Hi, See my reply to my friend, Swift. I think it is quite possible to have an efficient interface with wind power and compressed air.
I served in submarines, and we used compressed air routinely, at several and many pressures, and in clever ways for purpose. Parallel thinking on a large scale.
Best regards, Dan

What? No diamonds?

__________________
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T. Anderson

I'm a bit worried some people think, by using plastic toys, we are "sequestering carbon". You are not. Plastics are made from oil. The sequestering happened hundreds of millions of years ago so does not count now.

Compressed air: London used to have a public compressed air supply much the same as a gas and electricity supply now. Also parts of Liverpool I believe. Some of the pipes are still there.

You would need a large tank of very highly compressed air to power a car for an acceptable range. What happens in an accident?

Hi, We have ways of containing compressed air. This technology is well understood. Please understand; we had no need of alternatives when gas was 23 cents a gallon. You may live to see many different and peculiar technologies come out of the woodwork,...for many reasons.
If your daily travel does not exceed a 60 mile round trip, you might be a candidate for compressed air. I had heard of claims substantially further than that. 200 was mentioned. Remember: you can be dealing with super overdrive
and other things. Nothing is wasted in this kind of propulsion, and you can use your air system for braking. We shall see this and more in the very near future.
My pleasure talking with you. Best regards, Dan

Again, what happens in a collision?

A large quantity of extremely compressed air is hardly a safe proposition if the tank is ruptured...

I think our best bet is nuclear and hydrogen, with the hydrogen produced with the nuclear power. This is really the only reliable, zero emission technology that could produce a significant fraction of the electricity we need, and would also allow for thousands of years worth of fuel with no worries of running out, and no fluctuating prices.

Hi, Did you know that hydrogen is held in a high pressure by the same technology that holds high pressure air? And....in a collision, you can employ an
impact shut-off. It is much like an electric shut-off. You need not fear the instantaneous release of air. You need quality components ,of course.
What I advocate is a very dispursed technology, instead of an extremely
centralized technology. And it makes jobs for people. That isn't a bad thing.
Best regards, Dan

Shut-off valves would do no good in the case of a cracked storage tank, although I agree that a leak or explosion of hydrogen could be worse than a leak or explosion of plain air.

And we could debate whether or not "making jobs for people" is actually a good thing...

There is an advantage to compressed air in that we don't have to expend much energy to harvest it, and it time it should provide us with more energy than we used to obtain it. But the same could be said for hydroelectric power, wave-generated electricity and some other novel methods. Yet we don't see a massive exodus to abandon oil for them. Why?

The question is not whether or not we can make these technologies work. The question is: Can these technologies provide us with enough energy to meet our demands? What happens when the winds die down for a couple of years, say due to a variation in climate? And what about areas that don't experience a significant amount of wind, or don't have access to waves/rivers/geothermal sources?

The reason why these things aren't as practical as oil is because they aren't as distributable, they aren't as practical, they aren't as ubiquitous. Oil can be harvested in one place and shipped anywhere. It can be used as fuel. Or to create other fuels, or even other types of energy. Which makes oil useful for many things. Compressed air might run your car, but it won't power your A/C. Or your heat.

To save the environment is a worthy goal. But people want things. The things they want require energy, and lots of it. If getting a better energy source means that people are going to have to sacrifice all these things, I fear that we will use oil until there is none left.

Hi, High pressure air flasks have been around for a good many long years. They are transported each day on our many roads. This is a non-issue. And they are not made of glass. Their demeanor is governed by set regulations.
Hydrogen is less trouble than most any other inflamable in that it surely rises up and away from trouble, unlike gasoline and other fuels.
New industry in America is surely welcomed, especially if you have children to feed and taxes to pay. I should think that there would be not a great deal of debate about that....unless you are heavily invested in oil, and even these people are not without some civic sensibility. But this is not a jobs forum.
My purpose was to reflect on the very necessary and genuine alternatives which, although not picked up by the press, may have merit in the near future
and which philosophies may indeed be pondered by those in a position to advance them. I suppose they thought DaVinci was a quack when he invented the gated lock for canals , yet in time, even the Panama Canal was concieved
and flourished as real. Mechanical vision and innovation require time and necessity. Soon, we may need to find the time, and it may become necessary.

