Hot Engines Making Electricity?

Great Idea, It was tried with thermocouples and weighed to much, was to complex, not very efficient and was not cost effective.

If they have solved these issues great.

Add chimneys, gas hot water flues, even halogen lights to the waisted heat sources. I'm sure I missed many more. Solar ovens also.

@ 7-8% of 60% = 4.2-4.8% so of every 100Hp 4.2-4.8Hp converted to electricity.

could replace the alternator, saving a few more Hp and offsetting some weight.

But now you have surplus energy that has to be used or stored. Using it means electric motors that continually run or batteries and electric motors that equal more weight.

So replace the alternator on most cars and the real benefits in vehicles are for hybrids or fuel cell cars.

Vehicles that need or could use more electric power for other applications would benefit also.

2cents from

Brad

Could replace the alternator! Cunning....

I'm a great believer in removing bits! I remember first learning electronics tinkering with circuits and removing components to see what you could get away with.

If the heat to electricity generator only weighs the same as the alternator then it's a win win. (obviously it will need a fair amount of current to replace the alternator...)

Del

Great idea. It could be that this thermoelectric device charge the battery of the car AND run the airconditioning pump.. That will save a lot of energy.

To say the heat presently is entirely wasted is not exactly true. Heat emitted in cities (urban deserts or dust domes some say) does return a dividend in the form of lower (residential and commercial building) space heating requirements than would otherwise be the case. A reversal of the continuing "misappropriation" of arable farmland and scenic hinterland to low density residential and commercial use and infrastructure would be one way of increasing that dividend, and of also reducing the net dissipation from fleet engines...to begin with. Of course this is not something that could be appreciated, even if vaguely understood, in a place that tries to call itself a metroplex...(whatever that is, other than trying to pretend that Fote Wuth is actually just a part of Dallas; or other than some kind of "Big D metro-..." toy. ).

Efficient Green House Heat

One 3500 watts chinese diesel generator coupled to a small electric heater to produce heat and load. Air for combustion os piped in from outside thru an insulated pipe. The engine breather done the same way. 100 feet of 1.5 inches ID brass tube for exhaust heat exchange in the greenhouse another 50 of auiminium tubing for the remainder with the last 5 feet being insulated where the exhaust dischages ultimately to the outside. The air in the green house is exchanged twice per day with a hi and low intake for the exchange fan which is run by the generator. During the non-cold months the generator will be moved outside to supply fan power when or if needed. As compared to the heat bill for last winter this setup used 1/3 the money. For trucks How about using that excess heat for refridgeration in the cold shipment trailers?

Well, we can get into the high 90's with tri-generation utilised in stationary power plants. The weight and complexity added to cars would require a death spiral of larger engines to haul themselves around. The maintenance would be a nightmare.

What works at our house is that I have my wife hooked up with 30 velocity transducers in her coat and we plug her in via the cigarette lighter. Then I tell her she looks like she gained about 4 kilos while I was away . . . . . .

BTW, does anyone know where I can get a 6000 VDC car battery ? 3 phase !!

A heat engine works on delta T, between the hot side and a cold side. Whatever you put on the cold side is going to affect the delta T and reduce the performance of the heat engine. As your cold side device becomes larger, the performance reduction of the heat engine will get larger.

I don't get it! We are discussing Internal combustion engines not just stirling engines.

The water cooling on my car reduces it's performance?

If I extract heat from the exhaust system it will reduce the performance?

Where am I going wrong?

Del

Del,

Yes, the water cooling on your car greatly reduces it's performance. The cooling system is there to keep the cylinder walls from melting and the pistons from seizing. The higher the cylinder temperature, the better the performance. Note that the experimental ceramic engines that run without a cooling system have much better performance.

If you extract heat from the exhaust system you will reduce the performance. If you extract small amounts, as with something wrapped around the muffler, it will only cause a small reduction in performance. If you extract larger amounts of heat, as with a heat exchanger in the exhaust system, it will reduce performance more.

The performance of the engine depends on the heat of combustion in the cylinder moving out of the engine, to the atmosphere.

Dave

Cheers...

Lucid reply..ta

( I shall drain the water out immediately ! )

Del

Uhhhh . . . . ???

I clearly understand that substracting heat from the combustion in the engine will decrease efficiency, but not at the muffler?

The lower the temperature of exhaust gases are released to the atmosphere, the better usage of energy.

Please explain your logic.

MexSon,

You are correct that lower temperature exhaust gasses released to the atmosphere mean better energy usage. But when something is placed in the exhaust stream to extract energy, the engine no longer is releasing it's exhaust gasses directly to the atmosphere. It is now releasing exhaust to the hot side of the extraction device.

