Search Results (172)

The development of integrated renewable energy and high-density thermal energy storage systems has been fueled by the need for environmentally friendly heating and cooling in buildings. In this paper, MiniStor, a hybrid thermochemical and phase-change material storage system, is presented. It is equipped with a heat pump, advanced electronics-enabled control, photovoltaic–thermal panels, and flat-plate solar collectors. To optimize energy flows, regulate charging and discharging cycles, and maintain operational stability under fluctuating solar irradiance and building loads, the system utilizes state-of-the-art power electronics, variable-frequency drives and modular multi-level converters. The hybrid storage is safely, reliably, and efficiently integrated with building HVAC requirements owing to a multi-layer control architecture that is implemented via Internet of Things and SCADA platforms that allow for real-time monitoring, predictive operation, and fault detection. Data from the MiniStor prototype demonstrate effective thermal–electrical coordination, controlled energy consumption, and high responsiveness to dynamic environmental and demand conditions. The findings highlight the vital role that digital control, modern electronics, and Internet of Things-enabled supervision play in connecting small, high-density thermal storage and renewable energy generation. This strategy demonstrates the promise of electronics-driven integration for next-generation renewable energy solutions and provides a scalable route toward intelligent, robust, and effective building energy systems. Full article

Ejector-based cooling systems have gathered scientific interest as a low-cost alternative for solar-assisted cooling applications, especially in regions with solar abundance. This work presents the experimental investigation of a solar ejector cooling prototype system. The system, developed at the National Technical University of Athens, includes a custom-made ejector and is powered by a 48 m² flat plate solar collector field, assisted by an auxiliary natural gas boiler. Experimental testing under varying operating conditions was conducted to assess the system’s performance, focusing on the influence of evaporation and condensation temperatures. The maximum coefficient of performance (COP) was measured at approximately 0.160–0.165, corresponding to an entrainment ratio of 0.19 at an evaporation temperature of 9 °C and condensation temperatures of 26–27 °C. Ejector performance substantially declined with increased condensation temperatures. However, the influence of the evaporator pressure on system performance was less significant. These findings demonstrate the feasibility of ejector-based solar cooling as a sustainable solution for reducing electricity use in cooling applications, highlighting the critical influence of operating parameters in the system’s performance optimization. Full article

Solar thermal collectors remain a fundamental component of renewable heat generation in the building sector. Recent progress in solar tracking technologies has led to the emergence of adaptive and stepwise tracking systems that enhance radiation capture while maintaining low mechanical and energy demands. This review comprehensively synthesizes current knowledge on the design, modeling, and performance evaluation of such systems, with emphasis on their role in building decarbonization and techno-economic feasibility. The classification of collectors is revisited to highlight the relationship between optical concentration, tracking precision, and thermal output. Comparative studies indicate that adaptive and stepwise tracking strategies improve annual energy yield by 20–35% compared to fixed systems, while reducing the levelized cost of heat (LCOH) by up to 15%. Modeling approaches integrating optical and thermal domains are discussed alongside emerging applications of artificial intelligence, predictive control, and IoT-based monitoring. The paper concludes with an outlook on future research directions, focusing on durability, standardization, and digital integration of solar thermal systems in smart buildings. Overall, adaptive tracking technologies represent a promising pathway toward efficient and sustainable solar heat utilization in the context of global energy transition. Full article

