From what little I understand of air use in industry, it is considered very inefficient and seems it is only used when absolutely needed like when the power to weight ratio of a tool is a determining factor. From this and my general observations of air and how it was used in the numerous plants I have visited, my guess is that there is not a large enough demand to support the type of infrastructure you are suggesting except maybe in a particular industrial park where most residents had a very large need for it. Aside from that, I have the sense that, although the problems (leaks, condensation...) could be addressed on a larger scale in a similar fashion as they are on a smaller scale, it would still incur significant maintenance issues. Also, if there were high pressure zones (in an attempt to supply more with less material in piping) that there would also be significant safety issues. Not to rain on your parade, but seems like it is a no brainer and if someone had seen it as a practical way to make money (which it must do to be feasible) they would have already done it. But that's just my opinion, I could be wrong.

Inefficient or not, compressed air is a useful source of controllable force. Many on-off valves and flow modulating valves use compressed air as a power source as, by changing the pressure in a variety of ways, it can be used very easily to adjust process conditions to make consistently the materials mankind uses today. Incidentally, it is also relatively easy to fault-find on pneumatic installations; given appropriate care as to where jets are directed (i.e. not towards the skin, ears or eyes), compressed air is easy to spot for presence or absence: it either hisses or bubbles. Electricity just can't do that.

Electrical machines are more complex than a cylinder, a pipe, a piston and a spring. Large sections of London's Underground railway network have devices that operate using compressed air as a driving force: point actuators and train stop trips are among the examples. It enables small devices with minimal cabling to be used for control and detection, and the pipe network itself is an appropriate energy storage reservoir that provides the grunt needed to shift some of these items, which can be quite stiff and heavy.

Horses for courses, as in all engineering fields.

Further, compressed air machinery can go where electrical machinery cannot. Oil refineries spring to mind...

I whole-heartedly agree that there are many applications where air power is hands down the best solution. I just don't see it adequately widely enough applied in order to justify its institution as a utility. Since it would in all likelihood be produced by using electricity even if it were centrally produced and electricity already is widely distributed, the prospect of installing thousands of miles of air piping seems at the very least redundant. I just don't see an advantage to generating it locally. I've never heard any facility operator lament "Gee, I wish I could buy compressed air instead of having to produce it on site."

As my wife and I make preparations to move to the country and an "off the grid" lifestyle, we have been trying to decide what energy sources we will utilize in our home. I have long thought that a wind turbine driven air compressor would be a very fine use of the wind's inconsistent power supply. A air compressor driven by a turbine would not be hindered by fickle winds, it would be able to utilize light breezes, something an electric generator is incapable of. The storage system would be a simple pair of receivers, one high pressure and one low pressure. The first receiver would take in air compressed to whatever pressure the turbine/compressor would be capable of delivering, the second would only take in air from the first receiver after it reached a predetermined high pressure (80 psi) or so. This setup would gather energy in light breezes and high winds, it would be cheaper to store compressed air energy than it would to store the equivalent amount of electrical energy, and excess air pressure (if any) could be used to create electricity or heat. There are Amish farmers near where I live that use compressed air in a manner similar to the way we use electricity. They have "hacked" a large range of appliances to utilize air motors and cylinders instead of electric motors. They have wall mounted valves that are mounted like electric switches. I know one Amish gentlemen that runs a small grist mill with a steam engine modified to use compressed air.

If large turbines similar in size to the ones being put up by companies like Horizon wind energy and GE were used to drive efficient compressors instead of electrical generators they could provide the compressed air for large industrial complexes, vastly reducing electrical demands for many manufacturing facilities. With lowered electrical consumption it would be easier for wind turbine generators to provide those same manufacturing facilities with their electricity requirements.

"in size to the ones being put up by companies like Horizon wind energy and GE were used to drive efficient compressors instead of electrical generators they could provide the compressed air for large industrial complexes, vastly reducing electrical demands for many manufacturing facilities" The problem is, air is not as efficient. It takes more energy to get the same amount of work at the end of the line than if you use electricity. I'm not saying there aren't situations it might be useful, but it simply isn't as efficient and you will use more energy to do the same job.

The point is not that compressed air is more efficient than electricity. Factories use compressed air, the need isn't going away. Electricity is typically generated through rotary motion, that electricity is then converted back to rotary motion to compress air. By using wind, or even a steam turbine to compress air you eliminate the conversion. This would reduce the electrical load requirements of facilities tied to the renewably or traditionally generated compressed air grid. My factory uses more electricity to compress air than any other process. We have two 200 H.P. compressors, sized right, properly maintained, very, very few leaks. We would cut our on site electricity use by 38% by getting our air from a compressed air grid.

Also electricity cannot yet be stored on a large scale economically. Compressed air can.

Madscientist, your factory uses serious air at 400 HP. Many haven't been exposed to the amount of compressed air that is used by the factories that supply almost everything we touch or see in our daily life. It is more inconceivable to think of our world without compressed air than compressed air from a utility source. If the factories near you use anywhere near the compressed air you do the potential for a utility source in your area is not that far fetched. You are using about $5000 a month for electricity to compress air at 2/3 of your 1600 SCFM capacity. Add to that maintenance and repairs, the cost of money invested in capital equipment that will eventually wear out, floor space of a compressor room. My guess is that you would jump at a chance to connect to a 6" pipe flange that could supply much more clean, dry air (CDA) @ 100 psig than you use now measured by flowmeter at a rate of 1/3 cent per standard cubic foot (SCF) or 1 1/2 million SCF per month for approximately $5,000.

