Natural Gas generator efficiency

[Doggydogworld]

Does anyone make a natural gas furnace / generator???

Micro-CHP was the next big thing a few years ago. Gas utilities and propane vendors were hyping them. Figure 2 in this technology snapshot (PDF) has a nice graph showing type (fuel cell, internal combustion, Stirling, microturbine, etc.) and power rating. I have no idea how many of those vendors are still around, though Blue-Gen looks to be active in the UK.

FWIW, the Generac PowerPact 7.5 kW (LP) / 6 kW (NG) is rated at 117 cu ft of NG per hour at full 6 kW output. So that's about 5 kWh per therm, or 14 cents/kWh if your therms cost 70 cents (a great price, btw, Henry Hub futures are trading around 60 cents/therm today). People figure a small Generac will last ~3000 hours, or 18,000 kWh at full load. That adds another 11 cents/kWh in depreciation. Then you have maintenance costs (free labor, ha), repairs, etc.

 

[niktak11]

I was doing this calculation once for my 5500W Onan generator, which needs 1/2 gallon with no load and 3/4- 1 gallon per hour at full load.
Getting about 5kw/h into the batteries per hour. so it's 1 Gallon for 5kwh.

It's not really something I would be recommending permanent. 60cents - $1 per kw/h It's very expensive to run that thing.

Just so that you know 1 gallon is roughly 33kw/h. It might have made sense when gasoline was a $1.5 but not in $3-4 times.

The numbers I calculated for my gas generator are similar to yours. Nearly $1/kWh.

 

[sunsurfer]

Then nothing else works on them. The throttle control is inop without the inverter.

You could make your own dc generator with $150.00 engine and $150.00 alternator.


OP, you're not going to be on the winning side trying to arbitrage grid power with a home generator.

Good point! I like the simplicity and regulation already built into an automotive alternator.

If your charging batteries, its kinda a fixed load. Just set the throttle for the output/load you want or put a digital or mechanical governor on it?? Just thinking out loud here. The DC brushless gen head right off the crankshaft is kinda nice, no belts. Of course, yes the setup you mention is WAY simple and easy to FIX.

I live off grid and am my own power company. I do mostly solar but I have a lister clone and they work so well with BLDC motors. One could just mount some hover board motors and be done...though motors are motors and the hours add up fast on generators. No piston motor runs forever with out lots of parts. Thats just life. Its why I'm building a gas turbine from an automotive turbocharger.

Generator = high fuel cost and high parts cost no matter what brand or fuel. I'm off grid and allot of my neighbors are so we are very familiar with the life time of a generator that is used more then just for power outages or camping. A friend of mine runs them 24/7. He changes the oil frequently and mostly partial load but he has to buys them every 3-6 months no matter the brand or style. Time and physics, plain and simple.

 

[Hedges]

A friend of mine runs them 24/7. He changes the oil frequently and mostly partial load but he has to buys them every 3-6 months no matter the brand or style. Time and physics, plain and simple.

How Many Hours Should an Onan Generator Last? (All Facts)

Have you ever wondered how many hours should an Onan generator last? Look no more. We´ve got you covered. RVs are perfect for taking the luxuries of the home onto

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10,000 to 20,000 hours would be 13 to 26 months.

Unless he needs full load, I'd think an inverter/charger with auto-start would be an improvement.
(then start adding PV)

And then there were the diesel refrigeration units on containers that were mentioned earlier.

For your automotive alternator setup, you might want to adjust throttle according to exciter winding voltage (or duty ratio). Could idle down as current draw decreases.

 

[sunsurfer]

How Many Hours Should an Onan Generator Last? (All Facts)

Have you ever wondered how many hours should an Onan generator last? Look no more. We´ve got you covered. RVs are perfect for taking the luxuries of the home onto

www.rvandplaya.com

10,000 to 20,000 hours would be 13 to 26 months.

Unless he needs full load, I'd think an inverter/charger with auto-start would be an improvement.
(then start adding PV)

And then there were the diesel refrigeration units on containers that were mentioned earlier.

For your automotive alternator setup, you might want to adjust throttle according to exciter winding voltage (or duty ratio). Could idle down as current draw decreases.

