A novel concentrating photovoltaic curtain wall (CPV-CW) system integrated with building has been designed, tested and analyzed, and its application potential is determined and improvement suggestions are proposed. It can effectively improve the efficiency of photovoltaic (PV) module and provide a more uniform indoor lighting environment. The concentrator is constructed with truncated stationary asymmetric compound paraboloid. And cyclic olefin copolymer (COC) with high transmittance is selected as its structural material. A model building combined with CPV-CW system curtain wall has been designed and applied to the outdoor experiments. It was tested on its electricity generation efficiency, the internal lighting environment, and thermal insulation ability. According to the real time results, under the clear weather conditions, the transmittance of the CPV-CW system reaches 9.1%. The highest CPV-CW system generation efficiency, 26.5%, could be found in winter, followed by the autumn and summer separately. In addition, CPV-CW system can create a more uniform indoor light environment and meet the requirements of building insulation. Based on the analysis, the CPV-CW system has a broad application prospect for building integrated with concentrating photovoltaic.
High temperature and overheating of photovoltaic panels lead to efficiency losses and eventual degradation. For solar PV systems, this is a significant impediment for achieving economic viability. In this study, a novel Window-Integrated Concentrated Photovoltaic (WICPV) system is proposed for window integration. This offers high (50%) transparency and is fabricated and characterised indoors at an irradiance of 1000 Wm−2. Its electrical performance is tested (a) without applied cooling (i.e., under natural ventilation) and (b) with a heat sink to accommodate passive cooling media. The results are compared to study the effects of reduction in operating temperature on system performances. The effectiveness of a sensible cooling medium (water) and two latent heat removal media, phase change materials (or PCMs, RT50 and RT28HC), is investigated. This paper reports the passive temperature regulation of this WICPV at ambient testing conditions. The results demonstrate an increase in electrical power output by (i) 17% (RT28HC), (ii) 19% (RT50), and (iii) 25 % (circulating water) compared with the naturally ventilated system. This shows that PCMs are considerably useful for thermal regulation of the WICPV. Any improvement in efficiencies will be beneficial for increasing electrical energy generation and reducing peak energy demands.
Semi-transparent Building Integrated Photovoltaics provide a fresh approach to the renewable energy sector, combining the potential of energy generation with aesthetically pleasing, multi-functional building components. Employing a range of technologies, they can be integrated into the envelope of the building in different ways, for instance, as a key element of the roofing or façade in urban areas. Energy performance, measured by their ability to produce electrical power, at the same time as delivering thermal and optical efficiencies, is not only impacted by the system properties, but also by a variety of climatic and environmental factors. The analytical framework laid out in this paper can be employed to critically analyse the most efficient solution for a specific location; however, it is not always possible to mitigate energy losses, using commercially available materials. For this reason, a brief overview of new concept devices is provided, outlining the way in which they mitigate energy losses and providing innovative solutions for a sustainable energy future.
We propose two energy-mapping methods to produce a uniformly illuminated area for a nontilted (straight) and a tilted light source toward a target plane. These energy-mapping methods define the positions of the desired points (the destination points of the refracted rays of a light source) on an illuminated area. The surface of the lenses can then be formed through the position of the desired points. Based on these design methods, two freeform lenses, (i) a symmetric lens and (ii) an asymmetric lens, were designed to provide uniformity within a rectangular illumination footprint for a nontilted and a tilted light source, respectively. This method can produce uniformity for a tilted light source within 0 deg to 45 deg toward the normal vector on the target plane. Two freeform lenses for 0 deg and 20 deg tilted toward a target plane were designed. The illumination footprint of the symmetric and asymmetric freeform lenses was evaluated through ray-tracing simulations and experiments. Both models produce over 90% uniformity within an illuminated area.
