Solar wafers set to slash energy costs
By Damon Shorter ANU engineers have perfected a manufacturing process that could halve the cost of solar cells and revolutionise the solar energy industry. It will allow the cheap production of silicon wafers - the most expensive component of solar cells. At the heart of most solar cells are slivers of silicon less than a millimetre thick. These are normally made in a complex and expensive process that wastes about 90 per cent of the raw silicon. The new technique, known as the epilift process, grows high-quality wafers for a fraction of the price, bringing solar energy closer to becoming a commercially attractive source of clean electricity. "We regard this invention as one of the most important developments in photovoltaic research of the past decade," said Dr Andrew Blakers, who heads the Photovoltaic Group in the Faculty of Engineering and Information Technology (FEIT). The epilift process was launched at the ANU yesterday by ACT Senator Margaret Reid on behalf of the Federal Minister for Science, Peter McGauran. At the launch, ANU Vice-Chancellor Deane Terrell announced a new Centre for Sustainable Energy Systems, which will incorporate the Photovoltaic and Thermochemical Research Groups from FEIT and later expand to include other ANU energy research teams. "Australia has not always been as good at promoting technological advances as it has its major scientific breakthroughs," Professor Terrell said. "But we have a striking example before us today." Until now, producing the silicon wafers was about half the cost of solar cells, Dr Blakers said. Raw silicon was first decomposed into toxic and corrosive gases before being condensed and remelted into large blocks of pure silicon. Thin slices were then sawn off, often breaking the brittle wafers in the process. The new technique - predominantly the work of PhD student Klaus Weber - grows the wafers from scratch. A silicon layer about one tenth of a millimetre thick is deposited onto a silicon template, using the same principle that causes salt crystals to grow in concentrated salt water. Once the layer has reached the appropriate thickness, it is detached from the template with acid and peeled off like a pancake, using a method developed by Dr Weber and patented earlier this year. The undamaged silicon template is reused in further growth cycles. "We believe this is the best technique for the production of solar wafers that has been developed anywhere in the world," Dr Blakers said. Wafers of varying transparencies can be made by interrupting the growth phase at different stages, raising the possibility of semi-transparent "solar windows" that could generate electricity while providing shade. The epilift process is the latest in a series of international solar breakthroughs by Dr Blakers. In 1983 he produced the first 18 per cent efficient solar cell, followed by world records of 19 per cent efficiency in 1984, 20 per cent efficiency in 1985 and 22 per cent efficiency in 1989. The Photovoltaics Group is now seeking external sponsorship to develop the project to the point of commercial feasibility. | |