Mains gas generator so I can go off grid?

[SenileOldGit]

I have 12kW of solar panels, and two 5kW Voltacon V7 inverters in parallel, and three 5kWh Pylontech batteries. My house has mains gas and mains electricity. My daily standing electricity charge is around 65p, my daily standing gas charge is 30p. Apart from two occasions in the past four or five months, I have used zero grid electricity. I am trying to work out whether it would be cheaper for me to go off grid for electricity, and keep my mains gas supply, and use the mains gas to power a generator in the Winter months on the occasions when I don't get enough solar that day.
I have a cheap (£70) petrol generator which I bought from Aldi online a few years ago, which I might be able to use with my inverters, if it turns out that I am able to generate enough electricity in the Winter most of the time, and only need a generator a few times a month. (I haven't gone through a Winter yet with my solar system working properly, so this coming 2024 Winter will be the first set of proper figures I get from my solar system.)
If it turns out that I need fairly frequent (three or more days a week, for at least a month) of generator electricity, I was considering buying a better generator, and I am wondering if you can run one off mains gas in the U.K.?
a) Does such a generator exist in the U.K.? I haven't been able to find one - all I can find are ones that run on propane, and I believe the air/gas ratios, and other things, are different, for propane, compared to mains gas.
b) Will a qualified gas fitter be allowed to/willing to extend a gas pipe round to the back of my house, and into the generator? I presume outside gas pipes are orders of magnitude less dangerous than gas pipes inside a house (zero risk of an explosion), but I don't know what the legality of this is.

I only ask because if I did need to use a generator several times a week, if it isn't on mains gas, I would have to get gas or petrol to it on a frequent basis, and this will be very inconvenient and I presume more expensive than using house gas.

Because I have 15kWh of Pylontech batteries, I don't need a powerful generator, 1kW would be fine.

 

[ConnerLabs]

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These ones can run off LPG or natural gas. They cost a bit more than £70.

All generators will wear out eventually. The Aldi one is probably good for about a week of continuous runtime before the engine is scrap. Hopefully the Briggs & Stratton will last a lot longer, but how much longer? The cost of buying the unit up front and rebuilding/replacing the engine each time it wears out can be a significant part of the cost of electricity from it. You should look for a specification of engine lifetime, do this analysis and work out how it compares to mains electricity before spending a lot of money on a generator.

 

[wpns]

No neighbors who might hear or complain about a generator running?

Sounds like you need a tri-fuel (gasoline, propane, natural gas which I guess you call mains gas?) generator and a proper, permitted, feed for it.

Most generators are derated when using natural gas, for instance:

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claims 2200W propane (which I'm not sure I'd believe) and 1800W natural gas, which is _probably_ peak, so I'd derate it to at least (1800/2200) 80% of that, so 1440-ish watts.

I mean, there are natural gas conversions for lots of generators out there, but there are a whole lot of other issues, and your cost per KWHR might be _way_ higher than buying some mains power occasionally (or installing more solar panels, if you can).

 

[SenileOldGit]

Thanks for your replies. I wouldn't want to spend more than £500 - £600 on the generator. I think over panelling is my only solution - but my existing 12kW of panels already take up a fair bit of my third of an acre garden, so ideally I would want the extra solar panels to be easily removeable in the Spring, but I don't think that's going to be possible - a decent ground mount that can withstand the worst winds of the Winter, and also easy to remove the panels. Putting them out every year, and then taking them back in, would be a real pain in the proverbial.
Do you really think the Aldi generator would only last for a week? I would imagine it would be as good as a cheap moped's engine, which must go for a fair few thousand hours before it needs repairing?

 

[wpns]

Do you really think the Aldi generator would only last for a week?

You already own it, give it a try. Then you’ll be able to advise the next person to ask the question.

 

[HalfBaked]

I would mount the extra panels for winter vertically on a fence line. That way they won't take up any extra space and won't need to be moved in the spring.

 

[Brucey]

You've made do with minimal grid during late spring/summer months when solar output is optimal. You need to figure out how much you'll be running the generator during winter. I would suggest seeing what happens this winter to do then have the numbers to see if it makes sense to disconnect from grid. I can't imagine it will make sense to save on the 65p per day if you have to spend hundreds or thousands of pounds in petrol costs.

