Co-generation from Waste Heat

[Robert Haus]

Although this is not necessarily an alternate fuel thread, it is a related and often overlooked item: Cogeneration....using the waste heat from the cooling system or exhaust to improve overall efficiency of the system.

It is a pretty simple matter to add a couple of Tees and diverter valves (could even be automatic if you wish) ...then you could pipe the coolant through baseboard radiators or a heat exchanger and use it to help heat the house or domestic hot water while the generator is running.....imagine how little fuel that old Witte CD uses to begin with...now imagine not having to run the home water heater or boiler during the time the CD is providing power....there's no reason to dump all the waste heat to the outside air, especially in the winter when you could put it to good use.

Has anyone else tried this?

[PFT]

http://www.rocenergysavings.com/ener...gria/index.tpl
The above link is to the Rochester NY airport's web page about thier cogen system. It heats, cools, and powers the airport cheaper than buying electricity from the utility.
PT

[Robert Haus]

Thanks for the reply; that link didn't go to the airport, it came up with something very different...but I will do a search for the airport's system and take a look.

I know cogeneration has been done for many years in larger operations, I just can't figure out why no one has scaled the concept down to help with the efficiency of their cabin system...I know several people with remote cabins and those that run a generator are just letting the waste heat go to the air, none of them even try to recover it...It just seems so easy to reclaim some of it (who cares if it is only a partial reclamation, it is free) and yet most people don't.

Those of us in the engine hobby are in a very good position to be able to set up something like this: we have access to "junk" parts, tools, and the know-how to do it..............it could be as simple as the radiator or heater core and blower from a used car...just plumb it in to the room you want the heat...any circulation pumps/fans/etc can be run off the generator whose engine's waste heat you are recovering....then you don't have to run a separate furnace at the same time (or at least not as often)......that'll save a few bucks here and there.

[Harry]

The above link to rocenergysavings.com appears to be a domain name reserved for the purpose, but it is still in its infancy and carries general random commercial internet links.

Try this:

http://www.nyserda.org/Press_Release...3/03_03_03.asp

http://www.nyserda.org/programs/Envi...ect_update.pdf

http://www.google.com/search?hl=en&q...arch&aq=-1&oq=

[PFT]

Sorry about that, but that link used to go to the airport's page explaining the system. I copied it from my favorites list and had used it several times and it always went to the airport. I guess you just can't expect things on the web to remain constant.
Oh well, PT

[John Newman, Jr.]

Many years ago I read an article in Popular Science about a guy that ran a generator on natural gas and reclaimed the heat from the coolant, exhaust & oil to heat his house & water. Excess electric power was back-fed into the grid making his meter run backwards - Giving him a credit on his electric bill.
Being frugal & innovative are not new ideas!

[Robert Haus]

Exactly right John....I just can't figure out why more people aren't doing this...it seems too obvious to pass up.

I once had a setup to do this, I was just using the coolant, and it worked well...but I suspect an exhaust heat exchanger would have been even better......there more heat there to reclaim.

[Boatbum]

Try Googling "still engine" it was a marine engine designed in the early teens that the top of the piston was an oil engine while the bottom was steam derived from the exhaust gases. It claimed a 45% thermal efficiency!! Being a hybrid between steam and IC however it never caught on.

[CharlieBiler]

Mr. Haus,
I once worked on these co-generation systems. You normally get about three times as much out of the system as you would normally achieve with a generator alone. The normal internal internal combustion engine delivers one third of a fuel's energy out the crankshaft. The other third goes out through the radiator and the remaining third goes out the exhaust as heat.

The best system I designed used a 350 Detroit generator genset as the power system. The engine provided power to the house. The coolant was fed through the house with standard cast iron radiators. Each radiator had a standard pellet air thermostat to maintain constant temperature in each room. The exhaust was primarily used to heat domestic water and then it was run through a heat exchanger to get the last bit of energy out of the exhaust gas.

The house had a line voltage thermostat to monitor if the house was getting too cool. If the thermostat kicked in; a submerged strip heater would load down the generator and force the governor/injector pump to burn more fuel. On the coldest of nights this was needed, especially if no electrical power was being used.

The system burned no more fuel than the house normally used for heating in a furnace. The electric power was free and free domestic hot water was a welcome bonus.

In Pittsburgh there are several large scale co-generation projects that have been running for more than fifty years. People just do not notice them because the operations are a part of the local scenery. The largest private utility in America is located in the middle of the city. They burn coal, using very clean technology, and generate electricity. They then sell the steam to heat the buildings and skyscrapers in Pittsburgh. No one believes that there is a coal plant in the middle of a major city, because there is no smoke. The electric power is virtually free because the steam is needed to keep buildings warm, in the winter. In the summer they shut down.

