Hot Topics: Homemade Cogenerator Plant

cogeneration plant's Forum features conversations among 250,000+ experts and novices in over 120 categories, so each week, we highlight a conversation that may help you with a project. This transcript has been lightly edited.

Original Post: DIY Cogeneration Plant

WastePipe - Thread Starter

So I got bored and decided I had all the major components to make a DIY Cogeneration Plant, so a week or so ago, I started.

I have got farther than I thought I would. The overall plan is to put a separate engine on my 83 amp/20 KW PTO Generator, then divert the coolant water of that engine into my radiant floor heating system. Along the way I am going to plumb in a wood/coal boiler I have sitting idle, so when it is all said and done, I will be able to produce my own electricity, at the same time, heating my house (hence the name cogeneration).

For an engine for the PTO generator, I have a 4 cylinder Kubota engine off a reefer unit that I had kicking around, and am going to start with that. I managed to get they hauled up into my generator room by myself by rolling the 800 pound unit up an incline on pipes, and got it all stripped back to the engine. This meant removing the chiller parts, stripping the wiring off it, and then starting to work my way back out to make this thing run. Fortunately it was not seized as bad as I thought it was.

The rebuild started yesterday, with me making a new engine mount for the rear of the engine, then me grabbing a new starting panel off an old generator I had kicking around.

Along the way, I dragged in a 275 gallon fuel tank I also had kicking around. I ended up painting that a nice gray, and getting that into position inside the generator shed.. And then I managed to get the wood/coal boiler into the generator shed as well. This is located about 100 feet from my house, and is 12 x 24 and well insulated, so it should work well.

The plan now is to go in stages:

Get the starting circuit built

Get the engine running off from starting fluid

Get the fuel tank and lines hooked up and the engine running off from off-road fuel

Get the pto generator into position and married to the reefer engine

Get the generator hard-wired to the house

Get the draft controls on the wood/coal boiler in place (Chimney and forced draft intake air)

Plumb the wood/coal boiler to the genset engine

Plumb the genset/wood and coal boiler to the radiant flooring heat of the house

beelzebob- Member

Good luck. I would first do a calculation to be sure I can heat the house volume desired (with losses) from an engine that has a specified coolant operating temperature and a required flow rate determined by the water pump. I would be leery of the wood/coal aux boiler being used as controlling its heat is crude at best. If the closed heating system got hot enough to turn to steam it could explode.

zeezz - Member

Interesting project, but what is your goal with this? It will be significantly cheaper to just burn heating oil in a boiler than to run an engine to make the same amount of heat, even if you consider the cost of electricity you would generate. Then there's all the engine maintenance that would need to be done. You're loosing roughly 1/3 of the heat energy straight out of the exhaust, and you are not collecting 100% of the water energy either. You could really go nuts and make everything super efficient and coupled with a heat exchanger, but you will still never beat buying electricity and burning oil in a boiler.

Now, if this is just meant as a backup, or even a hobby, this is a great idea. If there was a power outage, you can heat your house with less total fuel than if you were just running a heater from the generator. And sometimes it is fun to just play with generators.

Cogeneration is a subject I have studied very closely and experimented with for years, but is almost impossible to make it worth the effort if you have power lines outside your house on a small scale. Much more suited to businesses, large apartment complexes, and similar things. Personally, I'd have kept the reefer unit together and turned it into a giant diesel powered heat pump! That could potentially be run for less than with grid power for heating.

I'd love to see some pictures of your setup.

Pilot Dane - Group Moderator

Where are you located? Burning diesel to generate your own electricity is one of the more expensive methods even if you do reclaim the engine's waste heat. If you are off the grid it makes sense to use the engine coolant for heating while generating electricity. It's commonly done on boats/yachts so it's not a crazy idea. It's just a expensive way to power the lights unless you don't have another option..

zeezz - Member

"Burning diesel to generate your own electricity is one of the more expensive methods even if you do reclaim the engine's waste heat."

I agree, diesel prices are a bit ridiculous these days, even offroad diesel. If your goal is low cost heat, you should look at mini splits (they can heat water too!) or simply burning wood.

I've done some rough math recently, I can buy gasoline for about $2.10 at the pump. If I use it in a generator I am entitled to $0.61 in state/federal tax refund per gallon. That's only $1.49/gallon for "offroad gas".

