[Sustain] [Fwd: RE: [Fwd: Compressed air car]]

David F david at fridley.net
Fri Jul 18 15:08:29 PDT 2008 

Don,

The heat issue is with the compression and storage of the air itself, not
the operation of the motor. When a gas is compressed, it heats up, and
either this heat is retained in something like metal or molten salt, or it
has to be rejected to the atmosphere through heat exchanges, where its
usefulness is lost. If the heat is ejected (which is the only technically
feasible process we have now), then when the compressed gas is released, it
has to be heated up because gas that is decompressing gets much colder, and
motors or turbines can't take being frozen (you've probably seen frost at
the nozzle when you've used those small cans of compressed air for cleaning
electronics). So in the compressed air energy storage projects that exist
today (Iowa, Germany, Alabama), natural gas is used to heat the compressed
air up before it reaches the turbines. Even with the heating, the overall
process is more efficient than burning natural gas directly.

High pressure storage vessels are also a problem, since they have
catastrophic consequences when they fail and thus the engineering
requirements are severe. It's the storage vessels that make the cost of such
systems more expensive than batteries.

Underground storage in airtight caverns is best, and geologically, old salt
dome formations (such as the ones we use to store natural gas in) are very
suitable. They are very stable geologically.

It seems unless small scale adiabatic (that is, no heat loss) storage could
be figured out, the efficiency of a small system for power generation would
likely be very low. First the PV or wind would have to drive a compressor to
compress the air, the engineering of the pressure vessel would require some
dealing with heat ejection, then energy would be needed to heat the air up
again before driving a small motor to generate DC power, then pass through
an inverter to AC. Manufacturing of the compressor, pressure vessel and
motor entail environment impacts beyond the boundary of the compressed air
system, so to weigh the tradeoffs with batteries, this would have to be
considered as well.

Storage of intermittent energy sources is indeed going to be a major
challenge to bringing true renewables into play for a 24/7 economy.

David


-----Original Message-----
From: Don Eichelberger [mailto:done7777 at sbcglobal.net] 
Sent: Friday, July 18, 2008 1:51 PM
To: Jeanne; david-fridley.net
Cc: sustainability at sfgreens.org
Subject: Re: [Fwd: RE: [Fwd: Compressed air car]]

Thanks, Jeanne and David-

I found this very interesting, thank you.  I do have some questions.

I am more interested in the compressed air motor as a decentralized 
stationary energy source that can act as an emergency back-up, like a 
battery but without the toxins.

It seems that, as a stationary source, some type of heat exchanger 
technology could be devised that could provide hot water as a 
byproduct.  Either submerge the motor in water or through use of 
cooling coils, it seems the heat could be made useable.  Heat sources 
would be from motor friction and compression of air molecules, right?

Couldn't such a motor be made to operate more coolly by using the air 
to cushion moving parts?

I don't understand the part about heat ejection having to heat the 
air up again on decompression, can that be explained in lay terms?
It seems if there is already a less efficient (50%) design that can 
deliver energy density equivalent to lead batteries, but without the 
toxins, is making huge steps.  I would be interested in checking out 
the midwest studies you referred to.

As for geologic storage, could such geological formations be made 
seismically unstable storing air at pressures of 2500 psi or more?  I 
am thinking more smaller, less centralized storage unit, say at a 
local market, that can be fed with a small windmill or solar panel 
powered pump for emergency power back-up for lights and refrigeration.

I look forward to hearing your thoughts.

