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using natural gas to generate electricity

Here is an idea, get a regular (say) Holden V6 engine, convert it to natural gas, and connect it to a 100KW electricity generator. You should be able to find something from an army disposal sale. Total cost, say $2000 for the engine and $3000 for the generator for a total of $5000 plus a bit of elbow grease. Make sure the genny can supply a peak of 100KW, but typically put out say

20KW of constant reliable power.

Then get all your neighbours (preferably the whole street) to sign up to your "electricity company" and make money!

Let's do the math to see if it is viable:

According to Origin Energy, gas is 1.1021 cents per Megajoule (in Melbourne metropolitan area, Australia)

So One Watt (W) is 1 Joule per second, 1W=1J/s. So a kW=1000W=1000J/s. There are 60*60 seconds in an hour, so a Kilowatt hour is

3600*1000 J=3.6*10^6 J. One mega-joule is 1 million Joules, 1MJ=10^6 J, so 1 kWh=3.6 MJ.

So with gas, 3.6MJ, or 1KWh will cost 3.3 cents.

But 1KWh of electricity from that greedy electricity company costs around $0.18 to $0.20 so what is your break even point?

Now lets say you sell electricity to your neighbours for 18.3 cents per KWh, so you are competitive.... your running profit per KWh is 18.3 - 3.3 = 15 cents.

How long will it take to get that $5000 investment back?

Well you will need to sell 5000/0.15 = 33333KWh to break even. Now how much does the average house use????? That is a big question. My use is around

10KWh per day but the figure seems to vary widely from house to house.

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Now I will use an average of 10KWh per day per house. Say you have 10 houses connected to your little scheme, just to keep the numbers round. The 10 houses shouldn't overload the 20KW generator, with 100KW peak capacity, so I think that is a realistic number anyway.

So at 100KWh generated per day, it will take 333.3 days, or just under a year, to get your money back.

Will the engine run for a year, non stop? I would say yes. Plenty of taxis clock up millions of km.... and apparently running an engine on natural gas is good for it.

From Wikipedia: Due to the absence of any lead or benzene content in CNG, the lead fouling of spark plugs is eliminated. CNG-powered vehicles have lower maintenance costs when compared with other fuel-powered vehicles. CNG fuel systems are sealed, which prevents any spill or evaporation losses. Another practical advantage observed is the increased life of lubricating oils, as CNG does not contaminate and dilute the crankcase oil. CNG mixes easily and evenly in air being a gaseous fuel. CNG is less likely to auto-ignite on hot surfaces, since it has a high auto-ignition temperature (540 °C) and a narrow range (5%-15%) of flammability.[6]

CNG emits significantly less pollutants such as carbon dioxide (CO2), hydrocarbons (UHC), carbon monoxide (CO), nitrogen oxides (NOx), sulfur oxides (SOx) and particulate matter (PM), compared to petrol. For example, an engine running on petrol for 100 km emits 22,000 grams of CO2, while covering the same distance on CNG emits only 16,275 grams of CO2. [CNG is essentially methane, i.e. CH4 with a calorific value of 900 Kj/mol. This burns with Oxygen to produce 1 mol of CO2 and 2 mol of H2O. By comparison, petrol can be regarded as essentially Benzene or similar, C6H6 with a calorific value of about 3,300 Kj/mol and this burns to produce 6 mol of CO2 and 3 mol of H2O. From this it can be seen that per mol of CO2 produced, CNG releases over 1.6 times as much energy as that released from petrol (or for the same amount of energy, CNG produces nearly 40% less CO2).] The corresponding figures are 78 and 25.8 grams respectively, for nitrogen oxides. Carbon monoxide emissions are reduced even further. Due to lower carbon dioxide and nitrogen oxides emissions, switching to CNG can help mitigate greenhouse gas emissions.[6] The ability of CNG to reduce greenhouse gas emissions over the entire fuel lifecycle will depend on the source of the natural gas and the fuel it is replacing. The lifecycle greenhouse gas emissions for CNG compressed from California's pipeline natural gas is given a value of 67.70 grams of CO2-equivalent per megajoule (gCO2e/MJ) by the California Air Resources Board (ARB), approximately 28% lower than the average gasoline fuel in that market (95.86 gCO2e/MJ). CNG produced from landfill biogas was found by ARB to have the lowest greenhouse gas emissions of any fuel analyzed, with a value of 11.26 gCO2e/MJ (over 88% lower than conventional gasoline) in the low-carbon fuel standard that went into effect on January 12, 2010.[7]