An average gasoline generator will produce between 4 and 7 kilowatts per gallon of fuel burned. I've tested my generator at 5KWH per gallon. So just for electricity, it cost $0.298 per kilowatt hour. My power company only charges about $0.13 per kilowatt hour.

If we could "catch" 100% of the waste heat from the generator it would look something like this:

5kw = 1 gallon per hour = 111,836 BTU total. Roughly 1/3 of the BTUs get turned into electricity, and 2/3 is heat. So you have available 74,557 BTU of usable heat per hour plus 5 kilowatts of electricity.

If we compare that to heating oil, a normal burner will be at least 80% efficient if not better. Heating oil has 139,000 BTU/gallon, with 80% efficiency you get 111,200 BTU per hour. If your heating oil cost $2.50/gallon, the 74,557 of usable heat from above is worth $1.67 in heat. Add 5 kilowatts of electricity, = $2.32 in recovered energy. But you probably spent closer to $2.50 on a gallon of fuel! And you haven't added maintenance costs yet. You have built a machine that does a great job of burning money.

This example is with gasoline, not diesel, but diesel currently cost more per BTU than gasoline does, thus a diesel generator would have even worse numbers. Gasoline would actually make a reasonably priced heating fuel if you burned it in a boiler, but they don't really make those and it would be much more dangerous to keep around than other fuels.

WastePipe - Thread Starter

I came to the conclusion that producing my own power and heat would cost about $1000 more per year than buying power from the utility, and buying propane to heat the house. But that was based on buying a turn-key $8200 genset every 30,000 hours, and operating the system 24/7 for the heating system (150 days)

In real-life, it is impossible to calculate, because a person would never operate a cogenerational unit that way.

Since the engine would produce 242% of my heating needs per day, that would mean I would only have to operate the genset for about 10 hours per day to get all the btu's needed for my house per day. That is because there is heat storage in the radiant floor heat of the concrete slab.

That would allow me to operate the system genset at optimal times for making power; most likely a 5 hour morning run, and then a 5 hour evening run, and then purchase power off the national grid during the down-times. This would mean buying power not only at its cheaper off-peak hour cost, but also when my home is consuming so much less power. Operating it in this manner, a homeowner would be achieving 100% of their domestic heat, and about 75% of their electrical purchases from the utility: yet their genset is consuming 60% less fuel because is not operating 24 hours per day.

It ends up being impossible to calculate because it depends on what a homeowner is comfortable doing. The more they match the gensets heating and power needs to their lifestyle, the more efficient it will be, but if they want to thumb their noses at the electrical grid utility and be a stand alone entity, then they will pay for that.

The biggest issue I see on calculations is that everyone is made on a 24/7 basis, and that does not have to be the case.

The other thing is, just because a home CAN make their own power and heat, does not mean they HAVE too. This will cost me around $500 to put into place; so just having the ABILITY to make my own power and heat makes it worth doing. But this is my conclusion; other homeowners may come to a different conclusion, and be fully justified in that.

zeezz - Member

"Since the engine would produce 242% of my heating needs per day, that would mean I would only have to operate the genset for about 10 hours per day to get all the btu's needed for my house per day. That is because there is heat storage in the radiant floor heat of the concrete slab."

It's not gonna work like that. In order to do that you would need a very very large amount of thermal storage besides the floor itself. Your floor is not going to stay hot 14 hours a day and then it won't get warm again for many many hours after that. There is nowhere near enough thermal mass in your floor to do this, and even if you tried the floor would always be very uncomfortable - either too hot or too cold.

"It ends up being impossible to calculate because it depends on what a homeowner is comfortable doing."

Nothing is impossible to calculate, it's actually quite easy. 1. How much heat do you need? 2. How much electricity do you need? Both are easy calculations. If you do the math, again, you will find this engine setup to be at least twice the cost to run as anything else.

The problem in most residential settings is that you need more heat than you do electricity, so you will need thermal storage if you are not running the engine constantly. But you also have to have a way to get electricity when the generator is off, so you can't disconnect from the grid. And you have to have a way to use the electricity again when your generator flips on - are you just going to use a transfer switch and have every clock/computer reset every day when they lose power for a second? If not you'll need to also setup a very expensive inverter/battery setup. Then summer comes and you basically need no heat except maybe a tiny amount of DHW. You haven't said anything about an exhaust heat exchanger, so you are still losing 33% right out the pipe, but they are also expensive to put together and never 100% efficient.

