat, high maintenance costs, and weak integration with other building functions. Moreover, existing research predominantly relies on simulation software for comparative analysis, lacking empirical data. Although DSF mixed ventilation and BIPV/T systems can enhance overall energy efficiency, their complex control mechanisms and high initial investment remain significant challenges. Additionally, the latent heat energy required for dehumidification in evaporative cooling is often underestimated in high humidity environments.

6.1.4. PV Grid Integration and Curtailment Issues [189]

The near zero marginal cost of PV electricity grants it dispatch priority in power systems [190]. However, as the penetration of PV increases, curtailment—i.e., forced reduction in PV output—has become a major concern. This issue is driven by the following key factors:

• Intermittency and Variability: PV generation often misaligns with building load profiles. In hot climates, although cooling loads are high, the peak demand typically occurs in the late afternoon, whereas PV output peaks at midday. To prevent frequency instability caused by midday overgeneration, grid operators may curtail PV output. This problem is exacerbated by the high variability of solar irradiance in hot climates, as well as by seasonal fluctuations, with curtailment rates peaking in spring and autumn.
• Geographic Mismatch: There is often a spatial disconnect between areas suitable for PV generation (sunny, dry regions) and areas with high electricity demand (urban centers). Many large-scale PV plants are located in suburban or remote regions, while electricity consumption is concentrated in city centers. In addition, existing distribution infrastructure may be outdated or not designed for high levels of distributed PV, and limited transmission capacity between these areas further contributes to the geographic mismatch.

Curtailment threatens the economic viability of PV projects and poses risks to the broader development of the PV industry. Several potential mitigation strategies have been proposed:

• Deployment of Distributed PV Systems: Distributed generation enables more flexible control by grid operators and allows for local balancing of generation and demand, thereby reducing curtailment. System level optimization can further minimize PV curtailment [191].
• Adaptive Shading and Demand Response Strategies: Adjusting load profiles through demand side measures can help better align building energy consumption with PV generation. Integrating energy demand–generation synchronization during the design phase can enhance the initial match between supply and demand.
• Building Integrated Energy Storage: On-site storage can capture surplus midday generation. However, the trade-off between avoided curtailment and the capital cost of battery storage must be considered. Coordinated electric vehicle (EV) charging strategies [192] and dynamic EV tariff design [193] can also help absorb excess PV output, reducing the need for costly stationary storage systems.
• AI-Based Energy Management: Machine learning models can forecast short-term PV output and cooling demand profiles. This enables predictive control strategies, such as pre-conditioning indoor temperatures and dynamically adjusting charge/discharge behavior of energy storage systems. Weather informed, feedforward control can thus improve the real-time matching of PV supply with building demand.

6.2. Future Directions

Despite significant advancements in materials, cooling technologies, and architectural parameters, current BIPV façade research remains fragmented. The lack of an integrated design framework prevents the efficient adaptation of BIPV to varying climate conditions and diverse building typologies.

To address these challenges, future research should establish a multi-dimensional, climate responsive BIPV design framework, integrating the following:

• Multi-climate parameter analysis (temperature, humidity, dust levels, UV exposure, wind speed, seasonal variations);
• Dynamic energy management strategies (real time PV efficiency optimization, adaptive shading, hybrid cooling);
• Economic and durability based on life cycle assessment (quantifying long-term performance and financial feasibility).

Based on the review of this study, the core components of the framework primarily consist of the following parts:

• Climate Adaptive Design (Materia, Technology and Architecture Integration)

• Establish climate specific criteria for material selection. For hot dry climates, prioritize CdTe/CIGS thin film modules with high temperature resistant encapsulation. In hot humid zones, recommend CIGS modules combined with POE encapsulation. Accelerate the development of moisture resistant PSC and dust-repellent surface technologies.
• Define climate adaptive performance indicators, such as resistance to hygrothermal cycling (>1000 cycles) and annual thermal attenuation rate (ΔT < 5 °C/year).
• The selection of cooling technologies for BIPV systems must account for the distinct characteristics of arid and humid heat conditions. As illustrated in Figure 2, a quantitative analysis based on climatic parameters—such as temperature, humidity, and solar radiation intensity—should inform the targeted selection of passive cooling techniques (e.g., phase change materials, ventilated structures) or optimized combinations with active cooling systems. Furthermore, it is recommended to dynamically integrate weather forecast data into the intelligent control strategies of BIPV systems.