In consideration, I should say that we shall require oil for flying. Difficult to
get around that. But any technology that keeps dollars on our shores will,
in time, be welcomed and indeed praised. And this will redirect precious oil for industrial requirements,such as they are. It all depends on your point of view.

If a compressed air tank is breached, there will be a release of the contents. Yes, sometimes the release can be violent, though brief. These tanks are very substantial, made of ductile iron of considerable thickness (10-20mm). Vehicle gasoline tanks are made of sheet metal (about 1mm thick). They are much more likely to rupture in a crash than are compressed air tanks, releasing tens of gallons of very flammable gasoline. Your choice; release of (non-flammable) air or raging conflagration!

__________________
Any day you wake up on "the right side of the dirt" is a good day.

T. Anderson

Well said, Sir. Ductile steel. It's only enemy is rust. They have a safety inspection program for high pressure air flasks that works. It has been around for many many years indeed. And compressed air is less trouble than acetylene or
pure oxygen. As has been said, it is a known and familiar technology.
With the advent of excellent synthetic oils as lubricants, we could consider the operating mechanisms to have an amazing usefull life in service,owing to a dust free input.
Best regards, Dan

I'm probably asking for trouble here, but I don't think compressed gas or hydrogen are likely to be used to store energy in the future. Although new materials could make compressed gas a more attractive option I think there is more room for improvement with batteries, capacitors and flywheels.

As for hydrogen, why not produce methane instead as it is easier to store and can be used with the existing natural gas infrastructure? (Hydrogen may be used as an airplane fuel because of its high energy to weight ratio, but the fuel tanks required will be enormous because of its low energy to volume ratio.)

Hi, If we continue to employ combustion in our vehicles, we may re-visit
steam, especially up north where we can enjoy particularly excellent efficiency
in the condate cycle, getting even more energy for free! We do it in Naval steam cycles all the time, as do many power plants that have cooling water.
In a vehicle, with better batteries, a steam/electric hybrid may become especially attractive . I always liked the idea of an steam/electric monorail.
Time will reveal much.
And yes, Methane is a usefull fuel, if you can harvest enough of it. It still generates CO2. however, but it could be generated on our own shores.
What do you think?
Best regards, Dan

Methane is the primary constituent of natural gas.

__________________
Any day you wake up on "the right side of the dirt" is a good day.

T. Anderson

When you compress and decompress air you are also inescapably in a heat cycle.

From what I can quickly find out, current compressors lose 90% of the energy as heat. So much so that large plants can re-use this waste heat to increase overall efficiency. These are industrial compressors that do not get up to particulary high pressures either. I suspect the efficiency goes down the higher the compression.

When you decompress a gas, after it has been cooled to ambient at high pressure, it cools. Anyone can see this by letting off a CO2 fire extinguisher and observing the snow, and the fact you can get frostbite by holding the the nozzle. This detracts from the energy, I guess it could be made better by building in a large heavy heat exchanger to take out heat from the surroundings.

Anyway, the overall efficiency would not seem to compare favourably with electric batteries or fuel cells. Although I agree it has the attraction of simplicity.

All these ideas are fine in the short run, but to escape the stone age and fire, we must look to the inside of the atom to become a full fledged type I civilisation and survive for the long term.

Hi, If you consider that the source of the compressed air could well be found in wind energy, and that it is completely non poluting, and that the industry remains on our shores, there may appear to be a considerable
weight in favour of such a scheme. Eventually, the plant pays for itself, and there is very low wear on such systems.
As for the cooling process of expanding air, I expect that can be taken advantage of by employing this in a local chilled water system for air conditioning,which usually takes 15 HP and kills your mileage; yet another plus for this design.
You are peeking at the future through the key hole. It remains for us to open the door.
Your questions are welcome.
Best regards, Dan

Dan,
I'm trying to figure out what you are proposing. How exactly is wind energy converted into compressed air? Are you suggesting the wind actually fills the gas cylinder? I'm guessing most compressed air cylinders are ~1000 psi - I can't imagine any wind driven system filling that.

I suspect you are proposing use a wind turbine to either directly run an air compressor, or have it run an electrical generator and use that to power the air compressor. But I just wonder if the combined efficiency of such a system is economically viable. I'm greener than most people (two hybrid car household for example), but people are not going to voluntarily double or triple their energy costs, so economics is important.

