Wasted heat

[BrokenTrack]

The other day we lost our power, but the kids did not even notice because I hooked up my PTO Generator to my Tractor, and made power that way. But as I checked on my tractor, the engine and generator were pretty warm after running for 18 hours...not dangerously hot, but warm.

Well my home is radiant floor heated, utilizing the two loop system with metering valve on a PLC. It is pretty simple but efficient, mostly because as long as the main boiler loop is between 100-212 degrees, I have a warm home. I built my heating system this way so that no matter what I want to heat with, propane, coal, firewood, solar, geothermal, compost heat, etc, it can heat my home.

So it got me to thinking, I have a couple of liquid cooled diesel engines kicking around, what happens if I put one of these engines on my PTO Generator and then plumbed the cooling lines to be circulated through my main boiler loop? I could conceivable produce enough power to power my home, and heat my house at the same time. This would be no different then a spit swapper on a tractor, and they obviously work.

In doing the math, it would seem to be expensive at first, me saving myself about $3800 in costs for heat and electricity, but consuming about $5400 in fuel. BUT...my generator produces 20 KW no matter what my house consumes, so with net-metering, I could kick extra power on the grid. At 16 cents per KW, I would not make a lot of money, but I would make some. That is I would make more money then I consume in fuel.

IF nothing else, being hooked up in spit-swapper fashion, when my generator was shut off, the propane boiler (or whatever is heating my home) would push the warm water back through my engine, and keep it constantly between 100-212 degrees so that it would also start no matter how cold it was outside.

I cannot see why this would not work.

 

[Industrial Toys]

ALL the menonites running Diesel and NG generators heat their slabs with the waste heat. You won't even ever see a radiator. I would install Murphy shut down on the tractor before considering such a more invested approach to a PTO set.

 

[dodge man]

First off I bet your utility wouldn't take the power. They have to take solar but I bet they wouldn't take the power from a gen set. Also you engine is going to be working much harder if the gen set is making full power, using a lot more fuel. I'm guessing when its all said and done its a losing plan. You are trying to go off grid it sounds like and the only time I think that pays is when hooking up to the grid is really expensive.

 

[BrokenTrack]

ALL the menonites running Diesel and NG generators heat their slabs with the waste heat. You won't even ever see a radiator. I would install Murphy shut down on the tractor before considering such a more invested approach to a PTO set.

I got a Reefer Diesel that might work well, they are only 35 hp and sip fuel, I believe only turning 1800 rpm. They are designed to run without a lot of human interaction too.

I got another engine too, but its 131 hp which is kind of big.

 

[CalG]

The other day we lost our power, but the kids did not even notice because I hooked up my PTO Generator to my Tractor, and made power that way. But as I checked on my tractor, the engine and generator were pretty warm after running for 18 hours...not dangerously hot, but warm.



In doing the math, it would seem to be expensive at first, me saving myself about $3800 in costs for heat and electricity, but consuming about $5400 in fuel. BUT...my generator produces 20 KW no matter what my house consumes, so with net-metering, I could kick extra power on the grid. At 16 cents per KW, I would not make a lot of money, but I would make some. That is I would make more money then I consume in fuel.



I cannot see why this would not work.

Your gen set only produces as much power as is consumed. And the prime mover supplies all of it, plus some more to accommodate loss.

 

[4570Man]

The more power you pull from the generator the more fuel it’ll burn. If my math is right that’s like $3.2 per hour in power sales. How much diesel is it going to burn under full load? Probably more than $3 worth. How long is the generator and engine going to last under full load? A 35 hp diesel is probably going to make more heat than your house requires working hard continues. Are you going to shut it off when it’s too warm inside?

 

[4570Man]

ALL the menonites running Diesel and NG generators heat their slabs with the waste heat. You won't even ever see a radiator. I would install Murphy shut down on the tractor before considering such a more invested approach to a PTO set.

How do they cool them in the summer if there isn’t a radiator?

 

[Industrial Toys]

Well, I have seen a hundred because I always like to see them. I guess, having the doors open in the summer gets rid of the heat. Just like I found out with the Rad inside the cab of my Kubota Loader, the heat in summer is not oppressive, and I'm one that can't take heat! I'm guessing, like they say, it's a "dry" heat. lol




One of the larger NG sets in use.

 

[dodge man]

I'll go back to what I said earlier, I'm not for certain, but I bet they won't take the power. So you can think about it all you want but if they won't buy the power back, it doesn't do any good.

 

[Industrial Toys]

Why would you want to make power at 75 cents a KWH and sell it for 25? Just making up numbers but I'm guessing you would find that.

 

[BrokenTrack]

I'll go back to what I said earlier, I'm not for certain, but I bet they won't take the power. So you can think about it all you want but if they won't buy the power back, it doesn't do any good.

Yes and no...

I am co-generating; generating heat for my home, but also producing my own power.

In the real world, I would probably just run my Gen-Set from November to April and go-generate, then shut my gen-set down the rest of the time, and get my power from the grid.

I am not sure how the math works on that. My electrical consumption is the highest in the winter, and that is when I need heat. Assuming a 2/3 split on electrical costs, and 100% savings on heat (instead of using propane), would save me about $3200.

Could I operate my Gen-Set during that time frame for $3200...or at or below 1280 gallons of fuel?

