don't forget that thermopiles only output around 50 watts in the stable water configuration. If you were to convert it into MJ using a blulectric engine, you'd get around 1 MJ a second, around equal to a redstone engine.
EDIT: also at Antice - RP2 engines can output up to 32 MJ/t but take 1000 watts to do 1 MJ
at optimal conditions you can expect around 50W from a thermopile, 200W from a solar panel during the day, 2500 from a wind mill and 5000 from a wind turbine - though I've seen a turbine get close to 10,000 in an eternal storm mystcraft age.
EDIT: also at Antice - RP2 engines can output up to 32 MJ/t but take 1000 watts to do 1 MJ
at optimal conditions you can expect around 50W from a thermopile, 200W from a solar panel during the day, 2500 from a wind mill and 5000 from a wind turbine - though I've seen a turbine get close to 10,000 in an eternal storm mystcraft age.