MEP-803A Cogeneration/CHP Combined Heat & Power

[upstateguy]

Just doing some brainstorming here and thought I should start another thread. I have wanted to set up a residential cogeneration system for many years and now that I am a proud owner of an MEP-803A with only 2 hours on the clock, I feel that itch again. I suppose the robustness of the 1800 rpm design with a good quality 4 cylinder diesel and noticing all the heat discharged from the radiator section on a cool day, while load testing at 10 kw got me thinking again.

I remember reading some documentation years ago about a rule of thirds for reciprocating diesel engines referring to the fuel consumed and where that energy goes. 1/3 to produce rotational energy, 1/3 heat from the cooling system, and 1/3 heat out the exhaust.

For example while producing 10 kilowatts continuously with the MEP-803A, you are consuming approximately .9 gal per hour. If 1.0 gallon of #2 diesel fuel produces approximately 138,700 Btu of heat., then .9 gal of #2 diesel would be approximately 124,830 btu. 124,830 divided by 3 = 41,610 btu. That would mean 41,610 btu generating electricity, 41,610 btu being expelled from the radiator and 41,610 btu of heat leaving in the exhaust. 10,000 watts represents approximately 34,121 btu so accounting for engine, generator, fan, alternator, water pump, etc I can see only getting 34,121 btu from the available 41,610 btu of energy (being 1/3 total). Keeping with that mindset with a 10 kw load, we should be able to easily extract some very usable heat from the cooling system and exhaust. I’m thinking at least 34,000 to 40,000 btu of heat from the cooling system and another 34,000 to 40,000 btu of heat from the exhaust. Here in upstate NY where we seem to heat 8 months out of the year, taking advantage of this waste heat makes a lot of sense. I have some ideas to integrate this into our own hydronic heating system and will be doing some real world testing to see how much heat can be obtained. My plan is to connect into the engine cooling system very similar to how the diesel fueled coolant heaters (pre heaters) are connected, or some other configuration on the engine side of the radiator thermostat. One important aspect is to maintain the coolant temperature at a level just below where the radiator thermostat opens. Since the 802’s and 803’s use a 170F thermostat, I plan to use a thermostatic mixing valve and a heat exchanger to prevent over cooling the engine cooling system. The last thing I want to do is extract so much heat the engine runs cold all the time. Plan is to leave the factory radiator and thermostat in place so excessive heat can be dumped to the atmosphere like normal. One of my first tests will be to heat a known quantity of water a certain number of degrees F and calculate how many BTUs have been extracted from the engine to do that. Additional testing will be done to find a practical and cost effective way to extract heat from the exhaust. Of course this all will depend on time and cash flow, and it seems anymore both are a challenge. If anyone has done any experimenting with extracting heat from the 802 or 803 please share here.

 

[LuckyDog]

No input at this time.
Lots of wondering questions.

Please keep me / us updated. I love the idea.

 

[Ray70]

I'm curious about this project as well.
I have to wonder IF the engine would actually run too cool or not regardless of how you extracted the heat, as long as you leave the thermostat in place and use only the radiator / hose portion of the generator for the hydronic supplement.
I would think that if you extracted more heat than the engine was producing, the thermostat would just close down, restricting or even blocking the flow of coolant through the engine at temps below that of the thermostat, thereby preventing overcooling the internals of the engine.

 

[2Pbfeet]

Good luck!

If it were me, I would leave the factory thermostat in place. It will kick open when the engine is warm, and take care of regulating the engine temperature. Basically, hook the radiator hose to your heat exchanger. (And yes, that implies that you probably would want to use the same size or larger hoses.)

You will have some waste heat as warm air from the generator head and engine exhausting the enclosure, so you might think about where to route it for your energy usage. I would not run it directly into living spaces as there will be off gassing of diesel, oil, etc.

All the best,

2Pbfeet

 

[upstateguy]

My plan is to leave the existing cooling system thermostat, radiator, fan, etc in place, but extract heat from the engine so the engine is typically always at a temperature just a few degrees below where the thermostat opens. That way if something shuts down or fails with my heat extraction system the thermostat will just open and dump heat to the atmosphere as normal. This could also allow for preheating the engine when temperatures are extremely low before attempting to start. For the tests I want to configure it with 1” standard heater hose that way it will be similar to how you would connect a heater core fan coil to the engine. Might even be a convenient mod to add clean heat to a shop that is powered by the generator. A small external circulator like A Taco 007 or B&G NRF-22 could be used on the engine side of the heat exchanger and be capable of circulating up to 45,000 BTUs through a 1” pipe with a 10F delta T. A simple thermostatic mixing valve can be used to bypass the heat exchanger to maintain the return fluid temperature to the engine to avoid thermal shock or over cooling the engine. Once the house hydronic system is up to temperature the bypass would close. The engine I’m sure is more efficient at a normal operating temperature. There are kits that use a diesel fueled coolant heater with a Tee in the lower radiator hose and another connection to the water jacket elsewhere on the block. The pictures I have seen on gov planet for the Alaskan 802 and 803 units which all seem to have the preheat kits don’t detail the block connection. I’ll admit I need to look over the engine a little more to see where the best connection points would be.

