Compressed Air Storage

[richhagen]

Well I had a bit of time this Saturday with my son, so we needed a small project to keep us out of trouble.  I have been so busy as of late that I've had little time to even follow the board, let alone post or build anything of utility, but I had a Saturday with my son, a few hours to kill, and a 1.7 HP air motor collecting dust.  We also had a 1hp 24V pm motor I had recently gotten from another project, so this seemed like a natural fit to give it a try.  I sold him on the idea that we could probably build a charger that would run his x-box 360 on compressed air.  We already have run it on solar in a tent when camping just because we could, but compressed air might be a nice science fair project for him at some point, and it has not been the easiest to keep his interest in the solar and renewable energy projects that I enjoy as a hobby. 

I lack the craftsman skills of many members here, and I did not drag the camera out until we had it all put together, but I took a few pictures and made this post in case it is of interest to anyone, or anyone has any good ideas to improve or modify it. 

I rigged up a couple of fittings on the air motor to connect it with the quick connect hose on the compressor and a valve to throttle it and we gave it a whirl.  I couldn't find the muffler for the exhaust, and I didn't add a filter and oiler for testing, but it purred to life with a sound like a gas motor scooter and the shaft spun rapidly.  It was an interesting start for us. 



We had a sheet of 12 by 48 inch 1/4 inch plate steel rusting in the basement of one of the buildings so I collected that up and we cut a piece off to make a base.  The air motor was a Gast 4AM series motor with a C56 mount, so I had to cut a hole in the center for the motor to mount to.  We did not have anything the exact size, but we found an old varnish can to use as a rough template to come close and winged it.  It worked out.  I cut the scrap into two gussets to hold the motor mount plate to the base.  All of that took a lot less time than drilling holes to mount the air motor as it turned out. 

First we drilled a couple of holes to mount the air motor, and after a trip to the hardware store to find a couple of short 3/8 inch bolts to hold it in place we bolted it in.  Next we placed the pulleys we had on the motors.  The ratio of the pulleys should be the ratio of the diameters.  I had thought they would make a two to one ratio, but empirically it wound up being about 1.75 to 1.  The air motor has quite a range of speed, although maximum torque is at about 250RPM and the maximum speed on the ratings is at 3000rpm.  The 24V motor is one HP at 1750RPM according to the specs so we tried putting the larger pulley on the air motor and the smaller pulley on the 24V motor, figuring the 24V motor would bog down the 24V motor and hold down its speed once it hit cut in voltage.  The 24V motor had a foot mount with slotted holes.  We lined the motors up with the belt on them so that we could drill and tap holes for the 24V. motor.  We drilled and tapped two of the holes on an angle, I really do need to sharpen the drill bits on the set at my house.  We only completed about half of the mounting holes, but I figured it was enough for a simple test and we could add the rest later and besides it would have to come apart to be painted anyway.  By now it was starting to get dark, where does the time go? 



We dragged out a couple of six volt golf cart batteries and connected them in series for 12V and I rigged a multimeter to keep tabs on the voltage. 

The next problem was that we did not have a large rectifier for this, although I did have a spare 30 amp meter I could borrow.  I did have a bunch of diodes from I had bought as surplus for use on solar panels.  We wound up rigging about ten of those in parallel and mounting them along with the amp meter on a small plywood block to test with.



We wired up the output of the 24V motor through the rectifier and amp meter on the positive side and directly through the battery for the negative output.  We tested the polarity by using a red led across the leads and spinning it by hand.  I switched the multimeter to be hooked across the input to the rectifiers and the negative of the battery to monitor the voltage of the generators output.  Once we had everything together an old 20gallon air compressor was fired up and charged to 120PSI.  The pressure regulator was set to 100PSI although I worried about the line resistance in the 100 feet of 3/8 inch air hose, which is really two 50ft sections with 1/4 inch fittings on the ends.  This is the entire setup.



We through the valve and it came to life, spinning up as the valve was opened.  The voltage on the meter came up to about 12 volts.



It flared up past ten amps and then quickly settled to 10 amps.  I could not get it to output more than that. 



