CHP = Combined Heating & Power...

[AC_Hacker]

Originally Posted by NiHaoMike

I think 2 strokes are less efficient than 4 strokes.

Probably true.

Do you know of any other cheap water cooled engine in this size power range?

-AC_Hacker

[Piwoslaw]

Originally Posted by NiHaoMike

I think 2 strokes are less efficient than 4 strokes.

I heard somewhere that the opposite is true, but that may depend on quite a few parameters. But if what we want is more heat than power then a "less efficient" engine would be just the thing, right?

[NiHaoMike]

Originally Posted by Piwoslaw

I heard somewhere that the opposite is true, but that may depend on quite a few parameters. But if what we want is more heat than power then a "less efficient" engine would be just the thing, right?

If you need more heat, use the excess power to run a heat pump. If the combined heat output is greater than the energy content in the fuel, it would essentially be a furnace with an effective efficiency above 100%.

[AC_Hacker]

Originally Posted by Piwoslaw

I heard somewhere that the opposite is true, but that may depend on quite a few parameters. But if what we want is more heat than power then a "less efficient" engine would be just the thing, right?

Well, possibly so, but consider that electricity is considered a 'higher quality' energy than heat, since it is easy to get nearly 100% efficiency when converting from electricity to heat, but it is very difficult to get much past 85% to 90% efficiency when converting from heat to electricity, 15% to 30% being common.

But you are right in that the 'wasted' heat energy would mostly be utilized.

However, if the inefficiency is due to fuel that is not totally combusted, it's a different matter.

-AC_Hacker

[AC_Hacker]

Originally Posted by NiHaoMike

...use the excess power to run a heat pump... it would essentially be a furnace with an effective efficiency above 100%.

Makes it a very attractive option doesn't it!

-AC_Hacker

There are many applications for waste heat recovery that do not involve power generation. The waste heat is used instead for systems such as absorption refrigeration, water evaporation or other processes that utilize low level heat energy.