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Concentrated solar power starts to shine

THE CONCENTRATED solar power (CSP) sector may not have had the momentum behind it that has driven the development of its flashier counterpart, photovoltaic solar energy (PV), in recent years, but high oil prices and a more favourable regulatory environment is starting to change this picture.

While PV generates electricity directly from solar panels, CSP – also referred to as solar-thermal energy generation – uses the somewhat less cutting-edge process of reflecting the sun's rays off an array of mirrors on to either a large central tower or a network of small tubes running across the face of the mirrors, in which water is turned into steam to drive more-or-less conventional turbines. Prototypes were built in the Mojave Desert in the 1980s, but it has taken the impetus of recent oil-price rises and calls for cuts in carbon emissions for the market to develop.

Spain is the world leader in the field, thanks largely to premium feed-in tariffs, as well as an abundance of free flat land on which to site mirror arrays. At present there is only some 450 megawatts (MW) of operational CSP capacity globally, but with a number of plants in the pipeline in both Spain and the US, the sector is poised to take off. The largest of those announced so far is a 280 MW plant using parabolic mirrors and water tubes being developed by Spain's Abengoa near Phoenix, Arizona, which is due to open in 2011.

Some 2.5 gigawatts (GW) of capacity could be operational in Spain alone by 2012 and perhaps 5-7 GW across the world by 2015, suggests Sebastian Waldburg, managing partner at SI Capital, a Barcelona-based renewables investment company. But to realise these figures, much will depend on the maintenance of an encouraging tariff framework. "As with other technologies, we need generous feed-in tariffs or other supporting mechanisms to get it off the ground," says Waldburg, whose company is an investor in Enerstar, a company developing a 50 MW CSP project in Spain's Alicante province.

At present, the pioneering status of the sector, the paucity of expertise and the high cost of equipment make CSP-generated energy a relatively expensive proposition. At best, CSP energy costs around €0.15 per kilowatt hour (kWh), compared with around €0.07/kWh for natural gas and €0.06/kWh for coal, including the costs of dealing with carbon dioxide emissions. CSP does work out a little cheaper than PV, but is nothing like as cheap as wind, which is starting to rival fossil fuels in terms of output cost.

In Spain, a feed-in tariff for CSP of €0.27/kWh, guaranteed for 25 years, is driving the expansion of the sector. Both Greece and Italy have recently introduced incentives that should encourage the sector there. California, Arizona and other southern US states are also fostering CSP.

The industry is optimistic that, given the expansion of the sector and the associated economies of scale in manufacturing and construction, the cost of solar thermal electricity can be driven down to less than €0.8/kWh over time, at which point it would start to be a genuinely viable proposition. But CSP is a technology relevant to a relatively small part of the earth and is unlikely to rival wind or even more flexible solar PV in its global reach. The need for the combination of sun, water (to cool the turbines and provide feedstock) flat land and a handy transmission network joined to a demand centre means it is ideally suited to hotter areas in, or close to industrialised centres.

Ambitious plans have been drawn up to build CSP facilities across the arid regions of North Africa and the Middle East, although those in the pipeline so far are fairly small in scale or are supplemental to a conventional power station.

Sun and land are not a problem in these regions, but the need for water and long-distance transmission infrastructure for larger schemes is. These may not be insurmountable problems. Pioneering work on dry-cooling techniques for power stations or the desalination of seawater may solve the water problem – although desalination would significantly increase fuel usage and cost. Expensive new transmission networks may also look more attractive in future, as hydrocarbons supplies dwindle or become too costly. But market observers say the moment at which large-scale renewable electricity imports to western Europe from North Africa and the Middle East will look attractive remains a long way off.

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