Thanks again,

Don

At 10:15 PM 7/16/2008, you wrote:
>Don,
>
>Here's David Fridley's response to my query on compressed air energy 
>storage.  Thought you might be interested.
>
>Jeanne
>
>
>-------- Original Message --------
>Subject: RE: [Fwd: Compressed air car]
>Date: Mon, 14 Jul 2008 19:39:41 -0700
>From: David F <mailto:david at fridley.net><david at fridley.net>
>To: 'Jeanne' <mailto:greengal at netvista.net><greengal at netvista.net>
>References: 
><mailto:487BA2C6.9060200 at netvista.net><487BA2C6.9060200 at netvista.net>
>
>
>Jeanne,
>
>Yes, but there are technical challenges of course. The main problem 
>is how to deal with the heat. The best way would be to store the 
>heat with the compressed air, but that hasn't been worked out on 
>large scale. What has been worked out is storage with heat ejection 
>(meaning having to heat the air up again on decompression), which 
>lowers the efficiency to about 50%. This method has about the same 
>energy density as a lead-acid battery, so it's good, but not as good 
>as advanced batteries. But you don't need the same toxic materials 
>as you do for batteries. There's some trials of wind/compressed air 
>storage in the Midwest I've read about, so it's definitely 
>progressed to the demonstration levels. As long as there are 
>appropriate storage conditions (underground caverns being best for 
>large scale storage), then it's a good option.
>
>As for the cars, the compressed air storage mechanism works best 
>with slow release, which is why these cars run on the air only up to 
>35 mph, then rely on the alternative energy source. Since 
>decompressing air cools it, you have built in air conditioning.
>
>David
>
>
>From: Jeanne [<mailto:greengal at netvista.net>mailto:greengal at netvista.net]
>Sent: Monday, July 14, 2008 12:03 PM
>To: Fridley, David
>Subject: [Fwd: Compressed air car]
>
>David,
>
>Don has an interesting question.  Suppose we forget about this as a 
>car, but consider it as a way to store intermittent sources of 
>energy.  Does it make any sense?
>
>Jeanne
>
>-------- Original Message --------
>Subject:
>Compressed air car
>Date:
>Tue, 06 May 2008 22:47:13 -0700
>From:
>Don Eichelberger <mailto:done7777 at sbcglobal.net><done7777 at sbcglobal.net>
>To:
><mailto:ber8832 at aol.com>ber8832 at aol.com, 
><mailto:richard at katznip.com>richard at katznip.com, 
><mailto:greengal at netvista.net>greengal at netvista.net
>
>
>Here are links I said I would send on the compressed air car being
>developed in France.  I am most interested in the motor as an energy
>storage device that's cleaner than batteries.
>
>I'd be interested to hear what you think,
>
>Don
>
><http://zeropollutionmotors.us/?page_id=43>http://zeropollutionmotors.us/?p
age_id=43
>
>http://www.popularmechanics.com/automotive/new_cars/4251491.html?series=19
>
>
>
>Don Eichelberger
>DJ Fix Independent Productions
>
>Green Uprising Blog
><http://www.greenuprising.blogspot.com>www.greenuprising.blogspot.com
>
>My You Tube
>
><http://www.youtube.com/watch?v=ctRp5rGJoUc>http://www.youtube.com/watch?v=
ctRp5rGJoUc
>http://www.youtube.com/watch?v=iySwwyZfDgE
><http://www.youtube.com/watch?v=8r9rK8nPREA>http://www.youtube.com/watch?v=
8r9rK8nPREA
>http://www.youtube.com/watch?v=u5UbnJ0kUqo
><http://www.youtube.com/watch?v=4SktIYTyC1U>http://www.youtube.com/watch?v=
4SktIYTyC1U
>
>My Space
>
><http://www.myspace.com/donnyfix>http://www.myspace.com/donnyfix
>
>Donny Fix del.icio.us book marks
>
><http://del.icio.us/donnyfix>http://del.icio.us/donnyfix
>
>The Hegelian/Marxist goal is emancipation.  Marx said it best in 1843:
>
>"Human emancipation wll only be complete when the real, individual
>man (sic) is absorbed into himself the abstract citizen; when as an
>individual man, in his every day life, in his work and in his
>relationships, he has become a species-being (politically accountabe
>to the whole); and when he recognizes and realizes his own power as
>social powers, so that he no  longer separates this social power from
>himself as political power."
>
>
>
>
>--
>Jeanne Rosenmeier
>415 751-0901
>
>--
>Jeanne Rosenmeier
>415 751-0901


Don Eichelberger
DJ Fix Independent Productions

My Blog
www.greenuprising.blogspot.com

My You Tube
<http://www.youtube.com/DonnyFix>http://www.youtube.com/DonnyFix

My Space

http://www.myspace.com/donnyfix

Donny Fix del.icio.us book marks

http://del.icio.us/donnyfix

The Hegelian/Marxist goal is emancipation.  Marx said it best in 1843:

"Human emancipation wll only be complete when the real, individual 
man (sic) is absorbed into himself the abstract citizen; when as an 
individual man, in his every day life, in his work and in his 
relationships, he has become a species-being (politically accountabe 
to the whole); and when he recognizes and realizes his own power as 
social powers, so that he no  longer separates this social power from 
himself as political power."

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