You pay for leaks and wasted air within your factory. The utility provider is responsible for the distribution system.

The incite from your first hand knowledge of compressed air and familiarity with it, warts and all, is appreciated.

You are ahead of the curve on the windmill. Generating electricity, transporting it to sub-stations and finally distribution to your factory to power electric motors that compress air is inefficient. Direct drive with wind, water, waves, even automobiles passing over pads in the freeway to compress air as they drive along would be more efficient for compression.

With the order of magnitude a utility generating compressed air could use the heat and water as viable byproducts.

These are not ideas whose time has past. They may be ideas whose time has not quite come. The greater density of our growing population makes finding better ways a must. As a boy when we had chicken dinner I was sent to catch one in the yard. Now they come without feathers or innards in plastic packages or even hot off the rotisserie at the grocery store. Most would criticise and condemn a Model A Ford if it were offered today. We have come a long way with automobiles from the Model A in 75 years. Compressed air equipment and practices are still much as they were when compressed air replaced steam in the same time span. Someone said "Don't ask what if it doesn't work, ask what if it does."

Mr Kreher:

do you agree that if compressed air facilitie is a new good option,that the compressor

that actuates the pistons must be directly by mechanical :wind/water-fall/and electri

city only at the amount of not consumed and to be lost ,to rotate electrical motors to

store air ,despair of low efficiency?"Continuous offer of electrical energy would be consumed by motors of compressors to compensate for periods of low consume"

Mckengbr, we in Portland, Oregon (and sister city Vancouver, WA) live beside the mighty Columbia river rolling down to the sea. While it is much damned for hydro-electric power I doubt that it produces compressed air at any point in it,s thousand mile run to the sea. I guess you could call a river a gradual water fall. In the Columbia Gorge wind mill farms are growing faster than trees to generate electrical energy. We have coal fired electrical generation plants and another nuclear plant is planned.

Madscientist echoed a comment I have heard before, that air compressors are the greatest consumer of electrical energy in many manufacturing plants.

I won't repeat undocumented efficiency claims for the electric motor to compressed air path but even in the middle ground it is not good.

I once marveled at the size of the boats that traveled Lake Superior with ore en-route to steel smelters farther east. Then one day I flew from Detroit to Cleveland and looked down from the plane to see tiny little boats at very slow speeds carrying their goods. The thought that trucks and trains hauled the ore to the lake shore to fill those tiny little vessels, waiting for them to meander to the next port, then unloaded again unto trucks or trains seemed so terribly inefficient that I was amazed. What we see depends on where we sit, on the lake shore or high above looking down.

I could guess that 20% of the electricity generated runs industrial compressors and half of that is wasted. Standing beside two 200 Horse Power compressors is impressive. Looking down from a plane from above or a Martian looking and wondering what the heck we are doing makes me think we are not giving this compressed air thing our best shot. Sons and daughters of those who built the Panama canal, linked a Continent with rail roads, highways, electricity and telephones damned the raging rivers can surely surmount a few details required to add compressed air to an industrial complex as a utility. It is common sense waiting to happen.

Tom Kreher wrote: The thought that trucks and trains hauled the ore to the lake shore to fill those tiny little vessels, waiting for them to meander to the next port, then unloaded again unto trucks or trains seemed so terribly inefficient that I was amazed.

Comment: And what you cannot see from an air plane is that the ship moves thousands of tons of ore at a much greater efficiency and lower cost per ton mile than any railroad or truck. Likewise your condemnation of wind generators not being able to store electricity only applies to AC. DC electricity can be stored.

I'm intrigued by the report of Amish farmers using compressed air to drive some appliances. Presumably this is low pressure air. Sometimes we tend to blind ourselves with science. this discussion revolves around high pressure air being delivered long distances in expensive pipelines. The construction of this distribution network is considerable. Is it really necessary to use such high pressure?

The painting industry has recently undergone a major revolution in switching to high volume low pressure HVLP painting instead of the traditional higher pressure lower volume paint guns using variations of bernoulli's principle.

Have a look at the vacuum delivery system used in majnor stores for the cashiers to send cash to a remote teller and money vault. These vacuum tubes deliver a canister many feet, sometimes hundreds of feet using very low pressure ( or rather vacuum on the opposite side of the piston.

A scheme to convert wind generators to high pressure compressors will run into problems that will defeat the expected efficiencies. However on a local level it may work if we concurrently develop a system of doing the same work using lower pressures.

Elnav

The turbine driven compressors I plan to build will probably compress air to about 80psi. The idea is to size the compressor to the lowest readily available wind speed in the region I plan to erect the turbine in. The wind speed at 60 -80 ft high is at least 10 mph, and can reach as high as 60+ mph in storms. I plan on building my turbines using available 36" carbon fiber rotors, they have very low inertia, and can withstand high wind speeds. The compressor I plan on building will utilize pistons to compress the air, I will probably build it as a dual stage compressor. It will have a small enough displacement that it can be started in light breezes. I got the idea when I was pumping up a tire using a small battery powered compressor. My battery was nearly dead, yet the compressor was able to generate pressure until the motor finally stalled. This made me think that a small compressor coupled to a turbine would be well matched to take advantage of light breezes, and it would still work in high wind speeds, it would just compress a greater volume of air, but at the same pressure. If the compressor where mounted on a 60 ft tower, it would be fairly easy to incorporate a heat exchange in the tower that would cool the air to ambient temperature before it goes through the desiccant dryer. I will use two receivers, a smaller stainless receiver with a drain, and a larger all steel tank (2600 gallons or so) to store the bulk of the air. It is possible to store as much energy as my family would use throughout the course of the day in such a receiver. A compressed air powered engine can power a generator, and many devices can be driven with air instead of electricity. I consider all of the advantages of storing energy using compressed air instead of lead acid batteries. The life span of an air tank is much greater than batteries, no hazardous chemicals. The energy density potential for a steel storage tank and lead-acid batteries are similar, but a tank will last for decades instead of years. I have decided to power my off the grid homestead with air as the primary, electricity from PV and wind as secondary, fossil fuels as backup.