Perovskite solar cell (PSC) technology is the flag bearer for the future of photovoltaics allowing unlimited possibilities for its application. This technology is currently limited by issues related to its scale-up, stability and the composition of the materials used in its preparation. Using small sized solar cells with higher efficiency under solar concentration is gaining traction as a methodology for scaling up this technology and broadening its applications. However, this has only been reported in devices with size <1 mm2 neglecting the series resistance of the device. Here, we report the performance of a 9 mm2 PSC at varying solar concentration levels and correlate it with the series resistance of the solar cell. The n–i–p structured device using a triple cation perovskite absorber with a mesoporous titanium oxide/SnO2 layer as the electron transporting layer and Spiro-OMeTAD as the hole transporting material achieved a peak efficiency of 21.6% under 1.78 Suns as compared to the 21% obtained under 1 Sun (1000W m−2) and AM1.5G. We further boosted the power output up to 15.88 mW under 10.7 Suns compared to the 1.88 mW obtained under 1 Sun; however this results in an actual efficiency drop of the PSC owing to the device series resistance. Further, we investigated the impact of the increasing solar cell temperature at higher concentration levels and identified the influence of series resistance on the performance of the PSC. Our work identifies the potential of concentrating photovoltaics and highlights the challenges and makes recommendations for future development.
Concentrating Photovoltaic/Thermal (CPV/T) systems can harness the freely available solar energy to simultaneously generate electricity and sensible heat. Using the principles of optical concentration, they can generate more electrical energy per unit area of solar cells and provide a better quality of thermal energy. In this work, we have developed an analytical model to simulate and predict the performance of a dense array hybrid CPV/T collector called “SUNTRAP.” The concentration of incident radiation is achieved using a reflective type three-dimensional cross-compound parabolic concentrator (3DCCPC) with a geometric concentration ratio of 3.6 × . The extraction of heat from the solar cells is achieved by allowing water to flow through the copper cooling duct on which the solar cells with CCPC are bonded. Using previously developed algorithms, the optical efficiency of the CCPC is calculated as a function of solar azimuth and altitude angle. The obtained optical efficiency is coupled to the thermal model to obtain the temperature distribution in the collector. The numerical results are in good agreement with the experimental measurements obtained at the outdoor solar laboratory at Penryn Campus, Cornwall. The average deviation in outlet water temperature between the numerical and experimental ones is 1.9%. The total electrical and thermal energy obtained from the CCPC-PV/T module on an experimental day is 1.21 kWh/m2 and 46.46 kWh/m2. A parametric study was done to obtain the effect of flow rate and external wind velocity on the performance of the collector. The solar cell temperature is found to decrease with an increasing flow rate. The performance prediction of the CCPC-PV/T module at Penryn shows that the module produced maximum energy in August, producing 7.51 kWh/m2 of useful energy. An economic analysis was performed to obtain the Levelized cost of electricity (LCOE) that the CCPC-PV/T module can deliver, and the LCOE was found to be £1.08/kWh. The coupled model is also utilised to predict the performance of the system for five different geographical locations, including Chennai, Rome, Alice Springs, Montreal, and Barrow. The model considers optimum panel tilt and time-dependent optical efficiency of the concentrator while estimating the energy output. Based on the results, the overall performance of the collector was found to be good in Chennai, with an annual electrical energy gain of 51.95 kWh/m2 and an annual thermal energy gain of 1164 kWh/m2.
The 3D concentrating photovoltaic is innovated integrated into the building as the window, which can improve the efficiency of photovoltaic (PV) cell and maintain the daylighting performance for the building. The lab test results showed that 3D concentrator photovoltaic daylighting (3D CPVD) modules could increase the maximum power by 2.89 times compared with bare cells, and its outdoor performance is comprehensively analyzed through the simulation and experimental research. The application prospect in globalization is also explored. Its electrical performance in outdoor environment under different weather and different open angles was tested and analyzed. 3D CPVD window with adjustable angle achieves the balance between daylighting and power generation. And it has the best electrical performance at 60° in low and middle latitudes. In addition, 3D CPVD windows with the transmittance of 9.47% can provide the brighter and more uniform interior daylighting environment. The simulation results show that the indoor annual useful daylight illuminance (UDI) is over 85%. Finally, the application prospects of the 3D CPVD window was analyzed by the life cycle assessment (LCA) method. Its energy payback time is less than 12 years in typical cities around the world, which shows its energy-saving and application potential.
