Running a genny off propane or butane?

[Vortex2]

Hi team,

Petrol is really an expensive fuel for a genny, due to the tax component.

Is there any way to run a genny from propane or butane?

Thanks.

[adam2]

Yes certainly, conversion kits are available from a number of sellers and ready converted generators are also available.
Not much of a saving at present, but that might change. Butane wont work in cold weather.

A large LPG cylinder gives a longer run time than a full tank of petrol. LPG keeps forever and has many other uses.

[adam2]

Alternatively a diesel generator might be better. Red diesel is cheaper than petrol. diesel engines not only burn cheaper fuel but less of it.
Diesel is safer than petrol or LPG.

Only 30 liters of petrol may be lawfully stored.
Almost no limit on diesel.

[Vortex2]

>>Only 30 liters of petrol may be lawfully stored.

Does that apply to agricultural sites too?

[adam2]

>>Only 30 liters of petrol may be lawfully stored.

Does that apply to agricultural sites too?

In general yes it does. Note however that the 30 liter limit is only applicable to petrol in cans, including petrol in cans within vehicles. Petrol in the built in tanks in vehicles does not count. So ten vehicles containing hundreds of liters in total is fine, but 31 liters in cans is not permitted.

One possible bit of "wiggle room" is that the limit is 30 liters per "premises" If you own several different premises some distance from each other, such as three houses in different towns, then clearly you may store up to 30 liters at each premises.
If you own several "premises" that are near each other or are contiguous, then you MIGHT be able to claim that 30 liters may be stored in each of these premises. It all depends on the exact definition of "premises" Is "Hill view farms" one premises, in which the case the limit is 30 liters at hill view farms.
Or could one take the view that Hill View farms comprises several premises such as a tool shed, a barn, a workshop, etc and that 30 liters could be stored in each premises.
What if you let a cottage to an agricultural worker ? can they store 30 liters in addition to that stored by the farmer ? AFAIK they can. If their employer and landlord permits this. Many tenancy agreements forbid ANY storage of petrol.

Another possibility is that under certain circumstances as much as 275 liters of petrol may be stored. This requires a a licence issued by the local authority, and generally an inspection by the fire brigade. Requirements include significant distances between the petrol store and ANY other buildings, significant distance from the property boundary, and from any water course. Very few agricultural sites can meet all the requirements.

Petrol should not be stored in living quarters, not certain if this actually illegal or simply fool hardy.
Take great care with ANY storage of petrol.

[adam2]

Did you hear about poor old Harry ?
No, what about old Harry ?
He struck a match to inspect the level in his petrol tank !
Oh No, you would think that would be the last thing he would do.
It was.

[clv101]

Alternatively a diesel generator might be better. Red diesel is cheaper than petrol. diesel engines not only burn cheaper fuel but less of it.

Yes, if you actually need to use a generator for any significant amount of energy diesel is the way to go.

[Catweazle]

If I was building a generator for long-term use I'd buy an old diesel car, remove the gearbox, add the generator electrics, park it next to my house, pipe the cooling water through my central heating system, add heat extraction to the exhaust. Unlikely to be stolen or even noticed, built in diesel storage, engine developed to run for hundreds of thousands of miles. Cost of an MOT failure diesel VW ? About £50.

[adam2]

If I was building a generator for long-term use I'd buy an old diesel car, remove the gearbox, add the generator electrics, park it next to my house, pipe the cooling water through my central heating system, add heat extraction to the exhaust. Unlikely to be stolen or even noticed, built in diesel storage, engine developed to run for hundreds of thousands of miles. Cost of an MOT failure diesel VW ? About £50.

That might prove more complex than it sounds, especially with regard to engine speed and therefore frequency control, but does indeed have the merits of low cost and being hard to steal.
If going down this route, then once the machine is running correctly, consider purchase of a second old car of the same model so as to have a spare.

[Catweazle]

That might prove more complex than it sounds, especially with regard to engine speed and therefore frequency control,

Cruise control ? Automatically varies engine power to maintain a set frequency, but probably easier to charge a large battery bank and draw via an inverter.

[adam2]

It might be possible to adapt a cruise control, but this may also prove more complex than it first sounds.
Cruise control maintains a constant ROAD speed despite varying gradients and headwinds etc.
With a vehicle adapted to a static generator, there is no road speed to detect.

If a cruise control was set to 50 MPH but actually achieved 53 MPH most drivers would not be that worried, and could of course set it to 47 MPH to more accurately achieve an actual 50 MPH.

53 cycles is too high for most electrical equipment intended for 50 cycles, and in the other direction, 47 cycles is too low.

In the UK the national grid are required to keep the frequency between 49.5 cycles and 50.5 cycles and almost always achieve this. (under emergency conditions, such as during a black start, the grid frequency might vary from 47.5 cycles up to 52 cycles, that however is for a "once in a lifetime" emergency, not normal operation)

Some overseas grid systems, and some generators vary between 48 cycles and 52 cycles and these should be regarded as the acceptable limits for most appliances.

[clv101]

If you already have an off-grid system with battery storage, you don't run anything straight from the generator. Instead you just run it for a few hours every few days when the sun or wind resource is poor to top up batteries.

So you can take a messy AC source, rectify, then put it through your DC charger.

[Catweazle]

If you already have an off-grid system with battery storage, you don't run anything straight from the generator. Instead you just run it for a few hours every few days when the sun or wind resource is poor to top up batteries.

So you can take a messy AC source, rectify, then put it through your DC charger.

Which would also be a better fit with the power of a car engine - probably a bit too powerful for conventional "always on" use, better suited to run at 20KW for a couple of hours to charge the batteries.

[Vortex2]

Does anyone have any idea on how much power a car alternator can deliver for long periods?

[adam2]

Does anyone have any idea on how much power a car alternator can deliver for long periods?

They vary a bit, but about 50 amps for the cheaper and smaller types up to about twice that for extra duty types.
So about 700 watts to about 1,400 watts at 14 volts.
Some types are NOT protected against overload.

There is not an absolute limit, but a trade off between output and life/reliability.
An alternator that might die of overheating within hours in the engine compartment of a car during a heatwave, might survive a similar loading for months in a micro-hydro installation on a snow covered hillside.

There is available a special type of alternator for fitting to a vehicle "Kestrel" brand. These produce several kw of well regulated 240 volts AC at any reasonable engine speed. Very expensive new and not often found used. They are not a simple alternator but involve some sophisticated electronics.

Historically various special alternators and dynamos were fitted to vehicles, but tend towards historical curious rather than being used these days.