Notice. New forum software under development. It's going to miss a few functions and look a bit ugly for a while, but I'm working on it full time now as the old forum was too unstable. Couple days, all good. If you notice any issues, please contact me.
norcold Guru Joined: 06/02/2011 Location: AustraliaPosts: 670
Posted: 08:24pm 13 Mar 2011
Copy link to clipboard
Print this post
Have toyed with the idea of using compressed air to store energy on a small scale,a number of energy companies are doing so on a large scale . Perhaps a plastic tank buried underground, air supplied from diversion power off a solar-wind-battery setup.Than used to drive a air generator to maintain batteries charge when wind and solar fail.Anyone tried such?We come from the land downunder.
Vic
MacGyver Guru Joined: 12/05/2009 Location: United StatesPosts: 1329
Posted: 10:51pm 13 Mar 2011
Copy link to clipboard
Print this post
[Quote=norcold]Anyone tried such?
Yup; tons!
. . . . . Mac
Nothing difficult is ever easy!
Perhaps better stated in the words of Morgan Freeman,
"Where there is no struggle, there is no progress!"
Copeville, Texas
norcold Guru Joined: 06/02/2011 Location: AustraliaPosts: 670
Posted: 07:42am 14 Mar 2011
Copy link to clipboard
Print this post
MacGyver. Perhaps I should reword my question, I would appreciate any info, links etc pertaining to the use of compressed air to store solar or wind power when batteries are "full". In particular details or a link to a working small scale (backshed)setup. Cmon helpout a OZ plumber(retired)We come from the land downunder.
Vic
Tinker Guru Joined: 07/11/2007 Location: AustraliaPosts: 1904
Posted: 02:28pm 14 Mar 2011
Copy link to clipboard
Print this post
One thing to consider is pressure loss at flexible air hose connections. On my shop compressor the tank pressure holds for a while when the hosepipe clamps are all re tightened but that condition never lasts long
I doubt an air driven generator would run for long from the said plastic tank. Even a compressed air divers tank at a few thousand PSI has a limited power storage to feed an air motor with a reasonable load on it for long periods.
Still, it might be fun finding out if the idea has merit Klaus
norcold Guru Joined: 06/02/2011 Location: AustraliaPosts: 670
Posted: 08:20pm 14 Mar 2011
Copy link to clipboard
Print this post
Imagine there will be many setbacks and problems to solve before a working system evolves. Have been off the grid for 4 years now, moved out of town, 48v battery system through 4200watt cont. inverter. Runs fridge freezer lights microwave etc even MIG welder (small)& 2.5hp air comp. On clear sunny days batteries are full by 1pm thus looking for ways to store that excess power. Am adding 2 small wind mills to this. Large scale systems are evolving using underground mines, used up gas fields etc to store the compressed air. But there doesn`t seem to be any backyard working systems. Tried googling & yahooing. Past posts on this and other forum show some interest and experiments, just do not want to reinvent the wheel.We come from the land downunder.
Vic
MacGyver Guru Joined: 12/05/2009 Location: United StatesPosts: 1329
Posted: 10:35pm 14 Mar 2011
Copy link to clipboard
Print this post
norcold et al
The rest of the crew here already knows this about me and I've explained it before, but I don't remember where it's posted, so I'll explain it again.
Simply put, I (used to) build windmills that compress air. I build a three-blade, up-wind device with what's called a "swash plate" on the main shaft. As the shaft spins, the swash plate wiggles from fore to aft and drives a small home-made diaphragm pump that pumps a "little" spurt of air each time the blade goes around.
The air is chambered in an on-board check valve body and then goes down a flexible tube to a copper line with a ball valve on it. When I want to stop things, I merely close the valve and the pump pumps against a dead head of air and stops within only several turns.
There is about 120 degrees of flexibility in the hose, which means you have to point the thing in the area of greatest average wind source, which for me is easy as I live on the West Coast of California and there's a sea breeze out of the west, northwest or southwest nearly daily except for the occasional "Santa Ana" about two days a year in which there is an on-shore flow.
At any rate, the little spurts of air collect in a GIANT accumulator so as to be of some use down the road. I'm a (retired) plumber and have access to many used (but not leaking) water heater storage tanks. I just tie them together in parallel and use check valves to keep any occasional leak from depleting the entire system of air pressure.
