Using a listeroid engine as an off-grid co-gen plant.

I wish I had pictures, but I did this more than 10 years ago, and didn't really consider documenting the process.

While I still lived in suburbia, I ordered a Lister 6-1 diesel engine knock-off from a company in India, through an importer recommended to me by someone on the Utterpower.com website.  I had a base machined from a piece of 1/2" thick mild steel plate, then proceeded to build this engine from a box of parts.  It took me about two months of Saturdays to get it all done, according to the directions I got from Utterpower.  Then I started it up, idled it for about 30 minutes, and shut it off.  Then it sat in my garage for most of the year, before I put it up for sale on Craigslist and sold it to a guy from Indiana.  With all this power failure stuff going on in California, I was reminded again about that engine, and why I thought would make a wonderful off-grid co-gen unit.  The engine runs very slow, for any modern engine, as it only runs from about 400 rpm up to about 650 rpm; so it can heat vegetable oil up using waste heat then burn it directly.  No need to convert any more to biodiesel than is required to start the engine and run to temp.

But there was another idea that I had with it, as the exhaust from the engine could also be used to heat domestic hot water, as well as contribute to the heat needs of an off grid home.  If attached to an automotive alternator for regulated 14.5 volts, the actual RPMs of the engine could be varied to the needs of the house.  300 RPMs when there was no need for power take-off, but it was winter so the heat from idling wouldn't be lost.  400 RPMs when a small charging current was needed to top-off the house battery bank, because it's winter and the sunshine is too short to do the job.  And 650 RPMs when the power demand is high, and the large invertor is in use; to run the washing machine, because there's a party and all the lights are on, or because there's work to be done in the shop.  An air compressor could also be attached to the engine in the same way as an alternator.

But the co-gen part comes, in my idea, from forcing the exhaust to push down through the center pipe of a gas water heater (with the burner gear removed) then out the bottom and into a pvc pipe buried in the ground, then outside.  Such an engine could also be connected to a traditional hot-water radiator, by way of a thermosiphon, to move the heat in the coolant into the living space.  The engine itself could be in a basement, or outside of the living space, so long as it was protected from the elements.

I know from experience that these engines are not particularity loud even with a cheap lawnmower muffler, and the slow sound of the engine is not at all offensive to the human ear; but by cooling the exhaust, then pushing it through the ground for some extra distance inside of a plastic pipe that can flex somewhat, the note that comes out the other end will be small.  You likel wouldn't be able to hear it running unless you were standing next to the engine or standing on top of the final exhaust exit.

Maybe I should order another kit.

That is interesting, I have never heard of those engines.

A similar off-the-shelf engine that people can get is a Refrigerator diesel engine as well. They run the refrigerator units on tractor trailer trucks and run at half speed compared to most engines, but are designed to run for up to 50,000 hours with no human interaction. That is they have low oil, and over temp cut offs because they know truckers are not watching them at all. mechanics often pull them apart and they are so worn out that they do not even know how they run, but they do.

I still have an interest in biogas, and now that I am not sheep farming, I have 107 acres of open land that is doing nothing. I always wondered if I could raise a type of crop that could produce biogas enough to cut down some of my other expenses. Electricity is one, but heating my home uses more energy than electricity (I live in Maine).

I do have radiant floor heat though so I could direct my Gen-Set's coolant water through to my home and heat my floor that way. Even buying diesel fuel the math almost works. If I sell to the power company my excess power, it would really work, but of course cheaper fuel alternatives also sound great. I am just not sure how the math would work on raising a crop, then converting it to biogas would all work, but I would think there would be significant energy in 107 acres of biogas derived from something?

Listeroids were the dream machine for off griders. I would say they have fallen out of favour for a few reasons. They do not meet the EPA emissions standards and as far as I know cannot be imported into the US anymore. Next is the expense and weight; they are incredibly heavy and require virtually their own room. Finally the falling cost of solar panels has made large arrays feasible reducing the importance of the generator element of an off grid home to something that can be handled by a smaller cheaper unit. I like them myself but an inverter generator will greatly outperform it efficiency wise. There is the Cogen element but again if its only running from time to time due to the greater solar production the cogen element becomes less important.   I alway liked the micro cogen site myself. anything you ever wanted to know about old iron is there. Some incredibly knowledgeable people    www.microcogen.info
This company makes a modern version of a biodiesel cogen unit using kubota engines   http://www.microcogen.ca/

I am pretty fortunate in that the heat side of what I need is already built. For me this is a form of hydronic heating. It basically is the two loop system I have in place, with a metering valve to help draw or temper what I have for heat in the primary loop. In short, all I need is hot water; 100 to 212 degrees, it does not matter how it is heated...solar, wood, pellet, coal, propane, oil, etc...it just has to be 100 degrees or above. As long as it as at the temp, then the main propane boiler will not come on.

My local dealer still has Lister Engines for sale. I would have an interest in them, but my dealer only showed a 6 HP version, but maybe they still have them from pre-ban days??? I am not sure, being in kit form also muddies the importation waters somewhat.

What I like about cogen is that for me, it is so easy to do. About the only real cost is in laying the tubing from barn (where I would house to generator) to my boiler, a distance of about 100 feet. I have the engine, generator and even fuel tank (275 gallons) ready to go. I am a little overpowered at 63 Hp for a 20 KW generator, but that is just excess fuel consumption. The only real complicated part is tying my excess power in with the grid. That is where I would recoup my money (return on investment), but if I did not do that, my cost would be incredibly cheap.

Travis Johnson wrote:I am pretty fortunate in that the heat side of what I need is already built. For me this is a form of hydronic heating. It basically is the two loop system I have in place, with a metering valve to help draw or temper what I have for heat in the primary loop. In short, all I need is hot water; 100 to 212 degrees, it does not matter how it is heated...solar, wood, pellet, coal, propane, oil, etc...it just has to be 100 degrees or above. As long as it as at the temp, then the main propane boiler will not come on.

My local dealer still has Lister Engines for sale. I would have an interest in them, but my dealer only showed a 6 HP version, but maybe they still have them from pre-ban days??? I am not sure, being in kit form also muddies the importation waters somewhat.

What I like about cogen is that for me, it is so easy to do. About the only real cost is in laying the tubing from barn (where I would house to generator) to my boiler, a distance of about 100 feet. I have the engine, generator and even fuel tank (275 gallons) ready to go. I am a little overpowered at 63 Hp for a 20 KW generator, but that is just excess fuel consumption. The only real complicated part is tying my excess power in with the grid. That is where I would recoup my money (return on investment), but if I did not do that, my cost would be incredibly cheap.