If windmills can drive compressors, the efficiency is not so important, so the idea of pumping up high pressure vessels to store air at random and erratic pressures, then to supply it at a controlled rate, has some merit - albeit localised - but on a small scale where a local group shares the cost of a suitable windmill might work. I will leave the sums to someone else.

The idea of a compressed air national grid is a bit to soon I feel. The infra-structure is mind-boggling. Having said that I heard of a system (40 years ago) somewhere in France, Paris I think, where there was huge communal compressors system -100,000 cfm I gather. No details and no proof other than gossip.

I don't think the idea is to have a nationalized compressed air grid, interlinked city to city. I think the idea is localized grids, interconnecting closely spaced companies on an intermediate scale. For example, my factory is located in very close proximity to several other factories. Compressed air is cheaper to produce as the scale of production increases, it costs more per CF.M. to produce 10 C.F.M. of 80 P.S.I. air that has been treated by a dryer and filtered to 1 micron or so than it does to produce 3000 C.F.M. This a terrific example of the economics of scale. The other advantages to such a system is that maintenance of a compressor would essentially be outsourced. This would eliminate any service needs of a compressor or dryer in an individual facility. Our compressors are serviced on weekends when the facility is not operating. We pay our maintenance people overtime to perform this work. This cost could be eliminated. If the planners of new industrial parks would incorporate a compressed air generation facility into the layouts of such parks at the onset implementation would not be very difficult. Factories would be lees costly to startup because there would be no upfront cost of compressors, dryers, and receivers.

The bottom line is compressed air would cost less to the end user if it were generated off-site and distributed to several facilities.

I suppose there is little difference in what you suggest in terms of distribution (where each consumer pays for compressed air on a user basis from a communal system), than a single large company having the same size plant supplying the same amount of air to numerous outlets in the same area. The difference basically boils down to the means of measuring usage.

Madscientist wrote: The other advantages to such a system is that maintenance of a compressor would essentially be outsourced. < snip> We pay our maintenance people overtime to perform this work. This cost could be eliminated.

REPLY

What a wonderful NIMBY tool! So some other poor slob has to ruin his week-end doing maintenance but because it's now outsourced he only gets the regular rate as a contractor.

News flash. Manufacturing generally is being outsourced. Why not just eliminate the entire cost of setting up a factory completely. Then you wouldn't have to worry about providing compressed air in any form. Save a whole lot of bother and expense.

I'm not looking to outsource manufacturing. Our maintenance people work long hours, and they are not especially fond of working Saturdays and Sundays, especially to do PMs on compressors. Sorry you guys can't spend time with your families this weekend, I need you to clean the heat exchangers on the compressors and change the oil. They appreciate having their weekends free as much as I do. I suppose if we wanted to bring all of our services in house we could buy a natural gas turbine to generate electricity. We could capture rain water run-off from our roof and setup a treatment plant here, and hire a couple of environmental techs to monitor the water treatment process. We could also buy an electric furnace to melt down our scrap. We could then close our doors because our massive overhead would prevent us from being competitive in our marketplace. We are in business to make money for our shareholders. Most of our employees own sizable amounts of company stock. When we find means to reduce operating expenses, we create opportunities to make greater profits. This increases employee profit sharing, makes us a stronger company, and provides our employees with greater stability. It also yields more money for our shareholders, our primary mission objective. The outsourcing you are referring to is bad, sending US jobs overseas. The kind I'm referring to would essentially create more jobs in our community and strengthen our local manufacturing base.

It was indeed in Paris.

The network was used to drive several power systems in the subway.

The clocks in several subway station still run on air. Now delivered by small units in the stations.

Compressed air is a very old way of distributing power, not really economical. The tubing is far much more expensive and dangerous than electricity. The fact that the tubing works as a capacitor makes it even worse.

Try to run a computer or make light with compressed air.

Did you ever see a compressed air stove?

The amish do use air as that is not forbidden by their religion.

Imagine a power down, it will take hours to get the system back on track.

Gwen,

With all due respect to the adherents of any particular religion, I do get a kick out of how they (to me) arbitrarily seem to pick some date, before which, the technology is acceptable, but after which it is not, or is sinful.

They never seem to go so far back as before the wheel, or fire, but some other much more recent time.

I have often thought that someone will be "inspired" to start a religion where the cutoff point was say 1946. You could have a car, provided it was a 1946 or earlier model, TV would be fine, but would have to use tubes and be black and white only, and so on.

But I digress.

On the subject of centralized compressed air supply, I think its potential is very limited. Not too mention that the typical smaller industrial compressors offer much room for improvement in efficiency, and that might be a better avenue to pursue.

