Under the southern sun

When it comes to the construction of large solar power stations, the energy industry in the south of Spain is ahead of the rest. Bilfinger Berger’s expertise is essential in ensuring the efficiency of the new solar thermal plants.

(Text: Tilman Wörtz, Photos: Frank Schultze)

Driving through the dusty plains of Andalusia is like driving into another time. Everywhere you look, it would seem almost as far as the eye can see, are rows of mirrors the size of houses. They are part of solar-thermal power plants that produce electricity from solar energy.

If you look carefully, you will see they are parabolic troughs, which work by focusing the rays of the southern Spanish sun, so rarely covered by clouds, onto their focal line. Pipes containing synthetic oil run along the focal line and when heated, the thermal oil transfers its energy via a heat exchanger to a water-steam cycle, which uses a turbine to drive a power generator.

The sun heats the thermal oil to 400 degrees celsius.

Bilfinger Berger is responsible for ensuring that as little energy as possible is lost during the process of transporting the oil and steam through pipes kilometers in length. Group specialists ensure complete insulation of pipes and plant components. “With daytime temperatures of up to 40 degrees, it’s a difficult job”, says project manager Jan van Asperen, who together with his team, has already insulated five solar thermal plants in Spain.

The new Solnova power plant in Andalusia is made up of four blocks, each with an output of fifty megawatts and each solar field covering an area as big as 70 football fields. The total length of the related power networks is over ten kilometers. Each pipe must be carefully covered in glass wool and then coated in aluminum, as the thermal oil is heated to temperatures of up to 400 degrees Celsius. Thermally insulating complex plant components such as the steam cycle heat exchanger is a particularly challenging task.

The sun heats the thermal oil to 400 degrees celsius.

The quality requirements are high. The insulating material used can only be obtained from a small number of manufacturers. The wire netting used to keep the glass wool tight against the pipe is galvanized to protect against rust. “Some of our competitors save on these costs. But we want the insulation to last for decades”, explains the project manager. He knows that “in the long term, quality pays off in the form of follow-up orders.”

The first solar thermal power plants are also appearing in North Africa.

The boom in solar energy makes Spain a very promising market for Bilfinger Berger’s insulation specialists. Applications for the construction of solar-thermal power plants with a total capacity of 4,300 megawatts have been submitted to the Spanish department of energy. A third of the plants have already been approved. The increased growth in the sector is due in large part to the statutory purchase price for solar power – 25 cent per kilowatt hour over twenty years is a safe bet. The big players Acciona and Abengoa Solar continue to set the scene and are already building solar-thermal power plants in North Africa. Bilfinger Berger has been working with both energy companies for years. Abengoa Solar, working on a new plant in Algeria, has again turned to Bilfinger Berger’s specialists. Jan van Asperen is confident “Solar-thermal energy will continue to be a hot topic for us for a long time to come”.

Desertec – Power from the Sahara

The aim of the Desertec major project is to use gigantic solar-thermal power plants in the Sahara to produce power, which would be fed into longdistance pipelines. A power plant covering an area half the size of Switzerland could meet the energy needs of the entire EU. The planning company, recently formed by industry leaders, is working towards turning this plan into a reality. The technology, including that to transport the power, already exists. The task now is to create the political conditions for such a pioneering project.