Lens-walled Compound Parabolic Concentrator Research Articles

Analysis and quantification of effects of the diffuse solar irradiance on the daylighting performance of the concentrating photovoltaic/daylighting system

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.

Design and Development of a Lens-walled Compound Parabolic Concentrator-A Review

Compound parabolic concentrator (CPC) is a representative among solar concentrators, one of whose disadvantage is that the concentration ratio limits the half acceptance angle. Based on this, researchers put forward a novel structure, named the lens-walled CPC. This paper reviews the design and development of lens-walled CPC. The structure of the symmetric and asymmetric lens-walled CPC and the improved ones are presented, and their indoor and outdoor performances are also illustrated. The lens-walled CPC has a larger half acceptance angle and a more uniform flux distribution that is suitable for PV application. Furthermore, the life-cycle assessment for building integrated with PV is performed and it shows that the energy payback time of such integrated system has a significant advantage. In addition, future research areas are also indicated that may provide more functions and more stable performance. The design methods and developmental directions given in this study would provide many references in solar optical research and solar concentrator optimization.

A novel concentrating photovoltaic/daylighting control system: Optical simulation and preliminary experimental analysis

A wide range of developed and commercially available daylighting systems have been reported, however, they have just a single function, so they require an extra complex component to adjust daylighting intensity to create a better visual-comfort interior environment seasonally. Thus, in this paper, a novel concentrating photovoltaic/daylighting control system based on the lens-walled compound parabolic concentrator which is made by the transparent material is proposed. It combines both PV and daylighting control for green building design. At noon, when the incidence angle is small and the solar radiation is strong, the majority of the solar radiation can be collected by the PV cell for electricity generation and the remaining solar radiation will act as the daylighting source. In the morning or evening, when the incidence angle is large and the solar radiation is weak, the majority of the solar radiation will pass into the building for daylighting while the remaining solar radiation will be collected by the PV cell for electricity generation. An optical model was built for the ray-tracing simulation by using the commercial software Lighttools®. The prototype of the lens-walled compound parabolic concentrator was manufactured and assembled for the indoor experiment to validate the optical model. To prove the feasibility of the system, the optical and electrical performance of the proposed concentrating photovoltaic/daylighting control system are derived from the simulation and experimental results, and the actual all-day daylighting performance of it is investigated through the software simulation. The simulation and experimental results indicate good electrical and daylighting performance of the concentrating photovoltaic/daylighting control system, and the proposed concentrating photovoltaic/daylighting control system suits all kinds building rooftop designs with different inclination angles, which proves it a wide scope of application.

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

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

Optimization design and performance analysis of a novel asymmetric compound parabolic concentrator with rotation angle for building application

A novel asymmetric lens-walled compound parabolic concentrator (ALCPC) for integration with the building south wall was proposed and manufactured. Besides of the asymmetric lens-walled structure, the special rotation angle at the bottom is also introduced to optimize the performance. The electrical and optical performance of the ALCPC-PV was detailed analyzed through the experiment and ray tracing simulation. The indoor experiment was conducted by a solar simulator (Oriel Sol3A Model 90943A) from Newport Corporation at the dark environment with the temperature of 25 °C. Form the experiment results, the ALCPC increases the maximum power by a ratio of 1.74x compared to the bare cell. The decrease of the geometric concentration ratio is mainly due to manufacturing errors, mismatch losses, series resistance losses, etc. The optical performance of the ALCPC was also investigated by the software Lighttools, and the optical efficiency and the distribution percentage of the energy collected through the total internal reflection and the specular reflection at different incidence angles are identified at various incidence angles. A good agreement is observed between the experiment results and the ray tracing results. The optical efficiency at the incidence angles of 0–60° is all within 90% of its peak value which means that the proposed ALCPC can achieve 60° acceptance angle with high optical efficiency that it shows a good potential as a static concentrator for the building south wall integration.

