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Hot topics: Homemade cogeneration plant

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Original Post: DIY Cogeneration Plant

WastePipe ̵

1; Thread Starter

So I got tired and decided I had all the essential components to make a DIY Cogeneration Plant, so for a week ago I started.

I've come further than I thought I would. The overall plan is to put a separate motor on my 83 amp / 20 KW PTO generator, and then divert the coolant on that motor into my radiant underfloor heating system. Along the way that I will lower in a wood / coal boiler, I have been in hibernation, so when all is said and done I will be able to produce my own electricity, while heating my house (hence the name cogeneration).

For a power take-off generator, I have a four-cylinder Kubota engine from a cooling unit that I kicked around and will start with. I managed to get them up to my generator room by myself by rolling the 800 pound unit up a slope on the tubes, and getting it all off to the engine. This meant removing the cooling parts, removing the cables and then starting to work my way back to get this thing running. Fortunately, it wasn't caught as badly as I thought it was.

The rebuilding started yesterday, with me making a new engine mount for the rear of the engine, then I grabbed a new starter panel of an old generator that I kicked around

Along the way I pulled in a 275 gallon fuel tank which I also kicked around. I ended up painting it a nice gray, and got it in place inside the generator shed … And then I also managed to get the wood / coal boiler into the generator shell. This is about 100 meters from my house and is 12 x 24 and well insulated, so it should work well.

The plan is now to go:

Get the construction circuit built

Few engine run from starting fluid

Attach the fuel tank and the wiring and the engine runs from off-road fuel

Put the PTO generator in position and get married with the cooling motor

Get the generator hard-wired to the house

Get the traction controls on the wood / coal boiler (chimney and forced intake air)

Plum wood / coal boiler for the genset engine

Plumb genset / wood house radiant floor heating

beelzebob Member

Good luck. I would first do a calculation to make sure I can heat the desired house volume (with losses) from an engine that has a specified coolant temperature and a necessary flow rate determined by the water pump. I would be leery of wood / charcoal aux boiler used as control of heat is at best raw. If the closed heating system became hot enough 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 think about the electricity cost you would generate. Then there is all the engine maintenance that must be done. You lose about 1/3 of the heat energy directly from the exhaust fumes and you do not collect 100% of the water energy either. You can really go nuts and do everything super efficiently and in combination with a heat exchanger, but you will still never have to buy electricity and burn oil in a boiler.

Now, if this is just a backup, or even a hobby, this is a good idea. If there was a power failure, you can heat your house with less total fuel than if you just run a heater from the generator. And sometimes it's fun to just play with generators.

Cogeneration is a subject I have studied very carefully and experimented with for several years, but it is almost impossible to make it worth the effort if you have power lines outside your house on a small scale. Much more suitable for companies, large apartment complexes and similar things. Personally, I would have kept the cooling unit together and turned it into a giant diesel-powered heat pump! It can potentially be run for less than with grid power for heating.

I would like to see some pictures of your installation.

Pilot Dane Group Moderator

Where are you? Burning diesel to generate your own electricity is one of the more expensive methods even if you recover 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 is usually done on boats / yachts so it is not a crazy idea. It is just an expensive way to power the lights if you have no other option.

zeezz Member

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

I agree that diesel prices are a bit ridiculous today, even off-road diesel. If your goal is low cost heat, you should watch the mini split (they can heat water too!) Or simply burn wood.

I've been doing 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 just $ 1.49 / gallon for "off-road gas".

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

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

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

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

This example is with gasoline, not diesel, but diesel currently costs more per BTU than gasoline does, so a diesel generator would have even worse numbers. Gasoline would actually make a reasonable heat fuel if you burned it in a boiler, but they don't really do that and it would be much more dangerous to hold on than other fuels.

WastePipe Thread Starter

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

In reality it is impossible to calculate, for a person would never run a cogeneration unit on that way.

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

It would allow me to drive the system gene at optimal times to power; most likely a 5 hour morning run and then a 5 hour evening run and then buy power from the national grid during the down times. This would mean purchasing power, not only at its cheaper off-peak hour cost, but also when my home consumes so much less power. By using it this way, a homeowner would achieve 100% of their domestic heat and about 75% of their electrical purchases from the tool: yet their genset consumes 60% less fuel as it does not work 24 hours a day. [19659005] It ends up being impossible to calculate because it depends on what a homeowner is comfortable to do. The more they match the heating and power needs of the gene sites to their lifestyle, the more efficient it becomes, but if they want to drop their nose at the power grid and be a standalone device, they will pay for it. [19659005] The biggest question I see when it comes to calculations is that everyone is done around the clock, and that doesn't have to be the case.