The compressor kicked on as the tank pressure depleted, and it seemed to me that the 1/3 hp motor of the compressor was just able to keep up with the air needed for the 10 amps into the battery, which would make for rather dismal efficiency, which is not that surprising.  If I were to ever implement a storage system where air was compressed to store energy and expanded to put it back into use, I would look for some way of either capturing the heat generated by compression, or some other heat source to add back to the gas before it was expanded to increase the efficiency. 

If I get the chance, although it will probably be a couple of weeks, I will try to perform some rudimentary measure of the round trip efficiency.  I have about a half a kilowatt hour of energy storage in ultracapacitors within the range that my sw4048 inverter can handle, and a system where I compressed air with the excess in the day and recaptured it at night to keep the bank charged up longer would be of some utility to me, although I would have to obtain an effective muffler for the air motor and probably find a more efficient compressor as well to have any hope of making it practical.  The motor is 24V, and the test was at 12V, but since the induced voltage should be proportionate to the rate of change of the magnetic field, so long as the winding insulation can handle it, and the bearings as well, generating a higher voltage should be a matter of changing the gear ratio between the air motor and the generator.  Since it is 1750 at 24V and I usually have to spin them a bit faster to get the voltage back out of them, I am guessing that if it is spun up at about 3600 rpm it will probably be putting out about 48V, but that is just a guess at this point.

[thirteen]

Maybe you could put an air pump the runs off of solar power and get a large tank fill it and then you could let the air out to run your charging system. It would not last long but would make a good project to try. Free sun power. Just an idea to play with or toss

[richhagen]

Along those lines my inverter has relays built in which can be set to turn off and on at different voltages which could be used to drive a compressor to charge up an air tank when there is surplus energy which would be indicated by a higher voltage, and also to drive a solenoid on an air valve if I can get the contraption to charge at 48V by changing the gear ratio when the voltage falls below a certain point.  Thirteen it would be an interesting experiment.  First step will be to increase the charging voltage.

[thirteen]

About a year or so ago I was trying to figure out doing the same thing but using water in a 10,000 gallon storage tank.  I wanted to use a ram pump to lift the water up 38 ft or a solar powered pump. And when the tank was full a float would open up a valve and send the water out onto a turbine charging a battery bank. I also tried to figure out a solar air pump for a separate tank just for air. When the water got low enough it would open up another valve and let the compressed air into the water tank thus forcing the water out of the tank with air. But ideas and things and not enough time all change.

[richhagen]

Getting a compressor to fill the tank when there is excess power should be easy enough for me.  I dump excess to heat in the winter, so the configuration would be the same, just put the compressor in place of the electric heater.  the compressor will already have a pressure switch to cut it off when the tank is up to its high pressure and there is a secondary relief valve on it in case of over pressure.  I could then manually dump it at night and worry about a more elegant scheme as time allows.  I did pick up a couple of 15 or so gallon tanks from an old flame suppression unit which appear to be rated to 175psi and are still charged up, I'll just have to figure out the plumbing on them as they have a valve on the top with a gauge before leading off to 3/4 inch schedule 40 that I am not familiar with.  A wild estimate based on the discharge of the 20 gallon tank is that I would need at least a 100 gallons of storage at 125psi to have enough energy to do anything of much use with, but I will have to take some rudimentary measurements to know what it would be good for. 

Along those lines I still think the next step will be to measure the energy required to pressurize a known volume, and then the amount of energy I recover on the discharge.  Then I can calculate a rough value for the Watthours per gallon (or liter) of storage capacity as well as the efficiency, or conversely inefficiency, of such a scheme.  I expect the efficiency to be low, but at least I would know the starting point from which to make improvements.   For instance, if I can compress cooler gas and expand warmer gas I should be able to gain a bit of efficiency.  A multistage compressor should help too. 

[GreatBallofFire]

Along those lines I still think the next step will be to measure the energy required to pressurize a known volume, and then the amount of energy I recover on the discharge.  Then I can calculate a rough value for the Watthours per gallon (or liter) of storage capacity as well as the efficiency, or conversely inefficiency, of such a scheme.  I expect the efficiency to be low, but at least I would know the starting point from which to make improvements.   For instance, if I can compress cooler gas and expand warmer gas I should be able to gain a bit of efficiency.  A multistage compressor should help too.