Structure optimization and annual performance analysis of the lens-walled compound parabolic concentrator

ABSTRACTThe primary lens-walled compound parabolic concentrator (lens-walled CPC) has a significant advantage of a larger half acceptance angle as a static solar concentrator, but it also has a drawback of a low optical efficiency. In order to overcome this drawback, in this article, series of structure parameters were investigated and compared to further improve the optical efficiency within the half acceptance angle combined with the material properties. The average optical efficiencies of the improved lens-walled CPCs could achieve more than 82% within the half acceptance angle of 35ᵒ. Experiments were adopted to verify the credibility and validity of the simulation. Moreover, annual performance of the lens-walled CPCs comparison with that of the mirror CPC for Nottingham was analyzed. Results show that the improved lens-walled CPC has a higher optical performance for actual building application.

Design and investigation of a novel lens-walled compound parabolic concentrator with air gap

Stationary solar concentrators can be integrated with building façade and roof, which can reduce the area of solar cells and attain higher temperature heat resource, especially in winter for building application. In this paper, a stationary lens-walled compound parabolic concentrator (CPC) with air gap was designed and investigated to meet the application requirements. The lens-walled CPC with air gap differs from the original lens-walled CPC in that it has an air gap between the lens structure and the reflector that maximizes total internal reflection and improves optical efficiency by reducing the optical losses of the specular reflection. The simulation and experiment verified the function of the new structure, and the results indicated that the lens-walled CPC with air gap increases optical efficiency by more than 10% compared with the original lens-walled CPC. In addition, the flux distribution of the lens-walled CPC with air gap is more uniform than that of the common mirror CPC. Thus, the lens-walled CPC with air gap not only has a larger half acceptance angle and a more uniform flux distribution than the common mirror CPC but also operates at a higher optical efficiency than the original lens-walled CPC. Thus, the lens-walled CPC with air gap provides a realistic and valid solution to Building Integrated with Concentrating Photovoltaic (BICPV) as a stationary concentrator and has good prospects for several applications.

An Outdoor Experiment of a Lens-Walled Compound Parabolic Concentrator Photovoltaic Module on a Sunny Day in Nottingham

A lens-walled compound parabolic concentrator (lens-walled CPC) has a larger half acceptance angle than a mirror CPC for the same geometrical concentration ratio of 2.5X, so it would be more suitable for the building-integrated application as a stationary solar concentrator. Based on our previous work, an outdoor experimental study of a sample trough lens-walled CPC PV module under sunny condition in Nottingham is described. The experimental results provide the verification of actual larger half acceptance angle obtained by the lens-walled CPC in comparison with a mirror CPC of the same size. Along with the analysis of the projected incidence angles, the experimental results also indicate that the lens-walled CPC of 2.5X orientated east–west may be a good choice for high latitude area as a stationary solar concentrator to give a satisfactory whole year performance.

Preliminary Experimental Comparison of the Performance of a Novel Lens-Walled Compound Parabolic Concentrator (CPC) with the Conventional Mirror and Solid CPCs

A conventional mirror compound parabolic concentrator (CPC) is limited by its half acceptance angle when pursuing a large geometrical concentration ratio with no tracking. A solid CPC, which is made from solid dielectric materials without notches, can achieve a larger half acceptance angle compared with the conventional mirror CPC of the same geometrical concentration ratio, which is attributed to the optical refraction caused by the dielectric material. However, solid CPCs are heavier and costlier. This paper presents a preliminary experiment on a novel lens-walled CPC. An experimental comparison of the conventional mirror and solid CPCs and the lens-walled CPC with the same geometrical concentration ratios of 2.5 is given for different incidence angles. Here the conventional mirror CPC chose the evaporated aluminium coating as the reflection layer, for short conventional CPC. Transparent acrylic was chosen as both the dielectric material and lens material. The three CPCs were all attached to a PV cell. Through the output characteristics of the cell, the optical performances of these CPCs can be obtained. The results showed that when the incidence angle was smaller than 35°, the optical efficiency of the lens-walled CPC remained above 46.7% and was more stable against incidence angle changes compared with the conventional CPC. It also weighed and cost less than the solid CPC. Thus, lens-walled CPC adequately combines the advantages of conventional and solid CPCs, and has great potential for use in large-scale practical applications.

