Search Results (74)

Many studies on solar heating systems have examined individual techniques to enhance the performance of solar water collectors, such as flow obstructions, increased turbulence, nanofluids, and investment in thermal storage. The benefits of integrating these sustainability strategies into a single, sustainable system have yet to be fully established. This work displays a hybrid water-heating system that contains a solar water collector (SWC) and an electric water heater (EWH), a photovoltaic panel (PV), and nano-additives to increase the outlet water temperature and improve thermal efficiency. Numerical and experimental analyses were used to estimate the influence of water flow rate (2.5, 3.5, and 4.5 L/min) and different Al₂O₃ concentrations (0.1%, 0.2%, and 0.3%) on system performance using U-shaped pipe in SWC model. The results highlight that lower flow rates consistently yield higher ΔT values because water spends a longer time in the collector, allowing it to absorb more heat. Also, when using water only, the collector efficiency increases pro-aggressively with flow rate. A significant performance enhancement is observed upon incorporating Al₂O₃ nanoparticles into the fluid, with a 0.1% Al₂O₃ volume concentration improving efficiency by ~7.4% over water. At 0.3%, the highest improvement is recorded, yielding a ~9.3% gain in efficiency compared to the base case. Full article

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

Although numerous studies have investigated individual methods to improve the performance of solar air heaters (SAHs), such as flow obstruction barriers, porous media, nanofluids, and thermal energy storage units, the overall integration of these reinforcement strategies into a unified, sustainable system remains to be defined. The current study presents a hybrid solar air heating configuration that combines a solar air collector (SAC) with an electric air heater (EAH) powered by photovoltaic (PV) panels, aiming to stabilize outlet air temperature and enhance overall thermal efficiency. Experimental and numerical approaches were employed to evaluate the influence of barrier geometry (flat, trapezoidal, and V-groove) and airflow rate (53, 158, and 317 L/min) on system performance using three SAC models. Experimental results revealed that lower airflow rate promotes greater temperature rise (ΔT) due to longer air–surface contact, while V-groove barriers achieved the highest ΔT and collector efficiency among all configurations. At higher airflow rates, the absorbed energy factor Fc (τα) increased to approximately 0.73, whereas the heat loss factor FcU decreased, indicating reduced thermal losses and improved energy transfer. Model III demonstrated the most effective heat absorption, confirming its superior thermal design. The integrated SAC–EAH system exhibited improved overall efficiency, with the SAC functioning effectively as a preheating unit and the EAH sustaining thermal stability during variable solar conditions. Numerical results showed that the highest temperature difference occurs at the V-groove barriers at an air flow rate of 53 L/min. In contrast, the difference between inlet and outlet temperatures decreases across the remaining models, with reduced percentages of 11.8% and 12.7% for Model II and Model I, respectively. Numerical simulations ensured the experimental outcomes, showing close agreement with the temperature variation trends and validating the system’s enhanced thermal performance. Full article

Photovoltaic-thermal (PVT) solar collector technologies are considered a highly efficient solution for sustainable energy generation, capable of producing electricity and heat simultaneously. This paper reviews and discusses different aspects of PVT collectors, including fundamental principles, materials, diverse classifications, such as air-type and water-type, and different cooling mechanisms to boost their performance, such as nano-fluids, Phase Change Materials (PCMs), and Thermoelectric Generators (TEGs). At the system level, this paper analyses PVT technologies’ integration in buildings and industrial applications and gives a comprehensive market overview. The methodology focused on evaluating advancements in design, thermal management, and overall system efficiency based on existing literature published from 2010 to 2025. From the findings of various studies, water-based PVT systems provide electrical efficiencies ranging from 8% to 22% and thermal efficiencies between 30% and 70%, which are almost always higher than air-based alternatives. Innovations, including nanofluids, phase change materials, and hybrid topologies, have improved energy conversion and storage. Market data indicates growing adoption in Europe and Asia, stressing significant investments led by Sunmaxx, Abora Solar, Naked Energy, and DualSun. Nonetheless, obstacles to PVT arise regarding aspects such as cost, design complexity, lack of awareness, and economic incentives. According to the findings of this study, additional research is required to reduce the operational expenses of such systems, improve system integration, and build supportive policy frameworks. This paper offers guidance on PVT technologies and how they can be integrated into different setups based on current normativity and regulatory frameworks. 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

