Concentrated Photovoltaics (CPV)

Wed, 02/19/2014 - 15:26

IHS forecasts that concentrated PV (CPV) installations will rise to 1,362MW in 2020, increasing from 160MW in 2013. This means double-digit growth during the coming years, driven by continuing lifetime cost reductions that are increasing the competitiveness of CPV against conventional PV systems.

The use of optical systems and mirrors to focus sunlight on PV cells raises the efficiency of CPV, as well as its cost. However, the multi-junction cells that are used instead of conventional silicon PV cells are able to convert the large amounts of sunlight, generated by magnifying the illumination on the cell by up to 650 times, into electric power at high efficiency. This means that fewer solar cells are needed to generate the same amount of electricity. Panels with these CPV systems are installed on dual-axis trackers which allow them to trace the sun when it crosses the sky, resulting in a perfect alignment between the sun and the panel.

CPV systems typically have 20 power units per panel, and 36 panels per system or array mounted on a dual- axis tracker. The power units consist of a primary mirror and a smaller secondary mirror on top that concentrate the sunlight. This is consequently sent to the receiver unit within the power unit which has a tertiary non-imaging optical rod and a high-efficiency multi-junction cell. A panel of 20 power units produces 432 watts of rated power, which amounts to 15.6kWp DC rated power on an array of 36 panels. Where traditional PV systems have efficiency levels of around 19%, CPV panels are already reaching 25% and can get up to 40% efficiency, or 42% in a laboratory setting. There still is a lot of room for innovation and improvement, as 50 % efficiency is achievable in the future, industry specialists believe. The efficiency curve shows a very steep improvement over little time, with a range increase of 5% over three years, compared to 1% for the same period in the case of silicon PV.