This study investigates the effect of rotation step size on the performance of flat-plate solar collectors (FPSC) equipped with single-axis tracking. Numerical simulations were carried out in EnergyPlus, coupled with a custom Python interface enabling dynamic control of collector orientation. The analysis was carried out for the city of Kragujevac in Serbia, located in a temperate continental climate zone, based on five representative summer days (3 July–29 September) to account for seasonal variability. Three collector types with different efficiency parameters were considered, and inlet water temperatures of 20 °C, 30 °C, and 40 °C were applied to represent typical operating conditions. The results show that single-axis tracking increased the incident irradiance by up to 28% and the useful seasonal heat gain by up to 25% compared to the fixed configuration. Continuous tracking (ψ = 1°) achieved the highest energy yield but required 181 daily movements, which makes it mechanically demanding. Stepwise tracking with ψ = 10–15° retained more than 90–95% of the energy benefit of continuous tracking while reducing the number of daily movements to 13–19. For larger steps (ψ = 45–90°), the advantage of tracking decreased sharply, with thermal output only 5–10% higher than the fixed case. Increasing the inlet temperature from 20 °C to 40 °C reduced seasonal heat gain by approximately 30% across all scenarios. Overall, the findings indicate that relative single-axis tracking with ψ between 10° and 15° provides the most practical balance between energy efficiency, reliability, and economic viability, making it well-suited for residential-scale solar thermal systems. This is the first study to quantify how discrete rotation steps in single-axis tracking affect both thermal and economic performance of flat-plate collectors. The proposed EnergyPlus–Python model demonstrates that a 10–15° step offers 90–95% of the continuous-tracking energy gain while reducing actuator motion by ~85%. The results provide practical guidance for optimizing low-cost solar-thermal tracking in continental climates. Full article

This present investigative work proceeds with the statistical study of the heat transfer coefficient (CTC) in the different flow transitions that are formed in a horizontal pipe with variation in the angles of inclination in a collector/evaporator component of a heat pump of solar assisted direct expansion (DX-SAHP) by using R600a refrigerant as working fluid in Quito - Ecuador. The dimensions of the collector/evaporator are 3.8 and 1000 mm inside diameter and length, respectively. To determine the results obtained, five practical tests are carried out with inclination angles of 10, 20, 30, 40 and 45°, with speeds or mass flows that vary between 203.24 and 222.28 kg·m⁻²·s⁻¹, the heat fluxes reached values between 200.58 and 507.23 W·m⁻². The correlations proposed by Kattan, Kundu, and Mohseni, and the experimental data were considered for the analysis of the effects of heat transfer on flow patterns. The results obtained from the investigation show that the maximum CTC is 6163.83 W·m⁻²·K⁻¹ with an inclination angle of 45°. Statistical analysis was performed considering the direction of Pearson presented results that for the angle of inclination of 10° a greater inverse direction of −0.316 is obtained. Full article

Solar-energy-driven membrane distillation provides a sustainable pathway to mitigate freshwater scarcity by utilizing an abundant renewable heat source. This study develops a two-dimensional axisymmetric computational fluid dynamics (CFD) model to simulate the transient performance of a hollow fiber water gap membrane distillation (HF-WGMD) module integrated with flat-plate solar collectors (FPCs). A lumped-parameter transient FPC model is coupled with the CFD framework to predict feed water temperature under time-varying solar irradiation, evaluated across four representative days in a Mediterranean city. The model is validated against experimental data, showing strong agreement. A comprehensive parametric analysis reveals that increasing the collector area from 10 to 50 m² enhances the average water flux by a factor of 6.4, reaching 10.9 kg/(m²h), while other parameters such as collector width, tube number and working fluid flow rate exert comparatively minor effects. The module flux strongly correlates with solar intensity, achieving a maximum instantaneous value of 18.4 kg/(m²h) with 35 m² collectors. Multistage HF-WGMD configurations are further investigated, demonstrating substantial reductions in solar energy demand due to internal thermal recovery by the cooling stream. A 40-stage system operating with only 10 m² of solar collectors achieves an average specific thermal energy consumption of 424 kWh/m³, while the overall solar desalination efficiency improves dramatically from 2.6% for a single-stage system with 50 m² collectors to 57.5% for the multistage configuration. The proposed system achieves a maximum freshwater productivity of 51.5 kg/day, highlighting the viability and optimization potential of solar-driven HF-WGMD desalination. Full article