 

[SeaGal]

Apart from two occasions in the past four or five months, I have used zero grid electricity.

It's easy in the summer in the UK.

if it turns out that I am able to generate enough electricity in the Winter most of the time, and only need a generator a few times a month. (I haven't gone through a Winter yet with my solar system working properly, so this coming 2024 Winter will be the first set of proper figures I get from my solar system.)

What is your daily kWh need in Winter?

 

[SenileOldGit]

I need about 10kWh per day all year round, which is probably 16kWh of solar, going by how many kWh I take from the panels at the moment. (Anywhere from 15kWh to 32kWh in a day - but I have an air conditioner that I use as much as I want when it's hot, so the 32kWh figure isn't representative of need, rather than of using everything I can to make use of the free electricity.)

 

[DPC]

Can you get off road diesel?

I would look at the costs of gas VS diesel and then look at the possibility of buying an Old lister SOM to provide power.
I suggest a water cooler SOM because you might be able to use some of the cooling system heat for your home in the winter months
you could also co fire that with about 40% gas from the mains to reduce diesel consumption of it turns out the gas is cheaper per BTU.

A used reconditioned SOM will last a lot longer than a China generator, and its quieter and quite easy to work on.

See that steaming drum of water?
That's the heat that could be recovered to warm your home.. ( maybe another 10% more could be collected from the exhaust too )
I just noticed your Avatar HA HA
Steptow and Son....

 

[CaliSunHarvester]

probably 16kWh of solar, going by how many kWh

Have you tried forecasting pv output with one of these web sites like pvwatts?

PVWatts

Estimates the energy production and cost of energy of grid-connected photovoltaic (PV) energy systems throughout the world. It allows homeowners, small building owners, installers and manufacturers to easily develop estimates of the performance of potential PV installations

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[Steve777]

Those old Lister engines can be made to run off of used vegie oil (from restaurants, etc), but it is quite a bit of work (and mess) to collect and filter the oil in order to use it.

But whatever ICE power source you use, be sure to calculate the cost per KWH of the electricity it will produce. There are a few threads on this forum which discuss just that. You might need to adjust those numbers for fuel and equipment prices in your locale, but should be a good starting place. Depending on the details, those numbers in the US tend to be in the $0.50 to $1.00 per KWH with fuel and equipment costs rolled in.

Generally it is uneconomical to replace the grid with a fueled generator based upon those numbers. However as backup for when the grid is unavailable, or if you anticipate grid pricing to soar, well that is a different thing.

 

[AntronX]

Nice thing about using natural gas to generate electricity is you can capture waste heat for home heating in the winter. If you already use gas for heating then you essentially get "free" electricity. Find old rusted out or accident totaled car with running engine and convert it to run on gas and attach it to a generator head. Car engine already has water cooling and will last much longer than cheapo air cooled generator. Exhaust will have 40-50% of thermal energy so you want to build a heat exchanger to capture it. Best if you can get everything for scrap price and restore it.

 

[DPC]

Don’t run any old diesel on waste oil.
I know you can but you set yourself up for all kinds of troubles.
A lister would be probably the easiest thing to get for a diesel set
I like Petter P range engines myself
A little more compact and modern
A Duetz hopper cooled ( or Andoria ) if you can get one ( probably harder now after brexit )
A Saab or Volvo marine diesel from a sail boat would make a fine home co generation plant

Petrol stationary engines in the UK are not something I am all that familiar with so finding those and natural gas conversions might be difficult
I have seen conversion of Petter p range to natural gas and spark ignition but you will be putting a lot of work into that

I don’t think generating your own hydro is cost effective unless you are co generating yo heat your home
And even the only to supplement your solar
And even then I’m not sure if it’s cost effective.

Not that simple to pull an engine from a car and run a generator
I can’t even think of any I have ever seen
Bedford made an online 6 truck engine block that doubled as a diesel or petrol …very robust engine with a governor that might work but that’s getting big and old hard to find …

 

[sunshine_eggo]

I only ask because if I did need to use a generator several times a week, if it isn't on mains gas, I would have to get gas or petrol to it on a frequent basis, and this will be very inconvenient and I presume more expensive than using house gas.

Have you confirmed your inverter/chargers will accept non-inverter generator power? Voltronics-type inverters are notorious for being intolerant of generator power.