Not trying to burst your bubble, but it just ain't gonna work with those fuels at your scale. All it will do is incinerate money. I'm still not really sure what you are even trying to do. If you want independent power, there are better ways. If you want cheaper heat, there are better ways. Diesel fuel is a dead end in 2020.

The best current source of cheap/independent power is solar panels. They are less than $1 per watt without tax incentives these days. They work in places that aren't even that sunny, and give you power in the middle of the day when it is most expensive. They also work if there is a power outage. You can also make hot water with solar panels, even in the winter.

WastePipe - Thread Starter

I disagree, but in part because some of your assumptions are not what I am experiencing.

For instance, my radiant floor heating system. Before I had back-up power, the house would only lose 1 degree per day. What I mean is, if the power went out for 9 consecutive days, the temp in the house would only drop by 9 degrees. the amount of btus that 60 cubic yards of concrete can accept, is pretty amazing: slow to heat up, but also slow to cool down.

Another assumption is that 33% of the heat of the engine goes out the exhaust stack, That is not what engine manufactures report. They design their engines so that 95% of the heat of a naturally aspirated engine gets transferred into the coolant system.

An engine dispenses 25% of its energy consumed in mechanical energy, and then 75% of that is heat. Of that heat, 95% gets transferred into the coolant system, so there is significant heat to be gleaned.

I came to that conclusion when we were out of power for 18 hours, and as I checked on my tractor now and then, realized how much heat was being produced...and then wasted! So I started looking into this, and then realized they have a name for it, cogeneration. Then I found out te Amish have done this for years, and now the Dept of Energy is encouraging homeowners to get into it in the Northeast because the high price of electricity here.

What I like is the low least for me... because I had all the major components like the spare boiler, the diesel engine, the generator, and the radiant floor heating system to tie into. I just have to put the components together. When I am done I will probably have $500 tied up in this when I am done, and can heat my home and power it multiple ways:


On Grid

Off grid



Diesel Fuel




zeezz - Member

Sorry buddy, you do not know what you are talking about. Seriously, I could teach a college course on this subject.

"Another assumption is that 33% of the heat of the engine goes out the exhaust stack, That is not what engine manufactures report. They design their engines so that 95% of the heat of a naturally aspirated engine gets transferred into the coolant system."

Wrong, wrong, wrong!! Stick your hand on a hot exhaust pipe and tell me that is 5% of the total heat! An average engine puts 1/3 out as useful energy (electricity in this case) and 2/3 as heat. Any mechanical engineer can tell you this. The heat is split almost evenly between engine coolant and exhaust. Different engines carry slightly different efficiencies, but nobody has ever produced one that put 95% of the heat energy into the coolant. Not possible, and would not be useful in most cases. Even boats, with water cooled exhaust manifolds, do not remove 95% of the heat from the exhaust. A giant, super efficient setup like the power company might use for backup might get something like 40/30/30 energy split, but guess what, you have a really, really inefficient engine/generator setup.

As for the cost, if you only spent $500 on this entire setup, it's not going to last. I'm sure you think it will, but I can promise you if you try to run this thing every single day you will be fixing it and tinkering with it every single day. A proper reliable and efficient setup will cost many many thousands of dollars, and still burn too much fuel. Your setup will waste even more fuel than a good professional setup would.

I'm not trying to attack you, but the thing about facts is they are true whether you believe them or not. There are many many facts available on this topic, there are books you can read, there are forums dedicated to this, and everything can be calculated. You just do not have a strong enough understanding of what you are doing to be doing it very well.

If this is just a way to stay warm and comfy when the power goes out, that's great. I think a secondary heating system and a fully installed backup generator is a very smart thing to have. Trying to run it every day for no apparent reason, is ridiculous. You are getting the wrong idea from the department of energy, I can assure you they are NOT encouraging anybody to take apart an old reefer, and make a half butted diesel generator out of it. They are not encouraging anything diesel powered anywhere. And the thing about the Amish, is they do not believe in things powered by electricity.

As for heating your slab, try turning off your heat source for 14 hours per day and see how long that lasts. Have you even tried for more than a few days?