Travis what propane boiler are you using? Is there a write up somewhere about your system?  I'm probably building again in the next year or two and would love to incorporate more of that. I run my radiant off of a backup loop off the propane water heater with the wood stove doing most of the work. There efficiency of the propane direct vent is not great though.  Next house I think will have a large reservoir of hot water heated by wood outside to work in tune with my charcoal making for gasification. The wood stove charcoal making method is efficient but I cannot get the volumes of charcoal I see myself using. Wood to charcoal, charcoal to electricity might be a good path for you as well.
Cheers,  David

I use a Munchkin Wall Hung Boiler.

I almost went with a propane hot water heater too, but the guys at the store told me to go with a boiler even though it cost $1800 more. They had to explain it to me (3) times before I understood why using the boiler was a much better alternative.

As for the system itself, it is very efficient and simple in concept.

It basically has two loops, the main boiler loop and then the loops going to and back from my floors to manifolds with flow control valves. In between the two loops is a metering valve, which is a silly name because all it is, is a variable speed circulating pump. This metering valve (circulating pump) is hooked to a PLC that monitors various functions:

Slab temp
Returning water temp
Outgoing water temp
Outside temp
Individual zone temps

Every minute the computer (plc) calculates what the temp is outside, what the water running through the floor should be, and what the returning water temperature is, and what the zone temp is. The PLC then sets a target temp for the water running through the floor.

The PLC meets the target temperature by pulling varying amounts of hot water from out of the main boiler loop. All the boiler does is make sure that loop is always between 100-150 degrees. That is all the boiler does. The metering valve (variable speed circulating pump) increases, or decreases the rpm in this pump to get the target temperature.

The target temp is so efficient that my zone valves never shut on or off. What I mean is, the computer is so accurate that if it says it need 76 degree water to heat the home for a 35 degree day outside, it does. Whatever I set my thermostats for, it typically is 1 degree + or = what I set it for. As the temp outside gets down, the water running through the floor goes up to make up for the cold outside, and vice versus, the water in the floor goes down if it warms up outside. It does this every minute so it stays right up to temp with what is happening for weather.

I do have zone valves, an a zone valve relay with priority, but they never come into play. They would if the zone got to warm, but the PLC controls that through water temperature running through the floor.

To gain a little more efficiency, I programmed the PLC to only operate the boiler if there is (2) calls for heat on 2 separate zones. That way if there is a cold spot by a thermostat the boiler does not fire up just for one zone. It takes 2 out of 3 zones to fire the boiler. I gained some more efficiency by lowering the default temp to 0 degrees. At that temp, because it is so cold outside, the boiler no longer tries to regulate temperature by how cold and warm it is, and so at 0 degrees, it just pumps 100 degree water through the floor. Normally it is set at 10 degrees, but this is Maine, it gets down to zero or below a lot!

The downside to my system is; the circulating pumps (one for the main boiler loop, the variable speed one called a metering valve, and the circulating pump pushing water through my floors) always run because the temp of that water controls the temp in my floor, not coming on and off with zone valves like conventional heating systems. So it costs me $10 more per month in electricity.

So you see it is pretty simple; the system is the smart part and the main boiler loop is dumb...it just has to be between 100-150 degrees. So when I plumbed the main loop, I added two valves so that I can heat that water with anything...a wood boiler, solar, compost heat, a cogen...again as long as that water is 100-150 degrees it could be heated any way. That is the reason why I added the metering pump controlled by the PLC. Without it, if I had wood heat, the water would be too high. I cannot circulate water above 120 degrees through concrete, so I would need to knock it down with cold water. I really dislike that concept...why heat water, just to cool it back down? The only other way to do it is, get a PLC that pulls the right amount of hot water out of the main boiler loop exactly when it is needed, and exactly how much is needed.

In the fall, at start up, my slab is 57 degree, and the metering valve cannot get enough hot water to meet demand, so it runs at 100%, but later in the season when the slab is warmed up, and it just needs to maintain temperature, it simmers along at 30%, that is why that circulating pump...the metering valve...has to be variable speed. It also has 3 manual speeds so I could set it at A setting 0-100%, then b-setting 0-100% and c setting at 0-100%. I had to do that because I had no idea what I needed for flow. Now that the system is set up, it is "balanced" and it runs itself.

It is all really simple. I will see if I can get a picture so you can see how simple it is. I am sure if you study the photo of my system, you could throw one together pretty easily. It is not cheap for the various components, I spent $10,000 13 years ago, but I am heating a 2600 sq foot home for $1700 per year using a 80,000 btu boiler. In Maine that is unheard of! But you buy it once, and it saves you money for years in fuel costs.

I found a picture:

The Red circled components show the boiler and its main boiler loop...note the valves, in this case going to a wood boiler
The green circled components are the metering valve (pump) and the plc (tiny green box).
The Blue shows the controls for the loops going through my floors. The box with all the wires is because the cover was off the zone control relay

So it is all pretty simple as you can see.

The only real way I could make this more efficient is, if I could add an Artificial Intelligence aspect to the PLC. If I had that, the computer would then take the computerized weather forecasts in digital language off the internet, and then adjust itself to what was coming.

I would program it so that IF a warm spell was forecasted for the next 12-24 hours, it would scale back on the heat knowing it was going to get warmer in the next few hours. Basically it would allow the heating system to ANTICIPATE incoming weather. Instead of it trying to heat the zones to 70 degrees at all costs, it would just say, "oh, warm weather is coming so I can cut back and allow the warm slab to heat the house for the next day or so."

Of course it could go the other way too, and that is ramp itself up knowing colder weather was coming in. I would not program it to do that though, because while it would make for a more comfortable home, it would consume more fuel.

But hopefully I have shown how fairly smart my heating system is, and how it could be even better. But that is what I love about hydronic systems over air, we got the technology to control where hot water goes and when, and that is super efficient! And it is all so simple. I am not even a boiler guy and I figured it out so I know anyone can.