Because I have 15kWh of Pylontech batteries, I don't need a powerful generator, 1kW would be fine.

Are you aware that your AiO pass through the source to power loads? If your combined charging and loads exceeds your generator output, the generator will overload and disconnect. You will need to set the maximum AC charge current and manage your loads inside whatever margin remains.

Lastly, generators are at their maximum efficiency at max rated continuous load. Lower power settings burn more fuel per kWh generated. To minimize wear and tear, a good balance is to run them at about 80% of peak.

 

[ConnerLabs]

Can you get off road diesel?

I would look at the costs of gas VS diesel and then look at the possibility of buying an Old lister SOM to provide power.

Got a Lister SR1 with 3kW Brush alternator at my workshop just now. I’m sure it would chug away at 1500rpm until the end of time, if you kept up with oil changes and valve lash adjustment.

The downside is the size, weight and noise level. The complete genset must weigh at least 150kg, and even with a better silencer than the standard pepper pot thing, an air cooled diesel is going to be noisy. The older water cooled Listers could be a lot quieter.

Have you confirmed your inverter/chargers will accept non-inverter generator power? Voltronics-type inverters are notorious for being intolerant of generator power.

This is a real concern. The grid input is hamstrung by the anti-islanding algorithms that make it disconnect if voltage or frequency go too far out of bounds. A belt driven alternator as shown in the video doesn’t stand a chance. There is no fundamental hardware reason for this limit, it’s programmed into firmware for regulatory reasons and some inverters allow it to be relaxed.

Even without anti-islanding, my inverter welder turned its nose up at Lister’s output for reasons that I’ve yet to figure out.

 

[SeaGal]

I need about 10kWh per day all year round, which is probably 16kWh of solar, going by how many kWh I take from the panels at the moment. (Anywhere from 15kWh to 32kWh in a day - but I have an air conditioner that I use as much as I want when it's hot, so the 32kWh figure isn't representative of need, rather than of using everything I can to make use of the free electricity.)

IMHO, 10kWh per day is not going to be achievable with your existing capacity during the Winter. As you don't have solar production figures for Winter, here's what we achieved over the last 2 years with 6.6kWp panels in sunny East Anglia; so that's about half of your capacity... I'll add a slight caveat that our panels are low tilt E-W facing, so we don't benefit from good sun in Winter, but the production from both strings is equal on overcast days - and last December there was a lot more overcast or rainy days than sunny ones. My finger-in-the-air estimate with S facing panels in December with 12kWh would be about 160-170kWh, having looked at the sunny vs. cloudy days and assuming that you're in an equally sunny part of the country. That's an average of 5kWh per day. But I'll let you know next Spring what we achieve this coming Winter as we're adding some S facing panels

Best day in summer we got 40kWh.
Best week in summer we got 240kWh.
Worst week was last December at 14.5kWh - so that's an average of only 2kWh per day with the worst day producing only 800Wh.
Whole month of December was 65.2kWh. Yep, less than 2 days in summer!
And November 1st to Feb 1st yielded just 300kWh.

 

[ConnerLabs]

Best day in summer we got 40kWh.
worst day producing only 800Wh.

This is the reality of solar power in the UK... A bit worse still up here at 56 degrees North.

you could also co fire that with about 40% gas from the mains to reduce diesel consumption

This would be an interesting experiment for sure. For safe operation the governor would need to control the rate of gas supply as well as diesel.

 

[DPC]

Got a Lister SR1 with 3kW Brush alternator at my workshop just now. I’m sure it would chug away at 1500rpm until the end of time, if you kept up with oil changes and valve lash adjustment.

The downside is the size, weight and noise level. The complete genset must weigh at least 150kg, and even with a better silencer than the standard pepper pot thing, an air cooled diesel is going to be noisy. The older water cooled Listers could be a lot quieter.


This is a real concern. The grid input is hamstrung by the anti-islanding algorithms that make it disconnect if voltage or frequency go too far out of bounds. A belt driven alternator as shown in the video doesn’t stand a chance. There is no fundamental hardware reason for this limit, it’s programmed into firmware for regulatory reasons and some inverters allow it to be relaxed.

Even without anti-islanding, my inverter welder turned its nose up at Lister’s output for reasons that I’ve yet to figure out.

Post some pictures of this set.
Not as common as gasoline fueled set but I used to run across old Listers and Petters in bush camps.

