The success of Solar Thermal Electric technology

Protermosolar

The new energy model should be based on efficiency and majority use of renewable energies. Solar energy is the most abundant of these and using it on a massive scale for thermal and electric applications will make a significant contribution towards mitigating climate change.

Solar thermal power plants (10 and 20 MW) in operation near Seville, Spain

This replacement of energy sources is already very much underway in some countries, in particular Germany, Spain and the United States (US). Wind energy is currently playing the most pivotal role, but solar, with its different technologies (low temperature thermal, photovoltaic and thermal electric) and biomass are gaining in share. In the immediate future, a mix of all these sources will be a core element for a sustainable energy model.

Potential and advantages

Generation of electricity from fossil fuels is currently a major reason for the increase of CO₂ in the atmosphere. Solar Thermal Electric (STE) plants can address this for various reasons: the clean process involved, their special characteristics regarding dispatch-ability and grid stability (instrumental to improving distribution networks) and the abundance of the solar resource worldwide.

Each year, the Earth receives 10,000 times more energy from the sun than world energy consumption. It may be converted and consumed with STE plants on a distributed basis or transported with losses of less than 3% per 1,000 km from areas with good solar insolation rates to other consumer places.

	Storage tanks with 7.5 hours capacity for a 50 MW plant near Granada, Spain

Despite not being very well known, the first units of these power plants have been in continuous operation since the mid-1980s. They generate electricity without emitting CO₂ and meet the demand thanks to their capacity for thermal storage of energy and conversion into electricity when required. In addition, they may be easily hybridised with biomass – or natural gas – thus following the demand curve.

Development of STE technologies started in the late 1970s as a reaction from industrialised countries to the sudden increases in oil prices. By the early 1980s, when the first projects were completed, their feasibility had been proven. Some of these experimental facilities, in Spain (PSA) and in the US (Sandia), are still being used to develop and enhance systems and components.

As an immediate consequence of this work, several STE plants amounting to 354MW were built in California in the mid-1980s and are still in operation today. These plants have inspired trust from investment banks and allowed for the progress attained in recent years. Circumstances have favoured solar thermal power plants, particularly after the decree on feed-in tariffs issued in Spain in 2004.

Spain: solar world leader

Thanks to long-standing institutional support for research and development and to the technological capacity and human capital achieved over the last 30 years, Spain is the undisputed leader in solar thermal electric energy internationally, with next-generation plants amounting 300MW in operation and a further 1000MW under construction, as well as having being awarded international turnkey projects in the US, North Africa and the Middle East.

The mass-scale incorporation of these facilities in countries with good levels of direct solar irradiance will mitigate greenhouse gases in significant quantities. A capacity of 20,000MW could be installed in Spain by 2020, with a strictly solar generation of 60TWh. If used to replace coal power plants, the emission of 60Mt of CO₂ would be avoided (equivalent to 25% of greenhouse gas emissions by the Spanish electricity system). The same ratio (1Mt of CO₂ per TWh) is applicable wherever a coal power plant is substituted.

Besides the projects being developed in Spain, the US, the Middle East, Australia, China and India, there is a multinational initiative, the Mediterranean Solar Plan, underway. Its purpose is to commission a significant number of STE (among others) in Northern African countries for partial exportation of the electricity to Europe through high voltage direct current submarine cables. This would majorly contribute to development in this region as it would create a new source of wealth, reinforce the electricity systems and generate local employment. Furthermore, the new European Directive on Renewable Energies allows importation of renewable energy to accomplish the 2020 targets.

In short, this technology should be promoted with more determination and more rapidly so costs are brought down and climate change is mitigated sooner. It would also significantly reduce the levels of fossil-fuel dependency.

The overriding concern is that consumers minimise their use of energy products (fuels and electricity) and meet their basic final energy needs (heat, cold, light, sound, communications, transportation) without incurring waste and inefficiencies in the consumption processes.

Protermosolar
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