This study investigates the electro-thermal transient response of a photovoltaic–thermal (PV/T)–heat pump system under dynamic disturbances to optimize operational stability. A dynamic model integrating a PV/T collector and a heat pump was developed by the transient heat current method, enabling high-fidelity simulations of step perturbations: solar irradiance reduction, compressor operation, condenser water flow rate variations, and thermal storage tank volume changes. This study highlights the thermal storage tank’s critical role. For V_tank = 2 m³, water tank volume significantly suppresses the water tank and PV/T collector temperature fluctuations caused by solar irradiance reduction. PV/T collector temperature fluctuation suppression improved by 46.7%. For the PV/T heat pump system in this study, the water tank volume was selected between 1 and 1.5 m³ to optimize the balance of thermal inertia and cost. Despite PV cell electrical efficiency gains from PV cell temperature reductions caused by solar irradiance reduction, power recovery remains limited. Compressor dynamic performance exhibits asymmetry: the hot water temperature drop caused by speed reduction exceeds the rise from speed increase. Load fluctuations reveal heightened risk: load reduction triggers a hot water 7.6 °C decline versus a 2.2 °C gain under equivalent load increases. Meanwhile, water flow rate variation in condenser identifies electro-thermal time lags (100 s thermal and 50 s electrical stabilization), necessitating predictive compressor control to prevent temperature and compressor operation oscillations caused by system condition changes. These findings advance hybrid renewable systems by resolving transient coupling mechanisms and enhancing operational resilience, offering actionable strategies for PV/T–heat pump deployment in building energy applications. Full article

The purpose of the study is to investigate the energy performance of a PVT collector in combination with a heat pump. First, a test system combining a heat pump and PVT module is built, and then its performance is carefully measured, assessing the electricity and heat production. The paper focuses on increasing the efficiency of a photovoltaic (PV) panel (as part of the PVT module) by cooling it with a heat pump. The main idea is to use the heat generated by the warming panels as a low-temperature source for the heat pump. The research aims to maximize the use of solar energy in the form of both electricity and heat. In traditional PV systems, the panel temperature rise reduces the solar-to-electric conversion efficiency. Therefore, cooling with a heat pump is increasingly used to keep panels at optimal temperatures and improve performance. The tests confirm that cooling the panels with a heat pump results in an 11.4% improvement in electrical efficiency, an increase from 10.8% to 12.0%, with an average system efficiency of 11.81% and a temperature coefficient of –0.37%/°C. The heat pump achieves a COP of 3.45, while thermal energy from the PVT panel accounts for up to 60% of the heat input when the air exchanger is off. The surface temperature of the PVT panels varies from 11 °C to 70 °C, and cooling enables an increase in electricity yield of up to 20% during sunny periods. This solution is especially promising for facilities with year-round thermal demand (e.g., swimming pools, laundromats). Full article

Steam is widely used in industry as a heat carrier for thermal processes and is primarily generated by gas-fired steam boilers. The decarbonization of industrial thermal demand relies on the capability of clean and renewable technologies to provide steam through reliable and cost-effective systems. Concentrating solar thermal technologies are attracting attention as a heat source for industrial steam generation. In addition, electricity-driven high-temperature heat pumps can provide heat using either renewable or grid electricity by upgrading ambient or waste heat to the required temperature level. In this study, linear Fresnel solar collectors and high-temperature heat pumps driven by photovoltaics are considered heat sources for steam generation in industrial processes. Energetic and economic analyses are performed across the European countries to assess and compare their performances. The results demonstrate that for a given available area for the solar field, solar thermal systems provide a higher annual energy yield in southern countries and at lower costs than heat pumps. On the other hand, heat pumps driven by photovoltaics provide higher annual energy for decreasing solar radiation conditions (central and northern Europe), although it leads to higher costs than solar thermal systems. A hybrid scheme combining the two technologies is the favorable option in central Europe, allowing a trade-off between the costs and the energy yield per unit area. 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