Prove me wrong. You haven't actually offered up any facts or any photos of your setup. Boy wouldn't I look stupid if you could post some facts and figures that show you are saving money or being efficient!

What are you posting for if you are already an expert? I'm honestly not sure. Have you even measured how many KWH per gallon you get?

WastePipe - Thread Starter

In life what I have found is, a negative statement cannot be proved.

There is very little I can do when I cite something, and a person says, “well I do not believe you.” At that point, any attempt to justify the citation becomes circular.

But your statement is counterintuitive to why I joined this site. We live in a world where people are told they cannot do things without buying it, and that is just not so. I am on this site, and mention this project so that people are encouraged and gain confidence in doing things for themselves.

How does Generac make a genset? They take someone else’s engine, mount it on a frame, put a generating head behind it, add some controls, and it is a working generator. I am doing the same thing. To say it will be a wrenching nightmare is outright wrong. I happen to be a human, and Generac happens to have humans assembling their components too.

That applies not just to me, but to anyone on this site. Take a stroll around Youtube searching for homemade inventions, and you will see the amazing skills and engineering everyday people have made over the years.

My faith in people, and not in original equipment manufacturers.

WastePipe - Thread Starter

This is a project that a lot of people on here can do. My parents installed a 14 KW Generac Unit, and when they were done, it cost them $6000.

A person could buy a used reefer engine for $2000, a rebuilt PTO generator for $800, add a fuel tank for $100, and do some wiring and have more KW's than my parents for less than half the money.

Let's say they did not want to buy components and put them together. A homeowner could buy an old Ford 9N for $1000, buy the rebuilt generator for $800, and have a 20 KW generator ready to go for $1800.

And that is not even taking into account the "clean power" that PTO generators provide compared to gas driven portable generators.

These kinds of projects get people thinking, and realizing there are many other ways to get what they are looking for without spending a fortune.


02-08-20, 06:40 PM




Join Date: Mar 2010

Location: USA

Posts: 3,819

Received 44 Votes on 42 Posts

What did you do with the original engine that come with the generator unit?

On principle, the idea is a good one. But I would design the system strictly for my electricity needs. Whatever heat given off and that could be captured would be an added bonus.

  1. Build/install the system and get the electrical part working..
  2. Add plumbing to route the engine cooling water into the house, either connected to an existing hydronic system inside or through its own plumbing and baseboard radiator loop inside
  3. The returning cooling water for the generator engine still goes through the generator radiator, here connected in series and equipped with louvers that vent the heat to the outside (of the generator shack) preferably only when the house interior has reached the desired temperature.
  4. For summer, manual valves are provided so the generator cooling water skips the house heating pipes and goes only to the generator radiator.
  5. Set the thermostat for the house heating system so that it comes on minimally or maybe not at all when the generator is supplying heat to the house.
  6. When utility power is on normally, leave the generator off and use other heating as needed.

No need to do any calculations re BTU, gallons per minute, exhaust stack losses, natural aspiration, etc.

You might call my approach an electrical plant with coheating as opposed to a heating plant with cogeneration. I do not think of the wood/coal heated boiler next to the generator as part of cogeneration, at least not unless it throws off steam that also spins a turbine connected to a generator.

alan73 - Member

seems like a great idea to capture the heat off the engine both the cooling system and exhaust to increase efficiency but I also dont see this being cost effective you would need to cut power generation by a lot more than 10 hours a day would really look at your fuel cost more you have an inefficient engine running 10 hrs a day how much fuel will you need a day.

you would really need to have storage like battery inverter set up to be able to reduce generator hours considerably then it might be possible along with solar power.

WastePipe - Thread StarterAllanJ...the generator I have never had an engine, it is a PTO generator so it is designed to be powered by a farm tractor. They are designed for farmers to power their farms like milk tanks and whatnot when the utility line goes down. Since a person is not buying an engine with the unit, they are much cheaper.

The downside is, a person has to go off back-up power if they use their tractor for other tasks, like plowing snow out of the driveway, or at least do that after the power comes back on. And another downside is, putting all those extra hours on their tractor. The longest we have ever been without power here, is 14 consecutive days, but that is 336 extra hours put on the tractor.

You make some very valid points though. It is cogeneration, so what does a homeowner prioritize for? 100% domestic heat, and consider the electricity produced as a freebee, or do they prioritize for electrical production, and consider the domestic heat generated?

