The state of the art

The most important technology for solar energy utilization in the world today is domestic and commercial water heating and pool heating, measured either in terms of the size of the industry which makes the hardware, or the total annual heat generated by the installations. Compared with local silicon cell manufacture, for example, a year's production of water heater collectors generates about 100 times more energy than a year's production of cells.

Fixed flat plate collectors have come to be accepted as simple, reliable, and cost effective heat generators for heating water up to about 75 C, which is more than adequate for domestic applications. There is constant pressure, however, to improve thermal cost effectiveness, (i.e. to increase the annual heat generated per dollar initial cost) and Australian manufacturers make extensive use of selective surfaces and low iron glass to this end. Problems have been caused by hard water and freezing temperatures, which Solarhart expects to solve with the introduction of its Black Chrome system.

Evacuated tubular collectors are not yet (1986) manufactured in Australia but the Sydney University group has interacted very closely with industry and has licensed some of the technology that it has developed to companies in Australia and overseas. These collectors can generate heat up to quite high temperatures with reasonable efficiency. Despite this it is likely that the first commercial applications will be at lower temperatures for domestic water heating, where a substantial market exists. Success in such a market would result in manufacture of large quantities of tubes. The resultant cost reductions could significantly enhance the prospect of higher temperature applications.

Direct conversion of solar energy into electricity using silicon cells is finding important applications in isolated locations where their relatively high cost can be justified. Telecom Australia has developed integrated transportable solar power packages, 13 of which were installed in 1978 between Alice Springs and Tennant Creek to provide the 130 watts needed for the 960 channel system. Since then many similar packages supplying loads up to 300 w have been installed in rural and remote Australia.

Other applications where solar cells are being used in reasonable quantities are: small scale water pumping, electric fences, small power units (less than 200 w peak rating) for lighting and electronic equipment not connected to the grid. Southern Cross manufactures solar powered pumps suitable for both borehole and surface water supplies. R&D at the University of NSW commencing in the mid 1970s concentrated on the factors which limited the maximum voltage output of silicon cells to below 0.60 volts. By 1979 the group had demonstrated the first cells with an output greater than 0.65 volts and subsequently approached 0.70 volts. During the early 1980s, this improved voltage capability was combined with reduced optical losses which maximised the current output of the cells. By 1983 the first silicon cells world-wide to exceed a conversion efficiency in excess of 18 per cent had been produced and independently measured. In 1985, a long term goal of the international photovoltaic community was reached when this work resulted in the first 20 per cent efficient silicon solar cell. In the same year, licensing arrangements were signed with BP Solar, for manufacture in Australia of high efficiency cells based on this improved technology.

Australian Academy of Technological Sciences and Engineering