LG_DAVE

Hello LG Dave

Ok i get it if you extract heat from engine you get performance penalty , but when you are extracting heat from muffler or exhaust not exactly putting hurdle in exhaust but from outside wrapping how does this affect power output , you do decrease the heat upto certain amount before released in the environment , also after the power stroke , rapid expansion of gases drive the piston down so the crank , after that heat is radiated towards engine parts and that is shear waste , your are not cooling the engine exactly just radiating to the environment , within short run engine will be sufficiently warm to keep it optimum running , you don`t require extra and additional heat generated after that , as far as gasoline engines are concerned you too require cooler air to enter the engine to get better compression , in diesel this better

vikas,

picture the free body diagram:

the cylinder interior is Th and heat moves to Tc, where Tc= Tambient. The effieciency of the engine is a function of (Th-Tc).

If we add an accessory to extract heat from the exhaust system the accessory's hot side must be at a higher temperature than Tambient to extract useful heat energy. The cylinder now sees (Th-Taccessory).

If Taccessory=Tambient, then the engine efficiency is not reduced, but the accessory extracts no useful energy from the exhaust.

If Taccessory> Tambient, the accessory can extract energy from the exhaust, but at the expense of engine efficiency.

LG_DAVE

Ok with the formulations , but it is unclear how you loose efficiency when you are extracting heat "energy" from exhaust without restricting flow of hot exhaust gases to environment , you mean hotter the engine better the efficiency of extraction energy so difference of Tacc & T amb is achieved , if so why have radiation of heat through radiator or heat exchanger , just enclose in heat insulation ,let engine roar and you get energy from sensors , but at what cost there is friction , rolling resistance , oil drag , dumb piston crank technology that is eating away 60/70% of energy stored in fuels so you bring it to 80/ 85% inefficiency , also as stated by me earlier your equations also effect equally to fuel to energy conversion in engine , if you burn cooler gases it will expand more rapidly than hotter air so you can save little fuel by altering the fuel to air mixture but air fuel will not mix or atomize in cooler condition as with hotter one . One more point is it worth to point regarding catalytic converters placed between engine and exhaust , doesn`t that heat and restrict burnt gas flow , why cannoy such sensor placed in or around to catalytic converter , please correct me on this if i am wrong , because you are trying to explain on free body diagram , ideal conditions , not actual field conditions

Vikas,

The theoretical efficiency of the Carnot cycle in a gasoline engine is around 20%. In practice, it is closer to 16%. The cooling system does nothing but keep the engine from burning up. It is totally detrimental to efficiency. The catalytic converter does nothing but convert emissions to more benign forms. It is totally detrimental to efficiency.

LG_DAVE

our modern engines deliver 18.2-18.6% effeciency towards drive shaft that we call fuel effecient related to performance , all auto maniacs arround the world think of passing 50/60 % benchmark effeciency that seems possible , i cann`t remember exactly but some time ago HONDA had demonstrated 72% effeciency made of alluminum that came closser to Carnot effeciency but that was lab tested and not for commercialisation

But question remains unclear if you tend to cool exhaust pipe/ assembly by extracting heat without restricting the flow how do you decrease effeciency of the entire engine , how do you decrease the performance by maintaining temperature difference of engine with Tambient , thank you

vikas

If you maintain the temperature difference of the cylinder with Tambient, you won't decrease performance. Nor will you extract any heat from the exhaust.

deja vu

@<5% efficient, 0.05*0.6=.03 great we can get 3% of that wasted heat assuming the 5% device can get access to 100% of the wasted heat

http://cr4.globalspec.com/thread/10153#comment91376

http://cr4.globalspec.com/thread/10669#comment97828

http://cr4.globalspec.com/thread/8027#comment68193

and plenty more

"Thermoionic" devices on the exhaust manifold would act as a heat sink[and improve eff.] if there is a use for high amp low voltage on board.

Yes. Done that-did that-been there-tried that . If not still clasified,will be in NEW dictionarys.

When working for Motorola forty years ago some remote repeater sites were powered by a propane flame heating a stack of thermocouples wired in series to produce enough power to charge batteries, and power the repeaters. I seem to remember through forty years of fog that the product was manufactured by 3M. Same principal as "Energy from hot engines", simple, effective, but was very expensive.

Regards CEKM

Thermocouples formed into cylinders and placed around natural gas burner fire boxes are currently being used to generate electricity for remote gas processing facilities in western Canada and the US. These are equivalent to a "J" thermocouple and offer a couple of hundred milliamps from a square foot. See GLOBAL THERMAL

Cheers, PYRO