Greg

I love it. Just think of the possibilities. We could have one for each year. They could split into factions and there could be wars over which technologies were the true technologies for any given time. We are the '57 Chevyists, death to the '57 Fordists and so on ad infinum, Gee, sounds vaguely familiar.

I see a huge potential market for compressed air to decontaminate the ocean bottom under the large floating frames for salmon cultivation in southern Chile.

In that zone of the world there are hundreds of fiords, in a landscape quite similar to Norway. The salmon cultivator companies there are having problems with the thousands of tons of detritus deposited at sea bottom.

I guess that with a network of strong plastic of fiber air ducts of some 12" diameter, fixed at the bottom, it would be possible to produce air bubble curtains of several hundred kilometers long that would allow recovering the original state of seawaters inside and around all fiords.

The situation is even worse in several lakes of southern Chile that urge for a major decontamination operation not only under the floating frames but all over the bottom. The problem is of high magnitude, at the point that the compressor plants should be the size of electrical plants installed near the cost. I guess that the air rays should not point to the bottom directly, because a giant cloud of detritus similar to an atomic cloud would be elevated immediately. The pistons should point upwards along the ducts avoiding direct hit to the bottom, the important thing is to increase the oxygen dissolved in deep waters and let algae and microbes do the rest.

In the extreme south of Chile the winds reach easily above 100 KM/H at all hours and year round, so in those fiords the conditions are ideal to design air concentration plants 100% based in windmills. These plants can also be built in western coast of Chiloe Island, in the cost facing the Pacific Ocean. All southern island costs facing de Pacific Ocean receive extremely strong winds that would allow keeping air bubble curtains alive almost 99.999 % of the year at top power.

I can make contacts with salmon companies for if they are interested in cleaning the ocean bottom with air bubble curtains. They would immediately ask me for prices. I am an electronic engineer with little idea in pneumatics, but some circuit simulator software programs allow understanding some about, however as "Kirchofs laws" do no apply to compressible fluids, these "pneumatic circuits" are more equivalent to non lumped circuits, so special simulation software programs should be used to design the networks, also considering that the deepness of the ocean varies significantly from one fiord to other. Detailed maps on sea bottoms are available for that entire zone.

Well this idea of hundred kilometer long ducts producing long air curtains should have also application for decontamination of port bays or along contaminated coast, as it is the case of Bengala Bay, India, or along the Ganges River India, or so many contaminated rivers and major ports along China and Japan coasts. The benefits would be very important to decontaminate the costs in the whole world.

Your company wills became the "Microsoft" of pneumatics; you have the golden key.

Jaime Soto Figueroa

Chile

http://www.matharts.cl/

This is a good idea but it is almost impossible to construct. Find out how deep those fiords are. Calculate the pressure at various depth and thats the air pressure +you have to have in the pipe to blow bubbles. I think you would need roughly 6400 psi if the pipe is 100 ft down.

100 ft is 30.48m

In seawater (3% salt) the overpressure will be 3.1 bar, or 45 PSI

The biggest problem will be: keeping the 12" pipes at the seabottom.

The basic idea is not really very new, I also feel that its time has passed us by already, London had such a system based on water pressure at around 700 lb sq in started around 1870, that ran until 1977.

Air would be far more dangerous I feel personally, what would happen if a building caught fire, the air might leak and blow the fire up to enormous temperatures, whereas water would just put it out.....I am not saying that high pressure water is not dangerous in its own way, just a lot less!

They actually achieved 5 MegaWatts of water power in the 19th Century, amazing.

Search on on the internet using:-"london hydraulic power company"

Also check out these links for more info, photographs and maps:-

http://www.subbrit.org.uk/sb-sites/sites/h/hydraulic_power_in_london/index.shtml

http://en.wikipedia.org/wiki/London_Hydraulic_Power_Company

http://www.answers.com/topic/london-hydraulic-power-company

Storing compressed air would be perhaps still better at the energy generation:

>> imagine wind energy that is converted to electrical by "wind farms".As mechanical

energy appears it must be electrically instantaneously consumed,and statistics can

show the demand according to day of week,season and hour.So,at moments of low

consume the potentiality of energy is not "fully consumed".But if some wind-ener

gy machines in the farm were to take mechanical energy of wind to move a compres

sor in subtitution to motor,then energy would be saved in really enormous containers,

but to be served to system by this air moving a generator in the moments of large

demand,as batteries would seem more direct ,but much more expensive and of consi

derabaly lower duration.

For energy storage compressed air is a poor solution.

You never recover the thermal losses encountered in compression.

Lifting water and allowing it to return through a turbine/generator is far better, and is the method used by some utility systems.

As repeatedly stated, compressed air is an industrial reality, and the point was that "communal" generation and distribution makes sense in an industrial park setting, from the standpoint of efficiency. A park created with this infrastructure would attract those industries with a high demand for compressed air. Also, alternate generation methods aside, if adequate (and safe) storage capacity was inherent, this storage could be recharged with electrical compressors during off-peak hours. That said, I do agree it seems air motor/compressor efficiency has much room for improvement.

I've been thinking of using compressed air for my house, though the thought of generating my own through electricity is what stops me. The expense would just be too great. If I could somehow move to another place where I could install a wind-driven compressor then I wouldn't hesitate. I wouldn't be a complete convert though. I'd still have some sort of way to switch back to electricity in case something goes wrong.

Compressed air use for the home is not the same as for a factory. I could think of some uses like ejectors for vacuum cleaners, air for power tools in my workshop, air-powered washing machines, dishwashers, blenders, etc. I might even go for pneumatic doors.

