How to construct a micro liquefaction cryo compressor for gas storage

[Frank S]

This is just a thought and one that may have been discussed before.
the thought of using  natural gas or propane as a fuel for generators  started me to thinking about if there is a mini micro way to liquefy gas such as the natural gas in your supply line for long term storage. or if you have a methane production unit or a gasifier if these could be liquefied for long term storage like LNG or Propane.
My  thoughts were many have wind turbines , solar panels  even hydro, but when the battery bank is fully charged why not if there is a way to say compress methane or other gases even natural gas from your supply line if you have one to liquid for long term storage then this could be used by the engine generators in an emergency or peak times of need
is there such a system? is something a viable idea  you would be only using the excess power produced from your solar or wind generators plus which ever gas you had this would actually be your dump load
Any thought's or Is this a waste of time 

[uber39]

Not a waste of time at all, I seem to remember many years ago , I think it was New Zealand where they used a compressor to fill a tank in the car from the house supply, looked like the compressor I used to use to fill scuba tanks.
      Ian
   

[Geno]

If I'm reading this chart correctly the pressures aren't nearly as high as I thought they would be.

http://home.mchsi.com/~gweidner/vapor-pressure-of-lp.pdf

Thanks, Geno

[Frank S]

This was my line of thinking. Anyone who has a wind turbine  it is almost an absolute given that at some time it will be producing more energy than they can use the same goes with solar and hydro. there is only so much battery storage that is even feasible. Storage or reserve energy as in fuel or electrical energy the problem is the on demand factor. About the only on demand storage that I can see is a way to compress gases fuel or if a person has the real-estate to pump water up hill during times of excess.
Mobile Bob has been talking about low rpm natural gas engines and this started me to thinking about What happens if your back up is a natural gas rig but the pipe line goes down which happens  all of the time, or the use is curtailed during extreme cold periods.

[Frank S]

I suppose with methane you would catalytically convert it into methanol to make it a liquid, But what about gas from a gasifier 
I know that Natural gas as with any other gas can be simply compressed to a point and this may be the simplest way to have a higher volume of storage;
But gas stored by  being liqudified retains its properties better takes up less space and for the most part is safer to store.
There is a guy in New-jersey who has a home hydrogen farm with 3 or 4 huge pressure tanks that he generates his hydrogen to run his car on.

[mobile_bob]

one can liquify propane fairly easily, and contain it just as easily

nat gas on the other hand is another matter entirely, the pressures needed
are something on the order of 4k psi iirc and of course the containment vessel
is an expensive proposition as well.

a while back i found some surplus compressors used to fill natgas automobiles
for around 4-5k dollars, the tanks were several hundred dollars each with capacities
on the order of 10-15 gallons.

i haven't looked at this for a while, but i suspect the prices are still very dear.

still worth looking into in my opinion, because nat gas like any other commodity goes up and down in price according to time of year and demand. it would be nice to buy cheap (compress and store) enough to carry me through the winter months. just not sure that it would be realistic to do so. cost of storage vessels would be very expensive and they don't last forever.

another reason why there ought to be interest in wood gasification, at least one could make gas as needed and not have to figure on liquification and storage issues.

fwiw
bob g

[mobile_bob]

something else i have been thinking about
that is just compressing the natgas to something around 175lbs and store it in as large
of a propane tank as i can find?

maybe a 1000 gallon tank, pressurized to 175lbs would have sufficient capacity to get me through quite a while?

haven't done the math on it yet.

seems like with the delivery pressure of nat gas being something like 1-2psi, a thousand gallon tank pumped up to 175lbs would take a very long time to deplete.

bob g

[BruceM]

I wonder what's new in home hydrogen electrolysis/separation/storage.  That seems a good way to use excess PV/wind power.  Especially if you could have dual fuel (LPG/hydrogen) appliances and switch over easily when you run out of hydrogen.  Pity the hydrogen embrittlement of storage tanks and pipes is such a problem. Oxygen separation and related safety issues are no small problem either. 



 

[BioHazard]

I've seen CNG compressors meant for home use (car refueling) as low as $3000. I think there are some chinese ones on ebay now. The tanks can be really expensive, but, if you're not using it in a car you might be able to get away with using tanks that are past their certification date for cheap. Seems like I've seen those on ebay too.

I like to keep an eye out for "CNG stuff" on craigslist, often industrial stuff goes cheap because most people don't have a source for CNG.

[Frank S]

OK here is a scenario you live in an area where you have really bad winters. you have grid ties IE  gas & elect.
you also co gen your own energy you have your wind gennie your hydro gennie  a roof full of solar panels a bunker of batteries. and a gasifier. ETC,ETC,
it is -30 or colder there has been a huge snow & or ice storm. The wind  gen is locked down due to High winds & Iceing. the solar  are covered with snow & ice. your grid goes down the utility company may take weeks to get the power lines back up. the nat gas has been curtailed or even shut off due to the cold. But you are the survivalist or the world, you have a 500 gallon tank LPG but the delivery could not  be done this year for what ever reason, however  additionally you have been compressing NAT gas to CNG you have been running your gasifier and compressing that gas as well. but getting out in the cold to fire that thing up while it is buried under 3 feet of snow is just not going to happen Maybe you are ILL or have a sick family member. even though all of your externals have been put out of commission your battery bank is not going to die because you have your reworked ST running on a low RPM engine that can run on your stored compressed fuel that your Wind,/ solar & hydro provided the energy to do so with the excess electricity that you did not use and would have otherwise simply dumped possibly through a heat sink.

[Frank S]

Maybe for a compressor you found an old diving tank compressor that was no longer certifiable for filling divers tanks.

[Tom Reed]

Another source for compressors is fire stations, the newer SCBA's run 4000 psi and the compressor we have goes to 6000 psi. We use nice light tanks that need to be regularly certified too. The regulators pressurize the masks to around .5 psi.

[fabricator]

The one thing that has always made me shy away from LNG is the possible crater.

[AdeV]

The one thing that has always made me shy away from LNG is the possible crater.

It's no worse than having a big tank of gas (petrol), shurely? Better, in fact, because the explosion will tend to go upwards, rather than hanging around on the floor in puddles setting fire to stuff. Take a leaf out of the electricity industry's book: Build a very very strong shed (triple-thick block walls) with a weak roof... if you can make the bang go up, instead of out, then the damage will be limited to a weak (=cheap) roof.

[AdeV]

Rather than compressing natural gas - which seems to be dangerous, and not particularly effective, why not use a Stirling heat pump to cool it to the -162C (-260F) necessary to condense it? I guess for storage you'd still need a container capable of containing the pressue of LNG at room temperature, unless you stored it under cryogenic conditions -  but then you need a constant power source (to run the heat pump), which rules out wind or solar power...