Concentrating PV Systems
Concentration of solar energy increases the illuminated flux on the photovoltaic (PV) surface thus less PV material is required. There are two ways of getting higher solar flux at the receiver: refractive optics such as using lenses and reflective optics such as optical mirrors. Several companies have successfully developed large scale reflective and refractive high concentrating systems, however, reliability and long term stability issues persist with the current technology. One innovative way to implement CPV systems in buildings is using asymmetric compound parabolic photovoltaic concentrators such as those shown in Figure 1(a). A 1kW dielectric based CPV system installed at Italy is shown in Figure 1(b). This CPV system can accept 80% diffuse sunlight in addition to the direct radiation, making it a suitable candidate for northern European climatic conditions.
High Concentrating Photovoltaics (HCPV) is currently in its embryonic stage and is exploding. The world’s highest ever solar cell efficiency of 43% creates new opportunities to reduce the cost and improve the overall efficiency of the CPV system. Such cell efficiencies mean that the collector area could be reduced up to two times with respect to conventional Silicon modules and three times with respect to thin-film modules. As the use of very high concentration decreases the cell cost contribution to just 20% of the system cost, the promise for reaching a 50% cost reduction with respect to the best flat plate PV is credible. An example of the HCPV system used for power generation in an earlier project is shown in Figure 2(a) and 2(b), which is a novel 3D hyperboloidal-ellipsoidal system developed at Heriot Watt University. Heriot Watt University is also a part of new tracking based technology that can be used for roof top application. More information can be found on ASPIS consortium.