The implementation of renewable energy systems (RESs) in the agricultural sector has significant potential to mitigate the negative effects of fossil fuel-based products on the global climate, reduce operational costs, and enhance crop production. However, the intermittent nature of RESs poses a major challenge to realizing these benefits. To address this, thermal energy storage (TES) and hybrid heat pump (HHP) systems are integrated with RESs to balance the mismatch between thermal energy production and demand. In pursuit of clean energy solutions in the agricultural sector, a 3942 m² greenhouse in Yeoju-si, South Korea, is equipped with 231 solar thermal (ST) collectors, 117 photovoltaic thermal (PVT) collectors, four HHPs, two ground-source heat pumps (GSHPs), a 28,500 m³ borehole TES (BTES) unit, a 1040 m³ tank TES (TTES) unit, and three short-term TES units with capacities of 150 m³, 30 m³, and 30 m³. This study evaluates the long-term performance of the integrated hybrid renewable energy and thermal energy storage systems (HRETESSs) in meeting the greenhouse’s heating and cooling demands. Results indicate that the annual system performance efficiencies range from 25.3% to 68.5% for ST collectors and 31.9% to 72.2% for PVT collectors. The coefficient of performance (COP) during the heating season is 3.3 for GSHPs, 2.5 for HHPs using BTES as a source, and 3.6 for HHPs using TTES as a source. During the cooling season, the COP ranges from 5.3 to 5.7 for GSHPs and 1.84 to 2.83 for ASHPs. Notably, the HRETESS supplied 3.4% of its total heating energy directly from solar energy, 89.3% indirectly via heat pump utilization, and 7.3% is provided by auxiliary heating. This study provides valuable insights into the integration of HRETESSs to maximize greenhouse energy efficiency and supports the development of sustainable agricultural energy solutions, contributing to reduced greenhouse gas emissions and operational costs. Full article

This paper reviews recent advancements in integrated thermoelectric power generation and water desalination technologies, driven by the increasing global demand for electricity and freshwater. The growing population and reliance on fossil fuels for electricity generation pose challenges related to environmental pollution and resource depletion, necessitating the exploration of alternative energy sources and desalination techniques. While thermoelectric generators are capable of converting low-temperature thermal energy into electricity and desalination processes that can utilize low-temperature thermal energy, their effective integration remains largely unexplored. Currently available hybrid power and water systems, such as those combining conventional heat engine cycles (e.g., the Rankine and Kalina cycles) with reverse osmosis, multi-effect distillation, and humidification–dehumidification, are limited in effectively utilizing low-grade thermal energy for simultaneous power generation and desalination, while solid-state heat-to-work conversion technology, such as thermoelectric generators, have low heat-to-work conversion efficiency. This paper identifies a key research gap in the limited effective integration of thermoelectric generators and desalination, despite their complementary characteristics. The study highlights the potential of hybrid systems, which leverage low-grade thermal energy for simultaneous power generation and desalination. The review also explores emerging material innovations in high figure of merit thermoelectric materials and advanced MD membranes, which could significantly enhance system performance. Furthermore, hybrid power–desalination systems incorporating thermoelectric generators with concentrated photovoltaic cells, solar thermal collectors, geothermal energy, and organic Rankine cycles (ORCs) are examined to highlight their potential for sustainable energy and water production. The findings underscore the importance of optimizing material properties, system configurations, and operating conditions to maximize efficiency and output while reducing economic and environmental costs. Full article

Emerging trends in heat pump (HP) and electric vehicle (EV) adoption within communities aim to reduce carbon emissions in the heating and transportation sectors. However, these technologies rely on grid electricity, whose carbon intensity varies over time. This study explores how the carbon-saving potential of these technologies can be further enhanced through demand-shifting operations and renewable energy integration. The research compares photovoltaic–thermal (PV/T) and hybrid solar heat pump systems that integrate EV charging and PCM-enhanced heat storage to improve space heating efficiency under low solar irradiance in the UK while reducing CO₂ emissions. The study simulates solar collector configurations and sizes, combining PV modules and heat pumps to enhance system performance. Control systems synchronize operations with periods of low grid CO₂ intensity, minimizing the environmental impact. The analysis evaluates PV/T systems, separate PV and thermal collectors, highlighting their energy efficiency and CO₂ reduction potential. Control systems further optimize HP operation and EV charging during periods of high renewable energy availability, preventing uncontrolled use that could result in elevated emissions. Using real weather data and a detailed building model, the findings show that a solar-assisted HP with 100% thermal collectors achieves a daily COP of 3.49. Reducing thermal collectors to 60% lowers the COP to 2.57, but PV output compensates, maintaining similar emission levels. The system achieves the lowest emission with high-efficiency evacuated flat plate PV/T collectors. Full article

