What quantities of gas would i require for this....

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58robbo
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What quantities of gas would i require for this....

Postby 58robbo » Thu Dec 31, 2009 8:58 am

Hi there. I'm planning an off-grid home in the Florida countryside. I will have some livestock and i intend channeling blackwater along with kitchen waste and perhaps grass clippings into the same system. Space is not an issue for me and i'll have sufficient solar tubing to heat the feedstock to the optimum temperature. I want to find out if i'll have adequate gas for cooking, back-up hot water and to run and an absorbtion refrigerator and airconditioning system. Heck, while i'm stretching the realms of possibility, i may aswell ask how much gas i'd need to produce to run a small automobile.

Would appreciate some input

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Bob
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Re: What quantities of gas would i require for this....

Postby Bob » Thu Dec 31, 2009 12:25 pm

This calculator can give you a ball-park estimate.

58robbo
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Re: What quantities of gas would i require for this....

Postby 58robbo » Thu Dec 31, 2009 11:39 pm

Thanks Bob,
I've aready used the calculator and determined that I could get around 200 cu ft per day. In addition, many of my neighbors have livestock and i'm sure i could hussle an infinite supply of feed to produce more gas.

What i really want to find out in how much gas is used up per hob for cooking. I wanted to find out how much gas i'd need to run and absorbtion chillers and how much gas i'd need to drive my 4 cyl ranger about town

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Bob
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Re: What quantities of gas would i require for this....

Postby Bob » Sat Jan 02, 2010 3:52 pm

Approximate heat content of methane (not biogas, but methane) is about 1,000 Btu/cu ft. So 200 CF/day would be about 200,000 Btu/day

A small burner on a gas range consumes about 5,000 Btu/Hr (or ~ 5 CF methane). A large burner about 12,500 Btu/Hr.

I'm not familiar with small residential scale absorption chillers, but google finds rotartica, for example, a 4.5 KW (1.28 Ton) model that looks like it might work. I don't know what kind of cooling load you have, but if my back-of-envelope calcs are approximately right, you could possibly run a 2.5 ton unit for up to 5 hours/day. (2.5 Ton * 12,000 Btu/Ton / 0.75 COP ~ 40,000 Btu) It looks like the smaller rotartica unit could run on about 20 CF/hour. A gas-fired refrigerator might be another option.

For your ranger, heat content of gasoline is about 124,000 Btu per US Gallon. So your 200,000 Btu/day would be equivalent to about 1.6 gallons/day.


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