Concentrated PV (CPV) Systems
Emre Tayyip Tan
Süeda Aksan
Concentrated photovoltaic (CPV) is a technology that maximizes the amount of energy produced from small photovoltaic parts.
What is Concentrated PV (CPV) Systems?
CPV systems are categorized according to the amount of their solar concentration, measured in "suns".
Types of Concentrators and Tracking
Low-concentration PV are systems with a solar concentration of 2-100 suns. For economic reasons, conventional or modified silicon solar cells are typically used. The heat flux is typically so low that the cells do not need to be actively cooled.
Low-concentration systems usually have a simple step-up reflector that can increase solar output by over 30% over non-concentrator PV systems.
Low Concentration PV (LCPV)
From concentrations of 100 to 300 suns, the CPV systems require two-axis solar tracking and cooling (whether passive or active), which makes them more complex.
Medium Concentration PV
High concentration photovoltaic (HCPV) systems use concentrated optics consisting of dish reflectors or fresnel lenses that concentrate sunlight at an intensity of 1,000 suns or more. Solar cells require high-capacity heat sinks to prevent thermal degradation and manage temperature-related losses in electrical performance and life expectancy.
High Concentration PV (HCPV)
All CPV systems have a solar cell and a concentrated optic. Optical sunlight concentrators for CPV present a very specific design challenge, with features that set them apart from most other optical designs. They should be efficient, suitable for mass production, capable of high concentration, insensitive to production and assembly errors, and able to provide uniform illumination of the cell. All these reasons make imagingless optics best suited for CPV. Non-imaging optics are often used for a variety of lighting applications. High transmittance glass is required to achieve high efficiency, and appropriate manufacturing process must be used to ensure shape accuracy.
For very low concentrations, the wide acceptance angles of non-imaging optics eliminate the need for active sun tracking. For medium and high concentrations, a wide acceptance angle can be viewed as a measure of how tolerant the optic is to defects in the entire system.
Optics of Concentrators
Solar Cells Materials Used in CPV Systems
A thin-film solar cell is made by depositing one or more thin layers of PV material on a supporting material such as glass, plastic, or metal. There are two main types of thin-film PV semiconductors on the market today: cadmium telluride (CdTe) and copper indium gallium diselenide (CIGS).
Efficiency, Cost, and Limitations of CPV Systems
Efficiency
Under outdoor, operating conditions, CPV module efficiencies have exceeded 33% ("one third of a sun"). System-level AC efficiencies are in the range of 25-28%. CPV installations are located in China, the United States, South Africa, Italy and Spain.
The target CPV cost to achieve the same IRR depends on the size of battery used in the CPV microgrid and is less than 2.08 $/W for all battery sizes. The maximum CPV cost of 2.08 $/W at which CPV can compete with PV is in a CPV microgrid including a 100 kWh battery.
Cost