Solar + Gas Hybrid Turbine
by Michael Graham Richard, Gatineau, Canada on 09. 5.05
Our friends at WorldChanging have a concise summary of a blog post by Sudarshan P. about a solar & gas hybrid turbine. The post starts out being about how solar production is still more expensive than other methods, and later on a solution is proposed: "Solar concentrators such as parabolic reflectors or fresnel lenses heat oil up to a temperature of 200C which is used to boil water to produce steam at a high pressure. The steam is super heated to temperatures of about 400C to 500C using biogas, wood gas, natural gas etc. [...] Maximum theoretical efficiency of a steam engine at 100 C is 20%. If we are able to increase the temperature of operation of the engine to say 400 C we get efficiencies of the order of 50%. [...] During bright sunlight the hybrid power station would be using 60% solar and 40% bio fuel. During the night the power would come from bio-fuel alone. But the demand during the night would be small. So less bio fuel would suffice during the night."
The gas doesn't even have to be of fossil origins; for example, biogas can be produced in great quantity with agricultural waste.
The hybrid turbine sounds like a great idea and we would really like a prototype to be made. If it works are well as predicted, we shouldn't waste any time before starting building a large number of power plants working on that principle!
The picture above is a random solar concentrator, not a solar/gas turbine. Mirrors of that type would probably be part of it if one is ever built, though.
::Profitable Solar Power, via ::WorldChanging.
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It's a clever but overly complicated solution. He want's to employ heat transfer to collect the solar energy into a central high-pressure high-efficiency steam turbine. Since the steam turbine isn't in the collector, you can use biogas when the sun goes down to keep generating power at off peak times. And a high-pressure turbine gains 10% efficiency over a stirling engine.
Problem is that moving that heat and the extra mirrors involved winds up costing you more than that the 10% you gain in a steam turbine. And that's 10% lost during peak consumption (and value), so that it can be sold latter at night when it's less valued.
And If your going to transport that heat so far from the collector you might as well just store it as heat in a sodium cloride preasurized tank (salt has a massivly higher thermal storage capacity than water, and big tanks of it can be insulated subterainian). Just release the heat on demand as the grid requires it. What is the point of biogas?
This is not exactly a new idea. Work on solar thermal power generation has going on for long time. I don't know why this idle speculation is news when there are actual advances being made, i.e the DOE's power towers which store energy in molten salts, not to mention a solar dish project which already hybridizes with natural gas or diesel.
Just do a Google search for 'solar thermal' or 'concentrating solar power'(CSP).
Some links
http://www.eere.energy.gov/solar/csp.html
http://www.volker-quaschning.de/articles/fundamentals2/index_e.html
I do want to note that 10% is on the order of 50%. :) They may want to use different wording.
But anyway, Stirling engines by SES in SoCal will probably end discussions of this technology pretty quickly.