Brainstorming a windmill air-compressor design

I'm interested in energy converter mediums. The one that seems to have the most potential and a fairly simple installation is coupling a windmill ( or simply a propeller) to an air compressor. The tank holds a volume of air for power which can be used right away or stored. Ganging tanks or a large volume bladder increases the potential energy conversion. As a by-product compressing air generates heat and releasing it causes a tremendous drop in ambient temperatures, both which could be directed to whatever served the best function. Many of the components needed already exist. Items like a hundred gallon air tank and a scraped 41cc engine attached to a vertical length of two by four coupled with a "U" yoke to a routed and balanced two by four blade would make an excellent prototype. Anyone have any ideas they'd like to share would be greatly appreciated. I'm going to try and make a working model over the winter and put it up on the Youtube - hopefully in the spring. My channel is Cannibalriot, but remember it's in the spring 2011 I'm shooting for. Let me know what you think, ciao bella!

Interesting.  Of course I'm not sure what you are going to do with all that stored air.  You might want to add an air powered motor and an alternator or generator and some 12 volt batteries.  You will be able to store more energy this way.  Maybe some 12 volt lighting off the batteries?

i like the idea, it has a lot of potential i think. it seems far easier to store energy in compressed air compared to batteries. and like tinknal said if you add a compressed air engine you can get power on demand when its windy, or store it for later use.

The thing to be aware of is entropy.  This is the principle that every time one form of energy is converted to another form of energy, that energy is lost.  For producing electricity for example, it would be most efficient to have the electricity go directly from the generator to the power grid.  Unfortunately, this leaves you to the will of the wind.  The most efficient way to store electricity would be directly to batteries.

Of course batteries are expensive.  Also, pneumatics are very poor energy converters.

That said, if you can store a lot of air for a low cost, it could be a cost effective solution. 

Just a though: it takes a fair amount of torque to run a compressor. This may stall out the blades on a wind turbine. You might want to visit www.windstuffnow.com or builditsolar.com or Hugh Piggot's site.
kent

There are at least 2 companies that make wind-driven air pumps.  I'm not sure if either works at a high enough pressure to be called a compressor.

One is made to pump air through an air-stone to aerate ponds.  The other is made for lifting water from a deep well.  I don't recall the name of either product, but this might be a pointer to help you see what's already out there.

If you manage to get any amount of pressure (it takes a lot to do anything significant apparently) you could look into vortex tubes to provide cooling for a refrigerator  or freezer ( a huge energy gobbler) with the waste hot air being used for whatever..or heating a room with the waste cold air used for whatever.. The temp differentials potentially are very useful - but so far as I can tell nobody seems to have come up with a way to harness these things for more than small jobs such as freezing tissue samples and so forth.  There is some research going on to try to make them feasible for third world countries as they have no moving parts to break down and are  simple to make.  According to the reports I've read, the home made ones tend to be noisy.

If they are, then you could get into thermo acoustics to generate electricity? Part of a news release having to do with the SCORE stove being developed for third world countries..(it's quite amazing, cooking refrigeration AND a small but usable amount of electricity produced in a 20-50 pound appliance they are trying to make so that it could be sold for well under $100)

Researchers in the Department of Electrical and Electronic Engineering at The University of Nottingham are working on the generator's Linear Alternator — the part which turns the sound energy into electricity. The system uses special configurations of magnets which generate electrical energy from sound. Computer simulations of the linear alternator have proved successful, and test models are currently being constructed in the department's workshops.

I've been thinking about this one for a year or two now.. Nothing serious, just thought experiments and a little reading. I've come to some conclusions that I'd like to share..

One thought I've had is to insulate a mass (a chunk of steel or something) and passively heat it by the sun. There would be an air channel with a one way valve in the mass through which compressed air would flow out of storage (the tank) to it's use point (air tool, generator, whatever). Seems to me that this would cause the compressed air to expand more, producing stronger push, more energy.

Also, it seems to me that since there is energy loss at every conversion, I would steer clear of conversions whenever possible. I would switch to air tools in the shop, maybe modify air tool components to do things in the house (blender etc). If electricity is needed, I wouldn't try to generate it in one large generator to feed the whole house. I would probably plum the house with pipe and generate at small micro generators AT THE POINT OF USE.

Donkey wrote:

One thought I've had is to insulate a mass (a chunk of steel or something) and passively heat it by the sun. There would be an air channel with a one way valve in the mass through which compressed air would flow out of storage (the tank) to it's use point (air tool, generator, whatever). Seems to me that this would cause the compressed air to expand more, producing stronger push, more energy.

I don't quite follow what you mean there, donkey? Can you explain what I am missing?  Air can only expand so much.


There are two working projects in the world that use compressed air to store energy last I checked. One in Alabama and one in Germany. There's also one under development in Utah I believe. They use excess electricity to compress air. The project in UT intends to use excess electricity from wind, solar or other sources to drive the compressors. Direct wind power simply does not not develop the torque required to compress air to the pressures they use, about 1000 PSI. That encounters problems with air temperatures rising to something like 600 degrees C. That is too hot and apparently the air must be cooled before being stored in their underground caverns. The way the compressed air is used is to mix it with some natural gas and burn it in turbines.


Air tools themselves have some great advantages for some uses and at the same time are not as good as electric in other uses. They are lighter for the power produced. Cheap air tools are better lasting than cheap electric tools, in my experience. Air is better for things like impact wrenches or for things where a back and forth linear motion is desired, as in a air chisel or air hammer.  An air powered drill will not try to keep rotating (and twist your wrist/hand) when the bit grabs; the air drill just stops or stalls. Air power is what makes a mechanics powered ratchet wrench even possible. Air tools don't have potential for killing you if you stand in a puddle of water when using them.

