Solar Concentrators: what are the different technologies?

Solar concentrators are devices that work on the basic principle of focusing on the sun. Discover different solar concentrator technologies, including Fresnel lenses, parabolic mirrors, reflectors, and Luminescent concentrators.

How Do Solar Energy Concentrators Work?

Solar concentrators are devices that work on the basic principle of focusing on the sun. Generally, intense sunlight results in higher temperatures, which increases the rate at which heat can be efficiently converted into electricity. To intensify sunlight, solar energy concentrators that bundle the sun into one focal point are used.

Operation of Solar Energy Concentrators

Solar energy concentrators operate on the principle of focusing a bundle of sunlight onto a small surface usually with the help of an optical device or a mirror. For the concentration technology to be efficient, the concentrator has to be directly facing the sun. As such, there is a need for the concentrators to follow the sun, with the help of a tracker, to ensure they catch maximum irradiance during the day.

Solar concentrator tracking

Tracking can be a single axis from East to West to cater for the daily movement of the sun across the sky, and a dual-axis from East to West and from North to South to exactly track the changing path of the sun. Since solar energy concentrators only work with direct sunlight, they are limited to clear sunny locations.

Advantages solar concentrators

Using concentrated photovoltaic (CPV) technology in a solar system can have several advantages over regular Si Mono- / poly crystalline and thin film technologies:

• Less solar cell material is required to capture the same or even more amount of radiation as a non-concentrating energy system:
  • High efficiency multi-junction cells are more expensive than standard Si solar cells, however, due to sunlight concentration, they require only a small cell surface.
• The entire system can be cost effective due to fewer cell materials, low cost optics, and increased output.

Types of Solar Energy Concentrators

Fresnel Lens

The Fresnel lens is named after the designer French Physicist Augustin-Jean Fresnel. This front of the lens is not smooth but has a rough surface sections angled differently to increase concentration while bringing weight and thickness to a minimum. Fresnel lenses can either be circular, providing a point focus with high concentration power, or cylindrical providing a line focus with reduced concentration power.

Parabolic mirrors

The concentration setup with parabolic mirrors requires two mirrors; a collector and a concentrator. The first mirror (collector) reflects the incoming rays of sunlight to a focal point in the second (concentrator) mirror, which is smaller. The concentrator then directs the sun rays into the middle of the reflector mirror where the solar cell is located. This configuration does not require optical lenses.

Reflectors

Concentrator reflectors are straight mirrors with silicone-covered metal that are angled to capture sunlight rays. To prevent reflection losses, the mirrors are used in pairs. The angle of inclination depends on the latitude of the installation.

Luminescent concentrators

Luminescent concentrators refract light in a luminescent film and then channel it to a solar cell. They do not require mirrors and optical lenses and can concentrate diffuse light. This concentrator technology does not need tracking.