2.

AI and IoT Driven Dynamic Control

• Apply machine learning algorithms for real-time energy optimization. This includes dynamic adjustment of PV tilt angles, activation of cooling systems, and solar shading based on current weather conditions. Develop smart façades capable of responding to climate sensor data and predictive weather inputs to adapt shading, ventilation, and inclination.
• Deploy IoT-enabled intelligent façades for continuous environmental monitoring and automated system adjustment, enhancing responsiveness and energy efficiency.

3.

Life Cycle-Based Economic and Performance Optimization

Although the calculation of the PP in various hot climate regions follows the same fundamental economic principle—namely, the initial investment cost divided by the annual net benefit—it often requires adjustments in practice. These adjustments arise from regional differences in climate characteristics, material durability, operation, and maintenance strategies, and building typologies. The PP is generally calculated using the following basic formula:

$$PP={\displaystyle \frac{I_0}{ANB}}=I_0/(R-OM+ThB)$$

(1)

In which,

$I_0$—Initial Investment (USD/kWp), including materials, design, construction, system integration, installation, and commissioning;

$ANB$—Annual Net Savings (USD/kWp);

$R$—Annual Electricity Revenue (USD/kWp);

$OM$—Operation and Maintenance (O&M) Costs (USD/kWp);

$ThB$—Thermal Benefit (USD/kWp).

While photovoltaic efficiency and material degradation rates form the foundation for evaluating BIPV systems, accurate calculation of the pp must also incorporate region-specific socioeconomic and climatic factors. The initial investment cost is significantly influenced by local labor expenses, policy incentives, and construction standards. For instance, regions with advanced prefabrication technologies or governmental subsidies for green building initiatives may benefit from reduced capital expenditures.

On the revenue side, the annual energy savings from BIPV systems vary depending on local electricity pricing schemes. For example, Dubai adopts a tiered electricity tariff structure, with peak rates reaching approximately 0.10 USD/kWh, whereas the post-tax electricity price in Singapore averages around 0.31 USD/kWh. Higher electricity rates can significantly shorten the PP of BIPV systems by increasing annual savings.

Solar irradiance represents another critical regional variable. While low-latitude regions generally possess higher solar radiation potential, high humidity and frequent cloud cover in tropical climates can substantially reduce photovoltaic output. In comparison to arid desert regions with stable and high-intensity solar radiation, annual energy generation in tropical rainforest areas may be reduced by 10–30%. Therefore, appropriate derating must be applied during the calculation process.

In addition, energy savings and operational costs associated with thermal management technologies and building operation strategies should not be overlooked—particularly under hot and arid climatic conditions, where dust accumulation can lead to higher cleaning and maintenance expenses. Conversely, in humidity regions, greater attention must be paid to material degradation and the integrity of electrical insulation. However, these factors are often underrepresented in existing studies and are rarely incorporated into PP calculations.

Based on the above analysis, this study estimates the PP under the climatic conditions of Singapore and Dubai using three representative configurations for hot climate scenarios: (1) baseline CdTe BIPV; (2) CdTe with PRC; and (3) CdTe combined with a naturally ventilated DSF. The parameter settings for each configuration are summarized in

Table 6. PV system PP calculation parameter settings.

