> James and all, > > Let's be realistic. > > Set me the MINIMUM possible spec that you would find useful > and I'll see whether I can make a realistically realizable > proposal for it. > This is an *absolute minimum* spec real device, not a toy, > that would be borderline acceptable as a demonstrator that > Stirling had its place. Ok, this I can deal with... Lets make it easy for you: No need for you to justify fuel costs, let's use solar power and limit operation to when the sun is high in the sky. I'll pay for the concentration of the sunlight into several hundred 'F heat. Harbor Freight has a 40" by 60" parabolic reflector for $99. It will hit 350'F in open air. That is about 180'C or 453K. http://www.harborfreight.com/cpi/ctaf/displayitem.taf?Itemnumber=94171 If you want to bury one end of the engine in the ground for cooling, or in a pool of water, I'm sure it could be adapted to a trough type reflector. That should get you ~90F, ~30C, ~303K on the cold end or 150K delta. (450-300)/300 = ~50% I pay 8-10 cents per KWh for electricity and the only time I have a need for more than what my PV system provides is when it is hot and I'm running the AC. >From what I can see of available, useful AC units, we are looking for about 1KW while operating, or 700KWh per year to cool a few rooms. Check under "Product Spec" on these pages: http://www.sears.com/sr/javasr/product.do?pid=08066026000 or http://www.sears.com/sr/javasr/product.do?pid=04275121000 10 amps at 115V ~1000W I will buy any system that can run an AC from a few of those reflectors given the promise that it will eventually pay for itself. E.g. if it will last for 1 year and produce enough energy to turn over the pump in a standard window AC when the sun is up, I would pay $70 for it (heck, call it $100). If it will last for 5 years, I'll pay $500. If it will last 10 years, I'll pay $1000. If it fails before it pays for itself, you have to fix it; your dime. Looking over your numbers below, this offer looks iffy. I'm sure a good solar collector can get you your 50% temperatures, but 1000 watts out is 2000 watts in and that is a pretty big collector, huh? Or no? --- James Newton, massmind.org Knowledge Archiver james@massmind.org 1-619-652-0593 fax:1-208-279-8767 http://www.massmind.org Saving what YOU know. -- http://www.piclist.com PIC/SX FAQ & list archive View/change your membership options at http://mailman.mit.edu/mailman/listinfo/piclist