[pedalling_faster]

i'm taking a composting class. the guy who teaches it is a soil scientist whose facility processes about 350 tons a day, converting it into compost mostly.
during one of the classes i joked about throwing a tarp on top of our 8 foot wide, 6 foot high compost pile, and filling it with water. so as to create a hot tub to sit in.

the piles heat up to 130-160 degrees F.
the prof. said that some compost facilities actually run pipes through the compost wind-rows, for heating.
the process of breaking down all the materials turns out to be quite exo-thermic.
so, yes, there's opportunities for capturing waste heat all around us.

[sicophiliac]

I have had the same thought myself actually. One would think it would be relatively easy to incorporate some sort of a steam generating system into the existing cooling system thats already in a car. Could use it in hybrid applications to recharge batteries possibly.

[Gerben]

If I am not mistaken then BMW is working on a car that uses the steam to create electricity, which is then used in a hybrid drivetrain. Using heat from steam will add additional weight and volume to the vehicle. It also involves moving parts which will require regular maintenance.
Power plants can also use waste heat but this is often found not to be profitable (at historic energy prices). Think about all the diesel generators that throw away their waste heat. Only large power plants use combined steam and gas turbines. Smaller gas turbines usually also lose their heat.
I think the smaller gas turbines will be a first type of application where we will see more steam cycles added. This can be followed by static (diesel) generator sets with a lot of yearly operation hours (for instance in remote locations). Cars will be among the last where we will see this happen on a large scale.

[SolarDave]

20-30 years ago Popular Mechanics ran an article on a Freon boiler-turbine combo for long haul trucks that they called a "bottom-cycle" engine. It supposedly generated 50 HP which was combined with the normal diesel output.
While that is nothing to laugh at, there was a lot of heat available because those engines are large and running at relatively high throttle settings compared to a passenger car. I doubt a passenger car engine version of that device could capture more than 1/5 of that (basic logic - it's using 1/5 as much fuel, so there must be about 1/5 as much waste heat available).

OTOH, I recall a passenger car cruises at freeway speed on level ground at something like 15-20 HP (I think that is the actual energy required, not what the engine is required to produce) so mixing in 5-10 HP from waste heat capture seems like it would make a BIG difference.
I wonder if that PM article is available somewhere and what happened to the research. Something obviously killed it - perhaps cheap diesel? I'd say that's changed.

[Tanada]

Heat Recovery
Most of the waste heat is available in the engine exhaust and jacket water coolant (figure 2.6.1), while smaller amounts can be recovered from the lube oil cooler and the charge air after-cooler if so equipped (i.e. in turbocharged engines).
In typical engines, heat in the jacket water or coolant accounts for up to 30% of the energy input and is capable of producing 90°C to 99°C hot water. Some engines, such as those with highpressure or
ebullient cooling systems, can operate with water jacket temperatures up to 130°C.
Engine exhaust heat represents 30% to 50% of the available waste heat. Exhaust temperatures of 450°C to 650°F are typical. By recovering heat from the cooling systems and exhaust, approximately 70% to 80% of the fuel's energy can be effectively utilized to produce both power and useful thermal energy.

From pages 108-109 of PDF was the only reference I was able to find, however it is in reference to static engines, not mobile units.

If you take the hot engine coolant water and run it through an exhaust heat exchanger you can certainly get low pressure steam, run the steam through a micro-turbine to produce power and then condense it back into hot water you feed into the coolant supply for the water jacket.

[Vegas]

Hmm. It could be a cost thing. Setting up another tranny is a pain, two cranks make ya a little crazy. Steam power is alot like electric though, torque at zero revs, wide powerband. Steam engines are simple, but large. I can't imagine it would cost more than hastily stuffing batteries into a SUV, like chevy/ford.

It just seems silly to me to build hybrid ICE/EV to get 10-15% improvement. The 15hp we use to cruse down the freeway uses 50hp worth a BTU's. Figured that way, burn 10hp-per-hr worth of gas, recover 5hp-per-hr worth of heat(5hp=15% of 35hp). Thats lowballing the heat recovery, and I am already doing better than a hybrid. I think we ain't doing shit like this 'cause when fuel is(was) $1.65 a gallon, who cares how much we use. Late, late, late.

Nowhere near as neat as a carb that runs off H2O, but those guys got rounded up by the black-booters.
When the average car has an engine with peak power ten to twenty times the continous power needed, it is hard running around saying
"stop, you are using too much"
Sorry, I am ranting. I am a wrench, mechanic, welder, draftsman, machinist, problem solver. I have a difficult time thinking there are no solutions, I can fix anything, given enough time.
I guess I need to ask just what exacty has to be fixed here...

[smallpoxgirl]

If you want to reduce the waste heat from an ICE, water injection is far older and simpler than trying to build a separate steam turbine system. link
You just inject some water with the fuel. It boils during the combustion of the fuel and increases the amount of work available to turn the crankshaft.

[Tanada]

If all you want to do is add water to your fuel stream a mix of alcohol and water added to your gas tank will do the same thing, without extra equipment weight added to your car. IIRC the EPA tests show that a half gallon of water dissolved in 10 gallons of Gasohol/E-10 has significant benefits.

[max_in_wa]

... The stigma of steam? ...

In that case, how about an EXTERNAL combustion engine: Stirling Engin?
Youtube has tons of examples all the way down to tin can and balloon size. Many run just on sunlight, though to get real power, you'd need to concentrate light on one side and shade on the other. Check it out.

[Vegas]

Heh, when I was twentysomething I had a '69 dodge splitwindow van. It needed the windows painted from the inside to be a REAL scary rig, but it was close. The engine was accsessed from a dog-house inside the cabin, making it perfect for in-route cooking shinanigains.
Four pound salmon, wraped in alot of tin foil, with a flip done at highway speed.
The old overalls is better, the tinfoil tears, end up with fish that tastes like exaust fumes;)

Seriously though, I guess some airplane engines use exaust driven turbines, coupled to the main shaft. And of course turbo prop. Not discounting the water injection, heck heat the fuel before combustion=better, but it is still on the front end, a 10 point gain buys you 3 points overall-know what I mean?

External combustion has some real advantages, but ya see EV's and feul cells talked about, never steam. Stigmia of steam, nobody wants to go backwards to 1860 tech. I am not sure how well external combustion would do 'real world', IE energy return on wood products.
In addition to the three phase electric motor, tesla built a realy wicked steam turbine, weird unfanlike blades. Being the mouth-breathers we are, mankind adapted the design for sewerpumps...