That is a nice piece of equipment... Did the PLC brain come programmed or is it custom? The rest is standard gear I like that. I control mine much more simply but I have less square footage and less control. A stainless hot water loop runs through the wood stove and is plumbed into the radiant loops which run off a circulator and runs 24/7 in the winter. There is a central thermostat that when there is a call for heat, because the wood stove has slowed down, it turns on the circulator to the hot water tank which goes through a plate exchanger in the radiant loops. Zone control is done through simple flow control valves with flow meters adjusted manually to equalize temps and left alone once adjusted... I like yours far more control. I run the circulators on the solar powered circuits of the house so there is no interruptions. That was why we chose the direct vent originally due to the limits we had on electricity when we were fully off grid...
David

It is just a plain ole Taco PLC...it has probably been updated now to something better, but it does work.

Like any PLC, you can just adjust the parameters as you see fit. Like anything, I just read the manual and then adjusted a few things to make it a bit better for me.

But it really is no different than what you have by the sounds. A lot of the controls were put in place because I did not know what I needed for adjustment. Like the flow controls on the individual pex loops in the floor. If I had run the same length loops on all of them, I would not have had to have flow controls. Live and learn...

But like yours, once it is set, it really is to be left alone. The only issue I had was trying to "balance" my system when I added another zone. The first part of my house was built in 1994 which was before radiant heat became big. After seeing how nice the back part of the house was, I HAD to add radiant to the first part! It took me a bit to balance everything out to handle the 50% increase in load.

What I really like about these systems is that you can add anything and everything. I added a wood boiler, but you could put tee's in and add solar...or compost heat...or the coolant lines off an engine. As long as the water temp is above 100 degrees, it will prevent the propane boiler from coming on. And since circulators do not act as check valves, there is no other plumbing to do, the computer in the boiler is smart enough to whether or not it should come on or not.

I am no boiler tech by any means, but there is a program here for what they call "Disadvantaged Farmer's" because through no fault of my own, farming is tough. For me it was cancer that caused me to struggle at farming, so I must do something else now. We talked about college. My career advisor wanted me to go to a 12 week course on boilers, but here in Maine, that does not allow for a "Solid Fuel Boiler's License". That is what I want, I do not want to just clean a propane or oil boiler...this is Maine, everyone heats with wood! After explaining it, he admitted that the 2 year degree would be a better fit.

When my father installed his Pellet Boiler, he could only find (2) people in our area that could do it, and they each quoted him $7000 to put their name on it. He ended up doing it himself, but there is a huge demand for Solid Fuel Boiler Guys. I think it would be neat to legally be able to do anything from a boiler like what we got, to installing Rocket Mass Heaters.

Travis Johnson wrote:

My local dealer still has Lister Engines for sale. I would have an interest in them, but my dealer only showed a 6 HP version, but maybe they still have them from pre-ban days??? I am not sure, being in kit form also muddies the importation waters somewhat.

The Lister 6-1 was one of the oldest designs for the Lister Engine Company, and they stopped producing it in the 60's, I believe.  So if your local dealer has Listers, they are either more modern models (which run at faster RPMs, are louder, etc) or they are knock-offs from India or China. India in particular doesn't honor the Lister patents anymore, so there are many 'legit' manufacturers of the 6-1 design; but literally zero 'legit' exporters.  I'd love to know where this local dealer actually is, though.

What I like about cogen is that for me, it is so easy to do. About the only real cost is in laying the tubing from barn (where I would house to generator) to my boiler, a distance of about 100 feet. I have the engine, generator and even fuel tank (275 gallons) ready to go. I am a little overpowered at 63 Hp for a 20 KW generator, but that is just excess fuel consumption. The only real complicated part is tying my excess power in with the grid. That is where I would recoup my money (return on investment), but if I did not do that, my cost would be incredibly cheap.

Th 6-1 stands for 6hp and one cylinder.  There's also a 12-2.  In either case the horsepower rating is at 650 rpms, but the engine can produce power at *much* slower speeds.  This engine design had an incredibly low specific consumption rate, despite it's very simple design.  So low that it takes quite a bit of modern control technology to match it even today.  What this could mean for an off-grid set-up (during the heating season) is that, once the engine was up to temp itself (as long as there wasn't too much taking of the heat for other reasons) this engine could idle at a very slow speed, running on straight vegetable oil, consuming very little until it's needed for power; then it could be run up to 550-650 rpms to drive a 100 amp automotive alternator for a period of time without much losses at all.  Even some small fraction of the fuel can be propane, if that's what you wanted to use.  The goal is to not have enough over production (of electricity) to bother with feeding into a grid at all.  Better yet, this 6-1 could be the baseline power system for a small, intentional community; rather than just a single off-grid homestead.  There's no way that the waste heat of a 6-1, even running 24-7, could supply the domestic heat demand of a community; but it could provide for the lights and pumps necessary for that community to share the heat output from an 8" rocket-mass-water-heater.

Yes, you are right, now that I read their advertisement, it says "Lister Like Engine Kits"...so they are knock-offs. Still, it is nice to know that you can still get them. And you are right, they have both a 6 HP and 12 HP engine. The 6 HP was $1600 though, without many add on attachments.

Lister Engine Maine

I also noticed that there is a lot of ways to get off the shelf slow speed generators. They have a Kohler 5000 watt 1000 rpm Generator that consumes 19 gallons of fuel every 79 hours for instance. Still a little small, but there are others too like Kubota and Ford...really depending on what you want to get.

One thing to keep in mind though with generators is that they are always rated by wattage, but the real limiting factor is actually amperage. For instance, my generator is a 20,000 watt (20 kw) generator, but it only has 83 amps, and that is what I quickly run out of. That is only (4) 20 amp circuits running after all. Actual draw-down by the load is different at varying times, but you see what I mean, my wife fires up her electric wall oven, and it brings the generator to its knees.

Travis Johnson wrote:Yes, you are right, now that I read their advertisement, it says "Lister Like Engine Kits"...so they are knock-offs. Still, it is nice to know that you can still get them. And you are right, they have both a 6 HP and 12 HP engine. The 6 HP was $1600 though, without many add on attachments.

Lister Engine Maine

I also noticed that there is a lot of ways to get off the shelf slow speed generators. They have a Kohler 5000 watt 1000 rpm Generator that consumes 19 gallons of fuel every 79 hours for instance. Still a little small, but there are others too like Kubota and Ford...really depending on what you want to get.