However, a centralized compressed air facility for an area seems terribly troublesome. It would be easier to troubleshoot, I agree, but fixing it is another thing. And the failure rate might be higher than electricity.

Of course, if the world had gone to compressed air in a big way rather than to electricity, we might have developed better reliability.

Madscientist, yours is a brilliant project, CAES(Compressed Air Energy Storage) has been around for a long time. There is one in Germany and US,each, and I read that they're planning to build more. Basically, concept is much like pumped up storage, except in this case, off-peak power is used to compress air and stored in subterranean salt caverns. At peak loads, same air is send to gas turbine - minus the compressor stage.

Going a step further, if this air is processed using VSA or PSA or good old distillation, oxygen could be separated and stored separately, to be reused in an oxy-fuel burner. This way, no parasitic loss to nitrogen or carbon dioxide take place as in normal combustion process, and the separated nitrogen(still under pressure) could be passed thru' heat exchanger/regenerator to extract almost all heat from the turbine exhaust!-to be re-directed to low temperature power turbine.

You could use wood chip, garbage, coal for fuel or make your own acetylene and set-up a real tight oxy-acetylene burner/heater.

W.r.t national grid, the idea would take off better, I feel, if there are more local area networks of compressed air consumers. In time, there are bound to be a few Inc. which would see big money all over this concept.

Re-conversion to electricity would also be easy; turbocharger turbine(compressor/blower not required)+externally heated heat exchanger+alternator/dynamo.

Sorry to interrupt: CO₂ is the normal result of a fuel burning reaction.

Gwen, I was actually referring to trace quantity in the atmosphere..........(after reading your comment, I realised this quantity was too small too include in my post, the way I did!!!)

I just wanted to agree with others who feel there is a HUGE demand for compressed air in industrial plants. Every plant needs compressed air, and some plants use more air than they do electricity for tools, vibrators, air pads, painting, sand blasting, etc.

It would be much less expensive to have one air compressor, one air dryer, one compressed air filter...versus many separate systems. The example of an industrial park is a great one, and I think the use of shared compressed air equipment is a great idea.

www.compressedairdesiccant.com

I have been working on a concept for a stirling engine/wind turbine solution for off-grid rural application which stores it's excess electricity in the form of compressed air in a reasonably sized tank above ground - for later use (as a battery if you will). The need is for small scale applications, as in a small farm which produces fuel on-site as a by-product of agriculture. The specific source of fuel in the concept I am working on would be bamboo fed using a spring-loaded hopper of a particualr design - as the tropics are the intended region for use in the case I am working on.

Are there small air driven turbines uniquely suited for converting compressed air back into electricity? The heat recovery and air compressor aspects need appropriate components to flesh out the system, as well as an air driven turbine that would be appropriately scaled and is readily available (in production now and acquirable for a reasonable cost). I am curious if a tesla turbine built for such a purpose would work efficiently enough to translate the stored compressed air. What PSI and what volume would be required to generate 10 Kw using a turbine with 70+ efficiency?

A stirling motor (i.e.- ST-5- http://www.stirling-tech.com/stirling/stirling.htm ) operates at 55% efficiency creating 6.5 Kw at 5 H.P. as opposed to 35-45% for ICE generators. Also, the benefit of wide range of fuel types for combustion in the stirling engine scenario is perfectly suited for the rural agricultural end user. The waste heat from combustion could be used to heat water and dry foods, as well as reclaimed in a heat exchanger for use in refrigeration (very useful in the tropics).

I am not an engineer but an active thinker with a concept that I think would provide reliable off-grid clean power to developing countries and rural residential energy consumers. Any thoughts or improvements on the concept would be greatly appreciated.

There exist air driven turbines to power small equipment in EX zones. (to avoid power cords and plugs) The problem is that these are typical small power (max 100W)

I fear that you will have to develop them yourself, or find someone who is interested to do it.

Do never forget that air compression is a costly form of power usage (lot's of the power goes into heat) When you decompress the air will cool heavily, this could be used to improve the efficacy of the Stirling engine.

The idea to use air is not new, and I have to admit that for tropic of grid use it is not so stupid: you need only little knowledge of maintenance to keep the system running.

But: what about the air reservoir, you will need to pressure test it regularly. And you will have to build a serious one.

Combined with the air driven cars you could set up a perfect system to have a basic transportation in small rural area's.

Some key items to take into account:

1. Go for maintenance and lubrication free apparatus. if you loose some efficacy it will be gained back as soon as you see that the system keeps on running without spare parts (always been the sore point of mechanical system in Africa)
2. Keep it as simple as possible
3. Go for proven technology
4. Involve locals as much as possible, even for the design. (This means that you need a clear case to start with, not the inverse: a system which needs a user)

Success, and if you need cooperation you may contact me (system evaluation / calculations)

Gwen

Hi Gwen

I knew you had become accepting of the central compressed air idea with your comment, "not so stupid".

For reservoir capacity it is easy to gang them together. They could be individually isolated for service and testing. Also in a compressed air grid additional reservoirs may be located at advantageous remote positions to bolster the system. While the main line may be subterranean it is easy to put a reservoir above ground as desired. In addition if serving the compressed air requirements of multiple facilities in an industrial park each individual facility may have it's own in plant reservoir fed from air central.