Project	Singapore	Dubai
$H$ (kWh/m2·year)	1 600	2 100
$PR$	0.75	0.80
$P$ (USD/kWh)	0.31	0.10
$OM$ (USD/kWp·year)	15	25 (Higher cleaning frequency)
$Kf$	0.75	0.75

. Reasonable estimates of initial investment and operational costs were adopted within a plausible range [194]; therefore, the primary variable affecting the results is the variation in electricity generation revenue:

$$R=H\ast PR\ast (1+∆\mathrm{E})\ast 1kWp\ast P\ast Kf$$

(2)

In which:

$H$—Annual Average Solar Irradiance(kWh/m²·year);

$PR$—System Performance Ratio;

$∆\mathrm{E}$—Electricity Generation Gain;

$P$—Electricity Price (USD/kWh);

$Kf$—Façade Reduction Factor.

As shown in

Table 7. Three PP of typical PV façade system configurations under hot climate conditions.

Configurations	${\mathit{I}}_0$ (USD/kWp)	$∆\mathbf{E}$	Region	$\mathit{R}$ (USD/kWp)	$\mathit{T}\mathit{h}\mathit{B}$ (USD/kWp)	PP (year)
Baseline CdTe BIPV	data	0	Singapore	279	0	5.9
			Dubai	126	0	15.3
CdTe with PRC	1750	5%	Singapore	293	0	6.3
			Dubai	132.3	0	16.3
CdTe combined with a naturally ventilated DSF	1850	4%	Singapore	290	5	6.6
			Dubai	131	5	16.7

, the PP of PV façade systems in Singapore ranges between 5.9 and 6.6 years, largely supported by high post-tax electricity tariffs. In contrast, the same configurations in Dubai require approximately 15.3 to 16.7 years for capital recovery due to low electricity prices, despite superior solar irradiance. While the integration of thermal control systems may extend the PP due to higher initial investments, these hybrid configurations can offer additional long-term benefits, such as extended module lifespan, improved indoor comfort, and reduced cooling demand, which are not fully captured in standard payback models.

To better assess economic viability under different conditions, region-specific benchmarks for lifecycle efficiency, material durability, and return on investment (ROI) should be developed based on Köppen climate zones. A comprehensive Life Cycle Cost Benefit Analysis (LCCBA) is essential, taking into account long-term factors including material degradation, maintenance frequency, and energy-saving performance. This approach enables the identification of climate-specific, cost-effective design strategies and technologies.

Moreover, streamlining construction processes, reducing installation time [53], and aligning deployment with regional building codes and renewable energy incentives [195,196] can significantly lower upfront costs and enhance financial viability. Context-specific policy supports—such as feed-in tariffs, carbon credits, or green building subsidies—also play a critical role in accelerating ROI and fostering market adoption.

Future studies should incorporate real-world monitoring data to validate model assumptions, and quantify how factors such as dust accumulation, façade orientation, and system degradation affect actual performance and PP. These insights are crucial for refining climate-adapted economic benchmarks and guiding the development of resilient BIPV solutions.

4.

Enhancing Industry Collaboration and Standardization

• Digital Collaborative Platforms

Address communication gaps among architects, engineers, policymakers, and manufacturers through digital collaboration platforms. Improve design efficiency and minimize costs associated with information discontinuities [197]. Early stage BIPV design should involve clearly defined roles for stakeholders. Regional BIPV alliances and design workshops—such as the public–private model of Singapore’s SolarNova program [198]—can foster integrated decision making. Establish shared databases including thermal properties of materials, regional climate profiles, and photovoltaic performance.

Promote early-stage collaboration between architects and PV engineers during the conceptual design phase to reduce design errors due to fragmented workflows.

Implement BIM-based co-design platforms [199], integrating tools such as Autodesk Forge and PVsyst to evaluate PV performance and building thermal load interactions during the planning stage. Leverage Product Lifecycle Management (PLM) systems to coordinate façade product development, testing, installation, and maintenance.