BUT, Back to the story,.... how long will that Holden engine really last? Hard to say, without actually giving it a go, but let's do some more educated guesses.

A regular Holden Commodore is pretty shagged with 300 000 km on the odometer. So lets use that as a base. How many hours of operation would that be?

Now if we use the engine as a generator, it's fair to say that we are treating the engine nicely. There are no cold starts, the acceleration is smooth, there is no stop-start traffic like you have on a real road, so you could maybe assume that if it was compared to a car driven carefully and nicely on the road, and you treated it right, it could make the 1 million km mark without having to be re-built. OK OK, I know what you're thinking, overly optimistic, let's make it more like 500 000 km. How many ***hours*** of operation is that. Well assuming 60 km per hour average, that's 8333 hours of operation.

Now we broke even after 333 days of operation, which is 7992 hours, so

8333-7992 = 341 glorious hours of selling electricity at 100% profit.

341/24 = 14.2 days, and with 100KWh sold per day, thats 14.2x100x0.183= $259.86 dollars of cold hard profit, before the engine gets changed over.

OK probably not worth the trouble. Never mind, carry on, nothing to see here.

Reply to
Mr Mac
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Whose wiring were you proposing to use to do this?

No it won't. You're running a heat engine. You cannot extract all the energy from the gas. With your converted petrol engine, you cannot even extract most of it. See

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Reply to
Sylvia Else

I assumed that the power generation from gas to electricity was 100% efficient. Obviously that's not the case, but it is conceivable that the waste heat generated by the engine could be used to heat up a large water container, which could then be piped to the customers, and still be put to good use.

Also, while the engine would have to be replaced yearly, I'd say the generator would last a lot longer. No brushes, so just bearings every few years.

Reply to
Mr Mac

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Imagine the noise with that running 24/7.

There are plenty of large KWH capacity diesel generator sets around, (probably based on truck engines) that would be designed and built precisely for this purpose therefore much more efficient at doing this job, and designed to last long under these conditions.

Finally, you would need to have 2 of them, or ability to switch back over to grid power, for when you have to do servicing, oil changes, spark plugs and so on.

Unless you have the grid as backup a second unit would be needed as backup in case of failure also.

You would be better off switching your stove, hot water system and home heating (if any) over to gas then you would achieve much closer to the levels of efficiency that you claim that gas can deliver than running these as electrical appliances via a gas powered generator. - assuming you can get a supply of gas at the prices quoted.

I think Sylvia should know a bit about generators and running costs lately, having become the recent proud owner of one.

Reply to
kreed

Then you need a means of capturing the heat, pipework to deliver the hot water, and meters to measure it.

You also need a way of billing customers, obtaining their payments, dealing with people who don't pay, and so on.

It all adds to the cost.

Did you check the capacity of the gas main? Is it capable of delivering the extra gas? If not, then it will have to be enlarged, and someone will have to pay for that.

Kreed mentions noise. Yes, there will need to be sound insulation. More cost.

The harsh reality is that owning and operating a generator is not a licence to print money.

Sylvia.

Reply to
Sylvia Else

Forget all the technical arguments, the basic reality is that the present utility system is *far* more efficient than any small scale one would be, when everything is taken into account.

Reply to
Bruce Varley

Now apply 5% efficency of conversion and see what you get.

Hint, go read the wikipedia article on the solar panel, especially the bits on price parity.

Reply to
terryc

5% sounds a bit low.

