Apr 2 2009
Recently, a metamorphic triple-junction solar cell of the Fraunhofer Institute for Solar Energy Systems achieved a record efficiency of 41.1% at 454 suns. Making multi-junction CPV cells the most efficient photovoltaic devices.
The importance of this high capacity to convert sunlight into electricity is magnified by the fact that multi-junction cell efficiency tends to increase with the concentration factor. This is because the performance of multi-junction cells is particularly resilient to increases in cell temperature. The only photovoltaic tecnology with a better temperature coefficient is a-Si thin film but this technology has a much lower efficiency. Currently, the useful range of concentration ranges from 2 to 1,000 suns. However, as methods of cooling cells are improved and new materials are employed in building multi-junction the concentration factor could be increased to take full advantage of high efficiency cells.
The report further explains factors which affect the efficiency of CPV cells. It also discusses in detail materials employed in CPV cells. Currently, two types of cells are being used in concentration systems: high efficiency silicon cells and multi-junction cells. At present, multi-junction cells have not achieved the same level of marketing development and industrialisation as those made of silicon.
CPV Today shared that its prediction is based on an analysis of the state of the art, on the historical evolution of systems and on the objectives depicted by manufacturers as well as on the analysis of the public institutions involved in the promotion of technology.
"Commercial cells will reach efficiency levels up to 45%, modules up to 35% and systems up to 30%, which will imply a substantial reduction of costs," according to an extract from the report.
The report also elaborates on historical efficiencies of CPV cells and forecast for efficiency improvement.