- Matt

 

[upstateguy]

Here is a terrible quality screen capture of the T in the lower radiator hose on an 802 that has the diesel preheater unit. You can see the smaller hose goes up to the right above the dead crank switch and a second hose comes down to the side of the block.

 

[Guyfang]

Matt, go to the TM section and find the TB for the heater installation. Don't know if any information in there would be of help, as I have never given it a serious look at. But who knows?

 

[upstateguy]

I finally had a chance to go though the TB for the preheater. Looks like they connect a Tee into the lower radiator hose and the other line goes where a freeze plug gets removed. Not sure where I could obtain the freeze plug hose adapter that is used in the kit. I really would rather not have to remove a freeze plug to incorporate this, but it may be the best way to accomplish what I want to do. I’m going to have to look over the water pump and thermostat housing a little closer especially around the temperature sensor and the high temperature switch.

 

[Guyfang]

I have some Ideas about how to find the freeze plug adapter. Maybe tonight I can explore them. Grilling for a mas of people today. As long as the grand kids are happy, the rest can whistle dixe.

 

[cbisson]

As long as the grand kids are happy, the rest can whistle dixe.

I know what you mean and agree 100%

 

[Ray70]

If you look at the area near the coolant temp sensor, many machines have a hose fitting that is capped off, I believe that would serve as a feed line out, then the fitting in your lower radiator hose could be your return.
Just have to check your machine, some have rubber caps on the fitting and some have a threaded plug.

 

[2Pbfeet]

There are also coolant hose T fittings.

All the best,

2Pbfeet

 

[Guyfang]

Ray wrote:
If you look at the area near the coolant temp sensor, many machines have a hose fitting that is capped off, I believe that would serve as a feed line out, then the fitting in your lower radiator hose could be your return.
Just have to check your machine, some have rubber caps on the fitting and some have a threaded plug.


As soon as I saw the CAGE code, I knew this was not good. 30554, that is the cage code for CECOM. Any part number, (98-2034) with that CAGE code is a made up number. So the part number is of no help. And part # 98-2034 is not a high usage part, so no one wanted to spend money on it for a NSN. More non help.

So I looked in the Lister-Peter TM's. A stink normal freeze plug has a part # of: 750-11390.

Then I looked through more Lister-Peter books for heaters. There are lots and lots, of heaters. But none that tap off the freeze plug. They do just what @Ray70 suggested.

For any useless data freaks out there, there are several NSN's for the whole heater kit.

6115-01-477-0564
6115-01-477-8344
6115-01-477-8354
6115-01-477-0566
6115-01-575-5744 This is the Master, (Best) NSN.

So if you just HAVE to do it with the freeze plug, I would call up/email who ever is now selling/servicing these engines, send then the pictures and descriptions, and say, "Help me." I know its no longer Lister-Peter, but thats about it. Ray or LITD should know who it is.

 

[Ray70]

Another thought is:
I've had a few 802's and 803's with the arctic heater kits in them, but there is no need for them anywhere near me, so I removed them and sold them as a complete kit.
To put it back to original I removed the modified freeze plug and put a normal one back in it's place, providing the modified plug to the buyer.
The freeze plug was easy to find at my local parts store, just measure what you have now. It was around 3/4" or 7/8" if I recall.
You could get yourself a new freeze plug and weld ( if steel ) or braze ( if brass ) a hose barb fitting into it.
It's very easy to change, easily accessible.
But if your machine has the provision near the temp sensor I would just make use of that.

 

[fb40dash5]

You could get yourself a new freeze plug and weld ( if steel ) or braze ( if brass ) a hose barb fitting into it.

I'm pretty sure that's really all someone did for the one in the preheater kit.

I have one laying around, unfortunately it's laying next to the rest of a removed preheater kit.

 

[uniquify]

What about something like this along with a npt to hosebarb fitting?

This is from listing on ebay for a "New Frost Plug Heater Bushing Adapter 3/4" FNPT thread, 1-1/4" BUSHING, 32 MM OD".