There is one huge building here that makes all its power from natural gas. They use the waste hot water to heat the building. A huge Olympic size swimming pool is heated by the stack gas. The stack gas then is used to heat the sidewalks on that block. They save enough every year to pay for the system every two years. In the summer they also cool the building with natural gas. They use a boiled ammonia system and it is twice as efficient as any Freon based energy hog air conditioning system.

If people ripped out their gas or oil fired furnaces and installed a simple three horsepower co-generator, America's energy problem would be solved. Then half of the utilities would go bankrupt. Your taxes would also double overnight. With the reduced fuel usage the tree huggers would then have nothing to bitch about. There ain't no energy crisis. There are just a lot of greedy people that we are not bothered enough to bury. Just try and set up your own turbine windmill or hydro pump turbine. You would never get a permit.

[russcomp]

Originally Posted by John Newman, Jr.

Many years ago I read an article in Popular Science about a guy that ran a generator on natural gas and reclaimed the heat from the coolant, exhaust & oil to heat his house & water. Excess electric power was back-fed into the grid making his meter run backwards - Giving him a credit on his electric bill.
Being frugal & innovative are not new ideas!

would love to do that

[renewablejohn]

Originally Posted by Boatbum

Try Googling "still engine" it was a marine engine designed in the early teens that the top of the piston was an oil engine while the bottom was steam derived from the exhaust gases. It claimed a 45% thermal efficiency!! Being a hybrid between steam and IC however it never caught on.

We are developing a modern day equivalent using a wankel engine for both steam and woodgas.

[dkamp]

Co-Generation isn't anything new... matter of fact, it's very much old-school, just seems to be forgotten or unnoticed by most... and right under our noses. Co-gen occurs in your car... that's waste heat melting frost from the windshield.

Over in Allentown, in the Bethleham Steel Gas Blowing building... there's all sorts of co-gen going on- those engines re-burning rich exhaust ejected from the blast furnaces... capturing waste heat from the engines' cooling jackets, operating low-pressure steam turbines and equipment, then on to heating water for domestic and plant use, and finally, providing hot water heat to administrative buildings, workshops, etc... it was all about squeezing every last drop of useable energy from what was brought in.

I've got my emergency generators slated for co-gen service- once the building is in place and ready, and generators are mounted, they'll be fitted with diverters, with coolant lines going to a heat-exchanger, then a pair of lines going to the main house and workshops to 'send' the heat.

During the winter, I currently burn propane for primary heat. When commercial power goes out (and it does several times a year, for anywhere from a half-day to 4 days-or-so), I select the appropriate generator, fire it up (burns propane) and feed electricity to the house and outbuildings. When my cooling bypass/exchanger is done, I'll have the furnace set up with heat exchanger and an incoming water-temp sensor... if the incoming water temp is above a certain threshold, sensor disables the furnace's gas-valve command, hence, blower circulates heat across the heat-exchanger.

When NOT on emergency power, my heat exchanger will ALSO be contributed to by a wood-burning furnace... which will also 'leak' a certain amount of heat into the generators' engine blocks, hence, keeping them warm.

My generators aren't currently fitted, but once in place, I'll have the exhaust manifolds wrapped in insulating tape, and once up above a condensate trap, I'll have the exhaust pipe jacketed for liquid cooling, both to bring down exhaust temp (where it passes through the wall), and also to capture otherwise waste heat.

I have three water-cooled magneto-ignited generators, smallest is 5kw 4-cyl, biggest is a 30kw. I pick the unit based on load needs... 5kw for minimum fuel consumption, 30kw when I need to feed hungry loads. Of course, min and max demand vary by time of day AND season, so having three gens out there give me the ability to optimize for economy against load needs.

[russcomp]

love to see pics

[George Clark]

sounds simple enough, but I have been doing this a long time and co-gen takes a lot of engineering and planing,also takes a lot of maintenance to keep the system up to proper levels.Then do not forget about system safety and the safety of others .All heat exchangers must be isolated fron the heating and cooling media,in other words if you are heating your water you do not want ti add contaminents from engine cooling or exhaust,then you must plan your system based on thermal loads,if you do not size everything based on thermal loads you will either come up short,useually not the case, or over, normally the issue,this means your fuel efficiency will go rite in the toilet,and your costs will go up for an inefficient system,plan before you spend.

[OpposedPistone]

How about enough for the whole neighborhood?