240D engine as CHP generator - PeachParts Mercedes-Benz Forum

funola · #1 10-08-2009, 12:48 PM

Has anyone used a 240D engine as a combined heat and power generator? I'd like to run it on veg and produce electricity and take the coolant and run it to an A coil in the house for heating. Has anyone in the forum done that with a 240D engine?

Graplr · #2 10-08-2009, 01:09 PM

I've read about someone powering appliances in their house with an inverter during a power outage, but nothing to the extreme you are talking about.

I'm not sure how much electricity you would get out of it. Perhaps others will know. Probably not enough to run an entire average house.

With enough work, I'm sure it could work. I guess the question is, how much work do you want to put into it?

ah-kay · #3 10-08-2009, 01:30 PM

I thought about it myself and here are my thoughts.

1) Engine in car - if you use an inverter hook to the battery then you will only get about 1KW max from the inverter. Assuming you get a heavy alternator which put out 100A. It is still quite good and just leave the car in idle or rev it up a bit.

2) Engine out of car - You can hook a generator head to it. Rev the engine to 3600rpm, I think most head take 3600rpm. Head is around $300 from Harbor Freight. This will give you may be 5KW or more, enough to run a whole house.

3) Run the coolant to a heat exchanger to heat your hot water or radiator in the house. It is possible but may be messy and need some inventiveness. Never thought of this.

4) Sync the power from the generator head back to the grid to feed surplus electricity to the operator. It is doable and you can sync it manually but it is dangerous and a try and error process. The electricity company may not let you do it. An automatic phase synchronizer is out of the questions. It is very expensive and not within the realm of a DIY.

I think in general it is doable for off grid use. An inverter is the best, and heat your hot water. Any members have other ideas?

pawoSD · #4 10-08-2009, 01:31 PM

A 616 can produce way more than the needed power to run a house. With the right setup attached to it you could probably get 50,000 watts or more. Fuel consumption at that output would be pretty high though. Even at normal levels, I'm betting that you'd need one heck of a supply of veg oil.

Running at 3600rpm with a moderate to low load would probably use at least 1.5 gallons an hour

Graplr · #5 10-08-2009, 01:35 PM

Quote:

Originally Posted by ah-kay

3) Run the coolant to a heat exchanger to heat your hot water or radiator in the house. It is possible but may be messy and need some inventiveness. Never thought of this.

I don't see why this wouldn't work. A solar thermal hot water system works basically the same. A panel or tubes on the roof are heated from the sun as the coolant is pumped to either an in-tank or an external heat exchanger.

Hot water tanks designed for a solar application should work.

And, depending on your climate, hot water is one of the biggest energy users in the house. So not having to heat your water would lessen the amount of elecricity that would be required in your home thus lessening the output from the engine.

Skippy · #6 10-08-2009, 01:46 PM

I found this in a few minutes of searching: http://www.northerntool.com/webapp/wcs/stores/servlet/product_6970_8795_8795

10 kW generator head, spin it at 3600 rpm and get 9600 W continuous. Takes 18 hp, says the website.

Peak mechanical output on a 616 (62 or 67 x 746) comes to either 46 or just under 50 kW, but you'd want to stay lower for a continuous duty situation.

What are you wanting to power?

ah-kay · #7 10-08-2009, 01:47 PM

Quote:

Originally Posted by Graplr

I don't see why this wouldn't work. A solar thermal hot water system works basically the same. A panel or tubes on the roof are heated from the sun as the coolant is pumped to either an in-tank or an external heat exchanger.

Hot water tanks designed for a solar application should work.

And, depending on your climate, hot water is one of the biggest energy users in the house. So not having to heat your water would lessen the amount of elecricity that would be required in your home thus lessening the output from the engine.

It would work. But you need to be inventive to hook up the plumbing. This is free energy. It all depends on how much effort one wants to put into this kind of project. Need to do a cost benefits analysis as the payback period can be long. This includes solar power, Prius, hybrid cars as the payback period is long, very long.

tombance · #8 10-08-2009, 01:53 PM

You would also have to rig up a governor for the engine to keep it at 3600RPM under any load...

Crazy_Nate · #9 10-08-2009, 02:01 PM

Ok, here are my thoughts:

68 HP ~= 50.7 kW
If you're going to use the engine for heat you have two sources:
1. Engine coolant - used for regulating the engine temperature
2. Exhaust - plenty of heat, may consider an air-water heat exchanger
For the engine coolant you need three things to consider:
1. The engine is not yet at operating temperature, coolant is circulated until it reaches an operating temperature
2. The engine is at operating temperature, cooling capacity is sustained by heating house water - water / water heat exchanger.
3. The engine is at operating temperature and the house heating needs are not capable of cooling the engine - use something like a bypass through an external radiator / fan

On the generation side - you need to decide between using 12VDC or 120VAC. Obviously one is easier for charging a battery array (think of it as a crude power smoothing), and then if you're not running things off of DC, use an inverter - there are various sizes for renewable applications, however, the larger inverter you want, the more it can cost.

For AC, you can run a synchronous generator at...well...its synchronous speed (with a 1:1 transmission ratio): here.

For a 2 pole generator - this is 3600RPM for the 60Hz power in the US (4 would be a reasonable 1800RPM). With that said, if you wish to tie into the grid, you need to make sure that your sinusoidal voltage fluctation is consistent (synched) with the grid - not fun. Synchronous wind turbines have interesting starting procedures because of this.

