Scaleable Solar

(3/5/2009) - The basic technology behind geothermal, solar, and wind energy production is well developed.  Wind and geothermal energy is already cost-competitive with new natural gas and sometimes coal plants (depending on circumstances).  Though solar energy isn’t quite there yet, several new developments are showing promise.  As I wrote about in December, a company called Cool Earth Solar is developing technology that they say will make solar PV cost-competitive with natural gas and possibly coal. 

Now a company named eSolar is proposing to do the same for solar thermal as Cool Earth Solar (CES) says they will do for PV.  Briefly, a solar thermal plant generates electricity by using the sun’s energy to boil water into steam, which then drives a standard turbine.  Several different designs are used to create electricity this way.  Nevada’s Solar One consists of rows of parabolic mirrors that focuses the sun’s light on pipes filled with circulating mineral oil heat transfer fluid.  The fluid transfers the heat to water, which boils and creates steam, etc. 

Another popular solar thermal design uses thousands of heliostats – flat mirrors that track the movement of the sun – to reflect light onto a center tower.  Department of Energy’s Solar Project has demonstrated the viability of this concept.  Instead of immediately heating water, the Solar Project has experimented using molten salts to store heat so that the plant can continue to make electricity when the sun goes away. 

eSolar promises to take the Solar Project’s concept and make it scaleable and affordable.  The company builds and assembles its mirrors, which are about the size of a LCD TV, in a factory.  Once they arrive at the construction site, they are simply attached to a foot high frame.  This process, says eSolar, saves a lot of money compared with other companies, which use larger mirrors that require a larger frame and more labor during instillation.

All of these small mirrors are installed close together and are positioned using computer software to create a parabola out of the entire field of mirrors.  eSolar’s use of computer software to align their mirrors is similar to CES’s use of software to inflate their solar balloons to just the right size.  In both cases, the companies are substituting computer software for precise physical placement and engineering.  In the past, labor would have been needed to position hard to construct, curved mirrors exactly right.  Each mirror would require special attention by a specialist.  Now, eSolar can develop a single piece of software and then use it in any number of locations for little additional cost. 

Although we don’t yet know eSolar’s cost of production (and eSolar declines to give out estimates, at least to the public), they have already secured several major contracts over the past few weeks – a 506 MW contract with NRG Energy, one of the largest coal-based energy producers in the United States, and a license with the Indian ACME Group to build plants capable of producing up to 1,000 MW in India – and is in the midst of building a 5 MW demonstration project in Lancaster, California. 

If the world is going to stave off global warming and develop a long-lasting network of renewable energy plants, we’re going to need to make clean electricity cheaper than natural gas and as cheap as coal, and transportation fuel (electricity or biofuels) cheaper than gasoline.  This can be accomplished two ways – make carbon-based energy more expensive or make clean energy cheaper.  At this point, it seems that we’ll need a pretty big technological breakthrough in the realm of sustainable biofuels (i.e. not corn-based ethanol) or batteries to truly threaten petroleum’s dominance. 

When it comes to the production of clean electricity, we are to the point now where the problems we currently face are largely a matter of engineering.  This doesn’t mean that transitioning from carbon-based energy to renewable energy will be easy.  Eventually, when renewable energy sources account for a large percentage of electricity production, we’ll need a breakthrough in energy storage technology to switch from more carbon-based energy sources into renewable sources without threatening to disrupt grid stability (because sunlight and wind are intermittent phenomenon that we cannot control).  In the past, engineers focused on things like converting the most energy per square foot of PV paneling, or how to make the most efficient battery, without regards to cost.  While this type of research will still be critical in the future, its important that researchers turn more of their attention to making current technologies cheaper, rather than just trying to develop high-tech wonders.