As far as "very little wear on such systems"; do have any proof of this? Are you talking about the car or the air compressor system? Most air compressors do require regular mainentance. It might be no worse than a typical furnace (I just don't know), but such considerations such not be lightly dismissed.

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You seem to favour a highly centralized system with extraordinary costs,
along with the finite use of such systems before their BURIAL, to say nothing of the danger they pose. They are only necessary on submarines, where we must employ such systems to protect our country, and must needs bear these risks
and spend those monies.
I shall never be in favour of such a hideous scheme as nuclear power, It is worse than a devil's bargain, and shifts it's economis burden to your children.
In this consideration, when all the cards are on the table, it is worse than bankrupt. There are alternatives.
Best regards, Dan

There are alternatives. . . ...and then there are cost-effective alternatives.

People, as a whole, don't want to sacrifice one little bit of the staus quo to get cleaner energy. Which is why electric cars, hydrogen fuel cells, etc. just don't catch on. It's cheaper to do things the way we have been. Until there is a marked ECONOMIC advantage in changing to another source, it probably won't happen. Comparitively speaking, there don't seem to be many advantages, economic or environmental, in going with wind-generated compressed air versus any other method.

And as far as nuclear energy shifting an economic burden to our children, that's the same as every other power source. They all have an economic effect on the generations that come after, be it the threat of nuclear contamination, of running out of fossil fuels, or of global warming. We will never find a source of energy free of any kind of trade-off. Even burning wood releases biomass to the atmosphere. If we moved to wind-generated compressed air, we would sacrifice our skylines and the beauty of our natural landscape. (Why go to such lengths to protect it if we are only going to foul up its appearance with an endless string of huge wind turbines?) And I have severe doubts that there is enough windy terrain on the Earth to even generate enough wind to compress enough air to provide everyone with all the power we need.

I have a hard time seeing this as a universal answer to the problem, especially since compressed air has no capability to generate electricity. But, it might pay off regionally, in areas where wind is plentiful and skylines are not an issue, and where people have non-electric appliances.

Hi, I suggest that the compressor be directly coupled to a large wind turbine.
There is no question about the available torque, and if you have seen much about synthetic oils like M....l one, There is indeed a long life to such equipment. None of this is rocket science, save the handling of compressed air.
Direct mechanical torque to make compressed air must surely be the most efficient method of making it. This mechanical linkage doesn't require high rpm, and as wind speed goes up, engage more compressors.
Actually, you simply release the dump valve, which then places a load on the compressor. This is done on heavy trucks every day. (In this case, there is a air actuated load valve, which when depressed, simply exhaust air in the cylinder and no compression occurs. When the air pressure in the tank goes low, the demand valve close and a load is placed on "that" compressor and works untill the set limit is reached and then the valve is depressed again.
Mechanically automatic.
Does this illustrate a solution for you?
Best regards, Dan

I suppose that it is much more beautifull to continue to deal with foreign countries and the oil they continue to charge more and more for.
When oil is $6 a gallon, does wind look better? Maybe.
Oil is the embedded sytem we grew up with. We are going to have to use less of it, and pay more for it. That is Certain. Developing a parallel system that weens us away from such, and makes jobs for US working people, and keeps us economocally strong in the process can't be a bad thing. Just different.
Times change, and people change with the times. Do you still have an 8 track tape player?? I should think you have a compact disc player and back up your music for pennies , unlike 8 tracks which got eaten and thrown away.
Ultimately, oil will be the 8 track system of older days.
Best regards, Dan

Hi, I suggest that the compressor be directly coupled to a large wind turbine.
There is no question about the available torque, and if you have seen much about synthetic oils like M....l one, There is indeed a long life to such equipment. None of this is rocket science, save the handling of compressed air.
Direct mechanical torque to make compressed air must surely be the most efficient method of making it. This mechanical linkage doesn't require high rpm, and as wind speed goes up, engage more compressors.
Actually, you simply release the dump valve, which then places a load on the compressor. This is done on heavy trucks every day. (In this case, there is a air actuated load valve, which when depressed, simply exhaust air in the cylinder and no compression occurs. When the air pressure in the tank goes low, the demand valve close and a load is placed on "that" compressor and works untill the set limit is reached and then the valve is depressed again.
Mechanically automatic.
Does this illustrate a solution for you?
Best regards, Dan

I think the question is, how does the efficiency of the
wind->compressor->pipe->engine

cycle compare to that of,
wind->generator->electric distribution system->battery->motor?

