Generator LPG conversions

Willie Trombone said:
R300 for 10 hrs vs R700 for the same time on petrol
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Hmm I doubt it. The fuel price is based on the energy content already + smaller factors they mostly have in common so I don't know how you'd save 50%+ unless you were also generating half the power. (Or doubled efficiency, which is basically impossible unless your petrol engine was broken to start with.)

Willie Trombone said:
Safer than petrol
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Depends on storage practices mostly I guess. But the back-yard conversion itself is likely to be the most serious source of danger so I reckon it's moot.

Willie Trombone said:
90% less emissions
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... of what? Definitely not CO2, since they're not drastically different chemically.
 
I have done this and it is 45-50% cheaper than running petrol.
25l petrol = R 450.00 with a runtime of approximately 13hrs
9kg LPG = R250.00 with a runtime of approximately 13hrs.
I have verified the figures before and after the conversion as I keep a spreadsheet with the generator runtime (for services) as well as associated costs such as LPG, petrol, oil and service kits.
I have no regrets doing the conversion.

PS: if you are mechanically minded, the conversion can be DIY.
 
lkswan747 said:
25l petrol = R 450.00 with a runtime of approximately 13hrs.
9kg LPG = R250.00 with a runtime of approximately 13hrs.
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bwana said:
I miss the days when those prices were even remotely accurate. :eek:
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You forgot that @lkswan747 is a senior citizen and gets Pensioner Discount on all kinds of purchases, especially on Tuesdays ...
 
I have seen plenty of these when I used to live in Mumbai, we also have LPG-converted cars.. They are much more cheaper than petrol-run generators/cars.
The downside is the engine corrodes, but the savings on fuel outweigh it.
 
lkswan747 said:
I have done this and it is 45-50% cheaper than running petrol.
25l petrol = R 450.00 with a runtime of approximately 13hrs
9kg LPG = R250.00 with a runtime of approximately 13hrs.
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Gasoline energy density = 9 500 Wh/L
* 25 L = 237.5 kWh

LPG specific energy = 13 778 Wh/kg
* 9 kg = 124 kWh

And 124/237 = 0.52
R 250 / R 450 = 0.55

So the price difference makes sense, unsuprisingly, because as I said above, price is based on energy content. The caloric value of 25 L of petrol is about twice that of 9 kg of LPG.

So the question is how are you getting the same runtime out of both fuels at these volumes? Is the engine twice as efficient on LPG? Or are you running half the load?


Willie Trombone said:
LPG has an extremely high thermal efficiency. When used as fuel for generators, it offers far superior efficiency than petrol, increasing the duration of the output and decreasing your energy costs.

Gas-fueled generators are far better for the environment than traditional petrol-fed units. Gas generators decrease carbon monoxide (CO) emissions by more than 90%, and hydrocarbon emissions (HC) by more than 70% compared to petrol generators.
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Clearly marketing speak. What about the physics though?

How would LPG offer superior efficiency? Does it burn much hotter? How?

How would LPG generate less CO? The only reason any hydrocarbon combustion produces CO is shortage of oxygen. Why would oxygen supply be different?

Same for hydrocarbon emissions. That's just unburned fuel. It's only going to be unburned if you're choking the engine or running it rich. Why would you do that? We are able to get stochiometrically near-ideal combustion ratios thanks to modern fuel injection and oxygen metering. Even without electronic control it defies belief that the OEM can get the design so wrong that an aftermarket conversion can work this kind of magic.

Ja so I have a lot of questions. Bottom line is this comes across as borderline perpetual-motion-machine-level bulls*it.
 
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Tomtomtom said:
Gasoline energy density = 9 500 Wh/L
* 25 L = 237.5 kWh

LPG specific energy = 13 778 Wh/kg
* 9 kg = 124 kWh

And 124/237 = 0.52
R 250 / R 450 = 0.55

So the price difference makes sense, unsuprisingly, because as I said above, price is based on energy content. The caloric value of 25 L of petrol is about twice that of 9 kg of LPG.