The second is that only one home CAN their own power and heat, does not mean that they HAVE . This will cost me about $ 500 to get in place; so just having ABILITY to do my own power and heat makes it worth doing. But this is my conclusion. Other homeowners may come to a different conclusion and be totally motivated in it.

zeezz Member

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

It won't work that way. To do that, you would need a very large amount of thermal storage besides the floor. Your floor will not be warm 14 hours a day and then it will not be 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 impossible to calculate because it depends on what a homeowner is comfortable to do."

Nothing is impossible to calculate, it is actually quite simple. 1. How much heat do you need? 2. How much electricity do you need? Both are simple calculations. If you do math, again, you will find this engine setting to be at least twice the cost of running like anything else.

The problem in most home settings is that you need more heat than electricity, so you will need thermal storage if you do not run the engine all the time. But you must also have a way to get electricity when the generator is switched off, so that you cannot disconnect from the grid. And you have to have a way to use electricity again when your generator turns on – should you just use a transmission switch and have each clock / computer reset every day when they lose power for a second? If not, you must also configure a very expensive inverter / battery. Then comes the summer and you basically need no heat except maybe a small amount of hot water. You haven't said anything about an exhaust heat exchanger, so you still lose 33% directly from the pipe, but they are also expensive to put together and never 100% efficient.

Don't try to blow up your bubble, but it won't work with those fuels on your scale. All it will do is burn money. I'm still not really sure what you're 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 today. They work in places that are not even sunny and give you power in the middle of the day when it is expensive. They also work if there is a power failure. You can also create warm water with solar panels, even in winter.

WastePipe Thread Starter

I disagree, but partly because some of your assumptions are not what I experience. [19659005] For example, my radiant floor heating system. Before I had reserve power, the house would only lose 1 degree a day. What I mean is that if the power was released for 9 days in a row, the temp in the house would only drop by 9 degrees. the amount of btus that 60 cubic meters of concrete can accept is quite amazing: slow to warm up, but also slow to cool down.

Another assumption is that 33% of the engine's heat goes out of the exhaust stack, This is not what engine production reports. They design their engines so that 95% of the heat from a naturally aspirated engine is transferred to the coolant system.

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

I came to that conclusion when we ran out of power for 18 hours, and when I checked my tractor now and then, realized how much heat was produced … and then wasted! So I started researching this and then realized that they have a name for it, cogeneration. Then I found out that Amish has been doing this for several years, and now the Energy Department encourages homeowners to enter the Northeast because of the high price of electricity here.

What I like is the low cost … at least for me … because I had all the major components like the spare boiler, diesel engine, generator and radiant underfloor heating system to tie in. I just had to put the components together. When I'm done, I'll probably have $ 500 tied into this when I'm done and can heat my home and run it in several ways:


On Grid

Off grid

Heating: [19659004] Propane

Diesel Fuel




zeezz Member

Sorry about buddy, you don't know what you are talking about. I could seriously teach a college course in this subject.

"Another assumption is that 33% of the engine's heat exits the exhaust stack. That is not what the engine manufacturer reports. They design their engines so that 95% of the heat from a naturally aspirated engine is transferred to the coolant system."

Error , wrong, wrong !! Put your hand on a hot exhaust pipe and tell it is 5% of the total heat! An average engine emits 1/3 as useful energy (electricity in this case) and 2/3 as heat. Any mechanical engineer can tell you this. The heat is almost evenly distributed between the engine coolant and exhaust. Different engines have slightly different efficiency, but no one has ever produced one that puts 95% of the heat energy in 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 gases. A gigantic, super-efficient installation that the power company can use for backup can get something like 40/30/30 energy split, but guess what, you have a really, really inefficient engine / generator installation.

As for the cost, If you just spent $ 500 on the entire installation, it won't last. I'm sure you think it will, but I can promise you if you try to run this thing every day you will fix it and make up with it every day. Properly reliable and efficient installation will cost many thousands of dollars and still burn too much fuel. Your installation will waste even more fuel than a good professional installation would.

I'm not trying to attack you, but the fact of the matter is that 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 devoted to this and everything can be calculated. You simply do not have a strong enough understanding of what you are doing to make it very good.

If this is just a way to stay warm and comfortable when the power goes out, it's fantastic. 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 get the wrong idea from the Department of Energy, I can assure you that they do NOT encourage anyone to take an old refrigerator apart and make a half-scaled diesel generator out of it. They do not encourage anything diesel powered anywhere. And the thing with Amish, is that they don't believe in things that are powered by electricity.

When it comes to heating your plate, try turning off your heat source for 14 hours a day and see how long it lasts. Have you even tried for more than a few days?

Prove me wrong. You did not actually submit any facts or photos in your installation. Boy, I wouldn't look stupid if you could post some facts and figures that show you save money or are efficient!

What do you write 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 the life I have found, it is not possible to prove a negative statement.

There is very little I can do when I quote something, and one person says, "I don't believe in you." At that point, all attempts to motivate the quote will be circular.