Compressed Air, personally it is my favorite power medium. If you are using off the shelf equipment, the efficiency estimate is pretty straight forward. If you're compressing to over 100psi than the efficiency is probably 20% or less using most commercially available air compressors (excluding very large rotary screw designs). Next, the 4AM is a very common air motor with many different variations, so we'll make a few assumptions on the air motor. Assuming the 4AM is running at an optimum RPM and inlet pressure, you should average around 50% efficiency from stored energy to mechanical output. If the RPM and pressure is not optimized, then the efficiency could be much lower. Next up is your pulleys and electric motor, which we'll assume is roughly 90% and we'll also pretend that there are no other losses, but there most certainly are additional losses.

So, just for an example lets start with 1kw of initial energy input into the compressor. 1kw * .20 (compressor efficiency)= 200w * .50  (air motor efficiency) =100w *90 (electric motor efficiency) = 90watts/1kw = 9% conversion efficiency. Now, I just used estimates, but if you want more technical and accurate measurements for energy stored in the compressed air storage tank, I would more than happy to help.

Compressed air can be horribly inefficient, but it doesn't have to be. There are many improvements available, so feel free to ask!

-Mark

[bob g]

compress when it is as cool as possible, paint the tank flat black and mount it in the sun, use the compressed air when in full sun and hot as heck... might as well use the sun to avoid those losses associated with the heat of compression.

bob g

[richhagen]

Yes My initial rough estimate when I went back and did some extremely rough measurements and estimates, which is in line with Greatballoffire's estimate.  It is too low to be of any practical use beyond a demonstration at present.  I did not realize the compressor was that bad at efficiency, but in order for there to be any practical use that will have to be improved upon a bit.  I could probably live with 25% and find a use, but that is at least 2.5 times the starting point.  Along with Bob's thinking I was looking at putting heat back into it before expanding it.  I was thinking that if I could figure out a method to get the heat generated during compression into an insulated water tank, and then run the air back through that on the way to the air motor it would help out the efficiency quite a bit.  I was also thinking that supplementing the heat into that tank with solar power would also be of help.  I was thinking that the energy storage capacity of the tanks would be greater if I could keep the compressed air cold while in storage, and heat it on the way to the air motor.  If I heat the air tanks in the sun, then the mass of air stored at a given pressure would be less, although the energy through the motor would be the same.  It would work as an efficiency improvement, but at the expense of needing a larger storage vessel for a given stored energy requirement.  My available space for a working system is not that great so I am kind of leaning away from that simpler solution in favor of heating a water tank as I think the portion of the energy storage in a hot water tank will be more compact than in the hot air tank, although I have not crunched the numbers on it yet.   For that reason I browsed over to build it solar's website to look over the various hot water heating systems to see if there was something reasonably simple and easy that I could implement to heat a water tank.   Before I use up what scarce time I have to build something though, I would be interested in hearing what other Ideas you guys have.  I still plan to do a better measurement of the electrical energy into the system and the electrical energy out to calculate a more accurate empirical calculation of the efficiency and will post that once it is completed. 

I have also recently downloaded Gast's air motor implementation guide and read through the concepts and browsed the torque curves for the motor.  In actuality, I am thinking that these motors would be great matches for a direct drive axial flux alternator designed to have cut in at the motors maximum torque for the low end of the operating pressure.   The torque tapers of slowly and I am thinking it would reach equilibrium while the motor is still operating near its most efficient for the range of pressures it would see.   The exhaust gases from the motor could be vented across the alternator to assist in heat removal as well. 

[definitionofis]

I saw a link last week to an article about water injection improving compression storage efficiency to 70%??.  I can't find it. Does that idea make any sense?