So the question is how are you getting the same runtime out of both fuels at these volumes? Is the engine twice as efficient on LPG? Or are you running half the load?




Clearly marketing speak. What about the physics though?

How would LPG offer superior efficiency? Does it burn much hotter? How?

How would LPG generate less CO? The only reason any hydrocarbon combustion produces CO is shortage of oxygen. Why would oxygen supply be different?

Same for hydrocarbon emissions. That's just unburned fuel. It's only going to be unburned if you're choking the engine or running it rich. Why would you do that? We are able to get stochiometrically near-ideal combustion ratios thanks to modern fuel injection and oxygen metering. Even without electronic control it defies belief that the OEM can get the design so wrong that an aftermarket conversion can work this kind of magic.

Ja so I have a lot of questions. Bottom line is this comes across as borderline perpetual-motion-machine-level bulls*it.
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I don't care how it does it! It works for me at a much cheaper running cost.
 
Willie Trombone said:
In fact, LPG is up to five times more efficient than other energy sources.
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Such absolute bullsh*t. I can all but guarantee you that line was written by some 22-year-old with a BA in sociology.

Go back to my previous post and develop an argument on first principles and stop copy-pasting sh*t teenagers / chatbots are posting for BP's LPG sales division.
 
lkswan747 said:
I have done this and it is 45-50% cheaper than running petrol.
25l petrol = R 450.00 with a runtime of approximately 13hrs
9kg LPG = R250.00 with a runtime of approximately 13hrs.
I have verified the figures before and after the conversion as I keep a spreadsheet with the generator runtime (for services) as well as associated costs such as LPG, petrol, oil and service kits.
I have no regrets doing the conversion.

PS: if you are mechanically minded, the conversion can be DIY.
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Still saving? Any issues? I am considering taking the jump and converting my 7.5KvA Ryobi generator too. Paying R300 every second or third day is getting on my nerve.
 
rvZA said:
Still saving? Any issues? I am considering taking the jump and converting my 7.5KvA Ryobi generator too. Paying R300 every second or third day is getting on my nerve.
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Definitely worth it. I have absolutely no regrets and have saved a lot of money on petrol. Invested in a 48Kg bottle and the thing runs for days (total loadshedding hours)

Pull the trigger man. :)
 
lkswan747 said:
Definitely worth it. I have absolutely no regrets and have saved a lot of money on petrol. Invested in a 48Kg bottle and the thing runs for days (total loadshedding hours)

Pull the trigger man. :)
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Thanks, I am pulling the trigger tommorow. I am now looking between two different bottles, 19kg or 48kg. The 48kg is a bit pricey at R5k for the bottle and about R1400 per change. But it may be worth it if it lasts a lot longer.
 
rvZA said:
Thanks, I am pulling the trigger tommorow. I am now looking between two different bottles, 19kg or 48kg. The 48kg is a bit pricey at R5k for the bottle and about R1400 per change. But it may be worth it if it lasts a lot longer.
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Not sure where you are located but I paid R3200 for a full 48KG bottle. If you can afford the 48kg I would recommend it.
Will you be doing the mod yourself?
 
lkswan747 said:
Not sure where you are located but I paid R3200 for a full 48KG bottle. If you can afford the 48kg I would recommend it.
Will you be doing the mod yourself?
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This is a company delivering the gas bottles and they will come out whenever you call them and replace the bottles for you. I think that is why they are more expensive? Nonetheless, no, I do not think I can mod this safely myself, I will be using a company who advertised the service and already modded the systems of two people in our street. I think it is a safer bet for me.
 
rvZA said:
This is a company delivering the gas bottles and they will come out whenever you call them and replace the bottles for you. I think that is why they are more expensive? Nonetheless, no, I do not think I can mod this safely myself, I will be using a company who advertised the service and already modded the systems of two people in our street. I think it is a safer bet for me.
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I am sure you won't be disappointed. Good luck.
 
Okay, done and dusted. Generator converted to gas. Will now wait for tonight to give it its first test run and see how it goes. Will let the first 19KG bottle run empty to see how many loadshedding sessions / hours I will get on a bottle.
 
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