Maybe, because I have a few options. I would have to do some heavy math with degree days and calculate out the BTU's required, but I think I need around 1/2 million BTU's per day. So that is about 4 gallons of diesel I must consume to get the heat needed for my home.

I could operate the gen-set 18 hours per day instead of 24, and save fuel during the middle of the night, and just grab what little bit I need from the grid. Because the home is radiant floor heated, the home could go 8 hours without heat very easily.

If the power company will not buy the co-gen power, then I could add a small solar array or wind mill, and then sell my excess power back to the grid as they would have no way of knowing if it was solar or co-gen that provided power, and we have to keep in mind, the main use is to heat my home, the electricity is just a byproduct of that power consumed.

The cost of the fuel could be tax-deducted.

Granted none of my calculations take into account wear and tear, but I am not sure that is a very big number anyway. Rebuilt engines are very cheap to buy, and with gen-sets, they log a lot more hours between rebuilds because they operate at a steady rpm. So the cost is rather minimal on that.

I think it is one of those things; it could be done. I am not sure a person would save a lot of money doing it, and it would take some mechanical tinkering and lifestyle changes (switching from co-gen to grid power) to pull off, but probably could be done. The only part I am really lacking is running the lines from the co-gen shed to the boiler.

 

[LouNY]

It's all doable, I would try to avoid back feeding the utility.
Mainly because of the synchronizing issues, I'm not sure how the solar units do this but I would
assume that the utility is controlling the inverter that is changing the solar DC to utility AC,
this has to be the same frequency and a slightly higher voltage to backfeed the utility.
A home generator or commercial unit will not have these abilities.
As far as recovering the engine heat that is quite doable and would be dollar sensible,
I'd be tempted to place a controlled 3 port valve that in one position would feed the floor
the other would go thru a radiator to control the engine heat.
Would this be less expensive then utility power I seriously doubt it.

 

[Industrial Toys]

What's the cost of rebuilding a generator? Sounds like an expensive boiler to me.

 

[nyone]

You will never make money selling the power company your excess power that you make in KW...while they buy it by the MW. Also most places will sell it to you at retail and you sell it to them at wholesale.

Your engine will be below operating temperature also. Bad for the engine and will prob wet stack.

 

[LouNY]

You will never make money selling the power company your excess power that you make in KW...while they buy it by the MW. Also most places will sell it to you at retail and you sell it to them at wholesale.

Your engine will be below operating temperature also. Bad for the engine and will prob wet stack.

Not if he maintains the correct thermostat in the engine.
That will maintain the engine temperature.

 

[shooterdon]

I am guessing a 35HP diesel at 1800 RPM will use about .75 gallon/hr? At $3/gal, that will be about $55/day.

If you can sell your excess power (assume 10Kw) for $.10 that returns $24/day.

So you are heating your home for $21/day and saving say $5/day on electrical power. Net for heat and power of $16/day

Then factor in maintenance on the engine and generator.

Am I missing something?

 

[ruffdog]

If you can make money selling power to the utility and heat your home from the engine cooling system, why not go BIG? I would even have local parts and a maintenance crew near by. The Fairbanks OP engines are legendary for their quality and durability.

Fairbanks Morse | Trident OP™

 

[DEWFPO]

I'd do the BTU calc's first to see if it works to heat your home, then check with the utility. As someone else said, IF they will buy the power back from you it will be at wholesale power rates or lower. They also need guarantees that you can and will provide 'clean' power back into the grid. Also, don't forget that heat put into the coolant from the engine will be nowhere near the BTU content of the fuel due to efficiency losses and heat dissipation on all surfaces.

DEWFPO

 

[the old grind]

If you use genset all Winter, go ahead and add suitable heat-exchanger to you heating loop and shunt the coolant into it just to see what's up. Electric load/output will likely vary more than heat output and fuel use/hr. (frictional losses, other real inefficiencies)

I suggest that the general idea is more sensible than silly. What to do with excess Kw, or on the coldest days? Run electric heaters at the cost you'd get the grid to pay you to feed back. When you don't need the heat, grid power saves gen fuel/oil, allows service.

Cold days, run the genset and coast thru the night (heat, as said) on-grid for clocks, office UPS, etc. KISS by switching elec source by human decision when firing up the gen, say vs ever expecting automatic stuff to know when you'd like to bump the thermostat on a dreary day or whatever.

I say don't overthink the complexity. Three separate but SxS controls, I imagine. 1) Switch power from grid to gen. (have it anyway?) 2) Switch/valve to shunt 'spit' loop 3) Switch to start gen. Build separately, and instruct to operate separately-but-in-unison. Your youngest could switch 'em with a holler from the other room. (If it looks like a good long-term plan, add sophistication/automation as time and budget allow tech tweaks.) btw, such a project/prototype sounds easy for a guy like BT.

 

[wagne223]

Even if the utility would take your unused power, you as a consumer cannot possibly generate electricity for the price the utility sells it for.

Converting fossil fuel will cost you 4x per kw over what the power company retails the power for.

The idea of using the waste heat from the engine is a good one and your idea for powering and heating your home would work for times when the utility is down.

Of course for normal use a boiler is a lot more efficient and therefore cheaper to operate.