[GreatBallofFire]

Yes My initial rough estimate when I went back and did some extremely rough measurements and estimates, which is in line with Greatballoffire's estimate.  It is too low to be of any practical use beyond a demonstration at present.  I did not realize the compressor was that bad at efficiency, but in order for there to be any practical use that will have to be improved upon a bit.  I could probably live with 25% and find a use, but that is at least 2.5 times the starting point.  Along with Bob's thinking I was looking at putting heat back into it before expanding it.  I was thinking that if I could figure out a method to get the heat generated during compression into an insulated water tank, and then run the air back through that on the way to the air motor it would help out the efficiency quite a bit.  I was also thinking that supplementing the heat into that tank with solar power would also be of help.  I was thinking that the energy storage capacity of the tanks would be greater if I could keep the compressed air cold while in storage, and heat it on the way to the air motor.  If I heat the air tanks in the sun, then the mass of air stored at a given pressure would be less, although the energy through the motor would be the same.  It would work as an efficiency improvement, but at the expense of needing a larger storage vessel for a given stored energy requirement.  My available space for a working system is not that great so I am kind of leaning away from that simpler solution in favor of heating a water tank as I think the portion of the energy storage in a hot water tank will be more compact than in the hot air tank, although I have not crunched the numbers on it yet.   For that reason I browsed over to build it solar's website to look over the various hot water heating systems to see if there was something reasonably simple and easy that I could implement to heat a water tank.   Before I use up what scarce time I have to build something though, I would be interested in hearing what other Ideas you guys have.  I still plan to do a better measurement of the electrical energy into the system and the electrical energy out to calculate a more accurate empirical calculation of the efficiency and will post that once it is completed. 

You're on the right track with supplementing the compressed air with solar thermal. The design that I advocate uses stored solar thermal energy in the form of compressed air with real time solar thermal energy to increase the volume before expansion. The problem, as you already pointed out, is the amount of space required to store a decent amount of energy as compressed air. You're idea about the hot water tank is also a good one, but the primary issue is the low efficiency of the compressor. Capturing waste heat is great, but not having waste heat is even better. Also, on the air motor, you're better off with a higher peak output air motor than what you need and then running it on a lower pressure level to match the load. You have already pointed out the great low starting torque advantage of air motors and when combined with some form of gearing the efficiency of the air motor can be decent. Not as many people interested in compressed air these days, but I'm hoping to change that a little bit.

I saw a link last week to an article about water injection improving compression storage efficiency to 70%??.  I can't find it. Does that idea make any sense?

Yes, in the right application water injection can be great. In the wrong application it can destroy equipment, but it's definitely capable of increasing the total efficiency of the air compression process.

-Mark

[dnix71]

Adding water to increase efficiency makes sense if you consider that when you compress air, water comes out. That's why you have a drain on the tank. You spent energy compressing the air/water vapor mix enough to force a phase change and then dumped the water. You are really doing a fractional distillation of air, and the water vapor is what drops out first.

That's where a lot of waste heat comes from if you are compressing humid air.

Dry air and an inline oiler are standard equipment unless you want to ruin your nice pnuematic tools.

[richhagen]

Reading through these, I don't know much about injecting water, as I am pretty sure the common air motors would not tolerate liquid water mixed in with the expanding air vary well.  The guide from Gast lists a few problems caused by having water in the air line on those motors.   I guess that if you could get the volume of vapor to increase at atmospheric pressure you could get more power, but I am not sure how practical that would be at this stage for my little experiment.  Basically I don't know how I could implement such a scheme.  I have acquired a water separator, filter and oiler for  the air motor, off the shelf equipment, but I have not plumbed them up yet, I've just ran it for short periods and manually added oil to the air motor to this point.

The compressor efficiency is a big issue as that is where the largest energy losses are occurring, but I don't see any off the shelf equipment that appears to be optimized for efficiency for either isothermal or adiabatic compression.  Although it appears that air 'can' be compressed more efficiently from an energy standpoint, there appears to be little done on other than compressors sized for whole factories to bring this about aside from a few models with small inter-coolers between the cylinders on a few dual stage piston compressors, but even on those the efficiency still appears to be rather low. 

