In concentrator photovoltaic (CPV) systems, sunlight is focussed using optics such as mirrors and lenses to form a point or a line. The photovoltaic (PV) cells are placed at the focus of the optics where they receive concentrated light. These systems offer several advantages over flat plate photovoltaic systems, including the replacement of costly solar cells with inexpensive optics (hence reducing overall system costs). Due to the increased concentration of light onto the cells, cells must be either passively or actively cooled to ensure optimum performance. This heat introduces the option of creating a hybrid CPV-thermal (CPV-T) system which can generate both electrical and thermal energy from a single integrated system.
The microconcentrator (MCT) system is a linear, single-axis tracking CPV-T system being developed in partnership with Chromasun Inc. The system operates at concentration ratios of up to 20X. The microconcentrator system reduces the size and weight of all components of a conventional CPV-T system, resulting in a system which is suitable for rooftop installation. In addition, hybrid receivers allow the option of producing both electrical and thermal power from a single unit. The target performance of each box is to simultaneously produce 2 kW of thermal power and 500 Wp of electrical power.
A limitation of many conventional CPV-T systems is that the desire to have the circulating fluid cool the cells conflicts with the desire to achieve a high temperature fluid. We are now working with UNSW, CSIRO, Chromasun, and NEP to develop a hybrid CPV-T system that can very efficiently deliver both 150˚C heat and solar electricity. The key technical goal of the project is to use spectral splitting to thermally decouple the solar cells from the 150˚C circulating fluid. The near infrared light where the PV cells operate most efficiently will be directed to PV cells. UV and visible light and far infrared light will be absorbed by a thermally insulated absorber. About two thirds of the solar power is in this wavelength range, allowing heating of the thermal fluid to 150 ˚C. Since the thermal and the PV absorbers are decoupled, the thermal fluid can reach high temperatures while the solar cells remain cool.
Hybrid CPV-T System Schematic