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• Transmitting lens-walled compound parabolic concentrator (TLWCPC) as skylight. • The smart daylighting control potential of TLWCPC was analyzed and validated. • The effects of the orientation direction and inclination angle were analyzed. • The annual smart daylighting control performance in five cities was investigated. Regulation of solar transmission through windows offers the potential to reduce energy consumption in buildings. Recently, the daylighting control characteristic of optical concentrators have drawn considerable research attentions owing to their variable transmittance in response to sun motion. In this research, we aim to propose and validate a novel way to smartly regulate the indoor daylighting environment while generating renewable electricity generation at the same time through the concentrating photovoltaic/Daylighting (TLWCPC-PV/D) skylight. This research particularly focuses on the evaluation of smart daylighting control (SDC) performance of it. The optical model of the TLWCPC-PV/D skylight was built with using ray-tracing simulation technique, which is also validated by experiment results. Because of the variable optical concentration process, the TLWCPC shows obvious SDC characteristic: when –32°＜ θ ＜32°, average daylighting efficiency is 11.15% while when −43°≤ θ ≤ –32° and 32°≤ θ ≤ 43°, average daylighting efficiency is 58.89%. Five cities with different latitudes are selected to perform the yearly daylighting control analysis. The comparative results indicated that orientation direction has an essential impact on SDC characteristic of the TLWCPC-PV/D skylight and the system in the North-South orientation shows excellent SDC ability i.e. it shows larger daylighting efficiency during the early morning and later afternoon periods while maintains lower daylighting efficiency during the noon period. Compared with other complex and expensive energy-saving glasses, the TLWCPC-PV/D skylight smartly adjusts the solar transmission through the optical concentration process according to sun motion and offers a new strategy of easy fabrication and multi-energy use that opens avenues for both static solar concentrator design and SDC mechanism in energy-saving buildings. [ABSTRACT FROM AUTHOR]

A solar concentrating system incorporated to the south-facing wall could be a promising solution to alleviate the energy demand pressure in buildings. However, concentrating systems incorporated in south-facing walls would require wide acceptance range of concentrators with the purpose of static installation. In order to tackle this problem, this article proposes a novel unitary asymmetric concentrator structure for incorporating the concentrating system in the south-facing wall. A general optimization strategy for the annual performance enhancement of the concentrator is reported. Four kinds of concentrators were designed based on the proposed structure. The annual performance enhancement by this optimization strategy was analysed and compared through the ray-tracing simulation and experimental validation for four typical types of solar concentrators, i.e. Mirror Concentrator, Lens-Mirror Concentrator, Dielectric Concentrator and Air-Gap-Lens-Mirror Concentrator. The optical performance of these concentrators was studied and compared. Their application was analysed and validated through the analysis. The findings have illustrated the optical efficiency of the concentrators for concentrating the photovoltaics or photovoltaic-thermal system incorporated to the south-facing wall either by attachment or embedded into a building structure like a window. These concentrators can be engineered as the main component as a part of the design for a building. [ABSTRACT FROM AUTHOR]

Low-concentration PV (CPV, concentrating photovoltaic) technology is a promising concept because it can work with the fixed installation. However, besides the economic consideration, the environmental impacts of the CPV module throughout its life cycle should be addressed as compared with the flat PV technology. Thus, in this paper, a novel high optical performance low-concentration concentrator namely asymmetric compound parabolic concentrator (aCPC) for building south wall integration is proposed. And based on the proposed aCPC-PV module, a life cycle assessment (LCA) has been performed for the low-concentration PV in China to make a scientific comparison with the PV module with the same output level environmentally. Several environmental indicators are calculated for Beijing, Hefei, Lhasa, Lanzhou, Harbin. The primary energy demand, energy payback time and environmental impacts are considered over the entire life cycle of the aCPC-PV module. The results show that the primary energy demand, energy payback time and environmental impacts of the aCPC-PV module are all relatively lower than that of the PV module with the same output. It is confirmed by the LCA study that the aCPC-PV module on behalf of the low-concentration PV technology is still a feasible and effective way for actual engineering because it’s more economic and more environmental friendly than the PV technology although the PV is experiencing continuous decrease in price and increase in efficiency. [ABSTRACT FROM AUTHOR]

Concentrated photovoltaic (CPV) technology as a typical PV application is becoming popular due to its advantages of high conversion efficiency and low cost etc. However an important issue for CPV technology is the non-uniformity on the illumination and the temperature which can finally influence the overall electrical efficiency of solar cells. This study presents the feature of the non-uniform illumination and temperature, and reviews the cause and harm of the non-uniform illumination and temperature. Then the specific effect on cell parameters of different solar cells is analyzed, and finally the improving methods for reducing this negative effect on concentrating solar cells are proposed. This review will help researchers to learn the effect of the non-uniformity on the illumination and the temperature, and common improvement method, which will benefit CPV design and optimization. [ABSTRACT FROM AUTHOR]

