QUESTIONS ABOUT CSP

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Questions are often asked about possible problems with CSP. The mains ones are listed here, with some answers.

How do CSP plants cope with sandstorms?

It seems that sandstorms are not all that frequent but that may vary from one desert to another. On the Sahara Wind website (www.saharawind.com) it says "According to our measurement recordings, sandstorms are fairly rare in occurrence. Winds blowing eastward from the desert account for less than 5 % of the normal wind regime. Sandstorms make only one part of this 5%."

With the parabolic trough type of system, it seems that the operators simply turn the mirrors upside down during a sandstorm. Other CSP systems may also protect the mirrors in a similar way. If the CSP plant is a hybrid (with gas firing as a backup) or if it has heat storage, then electricity generation may continue during the sandstorm.

What is the energy return on energy invested (EROEI)?

How long does it take for a CSP plant to recover the energy that was needed to create the equipment and install the plant?

Evert du Marchie (p 10) gives an energy payback time for the Fresnel mirror type of CSP plant as 6.7 months.

SCHOTT AG (p 13) suggests that the energy payback time for a parabolic trough type of CSP plant is about 5 months.

Could there be shortages of materials to construct CSP plants?

Generally speaking, CSP plants are constructed from materials that are plentiful and relatively cheap: steel, glass, concrete, aluminium and the like. At present, most of these are made using 'dirty' technologies that release CO₂ into the atmosphere but since they are so widely used in the world, it will be necessary to find new ways of making them, or good substitutes for them, that do not pollute the atmosphere.

Assuming the world continues to use at least as much electricity as now, the world's entire fleet of power plants needs to be replaced every 30 or 40 years anyway. To a large extent, materials like steel can be recycled from the old obsolete power plants to make the new clean power plants that we need now. Also, we need to ask whether CSP plants need more or less materials for their construction than other types of power plants that would be needed instead. Taking account of the complete power-generation cycle, it seems likely that CSP plants would require less materials than traditional alternatives. Although CSP plants need solar collectors, they do not need any of the relatively large infrastructure that is needed for the mining, processing and transportation of fuels such as coal or uranium.

Some figures given by Evert du Marchie (p 10) suggest that, if all of the world demand for electricity were to be met using CSP plants, then it would take about three years at current rates of production to make all the necessary steel. Although this scenario is conceivable, it is likely that CSP would always be one amongst several renewable sources of electricity, that construction of the necessary plants would be spread over a much longer period, and that ways will be found for constructing CSP plants without so much steel.

"Earth's natural wealth: an audit" is an interesting article from the New Scientist about the earth's mineral resources and how long they may last.

Environmental impacts

From at least as far back as Walt Disney’s The Living Desert, wildlife films have made us aware that deserts have their own vibrant ecology. If the world’s deserts were all to be covered with CSP plants, there would indeed be cause for concern about the animals and plants that live there. But less than 1% of the world’s deserts would meet current world demands for electricity and even in pessimistic scenarios, it seems unlikely that more than 5% would be needed in the future. It should be possible for CSP plants and wildlife to co-exist.

In a similar way, it seems likely that CSP plants would have a minimal impact on the lives of people that live in deserts. Indeed, by providing employment, electricity, water, shading from strong sunlight, and opportunities for horticulture (see CSP bonuses), any impacts may be more positive than otherwise.

Sustainable development

A possible objection to the DESERTEC concept is that it is simply another fix for the humankind junkie with its addiction to perpetual growth and the trashing of the planet.

Without any other policies in place, the DESERTEC concept could indeed provide an excuse for continued expansion of the human population with continually-increasing demands on the biological and material resources of the planet.

Alternatively, the DESERTEC concept can and should have an important role to play in the development and implementation of worldwide policies for truly sustainable living, introducing sensible policies to stabilise and then bring down the size of the human population, and bringing our demands on the planet into line with what it can provide without compromising the future (see Jeffrey Sachs, Common Wealth: Economics for a Crowded Planet, Allen Lane, 2008).

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