Well, he is working on his solar but off grid life is busier than you would think, especially when your building on raw land and working 40 hrs a week.

As far as the 10k - 20k hour life in your link, I call bull $hit. I wish that was reality but its not. Real world would tell me different. I've had Onans at remote communications sites and there is nothing special about them that gives them magic extended life. Unobtainium alloy rings?

If you drove 70 MPH for 20,000 hours ( which is the easiest life for a motor/constant temp/load ) that equals = 1.4 million miles. Car engines are built WAY better then a $600 generator thats running balls out to keep your fridge cool.

My current Gen has 800 hrs and its burning oil and making lower end noise. I have change the oil 16 times in it (every 50 hrs).

I ran a honda i2200 my first summer off grid and wore it out just running a window unit for the summer.

Making your own power is pricey. I am VERY grateful for the solar tech we have now.

 

[eXodus]

The numbers I calculated for my gas generator are similar to yours. Nearly $1/kWh.

thanks for confirming. And that's not including maintenance and depreciation. Just fuel.

 

[LeoThomson]

Using a natural gas generator in winter might be viable if you are able to capture (most of) the waste heat.

In the future I suspect we could see commercial applications of fuel cells in the home to produce heat and electricity during winter.

CORDIS | European Commission

cordis.europa.eu

 

[eXodus]

Using a natural gas generator in winter might be viable if you are able to capture (most of) the waste heat.

we already got that in Germany for decades. Called KWK (Kraft Wärme Kopplung) Power Heat Coupling
BHKW
Strom is Electric.

You use the engine coolant as heat source for your home heating. The engine coolant also wraps around the exhaust.

It really only makes sense when you consider heat as your primary objective and electric energy as byproduct.

But since heatpumps with a COP 6 came along even the best KWK can't compete anymore.

You only need 1 kwh of solar (about 2-4 cents) and 8-10 cents of battery (Lifecycles * kWh / cost of the battery) to produce 6 kWh of heat.

A heatpump with solar battery produces heat for 1-2 cents / kWh. Nothing comes close to this - natural gas is a 5-6 cents per kWh of heat (assuming 100% efficient combustion and transfer)

 

[Checkthisout]

Good point! I like the simplicity and regulation already built into an automotive alternator.

If your charging batteries, its kinda a fixed load. Just set the throttle for the output/load you want or put a digital or mechanical governor on it?? Just thinking out loud here. The DC brushless gen head right off the crankshaft is kinda nice, no belts. Of course, yes the setup you mention is WAY simple and easy to FIX.

I live off grid and am my own power company. I do mostly solar but I have a lister clone and they work so well with BLDC motors. One could just mount some hover board motors and be done...though motors are motors and the hours add up fast on generators. No piston motor runs forever with out lots of parts. Thats just life. Its why I'm building a gas turbine from an automotive turbocharger.

Generator = high fuel cost and high parts cost no matter what brand or fuel. I'm off grid and allot of my neighbors are so we are very familiar with the life time of a generator that is used more then just for power outages or camping. A friend of mine runs them 24/7. He changes the oil frequently and mostly partial load but he has to buys them every 3-6 months no matter the brand or style. Time and physics, plain and simple.

Are your neighbors buying honda and yamaha generators?

 

[Checkthisout]

Well, he is working on his solar but off grid life is busier than you would think, especially when your building on raw land and working 40 hrs a week.

As far as the 10k - 20k hour life in your link, I call bull $hit. I wish that was reality but its not. Real world would tell me different. I've had Onans at remote communications sites and there is nothing special about them that gives them magic extended life. Unobtainium alloy rings?

If you drove 70 MPH for 20,000 hours ( which is the easiest life for a motor/constant temp/load ) that equals = 1.4 million miles. Car engines are built WAY better then a $600 generator thats running balls out to keep your fridge cool.

My current Gen has 800 hrs and its burning oil and making lower end noise. I have change the oil 16 times in it (every 50 hrs).

I ran a honda i2200 my first summer off grid and wore it out just running a window unit for the summer.

Making your own power is pricey. I am VERY grateful for the solar tech we have now.