A Low Concentrating Photovoltaic Thermal system typically employs compound parabolic concentrator to focus sunlight and enhance the quality of both thermal and electrical energy extracted. One of the major issues during this process is the introduction of non-uniform illumination on the photovoltaic panels which can cause hot-spots and significantly reduce both the reliability and the electrical output from this system. This non-uniform illumination can be mitigated by integrating homogenizers which are typically linear extensions to the compound parabolic concentrators profile also referred to as elongated compound parabolic concentrators. In this work, the performance of a 2.5× Elongated Compound Parabolic Concentrator truncated to 1.7× and connected to a desiccant based cooling system has been explored. For a detailed analysis of the system, a coupled 3-D optical, electrical, thermal and process efficiency model has been developed. A full-scale prototype of the modelled system is also fabricated using a 380-Watt peak photovoltaic panel. Experiments conducted on the developed system showed a peak outlet water temperature of 56 °C at a mass flowrate of 24 L per hour. Comparative studies between compound parabolic concentrators and elongated compound parabolic concentrators based low concentrating photovoltaic thermal system is also presented to showcase the overall improvement in the process efficiency due to the mitigation of non-uniformity. Using a 400 mm length of the homogenizer the spatial non-uniformity factor was found to drop from 0.5 to 0.29 under normal incidence angle and results in a rise of 12% in the electrical output when compared to a compound parabolic concentrators-based system. The coefficient of performance of the desiccant-based air-cooling system is found to increase by 50% when coupled with two series-connected elongated compound parabolic concentrators based low concentrating photovoltaic thermal system. The improvement in coefficient of performance is mainly because of thermal and electrical energy savings from the developed system amounting to 352 kWhe/year and 665 kWhth/year, respectively. Further, the mitigation of non-uniform illumination showed a performance improvement of 5% in the coefficient of performance of the air-cooling system compared to a compound parabolic concentrators-based system.
Semi-transparent photovoltaic (PV) technology is attractive for building-integrated photovoltaics (BIPV) due to its ability to lower the admitted solar heat gain, to control the penetrating daylight and to generate onsite benevolent direct current power. In this work, semi-transparent cadmium telluride (CdTe) based BIPV as window was experimentally characterized using outdoor test cell in temperate UK climate. Spectral measurement confirmed its 25% visible transmission and 12% solar transmission. Thermal transmission and solar heat gain coefficient were calculated from measured thermal data. Overall heat transfer coefficient (U-value) of 2.7 W/m2 K was found for outdoor and indoor characterization of CdTe BIPV window. A comparison with single glazed window has been produced emphasis its feasibility for Facade buildings.
A low concentrator photovoltaic is presented and the optical losses within a double glazed window assembly are described. The use of plastic instead of glass is analyzed for its reduced weight and hence greater power to weight ratios. Although the transmittance of glass is higher, the power to weight ratio of the plastic devices was almost double that of the glass counterparts and even higher than the original non concentrating silicon cell. The plastic Topas material was found to be the best performing material overall. Crystal Clear, a plastic resin, had a higher average transmittance but had a lower optical efficiency due to the cold cast manufacturing process in comparison to injection moulding of the other materials. This proves the importance of considering both the materials and their associated manufacturing quality.
External quantum efficiencies, optical properties, silicon cell temperatures and performance is analyzed for concentrating photovoltaic devices made of varying optical materials. The measurement methods for optical analysis are given in an attempt to separate the optical losses experimentally. The Silicon cells were found to gain higher temperatures due to the insulating plastic optics in comparison to glass but these effects are eliminated during vertical window orientation where instead the encapsulate dominates the insulation of the cell. The results presented here prove plastic optics to be a worthwhile alternative to glass for use in low concentration photovoltaic systems and have the significant effect of reversing the weight disadvantage concentrator photovoltaic technology has compared to standard flat plate solar panels.