The design, construction and experimental characterization of a novel concentrating photovoltaic/daylighting window for green building roof

A novel concentrating photovoltaic/daylighting window to achieve the multi-function of the electricity generation and daylighting for buildings has been designed, constructed and experimentally characterized. It’s found that the concentrating photovoltaic/daylighting window can achieve a transmittance of around 10% for the natural daylight without decreasing the optical efficiency of the concentrator. The overall daylighting and electrical performance of the concentrating photovoltaic/daylighting window are investigated under the real weather condition.The hourly illuminance level, the temperature of the inner environment of the box and transient I–V curves are determined. The short-circuit current, open-circuit voltage maximum power generation, and Fill Factor of the system are derived from eachindividual I–V curve. Through the experiment testing, the illuminance level in the integrating box is in the range of 923-9230 lx with the outside illuminance level exceeds 100000 lx during noon time, which prove that the concentrating photovoltaic/daylighting window can improve the visual comfort for the building interior environment and it can also avoid the building interior environment from overheating and dazzling at noon which is caused by direct sunlight throughtransparent window. The preliminary economic analysis of the new concentrating photovoltaic/daylighting window is also made

An evaluation study of miniature dielectric crossed compound parabolic concentrator (dCCPC) panel as skylights in building energy simulation

The potential of miniature dielectric crossed compound parabolic concentrator (dCCPC) panel as skylights for daylighting control has drawn a considerable research attention in the recent years, owing to its feature of variable transmittance according to the sun position, but the viability of using it as skylights in buildings has not been explored yet comprehensively. This paper aims to study the feasibility of utilizing miniature dCCPC panel as skylight in different locations under various climates in terms of energy saving potential besides its daylighting control function. The transmittance of dCCPC panel varies at every moment according to the sky condition and sun position. Due to this specific property, this study novelly implemented a polynomial formula of the dCCPC transmittance in the Grasshopper platform, from which EnergyPlus weather data can be called to calculate the hourly transmittance data of dCCPC skylight panel throughout the whole year. An hourly schedule of transmittance is generated according to the hourly sky condition determined by the daylight simulation through Radiance and Daysim, and is then input to EnergyPlus simulation to predict the energy consumption of a building with dCCPC skylight. Fourteen locations around the world are therefore compared to find the most appropriate place for using miniature dCCPC panel as skylights. The energy saving in cooling, heating and lighting with use of dCCPC skylight panel are investigated and compared with low-E and normal double glazing. The results show that the dCCPC skylight panel can reduce cooling load by mitigating solar heat gain effectively although its performance is affected by several criteria such as sky conditions and local climates. It is generally more suitable for the locations with longer hot seasons, e.g., Log Angeles, Miami, Bangkok and Manila, in which dCCPC could provide up to 13% reduction in annual energy consumption of building. For the locations having temperate and continental climates like Beijing, Rome, Istanbul and Hong Kong, a small annual energy saving from 1% to 5% could be obtained by using dCCPC skylight panel

Daylighting characteristics and experimental validation of a novel concentrating photovoltaic/daylighting system

Daylight plays an important role on the environmental comfort level for buildings. As for the energy consumption in the building, lighting is one of the main contributors. However, traditional building integrated solar utilization systems such as flat photovoltaic or concentrating photovoltaic systems can only supply the heat or the electricity for buildings. Thus, a novel concentrating photovoltaic/daylighting window is proposed as a strategy to effectively generate the renewable electricity for the domestic use while providing a better daylight performance. The indoor experiment and ray tracing simulation are both conducted to identify the effect of the “daylighting window” on the optical performance of the concentrator. The annual daylight performance of a typical office building installed with the concentrating photovoltaic/daylighting window at various installation angles, window-to-ceiling ratios and under different climate conditions is investigated through RADIANCE. The accuracy and confidence of the simulation model is validated through the outdoor experiment, and the deviation between the experimental and simulation results is as low as 8.7%, which is indicated by the coefficient of variation of the root mean squared error. The simulation results show that the concentrating photovoltaic/daylighting window provides a good daylight performance on the working plane of the office room: the percentage of the working hours under daylight that lies in the useful range (100–2000 lx) can be up to 92.00%. It also achieves a homogenous distribution of daylight within the internal working space and effectively reduces the possibility of glare. Through the simulation results under different climate conditions, besides of the solar irradiance, the latitude also has an obvious effect on the annual daylight performance. So for the application in different latitudes, it’s highly recommended to be installed with the inclination angel near the local latitude for a higher annual electricity output and better annual daylight performance

Numerical and lab experiment study of a novel concentrating PV with uniform flux distribution

The uniform illumination profile that falls on the PV cell is good for PV output and lifespan, however the flux distribution of the concentrating PV appears to be non-uniform in most cases which is harmful for the overall performance of the concentrating photovoltaic. In order to overcome this disadvantage, a novel asymmetric compound parabolic concentrator concentrating PV with uniform flux distribution is proposed in this paper. A two-dimensional finite element model is built for electrical performance simulation of the concentrating photovoltaic module. The prototype of the concentrating photovoltaic module is manufactured and assembled to conduct the indoor lab experiment under Standard Test Condition to verify the feasibility and reliability of the model. The outdoor experiments are conducted to show the electrical performance of the concentrating photovoltaic module under the real weather condition. Then the model is used to analyze the electrical performance of the PV cell under the flux distribution created by the proposed concentrator. The results show that the electrical performance of the proposed concentrating photovoltaic module is close to that under the uniform flux distribution with the same total radiation level, which confirms that the proposed concentrator is beneficial for the PV output under concentrating illumination due to uniform flux distribution

Building integrated solar concentrating systems: A review

© 2019 Elsevier Ltd 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

Effect of non-uniform illumination and temperature distribution on concentrating solar cell: a review

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

Design and Optical Evaluation of a Novel Asymmetric Lens-Walled Compound Parabolic Concentrator (ALCPC) Integration with Building South Wall

Solar concentrating system is an effective way of combing solar energy with the building to satisfy the needs besides of electricity and hot water, also includes building heating, refrigeration, dehumidification, which require higher quality heat source. This paper put forward a novel static asymmetric lens-walled compound parabolic concentrator (ALCPC), which is composed of the mirror CPC and lens-walled structure, and can make full use of the total internal reflection and specular reflection. The optical performance of the ALCPC under the real application condition was established by software Lighttools®. Furthermore, the optimization structure by rotating the absorber away from the wall at some specific angles was also adopted for a wider scope applications. The results showed that the ALCPC has a large acceptance angle of 59° with highest optical efficiency of around 90% for most of the incident angles and has a relatively uniform flux distribution. In addition, annual performance analysis of the ALCPC was also done for Beijing (39°54’N, 116°23’E). The ALCPC as a static concentrator would be a good solution for the building south wall integration

Life-cycle assessment of a low-concentration PV module for building south wall integration in China

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