[GreatBallofFire]

Reading through these, I don't know much about injecting water, as I am pretty sure the common air motors would not tolerate liquid water mixed in with the expanding air vary well.  The guide from Gast lists a few problems caused by having water in the air line on those motors.   I guess that if you could get the volume of vapor to increase at atmospheric pressure you could get more power, but I am not sure how practical that would be at this stage for my little experiment.  Basically I don't know how I could implement such a scheme.  I have acquired a water separator, filter and oiler for  the air motor, off the shelf equipment, but I have not plumbed them up yet, I've just ran it for short periods and manually added oil to the air motor to this point.

The compressor efficiency is a big issue as that is where the largest energy losses are occurring, but I don't see any off the shelf equipment that appears to be optimized for efficiency for either isothermal or adiabatic compression.  Although it appears that air 'can' be compressed more efficiently from an energy standpoint, there appears to be little done on other than compressors sized for whole factories to bring this about aside from a few models with small inter-coolers between the cylinders on a few dual stage piston compressors, but even on those the efficiency still appears to be rather low. 

The water has to be filtered out before the air motor or you will have problems. The water injection functions similarly to the water injection on an internal combustion engine. Just the right amount of water sprayed in a specific mist is good for performance, but the wrong amount of water or the wrong droplet size damages the engine. Same scenario for water injection for air compressors, which is not recommended without computer controlled software for the injection system and an air compressor that is designed for it in the first place.

I don't want to spam this forum, but if you're interested in isothermal compression just contact me and I'll help out with what I can. As you have correctly stated, all of the efficiency increase has been focused on large 100% duty cycle air compressors that are rather expensive.

-Mark

[joestue]

i don't know about your 24v 1 hp motor, but the 90 and 180v motors i have all consume at least 50 watts idle.

figure another 100 watts of conduction losses and you're at 746/900 which is 82% efficient.
a 24 v motor is going to have at least an order of magnitude more brush loss...

[GreatBallofFire]

i don't know about your 24v 1 hp motor, but the 90 and 180v motors i have all consume at least 50 watts idle.

figure another 100 watts of conduction losses and you're at 746/900 which is 82% efficient.
a 24 v motor is going to have at least an order of magnitude more brush loss...

Ya, I was being generous with the 90% efficiency for the motor and pulleys, but that's why I said there are also other losses. Just trying to keep it simple and with even numbers that are easy to quickly calculate. The PM efficiency is the least of the issues. The primary problem is the total compressor efficiency and the next major problem is the physical space required for the air tank relative to say a 12v 100ah battery.

-Mark

[theshadownose]

If this is too far off topic, please delete or move. 

I understand that the efficiency is low to covert back to electricity.   What if you convert it to something else?   If you compress the air into the tank (in the shade) the tank heats.  once that excess heat is lost,  when you bleed out the air, bot the tank and the airstream are COLD.  Could this be used as a primitive A/C unit?

Or if you are in dry climate, force the air through a swamp cooler pad for even more cooling?

[GreatBallofFire]

If this is too far off topic, please delete or move. 

I understand that the efficiency is low to covert back to electricity.   What if you convert it to something else?   If you compress the air into the tank (in the shade) the tank heats.  once that excess heat is lost,  when you bleed out the air, bot the tank and the airstream are COLD.  Could this be used as a primitive A/C unit?

Or if you are in dry climate, force the air through a swamp cooler pad for even more cooling?

It's not that far off topic. It really depends what you are trying to accomplish and what you're comparing it to. General cooling and A/C are great byproducts of compressed air that has been used for work, but pretty lousy if it's the main goal. Most people don't realize it, but most modern A/C units are pretty good heat pumps that move a lot of heat relative to the electricity input.

If your primary goal is cooling there are a lot better ways than compressed air. However, if you are expanding the compressed air for work and then using the now cooler air as a byproduct that is a completely different scenario.

-Mark

[bob golding]

an idea i was told about that someone local has made is to use empty 2 litre cola bottles surrounded by expanded foam insulation as a fairly safe lightweight air tank.
i havent tried it myself yet, as i don't really have a use for compressed air, but he says the bottles will hold an amazingly high pressure. around 150 PSi. just an idea.
 the foam is squirted in around the bottles which are filled with water with the caps on so they don't collapse as the foam expands.
makes a nice lightweight energy store.

