How Green is your Desert?

10 January 2008

Picture a desert: baking heat, nomads on camels, burning sun, endless sand ……surmounted by arrays of polished aluminium generating massive amounts of electricity….excuse me?

 


This could be the future of power generation. The deserts of the earth receive about 700 times more energy from the sun than humanity consumes by burning fossil fuels. Using existing technology, gigantic Concentrated Solar Power (CSP) installations in these regions could generate massive amounts of environmentally-friendly electricity and transmit this power to consumers via low-loss High Voltage DC power lines. Conventional grids using AC power have high transmission losses, so cannot send electricity for long distances. It has been estimated that less than 1% of the Earth’s desert area covered in CSP arrays would generate the world’s entire demand for electricity.

Two projects have been proposed: EUMENA in the northern shores of Africa for the EU, and A Solar Grand Plan for the USA in the deserts of states like Arizona and New Mexico.

The solar arrays would be “Stirling Engine” types – a polished surface catches the sun, heats a liquid, which then goes through a heat exchanger and powers a turbine to generate electricity. This is so low-tech it can be made in a garage. The other technology is HVDC. Though this is not used much on a large scale currently, the first electric power stations devised by Thomas Edison used DC current over a hundred years ago. The HVDC power lines would take the energy to where it is needed where it would be converted to conventional AC power. Objectors may say that the power would only be available during the day, as the sun generally fails to shine at night. Electricity can be “stored” by pumping water uphill to a reservoir to be used to run a turbine when needed – “standby power”. A new technology which shows promise is the use of electricity to compress air in subterranean caverns such as old mines or empty gas or oil reservoirs. The compressed air is used to run a turbine when power is needed.

There are no technical obstacles to deploying this clean, reliable technology.

However it would be a huge, capital-intensive project. But so is nuclear power, and this technology is green, the fuel is free and available for the next few billion years, which cannot be said for uranium, which is becoming in short supply. In addition to generating electricity and running desalination plants to provide water, it would create jobs in impoverished areas of the globe for construction and maintenance technicians. Unlike large conventional power stations, if it had to be decommissioned, it could be done by grimy blokes with spanners and the components recycled. Of all the large-scale electricity projects such as nuclear, large hydro, or fossil-fuel power stations, this has the smallest environmental downside, and may even encourage horticulture in the shade of the arrays. Costs of operation are currently higher than conventional power stations, but that would reduce with the deployment of CSP on a large scale. The rocketing prices of fossil fuels will also tip the balance its in favour. The carbon footprint of the complete life-cycle of the plants would be extremely low: carbon would be emitted in the construction and maintenance of the arrays, power lines and undersea cables, access roads and control buildings but nothing like the amount that is emitted when building concrete conventional power stations (which is a huge carbon-emitting process). The operation of the CSP arrays would be zero carbon.

This is a potentially vast contribution in our battle against climate change, it uses existing, proven technology to generate electricity and would have additional benefits by bringing jobs, water and reclaimed land area to under-developed parts of the world.

www.trec.org.uk
Trans-Mediterranean Renewable Energy Cooperation

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