Why concentrating on the sun promises a bright future

By Fiona Harvey, Environment Correspondent
Published: November 3 2008 02:00

In an industrial park near Israel's Negev desert, rows and rows of large glass mirrors surround a 60 metre-tall tower. At the top is a boiler, and the water inside is heated to more than 550C.
This is a test facility, but in an operational plant the superheated steam would be piped to a standard electricity generating turbine, and the power carried from there to homes and businesses.
This test plant has been built by BrightSource Energy, a US company specialising in concentrated solar thermal power.
When most people think of solar power, they think of photovoltaic panels that convert sunlight directly into electricity or trap the sun's rays to heat hot water tanks.
Concentrated solar thermal power is different. It is a way of converting the sun's energy to electricity but without using the panels. Instead, mirrors concentrate the sun's rays on to a tank of water. From then on, the process of generating power is much the same as in a conventional power plant - the steam drives a turbine that produces electricity.
An alternative to this "central receiver" method is to use "parabolic troughs", mirrors that trap the sun's rays, which heat up a transfer fluid that is then used to heat steam in a standard turbine generator.
"We are proving [with our technology] that clean energy can be generated reliably, more efficiently, and at lower cost than ever before," says John Woolard, chief executive of BrightSource.
The company, which has raised more than $160m in funding, is developing a series of concentrated solar thermal power plants in California, with the construction of the first scheduled to start next year. The company says it plans to "change the way utilities generate electricity", and in March signed agreements with PG&E to supply 900MW. BrightSource's planned plants should provide enough electricity for more than 3.2m homes.
Concentrated solar power is seen as one of the brightest spots in the renewable energy industry. After wind power, the technology is the fastest growing sector of renewables, according to Emerging Energy Research, which expects more than $20bn to be invested in the next five years.
The last year has seen a flurry of announcements. As well as BrightSource, Acciona, Abengoa Solar, FPL Energy and several others have announced new projects. Emerging Energy Research estimates that more than 5,800MW of capacity will be installed by 2012.
"This is old technology," explains Reese Tisdale, analyst at Emerging Energy Research. "It has been around for 20-plus years." Until recently, however,it was seen as little more than a curiosity. But rising energy prices, the need for security of supply and concerns over climate change have caused a resurgence of interest.
Mr Tisdale says the technology also has the advantage of being cheaper than photovoltaic energy. CSP plants can produce electricity at a cost of 20 US cents per kilowatt hour without subsidy, which compares with about 25 cents for the lowest-cost photovoltaic systems. It is still much more expensive than natural gas, at about 8 or 9 cents per kilowatt hour, but the cost is likely to come down in future as the technology gains popularity.
Some of the main centres of activity for CSP are in the south-western US and Spain, where several companies are at work on new plants. For instance, the Spanish engineering group Sener Grupo de Ingeniería recently formed a joint venture with Masdar, a vehicle funded by the Abu Dhabi government. Called Torresol Energy, the joint venture will design, build and operate concentrating solar power plants in the world's sunbelt regions, starting with three plants in Spain with an expected combined value of €800m.
As the technology requires very strong sun, it is only suitable for areas where this is plentiful. But in such areas, it has huge potential, says Mr Tisdale. Some experts have speculated that solar thermal power plants in north Africa could power much of Europe.
One drawback is that the plants do not generate power at night. However, technology called molten salts is being developed to overcome this. The salts are molten at very high temperatures and retain the heat for long periods, so they can be used to store heat during the day when the sun shines, giving it back at night to keep the turbines turning.
Ausra, which is building a plant in California, says the US could cut its emissions by 40 per cent by moving to solar thermal power and using electric cars.
"The US could nearly eliminate our dependence on coal, oil and gas for electricity and transportation, drastically slashing global warming pollution without increasing costs for energy," says David Mills, chief scientific officer and founder of Ausra. "Our daily and annual energy needs closely match the energy production potential from solar thermal power plants with heat energy storage, and our models show solar thermal power will cost less than continuing to import oil."
Copyright The Financial Times Limited 2008