Higher Performance and Improved Reliability: key to making photovoltaics the mainstream sustainable electricity generation source of the 21st Century

Abstract

Solar energy is a cornerstone of the future global sustainable energy system. This is recognized by the International Energy Agency (IEA) and a wide range of other public organizations, private companies and NGO's. Within the portfolio of solar energy technology options, photovoltaic conversion (PV) for electricity generation plays a special role. It is highly modular and suitable for many applications, ranging from small stand-alone systems through medium-sized integrated grid-connected systems to large power plants. Finally, recent sharp cost and price reductions have made PV competitive on retail price level in most countries which is a crucial step towards the creation of self-sustaining markets. A further reduction by a factor of 2 to 3 will make PV-electricity competitive with electricity generated by fossil fuels or nuclear power plants on wholesale price level. Such a reduction is very likely to be achieved, the main question is how soon and using which technologies. Reduction of costs and prices on the level of costs/Wp alone, however, is not sufficient for PV to reach large-scale penetration. A number of very important challenges has to be tackled in parallel. The progress of PV has been based on upscaling and innovation of the cell technology, but it is clear that the "one size fits all" approach will not be sufficient in the future anymore. It is clear that reliability and qualification of PV-modules is to be shaped according to the location in which these PV-modules will be installed. In addition, given the efficiency increase of PV-cells and modules going to 20% and more, it is quite likely that these high-efficiency devices might suffer more from degradation than in the past. In relation to the further penetration of photovoltaics, the emphasis will also shift from the performance under standard conditions of temperature and irradiation (expressed as Wp) towards energy generation (kWh) under a broad variety of conditions. The paper will outline how performance increase and reliability improvement will have to evolve concurrently to make PV a major electricity source.