Quenching the thirst of concentrated solar power
Concentrated solar power (CSP) could have the potential to energise remote areas of the world, but it faces one major obstacle – the amount of water it uses. Now, thrifty water sprinklers, tailor-made rotors and hybrid sunlight-biomass boilers could cut the water bill of concentrated solar power and even help generate electricity when the sun doesn't shine.
In CSP plants, an array of large mirrors is used to concentrate sunlight, focusing it enough to turn water into steam and drive power turbines. The turbines generate electricity much as those of fossil fuel plants, only without the fuel expenditure or the greenhouse gas emissions.
It's one of the technologies that scientists on both sides of the Mediterranean are field-testing to supply remote communities with reliable energy sources, with CSP offering particular promise for rural electrification in sun-baked regions such as sub-Saharan Africa and the Middle East.
One in seven people worldwide still has no access to electricity. Generating their power on-site could work out cheaper than extending the grid to reach them.
However, while the cost of concentrated solar is coming down, the technology still suffers from one fatal flaw: most plants consume enough water to drain an Olympic-sized swimming pool each day. Two EU projects are now rethinking water management systems to bring CSP to the arid climates where it is most needed.
Delphine Bourdon is a thermal engineer at the French Alternative Energies and Atomic Energy Commission (CEA) in Le Bourget du Lac, France. She explains that, like all heat engines, concentrated solar plants rely on a temperature gradient to convert thermal energy into motion.
'Steam needs to be as hot as possible on one end of the generator and as cold as possible on the other,' said Bourdon. 'If you just leave the power plant to heat up in the sun, its efficiency quickly drops and components start breaking down.'
Cool down
At present, operators cool CSP plants by lavishing water on them. As coordinator of the EU-funded WASCOP project, Bourdon will spend the coming three years examining new technologies to refine intelligent management methods for cooling systems.
Air ventilation will be used throughout the day to keep the working temperature as low as possible. Water-cooling will kick in at hours of peak production but in sparse sprinkles that maximise the heat absorption of each drop.
Dr Falk Mohasseb, director of research and development at Kelvion Holding GmbH, a manufacturer of industrial heat exchangers in Bochum, Germany, agrees that smart optimisation is the way forward.
He coordinates the MinWaterCSP project, which focuses on advanced cooling and mirror-cleaning technologies. The project is developing a fan shaped to match the specific airflow and static pressure demands of individual concentrated solar plants.
This could replace the generic fans commonly used today, which are not designed specifically for the plants they are installed in. According to Dr Mohasseb, MinWaterCSP's customised fans offer improved performance, with a 10 % increase in efficiency already achieved in laboratory tests.
A fan with a diameter of 7.3 metres is now to be tested on the campus of Stellenbosch University in South Africa.
Dr Mohasseb says the pitfalls to be avoided in scaling machines up to such dimensions include the mechanical constraints on materials, vibrations, and especially noise. 'If the fan is too loud, it will never find a market,' he said.
Read on on Horizon Magazine.
More information:
editorial [at] horizon [dash] magazine [dot] eu
Horizon brings you the latest news and features about thought-provoking science and innovative research projects funded by the EU. Our articles are written by independent science journalists and are designed to appeal to both scientists and non-scientists alike.
Provided by Horizon: The EU Research & Innovation Magazine