What kind of duty cycle would you operate the engine at? Would you size the generator for peak load, or for continuous operation?

Graplr · #10 10-08-2009, 02:02 PM

Quote:

Originally Posted by ah-kay

It would work. But you need to be inventive to hook up the plumbing. This is free energy. It all depends on how much effort one wants to put into this kind of project. Need to do a cost benefits analysis as the payback period can be long. This includes solar power, Prius, hybrid cars as the payback period is long, very long.

I know a guy who has a solar thermal panel on his house here in MN. He installed it about 20 years ago. He ran his costs and it was about 7 years pay back in energy savings. Obviously many variables go into the equation...just stating what it was for him.

ah-kay · #11 10-08-2009, 02:25 PM

Quote:

Originally Posted by ah-kay

It would work. But you need to be inventive to hook up the plumbing. This is free energy. It all depends on how much effort one wants to put into this kind of project. Need to do a cost benefits analysis as the payback period can be long. This includes solar power, Prius, hybrid cars as the payback period is long, very long.

Graplr - what I meant is that some projects are difficult to justify except the feel good factor. I think Solar Hot Water ( convection type ) has the best return and short payback period ( your friend's system ). Very little mainenance and abundant amount of hot water. I had one on my roof until the tank leaked. The water was so hot and abundant that I can 'sell' it to my neighbors. As for Solar cells to generate electricity, the capital investment is huge and the payback period is long. You may get a tax credit for solar cells. Same goes for hybrid cars as you only save, may be $40, of gas per month but the premium is $5000+. Even project like this post is not really worth it except for the inverter. After you added the head, a governer, wiring, switch panel, plumbing, bypass radiator etc it would come to a considerable amount of money plus your sweat equity.

fruitmeister420 · #12 10-08-2009, 02:35 PM

What I'm seeing here is that the engine will produce an abundance of power, and the generator head needs to turn at aprox 3600 rpm. You could utilize the transmission to take advantage of that excess power and gear up to your desired RPM output.

Well it's just a thought

Graplr · #13 10-08-2009, 02:37 PM

Quote:

Originally Posted by ah-kay

Graplr - what I meant is that some projects are difficult to justify except the feel good factor. I think Solar Hot Water ( convection type ) has the best return and short payback period ( your friend's system ). Very little mainenance and abundant amount of hot water. I had one on my roof until the tank leaked. The water was so hot and abundant that I can 'sell' it to my neighbors. As for Solar cells to generate electricity, the capital investment is huge and the payback period is long. You may get a tax credit for solar cells. Same goes for hybrid cars as you only save, may be $40, of gas per month but the premium is $5000+. Even project like this post is not really worth it except for the inverter. After you added the head, a governer, wiring, switch panel, plumbing, bypass radiator etc it would come to a considerable amount of money plus your sweat equity.

Agreed. Most people do it because they like alternative energy, not for the financial savings. And I also agree that solar thermal has the best return on investment.

Diesel911 · #14 10-08-2009, 02:40 PM

There used to be Mercedes Engine Powered Thermo King Generator sets for the Refridgerated Trucks. They already have a Generator on them and a proper Governor and put out 220-240 Volts. In 1990 when I did that sort of work there were still some in daily use.
Might be easier just to find one.

The most of the Gen sets I have experience with ran at 1800 rpm when at full load.

There also may be a Marine liquid cooled.Exhaust Manifold for boating use. That would give you way more heat than the Radiator could put out and at cold temps that Engine may need to keeps the heat to itself.

bustedbenz · #15 10-08-2009, 02:46 PM

I don't know anything about running generators at a certain RPM, but 3600 is going to be pretty loud and pretty obnoxious after a while. Any method you could come up with (gears... transmission... somebody said something about poles on the generator???) to run 1800 instead of 3600 RPM would go a LONG way toward making this a more practical machine after you build it.

Also, is the engine's water pump strong enough to circulate coolant the distance from the generator to the house heating equipment and back with enough leftover capacity to ensure the engine is being cooled enough. Something to think about is that water pumps do fail, leak, whatever from time to time, and perhaps it would be worth looking into building some sort of safety for that, sort of like a low oil pressure shutoff, so that when the circulation system finally fails, the engine won't toast itself during the interval between when it dies and when you finally notice the house isn't getting warm anymore.

Since the speed of the engine is mechanically governed by the accelerator pedal and associated linkages and things and most 240s don't have tachs, I'm not sure how convenient or easy it's going to be to rig up a governor to keep the RPM constant to run the generator. When you do figure that out, would it be possible to tie some sort of low oil/low coolant engine shutoff safety feature into that mechanism? If it's already connected to the IP linkages somehow then it might be easy enough to have the thing shove the stop lever instead of throttling up when it detected those conditions.

If I was going to the expense of building this thing, (I agree with those that are saying the return on the investment is going to be a while showing up; you'd have to REALLY like alternative energy to go to this much trouble) -- I'd want a few of these safeties I'm talking about to keep it from exploding itself -- and I'd definitely not be able to stand hearing a 3600 RPM diesel roaring away constantly any time my house needed electricity. 1800 wouldn't be so bad.

Just my if-it-was-mine two cents. It's not my project.