# Old Mini Van to power and heat house.

## Main Question or Discussion Point

Hello, I have been thinking about using my old mini van to power and heat our home. We live in Canada and hydro prices have gone up allot over the past few years. Anyways the idea is to park the van beside the workshop, run the radiator lines to large water tank in the garage area that would hold heat, maybe 500 or 1000 gallons. I would also hook up 12 volt and 120/220 volt generators on the v belt system for power to charge batteries that power lights and small electronics. Also thinking the heat from exhaust could be caught with water jacket system, I get propane fairly cheap here so maybe I would run on propane, I already burn propane to heat house so why no get power and heat from hopefully the same amount of propane, thus eliminating my hydro bill altogether. The van would be put on blocks and would never move again, duck work from car heater could also heat the shop.

Any advice would be much appriciated.

thank you

Jay

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russ_watters
Mentor
Welcome to PF!

You'll have to run the numbers on the economics:

How much propane do you use in a season?
How much does it cost?
How much hydro (electricity?) do you use in a season?
How much does it cost?

You are making one major mistake though: the propane bill will go up. Your propane heat is at worst about 80% efficient and if you use your car's radiator and try to recover some of the heat from the exhaust as well, you might be able to get 50% heat and 30% power.

AlephZero
Homework Helper
Another issue is that unless you put some mechanical load on the engine, you will only be able to run it at low power (even if the engine revs are at the maximum) so you won't be burning very much fuel.

Of couse your could build a dynamometer brake for the engine and extract the waste heat from that as well, but that's heading away from this being a "simple" project.

I burn about $250 to$300 in propane over the winter months plus about same in electricity. I figure if I was able to have the engine start and run for 1 hours say 4 times every 24 hours to heat the system and power batteries. The current propane burner we use appears to burn allot and is constantly firing up, I can see the engine burning more.

Later on I would *** a gasifier boiler that will burn pellets.

Another issue is that unless you put some mechanical load on the engine, you will only be able to run it at low power (even if the engine revs are at the maximum) so you won't be burning very much fuel.

Of couse your could build a dynamometer brake for the engine and extract the waste heat from that as well, but that's heading away from this being a "simple" project.
well my mini van start up and get hot in about 10 minutes with no load, so burning less fuel is a good thing.

sophiecentaur
Gold Member
well my mini van start up and get hot in about 10 minutes with no load, so burning less fuel is a good thing.
You will only get as much energy out as the energy you put in, in the form of fuel. If you don't burn the fuel, you won't heat your house. There is no 'free' or even 'ultra efficient' way of using the fuel in your car or in your boiler. You will only get a kWhour (max) out of every kWhour's worth of fuel you buy. (Less a good 20% of losses) These are the facts of life, I'm afraid and there is no way round them.
Best way to save money on heating is to turn the thermostat down and to spend some money on suitable insulation methods.

russ_watters
Mentor
I burn about $250 to$300 in propane over the winter months plus about same in electricity.
I also need to know how much propane and how much electricity that gets you.
well my mini van start up and get hot in about 10 minutes with no load, so burning less fuel is a good thing.
That doesn't really tell you anything useful -- just getting hot is not an indication of how much recoverable heat it is producing.

A quick calc, though: Gasoline and propane have similar heat capacities, of around 48 MJ/kg (higher heating value). Based on watching my car's fuel flow in realtime, I would guestimate that your minivan will burn about 2 kg/hr. That's 96 MJ/hr or 26 kWh (also a rate of 26 kW).

Recovering half of that as heat would mean you could get 13 kW of heat. That's actually a decent amount of heat, so this is probably viable from the heating side. Check the capacity of your existing heating against that.

Now, if you could simultaneously recover half that much electricity (note, we're at idle here, so probably not...), that's 6.5 kW. I'd be shocked if you could use anywhere close 6.5 kW of in the winter. And since my gut tells me the cost of your generation of the electricity is probably higher than the electric company is selling it to you for, that will probably destroy your economics.

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russ_watters
Mentor
Another issue is that unless you put some mechanical load on the engine, you will only be able to run it at low power (even if the engine revs are at the maximum) so you won't be burning very much fuel.
The mechanical load comes from the generator.

Still, the biggest problem with cogen is whether the electrical and heat outputs are matched to the load. In the winter, the heat requirement is almost certainly going to dwarf the electrical requirement, but you can supplement the fuel-fired heat with electric heat...if you can generate the electricity cheaply enough for that to be economical.

sophiecentaur
Gold Member
I can see that the attractive feature of this scheme is the 'free mini van'. Do not get too hung up on that aspect because the other costs will soon become appreciable - even just mounting the engine or getting power off the shaft in situ. Combined heat and power systems have been tried all over the place and can be quite effective, I believe, in the right circs. But you need to do a total costing and bear in mind that you never get anything for nothing.
BTW, what sort of generator(s?) were you planning to link to? If you need to buy one then it could cost you. For AC power, you would need to control (regulate) the engine speed fairly well and that wouldn't be easy on a road engine.