Next, I build a small "steam" engine and run the compressed air through that, which is coupled to an alternator and that lets me run for however long the air lasts charging my deep-cycle battery.
The whole process involves several steps, but when you live on a yacht (land yacht) you have to do things in a small way, so the air-pump windmills actually make sense.
I set my blade pitch at 45* as a rule, because I'm after start-up torque and don't give a hang about speed; all I do is pump air!
I'm moving into a new house in a couple of weeks and I'll be building another complete rig, so watch for the post. I'll be building a smallish axial-flux alternator for the project and will post that build as well. Everything I build is really (read that REALLY) small, thus the projects are mostly for "show-'n-tell". If you want to up-size things to make them work for your particular needs, have a go at it. The theory doesn't change with the size.
Hope that helps you out some.
. . . . . Mac
Nothing difficult is ever easy!
Perhaps better stated in the words of Morgan Freeman,
"Where there is no struggle, there is no progress!"
Copeville, Texas
norcold Guru Joined: 06/02/2011 Location: AustraliaPosts: 670
Posted: 04:44am 15 Mar 2011
Copy link to clipboard
Print this post
Mac,
Many thanks. Your first reply set me to look up your profile and from there access to your earlier posts. Initially on searching the forum I had restricted the hits by searching compressed air energy storage(CAES). But that restriction had led me to posting on the forum and thus getting the feel of the forum. This shows the strength of the forum and the way the individual profiles can assist newcomers such as I. Take my hat off to the administrators. I guess both our interest in CAES comes from our plumbing background. I am going along the lines of using a air tool to power a PMA. The rpm and torque as well as the air consumption can be simply valve regulated. The excess power would be converted to air by a simple 240v AC powered compressor switched by the diversion capabilities of my Solar controller(Outback Power MX60). Unfortunately I`d disposed of all the old hot water tanks I`d replaced, thus my thinking of laying a long corrugated plastic tank in a trench buried underground as air storage. Again I thank you and will in future save asking for repeated posts by more clever searching. I guess like the Englishmen who wanted to be Irish by having half his brain removed but accidently getting it all removed.
She`ll be right mate!! We come from the land downunder.
Vic
dwyer Guru Joined: 19/09/2005 Location: AustraliaPosts: 574
Posted: 10:25am 15 Mar 2011
Copy link to clipboard
Print this post
Norcold
How about this one ?
Dwyer
VK4AYQ Guru Joined: 02/12/2009 Location: AustraliaPosts: 2539
Posted: 01:23pm 15 Mar 2011
Copy link to clipboard
Print this post
Hi Norcold
I picked up a trailer load of 6 inch poly water main pipe of cuts that would make good air tanks with the ends blocked off, just a suggestion.
Many years ago I ran a compressor off a VAWT into a very large receiver I picked up at auction, I tried all sorts of air motors but found them very inefficient on air, in the end I used a small steam engine with an expansion valve governor it was the best.
All the best
BobFoolin Around
norcold Guru Joined: 06/02/2011 Location: AustraliaPosts: 670
Posted: 05:39pm 15 Mar 2011
Copy link to clipboard
Print this post
Hi Tinker,Dwyer & Bob,
I have piped my compressed air from compressor to a number of air outlets (for tool use) around my workshop using ordinary 20mm poly water pipe and poly fittings, and that has worked without leaks for many years. It`s flexible tough doesn`t rust and esy to run(heath & safety may object). Have also used PVC water pipe and fittings without problems in the past. With a plastic welder and a trailer load of poly offcuts, well possibilities. Currently have a Southern Cross windmill pumping our household water from a dam to a tank, had replaced its brass pump(gone brittle with age) with a length of PVC pipe and a machined soft plastic piston using readily available poly non-return valves. That`s been performing without dramas for 6 months. Should be able to construct a air pump along those lines(much closer tolerances),that may solve the problem of swinging a rotary compressor directly from the mills blades.You fellows are getting the old grey matter working. We come from the land downunder.
Vic
MacGyver Guru Joined: 12/05/2009 Location: United StatesPosts: 1329
Posted: 04:56am 16 Mar 2011
Copy link to clipboard
Print this post
norcold
Be careful running any pressure much above 40 psig when using PVC plastic pipe above ground. The problem is, if you run into it with a forklift or anything else capable of crushing or cracking it, it becomes a fragmentary grenade and will shoot shards of sharp plastic all about your shop and possibly through your body.