An electric tool can be used as soon as it is plugged in and it will run as long as the power is available. Connected to the grid like most people are that is virtually forever. Air tools will also run forever, or at least as long as compressed air is available. In order to have run times that will not interrupt the work a large compressor is required.  An air tool requires a certain amount of pressure and a certain volume of air to be used.  A typical small home compressor rapidly runs out of air when used with air motor tools. That is the big drawback to using air to power things around the home. A tool like a nailer or stapler is another matter. They mainly require air pressure from 70 to 120 PSI but very little air volume. To use my air grinders, drills and sanders without inconvenient interruptions I need a compressor whose replacement cost today would be in the order of $1800. That's more than what many folks have spend on their portable power tools.

Running air lines around the house or shop is not as simple as running electrical wires. The air system must be equipped with air dryers for some tools. Some compressors have trace amounts of oil in their output; for some used that is bad. On the other hand air motor tools require some lubrication. Usually a drop or two of oil is added "every so often" by dripping it in the air inlet of the tool. This makes its way out of the tool at the exhaust port, so air tools tend to be a little messy. Not a big deal in the workshop but it might be undesirable with a food blender on the kitchen counter.

Air delivery pipes, like electrical wires, need to have their size increased over distance. The air piping tends to be larger than electrical wiring though. But then wiring to my air compressor is a good size too, 240 VAC 30 amp service.

So, until there is some "magic" breakthrough in a means to compress air more efficiently I don't think there is a general market for home use of compressed air. As a commercial energy storage medium it has promise.

MountainDon Miller wrote:
I don't quite follow what you mean there, donkey? Can you explain what I am missing?  Air can only expand so much.

Air's expansion and it's ability to do WORK is all about heat. In fact, I don't think it's off base to say that compressed air tools ARE heat engines.

When air is compressed, it typically looses it's latent heat as waste to the environment. When air expands, heat is drawn back from the environment again into the expanding air mass until it equalizes with it's surrounds. This effect can be seen whenever you use air tools. Compressors get hot and the tools get cold.
Compressors are equipped with cooling fins, as their ability to compress air relies on their ability to cool it. Conversely, high end air machines require HEATING to work for any length of time as the expanding air can freeze them solid.

This transfer of heat GREATLY lowers the basic efficiency of air systems as the latent heat inside the air is potential energy and transferring it back and forth excludes it from doing work.  There have been attempts to keep the latent heat inside of compressed air systems (the air itself) in order to keep the potential energy, there are some high tech solutions that work to some degree but they are EXTREMELY expensive and overly technical for the home tinker-head..

My thought is: Why not just re-introduce heat from an essentially free source? Air tools do this anyway from ambient heat, why not direct that heat into more efficient expansion?

OK. I get that. A solar collector of sorts to warm the air just before it is used. You are right though, I think it complicates things. 

As it is my compressor has an intercooler to get of the heat at that point. In the winter it's nice in the shop and in the summer it is not wanted so I have a rube goldberg vent system to expell that heat outside.

Have a wild idea of heating up water by using a windmill. I use to work with electronic's and heavy hydaulic's. At first I wanted to use a hydraulic pump, but a leak would spray the surroundings with hydraulic oil. Is it possible to build a compact hi power waterbrake? It has to be sturdy as well. I don't want to hang in the tower once a week.

We bought a windmill air compressor that has a 10 HP compressor and store the air in two 1,100 gallon propane tanks. The 5 blades are over 17 feet long and it works great, started out using it just as a pond aerator but have since switched over some of the electric motors in my shop to pneumatic motors. The Wind compressor is set for 175 PSI. Im in the process of looking for a third storage tank

Markham Cornoit wrote:Have a wild idea of heating up water by using a windmill. I use to work with electronic's and heavy hydaulic's. At first I wanted to use a hydraulic pump, but a leak would spray the surroundings with hydraulic oil. Is it possible to build a compact hi power waterbrake? It has to be sturdy as well. I don't want to hang in the tower once a week.

I am concerned with the complicated drivetrain of wind generators and think a hydraulic drive would really simplify the wind turbine especially if used with a hydraulic accumulator. What I am struggling with is finding a slow speed hydraulic pump.

r john wrote:

Markham Cornoit wrote:Have a wild idea of heating up water by using a windmill. I use to work with electronic's and heavy hydaulic's. At first I wanted to use a hydraulic pump, but a leak would spray the surroundings with hydraulic oil. Is it possible to build a compact hi power waterbrake? It has to be sturdy as well. I don't want to hang in the tower once a week.

I am concerned with the complicated drivetrain of wind generators and think a hydraulic drive would really simplify the wind turbine especially if used with a hydraulic accumulator. What I am struggling with is finding a slow speed hydraulic pump.

Most hydraulic pumps are going to be positive displacement pumps, and should theoretically operate at any speed (In practice, of course there are both upper and lower limitations). A gear pump would probably be the best choice for a windmill.

Depending on the air pressure that you want to store the other method that I tried and was able to get 35 PSI from was using my old 702 windmill. I mounted a goodyear airbag that trucks use as a shock absorber to the botttom of the tower, on the down stroke of the windmill it would push the airbag open and suck the air in through one check valve. On the upstroke it would squeeze the airbag closed and force the air out through a second check valve into the air storage tank. If you try this method make sure you dont try to squeeze the air out on the down stroke or it will bend and or brake the wooded rod on the windmill. Trust me on this one. Once the tank had about 35 PSI it would stall the windmill

Regards,
Gary

The Amish have been using wind driven compressed air for many years to power kitchen appliances.