The renewable energy target passed through Parliament a few days ago. It’s disappointing, though not entirely surprising, that the Coalition amendments that got up related to more compensation for big polluters, and the grandfathering of existing coal mine gas projects into the RET. The environmentally useful proposal from the Coalition was the reservation of 25% of the RET for emerging renewable technologies like solar thermal, geothermal, wave, and biomass energy.
It’s a shame, because it seems that there are some very interesting developments happening in these areas, notably with regards to solar. Matthew Wright at Beyond Zero Emissions pointed me some exciting projects in Spain by Torresol Energy. In a nutshell, they are building plants that allow the sun’s energy to be stored, and turned into electricity when it is needed, rather than when it is available.
We’ve briefly mentioned Torresol’s Andasol 1 plant on LP before; it uses parabolic troughs to collect solar energy, oil to carry the heat back to the molten salt heat storage. But their newest plant, Gemasol, does things differently. Rather than parabolic troughs and the oil heat carrier, the under-construction Gemasol plant features a variation on the “solar tower” concept. A “mirror field” of flat, movable mirrors surrounds a high tower. The mirrors focus the sun’s radiation on the top of the tower, where the molten salt is heated. The molten salt is used directly to heat water and run a steam turbine as before.
As explained in this interview, their new plant has a couple of advantages over the older one. For one, the oil could only run at a maximum temperature of around 400 degrees Celsius. With the oil taken out of the system, the new system works at around 550 degrees Celsius; as discussed on this earlier post, increasing the temperature at which a heat engine works makes the system more efficient. The tower technology also eliminates the need to run a heap of piping, heat exchangers, and whatnot, as well as the heat exchange between the oil and the molten salt.
As the interview explains, all of these plants will hopefully produce useful power all the way through summer nights, and even in winter will supply power in the evening peak periods, unlike solar photovoltaic systems.
Andasol 1 is operating now; Gemasol will be finished in 2011 or so. And beyond that, it will take a little while for the plants to demonstrate that they meet their design levels of performance. And it still remains to be seen how much these plants will cost to build when they’re scaled up to fully commercial operation.
But a renewable energy source with cheap energy storage is like gold. While Australia doesn’t have to replicate exactly what’s been done in Spain, the abandonment of the RET reservations for renewable energy other than wind does seem a lost opportunity to try these and other such ideas, on a commercial as well as a proof-of-concept scale.