There was a time not too long ago when concentrating solar power (CSP) technology was cheaper than solar photovoltaic systems. Back in 2006, when PV installed was $8/W to $12/W, CSP was about $6/W.
Energetic and pervasive international policies – the renewable energy standards, feed-in tariffs, net metering and other incentives – have produced a revolution in photovoltaic solar power. These policy mechanisms were designed to get volumes up and costs down, and they have succeeded.
By some estimates, approximately 67% of human use of energy for industrial applications is in the form of heat, and about one third is in the form of electrical energy. Broadly speaking, the solar sector – and the PV segment most especially – has been focusing on the electricity piece.
Solar has had very little penetration in the other 67%, except in one area – rooftop solar thermal hot water heaters.
‘We can convert sunshine into heat very effectively,’ says John O'Donnell, vice president of business development at GlassPoint Solar, a developer of CSP systems. ‘We can capture 95 percent of incoming light and turn it into heat. Depending on the geometry of our heat system, we can retain a high fraction. Systems that make steam from sunshine can capture up to 70 percent of the energy in the sunshine – not 15 percent of the energy that PV systems turn into electricity.’
That is all well and good, but CSP has been waging something of a rear-guard action against the rising tide of PV capacity. O'Donnell says the key to a successful CSP application is not to compete with PV on its home ground – electricity generation but in the realm of making heat.
‘We can deliver steam at half or one third the cost of fossil-fueled systems,’ he says. ‘At a moment where the electricity sector does not look like a good target because of what is going on with PV, maybe we can get energy to a price-point where we can open other markets that were previously closed, just by being cheaper than fossil fuel.’
In terms of application, the company looked at a wide range of industrial applications and, early on, focused on thermal-enhanced oil recovery (EOR). O'Donnell says this seems like an odd niche until you realize something about its simplicity and scale.
California today produces about 450,000 barrels of oil per day and uses about twice that. Just about half of this oil is produced with thermal EOR. Some wells stop being productive because the remaining oil is too viscous. If you heat oil, its viscosity drops. Heating it up to about 300 degrees F makes it move from being like tar or molasses to being like water.
‘You can't just heat the oil, because it is embedded in rock,’ O'Donnell says. ‘You have to heat the rock.’
The most cost-effective way that has been developed to do this is steam. In California, 15% of all the natural gas used in the state is used to make steam for this purpose. From an energy standpoint, about one third of the total energy contained in the barrel of oil you produce is used to make steam to produce that barrel.
GlassPoint is focusing its initial efforts on replacing the natural gas used in thermal EOR operations with CSP. But can CSP be made cheap enough for this to be economical?
The answer, O'Donnell says, emerged from something of a joke. The big problem with CSP is that it is outside.
‘Oh, these things would be way cheaper if they were indoors,’ he says.
There was this recognition, O'Donnell says, that there is an industry out there that delivers thousands of acres of indoor, high-sunshine environment for farmers: greenhouses. The greenhouse industry – and there is a thriving one – has been optimizing those structures for a century. There are greenhouses in Bermuda, where the wind speed is 150 mph. There are greenhouses at McMurdo Station in Antarctica, in northern Canada and every continent on Earth.
‘Those guys have been turning the crank for a century on making greenhouses lower cost, lighter, more sunshine,’ O'Donnell says. ‘Because one percent more sunshine is one percent more tomatoes.’
With an environment defined by a greenhouse, GlassPoint engineers were able to develop parabolic trough collectors that weigh 10% as much per unit area as existing designs. Instead of industrial-scale hydraulic actuators for moving the mirrors, the GlassPoint system uses 10 W stepper motors to point them.
As a result, the system – including the greenhouse – uses a little less than half as much steel per unit of sunshine collected as existing parabolic trough systems. It also requires about one third as much land as older parabolic troughs.
‘We have really cheap mirrors and expensive greenhouses, so we completely fill up the greenhouse with mirror,’ O'Donnell says. ‘With other designs, the mirrors cost a lot more, so they spread them out so they don't shade each other in the morning. But that means that at noon, only about a third of the land is covered with mirror. We cover 97 percent of the land with mirror.’
In terms of cleaning, O'Donnell says the farmers came through on that as well. The agricultural greenhouse industry is well supplied with vendors of automatic washing systems. Such a system has about 90% wash water recovery if the process is performed at night with little evaporation loss.
The addition of the greenhouse results in a CSP system that can be made less expensively than one that sits out in the open.
‘Because we're protected, I can sit right next to the nastiest coal-fired power plant or oil refinery, and I don't care because the only thing I have outside is tempered glass and anodized aluminum,’ O'Donnell says. ‘We are environmentally durable anywhere. We don't even care about sandstorms in the Middle East.’
The Sultanate of Oman, Royal Dutch Shell and a cadre of other investors recently made a $53 million equity investment in GlassPoint to develop a production scale CSP-based thermal EOR system. The company has been operating a pilot system in Oman since 2012.