The hybrid photovoltaic-daylighting window system has aroused more and more attention in recent years, because of its higher solar energy utilization ratio and better adaptability to building's energy consumption. In this area, the concentrator-PV type glazing technology is an important branch that smartly adopts the optical concentrators to realize the efficient use of solar energy for renewable electricity generation and daylighting at the same time. A novel transmitting lens-walled compound parabolic concentrator (TLWCPC) is designed, which is able to achieve the function of daylighting without decreasing its optical efficiency. Based on the TLWCPC, the TLWCPC-Photovoltaic/Daylighting (TLWCPC-PV/D) system is designed. Considering that the sun rays for daylighting will experience complex optical transmission processes in the concentrator, the proportion and amount of the diffuse solar irradiance have significant impacts on the overall daylighting performance of the concentrator-type PV glazing systems in both daylighting energy level and distribution uniformity. In order to address this issue, in this research, the ray-tracing simulation model for the TLWCPC-PV/D system installed on the roof of a typical office room is developed and the experimental results under sunny and overcast weather conditions are used to validate the accuracy and confidence of it. The validated ray-tracing model is then used to evaluate the effects of the proportion of the diffuse solar irradiance with the total solar irradiance set at a constant value on the overall daylighting performance of the TLWCPC-PV/D system at different incidence angles. It is found through the simulation results that at different incidence angles, the daylighting energy levels on the analysis grid show obvious decreasing trends with the increase of the proportion of the diffuse solar irradiance via different rates but the distribution uniformity of them is enhanced significantly. Finally, two actual tested weather profiles on either date with different proportions of the diffuse solar irradiance are selected to make the daily energy performance analysis for the TLWCPC-PV/D system, which further emphasizes the effects of the diffuse solar irradiance on the concentrating solar systems. • The ray-tracing simulation model for the TLWCPC-PV/D module was built considering the diffuse solar irradiance. • The simulation model was validated using the experimental results under different weather conditions. • The effects of the diffuse solar irradiance on the daylighting performance of the TLWCPC-PV/D window were analyzed. • The daily energy performance analysis was performed for the TLWCPC-PV/D window. [ABSTRACT FROM AUTHOR]

This paper aims to present a novel concentrator-photovoltaic window (CPVW) for the building application, which is able to provide a uniform daylighting environment. In order to study the daylighting performance of the CPVW, the ray-tracing simulation model for the complex window systems are built and validated by the outdoor experimental results. The daylighting uniformity of the proposed window system is analyzed and compared with the state-of-the-art semi-transparent photovoltaic window system (STPVW). The coefficient of variation (CV) is developed to evaluate the daylighting uniformity of photovoltaic windows. It was found that with the use of the CPVW, the daylighting uniformity can be significantly enhanced, while enlarging the active daylighting area at the same time: the CV values are decreased from 0.647, 0.642, 0.606, 0.595, 0.639, 0.624, 0.764 (for the STPVW) to 0.011, 0.044, 0.054, 0.054, 0.113, 0.171, 0.220 (for the CPVW) at various incidence angles. Due to the sun rays reallocation of the concentrator, the active daylighting area can also be enlarged: the ratio of the active illumination area offered by the CPVW to that by the STPVW can be up to 6.69 ×. Thus, with the use of the concentrator-photovoltaic window system on the building, not only can the solar energy utilization be greatly enhanced and does suit the building energy demands well, but also it improves the daylighting uniformity and active natural daylighting area significantly. • A novel concentrator based multi-functional BIPV window was introduced. • The daylighting performance of the concentrator-PV window was investigated through validated ray-tracing simulation modell. • The concentrator-PV window can provide much more uniform daylighting environment. • The concentrator-PV window can illuminate as larger area as up to 6.7 times of its own size. [ABSTRACT FROM AUTHOR]

• It summarizes the building integrated solar concentrating systems according to different functions. • It introduces the demands, types, applications and structures of the building integrated solar concentrating systems. • It presents prospects/directions/policies around the world towards the building integrated solar concentrating systems. In the building sector, concerns towards the vast energy consumption has promoted the development of renewable energy technologies. In this regards, the solar concentration devices show a promising concept for building applications. However, the solar concentrators for application in buildings have many restrictions, which are different from the traditional solar concentrators. The main objective of this paper is to present a concise review on the building integrated concentrating devices, that have their own characteristics and multiple functions. This paper made a classification based on device's functions, i.e. building integrated concentrated photovoltaic systems (BICPV), building integrated concentrating solar thermal (BICST) and building integrated concentrating solar daylighting (BICSD) and the combination of functions, i.e. BICPV/T, BICPV/D, BICST/D and BICPV/T/D. At the same time, this paper presented an elaborate introduction of the demands, types and applications of the building integrated concentrating devices and prospects/ directions/ policies about these technologies around the world. The review would provide important information for the actual engineering of building integrated concentrating devices. [ABSTRACT FROM AUTHOR]