I disagree on the highlighted point.  With regard to off-grid co-generation, smaller is generally better.  You want the smallest co-gen setup that can run your single largest running load; and depend upon your battery bank & inverter to take up any slack, including the additional start-up amperage of that largest load. This is a departure from traditional backup generator calculations, because you'd generally want 150% to 200% of your largest load, so that the gen-set can start & run your largest load as well as lights and other smaller operations during an outage.  But an off-grid co-gen setup isn't intended to carry you through the dark times of a grid outage, but as a regular contributor to your normal energy use pattern during the heating season.  This line of thinking forces you to coordinate your electricity usage so as not to outrun your co-gen plus solar array plus battery storage; but the longer period of time that the co-gen can be run at a productive cruising speed, the more efficient it is at doing all it's functions; in part because start-up from cold to warm running is a large portion of your "lost" energy (although you can still recapture most of that heat by drawing heat off the warm engine following shutdown).  For example, you might get 4 hours of insolence (energy equivalent of full-sun) during a typical winter day; so you don't want your co-gen running while the solar panels are doing a decent job keeping the lights on and the battery bank over 80%; but once the sun drops below the horizon, you need more heat and more power for lighting, etc.  So you might wait for an hour or so after sundown, then start the co-gen while the washing machine or dishwasher is running, leave it running while showers are taking place (peak domestic hot water demand) and shut it down once all the demanding housework is done and the kids are ready for bed.  So the co-gen runs at productive speed for about 3 hours each winter evening, providing only a portion of the heat and power demand while running, but is fully utilized while running (even the power produced between wash cycles is stored in the battery bank, to be used by the refrigerator overnight).  Thinking along these lines, with the co-gen as a part of your total energy system intended primarily for winter, allows you to design your solar array ideally for summer.  So your solar array can be smaller, as compared to an array intended to do the full job either year round or as a '3 seasons' design.  Also, your battery storage can be smaller; because you're no longer constrained by the 3-days of storage rule, since if the battery storage that you can afford ever gets too low to safely run the refrigerator overnight, you can start up the co-gen for a few hours anyway.  Yes, this means that long term storage of at least some diesel or bio-diesel fuel would be a necessary part of your household planning; and you might never be completely independent of society for your energy sources this side of TEOTWAWKI; but you'd still have the freedom to expand your solar array as events permit, slowly reducing the need to run your co-gen; until ultimately you can sell it to another, less established, off-grid household in your area.

Travis Johnson wrote:
One thing to keep in mind though with generators is that they are always rated by wattage, but the real limiting factor is actually amperage. For instance, my generator is a 20,000 watt (20 kw) generator, but it only has 83 amps, and that is what I quickly run out of. That is only (4) 20 amp circuits running after all.

I'd wager that is 83 amps at 230 volts single phase, with a neutral tap in the center to allow 115 volt appliances to run. So if all your loads are 115 volts, a trained electrician can derive eight 20 amp circuits from that source. Actually, household circuits are generally designed to be protected at 15 amps, but "derated" to 80% for single loads that consume an entire circuit, so legally limited to 12 amps; so a 20KVA genset can legally & functionally support a 115/230 volt, single phase household power panel with up to 14 circuits if they are all limited to 15 amp breakers. Of course, this doesn't mean that you can, or would want to, turn everything on at once; these calculations assume a bit of "non-coincidence of loads".

Actual draw-down by the load is different at varying times, but you see what I mean, my wife fires up her electric wall oven, and it brings the generator to its knees.

This brings up two potential issues...

1) Have you considered switching to gas/propane? You could eliminate a huge demand load from your electrical system, and your co-gen or backup gen-set need could be lower.  Electro-resistive heat is "expensive" in a lot of different ways.

2) Is your wife's electric oven wired for 115 volts?  This would seem unlikely, as such a high demand load would be better served wired as a 230 volt device.  Unless your grid power service is only 115 volts nominal, and not a 115/230 volt service.  I know that 115 volt only services exist, particularly at the extreme ends of rural electric service, but in 25 years working as a licensed electrician, I've literally never seen such a household grid service myself.  If it is, indeed, wired for 115 volts; then the gen-set is bogged down by it primarily because it can only use half of the generator coil at a time, and if anything else draws from that same side of the generator coil, the gen-set will overload.  Balancing the amperage across both sides of the generator coil will reduce your engine's loading a little, as well as reduce the odds that the gen-set is overloaded and 'trips' out.

Without a question, alternative power is a different lifestyle choice unto it's own. I could easily handle that sort of lifestyle, and flip switches as required, but there is no way my wife and kids could. Back when we had a 4000 watt back up generator they just did not understand the concept that it could not do all that the grid-based power could. They were forever using this or that, and I was like, "you cannot do that!"

With 20 KW and 83 amps, we are still a little limited, although it would seem that would not be the case. My wife's wall oven will bring the generator to its knees, as well as the electric hot water heater. We do not run either while on generator power. We could probably flip switches, and divert all the power to the hot water heater, or the wall oven and be fine, but it is just easier not to.

We were on a program switching as many appliances to propane as we could, and were doing pretty well with that until we switched to the Tiny House, and then after a year, moved back in here. When we did that, we brought our propane appliances with us, and brought the electric appliances from the Tiny House over here. Now having moved back, we did not bring the propane appliances back. We can, and it would help, but we ran into issues with that too.

The cost was probably cheaper for such things as the kitchen stove, the clothes dryer, and the boiler; but because demand was higher, we had to have a big propane tank. That was fine, except the propane company will not fill the tank unless it is below 15%. That meant we got a HUGE bill when they showed up. I asked them too top it off every other week or so when they drove by on their weekly route, but they said they could not do that, but it was really tough to get a huge bill all at once. With electric, they just charge you what you use every month, so it is a bit easier to take. And with propane, it is all or nothing too. You cannot just go down to the local store and dump a few gallons of propane in the tank like you can with oil if you are running low; you are very much at the mercy of the propane delivery company.

I am not saying I have anything against propane. At some point I will bring our old propane appliances back, and when the electric water heater dies, I will replace it with a boiler mate so I have propane domestic hot water. I cannot do anything about the wall oven though, for whatever reason, they do not make them in propane or gas that have any size to them, they are electric ovens only....and do they ever take some juice!! WOW!

One of the biggest issues I am facing now is what to do with the apartment we are adding onto this house. Katie thinks it will just be intermitenly used, but we have four children, and because the way things are now in society, I do not see them leaving the nest at 18 years old like I did. So for that reason it will be fully furnished with a kitchen, bathroom with washer and dryer...the kids can do their own laundry, I am not going to have their mother do it for them.

