The thermal energy storage system of Europe's first parabolic trough power plant, Andasol 1, has been successfully put into operation.

Solar Millennium stated that with the use of storage technology, a new era has begun in solar energy.

The Andasol 1 storage system absorbs part of the heat produced in the solar field during the day. The turbine produces electricity using this heat during the night, or when the sky is overcast.

"The use of the world's biggest molten salt thermal energy storage in any industrial plant to date, enables a plannable plant operation even when the sun isn't shining. The commissioning of the storage system and the turbine, along with the feeding of electricity into Spain's grid (on a test basis) will follow within the coming days," stated the company.

In a few weeks, Andasol 1 will then go into regular operation.

Andasol 1 is under construction since 2006 and will go into operation this year. The sister projects will be completed in 2009 and 2011.

At Andasol 1, the heat generated in the solar field is to be stored in a molten mixture of 60 percent sodium nitrate and 40 percent potassium nitrate.

The storage tank consists of two, 14-meter high tanks with a diameter of 36 meters and a capacity of 28,500 tons of molten salt. During the pumping process from the 'cold' to the 'hot' tank, the molten salt absorbs additional heat at an outlet temperature of approx. 280° C, thereby reaching a temperature of 380°C. A fully loaded storage system can keep the turbine in operation for 7.5 hours, which means almost 24-hour operation of the power plant in summertime. Molten salt has been used in different industrial applications for about 60 years to date, e.g. in galvanising.