Tom

Thanks Gwen, for your input and offer for calc's, etc..I can guarantee I'll need your expertise there. I am designing for two specific NGO off-grid tropical agro-forestry / permaculture farms whose intention is to increase and diversify their energy sources. One is using a honda 3000 ICE for lights and pumping water (as a startup energy source - they are new and remote REMOTE) the other uses PV solar system exclusively and is 2 miles up a river by dugout canoe. I spent 2 months, 30 days at each place inspecting their situation and in each case, a Stirling motor was hands down the solution for their needs. The cost of maintenance is as you imply, the primary concern, as the system must be built to last as long as is materially possible. Reducing the moving parts to 6 axles(very few moving parts) is what I have determined is possible in such a system. Count them:

1. The piston in the stirling(1)

2. The Stirling shaft for external belt pulleys,attachments, what have you

3. electric generator (1)

4. rotary screw compressor (3-4)

5. Air turbine shaft (Tesla turbine/generator combo)(1)

Total moving parts (9)

however:

You add that the storage tank is a liability and must be tested for leakage regularly. All joints in the air system are possible failure points but relatively easy to fix without complex equipment or knowledge.

If components of this system are designed in combination, that is, if the tesla turbine and generator were one unit, and the stirling engine and it's generator were one unit, etc, elegance could occur.

What I see is that the Honda 3000 ICE generator is a beautiful piece of machinery, running 2 years without a hitch. The users I met loved it. One problem is that it costs 5 gallons of gas by truck to town to get more gas for the generator. The wear and tear on the truck is another, and if any of it's 500 moving parts fails, the whole device is useless and requires taking it in to be serviced by someone who has unique knowledge and access to the greater economy at large to tap the honda parts distribution system to get the machine up and running. Independence from such a costly and unsustainable energy exchange is what these people are trying to implement. By learning how to make fire if you will, homo sapiens entered the next era of their evolution.

Energy independence is a matter of layering functions for individual elements - (co-generation) and doing so by eliminating the complex components which require esoteric knowledge to maintain. Simplicity in the solution is a solution as far as I see it, especially when you imagine a scenario in which all distribution networks are no longer operating. Sustainability is achieved through the resources of community (the people themselves) so I agree completely with your comment about designing with the end-user/community in mind.

Air compression may be inefficient use of energy but it is a secondary conversion of the primary source of energy so that:

You burn as efficiently as possible 100 lbs. of bamboo, converting it to ( 8600-12900 Btu/lb) for an avg. of 1 million BTU's converting it to electricity on the spot at 55% efficiency (15,000 watts) over a 4 hour period. Say that energy consumption is less than that. You have already burned the fuel, so rather than let it go up in smoke, you store it. This would be done by pumping water first, then when tanks are full, dumping energy to the air compressor to store the energy there, for use later, day or night without the environmental hazard of toxic batteries and their short term life-span and high cost.

Each step has it's inefficiencies but in terms of harnessing the most out of those BTU's, in an environmentally friendly way, multiple functions and storage regimes are needed. The more elements for single functions and the more functions for single elements in the system, the better. But as you add these together, complexity begins to have it's own cost. That is what a Honda generator is, a costly stacked assemblage of elements or parts for a single function. And each part depends on another system for replacement. You can't make your own replacement parts and you can't fix it yourself without knowledge that is specific to that device which is unapplicable to anything else. Learning to fix such a thing is a costly way to spend your time and energy. Your time is better spent in dealing with the yields the energy makes possible.

As for air cars and suspended podcar tracks and an urban future where people are liberated from renting space on asphault, I think that capitalism itself is the biggest obstacle preventing positive change.

When the Iron Law of Oligarchy is applied to the economic thrust of a nation, a country such as the U.S. create markets that bully out competition in favor of their own hegemonic agenda's. The elite class of most countries have turned from considering their social contract with the people they affect because the game has become New World Order consolidation of power into corporate hands, bolstered by government endorsement and policy. This is fascism as Mussolini described it and unless people make a shift in consciousness away from the opiate of television and become conscious of global events and get involved in local cooperatives to grow their own food and form active political bodies functioning locally, in short, taking government back into their own hands, the corporations will continue to drive amorally toward the endless pursuit of profits and continue their insatiable extraction of resources according to an economic model that states these things are limitless.

Of course resources are not infinite. So in order to design the future to incorporate industrial parks that are consciously improving their efficiency model continuously and design car tracks to make commuting in cities more efficient, one has to believe that there is a solution to the political predicament of corporatocracy and oligarchy. But the debate is really whether human communities can be healthy and productive and sustainable in groups larger than 100. Which leads to the question of whether food can be made available at such great cost year round in massive grocery stores. Tomatoes in US markets from Argentina in December are a component in an economic machine that itself is completely inefficient and unsustainable. If everything we eat costs more in calories to produce than we get from it, we are living on credit. Oil is that credit.

So, how do you compress the air in the first place?. How do each of us personally, make and consume energy?. Nothing will be a perfect exchange or totally efficient but it's really damn easy to be in the black if you decide it. And if we collectively decided it, the values of our society would shift and through consensus shape a future to allow all the solutions mentioned on CR4 to happen.

In all this I am personally considering the developing world, especially areas where the living pharmacy of the planet is located, namely Central America, in the library of plants and animals there that must be protected and secured from the present trend of slash and burn and corporate agri-business which uses pesticides, fertilizers and genetically modified plants to trap local farmers in cycles of servitude, not to mention the ecological cost to the land and loss of biodiversity. All of this activity amounts to a machine about to run out of gas.