But with heat, cooking, hot water, and clothes dryer...do I just use what I have kicking around which is all electric, all new appliances, or do I switch to propane? And do I tap into a new propane tank, or just use the old one since I am assessed a yearly fee for every tank I have? It would be kind of nice to tell my daughter and her husband to keep her own darn propane tank filled, but I suspect we would have to keep it filled for them anyway! We all know how that goes.

The real question is what do I do for heat. I have to run new concrete floors anyway, so do I run pex through it and heat by radiant floor heat? I would have to run a whole new manifold and set of controls, but my boiler might produce enough btu's to heat the apartment. It would be a lot easier though to just install a Reneai Heater instead, not to mention being a lot cheaper. The only issue with that is, it would be heated 100% by propane. With radiant floor heat I could use the propane/wood/coal/geothermal set up I got now.

So I got a lot to think about with this new renovation (mother in law apartment).

Creighton Samuels wrote:

Travis Johnson wrote:Yes, you are right, now that I read their advertisement, it says "Lister Like Engine Kits"...so they are knock-offs. Still, it is nice to know that you can still get them. And you are right, they have both a 6 HP and 12 HP engine. The 6 HP was $1600 though, without many add on attachments.

Lister Engine Maine

I also noticed that there is a lot of ways to get off the shelf slow speed generators. They have a Kohler 5000 watt 1000 rpm Generator that consumes 19 gallons of fuel every 79 hours for instance. Still a little small, but there are others too like Kubota and Ford...really depending on what you want to get.

I disagree on the highlighted point.  With regard to off-grid co-generation, smaller is generally better.  You want the smallest co-gen setup that can run your single largest running load; and depend upon your battery bank & inverter to take up any slack, including the additional start-up amperage of that largest load. This is a departure from traditional backup generator calculations, because you'd generally want 150% to 200% of your largest load, so that the gen-set can start & run your largest load as well as lights and other smaller operations during an outage.  But an off-grid co-gen setup isn't intended to carry you through the dark times of a grid outage, but as a regular contributor to your normal energy use pattern during the heating season.  This line of thinking forces you to coordinate your electricity usage so as not to outrun your co-gen plus solar array plus battery storage; but the longer period of time that the co-gen can be run at a productive cruising speed, the more efficient it is at doing all it's functions; in part because start-up from cold to warm running is a large portion of your "lost" energy (although you can still recapture most of that heat by drawing heat off the warm engine following shutdown).  For example, you might get 4 hours of insolence (energy equivalent of full-sun) during a typical winter day; so you don't want your co-gen running while the solar panels are doing a decent job keeping the lights on and the battery bank over 80%; but once the sun drops below the horizon, you need more heat and more power for lighting, etc.  So you might wait for an hour or so after sundown, then start the co-gen while the washing machine or dishwasher is running, leave it running while showers are taking place (peak domestic hot water demand) and shut it down once all the demanding housework is done and the kids are ready for bed.  So the co-gen runs at productive speed for about 3 hours each winter evening, providing only a portion of the heat and power demand while running, but is fully utilized while running (even the power produced between wash cycles is stored in the battery bank, to be used by the refrigerator overnight).  Thinking along these lines, with the co-gen as a part of your total energy system intended primarily for winter, allows you to design your solar array ideally for summer.  So your solar array can be smaller, as compared to an array intended to do the full job either year round or as a '3 seasons' design.  Also, your battery storage can be smaller; because you're no longer constrained by the 3-days of storage rule, since if the battery storage that you can afford ever gets too low to safely run the refrigerator overnight, you can start up the co-gen for a few hours anyway.  Yes, this means that long term storage of at least some diesel or bio-diesel fuel would be a necessary part of your household planning; and you might never be completely independent of society for your energy sources this side of TEOTWAWKI; but you'd still have the freedom to expand your solar array as events permit, slowly reducing the need to run your co-gen; until ultimately you can sell it to another, less established, off-grid household in your area.

I am not sure on this though.

IF I am using an engine to co-gen both electricity and heat, I would think the heat would be the harder of the two demands to meet.

My home takes about 5 gallons per day of propane to heat in the heart of the heating season which is about 455,000 btu's per day based off 91,000 btu's per gallon of propane.

Assuming some losses, it will take at least 10 gallons of diesel fuel consumption per day to get that with engine heat. So while it would seem fuel economy is of great importance, in this case it really is not because I am going to need at least 1 million btu's per day, and probably closer to 1.5 million btu's. I could drastically change my lifestyle so that the small gen-set listed meets my electrical needs, but I am not sure it will provide enough heat. My calculations show that 5000 watt engine will provide around 3/4 of a million BTU's per day. I am not sure that would be enough.

Travis Johnson wrote:

Creighton Samuels wrote:

Travis Johnson wrote:Yes, you are right, now that I read their advertisement, it says "Lister Like Engine Kits"...so they are knock-offs. Still, it is nice to know that you can still get them. And you are right, they have both a 6 HP and 12 HP engine. The 6 HP was $1600 though, without many add on attachments.

Lister Engine Maine

I also noticed that there is a lot of ways to get off the shelf slow speed generators. They have a Kohler 5000 watt 1000 rpm Generator that consumes 19 gallons of fuel every 79 hours for instance. Still a little small, but there are others too like Kubota and Ford...really depending on what you want to get.

I disagree on the highlighted point.  With regard to off-grid co-generation, smaller is generally better.  You want the smallest co-gen setup that can run your single largest running load; and depend upon your battery bank & inverter to take up any slack, including the additional start-up amperage of that largest load. This is a departure from traditional backup generator calculations, because you'd generally want 150% to 200% of your largest load, so that the gen-set can start & run your largest load as well as lights and other smaller operations during an outage.  But an off-grid co-gen setup isn't intended to carry you through the dark times of a grid outage, but as a regular contributor to your normal energy use pattern during the heating season.  This line of thinking forces you to coordinate your electricity usage so as not to outrun your co-gen plus solar array plus battery storage; but the longer period of time that the co-gen can be run at a productive cruising speed, the more efficient it is at doing all it's functions; in part because start-up from cold to warm running is a large portion of your "lost" energy (although you can still recapture most of that heat by drawing heat off the warm engine following shutdown).  For example, you might get 4 hours of insolence (energy equivalent of full-sun) during a typical winter day; so you don't want your co-gen running while the solar panels are doing a decent job keeping the lights on and the battery bank over 80%; but once the sun drops below the horizon, you need more heat and more power for lighting, etc.  So you might wait for an hour or so after sundown, then start the co-gen while the washing machine or dishwasher is running, leave it running while showers are taking place (peak domestic hot water demand) and shut it down once all the demanding housework is done and the kids are ready for bed.  So the co-gen runs at productive speed for about 3 hours each winter evening, providing only a portion of the heat and power demand while running, but is fully utilized while running (even the power produced between wash cycles is stored in the battery bank, to be used by the refrigerator overnight).  Thinking along these lines, with the co-gen as a part of your total energy system intended primarily for winter, allows you to design your solar array ideally for summer.  So your solar array can be smaller, as compared to an array intended to do the full job either year round or as a '3 seasons' design.  Also, your battery storage can be smaller; because you're no longer constrained by the 3-days of storage rule, since if the battery storage that you can afford ever gets too low to safely run the refrigerator overnight, you can start up the co-gen for a few hours anyway.  Yes, this means that long term storage of at least some diesel or bio-diesel fuel would be a necessary part of your household planning; and you might never be completely independent of society for your energy sources this side of TEOTWAWKI; but you'd still have the freedom to expand your solar array as events permit, slowly reducing the need to run your co-gen; until ultimately you can sell it to another, less established, off-grid household in your area.