Unless you're going to build something with a wind "footprint" (swept area) of several square meters, I've found that a diaphragm pump works best. Piston pumps have too much friction and have wear problems (lubrication) whereas a diaphragm is merely a slab of rubber that bounces back and forth inside a housing.
I usually design my air pumps with a small return spring so as to give my windmill a little assistance for half its revolution. In heavy wind, it doesn't matter much, but on light days, every little bit helps.
. . . . . MacNothing difficult is ever easy!
Perhaps better stated in the words of Morgan Freeman,
"Where there is no struggle, there is no progress!"
Copeville, Texas
norcold Guru Joined: 06/02/2011 Location: AustraliaPosts: 670
Posted: 08:57pm 16 Mar 2011
Copy link to clipboard
Print this post
Mac,
We come from the land downunder.
Vic
norcold Guru Joined: 06/02/2011 Location: AustraliaPosts: 670
Posted: 09:38pm 16 Mar 2011
Copy link to clipboard
Print this post
Mac
No I`d use poly pipe not PVC for the reason you outlined. I remember when poly first came out in OZ, brass fitting were terrible, poly would split, some ants and soldier crabs would eat it etc etc. But it`s come of age, because I live in irrigated farming area there is many miles of it, brilliant pipe. Have 2 wind turbines coming from film next week, am looking forward to getting one of them up pretty quickly. Up till last year, solar was ample but we had a very cloudy windy year, thus am going with electric mills to supplement the solar. As am 1.5km downwind of a hilly range that is 100m higher than my site, have acceptated wind will only ever be a supplement at my site. Installed a 200w mill here back 4 years ago, it has shown wind has some potential here, be a lot better up on those hills. With the compressed air project I`ll explore the air driven PMA concept with present air storage firstly, but at this early stage feel the storage of air will be the biggest challenge to have a working system. We come from the land downunder.
Vic
MacGyver Guru Joined: 12/05/2009 Location: United StatesPosts: 1329
Posted: 10:18pm 20 Mar 2011
Copy link to clipboard
Print this post
norcold
My prison sentence (marriage) is almost over and I hope to be on my own and building again within a couple of weeks. If you can wait that long, I'll try to get some builds going and continue posting to the 4m where I left off about 7 months ago.
With no machinery (all in storage so ex-wife didn't trash everything), I've been only drawing and dreaming. That all changes as soon as my divorce is "final". I"m hoping that will be this Tuesday afternoon.
. . . . . MacNothing difficult is ever easy!
Perhaps better stated in the words of Morgan Freeman,
"Where there is no struggle, there is no progress!"
Copeville, Texas
yahoo2 Guru Joined: 05/04/2011 Location: AustraliaPosts: 1166
Posted: 02:00pm 24 Apr 2011
Copy link to clipboard
Print this post
We used large propane gas tanks but you really need a good dryer installed or they rust out.
Temporary storage was 45 Kg propane cylinders with a gate valve and ryco quick coupler on top. Chuck a tank rack and a couple of charged cylinders in the ute. One will run the air tools and the other will fully inflate a tractor tyre.
Commercial air storage farms use similar tanks for low pressure, then boost the pressure, cool the air and store it at massive pressures in gangs of thick walled vertical pipes.
NASA run their wind tunnel facility on compressed air, I'm sure I've seen a video on the internet somewhere. 5000 psi for the hyper-speed tunnel (don't quote me on this, memory is a bit hazy) I'm confused, no wait... maybe I'm not...
