Energy Conversion Efficiency of Various Engines

[jamesqf]

Originally Posted by Old Mechanic

Fairly sure co-generation in commercial power plants uses the turbines exhaust heat to boil water for a steam trubine.

Or other working fluid. Often a fluid with a lower boiling point is used, as in geothermal plants. Which are basically the same technology: recovering energy from a relatively low-temperature source. See e.g. Ormat Technologies Inc. | ORMAT® ENERGY CONVERTER (OEC)

[redpoint5]

Speaking of electric power plants, what prevents the use of heat pumps to generate steam power from relatively low heat sources? I know geothermal heat is used to produce power in places such as Iceland, but why can't the same principle be applied in any location? Grab heat from the air or ground > condense it until the temperature exceeds boiling > make steam > generate power. If heat pumps can achieve 300% efficiency, it seems this method of power generation should be feasible anywhere.

[serialk11r]

Originally Posted by redpoint5

Speaking of electric power plants, what prevents the use of heat pumps to generate steam power from relatively low heat sources? I know geothermal heat is used to produce power in places such as Iceland, but why can't the same principle be applied in any location? Grab heat from the air or ground > condense it until the temperature exceeds boiling > make steam > generate power. If heat pumps can achieve 300% efficiency, it seems this method of power generation should be feasible anywhere.

Er no, you never want to add another energy conversion process, it always represents a loss in efficiency.

The heat pump will consume more power than can ever be recovered from the waste heat, this is how thermodynamics works. The 300% represents the total heat moved per unit mechanical energy consumed, not the actual efficiency, otherwise it'd be a perpetual motion machine.

[Piwoslaw]

Also, heat pumps have high efficiency only when the temperature differential is relatively low. Boiling water is not where they thrive, unless the water you start with is only a few degrees below boiling.

Iceland uses geothermal energy from volcanos - pump water down into lava and get steam back. No HPs. And carrying a volcano around in your truck ain't gonna work.

[Flakbadger]

Originally Posted by Old Mechanic

The most efficient IC engine is right at 55% and it can run on basically crude oil, virtually unrefined. That engine would not work in your car, with a 3 foot bore and an 9 foot stroke running at 92 RPM.

Mech, is that the engine from that giant Maersk container ship?

[user removed]

Brake specific fuel consumption - Wikipedia, the free encyclopedia

Here are a few. To answer your question, yes one of the most efficient is used in giant container ships. Uses 285 tons of bunker fuel per day. No turbo. Sctoch yoke to eliminate side loads on piston. Engines run 24-7 for years.

regards
Mech