WastePipe - Thread Starter

Alan73...I am not sure how much fuel I would consume per day. That is because a reefer engine is a specially designed engine designed for long life (30,000 hours) and to sip fuel. To do that they spin at about half the rpm of a regular diesel engine.

But that is good because a PTO generator is designed to spin the input shaft at slower RPM's too. They have a gear box that speeds the generator heads input shaft at a much higher speed to get the needed rpm's. PTO generators are different then most pto tractor work in that a person does not set the tractor at 2000 rpm to bushog lets say, instead, the tractor is throttled up to put the amperage gauge on the pto generator in the green zone. This matches the generator's output to the load it has on it.

I think I will consume about 1/2 a gallon of fuel per hour...

alan73 - Member

yes 540 rpm pto seems most common for tractors but the ones ive seen used required the tractor to run at a faster rpm so it was definitely using lots of fuel really doubt the 9n could run a 20kw probably not enough power but did see the test for the 8n on tractor data at 2.5 gallons per hour at 18 pto hp a diesel would do better but I think it will be way more than 1/2 gallon an hour.

WastePipe - Thread Starter

Yeah a Ford 9N was only 24 HP so it could only provide 17 KW's, but honestly that would power just about any home even at full demand, unless of course their electrical consumption was crazy.

My farm tractor is only 27 hp, and it can kick out 20 KW. About a month ago we were without power for 18 hours, and I used my tractor for back up power, operating at about 3/4 throttle and I used 10 gallons of fuel. So that is pretty close to a half gallon per hour., so that is where I based my fuel consumption. (But I do not know what actual consumption will be).

caddymac - Member

Slightly related, I have been waiting for years for domestic fuel cells for Combined Heat and Power (CHP) to hit the market. So far for North America it has been more experimental than anything.

WastePipe - Thread Starter

I always liked Crowley's 6 Stroke engine and wished he would have put it into production.

If I had that in this situation, I could go with an engine that was the same physical size, and yet match it up to a PTO generator that was twice as big since it has two power strokes in its 6 strokes.

I would have to do that because the resulting steam robs the engine of heat, but turns it into steam instead, and makes use of that steam. In order to get the cogeneration part of it, I would have to use electric heaters in my house instead of plumbing the engines hot water into my radiant floor heating system. BUT that would make installation a lot simpler because I would just have to run wires from the generator instead of having plumbing lines.

WastePipe - Thread Starter

Crowley's six stroke used a 4 stroke diesel as an engine block, but I wonder if it would be easier to modify a 2 stroke diesel engine block, but when adding the 3rd and 4th strokes to it, a person could inject the water and get the second steam power stroke?

I think that would make creating the camshaft easier since an engine maker would not have to make intake valves, just exhaust valves, diesel fuel injectors, and then the water injectors. Maybe it would make 2 stroke diesel have a come-back?

I kind of like 2 stroke diesels, and have a skidder that still has a 2 stroke diesel engine in it.

WastePipe - Thread Starter

I got found some pictures today so people can see the major components I am putting together to make this work...

This is the reefer engine as it was sitting for some 30 years inside a barn...

a dusty, complex reefer engine

WastePipe - Thread Starter

This is the radiant floor heating system the engines coolant system will eventually be plumbed into.

the red circled components are the control loop, and the loop in which the cogen will be plumbed. The green circled components show the metering valve, the plc and the relays to get the right amount of heated water to my floor loops. The blue circled components are for my floor loops of course.

radiant floor heating wiring setup

WastePipe - Thread Starter

This is my PTO generator I am marrying to the reefer engine first pictured....

PTO cogenerator shed

WastePipe - Thread Starter

This is a picture of my wife loading up our spare firewood/coal stove,

This boiler is kind of funny because I got it all hooked up, and then my wife decided she wanted to use the boiler room for a mudroom instead, so I ended up pulling it all out. Now it is just sitting, so I minds well plumb it into the cogen circuit in series since it is just kicking around, not doing anything.

woman in red dress and heels with homemade boiler

WastePipe - Thread Starter

I cannot seem to load the photo of my 3 phase generator I have been using for spare components to marry everything together, It does not really matter, it is kind of a dinosaur, but it will never make another volt, so I minds well use it to make my cogen go.