Oscar4u Regular Member Joined: 23/02/2011 Location: New ZealandPosts: 42
Posted: 10:47am 25 Apr 2011
Copy link to clipboard
Print this post
Hello Norcold
The ultimate is an old boiler or something of that nature. With the cost of scrap and transport this is not cheap however. Compressed air can be deadly, something that absolutely scares me. Here propane 15 kg propane bottles are cheaper to buy new than to recheck. Hence heaps available. But plumbing them together a little bit of saga. Anothe source of steel bottles is a refrigeration company. Freon etc bottles are never reused. What pressure are you thinking of storing? I burried a plastic 44 gal drum in the ground, filled with water and run 50m of plastic air line throught it. Theory is that cool air is easier to get moisture out of. Seeing as you are not using a compressor that is not an issue though. Best wishes
OscarOscar4u - for all your rotary cowshed repairs
norcold Guru Joined: 06/02/2011 Location: AustraliaPosts: 670
Posted: 11:37pm 25 Apr 2011
Copy link to clipboard
Print this post
Some old boilers in old mining areas around where I live, but the cost of transport rule them out. Cannot see why not a corrugated plasic tank buried down a couple of meters, with the soil supplying the strength to contain the pressurised air,the corrugations to stop the soil collapsing the tank when not pressurised, the plastic only the seal. Corrosin would be no problem, thus no need to remove moisture except perhaps an oulet at the bottom for an occasional drain using the compressed air to force the water out through a valve above ground. Comes down to cost and size of storage whether the idea has some merit. Water using a pump, hydro generator and two water tanks may be the way to go as I`m fortunate to have a hill close by to give me some head. Have batteries here that are fully charged by 1pm on a sunny day, thus another 4 hours of solar power going to waste each day. A couple of wind turbines having their power wasted also, but do have good cold beer. Pity I wasn`t on the grid than could sell the power. But I wonder how long that would last if one was making money out of power rather than paying to use it. I think currently in QLD you can get 44c/Kwhr but pay a max of 26c/Kwhr when using. Is the object of these subsidies to break the power companies, to give them an excuse to up the rates or to appease the watermelons? I know no politics but I`m a bloody proud redneck.
Perhaps my thinking has some flaws, it usually has, but than past stuff ups never discouraged this tinkerer from making more. We come from the land downunder.
Vic
Oscar4u Regular Member Joined: 23/02/2011 Location: New ZealandPosts: 42
Posted: 08:08am 30 Apr 2011
Copy link to clipboard
Print this post
Hello Norcold
What size tank and pressure were you wanting to do? I think it has potential lethal consequenses. The power in compressed air is tremendous. In a plastic tank your margin of safety would be nil and even a few meters down would not want to stand close to it. Sorry to pop your bubble. Cheers
OscarOscar4u - for all your rotary cowshed repairs
MacGyver Guru Joined: 12/05/2009 Location: United StatesPosts: 1329
Posted: 05:05am 01 May 2011
Copy link to clipboard
Print this post
norcold
Before you decide to use compressed air as a motive force, it would be good for you to build a small engine or two to see how big a unit you will need to power your generator.
As soon as I finish a couple more projects, i'll be embarking on building a small "wobbler" or "oscillating" air engine, which can be used either as a pump or as an air engine. It will power an alternator or any other appliance that needs rotational input. A lathe is nice to have to build these little engines, but not abolutely necessary as I will attempt to show here on the 4m.
I have already started building the parts for one and it uses a square extruded aluminum tube as the cylinder. The piston is a piece of oak milled to a running fit of about .001".
In these little engines, the cylinder wiggles back and forth with the motion of the piston end, which is tied to the crank. As the cylinder glides from side to side, a single port in its inside top end shuffles between the intake and exhaust ports and that's about all there is to it.
Lubrication, always a problem with most engines, is not so much a problem with oscillating ones as the sliding surface area is great and it holds more lubricant than traditional designs.
The engine can be used directly coupled to the windmill too and it becomes a very effecient air compressor.
. . . . . MacEdited by MacGyver 2011-05-02Nothing difficult is ever easy!
Perhaps better stated in the words of Morgan Freeman,
"Where there is no struggle, there is no progress!"
Copeville, Texas
norcold Guru Joined: 06/02/2011 Location: AustraliaPosts: 670
Posted: 05:54am 01 May 2011
Copy link to clipboard
Print this post
Oscar4u,
Buried down a couple of meters I don`t see a problem, but than I might be a thrill seeker. I see the storage of air as the main bottleneck, that must be sorted out firstly, generators and motors can be trialled on normal air tanks. But still have the other option of water turbine, pump and tanks. Lots of thinking and having ideas pass around may solve this.We come from the land downunder.
Vic
Notice. New forum software under development. It's going to miss a few functions and look a bit ugly for a while, but I'm working on it full time now as the old forum was too unstable. Couple days, all good. If you notice any issues, please contact me.
Print this post