The term SHIP (solar heat for industrial processes) or SHIPs (solar heat for industrial plants) refers to the use of collected solar radiation for meeting industrial heat demands, rather than for electricity generation. The global thermal capacity of SHIP systems at the end of 2024 stood slightly above 1 GWth, which is comparable to the electric power capacity of a single power station. Despite this relatively small presence, SHIP systems play an important role in rendering industrial processes sustainable. There are two aims in the current study. The first aim is to cover various types of SHIP systems based on the variety of their collector designs, operational temperatures, applications, radiation concentration options, and solar tracking options. SHIP designs can be as simple as unglazed solar collectors (USCs), having a stationary structure without any radiation concentration. On the other hand, SHIP designs can be as complicated as solar power towers (SPTs), having a two-axis solar tracking mechanism with point-focused concentration of the solar radiation. The second aim is to shed some light on the status of SHIP deployment globally, particularly in 2024. This includes a drop during the COVID-19 pandemic. The findings of the current study show that more than 1300 SHIP systems were commissioned worldwide by the end of 2024 (cumulative number), constituting a cumulative thermal capacity of 1071.4 MWth, with a total collector area of 1,531,600 m². In 2024 alone, 120.3 MWth of thermal capacity was introduced in 106 SHIP systems having a total collector area of 171,874 m². In 2024, 65.9% of the installed global thermal capacity of SHIP systems belonged to the parabolic trough collectors (PTCs), and another 22% of this installed global thermal capacity was attributed to the unevacuated flat plate collectors (FPC-Us). Considering the 106 SHIP systems installed in 2024, the average collector area per system was 1621.4 m²/project. However, this area largely depends on the SHIP category, where it is much higher for parabolic trough collectors (37,740.5 m²/project) but lower for flat plate collectors (805.2 m²/project), and it is lowest for unglazed solar collectors (163.0 m²/project). The study anticipates large deployment in SHIP systems (particularly the PTC type) in 2026 in alignment with gigascale solar-steam utilization in alumina production. Several recommendations are provided with regard to the SHIP sector. Full article

The sun represents a potential opportunity for sustainable energy production. The study of solar energy harvesting reinforces this promise, with studies simulating different operating environments by estimating the sun’s orientation toward the south or north, depending on the planet’s location. However, studies for latitudes between 23° South and 23° North are a little-explored area. This research investigates different energy harvesting scenarios in flat-plate collectors, combining different possibilities throughout the year, analyzing the amount of energy captured using algorithms and Monte Carlo simulation. The methodology allows predicting efficiencies above 36% simply by rotating the harvesting devices from north to south or vice versa just twice a year. Full article

The solar thermal collector network (SCN) and the thermal energy storage system (TES) represent 90% of the solar thermal installation (STI) total costs. STI occupies 30 hectares, and any reduction is significant for the environment. The proposed approach, which includes a solar thermal plant with recirculation, a mixer, and a heat exchanger, reduces investment costs and environmental impact. It facilitates mixing in a simple tank. The developed methodology reduces the number of collectors and the size of the storage system. An industrial-powdered milk process is the case study. Two scenarios and the base case were evaluated. The four seasons and critical meteorological conditions were considered. Scenario one, without a heat exchanger, presents energy surpluses in three seasons. The second scenario, with a heat exchanger, heats the feedwater and guarantees the heat load and target temperature on critical days of the year. In this second scenario, it is possible to reduce the tank filling time from 8 to 7 h. Up to five parallels were reduced in both scenarios, with mass flow of 0.125 kg/s and up to 3.75% of the total tank volume of 52.65 m³ (mass flow 0.075 kg/s). The optimized system is cost-effective, and 10.20% of the total cost was reduced. This methodology can be applied to any low-temperature STI. Full article

