What are Concentrating Photovoltaics?
Concentrating photovoltaics (CPV) is used to describe systems that combine photovoltaic (PV) cells with an optical component that concentrates light. The optical components, which are also called optical concentrators, are designed to harvest sunlight from a wide area and focus it directly onto a small area covered by PV cells. This increases the intensity of the light reaching the PV cells, which in turn increases the amount of power the cells can produce.
There are two main types of concentrating optical systems, refractive types that use lenses and reflective types that use mirrors. Refractive types include Fresnel lenses, refractive prisms, luminescent plastic or glass and compound parabolic concentrators. Reflective types include parabolic troughs, dishes, v-groove mirrors.
Another way in which concentration of light can be applied to PV is through a luminescent solar concentrator. A sheet of plastic luminescent material traps solar radiation over a large area and directs it to the materials edges where there are thin strips of PV material.
CPV systems can be designed to magnify sunlight at different ratios; three classes exist:
- low concentration, where the magnification ratio is less than 10X
- medium concentration, between 10X and 100X
- high concentration, where the ratio lies above 100X but is usually less than 1000X
What are the advantages of Concentrating Photovoltaics?
CPV systems can be used to reduce the overall cost of power generation. Concentrating optics increase the intensity of sunlight per unit area which means less PV material is required to produce the same amount of electricity. Since the materials required for the optical systems, such as glass or plastic, are cheaper than PV materials the cost of the system can be lowered compared to analogous non-concentrating PV systems.
What are the challenges for Concentrating Photovoltaics?
If the concentrating optics do not focus light uniformly across the PV cells, the efficiency of the cells is reduced. Their efficiency also drops with increased temperature so dissipating heat from the PV cells is important. Most CPV systems that have been developed only concentrate direct sunlight so many of them employ mechanical systems that allow them to track the sun through-out the day. These systems can be prone to long-term reliability issues. Additionally, CPV systems that are only suitable for use with direct sunlight are not very suitable for Northerly climates which experience more diffuse light conditions.
Please click on the links below to learn more about concentrating photovoltaics and the work being carried out by SISER researchers.