If you were really interested in being self sufficient for power, you would probably be better off buying a second hand water cooled diesel generator. You don't want to land yourself with a 90% built system that never actually delivers.

Averagesupernova
Gold Member
I can't say for sure but I would guess it will cost you 5 to 10 times what you pay for commercial power to generate it on your own. That may be a conservative guess as it depends on what you pay. About 15 years ago I did some calculations on this during an extended power outage. I came up with 50 cent per KWH just in fuel to generate it with a gas powered generator. This was an average over a number of days. The generator did not run unless necessary. It was easy to calculate because there was little electrical load compared to being on the grid since everything that was not necessary was turned off.

Thanks for all the replies everyone, propane is cheaper then diesel here so I do want to go propane CHP, I have seen a few units out there that would fit the bill but pricy and not available here in canada, I been thinking a liquid cooled propane generator could easy be used to both heat and power house. Pellets are another cheap option for me, I found one stove maker who claims to have adapted a steam turbine for power, interesting. I will start by getting my electric system in place, battery bank and inverters, then eventually ill find the best way to charge them,

I am now thinking of going with an outboard boat motor, 4 stroke converted to propane connected to an industrial electric motor for power, engine heat recovered through cooling system and exhaust system. I figure around 200cc would do it all, this could all be built into my shop beside the house and have lines running to the house.

I can't say for sure but I would guess it will cost you 5 to 10 times what you pay for commercial power to generate it on your own. That may be a conservative guess as it depends on what you pay. About 15 years ago I did some calculations on this during an extended power outage. I came up with 50 cent per KWH just in fuel to generate it with a gas powered generator. This was an average over a number of days. The generator did not run unless necessary. It was easy to calculate because there was little electrical load compared to being on the grid since everything that was not necessary was turned off.
Hi seriously doubt 5 to 10 times is accurate,

OmCheeto
Gold Member
I am now thinking of going with an outboard boat motor, 4 stroke converted to propane connected to an industrial electric motor for power, engine heat recovered through cooling system and exhaust system. I figure around 200cc would do it all, this could all be built into my shop beside the house and have lines running to the house.
Wow! Sounds like something I would do. Except that it would take me months to design a governor. Have you considered just buying a small generator?

Also, what you asking about is sometimes called cogeneration, or CHP, which is an abbreviation of "Combined Heat and Power". A google search of cogeneration here at the forum yields 64 references.

Several of which provide relevant information of currently existing products: Lichtblick, Honda.

sophiecentaur
Gold Member
Hi seriously doubt 5 to 10 times (cost) is accurate,
I wouldn't be all that surprised. They go to a lot of trouble to get power station turbines as efficient as possible, achieving up to around 60% elec out / fuel in. Car engines don't manage that over most of the power range and then there would be the performance of a low cost / surplus generator. Then you are already paying for an expensive delivery chain for your fuel (as opposed to the cheap wire distribution of electric power).

The time when you really do better 'on your own' is when you have a free source of energy - like regular wind or good Solar. You could find you put a lot of effort and bruised knuckles into your project and either barely break even or lose out. That would be disappointing so get the spreadsheet out and do your sums very carefully before lifting a single spanner.

And don't forget to factor in the oil changes.

sophiecentaur
Gold Member
And the bloody noise!

How about a toyota prius as a starting point?

How about a toyota prius as a starting point?
But then you have to own a Prius.

I just got back from the junkyard and there is one that is complete.

Engine and transmission are 600 bucks.

Wiring harness is 20 bucks.

Main ecu is 30 bucks.

That said, I think a diesel hybrid would be the way to go.

sophiecentaur
Gold Member
What use would a hybrid be? You don't want to be using up battery power to turn over the engine if it's not taking you anywhere.

I am going with propane because I already have propane and its cheap here, 2 cylinder liquid cooled 4 stroke making about 50 to 80 HP should be fine, the heat from the engine and alternators 12v and 120/220 volt, all tied into a system,

What use would a hybrid be? You don't want to be using up battery power to turn over the engine if it's not taking you anywhere.
Hybrid cars can generate a huge amount of electrical power.

Hybrid certified Toyota and Lexus master technician.

sophiecentaur
Gold Member
Hybrid cars can generate a huge amount of electrical power.

Hybrid certified Toyota and Lexus master technician.
Yes but not at mains voltage AC, which is what we all really want in the home. The real reason for not using a motor car engine is the lack of accurate speed regulation and, in fact, getting the gearing / pulley system right for optimum engine speed / efficiency. This project is supposed to be competitive with the mains supply so it needs to be done right.
A car engine is designed for variable power / speed output, up to, say 100kW. A generating set needs to produce up to 10 - 20kW at a fixed speed. Two significant differences when you're talking about efficiency.

This project is supposed to be competitive with the mains supply so it needs to be done right.
NOTHING is competitive with the mains supply.