• Standardized Evaluation Systems

Encourage national or regional energy authorities to develop standardized BIPV performance assessment frameworks based on climate zones. This includes classification schemes for climate adaptability.

Align such standards with existing green building certifications (e.g., LEED, BREEAM, and China’s Three Star Rating). For humid climates, assessment should include parameters such as “module surface temperature attenuation coefficient” and “hygrothermal cycling resistance,” fostering a multi-dimensional pathway for standard development.

By integrating real-time climate data, AI-based optimization, and lifecycle cost analysis, this climate adaptive BIPV façade framework could overcome current technical bottlenecks and enable high efficiency, stable, and scalable BIPV applications in hot climates.

7. Conclusions

This study provides a comprehensive review of the design, materials, and performance of BIPV façades in hot climates. The existing literature extensively explores material selection, technological integration, and design optimization for BIPV façades under high temperature conditions. Practical implementation necessitates balancing climatic factors (ambient temperature, solar irradiance, humidity) with material durability, energy efficiency, cost, photovoltaic orientation/tilt, building orientation, and WWR to maximize power output and system efficiency.

Here are some key findings of this study:

Material Selection: BIPV materials must align with efficiency, temperature sensitivity, and climatic adaptability. CdTe or CIGS thin film technologies paired with heat resistant encapsulation are suitable for arid regions, while CIGS POE combinations are preferred in humid climates for enhanced hydrolytic stability. Current semiconductor research lacks long-term stability assessments under dynamic climatic variations, necessitating performance enhancements tailored to architectural weathering requirements. A climate performance database should be established to quantify efficiency degradation rates, thermal stress thresholds, and energy consumption correlations across climate zones, providing baseline data for regionalized design and material selection, particularly for hot regions (e.g., Middle East/Southeast Asia).

Cooling and Daylighting Strategies: BIPV façade cooling technologies (PRC, DSF, PCM, evaporative cooling) and dynamic shading systems (electrochromic glazing, PVSD) require climate specific optimization. While hybrid active passive cooling systems are increasingly studied for indoor environmental optimization, few address dual energy cost efficiency or fully account for hidden operational expenses. Integrated PV façade technologies must prioritize economic feasibility.

Integration of Intelligent Systems: Extensive studies on PV module parameters and architectural design variables have established critical reference frameworks for BIPV applications in hot climates. Concurrently, PV façades are evolving toward dynamic adaptive systems, with multi-objective optimization algorithms emerging as a key research focus. These algorithms primarily target the optimization of design parameters, particularly for PVSD, to balance energy generation, thermal comfort, and daylighting performance.

Research Gaps: Existing studies extensively address PV component parameters and architectural design variables, offering valuable references for hot climate BIPV design. However, current research predominantly focuses on single component performance or localized cooling optimizations, neglecting holistic system evaluation, dynamic feedback mechanisms, and lifecycle economic assessments. Future studies must address performance degradation under evolving climatic conditions and parameter drift in long-term operation.

Research indicates that while current BIPV façades show significant potential in enhancing energy self-sufficiency and aesthetic performance, the existing literature predominantly focuses on optimizing individual component performance or localized cooling technologies. There is a lack of comprehensive multi-dimensional evaluation of the entire system, and insufficient attention is given to dynamic feedback mechanisms, particularly economic assessments and adaptive design. Furthermore, under the context of future climate change, issues related to the drift of design parameters and long-term performance degradation require further exploration.

In summary, this study systematically reviews the current state of research and technological challenges related to BIPV façades in hot climates. It provides a complete solution chain for NZEB in tropical regions, ranging from material selection to intelligent optimization. Additionally, it outlines future research directions, including multi-scale, multi-physics coupled simulations, intelligent optimization control, and life cycle environmental and economic assessments. Future work should focus on long-term field monitoring and cross regional comparative studies to refine dynamic feedback mechanisms and integrated design solutions, thereby promoting the widespread application of BIPV façades in building energy efficiency and low carbon transitions.