[GreatBallofFire]

an idea i was told about that someone local has made is to use empty 2 litre cola bottles surrounded by expanded foam insulation as a fairly safe lightweight air tank.
i havent tried it myself yet, as i don't really have a use for compressed air, but he says the bottles will hold an amazingly high pressure. around 150 PSi. just an idea.
 the foam is squirted in around the bottles which are filled with water with the caps on so they don't collapse as the foam expands.
makes a nice lightweight energy store.

Wow, I wouldn't recommend that to someone that I didn't like let alone someone that I did. It's definitely true that plastic bottles will hold some pressure and probably a little more if they are surrounded with foam like you're talking about, but 150 psi in plastic cola bottles is done right nuts. There is a reason air tanks are made from steel or carbon fiber.

-Mark

[bob golding]

i wasn't suggesting you DO take them to 150 PSI, just that they will withstand 150 PSI. he is using them at around 15 PSI.giving a safe overload of 10 times the pressure. this is plenty for doing things like paint spraying.

[GreatBallofFire]

i wasn't suggesting you DO take them to 150 PSI, just that they will withstand 150 PSI. he is using them at around 15 PSI.giving a safe overload of 10 times the pressure. this is plenty for doing things like paint spraying.

15psi is completely different than 150psi, I just didn't want people to think they could go out, collect some empty soda bottles, and then could put 150psi in them as long as they are surrounded by foam. Any medium under pressure has the potential to be dangerous, including compressed air.

-Mark

[bob golding]

fair point. i am assuming, maybe wrongly that anyone playing around with compressed gases would have enough sense to understand that there is a lot of stored energy in compressed air and  be careful.
in the case of the soda bottles the 150 psi was established using water, the correct way to test pressure vessels.

[prasadbodas2000]

The experiment described by richhagen was interesting, but yes the losses due to efficiency limits associated with air/gas compression systems can be substantial.

On the other hand a pumped storage water system (pelton turbine - 90% eff with centrifugal pump - 45 - 50% eff or reciprocating piston pump 85+% eff) might be a better combination. Needs a pair of water tanks and a height difference which generally would be provided by the height of the house/building.

The idea is if possible to avoid the battery at all :-)

[GreatBallofFire]

On the other hand a pumped storage water system (pelton turbine - 90% eff with centrifugal pump - 45 - 50% eff or reciprocating piston pump 85+% eff) might be a better combination. Needs a pair of water tanks and a height difference which generally would be provided by the height of the house/building.

The idea is if possible to avoid the battery at all :-)

You're definitely right that pumped storage can be more efficient than compressed air, that's why there is so much more utility pumped storage than utility compressed air. I not a big fan of batteries at all, but if you're only storing a small amount of energy I would take $100 battery over many of the other options. You're probably not going to get a decent turbine and pump for less than 100 bucks.

-Mark

[Bruce S]

Actually you can think of either the compressed air storage or water as the battery.
Both are used to "store" for later usage, therefore they take the place of the traditional battery.
In the distant past before batteries were not as common place, water and mechanical (clockworks) were the battery of their time.
Water is 8 times more dense as air, which is why a great number of reservoir based gen facilities pump at low demand instead of compressing air.
In colder climates there would need to be in place a way to keep the water from freezing or go with an alcohol additive.

Cheers;
Bruce 

[GreatBallofFire]

Actually you can think of either the compressed air storage or water as the battery.
Both are used to "store" for later usage, therefore they take the place of the traditional battery.
In the distant past before batteries were not as common place, water and mechanical (clockworks) were the battery of their time.

Well of course anything that "stores" energy is considered storage. For a small residential system, Lead Acid is still one of the easiest ways to store a limited amount of energy, 1 or 2 kW. I don't even like battery based systems, but that is still currently the reality.

Water is 8 times more dense as air, which is why a great number of reservoir based gen facilities pump at low demand instead of compressing air.