I am interested in what happens to the worlds' cities and what they'll look like in the future but I am more interested in what cities will do if the food they require stops coming. I am interested in what would happen if cities became responsible for producing all their caloric needs and were thereby sustainable. I live in Seattle and there is talk of municipal investment in wind farms as a major step toward liberation from the regional Grid. The time may come where cities are forced to buy energy at exorbitant cost from an Enron kind of regional utility conglomerate, enslaving the populations of multiple cities. In Central America as in many places worldwide, energy costs 1/4 of the monthly wage. In Bolivia, Bechtel was attempting to acquire ownership of water rights for a majority of the population, intending to charge 1/4 the monthly income of Bolivians for it, even when water ran freely nearby. Together the numbers in such a scenario equals half of a persons' income for the month. What would it be like in the USA if 33% of income went to taxes and another 50% went into clean water and electricity/energy needs; 17% of your income would be left over for food and housing; that's the way it is in developing countries, so they go without clean water and energy and grow their own food. So, if you can do the same thing here but acquire the implements for liberation from energy servitude now, you would be outside of the stranglehold. You can put to use state of the art technology available (magnetic bearings, precision machine parts, etc.) and apply it to a local energy and food production system geared to manage soils sustainably and provide low cost- energy and well water for small communities, as models, then as examples, then as spawners of the model, then as systems of users utilizing the model, thereby a future with Human's in it will have the greatest chance of being sustainable. I hope we can get to it before cities and economies at large collapse of an insatiable consumption of resources on credit that comes due all at once.

So in spite of what seems, it is time for me to get to the nuts and bolts of the system I have described and find the best elegant solution for the design of it's parts and connections and build the prototype and put it to work and document it from as many angles as possible and then demonstrate it and make it available as a turnkey system for the wide market of off-grid users in the world at large. I am interested in an open source mechanism for it's development as well if anyone is interested.

Thanks again,

Benjamin Higbee

Quite some heavy epistle you made.

I'm just an application development engineer / system architect.

You are right on the powerful qualities of Stirling engines.

At the moment there are some nice evolutions on these great machines.

NASA did some extensive research and some firms are continuing this to make real applications with it.

The idea of making compressed air direct from the mechanical action available in the Stirling cycle is great as you don't need to consume it directly, it is stored on the grid.

A Stirling engine with a multi purpose burning chamber could work on everything that can be burned.

When the pressure goes down you need to burn more bamboo.

There already finished units that burn gas fuels and make electricity, in both stand alone and grid connected units.

How real is the project?

As I said before: keep it simple and splitting functions enlarges the functionality and reliability.

Gwen,

project is very real, I have two NGO permaculture/tropical agro-forestry farms in rural Belize waiting for the system to be spec'd out, priced, built, tested and shipped. I am now doing the ground work finding parts that match the task, costing the fabrication of specific pieces, then I'll assemble and test a prototype here in the US and then dismantle and ship there. Most parts will be off the shelf solutions to fit together. Eventually the idea is to make a robust housing - contain all within a shell with components elegantly and easily attached to fittings. That's the plan.

I am working to design the final product to coincide with their specific needs on the first unit. If the prototype we build works well for them, we will have a turnkey solution to make available for many many similar operations in Belize and beyond.

So, i have alot of work ahead. any help with design / components that fit would be great...

if interested, I can email a schematic in the next few days that gives overview of the flow of the powerplant and what it will need to do...

email: zeitspiralez@yahoo.com

Benjamin Higbee

Remove your E-mail adress, if possible (sometimes I can click on edit of my own contributions)

if you have enough air for 10 Kw, build a blown in place cement tunnel to fit the span of the 10 Kw wind turbine you choose, seal one end (smoothly) against your compressed air source. vane style air motors are available only up to 5Kw nominal output, but would not turn a 5Kw generator. the 10Kw air motor you and i both want does not exist, but if you google<<< di pietro rotary air engine >>> you will find the pick of the litter for 'in development'. but i include here my own take on stirling, wind, and solar. i will post the below somewhere else too, dont know where yet.

POWER FROM A CONVECTION LOOP:

this is a scaled down version of the solar tower updraft system planned for austrailia, or the SHPEGS project with water/silica jell,(or cacl) adsorption, instead of ammonia absorption, or the water spray downdraft 'culvert on a hillside', proposed for hot dry climates.... or is it a solar hot, creek water cold, stirling motor with gravity/adsorption/psi assist?

MY SMALL SCALE PLAN:

I have a 10 acre property in bc, canada, with a very cold, (7C seasonal avg), creek water intake ~ 80' uphill, reaches my waterbox at ~40 psi, the overall grade is about 35%.

a wind turbine, (kicks in at 5m/s, out put at 8m/s = 10Kw), with 18 foot span is the basic buy;

two blown in place cement chambers, (see monolithicdome.com), are the basic build:

the top chamber is a 10' diameter by 10' long cylinder, under ground, sloping downhill. 20, or so, cold creek water misters, pointing downstream, form a ring around the hot air inlet. a small amount of excess water is collected at the lower end; can pass as preheated domestic, or be ambient cooled and let back into a smaller creek that i have nearby.

a buried 2' air duct runs 150' down, (drop = 50') to the wind turbine, which sits in the the mouth of the larger, 18' diameter by 30' long, hot air chamber. BUT... this humid air would be very hard to heat and lift, AND when it got back to the top, almost saturated, the cooling effect of the spray would be severely reduced.

so, after the turbine, in the bottom of the solar collector i have a desiccant bed/wheel ... um .... er ...of some sort. this absorption bed begins the heating cycle by removing the water. i have two ideas for this:

1 a silica gel desiccant wheel --- these exist for
smaller diam ducts, scale up and build. the saturated
part of the wheel is regenerated by the hot air trapped between the black cement collector, (get to that in a sec), and its ETFE skin. might have airflow issues, but..... here is a question that vexes me: is not heat the end product of the airflow issues? is not more heat a good thing anywhere after the turbine? same question for the interior heat transfer pipes inside the black tube that may be called for: is not friction here at least
breaking even, as it adds heat?

