I'm guessing that their claim 90% efficiency is based on fuel efficiency - if you add up the heat output and the electrical output then divide by the BTU's in the fuel consumed you might get 90%. Lets do some math based on the data sheet for the AC unit - 1.1 m^3/hr = 38.85 ft^3/hr = 39895 BTU/hr of fuel input (= 11.7kW) 1.2 kW = 4094 BTU/hr of electrical 8.0 kW = 27296 BTU/hr of heat This gives us an efficiency of (4094 + 27296) / 39895 = 79% Or in kW (1.2 + 8.0) / 11.7 = 79% Now there is one discrepancy - they say 1.1 m^3/hr of natural gas at the 10.5kW firing rate. The highest setting is 1.2kW electrical and 8kW of heat for a total of 9.2kW. If you take 10.5/11.7 you get 90%, but the 9.2/11.7 gives us the 79% number. So - it depends on how you want to look at it. You could also look at the exhaust temperature rise and volume of exhaust and figure that as lost energy and everything else is used. But all of this assumes that you want/need 6x as much heat as electricity. It also doesn't subtract out the power used for the water pump for the cooling water or other electronics. They state the other stuff to be 110W when generating power. Subtract that from the 1.2kW. Of course most of that ends up as heat so you still get the energy in your house I guess. Anyone have a good book showing how much power a pump will use that is moving say 8 l/min and a pressure of 1500mm H20. Subtract that from your 1.2kW too. I've seen salesmen push "99% efficient" wood stoves based on the fact that the ash has only 1% of the carbon left after burning all the wood. But they didn't account for the heat going up the chimney. Dan Art wrote: > I do not belive the 90 percent efficiency claimed by them. It cannot > be that good, due to the fact that there has to be major leakage > (heat) between the hot side and the cold side of the piston. Even if > the 'block' is plastic, there will still be a major heat loss. A > burner (heat source) can be 90 percent efficient, but any moving parts > are going to shoot their claimed efficiency specs down. If the > efficiency was that good, they would be all over the place, especially > in off the grid and isolated locations. > > Heat (as a byproduct) can be used to make cold air as well-so the unit > could heat in winter and cool in summer. > > Flame suit on, fire away. > > Art > > At 04:34 PM 4/6/04, you wrote: > >> http://www.whispergen.com/ >> Trials appear to be underway but I haven'r heard much about them for >> a year >> or so. >> Richard P >> >> >> >> >> >> Do you have som epointer for more info about "Whispergen"? >> >> /Ake >> >> -----Ursprungligt meddelande----- >> Fren: pic microcontroller discussion list >> [mailto:PICLIST@MITVMA.MIT.EDU]Fvr Richard.Prosser@POWERWARE.COM >> Skickat: den 6 april 2004 22:07 >> Till: PICLIST@MITVMA.MIT.EDU >> Dmne: [OT:] Superb low temperature differential Stirling Engine >> >> >> [Topic Added] >> I think this is the philosophy behind the "Whispergen" stirling >> engines. - >> Electricity is produced as a by-product of home heating. >> RP >> >> >> >> Sorry 137 KWh a day is the correct value. >> >> -----Ursprungligt meddelande----- >> Fren: pic microcontroller discussion list >> [mailto:PICLIST@MITVMA.MIT.EDU]Fvr Ake Hedman >> Skickat: den 6 april 2004 11:02 >> Till: PICLIST@MITVMA.MIT.EDU >> Dmne: SV: SV: ] Superb low temperature differential Stirling Engine >> >> >> But if you use a higher temp difference. >> >> In my case I warm the house with pellets and say I have a stirling >> engine in a pre stage to my heater. pellets burn with a temp around 1200 >> C >> >> 1200 + 273 - 300 / 1475 = 79% 1/3 => 27% This goes to the electric >> generator. >> >> I guess the losses are in heat so it can be used it to warm the house. >> >> I use about 1000 kg of pellets a week for warming in the winter ( big >> house ). The total energy used a day is thus 1000 * 4.8kWh = 4800 KWh >> Say I have 20% efficiency for the electivity generator I can take out >> 960 KWh a day in electric energy!!! and have the rest left to warm the >> house. >> >> Do I have a fault in my thinking here? >> >> >> >> >> >> >> >> -- >> http://www.piclist.com hint: PICList Posts must start with ONE topic: >> [PIC]:,[SX]:,[AVR]: ->uP ONLY! [EE]:,[OT]: ->Other [BUY]:,[AD]: ->Ads >> >> -- >> http://www.piclist.com hint: PICList Posts must start with ONE topic: >> [PIC]:,[SX]:,[AVR]: ->uP ONLY! [EE]:,[OT]: ->Other [BUY]:,[AD]: ->Ads >> >> >> >> -- >> http://www.piclist.com hint: PICList Posts must start with ONE topic: >> [PIC]:,[SX]:,[AVR]: ->uP ONLY! [EE]:,[OT]: ->Other [BUY]:,[AD]: ->Ads > > > -- > http://www.piclist.com hint: PICList Posts must start with ONE topic: > [PIC]:,[SX]:,[AVR]: ->uP ONLY! [EE]:,[OT]: ->Other [BUY]:,[AD]: ->Ads -- http://www.piclist.com hint: PICList Posts must start with ONE topic: [PIC]:,[SX]:,[AVR]: ->uP ONLY! [EE]:,[OT]: ->Other [BUY]:,[AD]: ->Ads