Compressed air storage on the utility scale actually has a COP of over 1, so it can be more efficient than pumped storage when used with combustion turbines. But, there are pretty strict geographic requirements for utility size compressed air storage, which is why it is not more common. Hydro facilities use pumped storage since it cost $0.03 a kW to pump it and the utility sells it later for $0.11, not too hard to figure out why there is so much pumped storage in the grid system.

-Mark

[wlcoldiron]

Hi
I use compressed air to pump water from a well. I use a tapered main bearing compressor that is direct drive from the wind. It sets on a tower and I use a 1,000 gal propane tank for storage. In the winter the air pressure reaches above 150#.  I service the compressor bi-annualy. It works well. I plan to add compressors until I get enough air to pump around the clock.  Weldon

[GreatBallofFire]

Hi
I use compressed air to pump water from a well. I use a tapered main bearing compressor that is direct drive from the wind. It sets on a tower and I use a 1,000 gal propane tank for storage. In the winter the air pressure reaches above 150#.  I service the compressor bi-annualy. It works well. I plan to add compressors until I get enough air to pump around the clock.  Weldon

Hey, thanks for sharing! I assume since you are planning to add more compressors that you currently have more wind available than storage? Are you going to increase the pressure since you are using a propane tank which probably has a pretty high maximum pressure rating. What service is usually required for the compressor?

1000 gallon tank at 150psi is some serious energy storage for compressed air, over 10kW assuming worst case adiabatic expansion. Unfortunately, the kWh rating is probably pretty low, around 0.18kWh. Roughly, how much water can you pump and to what height?

-Mark

[wlcoldiron]

Hi
The compressor maintainence is to change the oil and check for loose bolts. I could increase pressure because the tank is rated for 200# working pressure. I will add compressors and tanks  for more storage. I My lift is about 55' and the well is about 2000' deep. The pump is homemade and it has a 1"discharge. With 10 cfm pump and 25# air pressure it pumps about 6 gpm.  The reaso to add more compressors is to pump more water to keep water in the stock tanks. I have about 2500 gal. of storage available. I have a seperate storage container for air to operate my shop air needs. It has worked well for a long time. I have no well pump maintainence at all and no electricity bill to pump water or shop air.  Weldon

[GreatBallofFire]

Hi
The compressor maintainence is to change the oil and check for loose bolts. I could increase pressure because the tank is rated for 200# working pressure. I will add compressors and tanks  for more storage. I My lift is about 55' and the well is about 2000' deep. The pump is homemade and it has a 1"discharge. With 10 cfm pump and 25# air pressure it pumps about 6 gpm.  The reaso to add more compressors is to pump more water to keep water in the stock tanks. I have about 2500 gal. of storage available. I have a seperate storage container for air to operate my shop air needs. It has worked well for a long time. I have no well pump maintainence at all and no electricity bill to pump water or shop air.  Weldon

Weldon, thanks for sharing your information, it can be very helpful. A quick guestimation puts your pump efficiency probably some where around 15% which ain't too bad. Since you have so much water storage available, can you pump the water directly from the wind turbine and then store the additional energy in the air tanks? I don't know your set up, but I was just curious. It's great that your compressor just needs a little oil and a quick check of the bolts once or twice a year.

-Mark

[wlcoldiron]

Hi
I can pump the well directly from the wind turbine but I don't. I pump the air into the tank and regulate both the flow rate and the pressure so the volume and pressure are relatively constant. I don't use the air that is exhausted with the water from the well. If I used the exhaust air the water pump would be less effective. I don't pay too much attention to effeciency percentages because I just look at the amount of money per month I save. Besides the fact it is environmently  friendly and simple. Weldon

[GreatBallofFire]

Hi
I can pump the well directly from the wind turbine but I don't. I pump the air into the tank and regulate both the flow rate and the pressure so the volume and pressure are relatively constant. I don't use the air that is exhausted with the water from the well. If I used the exhaust air the water pump would be less effective. I don't pay too much attention to effeciency percentages because I just look at the amount of money per month I save. Besides the fact it is environmently  friendly and simple. Weldon

Very cool Weldon, thanks for sharing info about your setup with us.

-Mark