I can't guarantee it'd fit, but it seems like it could work if it were the right size.

 

[upstateguy]

I finally had a chance to read up on everyone’s comments, some great ideas which has caused me to do some more digging. I took some pictures of my engine water pump and thermostat housing, then looked up some drawings which didn’t have a lot of detail, but searching for the water pump 186-6178 I found some good images of the water pump casting from various perspectives. So I came up with the following conclusions on the lower 2 ports. The water pump returns coolant back to the block, the hot coolant travels out into the thermostat housing where the water pump will either draw the coolant directly back into the block or if hot enough the thermostat opens and the water pump draws cooled coolant from the lower radiator hose. The upper angled port closest to the lower radiator hose goes into the return hose cavity of the casting, the lower port is in the discharge path of the water pump volute where coolant passes back to the engine. See the attached images for details. It looks like I could use the angled return port or use a tee in the hose for a return, but for supply I would have to use the high temperature switch port and Tee in the high temperature switch at that location. The ports are pretty small so the amount of heat I could recover would be very limited. This would probably work fine for a small fan coil of 5,000 to 10,000 BTUs, but probably not able to pass enough volume to obtain 40,000 BTUs of heat. The ports appear to be 3/8” to 1/2” (just guessing) so that is not a lot of volume. Better than nothing and minimal changes to access some heat, but probably would still be dumping large quantities though the radiator at higher loads. So I’ll have to do some more brainstorming, possibly looking at removing the thermostat and installing an “in hose” thermostat near a tee in the upper hose or some type of custom thermostat housing to allow connection of a larger supply line on the back side of the thermostat. After some more thought, I am concerned that connecting to the rear freeze plug location may cause stagnated coolant flow in the engine passages possibly leading to hot spots. Just more brainstorming, I appreciate everyone’s feedback on this and the ideas are great. I may go ahead and connect to the smaller ports just to see how many BTUs I can extract..

 

[Summerpaws]

Interesting subject. 30+ years ago I had a similar thought. I was given the opportunity to get a free 7.5KW MJDE Onan Marine generator out of an old Trojan Tri Cabin that was being demolished. I brought it home and it ran and produced power with very little work. I was working in a co-gen power plant at the time and I wanted to see if I could use this generator to power my home and use the waste heat from the cooling system to heat the house. I envisioned tapping into my hydronic system and using all the baseboard radiators to cool the engine.

Before I even thought about how I was going to hook the electrical side of the generator, I wanted to do a proof of concept regarding the cooling system. I mounted the genset to a base made of 4X4’s and moved it into the basement up against an outside wall.

The generator had a water cooled exhaust using raw sea water pumped into a heat exchanger then out into an exhaust riser where the raw water mixed with the exhaust and out of the boat via a rubber hose and a water lift muffler. The heat exchanger acted as the radiator for the generator The cooling system of the generator was filled with coolant. I was able to eliminate the riser and fabricated an exhaust system out of steel pipe. I used an automotive muffler and ran it out through one of my basement windows using an aluminum plate. I tapped into one of the perimeter pipes that went from my furnace to all of my baseboard heaters and back to the furnace.

I ran a hose from the raw water pump inlet and another hose from the discharge side of the heat exchanger.
It took a bit of work to purge the air out of the system but eventually I got it.

I ran the generator unloaded for my first attempt. If I remember correctly, I ran the generator for close to an hour and the pipes to my baseboard heaters were barely warm. I then wired the generator to a couple of heaters and that helped a bit but still, the pipes stayed only luke warm. The engine was at operating temperature due to it’s closed cooling system but there was not a lot of useable heat to heat the house.

Thinking about it, I figured that maybe I was moving the water too fast through the system. I eliminated the raw water pump and wired the furnace circulator pump to run off the generator. That helped a bit but I still got very little heat from the baseboard heaters.
Thinking about it more, it dawned on me that the furnace itself was still in the circuit. That held several gallons of water.. My thought was it was simply taking too long to heat that huge volume of water. At that point the project was getting complicated and the wife was not happy.


Takeaways on this:

The generator was LOUD. I was going to have to make a sound deadening cabinet.

I was going to have to figure out if I could wire the gen for 120/240. Some people told me it couldn’t be done, some said it could and some said if I did I would have voltage regulator issue.

If I was going to get serious, I would have to re-plumb my heating system to eliminate the furnace when the generator was running. I think that would have allowed me to get heat to the baseboards quickly. (The water coming out of the heat exchanger was hot.