Sometimes you get corrosion and dirt on the slip rings and they make noise electronics do not like.
There are other things that can be done to clean up the noise.

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Yes the air cooled units are noisy compared to the water cooled...

You could run your home on an air cooled unit but you lose the possibility of heat recovery

 

[ConnerLabs]

Noisy, stinky, badly needs a wash... and so does my generator.
I've cleaned the slip rings with a fibreglass brush, and since making this video I replaced the selenium rectifiers with silicon. They were going intermittent and making the output voltage drop off at random.

I looked at the output voltage on an oscilloscope and it actually seems pretty good compared to a newer petrol generator that I had in for repair.

It will actually run my welder fine when set for 115V output. 230V output also works if I step it down to about 200 with an autotransformer.

 

[DPC]

Starts and runs well...
Rings look pretty clean....

Good unit

needs muffler lol...

 

[CaliSunHarvester]

Best day in summer we got 40kWh.
Best week in summer we got 240kWh.
Worst week was last December at 14.5kWh - so that's an average of only 2kWh per day with the worst day producing only 800Wh.
Whole month of December was 65.2kWh. Yep, less than 2 days in summer!
And November 1st to Feb 1st yielded just 300kWh

That's some impressive summary. I want to do the same when I have 12 months completed.

 

[SenileOldGit]

I would mount the extra panels for winter vertically on a fence line. That way they won't take up any extra space and won't need to be moved in the spring.

The problem with that is that they would cause shading on my existing panels during the Winter. I would have to mount them at an angle, and even then, I may not have enough space - my neighbour to the South has a line of trees about 12 feet high, between his garden and my garden, so I have to keep the panels away from them.

 

[SenileOldGit]

Thank you all for your replies, very interesting food for thought. At the moment, I think my cheapest and easiest option is to get a smart meter, and use Economy 7 electricity to charge my batteries at night in the Winter, it's only 7p per kWh from Eon, my electricity provider. I will have to check the next day's weather forecast each day, before deciding how many kWh to charge the batteries with each night, but that's all.
I am also thinking about getting two 'Easy Fit' air conditioners, which also act as air source heat pumps, to use for heating, as I believe that you get 3 kW of heat for every 1 kW of electricity they consume. (I will also use them as air conditioners in the Summer, when I have loads of spare solar energy to use.) Would this be almost as cheap as gas central heating, which I also have?

 

[Lprantner]

I have 12kW of solar panels, and two 5kW Voltacon V7 inverters in parallel, and three 5kWh Pylontech batteries. My house has mains gas and mains electricity. My daily standing electricity charge is around 65p, my daily standing gas charge is 30p. Apart from two occasions in the past four or five months, I have used zero grid electricity. I am trying to work out whether it would be cheaper for me to go off grid for electricity, and keep my mains gas supply, and use the mains gas to power a generator in the Winter months on the occasions when I don't get enough solar that day.
I have a cheap (£70) petrol generator which I bought from Aldi online a few years ago, which I might be able to use with my inverters, if it turns out that I am able to generate enough electricity in the Winter most of the time, and only need a generator a few times a month. (I haven't gone through a Winter yet with my solar system working properly, so this coming 2024 Winter will be the first set of proper figures I get from my solar system.)
If it turns out that I need fairly frequent (three or more days a week, for at least a month) of generator electricity, I was considering buying a better generator, and I am wondering if you can run one off mains gas in the U.K.?
a) Does such a generator exist in the U.K.? I haven't been able to find one - all I can find are ones that run on propane, and I believe the air/gas ratios, and other things, are different, for propane, compared to mains gas.
b) Will a qualified gas fitter be allowed to/willing to extend a gas pipe round to the back of my house, and into the generator? I presume outside gas pipes are orders of magnitude less dangerous than gas pipes inside a house (zero risk of an explosion), but I don't know what the legality of this is.

I only ask because if I did need to use a generator several times a week, if it isn't on mains gas, I would have to get gas or petrol to it on a frequent basis, and this will be very inconvenient and I presume more expensive than using house gas.

Because I have 15kWh of Pylontech batteries, I don't need a powerful generator, 1kW would be fine.

I use a Champion 9kw Dual fuel generator, propane or gas, always use propane, and with my 6kw hybrid inverter, works great.