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Old 11-09-14, 11:51 PM   #11
AC_Hacker
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Default Combined Heat and Power

This Combined Heat and Power idea has been discussed in some degree of detail HERE.

It could save some time.

I'm not sure why The fascination with car A/C compressors for hacking?

Really well designed, efficient, working piston compressors are widely available.

Maybe it's because folks just happen to have a car compressor laying around and want to do something with it.

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Old 11-11-14, 07:30 PM   #12
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Default Use The Google

By the way, if you "Use The Google" regarding the question originally asked in this thread, you will find a really significant amount of information.

Give it a try...

-AC
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Old 11-13-14, 10:09 AM   #13
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The First and Second Law of Thermodynamics say that when converting one form of energy to another, there will always be losses. Converting chemical energy (burning any kind of fuel) to mechanical energy has a lot of lost energy (put your hand next to any running engine ... that is heat energy you are feeling).

We have used these lossey devices ("engines") for hundreds of years because the fuel was cheap and plentiful. Relative speaking, these fuels still are.

Electric to mechanical energy (a motor) is actually pretty efficient compared to an "engine".
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Old 11-13-14, 10:31 AM   #14
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Quote:
Originally Posted by theoldwizard1 View Post
The First and Second Law of Thermodynamics say that when converting one form of energy to another, there will always be losses. Converting chemical energy (burning any kind of fuel) to mechanical energy has a lot of lost energy (put your hand next to any running engine ... that is heat energy you are feeling).

We have used these lossey devices ("engines") for hundreds of years because the fuel was cheap and plentiful. Relative speaking, these fuels still are.

Electric to mechanical energy (a motor) is actually pretty efficient compared to an "engine".
I'm not sure that I see your point here...

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Old 11-13-14, 01:41 PM   #15
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Quote:
Originally Posted by AC_Hacker View Post
I'm not sure that I see your point here...

-AC
Natural gas is chemical energy. Converting it into mechanical energy will never be overly efficient, especially on a small scale.

Power companies buy their "chemical energy" (or nuclear energy) at wholesale and the economies of scale minimize the losses in converting it to electrical energy. Even though there are losses in the electric transmission line and some in the electric motor inside the compressor, it is not likely that a natural gas "powered" heat pump (compressor) will EVER be cost effective !


When fuel cells (which convert NG to electricity directly) become cheap, the above statements probably will go out the window !

BTW, the Japanese have developed small fuel cells because in certain parts of that country electricity is hard to come by (especially when all the nuclear plants were shut down). NG is expensive in Japan, but it those areas it was available.
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Old 11-13-14, 02:06 PM   #16
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We used a number of KWHs of electricity running machines and a few years ago we were burning furnace oil to heat.

Hey, why don't we get a diesel genset and with the oil we were burning and sending up the chimney. Why don't we power the machines at the same time. It actually made economic sense.

The diesel would power the generator providing us with electricity and heat the shop as well with its waste heat. It can make a lot of sense.

Two rationalities came to mind:

1/ The cost of diesel fuel was rising rapidly.

2/ We didn't care for another machine to maintain.


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Old 11-14-14, 12:46 AM   #17
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Quote:
Originally Posted by AC_Hacker View Post
This Combined Heat and Power idea has been discussed in some degree of detail HERE.
Yes, I know a lot about CHP. That is not what I am talking about. I have no plans to generate electricity.

Quote:
Originally Posted by AC_Hacker View Post
I'm not sure why The fascination with car A/C compressors for hacking?
I was just asking what is available. Suggestions?


Quote:
Originally Posted by AC_Hacker View Post
By the way, if you "Use The Google" regarding the question originally asked in this thread, you will find a really significant amount of information.
Yeah, I'm pretty familiar with google. The question originally asked was "anybody ever build a natural gas heat pump?", and thus, google cannot answer that question because I was asking the members of the forum. But beyond that, if you do a search for natural gas engine driven heat pumps you find almost nothing. Most results are about industrial sized gas burning ammonia absorption systems. I'm not asking about commercial systems, I'm wondering if anybody else has ever tried to do this themselves.

Quote:
Originally Posted by theoldwizard1 View Post
(put your hand next to any running engine ... that is heat energy you are feeling).
You seem to be missing the point. Yes, I know exactly how much waste heat an engine produces, that's why I did the math for you in my first post. The engine in this situation is nothing more than a gas burner, that heat is not wasted, I am harvesting it.

Quote:
Originally Posted by theoldwizard1 View Post
it is not likely that a natural gas "powered" heat pump (compressor) will EVER be cost effective !
Do you have any information to back that up? All the math I provided in my first post shows an approximate 50% savings. Is my math wrong?

Quote:
Originally Posted by theoldwizard1 View Post
Power companies buy their "chemical energy" (or nuclear energy) at wholesale and the economies of scale minimize the losses in converting it to electrical energy.
That is not true. Commercial power generators throw away their heat. If you can use that heat for something else to displace a fuel you would otherwise be buying for heat, then you can save significant money. It is also much more efficient energy wise, if you care about that sort of thing.

Quote:
Originally Posted by randen View Post
Two rationalities came to mind:

1/ The cost of diesel fuel was rising rapidly.

2/ We didn't care for another machine to maintain.
I totally agree with you there. On the other hand, they've actually been lowering the price of natural gas! Maintenance is one of the biggest possible issues, but this is also something of a hobby.
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Old 11-16-14, 08:52 PM   #18
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Default York Triathlon

Triathlon (heat pump) - Wikipedia, the free encyclopedia

York made one like this in the late 90's, never caught on.
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Old 11-16-14, 09:01 PM   #19
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My question is this: do you have an abundant supply of free natural gas?

If so, it is economical at any efficiency. At some low temperature, you would not move enough BTU's with the heat pump to keep up with the thermal losses of the home. You could then rev up your engine and harvest the additional heat generated.

If not, most individuals in the field switch from air-source heat pumps to straight gas furnaces at a balance point somewhere around 20 degF due to the shortcomings of the heat pump system. It is just not wise to run the heat pump constantly at low COP when you can cycle a gas boiler or furnace to provide the same heat.

Above this balance point (most of the time in the USA), a heat pump makes sense, regardless of how you power it.
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Old 11-17-14, 07:08 AM   #20
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Quote:
Originally Posted by Servicetech View Post
Triathlon (heat pump) - Wikipedia, the free encyclopedia

York made one like this in the late 90's, never caught on.
From Wikipedia

Quote:
... the Triathlon was driven by a natural gas fueled 5 horsepower Briggs and Stratton engine ...

I actually worked alongside some guys trying to develop a Wankel engine to run the A/C compressor in the late 1980s. The engine would run on natural gas. It was aimed at small businesses (convenience stores, fast food restaurants, etc).

The system worked fine, but there were durability issues. When run continuously, the oil and spark plugs had to be changed every 2-4 weeks ! Also wear on the seals (Wankel equivalent to piston rings) was high.

The motivation was a predicted shortfall of electric power in the SE (check the population growth in GA from 1980 through 2010).

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