Dismiss Notice
Join Physics Forums Today!
The friendliest, high quality science and math community on the planet! Everyone who loves science is here!

Anyone thought of combining solar water heater with Stirling generator?

  1. Feb 3, 2008 #1
    I've heard that solar water heating is very efficient, almost all the radiation of the sun on the panel is turned into heat.

    Also heard Stirling cycle generators (where heat flow from hot to cold is turned into mechanical motion and hence into electricity) are also quite efficient. Though by no means as efficient as solar water heaters.

    So what happens if you put the two together to produce electricity? You could use the stored hot water in the night too. It must be quite low-cost, certainly the solar panels and water tanks are mass-produced already, the cost is in the Stirling engine.

    Anyone thought about this?
  2. jcsd
  3. Feb 3, 2008 #2
    Although it isn't exactly like what you describe there are some experimental sites across the world, a couple in the Western deserts, that use the following concentrating solar arrays.


    They generally run in a vapor compression cycle (a form of a Rankine cycle), however, and use steam turbines to capture the energy and convert it to mechanical work.

    Everything I have read says that they work pretty well and are quite efficient but can only run a couple of hours after the sun has set. As far as the use of the Stirling engine I cannot comment.
  4. Feb 3, 2008 #3


    User Avatar

  5. Feb 4, 2008 #4


    User Avatar
    Science Advisor
    Gold Member

    It certainly works. You just don't get very much power out of it, due to the relatively low power/surface area ratio of incident sunlight, and the low specific power of a Sterling engine.
  6. Feb 4, 2008 #5
    Can you just remind me what specific power is? Output power per kg of mass or something?
  7. Feb 4, 2008 #6


    User Avatar
    Science Advisor
    Gold Member

    I meant power relative to physical size, but your definition is better. :smile:
  8. Feb 4, 2008 #7
  9. Feb 5, 2008 #8
  10. Feb 12, 2008 #9
  11. Feb 15, 2008 #10
    Sounds like a good idea, but here is my experience:

    My father has a stirling engine, I made an experiment with this stuff back in high school. The water was really hot, like 90°C almost. Even the striling started to move, the real turn was when the motor was exposed to direct flame. And with the loss of energy of the mechanical transmission from the stirling engine to a generator the current that could be obtained was minimal.

    I compared this result later when I was working with alarm systems using solar panels. Using a solar panel is more effective and cheaper in the long run compared to what can be obtained of the solar panel. And as you can consider using batteries you can use the obtained energy anytimne you want to. I dont know if now a more efficient stirling engine can be obtained to compare with whats available nowadays.
  12. Feb 18, 2008 #11
    Where can one acquire a large sterling engine or an engine using the same concepts (a waste heat engine)? I am interested in focusing large/many fresnel lenses and using the heat from the focused beams into electricity and work.

    Here is a cool company but I cannot seem to find out if any of their products are for sale. http://cyclonepower.com/waste_heat_engine.html
  13. Feb 18, 2008 #12


    User Avatar

    Staff: Mentor

    How 'bout a steam engine?
Know someone interested in this topic? Share this thread via Reddit, Google+, Twitter, or Facebook

Have something to add?

Similar Discussions: Anyone thought of combining solar water heater with Stirling generator?
  1. Solar Water Heater (Replies: 6)