But your statement is the opposite of why I joined this site. We live in a world where people say they can't do things without buying it, and that's just not the case. I am on this site and mention this project so that people are encouraged and trusted to do things for themselves.

How does Generac create a genset? They take someone else's engine, mount it on a frame, put a generating head behind it, add some controls and it's a working generator. I'm doing the same thing. To say that it will be a changing nightmare is completely wrong. I happened to be a human being, and Generac also happens to have people assembling their components.

This applies not only to me but to someone on this site. Take a walk around Youtube and look for homemade inventions, and you'll see the amazing skills and technology that everyday people have done over the years.

My belief in people and not in original equipment manufacturers.

WastePipe Thread Starter

This is a project that many here can do. My parents installed a 14 KW Generac unit, and when ready they cost $ 6,000.

One person could buy a used refrigeration engine for $ 2000, a rebuilt power take-off generator for $ 800, add a fuel tank for $ 100 and make some cables and have more KW than my parents for less than half the money.

Let's say they didn't want to buy components and put them together. A homeowner could buy an old Ford 9N for $ 1,000, buy the rebuilt generator for $ 800, and have a 20 KW generator ready to go for $ 1800.

And it doesn't even take into account the "pure power" that the PTO generators provide compared to gas powered portable generators.

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

# 12

02-08-20, 06:40 PM




Connection Date: Mar 2010

Location : USA

Posts: 3,819

Received 44 votes on 42 posts

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

In principle, the idea is good. But I would design the system strictly for my electrical needs. Whatever heat that is released and that can be captured would be an added bonus.

  1. Build / install the system and make the electrical part work ..
  2. Add plumbing to direct the engine cooling water into the housing, either connected to an existing hydronic system inside or through its own plumbing and baseboard radiator loop inside [19659113] The recovered cooling water for the generator motor is still passed through the generator radiator, here connected in series and equipped with slats which vent the heat to the outside (from the generator cabin) preferably only when the interior of the house has reached the desired temperature.
  3. For the summer, manual valves are provided so that the generator cooling water skips the house heating pipes and goes only to the generator radiator.
  4. Set the thermostat for the house heating system so that it turns on minimally or maybe not at all when the generator supplies heat to the house.
  5. When mains power is on normally, turn off generator r and use other heating as needed.

No need to make any calculations regarding BTU, gallons per minute, exhaust gas losses, natural aspiration, etc.

You may know my setting an electrical system with coheat as opposed to a heating system with cogeneration. I don't think of the wood / coal heated boiler next to the generator as part of cogeneration, at least not if it throws away steam that also spins a turbine connected to a generator.

alan73 Member

seems like a good idea to capture the heat from the engine both the cooling system and the exhaust to increase efficiency, but I do not see that it is cost effective that you would need to reduce power generation by much more than 10 hours a day. really look at your fuel cost the more you have an inefficient engine that runs 10 hours a day how much fuel you need per day.

you would really need to have storage as a battery inverter set to be able to significantly reduce generator hours as this may be possible along with solar power.

WastePipe Thread Starter AllanJ … generator I have never had an engine, it is a PTO generator so it is designed to be operated with an agricultural tractor. They are designed for farmers to run their farms like milk tanks and whatever when the toolbar goes down. Since a person does not buy an engine with the unit, they are much cheaper.

The disadvantage is that a person must extinguish the reserve power if they use their tractor for other tasks, such as plowing snow from the driveway, or at least do so after the power restart. And another disadvantage is to spend all those extra hours on your tractor. The longest we have ever been without power here is 14 days in a row, but there are 336 extra hours on the tractor.

However, you make some very valid points. It's cogeneration, so what does a homeowner prioritize? 100% domestic heat, and consider the electricity produced as a standalone, or do they prioritize electrical production, and consider the domestic heat generated?

WastePipe Thread Starter

Alan73 … I'm not sure how much fuel I would consume per day. This is because a cooling engine is a specially designed engine designed for long service life (30,000 hours) and for sipping fuel. To do so, they spin at about half a revolution for a standard diesel engine.

But it is good because a PTO generator is designed to spin the input shaft at slower speeds as well. They have a gearbox that speeds up the input shaft of the generator head at a much higher speed to get the required speeds. PTO generators are different than most PTO tractor jobs in that a person does not set the tractor at 2000 rpm to bushog let's say, instead the tractor is shut down to put the current meter on the PTO generator in the green zone. This matches the output of the generator to the load it has on it.

I think I will consume about 1/2 liter of fuel per hour …

alan73 Member

yes 540 rpm Pto seems most common for tractors but the ones I have seen used demanded that the tractor run at a faster speed per minute so it definitely used lots of fuel really doubt that 9n could run 20kw probably not enough power but saw the test for 8n on tractor data at 2.5 gallons per hour at 18 pto hp diesel do better but I think it will be much more than 1/2 gallon per hour.