So those are all the components I am putting together to make this work. It should be a unique set-up when I am done.

beelzebob - Member

Is the sheet over the window to prevent anyone seeing your wife load wood into the stove?

WastePipe - Thread Starter

No, I was trying to block light from streaming through the window. I did however, put concrete blocks under the boiler to lift it up so that she would not have to stoop over quite so far to add firewood, or shovel in coal. I added tinwork around that, which you can see is painted red at the base of the boiler. I suppose not having on 4 inch heels would help too.

Pilot Dane - Group Moderator

Coal? Do you have a source of coal? I've come across some underneath a few of my rental houses but it's not easily available in my area.

WastePipe - Thread Starter

I can see where finding coal might be tough in the southern states, but where it gets cold, it would be pretty easy to find I would think. Here in the Northeast it is everywhere. It is also one of the cheapest ways to heat your home.

In this cogen system, I am putting in the wood/coal boiler, but in another house I have, I got a nice 1893 Pot Bellied stove. That burns wood or coal as well, and is a really nice stove for something that is 127 years old.

woman with old wood stove heater

WastePipe - Thread Starter

This whole cogen project started because of that wood/coal boiler though. I had it sitting around doing nothing, but realized I had a ideal outbuilding it would be perfect in. I just had to run plumbing lines to it.

With my back up generator, I wanted it to have its own engine so I did not put hours on my tractor while running it. That would be great if it had its own spot in a building too. Then when running it for 18 hours during a power outage I realized how much heat my tractor was putting out.

So it just made sense, if I was going to run plumbing lines for the wood/coal boiler, why not also plumb my generator coolant lines into the system as well! I mean they are right beside each other.

WastePipe - Thread Starter

With the cold weather, I have not been working on this project, but it warmed up, I had nothing else to do (retired) so I went back to working on it.

I had a tough time getting the wiring figured out, so I finally stripped everything back, replaced all the wiring circuits with redone wires, and managed to get a whole lot of nothing!

What the fanny pack?

I had power everywhere it should be, and when it should be there, so what was up?

I jumped the starter terminals and another whole lot of nothing!

WastePipe - Thread Starter

So I took a deep breath, grabbed some wrenches, and took off the starter.

It was apparent what the problem was as soon as I did that. The starter looked like the Mars on the inside: the RED PLANET! (Rust)

Holy suffering snotballs. Everything was froze up: the solenoid, the solenoid linkage, the main bearing, the Bendix drive...really, everything had to be frozen up? (Of course this engine has not been started in 30 years so that might be why).

So I broke it all free, sand papered everything down, lubed, oil coated, greased, cleaned...everything.

Then as I was putting the last part on, the brush hung up on the comm, and the forty year old plastic of one of the brushes busted off. Flew right past my ear! Really? Really? I spent four hours cleaning the starter and making it perfect, and it did that?

I got a nice starter shop nearby, so I will take it there. I was hoping to save $100, but that does not look like it will be the case. But oh well, I tried...

beelzebob - Member

You should remove the plugs, squirt some WD40 onto each piston and turn engine over by hand, More than .likely the piston rings are stuck as well as other parts. Search the web for info on things to do before attempting to start an engine that has not run in a long time. What you don't need are problems that can be avoided.

Pilot Dane - Group Moderator

It's also a good idea to remove the injectors and turn the motor over by hand to insure there isn't fuel or water in any of the cylinders. You don't want to do serious damage by hitting the starter on a hyrdo locked engine.

WastePipe - Thread Starter

Oh for sure, what you both say is great advice, so I in no way want to diminish that, but yes...I have already done that. :-)

I even opened up the engine a bit, and took a peek and was shocked at what I saw, the engine looked as if it was run yesterday! I think someone put oil in the top-end before storing it because it looked really nice.I then rolled the engine over by hand, and it was not even seized. I was sort of surprised, but not really, both because it sat for so long, yet the engine looked so good. But this is an engine designed to operate for 25,000 hours, and it has 2607 hours on it, so it has barely broke in. I know the back story on this engine, and it is not bad. The nameplate on the reefer unit said it was made in March of 1979, and I knew my uncle bought the reefer unit in 1988. He just bought it for a storage trailers, so that meant it was only used as a reefer for 9 years, and how many years it sat for resale, I am not sure. That made it worth salvaging, but then I dug the broken glass out of the hour meter so I could read it, and it was just rolling onto the seven of 2607 hours.