What wore out on the Honda and was it new or used?

 

[sunsurfer]

What wore out on the Honda and was it new or used?

Using it 24/7 wore it out. Rings I am guessing, still haven't torn it down yet. I got it new - It started using oil and getting hard starts, fuel usage went up. No bad engine noise though, rougher lower speed running! I currently have a preditor 3500 and its gotten engine noise now. Those rings can only scrap up and down the cylinders so many times before they wear out. Its simple math. Hondas seem to have the best motors hands down. I see worn out Honda's in the adds all the time. People want to much money for them even after they are tired.

I hate running the generators now. Stretch the solar/batts out where ever I can.

 

[Hedges]

If you drove 70 MPH for 20,000 hours ( which is the easiest life for a motor/constant temp/load ) that equals = 1.4 million miles. Car engines are built WAY better then a $600 generator thats running balls out to keep your fridge cool.

My current Gen has 800 hrs and its burning oil and making lower end noise. I have change the oil 16 times in it (every 50 hrs).

I pulled heads from 1997 Sable Vulcan engine at 170,000 miles (equivalent to 2400 hours at 70 mph). I dropped out one piston, with the intent of replacing rings.
With a single ring reinserted in the bore, I checked end gap. It was 4 mils above new spec dimensions, indicating 1 mil change in diameter.
Top vs. bottom of the bore, 4 mil difference in end gap, indicating 1 mil taper in diameter.
Far less than service limit. I consider it barely broken in.

Cast iron can give you that.
Is your current generator cast iron, cast iron sleeve, or aluminum bore?

Of course an 1800 RPM engine could last longer. Probably more than twice compared to 3600.

The high hours Onans maybe do happen, but just a small percentage, several sigma from the mean?

Certainly PV is nicer. Just doesn't always produce.

 

[Checkthisout]

Using it 24/7 wore it out. Rings I am guessing, still haven't torn it down yet. I got it new - It started using oil and getting hard starts, fuel usage went up. No bad engine noise though, rougher lower speed running! I currently have a preditor 3500 and its gotten engine noise now. Those rings can only scrap up and down the cylinders so many times before they wear out. Its simple math. Hondas seem to have the best motors hands down. I see worn out Honda's in the adds all the time. People want to much money for them even after they are tired.

I hate running the generators now. Stretch the solar/batts out where ever I can.

Do you have an hours approximation and an approximation of the average load?

Please share what you find if you end up tearing it down.

If you're an Ebay guy, you can sell the components for a pretty penny and recover some costs.

I also suggest cleaning the carb and checking the valve lash and of course a compression test.

 

[Checkthisout]

I pulled heads from 1997 Sable Vulcan engine at 170,000 miles (equivalent to 2400 hours at 70 mph). I dropped out one piston, with the intent of replacing rings.
With a single ring reinserted in the bore, I checked end gap. It was 4 mils above new spec dimensions, indicating 1 mil change in diameter.
Top vs. bottom of the bore, 4 mil difference in end gap, indicating 1 mil taper in diameter.
Far less than service limit. I consider it barely broken in.

Cast iron can give you that.
Is your current generator cast iron, cast iron sleeve, or aluminum bore?

Of course an 1800 RPM engine could last longer. Probably more than twice compared to 3600.

The high hours Onans maybe do happen, but just a small percentage, several sigma from the mean?

Certainly PV is nicer. Just doesn't always produce.

My experience with Onan anything is the engines are good for about 800 hours until they start burning loads of oil and losing compression.

If the OP is having issues at 800 hours, then that just again confirms what I have found the last 30 years.

1) 3500 hours is equivalent to 100k

2) Diesel Yanmars wear out about 3500 hours.

3) And more fun facts I can't think of.

I maintain around 30 Honda 2000 generators that get run hard and put away wet. They have issues when the oil doesn't get changed and checked as all small engines do.

Not saying surfer neglected his 2200 but if he actually wore one out then it had a loooooottttttttttt of hours on it. I'm guessing in the neighborhood of 4-6000 hours at a relatively higher load.

