> But these aren't the only ways to use the field to collect solar > energy, nor is it the only way to utilize electrical energy if that's > what you have the field produce. Very true. Perhaps I should have been more generic in my description. > For example it's not clear to me at all that the best artificial way > to collect solar energy over a large field is with solar panels. At > efficiencies of 10-18%, there is a lot of room to do better. A bunch > of mirrors for concentrating the radiation and a custom designed heat > engine for the task should be able to do considerably better. The > theoretical maximum high temperature for the heat engine is the > temperature at the surface of the sun, and the low is ambient air. > The carnot efficiency should be pretty good. Even if only half of > that is actually realized, it should still beat solar cells handily. Now you have a few choices for heat engine. Stirlings have NOT caught on well have they? Could it be the pricing? Or is it that to approach high efficiencies they need working fluids that are caustic and expensive to contain? Is there a LOW cost heat engine? One that can be made from existing hardware for example? Steam engines are a possibility, but the boilers are unsafe and valving modifications can be difficult. I personally have seen a 5hp Brigs and Stratton gas engine that was modified by replacing the cam shaft to run as a steam engine. And there are other ideas.... Such as /internal/ boiler steam engines: http://www.massmind.org/techref/idea/mc-heat-inject.htm a version of this with a much more expensive injector and an external (not quite) boiler has been done using an existing (old) gasoline engine. http://www.flashsteam.com/Steam_Engine_Project.htm He ran into the effect I postulated in the first link there, but he thinks it is a bug and I think it is a feature. He calls it "Heat of Rejection" and notes that if the engine block isn't heated up, the steam expansion from his injector almost instantly condenses back on the inside of the cylinder walls. I say to heck with the preheated, high pressure injector, just heat the hell out of the cylinder and/or head and inject cold water. When it hits the air / walls / head inside the cylinder it will flash over into steam and the volume expansion will push the piston down and the crank around. > Now what can you do with that energy? A heat engine could run a > generator and then you can compare apples to apples with the solar > cells. However there may be other ways to at least partially utilize > the heat or the mechanical energy that would have turned the > generator. I don't understand all the processes, but there must be > some way to produce chemical fuel, like separating hydrogen and oxygen > from water. Carbon based fuels are more convenient to our current > infrastructure. I've always been intrigued by the idea of taking > water and grabbing CO2 out of the air to make a carbon based fuel, > like methane or methanol for example. I think the real problem is > that there is so little carbon in the air, that concentrating it will > be inefficient. Still, there is nothing theoretical against this that > I can see, and the low fraction of carbon in the air makes it > difficult but does not require it to be theoretically inefficient, > although you have to harness the energy represented in the "waste" > oxygen that will be produced. I know this is totally impractical > today, but I wonder how feasible it could be if there was a concerted > effort to make it so. Wow! Now that is interesting... Where does CO2 (as in fire extinguishers, dry ice, etc... Come from now?) Pulling it out of the air could help to reverse global warming as well, right? > I think you need to separate what is theoretically feasible from what > is practical with today's existing infrastructure. > I think in this discussion we are talking about what could be long > term, so today's infrastructure limitations aren't relevant. The cost of development is a cost, so that has to be considered as a startup cost in the system. I would love to know more about what could be done today, and is perhaps not being done because it is not considered efficient enough or is to costly to start. Then you can look for ways to get around those problems. > > ***************************************************************** > Embed Inc, embedded system specialists in Littleton Massachusetts > (978) 742-9014, http://www.embedinc.com > -- > http://www.piclist.com PIC/SX FAQ & list archive View/change your > membership options at http://mailman.mit.edu/mailman/listinfo/piclist -- http://www.piclist.com PIC/SX FAQ & list archive View/change your membership options at http://mailman.mit.edu/mailman/listinfo/piclist