The Holden Omega V6 engine uses 10.9 litres per 100km, and is rated at 190KW at 6700RPM. I'll assume that it needs 20KW to cruise at 100km/h. (if you have some real data, I would love to see it)

What is the real efficiency:

Well petrol has an energy of 32MJ per litre which is 8.89KWh per litre. Multiplied by 10.9 (litres in one hour of the engine outputting 20KW) gives

96.89KWh

So we burn close to 100KWh of petrol to get 20KWh of real work..... or around 20% efficient.

So yes, not very good figures. But heat is the biggest by-product. If we can use the heat to warm up our houses, and swimming pools, and hot water systems, we can internalise most of the losses.

Say you have a group of 10 to 20 apartments in a cold climate, where the heat is not wasted, but put to good use. It's conceivable that you will get close to the system working out.

Reply to
Mr Mac

That's certainly the correct result, but I think the technical/economics arguments still need to be expressed, because otherwise people, even those who would be willing to examine and understand the arguments, can be left with the impression that the whole thing is a scam by which people are sold overpriced electricity.

Mind you, I was watching Energy Australia do some substation work near my home the other day. They'd closed one side of the road, and had two people controlling traffic through the one remaining lane. I have to wonder whether that's really the cheapest way of doing that - portable automatic traffic lights are available.

Sylvia.

Reply to
Sylvia Else

"Mr Mac"

** Completely nuts.

If you have gas available - then so do all your neighbours.

They will already be using it DIRECTLY it for hot water, cooking and home heating - which are the 3 major consumers of energy in a home. Only their fridges, CFL lights and small appliances use electricity - plus air con if they have any.

Gas homes generally have rather small electric bills.

BTW:

Gas appliances are rather inefficient as much waste heat energy goes up flues etc.

.... Phil

Reply to
Phil Allison

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Strange you should say that, they were working on some 11kv lines near here, they had 2 guys up the pole using 2 separate cherry pickers, another spare cherry picker across the road, and 4 work utes. saw 6 other people on the ground that seemed to be doing very little.

Reply to
kreed

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A lot of the heat is lost out of the exhaust pipe, you would have fun collecting it.

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You could put the engine in the basement, and run the exhaust up through each floor, with it running through radiators in each apartment on the way :).

God help you if it leaked Carbon monoxide and killed someone.

Soviet apartments had arrangement like this, it even looked like a giant exhaust system in some units. (really excellent for drying out towels etc though)

They didn't use exhaust fumes though, steam was pumped around town from suburban "heating stations". I don't know what energy source ran these but it was probably one of the most inefficient ideas ever thought up. (hence the manholes seen often with steam escaping) That's socialism for you.

Reply to
kreed

A lot of the heat is lost out of the exhaust pipe, you would have fun collecting it.

---------------------------

Turbo.

Reply to
Dennis

Sure it wasn't NY USA you are thinking of? same steam heating and exhaust vents releasing steam.

Reply to
terryc

Never been there so I don't know. Have seen the Russian system first hand. Too hot, had to open all the windows to sleep properly. Thank god they seem to not have mosquitoes.

Reply to
kreed

. . .

Congratulations! You have just invented cogeneration.

There is a building around the corner here which has a gas-fired tri-generation plant - provides electricity, heating and cooling.

Andy Wood snipped-for-privacy@trap.ozemail.com.au

Reply to
Andy Wood

That's a bit like buying a PC and calling yourself an ISP.

Reply to
Swanny

And whre is the generator infrastructure located? Certainly can't be on someone's residential block. The location would need special zoning.

Reply to
Swanny

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How would they do it cheaper than the supply authority ? or are there peak or excessive business tariffs there ?

Reply to
kreed

I had a similar idea on a much smaller scale ie convert one of those small el cheapo generators from Bunnings to run on natural gas and use it for backup during power outages.

Suspect this may not be possible as they are 2 strokes so presumably lubrication would be a problem?

Anyway, as I would have to pay someone to do the conversion, I imagine this would be a really bad idea financially.

Dave Goldfinch

Reply to
Dave Goldfinch

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