So it has not been run since at least 1988. We took it off the trailer then, shoved it into a workshop, and left it. So it has not been run for 32 years, but that is the beauty of old diesels, they are just waiting for someone to bring them back to life.

WastePipe - Thread Starter

I took the starter to the starter shop today and got more great news, and on several fronts.

They looked pretty skeptical at getting the starter rebuilt, but said they would do some investigating, and see what they could do with it. They also doubted it was a Kubota because it was such a robust starter. I had been told by a mechanic that Carrier Transicold had only used Kubota engines, and they had started importing engines to the USA about the mind-70's, so this made sense.

But after really looking around the internet, I deduced that it was actually a Perkins 4.108 engine. Since this was made from 1958-1992, there are plenty of them around, and plenty of parts. The first good news was that a new, high-torque, high-speed starter for this unit is only $139, and will be here in three days. It is nice to know that new parts can be bought right off the shelf for this unit.

The second was its size. I had thought it was around 30 HP, but it is almost double that at 55 horsepower. I only have a 20 KW generator for this, but it is nice to know I can power something bigger if I needed too.I found the service manual for this online, and downloaded it, so I am no longer doing this blind. Not that I really think I will have to get inside this engine. It really, really looked good.

Really all I got left now is to hook up the fuel system, which will be pretty expensive considering, then get the intake air, and exhaust outside of the building, but that is pretty simple. After that I got to mount the generator, and then machine out an adapter between the engine and generator.

WastePipe - Thread Starter

I just thought I might go and review some of the math on this to show how boilers, boiler horsepower, mechanical horsepower, and btu's all work math-wise to give a person an idea on how to calculate what their engine might do in terms of heating a home.

One horsepower equals 3/4 of a KW, or 750 watts. Since a tractor is rated by its PTO horsepower, my 27 HP Kubota can produce 20 KW, or 20,000 watts. (27 X 750 = 20250 watts or 20 KW)

But then there is boiler horsepower. 100 mechanical horsepower equals 7.5 boiler horsepower, or put another way; 13 times more powerful then mechanical energy. So my 55 hp Perkins Engine is equal to 4.23 boiler horsepower. (55 / 13 = 4.23)

A boiler horsepower is equal to 33,000 btu's, so my Perkins engine is basically a 139,000 BTU boiler. (4.23 X 33,000 = 139,590)

But energy can neither be created nor destroyed, only converted, so we know with an engine, 75% is converted to heat, and 25% is converted to mechanical energy. So my 139,000 btu Perkins engine is actually only producing 104,250 btu's. (139,000 X 75% = 104, 250 btu's)

But we also know that energy cannot be created nor destroyed, but energy can be dissipated; which is saying, it can be converted to an energy form that cannot be recovered. In this case, we know that 10% of that heat goes up the exhaust stack, and not into the water jacket of the engine. So my Perkins engine is really a 93,825 btu heater. (139,000 X 85% = 93,825 btu's).

So on the coldest days of the year, my home needs about 700,000 btus, so from all this I can determine, my generator needs to run at least 7.5 hours per day to meet my heating needs in the dead of winter, and less time in the shoulder seasons of course. (700,000 / 93,825 = 7.5 hours)

Keep in mind, this is prioritizing my engine for heat, and thus the electricity is just a free byproduct. Also remember that I have in-concrete-slab radiant floor heat, so I can save my heat, and do not need to produce heat on an as-needed basis.

WastePipe - Thread Starter

Of course, if a person wants to check their math, they can simply do it backwards, and use fuel consumption.

Since we know that a 55 hp engine consumes about 1.5 gallons per hour, and we know that diesel fuel has 131,000 btu's per gallon, we get 196,500 btu's per hour. If we subtract out for the loss of mechanical energy and waste going up the exhaust, or put another way, a 65% efficient heater (which is what an engine would be if it was graded as a heating appliance), we get a 127,000 btu heater/engine.

When doing these math checks, it is important to ask: does this make logical sense?

And this makes sense...this engine is between 93,000-127,000 btus depending upon throttle position which is dependent upon electrical load.

WastePipe - Thread Starter

I am still moving forward on this project, but slowly.

