As you drive through the Andalusian countryside you may be greeted by a strange sight, a giant tower gleaming in the sun’s light surrounded by a sea of mirrors. It may seem like something out of the future but it is very much in the here and now – you would be looking at Europe’s first commercial solar power tower.
Located just outside of Seville in southern Spain it is a spectacle to see, the reflected light is so strong as to light up any dust and other particles in the air, creating the effect of glowing, tangible beams spreading from the mirrors to the tower. But it is much more than just a pretty sight.
Unlike the conventional solar photovoltaic panels that most people think of when we talk about solar power, this does not convert the sun’s rays directly into electricity via some complicated physics but instead it utilises a centuries old idea it uses a steam driven turbine to generate the electricity.
At the centre of the plant is a stylishly designed concrete tower reaching a height of 115 m (377 ft). Around this there are 624 heliostats that is a sun tracking mirror to you and me each one with a surface area of 120 square metres. That’s a total collection area of 74,880 square meters, the equivalent of 17 American Football pitches’ worth or mirrors! Throughout the day as the sun follows its trail across the sky motors at the base of the mirrors angle them such as to focus the sun’s rays directly onto a collector at the top of the tower. This heat then converts the water into steam at a temperature of 250°C. This in turn is fed into conventional steam turbines that are used to generate the environmentally friendly electricity.
Owned by Abengoa and designed by Solúcar EnergÃa the plant can generate 11MW, enough to power 6000 homes. Unlike conventional solar power though it can carry on providing power after the sun has gone down an hour’s worth can be generated by using the heat from stored steam built up during the day. Although these type of systems can not provide continuous power throughout the day they are ideally suited to supply the surplus energy required during peak hours. In hotter countries one such typical need for peak generation is where the heat often necessitates the use of air conditioning, an energy intensive process drawing most of its power during the sunniest part of the day, ideal for solar power.
At present the cost of such energy is about three times higher than conventional methods of power generation but it benefits from all the usual pros of sustainable energy once set up it has zero emissions and does not require any external fuel. And, as with all technologies, the cost should continue to drop as it develops over time.
The PS10, as the solar power tower is called, is the first of two such tower and heliostat field technology power plants, with the second, the PS20 generating a much higher 20MW using 1255 mirrors powering another 12000 homes the two of which together would displace a total of 54,000 tones of carbon dioxide each year. An important figure as an ever increasing need for countries and companies alike to keep an eye on their carbon emission comes into law.
But this is just the start for this company, not happy with the largest such generators in the world they are in the process of adding a further six power plants, each utilising a different solar technology until they reach the desired total power output. This conglomerate of eight power stations, the Sanlucar la Mayor Solar Platform, will be by far the biggest in Europe producing a staggering 302MW enough energy to power 181,200 homes!
This large scale development is important for the future, not only as a means for generating power for over a hundred thousand homes but also as a place to test several different technologies, to work out their strengths and their weaknesses in a large scale and commercial setting. And this in turn will hopefully lead to their implementation in other locations around the world.