Solar Power

We would all love a Spanish holiday right? My family thought so when we had the opportunity to make the most of a trip to Europe. Spain is sunny and warm, the people are friendly and there’s history to boot. But, as an engineer I had some additional plans. Spain is one of the leaders in solar energy technologies with several different style of plant in operation. Before our travel my wife was mildly interested and my two young children had little idea what we would see. When we arrived we were all in awe of this simple and efficient technology.

There are three main types of solar energy collection is use in Spain; PV (Photovoltaic like the panels on your roof), parabolic trough and solar power towers.

Our first visit was the Olmedilla PV park located part way between Valencia and Madrid. This park contains 270,000 panels and is rated at 60MW. It produces 87,500 MWh annually. The park lines the low undulating hills of the area and was surprisingly unobtrusive. It is visible from only a few sections of the main road and is better seen by driving around the small access roads patrolled by a lone security vehicle.

Our second visit near Granada in the South of Spain included both the Andasol parabolic trough and Abengoa solar towers PS10 and PS20. Both of these systems use reflectors to focus the sunlight onto a collector.

In the case of the parabolic trough, this collector is a steel tube filled with a temperature stable synthetic oil. The oil is heated to around 400° C and is pumped through a heat exchanger where it boils water to drive a turbine. The hot oil continues through the system to storage tanks filled with potassium, sodium and nitrate salts. The salts are heated during the day from the excess heat and then transfers the heat back to the oil at night or during rainy periods when it is not being heated by the sun. The Andasol parabolic trough site is made up of three plants, Andasol 1, 2 and 3 and can store enough heat in the salt mix to continue producing full power for 7.5 hours. The three plants combined are rated at 150MW and produces about 180,000 MWh annually.

The solar towers PS10 and PS20 use sun tracking reflectors to direct sunlight to a collector at the top of a central 115m high tower. At the collector, water is heated directly to produce steam with one hour of power storage achieved by holding pressurised superheated water in a storage tank. PS10 is rated at 11MW and the improved PS20 rated at 20MW.  Together they produce about 71,000MWh annually.

The towers could be seen from some distance away and really looked spectacular with the concentration of sunlight illuminating water vapour and dust in the air to create beams of light.

We continued on to visit a third site near Seville called Gemasolar. It is a site adopting a full 360° arc of reflectors focusing the sunlight to a central tower 140m tall. Gemasolar adopts similar molten salt technology to the Andasol parabolic trough plant however it pumps the salt mix directly to the heat exchanger in the tower and then through the storage tanks before being used to produce steam. The plant is rated at 120MW with 15 hours of salt storage and produces 110,000MWh annually.

This site really must be seen to be appreciated. The crisp clean look of the plant and that magnificent collector standing in the middle was well worth the detour to see the site.

So why don’t we see these plants in Australia? This is a question I have been asked by everyone I have shown our happy snaps to. I think the answer is that we will see them. It is only a matter of time before pressure is put on our aging and polluting coal power stations to invest in new infrastructure and there is no argument that for a new power station, solar thermal plants would be chosen over coal. All you need is a water supply and sun… and we have plenty of sun (just as much as Spain).

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