Achieving net-zero emissions in arid and high-solar-yield regions demands innovative, cost-effective, and scalable energy technologies. This study conducts a comprehensive techno-economic analysis and assessment of a novel hybrid photovoltaic–thermal solar collector (U.S. Patent No. 11,431,289) that integrates a reverse flat plate collector and mini-concentrating solar thermal elements. The system was tested in Qatar and Germany and simulated via a System Advising Model tool with typical meteorological year data. The system demonstrated a combined efficiency exceeding 90%, delivering both electricity and thermal energy at temperatures up to 170 °C and pressures up to 10 bars. Compared to conventional photovoltaic–thermal systems capped below 80 °C, the system achieves a heat-to-power ratio of 6:1, offering an exceptional exergy performance and broader industrial applications. A comparative financial analysis of 120 MW utility-scale configurations shows that the PVT + ORC option yields a Levelized Cost of Energy of $44/MWh, significantly outperforming PV + CSP ($82.8/MWh) and PV + BESS ($132.3/MWh). In addition, the capital expenditure is reduced by over 50%, and the system requires 40–60% less land, offering a transformative solution for off-grid data centers, water desalination (producing up to 300,000 m³/day using MED), district cooling, and industrial process heat. The energy payback time is shortened to less than 4.5 years, with lifecycle CO₂ savings of up to 1.8 tons/MWh. Additionally, the integration with Organic Rankine Cycle (ORC) systems ensures 24/7 dispatchable power without reliance on batteries or molten salt. Positioned as a next-generation solar platform, the Hassabou system presents a climate-resilient, modular, and economical alternative to current hybrid solar technologies. This work advances the deployment readiness of integrated solar-thermal technologies aligned with national decarbonization strategies across MENA and Sub-Saharan Africa, addressing urgent needs for energy security, water access, and industrial decarbonization. Full article

The building sector accounts for nearly 40% of global primary energy consumption, with heating, ventilation, and air conditioning (HVAC) systems contributing significantly to energy use and greenhouse gas emissions. Conventional HVAC systems face challenges in addressing humidity control and efficiency, particularly in cold and dry climates. This research demonstrates the development and transient simulation of a novel solar-assisted desiccant wheel-based system for heating and humidification (SDHH) in Taxila, Pakistan. The proposed system includes a desiccant wheel, heat wheel, water-to-air heat exchanger, and a direct evaporative cooler. An array of flat plate collectors supply hot water to the heat exchanger. TRNSYS simulations investigated the performance of SDHH by evaluating heating capacity, humidification, and indoor temperature and humidity values in winter. Results show that the SDHH system maintained the required temperature in the zone and improved the zone humidity level. The desiccant wheel increased the absolute humidity of product air by 0.003 kg/kg. The average indoor temperature was 21 °C, and the average absolute humidity was around 0.008 kg/kg. These results justify using the proposed system in dry and cold climate conditions. Full article

Solar heaters are a sustainable solution to lower operating heating costs for diverse applications. Improving the design of these devices promotes the adoption of this technology to reduce the environmental impact of traditional gas water heaters. The present paper studies heat transfer along the plate-fins of serpentine-type flat-plate solar collectors. The focus of this investigation is the analysis of tube-to-tube thermal conduction through the absorbent plate and its effect on the heat gain of the circulating fluid. The model used here does not consider the adiabatic boundary condition in the plate mid-distance between tubes but applies the prescribed temperatures of the tubes as a boundary condition for the plate-fins. This type of boundary condition allows for heat conduction between rows of tubes. The analysis demonstrates that tube-to-tube heat conduction along the absorber plate has a detrimental effect on the heat gain of the circulating fluid. This effect is responsible for a decrease of up to 10% of the circulating fluid heat gain. This investigation defines the set of parameters that affect the performance of plate solar heaters because of tube-to-tube thermal conduction along the plates, and it helps to choose operation and designs parameters, leading to better design of these devices. Full article

