In theory, about 1 per cent of the surface of the Sahara desert would be sufficient to supply the world's entire electricity demand from clean, solar thermal power plants. In reality, solar and other renewable energy sources have some way to go before they can compete economically with fossil fuels in the medium term.

Attempts to improve the efficiency and feasibility of solar thermal power plants have been going on for some time. Since 1999, German consulting engineer Fichtner has been at the forefront of implementing solar energy projects around the world. 'We specialise in large power stations based on solar thermal technology,' says Georg Brakmann, head and co-founder of Fichtner Solar, an independent company within the Stuttgart-based Fichtner group. 'At present, we are involved in about two-thirds of all project developments for solar thermal power plants being carried out worldwide.'

The bulk of the work Fichtner Solar has been involved in so far was assigned in 2000 by the World Bank, on behalf of the Global Energy Facility (GEF). GEF promotes clean energy technologies and operates in partnership with the UN Environment Programme (UNEP) and UN Development Programme (see box).

'Several years ago the GEF allocated $200 million for distribution through the World Bank to carry out four solar thermal power plants,' says Brakmann. 'We were appointed by the World Bank to work on three of these plants.' The appointment has meant Fichtner Solar has taken on the consultancy role for the construction of three combined cycle power stations with solar thermal elements in Egypt, Morocco and India. A fourth station planned for Mexico will be carried out by a US firm.

The strategy behind the choice of locations is clear. In contrast to photovoltaic plants, which produce energy in the range of less than one watt to several megawatts, solar thermal power plants are not based on the photo effect. Instead they generate electricity by heating a medium through sunlight. The resulting steam is converted into electricity in a steam turbine, generating energy well into the megawatt range. However, Brakmann says the technology is feasible only in countries located below 40° north latitude and above 40° south, making the Middle East, North Africa, Southeast Asia and Latin America prime targets for such projects.

For cost reasons, the solar thermal units are often built in a specially designed plant known as an integrated solar combined cycle (ISCC). Typically, ISCC power stations consist of a solar field with parabolic trough collectors as well as gas and steam turbines.

The rationale behind the ISCC solution is simple. 'Integrating solar thermal into the combined cycle infrastructure is cheaper than building two separate plants,' says Brakmann. 'Instead of using a 40-MW steam turbine, a larger 70-MW turbine, for example, will be installed, which will receive the additional steam generated from the solar field.'

All three GEF-sponsored projects will be designed as ISCC power plants. 'The World Bank has chosen solar thermal technology for its projects because it considers this to be a good technology,' says Brakmann.

In Morocco, Fichtner Solar is providing full consultancy services on the implementation of an ISCC station at Ain Beni Mathar, close to the Algerian border. The plant will consist of 200,000 square metres of parabolic trough collectors and one gas turbine and one steam turbine, each with capacity of 60-70 MW.

The power station was originally planned to be developed as an independent power project (IPP). However, as in other parts of the region, there have been difficulties in attracting investors for private power schemes. As a result, the project has fallen behind schedule and might now be carried out on an engineering, procurement and construction (EPC) plus operations and maintenance (O&M) basis. Fichtner's scope of works - which originally included the development of a power purchase agreement, fuel supply agreement and form of guarantees - might therefore change accordingly.

The Kureimat solar/thermal hybrid combined cycle power station in Egypt faces similar problems. The project was also planned as an IPP, but has been thrown off track over issues relating to new exchange rate regulations affecting the power purchasing price. The private approach is now being reconsidered and the project might also be offered on an EPC/O&M basis. Fichtner Solar will be in charge of the preparation of specification and contract documents and the evaluation of bids, as well as contract negotiations.

Besides World Bank-backed projects, Fichtner Solar's regional portfolio also includes carrying out a feasibility study, backed by the German government, for a 400-MW ISCC plant at Yazd in Iran. 'Our proposal is to add gas and steam turbines and a solar field to the existing Yazd plant,' says Brakmann. However, the project has made little headway towards implementation, as raising finance has proved difficult.

The future of solar energy will largely depend on its economic feasibility. While its production has become economically more viable in recent years, it is still significantly above the cost of conventional fossil-based power generation. The cost has roughly halved since the first solar thermal plant was built, in California's Mojave desert in 1984. But at $0.12-0.14 a kWh it is still well above the $0.05 a kWh generation cost from fossil-based power plants.

'Solar thermal power is not competitive at the existing oil price level, which is why subsidies are needed,' says Brakmann. 'The World Bank considers solar thermal a good technology, which might be more expensive now, but whose cost is also likely to fall further.'

But this will only happen if solar thermal power plants are rolled out on a larger scale. Once 100 solar thermal power plants, each of about 50 MW, have been built, the cost of new facilities, equipment supply and operation should fall significantly. 'It is only a question of time before solar procedures will become cheaper,' says Brakmann. 'The more plants are built in the early stages, the more the cost will decline.'

This should in turn provide an incentive for investors, businesses and scientists to improve the existing systems and commercialise them further. The question is, where would the $5,000 million of investment, required for the first 100 plants come from? Investment in the sector has been sluggish in recent years: since the Luz plant came on stream in California 12 years ago, no new solar thermal power stations have been built. Given the challenges that lie ahead for the energy sector, the hope is that this will change.

OK