(Published in the March 2011 issue of Traveller, the inflight magazine of Easyjet. Read the original here.)

Its not just the tourists who can’t get enough of southern Spain’s year-round sun. Europe’s leading energy and construction companies are keen to stake a claim in Spain’s fast growing solar thermal energy market, which has just overtaken the US to become the world’s largest.

Solar thermal energy is a relatively untapped renewable source — at least in Europe — that uses mirrors to concentrate sunlight and generate heat. This heat is then used to produce electricity using a turbine as in a conventional power station.

Mention solar power and most people think of photovoltaic (PV) panels, a quite different technology which converts light directly into electricity using silicon cells.

Thanks to generous subsidies, PV panels are a common sight on rooftops or in so-called solar farms — and not just in sunny Spain. In 2009, gloomy-skied Germany overtook Spain to become the world’s largest PV market.

But the big problem with PV panels is they produce little electricity on cloudy days — and none at all at night.

In contrast, solar thermal plants have built-in storage so they keep producing electricity when clouds block the sun and at night.

And unlike wind energy, which has grown to be Spain’s third largest power source, solar thermal plants can store energy that can not immediately be used, feeding it into the grid when needed.

That makes solar thermal energy a more flexible alternative to other renewable energy sources, even though it is currently more costly.

“The grid operators like solar thermal power far more than PV or wind power,” says Paul Coffey, chief operating officer of RWE Innogy, the renewables division of German energy giant RWE.

Utilities are warming to solar thermal plants because, both on the balance sheet and on the ground, they perform much like conventional power plants.

But the costs of building these plants are steep — around €300m for a 50MW plant.

To improve the economics, solar thermal plants need to be located in southern Europe, where the sun’s rays are hottest, and in sites where cloudy days are rare.

One such site is the Tabernas desert near Almería, an area that Sergio Leone fans will recognise as it was used to film several spaghetti Westerns.

Tabernas is home to the Plataforma Solar de Almería, a Spanish-German solar energy research facility set up in the 1980s.

Over 20,000 sq metres of mirrors are installed on its 100-acre site and there’s a huge solar furnace that would do a James Bond movie proud.

A 40-minute drive inland from Tabernas is the equally futuristic Andasol complex whose 600,000 mirrors glinting in the year-round sun.

Occupying a surface area of 1.5m sq metres — 210 football pitches — Andasol will become Europe’s largest commercial solar energy site when its third and final plant, Andasol 3, starts operating this year.

Andasol 3, in which RWE has a 25% stake, has a capacity of 50MW while the combined capacity of all three plants is 150MW.

Around 500 workers have helped construct Andasol 3 and 50 permanent jobs will be created when its turbines start spinning this year. That’s good news for the local economy as the Andalucía region has one of the highest unemployment rates in Spain.

Here’s how Andasol 3 works. More than 80km of trough-like mirrors arranged in 300 rows focus the sun’s rays onto horizontal tubes through which a special fluid circulates. The fluid heats to 400 degrees C and then passes through a heat exchanger to generate steam. As in a traditional power plant, the steam drives a turbine and generates the electricity.

If too much heat is produced, the excess is used to heat liquid salts in storage tanks. This stored heat can then be fed back into the system when it’s cloudy or at night.

“Theoretically, we can run the plant 24 hours a day during the summer,” says Frank Dinter, RWE Innogy’s head of solar power. But it will likely only run from 8am to 12pm as that is when electricity prices are highest.

This ability to program Andasol’s output like a conventional power plant is one of the key attractions of solar thermal energy.

Another is the greater efficiency of a solar thermal plant.

“On a good day, solar thermal can deliver more than double the electricity of a PV plant [of the same size]. That’s why we decided to stop developing PV plants,” says Mr Dinter.

While RWE has also looking at sites in Sicily and southern Turkey, Spain is the favoured location for thermal solar projects.

“Spain is the outstanding EU member state when it comes to promoting thermal solar power,” says Mr Coffey.

Despite its pioneering role in solar energy research, Spain’s first commercial solar thermal plant only began operating in 2006. Since then, Spain has hit the acelerador and already overtaken the US with the largest installed capacity of thermal solar power — currently 432MW produced by 11 plants.

And while the country’s deep economic crisis recently forced the government to reduce the massive subsidies previously paid to renewable energy producers, the solar thermal sector escaped lightly.

The loudest howls of protest at the cuts have come from private investors who put their money into huertas solares — solar farms that use ground-mounted PV panels. These projects were promoted as get-rich-quick schemes in local newspapers but now face tariff cuts of up to 45 percent.

The wind energy sector, one of Spain’s great success stories, has also had its wings clipped with cuts of 35 percent on the price of wind-generated electricity.

But the government spared solar thermal energy from the deepest cuts, recognising that it is much less developed and hasn’t suffered an investment bubble.

Indeed, the new law has brought clarity – and a fresh sense of urgency — to solar thermal projects still on the drawing board. That’s because the law guarantees them generous tariffs for 25 years that cannot be retroactively reduced.

By 2013, the plans predict Spain will have 60 solar thermal plants generating a combined 2,500MW of power. But to qualify for the generous tariffs and unblock investment in the sector, the government requires that, once approved, thermal solar projects need to start operating within 36 months.

The race is  now on for a place in the Spanish sun.

Europe’s Big on renewables

The largest photovoltaic solar plant operating in Europe is at Montalto di Castro, outside of Rome. The 85MW plant has been built in four phases with the last two completed in December 2010.

Surprisingly, perhaps, cloudy Germany is home to Europe’s second largest PV plant. It is at Finsterwade in the eastern state of Brandenberg and the three-phase facility has a combined capacity of 81MW.

Scotland has Europe’s largest onshore wind farm. The 140 turbines currently working at Whitelee wind farm in East Renfrewshire generate 322MW. Another 75 turbines are to be added by 2012, taking the expanded capacity to 539MW

Gwynt y Môr is Europe’s largest offshore wind farm project, although it is still under construction 18km off the North Wales coast. When completed in 2014 it will produce 580MW.

In 2020, the offshore wind prize will pass to the Dogger Bank project, which will see 9000MW of wind power installed on a sandbank 200km off the east coast of England.

By far the biggest renewable energy project conceived in Europe is Desertec, a hugely ambitious initiative to source 15% of Europe’s electricity from solar energy plants scattered across the Sahara by 2050 — the electricity would be transmitted to Europe via undersea cables. The €400bn project is still at the planning stage and needless to say, faces formidable technical and political obstacles.