Experiment and simulation study on the flux distribution of lens-walled compound parabolic concentrator compared with mirror compound parabolic concentrator

Preliminary lens-walled CPC (compound parabolic concentrator) was proposed owing to its larger half acceptance angle, but in fact, it has another advantage of more uniform flux distribution than mirror CPC with the same geometrical concentration ratio. In this paper, in order to firstly evaluate the flux distribution of lens-walled CPC comprehensively, a lens-walled CPC PV (compound parabolic concentrator photovoltaic) was fabricated and tested at the different incidence angles comparison with mirror CPC PV. The experimental results showed that the FF (fill-factor) of the mirror CPC PV dropped more sharply than that of the lens-walled CPC PV, which indicated that the lens-walled CPC has a more uniform flux distribution on PV (photovoltaic). In addition, a software simulation of the flux distribution between mirror CPC and lens-walled CPC was carried out. The simulation illustrated clearly this advantage of the lens-walled CPC, which directly demonstrated the experimental inference and would be significant for lens-walled CPC application.

Comparative study on annual solar energy collection of a novel lens-walled compound parabolic concentrator (lens-walled CPC)

Abstract This study presents a comparison of a novel lens-walled compound parabolic concentrator (lens-walled CPC) with the common mirror and dielectric (e.g., acrylic or polycarbonate) solid CPCs in terms of annual solar energy collection. The comparison is conducted for the trough CPCs with a geometrical concentration ratio of 2.5, which corresponds to a nominal half acceptance angle of 23.5°. The presented lens-walled CPC has a thin lens-shape wall with mirror coating on its back surface, and the refraction of the lens can lead to a larger acceptance angle. A commercial optical analysis software PHOTOPIA is used to determine the optical efficiency of the lens-walled CPC at different incidence angles. On the basis of simulated optical efficiency, the hourly solar energy collection for various trough CPCs is then calculated according to the hourly beam and diffuse solar irradiation values in EnergyPlus weather data. In terms of monthly accumulative solar energy collection, the lens-walled CPC can achieve about 80% of the solid CPC's performance and 20–30% larger than the mirror CPC. This indicates that the lens-walled CPC may be a promising design for stationary concentrating photovoltaics application.

A Novel Lens-Walled Compound Parabolic Concentrator for Photovoltaic Applications

A compound parabolic concentrator (CPC) is a nonimaging concentrator that can concentrate solar radiation coming within its acceptance angle. A low concentration CPC photovoltaic system has the advantages of reduced Photovoltaics (PVs) cell size, increased efficiency and stationary operation. The acceptance angle of a CPC is associated with its geometrical concentration ratio, by which the size of PV cell could be reduced. Truncation is a way to increase the actual acceptance angle of a mirror CPC, but it also reduces the geometrical concentration ratio. On the other hand, a solid dielectric CPC can have a much larger acceptance angle, but it has a larger weight. To overcome these drawbacks, this study presents a novel lens-walled CPC that has a thin lens attached to the inside of a common mirror CPC or has the lens to be mirror coated on its outside surface. The shape of the lens is formed by rotating the parabolic curves of a CPC by a small degree internally around the top end points of the curves. The refraction of the lens allows the lens-walled CPC to concentrate light from wider incidence angle. The commercial optical analysis software PHOTOPIA is used to verify the principle of the presented lens-walled CPC and examine its optical performance against the common CPCs. As an example, the simulation is aimed to evaluate whether a lens-walled CPC with a geometrical concentration ratio of 4 has any advantage over a common CPC with a geometrical concentration ratio of 2.5 in terms of actual acceptance angle, optical efficiency and optical concentration ratio.

Radiance/Pmap simulation of a novel lens-walled compound parabolic concentrator (lens-walled CPC)

This study presents a Radiance/Pmap ray-tracing analysis of a lens-walled compound parabolic concentrator (lenswalled CPC), which has a thin CPC-shape lens attached to a common mirror CPC or being mirror-coated outside. The lens-walled CPC may have a larger acceptance angle than a mirror CPC and could be an alternative to a solid dielectric CPC which may be heavy and costly. The lens-walled CPC may be a promising design for buildingintegrated photovoltaics applications. The well-known ray-tracing software Radiance with its supplementary Pmap is used to verify the principle of the presented lens-walled CPC and examine its optical performance against the mirror and solid CPCs. A comparison of simulation results between Radiance/Pmap and a commercial software Photopia is also given.