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arrowConcentrated Photovoltaics


CPV Technology (as seen in the above diagram) is when sunlight is concentrated into a small area of PV cells in order to generate electricity, by using optics such as curved mirrors or lenses. (*Diagram courteousy of Green Rhino Energy)

Why Concentrated Photovoltaic instead of Non-Concentrated Photovoltaics?

CPV technology can save money on the cost of solar cells compared to Non-CPV. This is because a smaller area of photovoltaic material is needed when using CPV. A smaller area of PV can allow for CPVs to use higher-efficient solar cells.

What is required to concentrate sunlight on a small PV area?

Solar Trackers, Cooling systems and concentrating optics are needed to make a CPV system.

Types of CPV Systems

Low Concentration PV Medium Concentration PV High Concentration PV
Photovoltaic Material High Quality Silicon Multi-Junction Cells
Tracking Needed? Tracking is not necessary A 1-axis tracking is sufficient Dual axis tracking is required
Degree of Concentration 2-10 10-100 > 100
Summary Low Concentration PV (LCPV) Systems are those systems that have a solar concentration of 2-10 suns. (Suns is the measurement for Systems' solar concentration). These systems can have a high acceptance angle as the solar collector has a low concentration ratio. The cells also do not have to be actively cooled since the heat flux is low. Medium Concentration PV Systems need a solar tracking device as well as a cooling device, which can either be passive or active. High concentration photovoltaics (HCPV) use fresnel lenses or dish reflectors to concentrate sunglight. Multi-junction solar cells are preferred since they have a lower temperature coefficient and higher efficiency. These systems also require high-capacity heat sinks to manage temperature-related performance losses.

Different Types of Concentrator Technologies

Parabolic Mirrors Reflectors
In a Parabolic Mirror, the incoming parallel sunlight is reflected by the first mirror through a focal point to the second mirror. Then the second mirror reflects has the same focal point. It reflects the sunlight to the middle of the first mirror, which contains the solar cell. Reflectors are typically used in LCPV systems. These use mirrors that concentrate sunlight onto the solar cell, often made with silicon-covered material. Monocrystalline silicon is typically used in Low Concentration systems.

Fresnel Lens Luminescent Concentrators
This is a type of lense that has several sections with different angles. A large aperture (the space through which light passes) and short focal length is possible with the Fresnel Lens, all the while, maintaining a low weight. Multi-junction PV cells can be used with maximum efficiency. Light is refracted into a luminescent film and then channelled towards the PV material. The concentrator does not need any cooling since the film can be made in such a way where the wavelengths would just pass through instead of being converted by the cell.

*Images courteousy of Green Rhino Energy

Cooling Systems

Most concentration systems need a Cooling system. There are two types of Cooling Systems:

arrowActive Cooling : Cooling is done typically using a liquid metal, which can cool from 1700C to 100C.

arrowPassive Cooling : The cell is placed on a cladded ceramic substrate, having a high thermal conductivity.