In many developing African countries, milk safety is often managed through traditional methods such as fermentation or boiling over firewood. While these approaches reduce some microbial risks, they present critical limitations. Firewood dependency contributes to deforestation, depletion of agricultural residues, and loss of soil fertility, which, in turn, compromise environmental health and food security. Solar pasteurization provides a reliable and sustainable method for thermally inactivating pathogenic microorganisms in milk and other perishable foods at sub-boiling temperatures, preserving its nutritional quality. This study aimed to evaluate the thermal and microbial performance of a low-cost solar milk pasteurization system, hypothesized to effectively reduce microbial contaminants and retain milk quality under natural sunlight. The system was constructed using locally available materials and tailored to the climatic conditions of the Savanna ecological zone in West Africa. A flat-plate glass solar collector was integrated with a 0.15 cm thick stainless steel cylindrical milk vat, featuring a 2.2 cm hot water jacket and 0.5 cm thick aluminum foil insulation. The system was tested in Navrongo, Ghana, under ambient temperatures ranging from 30 °C to 43 °C. The pasteurizer successfully processed up to 8 L of milk per batch, achieving a maximum milk temperature of 74 °C by 14:00 GMT. Microbial analysis revealed a significant reduction in bacterial load, from 6.6 × 10⁶ CFU/mL to 1.0 × 10² CFU/mL, with complete elimination of coliforms. These results confirmed the device’s effectiveness in achieving safe pasteurization levels. The findings demonstrate that this locally built solar pasteurization system is a viable and cost-effective solution for improving milk safety in arid, electricity-limited regions. Its potential scalability also opens avenues for rural entrepreneurship in solar-powered food and water treatment technologies. Full article

An experimental setup was developed, incorporating a monitored DualSun^® photovoltaic–thermal (PV/T) panel and a weather station to continuously record real-time climatic conditions. This setup enables an hour-by-hour comparison between the actual performance observed under real-world conditions and the predictions generated by the thermal model. The generated dataset was used to evaluate a thermal model derived from the literature, comparing its predictions with measured data. The model adopts a quasi-steady-state, one-dimensional approach based on heat balance equations applied to both the photovoltaic cells and the heat transfer fluid. Conducted during the summer of 2022, the experiment provides valuable insights into the accuracy of the literature-based thermal model under summer meteorological conditions. The results show a good correlation between the experimental data and the model’s predictions. The average deviation observed for the outlet fluid temperature is 0.1 °C during the day and 1.3 °C at night. Consequently, the findings underscore the model’s effectiveness for evaluating daytime performance, while also pointing out its limitations for nighttime predictions, especially when hybrid PV/T collectors are used for applications such as nighttime free cooling. Full article

Decarbonisation in hot climates demands innovative cooling solutions that minimise environmental impact through renewable energy integration and advanced system optimisation. This study investigates the energetic and economic feasibility of a thermo-mechanical vapour compression (TMVC) cooling system that integrates a conventional vapour compression cycle with an ejector and a thermally driven second-stage compressor powered by solar-heated water from evacuated flat-plate collectors. The system is designed to reduce mechanical compressor work and enhance cooling performance in hot climates. A comprehensive 4E (energy, exergy, economic, and environmental) analysis is conducted for a multi-story residential building in Baghdad, Iraq, with a total floor area of approximately 8000 m² and a peak cooling demand of 521.75 kW. Numerical simulations were conducted to evaluate various configurations of solar collector areas, thermal storage tank volumes, and collector mass flow rate, aiming to identify the most energy-efficient combinations. These optimal configurations were then assessed from economic and environmental perspectives. Among them, the system featuring a 600 m² collector area and a 34 m³ storage tank was selected as the optimal case based on its superior electricity savings and energy performance. Specifically, this configuration achieved a 28.28% improvement in the coefficient of performance, a 22.05% reduction in energy consumption, and an average of 15.3 h of daily solar-assisted operation compared to a baseline vapour compression system. These findings highlight the potential of the TMVC system to significantly reduce energy usage and environmental impact, thereby supporting the deployment of sustainable cooling technologies in hot climate regions. Full article