I did manage to pick up that new starter and get in on the engine. The start circuit worked, or at least sort of, it did until it came up on compression. That really did not surprise me as this is a high-torque, high speed starter so it needs some serious juice. My bulldozer was about the same size and so it used (2) batteries too, so I will need to add another into the mix.

In the meantime, I moved the engine 90 degrees so I could work on it easier. This better situated it in the building. I then found a bunch of tank hardware on another tank that I had kicking around, and so I managed to grab the legs, the whistle, the tank gauge, and fill pipe off that tank, and transfer it to this one. I then added a primary filter to the bottom port, and so the tank is ready to be filled.

I then turned my attention to the radiator, and mounted that in the wall of the generator shed. I managed to scare up enough hoses, pipes and clamps to get that in place, and ready for the engine to be wetted. I also mounted the air intake and filter house through the generator wall, but lack enough air induction hose, so I will have to try and scrounge that up.

Finally I managed to take the wiring. Before it looked horrific with wires and gauge lines everywhere. I took a screen door spring and stretched it from the engine to the wall where the starter controls are, then wire-tied the wires and gauge lines together, then swapped them all in protective wiring harness plastic. The spring will move with engine vibration, but allow the strain to be taken off the wires and gauge lines.

So it really is starting to change from a cobbled together unit, to something fairly nice looking.

Pilot Dane - Group Moderator

You put the radiator in the wall. Are you going with an electric fan or one driven off the crank?

WastePipe - Thread Starter

Yeah I mounted the radiator into the wall. Like you, I hemmed and hawed on which to do...mount the radiator to the wall, or mount it to the engine and run a plenum out through the wall. Because of the way the reefer unit was originally set up, it was easier to do it as I did.

I plan on getting (2) 10 inch electric fans.

For whatever reason, probably being a reefer unit, it has a very narrow, tall radiator. So twin 10 inch fans, mounted over and under will cool the radiator quickly I think, much better than an engine driven one.

How often I will run in radiator mode, I am not sure. Once the genset is all running, generator mounted, and cooling lines run to the house, I probably will just dump the excess heat into the house and cool the engine that way.

But until all that happens, I got an radiator hooked up. I will have to run a belt from the crank shaft to the water pump though.

As for electric fans, I got some other wiring to do as well. I am charging the batteries by a batter-minder so I do not get parasitic loads with an alternator set-up. Then I will have a circulator to send the engine coolant to the house. Then the electric fans. A three switch set up will enable me to snap those items on and off as needed.

WastePipe - Thread Starter

Just to be clear, I am using what I have because I got what I got, but if a person wanted a purchased cogeneration plant right off the shelf, I would suggest they do so differently than what I have going on.

My suggestion would be to buy (2) generators instead of one. In that way, a person could operate one engine, getting the heat they needed at less fuel consumption, and most of the time; the electricity that they need. If they need more electricity, they could put the second engine online, but only as needed.

Perkins makes a nice 2 cylinder diesel engine operating a 10 KW generator for $6500 for a 30,000 hour service life. Having (2) of these would give a person plenty of power and heat. They would have to buy a synchronizer when both are put online, but the cost for that is so low, that there would be a favorable return on investment from fuel savings in short order. They have a consumption rate of only less than half a gallon of diesel fuel per hour at half load.

Obviously if a person had a Tiny House and wanted to heat/power something like that, they could scale-down the (2) generators to match the heat/electricity load.

Note: While this project is for powering/heating a 2600 sq ft home, I have had Tiny Houses since the 1990's and have always really liked them.

WastePipe - Thread Starter

Well I finally went out and got some photos of the Cogenerating Unit I am building.

It bothers me to show pictures of it in a way because I always think, "I should do this before I post a picture of it, or I should do that", but then I end up having no start and finish pictures. In that sense, it is always good to show where you started, and the build along the way; no matter how bad it may look!

The only thing I think I will change is the tank arrangement. Right now it is inside the generator shed, which is good, but if it was outside it would give me more room, AND allow me to fuel up my tractor as well. It would also help me align the fuel lines a little better, and be easier for the fuel delivery man to get too. So a lot of benefit, except, fuel can gel when it gets really cold. But I guess there is ways to prevent that.

So this is what I got so far...

homemade cogenerator

cogeneration plant