WastePipe Thread Starter

Yes, a Ford 9N was only 24 hp so it could only supply 17 KW, but frankly it would power almost all homes even at full demand, unless their electric consumption obviously wasn't crazy.

My agricultural 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 back-up tractor, worked with about 3/4 throttle and I used 10 liters of fuel. So it's pretty close to half a gallon per hour, so that's where I based my fuel consumption. (But I do not know what the actual consumption will be).

caddymac Member

Something related, I have been waiting for several 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 had it in production.

If I had it in this situation I could go with a motor that had the same physical size and still match it to a PTO generator that was twice the size because it has two power types in its 6 kinds.

I would have to do that because the resulting steam robs the engine of heat, but turns it into steam instead and uses that steam. To get a cogeneration part of it, I would have to use electric heaters in my house instead of turning off the engines hot water in my radiant underfloor heating system. BUT it would make the installation much easier as I would only have to run wiring 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 you add the third and fourth blows to it, would a person be able to inject the water and get the second type of steam power?

I think it would make it easier to create the camshaft because an engine manufacturer would not have to make intake valves, only exhaust valves, diesel fuel injectors and then water injectors. Maybe it would make 2-stroke diesel come back?

I rarely like 2-stroke diesel and have a skier who still has a 2-stroke engine in it.

WastePipe Thread Starter

I found some pictures today so people can see the most important components I put together to do this work …

This is the cooling engine because it sat for about 30 years inside a barn …

 a dusty, complex cooling engine

WastePipe Thread Starter

This is the radiant underfloor heating system that the engine coolant system will eventually move into.

the red circular components are the guide loop and the loop in which the cog will move. The green circulated components show the metering valve, plc and relays to get the right amount of heated water to my floor loops. The blue circular components are of course for my floor loops.

 heating lines for radiant underfloor heating

WastePipe Thread Starter

This is my power take-off generator that I first marry the cooling motor … .


WastePipe Wire Starter

This is a picture of my wife uploading our spare wood / charcoal stove, [19659128] This The boiler is quite fun because I connected everything, and then my wife decided she wanted to use the boiler room for a mud room instead, so I ended up pulling it all out. Now it's just sitting, so I'm probably going to put it in the cooking circle in series because it just kicks around, doesn't do anything.

 woman in red dress and heels with homemade forehead

WastePipe Thread Starter

I can't seem to load the photo on my 3-phase generator that I have used for spare parts to marry everything, it doesn't matter, it is kind of a dinosaur, but it will never make a new volt, so I can probably use it to get my boil going.

So that's all the components I put together to make this work. It should be a unique set when I'm done.

beelzebob Member

Is the sheet over the window to prevent anyone from seeing your wife load firewood in the fireplace?

WastePipe Thread Starter

Nej, jag försökte hindra ljus från att strömma genom fönstret. Men jag satte betongblock under pannan för att lyfta upp den så att hon inte skulle behöva böja sig så långt för att lägga till ved eller spade i kol. Jag lägger till plåtbearbetning runt det, som du kan se är målad röd i botten av pannan. Jag antar att det inte skulle hjälpa att ha klackar på 4 tum.

Pilot Dane Gruppmoderator

Kol? Har du en källa till kol? Jag har stött på några av mina hyreshus men det är inte lätt tillgängligt i mitt område.

WastePipe Thread Starter

Jag kan se var det kan vara svårt att hitta kol i södra säger, men där det blir kallt, skulle det vara ganska lätt att hitta skulle jag tro. Här i nordöstra är det överallt. Det är också ett av de billigaste sätten att värma ditt hem.

I det här kogensystemet sätter jag in trä / kolpannan, men i ett annat hus som jag har, fick jag en trevlig kamin från 1893. Som bränner trä eller kol också, och är en riktigt fin spis för något som är 127 år gammal.

 kvinna med gammal vedspisvärmare

WastePipe Thread Starter

Hela kogenprojektet startade dock på grund av den ved / kolpannan. Jag hade det att sitta runt och inte göra någonting, men insåg att jag hade en idealisk uthus som den skulle vara perfekt i. Jag var tvungen att köra rörledningar till det.

Med min back-up-generator ville jag att den skulle ha sin egen motor så jag satte inte timmar på min traktor när jag körde den. Det skulle vara bra om det också hade sin egen plats i en byggnad. 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.

WastePipeThread 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!

WastePipeThread 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! Verkligen? Verkligen? 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…


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 DaneGroup 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.

WastePipeThread 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.

WastePipeThread 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.

WastePipeThread 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.

WastePipeThread 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.

WastePipeThread 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 DaneGroup Moderator

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

WastePipeThread 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.

WastePipeThread 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.

WastePipeThread 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

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