'Solar could supply the world'

2012-07-27 09:24
Concentrated solar power has emerged as a renewable energy alternative. (AP)

Concentrated solar power has emerged as a renewable energy alternative. (AP)

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VIDEO: CSP explained

2012-07-23 09:16

Concentrated solar power is discussed as a viable renewable energy alternative in this YouTube video.WATCH

Cape Town - New solar plant technology may take up a lot of space, but it can easily deliver enough energy to power the world, a researcher has said.

Concentrated solar power (CSP) has emerged as a potentially efficient technology that may be able to reduce the reliance on fossil fuels for electricity generation.

"They take up space but when you actually calculate it, it's a small amount of space. One hundred by 100 miles in the Sahara would actually be enough to power the whole world. It's not total insanity," Paul Gauché senior researcher and director of the Solar Thermal Energy Research Group (Sterg) in the Department of Mechanical and Mechatronic Engineering at Stellenbosch University told News24.

While wind power and photovoltaic solar energy may be more mature technology, they have limitations in that they are intermittent, but CSP could be more reliable and efficient over the long term.

CSP uses a set of mirrors that focuses sunlight onto a single collector. The heats drives a steam turbine, similar to a traditional coal-fired power plant.


"Instead of using diesel you're concentrating sunlight and storing that in a thermal storage tank and when you need the turbines, you turn them on," Gauché said.

The technology has seen adoption in the US and Spain and Gauché said that the key development in the technology was the use of a heat storing mechanism.

"The most successful developments are these concentrating solar plants where they actually store the heat energy in salt tanks. The top of the tower actually heats salt and keeps salt molten - these are special salts - and they remain in the molten state all the time," he said.

Because solar energy is dilute in terms of energy density compared to fossil fuel, a CSP project needs a large land area with abundant sunshine to be efficient.

Water is also a challenge to the technology as it uses steam to drive turbines.

"You're dealing with at best about 1 000W per square metre of sunlight hitting the ground and the ballpark is you need about 3ha to 5ha per megawatt of electricity," said Gauché.

A typical large CSP plant produces about 250MW, implying a land area of about 1 000ha.

He said that with the CSP technology could, in the long term, be used to provide electricity for the global population, particularly because it uses a heat storing mechanism to continue delivering energy at night.


Eskom secured a $365m loan from the African Development Bank to build renewable energy plants in the Northern Cape province and the utility said that its solar plant was intended to be a serious power station rather than a demonstration plant.

"We're quite keen on solar; the cost of the technology has to come down. In general, we are keen on solar and keen to do more of it," Eskom spokesperson Hilary Joffe told News24 in 2011.

"So it's not an experimental project, it will be a real power station. A 100MW is a lot of power - it is scale - it's significant," she added.

What makes CSP a particularly attractive option is that it currently costs about R2 per kWh (Kilowatt hour) to produce energy, but this is cheaper than the high cost of gas turbines which typically cost between R3 and R5 per kWh and the cost of the young technology is expected to decline.

As some countries shut down nuclear plants in the wake of the Fukushima Daiichi disaster in Japan, renewable energy projects have come under accelerated interest.

The EU has begun to look into developing a €400bn ($774bn) network of CSP power plants based in the Sahara region known as Desertec.


Germany in May set a record for production from photovoltaic solar power at 22 gigawatts (GW) of electricity per hour which is roughly equal to 20 nuclear power stations running at full capacity.

Gauché conceded that CSP technology was young, but rejected suggestions that SA would never be able to depend on solar power to generate electricity.

"One's got to be a little bit careful about blanket statements that solar cannot do it, because that is simply not true. Solar might not be able to do it today."

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