solar-powered steam & stirling engines, ocean thermal energy conversion - What Else ?

i've been reading up on "how to make electricity".
a lot of interesting technologies out there.
a 7kW heated sodium solar powered steam engine pilot plant in australia
stirling energy systems, a company in arizona that's sticking a stirling engine at the focal point of large solar arrays and getting 30% efficiency.
OTEC, ocean thermal energy conversion, a system that relies on the temp. diff. between deep water & surface temps. to drive a turbine.
however this survey is a little less comprehensive than i would like it to be.
i would like to make sure i've covered everything before i build my next toy.
basically i'm looking for existing energy systems that take a heat source and output to a drive shaft for a generator.
is there a professorial type amongst us that could tell me the categories of devices that are applicable to the conversion of heat to electricity ?
thanks. i do web searches for individual categories but i have a feeling i might be missing something.
magnetohydrodynamics and nuclear fusion are a little beyond my budget.
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Some books try to categorize pumps and compressors in an orderly heirarchy but I always found that more confusing than satisfying. You get so many misc. items. The scroll compressor's family tree only has one branch.
Just as it is hard to know where to keep the tools you use in both your shop as well as your vehicle, there seems to be an infinite number of ways to categorize even a short list of stuff.
Are you generating electricity from spinning a generator?
If so one way to categorize might be to ask what turns the shaft in the engine.
1. a piston/crankshaft or
2. a turbine.
Some engines, however, have no shaft output. They only vibrate a fluid and the vibration runs a linear alternator.
In that case the categorization scheme above wouldn't be very useful.
Bret Cahill
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I'm certainly not "a professional type" but you might look at peltier devices:-) They take a temperature difference and convert it to electricity. I think they are more typically used as temperature sensors. A magazine I subscribe to did an article on using them on a coffee cup so that the coffee stirs itself. On the other hand, they are not very efficient, so they may not be what you are looking for. I ran through the numbers for a design a while back. Basically, lining streets with them as an energy source. My logic was rather than building solar panels everywhere why not use the largest black body out there, roads. I did the math for charging a car battery. And while the number of devices would fit in the length of road outside a typical house, just the cost of the devices i think was over $100,000 dollars (it required a lot of them even for ideal conditions).
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