I am not sure on this though.

IF I am using an engine to co-gen both electricity and heat, I would think the heat would be the harder of the two demands to meet.

My home takes about 5 gallons per day of propane to heat in the heart of the heating season which is about 455,000 btu's per day based off 91,000 btu's per gallon of propane.

Assuming some losses, it will take at least 10 gallons of diesel fuel consumption per day to get that with engine heat. So while it would seem fuel economy is of great importance, in this case it really is not because I am going to need at least 1 million btu's per day, and probably closer to 1.5 million btu's. I could drastically change my lifestyle so that the small gen-set listed meets my electrical needs, but I am not sure it will provide enough heat. My calculations show that 5000 watt engine will provide around 3/4 of a million BTU's per day. I am not sure that would be enough.

I really like how the full story can get teased out as we go back and forth like this. I know what I would do in your situation Your final setup will for sure differ:
1) set up a centralized outdoor wood boiler with a large water reserve to feed all the heating loads including domestic hot water and the new apartment. Working wide open they are quite efficient its when they idle during the shoulder seasons that they suffer so you maintain your electric boiler for then.
2) plumb your diesel backup genny into the central boiler's water reserve not the house to avoid heat transfer mashups and redundant infrastructure trying to feed the house directly with several systems. feeding the grid at maximum efficiency the generator would have a bottomless sink in the water reservoir to pour all that heat.
3)maintain an all electric home with the exception of the oven which will limit peak loads. On the Stove propane consumption is minor and would avoid the huge draw down on the generator.
4) investigate Net metering. My understanding is Maine just reversed their punitive measures on it:  https://www.natlawreview.com/article/maine-enacts-new-law-to-encourage-net-metering-and-long-term-contracts-distributed
As the bigger solar farms are upgrading to more efficient panels the used market is being flooded with 60 cell 225-250 watt panels that are less then 10 years old often for 15-20 cents per watt. I would choose systems with battery backup myself but that is a preference and straight economics does not support it at this time so a direct to grid system will be cheaper...

Always a fun mind exercise, Best regards,  David

Travis Johnson wrote:
IF I am using an engine to co-gen both electricity and heat, I would think the heat would be the harder of the two demands to meet.

Yes, of course; but you have more sources of heat than you are likely considering. Any device that consumes electricity produces waste heat that, if it lives inside your house, contributes heat gain in winter.  A refrigerator contributes a lot, less so a washing machine or dishwasher, because some heat is lost down the drain. If you're actually off grid, you certainly don't depend upon only one or two heating sources; while you might not have a rocket mass heater, you'd be wise to have a woodstove in addition to your main source of heat.

My home takes about 5 gallons per day of propane to heat in the heart of the heating season which is about 455,000 btu's per day based off 91,000 btu's per gallon of propane.

So adding a co-gen unit would reduce your propane consumption, but shouldn't be expected to replace it outright.

Assuming some losses, it will take at least 10 gallons of diesel fuel consumption per day to get that with engine heat.

Why would you assume losses? At least, why would you assume losses greater than your propane heater? The best propane furnance that I've seen was 96% efficient under lab conditions. Any well made co-gen unit should be able to come close to this, that's the point of co-gen.

So while it would seem fuel economy is of great importance, in this case it really is not because I am going to need at least 1 million btu's per day, and probably closer to 1.5 million btu's. I could drastically change my lifestyle so that the small gen-set listed meets my electrical needs, but I am not sure it will provide enough heat. My calculations show that 5000 watt engine will provide around 3/4 of a million BTU's per day. I am not sure that would be enough.

Again, the co-gen unit shouldn't be expected to provide for all your heating needs.  But it can contribute to your heating needs.

You are more correct on additional heat sources than you probably realize. My house was built right, I knew it was going to be radiant floor heated so I dumped 400 ton of rock underneath the slab so I am pulling quite a few BTU's via geothermal. It works so well that last year, when this house was vacant, and had the heat turned off, it never got below freezing in here. It was cold at 44 degrees granted, but it was also -7 degrees below zero (f) outside too. I thought that was pretty darn good.

It does get to about 63 degrees with no heat on, but people living in here. My radiant floor heat is off now, I am just using a 30,000 btu pellet stove to heat the front part of the house, but the bedrooms fluctuate between 63-67 degrees.

You are right of course too, in that I could just cogen most of the time, and if my temp falls below 100 degrees, the propane boiler fires and gets the main boiler loop up to temperature.

5000 watts though does sound low to me, mostly because I had a 4000 watt generator and it did not do much. Even with 20,000 watts it seems limited. The amperage gauge was in the green though, and the governor on the tractor should have kicked in and taken care of any start up loads. It is pretty responsive, and pto generators are known for quality of power, but my refrigerator, and other heavy loads much prefers grid power than Kubota!

I was doing research into these engines when there was a Lister engine group on yahoo groups.


This gent runs off veg oil gives him power and heat.


There was a guy who was able to get them to run off wood gas and used a micro controller to regulate the timing of when it fired.

David Baillie wrote:I really like how the full story can get teased out as we go back and forth like this. I know what I would do in your situation Your final setup will for sure differ:

Your quote was truncated just for ease of reading...

Yes, yes and yes again; this is a great discussion and I hope NO ONE feels I am being critical of what anyone has said. There are no wrong or right answers to this at all. I love these kind of discussions, and feel like if we were at a real coffee house, I would be buying coffee, and everyone would feel like you really are true friends...which you are in an online way.

