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Stirling engines?

  
 
Saturn's nod
11:06 / 16.07.07
Right, what's with Stirling engines? What are the stats on their efficiency and what scale of trials have been conducted? Who are the experts?

Stirling engines are solar powered generators, using a robot-controlled array of parabolic mirrors to focus sunlight onto a piston, which I think then uses the heat-expansion effect to drive a turbine. If I understand it correctly they have good efficiency.

Humanity's using I think > 50% primary productivity through photosynthesis. I don't think it's reasonable to plan on pulling through any more of that, not if we want to carry on sharing the planet with other large animals. Hence I have been thinking about other solar-energy harvesting mechanisms. Photovoltaics seems to be a bit dirty in production: need rare ores mining and refining and transporting from all over, and then they're still kindof low on efficiency and fairly fragile. Stirling engines seem to be robust and to my reading so far, promising as a power generation route: so what's happening with them? Any experts around?
 
 
Evil Scientist
11:44 / 16.07.07
The company site in the link below seems to be ready to implement them in a utility format. Although it's not something that is currently available to install in your house.

Link.

I would presume that, as the technology becomes more widespread it will start to bleed into use in a home setting. It's certainly a more efficient generator of energy than photovoltaics.
 
 
Saturn's nod
16:15 / 16.07.07
Ta, E.S..

Doesn't it look good? Makes me feel like I've seen the future: robust, efficient, quiet solar power generation.
 
 
Lagrange's Nightmare
01:59 / 17.07.07
Stirling engines are actually quite old (invented 80 years before the diesel engine) and are notable because their theoretical efficiency is the maximum possible for a thermodynamic cycle. The other most notable feature is that it is an external combustion engine (heat is transferred to engine, not within the engine) making it ideal for solar processes. The best results that have been achieved are 65-70% of the theoretical efficiency (best overall 42% but the majority operate at around 30%).

One of the main constraints of stirling engines is that they are expensive (appx $7/Watt) where using micro gas turbines have a lower efficiencey (25-33%) but only costs $1/W. If stirling engines ever reached mass production this cost would come down.

It's certainly a more efficient generator of energy than photovoltaics.

Well not really. It's certainly more efficient then silicon solar cells, but concentrating solar cells are actually quite comparable. For instance the best multi-junction cells were only 34% in 2001 and are now over 40%. Originally these high quality cells were only used for space applications but when combined into systems like this you have technology that can produce electricity at a similar if not cheaper price to stirling engine systems. (Note: these guys reckon they can do it cheaper then 'fossil' electricity, but i don't think its been verified) The downside to these systems are of course the components required to produce the cells however they have other benefits in that the cells can be easily changed and the efficiency of the pv cells has much more room to improve then stirling engines.

The problem with both of these systems is that they need a strong solar resource to be able to work well. Great for California, less so for UK...

more to come later... maybe
 
 
grant
18:56 / 27.10.08
Did Dean "Segway" Kamen just build a functional one or is he blowing hype again???

I honestly can't tell.

By the definition in that article, by the way, Stirling engines don't have to run on sunlight - any heat source would do.

I know Einstein invented a fridge that runs on heat with no moving parts. I can see, theoretically and in a very general sense, that it'd be possible to use heat to move parts, too.
 
  
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