A European consortium of companies and research groups has boosted the efficiency of silicon solar cells, proven the sustainability of solar electricity and defined clear ways to low cost.
Within the framework of CrystalClear, a large European project on the development of low-cost, highly efficient silicon solar modules, a consortium of companies and research groups has reached important milestones. Together with another European project, Topsicle, researchers increased the conversion efficiency of large-area multicrystalline silicon solar cells to a record value of 18%. In parallel, the consortium developed a process for manufacturing of extremely thin solar cells, allowing very efficient use of the high-purity silicon starting material. On large area multicrystalline silicon wafers of only 150 micrometer (0.15 mm) thickness a conversion efficiency over 16% was demonstrated, while monocrystalline silicon cells of 130 micrometer showed 17.6%. Cell processing was done using industry-compatible processes. High efficiency values are particularly important because efficiency is a key parameter to lower the manufacturing costs of solar modules. Materials and process equipment represent important cost components in the final product. Efficient cells and modules require less material per unit of electrical product power and the throughput of process equipment is effectively increased, thus contributing to cost reduction. The use of very thin silicon wafers is another effective way to reduce materials cost, especially when combined with a high efficiency.
The consortium has performed detailed cost calculations showing that the technologies now successfully under development may be produced at around 1 € per watt of module power, which is about half of today’s cost. Condition is that manufacturing is done in large volumes. The consortium has also prepared a technology roadmap that outlines all the necessary steps still to be taken to arrive at this 1 € per watt cost level. The results underline the vitality and potential for low cost of the crystalline silicon technology, which currently has a market share of over 90% and appears to be ready for the future.
Last but not least, CrystalClear has carefully analyzed the environmental impact of solar modules and complete systems as they are installed today. In contrast to a persistent misunderstanding, today’s solar electricity systems have a so-called energy payback time (the time needed to generate the energy that was consumed for manufacturing and installation) of only 2 years in Southern Europe and 3 to 3.5 years in more northern parts. Moreover, the researchers showed that there is a concrete potential for further shortening by a factor 2. This energy payback time has to be compared with a technical lifetime of 25 years or more, which means that solar electricity is highly sustainable and indeed effective to reduce CO2-emissions.