2 fill the bottom third of the hot cylinder say, 2 feet deep with rock cacl as the adsorbent. at the lowest point, a drain takes the cacl/water mixture out to a reservoir. a pump circulates this up to a solar evaporator bed, running back down to the base of the lower chamber. (again, hot air from the trapped space can be used here). the recrystallized cacl gathers at the base of the black tunnel, and a chute periodically dumps this back in. the only energy cost here is pumping the same volume of water that you remove, (yes, its denser), up 35feet. i think a couple liter/min is optimistic, as heating any amount of water up 100C, (this is my 24/7/365 projected AVERAGE delta T... read on) would take more energy than pumping it up 25 feet. in fact the more water, the better for my prospects, right?

HEATING CHAMBER:
a blown in place cement tube,(nickel or carbon black outside surface, selective thermal topcoat), with inside diameter 20', length 30', contains a blown in place cement tube with outside diameter 18'. the two foot 'jacket' is filled with heat transfer fluid. the 10 meter long inner section runs back uphill, smoothly enters a (shorter) air duct that connects with the spray down chamber. this hot return section, again 2' diameter, is spray foam insulated and buried in a perlite trench.

this large volume of htf enables:

domestic heat,(did i mention that the system will provide all domestic heating and removal of heat?).

fluid to circulate in the interior heat pipes: to stay
out of the airflow, these are put, infloor heating
style, on the bottom of the inner cylinder, (this adds to seasonal thermal storage as well).

diurnal storage: i have sized the htf volume and aperture for 7 hrs exposure = the btu's it takes to heat my house for 24 hours when it is 20c below, PLUS the amount of heat loss from 24 hr wind tunnel operation. these kind of cupped cylinder, black body collectors convert a healthy percentage of solar energy into btu's. even if i only get 50% of the energy falling in 7 hrs on 100 square meters, (10 meter by 10 meter collector area @ ~~1000 watts/sq meter) into btu i have lots. even in this dead of winter, worst case scenario, there is a cold air bonus available. by use of a venturi valve the cold water at 50psi can draw in outside air: you can tune these as to how much air but, due to nucleation issues, the water would not freeze until minus 7C, or colder. (i have tried to make snow this way...it does not work)

seasonal thermal storage: sizing this big will give tons of heat in the summer. the black tube sits very close to bed rock so, with little effort and a minor cost, shallow, vertical heat pipes are bored directly below the hot section, (ten meters deep x one every few feet). very small retrieval cost as the tube sits right in the hot plume.

the look of the entire solar collector is very close to a scaled up solar batch heater. anodized aluminum parabolic troughs cup the black cylinder and bring the width out to 10 meters . a cable tensioned ETFE membrane covers the 10x10 meter aperture.

this is NOT a million dollar build:

100 sq meters ETFE foil = $15,000
cable tensioned ETFE support structure = $10,000
10 Kw wind turbine = $20,000
200 feet of 2' air duct, trench, perlite = 8,000
many gallons of heat transfer fluid = $10,000
two, (well, three really), blown in place cement chambers = $100,000.
10 6" by 10 meters deep boreholes; 60 meters @ $300/meter = $18,000

GRAND TOTAL $182,000

my stirling question is this: if this thing just laid flat it looks like a sterling setup with potential, but no potentiator. the air would still want to move from the high pressure to the low pressure chamber, but would probably form loops in both air ducts; ie it has no direction. but, aided by that 50' drop and nudged again by the nozzles, flow is established and no air goes the wrong way. therefore, one should get at least the output predicted by stirling formulas that take swept volumes and delta T as inputs. i have seen this formula somewhere online, plug and play style. my own Fermi estimate is that, at summer solar max, with the hot air at ~ 160C and cold at 10C, there may be too much wind for a 10Kw turbine.

ok, let the torrents of 'yeah but's loose. i am posting here to put this idea up against rigorous thinking, but helpfull suggestions very welcome too.

regards duke

my quote "damm the o-rings, we have GOT to launch"

If a conventional one piston air compressor pumps X amount of cu inch per revolution into a tank, could I use a smaller electric motor if the rotor compresses one sixth every 60 degres so the total volume per revolution is the same . Stroke of piston and dia of rotor would be the same .

To the best of my knowledge the rotary compressors use approximately the same amount of electrical energy to compress an equivalent amount of air as the reciprocating compressors. I am not sure if they use a smaller motor at more or less continuous load vs the half cycle load of a recip. Most of the compressors over 30 horse power that I see in industrial plants are rotary so they must have an advantage.

If you want to find out more about compressed air systems there's some information at the bcas website, it's short for British Compressed Air Association. Hope it helps.

If you want to find out more about compressed air equipment there's some information at the bcas website, it's short for British Compressed Air Association. Hope it helps.