I thought about plumbing the hot water from the heat exchanger to go in to the house system right after the furnace so the hot water would hit the baseboards first but my furnace was nowhere close to where the generator needed to be so…more complications.

Much to my wife joy, I gave up on the project but I still think it could/would have worked.

I like your idea and I will stay tuned to see how it goes.
My first thoughts on your idea is if the generator is outside, you will have to run coolant in your house system unless you use a heat exchanger.

 

[upstateguy]

About 30 years ago our neighbor had a small wood boiler that was a section of large steel gas line maybe 2’ in diameter and 4’ deep with a rectangular water tank welded on the top. A friend of her husbands built it and her husband connected it to the main radiator loop in the house and had issues with the radiator loop not getting much more than “luke warm” (100F or so). I looked it over and came up with a good solution for them. I connected the small wood boiler to her oil fired boiler with a pump that ran as soon as the aquastat in the well of the wood stove tank exceeded 160F. I then connected a pipe mounted aquastat to that separate loop between the oil fired boiler and the wood stove so if the loop temperature got above 190 on the return from the oil boiler to the wood stove, the pipe mounted aquastat would parallel the upstairs thermostat and force the main zone on as a call for heat until the loop temperature dropped to 180. We used the mass of the cast iron oil fired boiler as a thermal battery. The oil fired boiler also had a tankless hot water coil so it would provide all the domestic hot water they needed. It did have an anti scald thermostatic mixing valve on the domestic hot water supply so scald issues from hot water was not an issue. With the wood stove running, the main loop would cycle on for about 5 minutes and then off for about 4 minutes. If the temperature in the house was below the thermostat setting, the zone circulator would turn on and call for heat, but would not fire the oil boiler until the system water temperature cooled down below 160. It did take some trial and error to get the aquastats set where everything worked smooth. This system worked well for about 10 years until the home was flooded and they installed a coal/pellet stove upstairs where systems wouldn’t flood.

My plan is to connect the generator outside, about 15’ away from the house for noise, exhaust, and general safety. Run a dedicated small circulation pump from the convenience outlet power (internally, not plugged in) using insulated 3/4” oxygen barrier PEX to an indoor located heat exchanger so I won’t need glycol throughout my house system. I am also planning to add a large buffer tank in my primary boiler loop and configure the system so I will not overcool the engine coolant, but also allow for the existing radiator and engine thermostat to dump excessive heat if my pump fails or it is a summer and I only need enough to heat up the buffer tank and our indirect fired water heater. At that point it is good to dump the heat outside.

We primarily heat our 3,000 sq ft log home with two 12,000 BTU minisplits, (which actually provide up to 20,000 btu of heat each until we are around -10F. We only need about 30,000 btu of heat to maintain the temperature in the house when the outside temps are 0 to -10 F. When the power is off or the outside temperature drops below -10 for an extended time, we switch on the propane boiler. We have multiple radiant floor zones and while running the propane boiler at 180F, the insulated concrete basement floor has a max water temperature setpoint of 100F if the outside temperature drops to -20F.

I have a 30 kWh rack mount lithium iron phosphate battery bank connected to a 12 kw split phase 120/240v inverter. Which easily runs the entire house for 24 hours. Eventually I will add some solar, but for now my plan is to run the generator using two 5 kilowatt chargeverters (240VAC to 57 VDC 5 kw rectifiers) to recharge the battery bank while running house loads. I figure this way I can easily load the generator with a nice fixed 8 or 9 kw load when running, prevent wet stacking, maximize power use while running and the heat produced by the engine. There are definite challenges to make the heating system play well with the waste heat from the generator. I figure if the power is off for an extended time, I really want to take advantage of the waste heat. Just connecting in a fan coil unit like a heater in a car with an aquastat and thermostat on the fan so the fan doesn’t run unless the water temp is above 160 and the room temperature isn’t above the setpoint would be a good application. It is nice to be able to share ideas with like minded people, I am really enjoying all the discussions here and the wealth of knowledge everyone is willing to share.
My wife is also a saint for putting up with my experiments. She actually really likes our “new” 2003 (2014 reset) MEP-803A that has 6 hours on it now.

 

[DD58]

I had the same idea but with one of those small Chinese diesel heaters. The exhaust of it was so hot you could cook a burger on it. I ended up using an Amazon heat exchanger and a heater core from a s10 I had laying around. Ran 50/50 antifreeze in it with a small 12 volt fan. Had to add a 2 gallon coolant tank to help cool the loupe down. Doubled my head out put in my shed. I can now work in the snow in shorts a one a t shirt. Can’t wait to see your come to fruition!!


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