Monday, October 22, 2012

Solar Power from Deserts

Enormous quantities of energy fall as sunlight on the world’s hot deserts and concentrating solar power (CSP) is a proven technology for tapping in to it. CSP is a relatively simple, mature and practical technology that, with the right political and financial impetus, can be brought into play very soon.
CSP plants in the US Deserts have been operating for more than 20 years.  Since 1984, the solar dish equipment has held the world's efficiency record for converting solar energy into grid-quality electricity. The CSP plants do not use photovoltaic cells but concentrate the sun’s heat to boil a liquid. This is used to generate electricity. Three types of plants exists.

Power Towers use a large field of sun-tracking mirrors to concentrate sunlight on to a receiver on the top of a low tower, to raise steam and thus generate electricity.
Trough Systems use parabolic trough-shaped mirrors, each one of which focuses light on to a tube containing oil or similar fluid that takes the heat to where it can be used to raise steam and generate electricity.



Dish/Engine Systems uses a large sun tracking mirror with a Stirling engine generator at its focal point to convert heat energy into electricity.
Some detailed projections prepared for the German Federal Ministry for the Environment, Nature Conservation and Nuclear Safety (BMU) show how, even allowing for increases in demand, a combination of CSP with other technologies can enable Europe to cut CO2 emissions from electricity generation by 70% by the year 2050, and phase out nuclear power at the same time
Every year, each square kilometre of hot desert receives solar energy equivalent to 1.5 million barrels of oil. Multiplying by the area of deserts world-wide, this is nearly a thousand times the entire current energy consumption of the world. At the moment, only a small area of desert will need to dedicated to CSP plants to generate enough electricity to power the world.
Are there any problems?
The first thing most people say is that the sun doesn’t shine at night. This is true, but deserts in the US, Africa and Australia all receive sun light at different times. Furthermore, techniques exist for storing the energy in melted salt or other substances. The clean electricity can also be used to produce hydrogen which can be stored.

How do we get the power from the deserts to the UK? It is feasible and economic to transmit electricity to the whole of Europe, the Middle East and North Africa using modern high-voltage DC (HVDC) transmission lines. Average transmission losses over modern high-voltage DC transmission lines (HVDC) are about 3% per 1000 km. In round figures, this means that electricity can be transmitted from North Africa to London with only about 10% loss of power. Since the fuel for CSP is free, any such loss is quite acceptable.

Other benefits
Besides generating electricity, the power plants in deserts could help the economies of Africa and other desert countries. The CSP plants can make use of the waste hot water to desalinate sea water which could have a major impact in alleviating shortages of water throughout the world, a problem that is likely to become increasingly severe with rising global temperatures
Although the area under solar collectors is in shadow, it should still receive a lot of light, quite sufficient for growing plants. Thus land that would otherwise be useless for any kind of cultivation could become very productive. An obvious problem is that plants need water and that is not plentiful in hot deserts. But desalination of sea water is another potential by-product of CSP and this may provide the fresh water that would be needed for CSP horticulture.

The potential of CSP in deserts is so huge that by 2050 the UK could be importing 70 TWh from this source. (1 TWh is enough to power 50 billion x 20 watt low energy light bulbs for an hour)

For more details contact Dr Gerry Wolff on 01248 712962 or by email at gerry@mng.org.uk
The web site can be found at: www.mng.org.uk/green_house

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