 

[Checkthisout]

I would definitely want heat off grid but could do without a/c even in the hottest climate.

Dietary changes and regular vigorous exercise greatly increase heat tolerance. At least for me...and a good swim hole....

 

[sunsurfer]

1) 3500 hours is equivalent to 100k

Going by the 70 MPH bench mark which is light load for a car engine, I get 3,500 hrs x 70 MPH = 245,000

Of course, car engines are built WAY better than small generator motors. As the saying goes, your mileage may very.

 

[Checkthisout]

Going by the 70 MPH bench mark which is light load for a car engine, I get 3,500 hrs x 70 MPH = 245,000

Of course, car engines are built WAY better than small generator motors. As the saying goes, your mileage may

Just checked our 2013 diesel.

97,000 on the odometer.

 

[Hedges]

Those are probably hours consisting of 60 minutes each.
My old Caterpillars have "hour" meters, but those are really revolution counters.
Perhaps most of your engine hours were at relatively low RPM, cruising.
So not as comparable to (non inverter) generator hours. Assumed freeway speeds would come closer, but still varies with transmission gearing; load and hills.

 

[byteharmony]

How about a generator that has only 1 moving part and is simple to rebuild? What if it could be build cheaply? Efficiency is not good but if you combine heating water/air it could fair fine.

Wood Fueled Battery Charger

I've been working on a design for months now. Anyone interested in helping me design a test build? Goals 1 - Simplest possible (few moving parts) power from wood source while also heating water. 2 - Keep cost down 3 - Use off the shelf parts 4 - Automated 5 - reliable hours of use and easy...

diysolarforum.com

I can't wait to read this, would be amazing for my cabin friend. I even have 140 archers of wood that could be fun to use this way .

So so I think Honda makes inverter based DC only portable generators, I forget the voltage. It’s very common in populated areas during power outages telco companies roll them out and plug them into booster stations out on the telco lines. On our road it’s common to see Comcast chain up a generator to the pole to keep the area internet going.

I even stopped one storm and filled it up and fired it up. I can’t work if I don’t have the internets.

Looked, haven't seen that with a quick google search, any links?

Micro-CHP was the next big thing a few years ago. Gas utilities and propane vendors were hyping them. Figure 2 in this technology snapshot (PDF) has a nice graph showing type (fuel cell, internal combustion, Stirling, microturbine, etc.) and power rating. I have no idea how many of those vendors are still around, though Blue-Gen looks to be active in the UK.

From what I'm reading about generators being disposable maybe adding heat coupling to the unit would be a pain?

FWIW, the Generac PowerPact 7.5 kW (LP) / 6 kW (NG) is rated at 117 cu ft of NG per hour at full 6 kW output. So that's about 5 kWh per therm, or 14 cents/kWh if your therms cost 70 cents (a great price, btw, Henry Hub futures are trading around 60 cents/therm today). People figure a small Generac will last ~3000 hours, or 18,000 kWh at full load. That adds another 11 cents/kWh in depreciation. Then you have maintenance costs (free labor, ha), repairs, etc.

Thx for the numbers!!

we already got that in Germany for decades. Called KWK (Kraft Wärme Kopplung) Power Heat Coupling
BHKW
View attachment 118965 Strom is Electric.

You use the engine coolant as heat source for your home heating. The engine coolant also wraps around the exhaust.

It really only makes sense when you consider heat as your primary objective and electric energy as byproduct.

But since heatpumps with a COP 6 came along even the best KWK can't compete anymore.

You only need 1 kwh of solar (about 2-4 cents) and 8-10 cents of battery (Lifecycles * kWh / cost of the battery) to produce 6 kWh of heat.

A heatpump with solar battery produces heat for 1-2 cents / kWh. Nothing comes close to this - natural gas is a 5-6 cents per kWh of heat (assuming 100% efficient combustion and transfer)

I wonder with the use being so sparse in my case, would the radiator actually become a heat sync while it waited to fire making the heating part of a generator more of a pain the pleasure?

 

[sunsurfer]

Just checked our 2013 diesel.

97,000 on the odometer. View attachment 118996View attachment 118997

Looks like driving hour you averaged about 23 mph.