But it is interesting because I was kind of thinking about what you were suggesting David (and you as well Creighton).

I no longer have sheep, so I have a lambing barn that is about 50 feet away from our house. It is insulated, has a concrete slab, and at 12 x 24 feet, pretty sizable. I also have a wood coal boiler kicking around that I could use, and thought about putting that inside the building, then sticking that 6 cylinder White diesel engine I have kicking around as well, and marrying it to the PTO Generator. I would then just have to plumb the radiator lines to the wood/coal boiler, vent the exhaust outside, and then run lines to the main loop of my radiant floor heating system.

I do have 220 volt in my lambing barn, so I could just back-feed my home that way so wiring is not a huge issue. The biggest issue is putting in the lines going to my heating system since I have to thread about (4) plumbing pipes, and (2) electrical lines, and (1) buried propane line.

It is interesting to note that my Uncle, who has solar, wind power and geothermal said he wished he had an all electric home too. As is, he saves about half of his electricity, but says the return on investment would be better if he had more electric appliances. He also said that he will never recoup his money for his windmill, never recoup his money for the solar, but has already recouped his money from geothermal. I thought that was kind of interesting.

Mart Hale wrote:I was doing research into these engines when there was a Lister engine group on yahoo groups.


This gent runs off veg oil gives him power and heat.

There was a guy who was able to get them to run off wood gas and used a micro controller to regulate the timing of when it fired.

Diesel and woodgas is a hard one... You will always need a certain percentage of diesel to get the engine to fire then you need to control the woodgas. For woodgas and chargas stick with spark ignition engines and save yourself a boatload of frustration...

Mart Hale wrote:

There was a guy who was able to get them to run off wood gas and used a micro controller to regulate the timing of when it fired.

While I do know that adding a spark plug in the threaded hole for an, entirely optional, glow plug is possible; I honestly don't know why anyone would want to convert a 6-1 to spark ignition.  Wood gas, propane, and any number of other non-diesel like fuels can be burned in a normal 6-1 without much issue, so long as there is a minimum amount of actual diesel in the gas charge; simply because the diesel will ignite at the proper point and ignite the rest of the fuel immediately.  One could use a quart or less in an hour of diesel, under load, if there's another fuel that one desires to consume first.  And I can see that as a valid option, because diesel fuel (or heat oil) isn't cheap; so if you have the option of feeding a woodgas generator into the 6-1, why not?

But part of the advantage of the slow moving 6-1 is that it can effectively use a wide variety of fuels as it's diesel charge; including heated vegetable oil, heat oil or kerosene.  It's a pretty tough engine.

Even the glow plug would only be useful to someone cold starting the engine in a very cold environment, such as Montana in January.

It would be interesting to see what would happen if someone made the Lister Engine into a 6 stroke engine instead of 4 stroke!

Not only would a person get an extra power stroke for free, they could take some of the parasitic load off the engine since there would not need to be any coolant system then. It would take co-generation off the table because obviously the engine heat is scrubbed out during the sixth and final stroke of the engine, but it would blow someone away with the efficiencies that they could get; especially in a generator set up.

The wood/coal boiler I have kicking around is kind of interesting.

I had installed it a couple of years ago, and some guys online helped me to install it correctly. As a joke, and knowing Katie is kind of cute, asked me "to take a picture of Katie with the boiler, just so we can see which one is better looking." I told that to Katie, so she said she would have her picture taken with it, and so we did.

But then Katie said she wanted a finished mudroom, but without a big ugly boiler in it. So I pulled the boiler and put it in storage, and that is where it has been ever since.

So about a month ago, I see the boiler again, and figure I have not been using it, so why not sell it. So I put it up for sale, and crickets...for like 2 months, nothing.

So I tell Katie, "well me mind's well keep it because a new boiler is like $7000-$9000", and this other boiler I am selling for $900. Then on Sunday I get an email from a guy, and he is interested in buying it. That is fine, I put it up for sale, I am a man of my word, so I tell him, I was going to keep it, but if he needs a boiler, hey, who am I to keep a man from making his house warm in winter. I tell him it is in perfect shape, and to come out and take a look at it. Heck I will even load the thing in a truck on a trailer with my tractor for him. With boilers, that is a very generous offer because moving boilers sucks.

Then I start getting question after question about it, and then he starts haggling me over the price. I tell him nicely, to go check out the price of new boilers, then the price of used boilers even, and decide if he wants it or not.

I keep forgetting that this is the reason why I do not sell stuff. You end up spending hours dealing with questions that at most ends up with a few bucks, but for the most part, just sucks up your time.

Anyway, this is the boiler I would hook up to the cooling system of that gen-set. It has a pretty big water jacket, and has the ability to have a domestic water coil installed in it as well. As for which is better looking; the boiler or Katie, that debate is up for you to decide. Myself, I think with the black with red trim, the boiler is quite striking. (LOL)

Love people like things... That is as far down that road as ill go. AS far as the boiler goes you would want a large tank of hot water so you could fire it hard once or twice a day and coat on the heated water as opposed to let it simmer. Also you could feed that genny coolant into the loop.
Here is a video of a wood gasser in Sweeden who contributes a lot on www.driveonwood.com this would be my goal...


A system sketch:  

and the thread:   http://forum.driveonwood.com/t/jos-wood-boiler/2015/34

Yeah boilers are pretty simple, the sketch shows pretty much what I would have. I would omit the tank because it adds a level of inefficiency.

I have never considered an external tank as efficient. I can see why people would think they were, because the boiler could be shut down for stretches of time, but it is not consistent which thermal dynamics. In short, it is going to take x amount of btu's to heat water up, and whether it is in one big dose, or a little at a time over time, it is the same btu's to do the same work. Think of it like an air compressor pumping up a big tank of air, versus a little tank. In use, the little tank will cycle on and off, but it is no more, or no less efficient then the big one. It just takes longer for the compressor to run to pump up the bigger volume of air.

The big tank also goes against the very nature of hydronic heating, which is: use constant amounts of heat to provide low temperature heat to the massive radiator that the floor is. Since radiant heat does not heat the air itself, but rather what makes up the room, this is significant radiating surfaces. But to be fair, the sketch involved typical baseboard heating and not a radiant floor heating system like mine. That is why we all must be careful when designing heating system.

If the tank does anything, it would be for the heating of domestic hot water. If I desired that, the tank would take the form of a BoilerMate. This would be required because I cannot mix boiler water with domestic hot water.