That's for vehicle propulsion BTW.

I suppose there's another variation,
wind->generator->hydrogen->distribution->engine or fuel cell.

At the moment, although I'm attracted by the simplicity and reliability, it looks like the efficiency of compressed air is less than 10%, whereas I think you're looking at say 70% for electric or hydrogen cycle (the latter used in fuel cell).

BTW I appreciate the air conditioning suggestion, at the mo I'm looking out at a rainstorm in semi-darkness at midday, the temperature is about 9 degrees C and air con is the last thing on my mind. My guess is a compressed air motor in a road vehicle would end up a frozen block of ice very quickly.

nHi, I sympathize with your present temperature. Severe cold is damned inconvenient. At present, I have 49°, 20° above normal for this time of year.
I should think that the air system I suggested is well higher than the 10%
you suggested. I'll try to research this to give you something accurate.
The French have an air-powered car already. If I can put a number on wind-
electric production and translate this into mechanical compressive production,
we shall have a clear picture of efficiency. You never get 100%, but I don't see the spetacular loss in efficiency suggested in the 10% you inferred.
Electricity has all kinds of losses. It is simply familiar to us. The new designs
for compressed air escapement motors are remarkable, because they take advantage of the most efficient part of the power cycle. Understanding this advance in engineering, and the simplicity in compressor design, the case for
compressed air becomes more viable. Of course, people are in love with 6500 lb. vehicles. And airpower can move them.....but it gets expensive.
The nice thing about compresed air is that you can employ super overdrive.
There is no knocking involved with compressed air. Yet another advance in efficiency. The picture will become more clear in time. You know...when people first saw an automobile, many said...."Get a horse". In time, many
began to enjoy such contrivances.
Best regards, Dan

Is that degrees F or C?

Anyway, I've been trying to do some back of envelope calculations without much success. Perhaps some physicist or person with an engineering bent can help.

What would the air consumption rate be? I've been trying to work it out from first principles. It'd be a good exam question for intermediate level physics I think.

If you want a vehicle to travel at say 30 metre/sec (67 mph) and we guesstimate the power to do that is 30kW (40bhp), Power= force x velocity, the force is 1000 Newton (or roughly 100 kilogram force).

To provide that force at 30 metre/sec I've calculated an air consumption rate of 2900 litre per second (volume measured at ambient pressure). That's assuming no temperature change (which there would be).

Is that 2900 litre per sec anywhere near correct? If so, it's a lot, and your range at this speed would be very limited. There are some skeptical comments on the Wiki page on compressed air vehicles also, related to this.

Having said that, I think the desseminated nature and simplicity of the concept is great. I guess you could use the waste heat from pumping up your car (via the windmill) to heat your water.

Sorry, decimal place correction is in order. The volume is 290 litre/sec, not 2900.

But it's still a lot. If you stored it at 230 atm (the rating of most compressed air cylinders) you'd need over 4 cubic metres to travel for 1 hour.

[QUOTE=kzb;883483]Sorry, decimal place correction is in order. The volume is 290 litre/sec, not 2900.
Here's a site: http://www.theaircar.com/
Interesting.

Danscope, what I found interesting was the energy storage equivalent of the compressed air tank.

300 litre at 300 bar is said to be 46MJ of energy. Now it's not clear from the website whether this is the theoretical energy stored, or the energy as used in the engine, or even the energy put in to compress it originally.

However, taking the most charitable interpretation that this is the energy as used in the engine, be aware that 46MJ is only 1.3kW-hr (1.7 bhp-hr).

There appears to be an option for a larger 340 litre tank at the same pressure, equivalent of 52.1MJ. That is still only 1.48kW-hr (1.94 bhp-hr).

My lawnmower is about twice as powerful as that, and it runs for much longer than an hour on a paltry couple of litre of fuel. However I suppose that is a fossil fuel that we have to get away from. But I think the vehicle they are after backers for is actually a hybrid, it does use fuel to charge up its tank.