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November 2004

Article

 

Novel invention could mean cheaper source of energy from solar power

Energy security has become one of the hottest political topics in the last few years with the prospects of skyrocketing oil prices and shortages. Along with the looming dangers of climate change, the urgency of alternatives to CO2 emitting energy sources is becoming more obvious by the day. One of the most important actions to counter these challenges is the establishment of alternative energy sources such as solar energy. Latest research by South African scientists have taken us one step further to realising these goals.

Solar power

Solar power has traditionally been differentiated into solar thermal and solar photovoltaic (or PV for short) systems. The photo-voltaic effect is a phenomenon that depends on quantum physics, and allows specific materials to directly convert solar radiation to electricity. The photo-voltaic effect is used in solar panels, that have been powering spacecraft for decades and have recently been making their presence felt in supplying electricity to free-standing locations on earth, like telephone towers and pump systems on farms. 

However, the panels available commercially today are almost all based on high-purity silicon as the photo-voltaic material, and these panels are much more expensive than the equivalent amount of coal, petrol or gas.

The only way to make photovoltaic energy more widely used, is to make devices (including solar panels) that are much cheaper than the current silicon-based devices. The most promising PV material identified to date is Copper-Indium-Gallium-Diselenide (CIGS).

CIGS is much more efficient than silicon at converting incident sunlight into an electric current: Less than one micron of CIGS absorbs more than 99% of available incident solar energy, compared to 350 microns of silicon to do the same job.

Despite the excitement around CIGS, significant cost savings compared to silicon were not achieved, despite 20 years of research. However, a new development has made the picture considerably brighter. 

Cost-saving CIGS solar panels

Prof Vivian Alberts of the Department of Physics at the Rand Afrikaans University in South Africa and team have developed and patented a novel manufacturing technique that finally makes it possible to construct CIGS solar panels at a very low cost. The method is easily upscalable to industrial output levels, while remaining much cheaper to produce than conventional silicon solar panels.

Work done over the last two years indicates that panels can be produced in commercial volumes at a cost of about R 500 for a 50 Watt panel. This is much cheaper than existing solar panels available on the market. CIGS is a remarkably stable material and conversion efficiencies should be sustainable for 15-20 years in any given panel.

RAU physicists are currently collaborating with physicists from the University of Port Elizabeth and the University of Pretoria to make 20 Watt CIGS panels, thanks to an award by the Innovation Fund in the national Department of Science and Technology during 2003. The award, in the amount of R 13,2 million, has been used to construct a pilot assembly facility on the RAU campus (with more than R 2 million of top-up funds added by RAU management).

The two main components of the facility are a state-of-the-art sputtering instrument and a state-of-the-art diffusion oven. The former was designed by Leybold Optics of Dresden, Germany, and the latter by Wilro Technologies in the Netherlands. Both these instruments were designed according to Prof Alberts' unique and novel specifications and are, at the moment, the only examples of their kind in the world. They also constitute the best combination of instruments of this kind in the world at present.

Benefits

This patented technology has caused great excitement across a broad front of stakeholders, since it promises to bring the practical cost of applying solar photovoltaic systems for electricity production down to a level comparable to coal-fired or nuclear technologies.

Furthermore, the technology contributes nothing to carbon dioxide emissions and consumes only the resources used to manufacture the solar panels (the metals copper, indium and gallium and the non-metal selenium). These materials could in principle all be recycled into new panels at the end of the useful lifetime of a panel, since no material whatsoever is consumed. The finite lifetime (15-20 years) of a panel is simply due to deterioration of the crystal structure over time.

The energy used to make a panel is recovered within 1-2 years of operation, beyond which a further 13-18 years of net energy production remain. There is no vulnerability to disruptions in fuel supply, since sunlight is the fuel consumed.

In addition, solar photovoltaic technology can be produced in any desired amount, from a few milliwatts to many megawatts, if so desired. It is not necessary to erect large power stations to serve a community with energy from this technology. 

A typical middle-class suburban family needs only about 30 square metres (about the size of a living room) of solar panels to supply all of its electricity needs. 

The technology also holds great promise for socio-economic development, especially in the rural areas of Southern Africa. - RAU


More information:

The pilot production facility was officially opened by the South African national minister of Science and Technology, Mr Mosibudi Mangena, on 9 November 2004.

Related articles:

Nigeria: Warming up to solar energy

Solar cookers for Africa

Energising Africa

 

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