The video too was surprising because it used a very simple mechanical damper for incoming air. My boiler has aquastats as well, but it turns on a draft blower to increase, or diminish combustion. It also has an overtempt aquastat so that it can be wired to a relay so that zone valves can be activated. This is important because in a hand-fed boiler situation, you could have a runaway situation. This would happen if you just loaded the stove, the fire took off, and then you lost grid power. You could rely on the 12 PSI relief valve to open, thus depressurizing the system, but a better back up system is to have a dump zone so that all that heat gets pounded into a cold appliance. An antique cast iron radiator is an excellent means because it is simple and effective. A Modine unit is also really effective. You would most likely add a dump zone though if the boiler went into relief a lot. I seriously doubt this would happen though in a cogen situation because the power would never go out by the very definition of cogeneration.

I don't think you could have a runaway with the water tank. Runaway is usually something you worry about with on demand boilers fuelled by solid fuel. The idea is that a boiler especially a wood fired one works at its best efficiency when its firing hot. So in this case Jo fires a full load at max efficiency and uses the tank to float. The tank is highly insulated so any losses to the air is counter balanced by the increased boiler efficiency. So the theory goes...

I am not so sure...

If a appliance is efficient enough to heat up in the first place, then it surely is efficient enough to go past the boiling point and flash to steam. If it cannot, then it would seem circular to me; that it was not efficient in the first place.

Flashing to steam is a very dangerous proposition. Steam expands 900 times in an instant. They jokingly refer to it as squish-bang for a reason. Yes there is a pressure relief valve, but that should be a last resort. Proper design should be foremost on everyone's mind.

Jeesh...all this talk about 3000 watt engines and I forgot I had one sitting up to the other barn. It is a 1943 beast, 3 KW 1 or 3 phase, with gasoline or LP engine. That is liquid cooled too, so it might work in a Co-Gen application.

I am not sure the 6 cylinder White will work well. I actually went in that barn to check on that engine, and found out it is bigger than I thought. It is a White D3400 so it has 131 HP at 3200 RPM...quite a bit bigger than I thought. That will definitely heat my house, but goodness, I do not need 50 KW's of power output. It is reconditioned though, so it should run for awhile.

I never did make it back to the way back of the barn to go look at the smaller Izuzu Diesel I have for a refrigeration unit for a tractor trailer truck. That might work too, so those are my three options.

Betcha there is a market for the white... Sell it to finance the co gen project... Its hard though I know. I'm a natural pack rat for machinery who is trying to go minimalist...I currently have enough solar parts for 3 smaller systems all taken from tear outs for upgrading.

I agree with David.  It looks like your best play is to put the White up for sale, perhaps on one of the "Old Iron" collectors' websites.  Then use the proceeds to finance your co-gen setup, whether the refrigeration diesel will work or not.

Travis Johnson wrote:I am not so sure...

If a appliance is efficient enough to heat up in the first place, then it surely is efficient enough to go past the boiling point and flash to steam. If it cannot, then it would seem circular to me; that it was not efficient in the first place.

This seems intuitive, but it's not necessarily so.  Efficiency is different than effectiveness; and there are many heating processes that become increasingly inefficient as they approach the atmospheric boiling point of water.  It's not safe to depend upon that concept, but it's generally true that it's less energy efficient to heat a pot of water from 180 degrees to 200 than it is to heat that same pot of water from 80 to 100.

using a lister engine becomes most economical if you use recycled cooking oil to run it, has to be heated and filtered or you could make biodiesel from waste veg oil

bruce Fine wrote:using a lister engine becomes most economical if you use recycled cooking oil to run it, has to be heated and filtered or you could make biodiesel from waste veg oil

When running, a listeroid running on used vegetable oil smells similar to french fries.  Not good french fries, mind you; more like 2nd class dive bar fries, but the similarity is there.

But it's also way cheaper than making it into biodiesel.  That's an expensive and time consuming process.  I think that, with as many chemical resources that are necessary to make biodiesel; it will always be a niche fuel until petro-diesel is no longer economically available, and then only armies will be able to get it.  Even then, the chemicals necessary are used for so many things, humanity might consider it more important to manufacture actual soap.  Wood gas is an easier renewable fuel to actually create and use.

Travis Johnson wrote:

I never did make it back to the way back of the barn to go look at the smaller Izuzu Diesel I have for a refrigeration unit for a tractor trailer truck. That might work too, so those are my three options.

What are the specs for these?  I was trying to find these used on the Internet, to see if they were cheaper on the used American market than a new listeroid imported from India; but my google-fu is weak today.

Whoa!

I just found a 1928 Lister model A for sale on Craigslist, less than two miles from my house!

https://louisville.craigslist.org/atq/d/la-grange-lister-vertical-engine/7009375961.html

It's a 2.5 horsepower @600 rpm hit & miss engine.  Not a diesel, but still a wonderful choice for a co-gen.

Travis Johnson wrote:The only real way I could make this more efficient is, if I could add an Artificial Intelligence aspect to the PLC. If I had that, the computer would then take the computerized weather forecasts in digital language off the internet, and then adjust itself to what was coming.

I would program it so that IF a warm spell was forecasted for the next 12-24 hours, it would scale back on the heat knowing it was going to get warmer in the next few hours...

not really AI you need....just a web scrapper or maybe an old fashion RSS reader.  If you are serious, I could work on the code for you...it'd get me back into script writing, and if it works well enough for you, I could use your code part of my code portfolio.

let me know, it would be interesting!

Creighton Samuels wrote:

Travis Johnson wrote:

I never did make it back to the way back of the barn to go look at the smaller Izuzu Diesel I have for a refrigeration unit for a tractor trailer truck. That might work too, so those are my three options.

What are the specs for these?  I was trying to find these used on the Internet, to see if they were cheaper on the used American market than a new listeroid imported from India; but my google-fu is weak today.

I am not sure. As you will see, I made my way back to the shop so I took some pictures, but of all of them, I was not able to find out much about the Reefer Engine. It was made in 1983...I do know that much.

I think EVERYONE has a Reefer Engine kicking around somewhere. They are cheap because there are just so many of them out there. They work good because they have the shutdowns already in them for over temp, low oil, etc because they are run with no oversight from the truckdriver. Most are also in the 34 HP range, and operate at half throttle (1800 rpm) to save on fuel consumption.

If you do a search for Reefer Engines, I am sure you can find one close by for cheap.