The effects of global warming are severely recognizable and, according to the OECD, 47% of the world’s population will soon live in regions with insufficient drinking water. Already, many countries depend on desalination for fresh water supply, but such facilities are often powered by fossil fuels. This paper presents an energy self-sufficient desalination system that runs entirely on solar power. Sunlight is harvested using parabolic trough collectors with an effective aperture area of 1.5 m × 0.98 m and a theoretical concentration ratio of 150 suns, in which a concentrator photovoltaic thermal (CPV-T) hybrid-absorber converts the radiation to electricity and heat. This co-generated energy runs a multi-effect distillation (MED) plant, whereby the waste heat of multi-junction concentrator solar cells is used in the desalination process. This concept also takes advantage of synergy effects of optical elements (i.e., mirrors), resulting in a cost reduction of solar co-generation compared to the state of the art, while at the same time increasing the overall efficiency to ~75% (consisting of an electrical efficiency of 26.8% with a concurrent thermal efficiency of 48.8%). Key components such as the parabolic trough hybrid absorber were built and characterized by real-world tests. Finally, results of system simulations, including fresh water output depending on different weather conditions, degree of autonomy, required energy storage for off-grid operation etc. are presented. Simulation results revealed that it is possible to desalinate around 2,000,000 L of seawater per year with a 260 m² plant and 75 m³ of thermal storage. Full article

Solar electric and solar thermal energies are often considered as part of the solution to the current energy emergency. The pipes of flat plate solar devices are normally heated by their upper surfaces giving rise to an asymmetric temperature field in the bulk of the fluid, which influences the heat transfer process. In the present work, a study of the characteristic length of tubes, or most efficient distance at which heat transfer occurs, in flat photovoltaic-thermal (PVT) hybrid solar devices has been carried out using three heat transfer fluids: water, [Emim]Ac ionic liquid and ionanofluid of graphene nanoparticles suspended in the former ionic liquid. The mean objective of the study was to know whether the heat transfer occurs in optimal conditions. Experimental measurements have been made on a commercial PVT device, and numerical simulations have been performed using the HEATT^® platform to determine the characteristic length of the process. The tests conducted showed a clear improvement in the temperature jump of the fluid inside the collector when INF is used compared to water and ionic liquid and even a higher overall energy efficiency. Electricity generation is not greatly affected by the fluid used, although it is slightly higher when water is used. Slower fluid velocities are recommended if high fluid outlet temperatures are the goal of the application, but this penalizes the overall thermal energy production. The characteristic process length is not typically achieved in parallel tube PVT collectors with ordinary flow rates, which would require a speed, and consequently, a flow rate, about 10 times lower, which penalizes the performance (up to four times), although it increases the fluid outlet temperature by 234%, which can be very interesting in certain applications. Ionanofluids may in the medium term become an alternative to water in flat plates or vacuum solar collectors for applications with temperatures close to or above 100 °C, when their costs will hopefully fall. The results and methodology developed in this work are applicable to solar thermal collectors other than PVT collectors. Full article

A novel concentrating photovoltaic-thermal solar collector was designed, fabricated and experimentally investigated at the University of Lleida, in Spain. Two designs based on two dielectric liquids, isopropyl alcohol (IPA) and deionised water (DIW), were developed. In both cases, the solar cells were directly liquid-immersed. The study includes experiments and numerical simulations. The proposed concentrator was incorporated into a testing unit to examine its potential as a façade by controlling light and thermal flux transmitted into a building. The results show promising electrical performance and acceptable thermal performance, with thermal losses ranging from 14 to 20 W °C⁻¹m⁻². The optical efficiency was around 73% in the case of the concentrator with DIW and about 76% for the one with IPA. Regarding electrical performance, the fill factors for IPA and DIW configurations are as follows: 62.8% and 61.7%, respectively. The comparison results reveal striking differences between the testing unit with and without solar concentrators, with the concentrator-equipped unit showing around four times lower illuminance and a 50% reduction in maximum heat fluxes and interior temperature. Generally speaking, it can be said that these energy-generating façades show satisfactory behaviour and offer interesting possibilities for building-integrated applications. Full article