Compressed nitrogen to replace the power grid? Nope.
February 25th, 2010
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Lancaster Wind Systems says by turning wind energy into hydraulic power, inert nitrogen gas can be compressed in thousands of kilometres of unused pipelines across North America — creating a sort of giant pressure tank.
Wind turbines would add pressure to the network, and small electricity-creating turbines tied into the system would draw off that pressure, producing power in a closed-loop system right where the electricity is needed.
“You might have 200 generators in a major city, each in the 1.5-megawatt to four-megawatt range. And since the nitrogen is returned to the pipeline, there are no emissions,” said Dave McConnell, president and CEO of Lancaster.
He thinks electricity transmission lines will one day be a memory, with the continent’s energy moving around as pressurized gas. The project has attracted funding from the Sustainable Development Technology Canada fund, and also raised millions from private investors.
With 18 patents already filed and more on the way, Lancaster has a working one-megawatt wind turbine producing hydraulic power, and plans to open a pilot project this summer in which 42 minutes of energy will be stored in a short pipeline section. A major pipeline company is supplying the material.
A wind turbine today is basically blades turning a shaft in a generator unit that creates electricity, with all the heavy equipment at the top of a strong mast.
Lancaster has turned that around. Its unit acts more like a windmill, with a lighter mast supporting the blades and hydraulic tubing, and the heavy equipment on the ground.
Currently the research focus is on details of transferring the energy to storage.
“That is where we are at, the mechanism of transferring this energy into a vessel. We can’t talk about it, except that when the fluid comes down it is under pressure,” said Arnie Barr, a field supervisor.
McConnell points out there is no hydraulic fluid in the storage system; it is simply moved into a tank and then sent back up the mast to be recompressed by the power of the wind.
“There is a pressure exchanger to convert the energy in the (hydraulic) fluid into the storage medium (nitrogen gas),” he said.
….
After a lifetime in the offshore-oil business, McConnell said he returned to Canada with the idea of buying a couple of drilling rigs. But then he had a better idea.
If this is a “Much better idea,” I’d hate to see a worse one!
Basically what we have here is a simple pneumatic power transmission system. One which is envisioned as being so enormous that the pipes and the pressure tank are actually one in the same. There are two things that make it a bit different than most conventional pneumatic systems: first, for some inexplicable reason it uses a combination of hydraulics and pneumatics, instead of just one or the other. Secondly, for other unexplained reasons, it uses nitrogen gas, rather than just using air, which is 80% nitrogen to begin with and works just as well.
Unused pipelines?
If anyone is aware of these enormous unused pipelines across North America, they might want to let the natural gas companies know, because as it is, the gas pipelines we have are running near capacity and plans are already being made for more pipelines. Of course, for pipelines to be useful for this concept, they’d have to actually be located in the areas where power is to be transmitted.
There’s another problem, as well. If compressed gas is going to be used for power storage and transmission, it’s going to have to be at enormous pressure. After all, compressed gas doesn’t carry that much energy as is, and if the pressure is not very very high, the energy will be negligible. This means the pipelines will need to be capable of containing huge amounts of pressure. Any weakening or even the tiniest leak is going to be a deal breaker. If the pipe is corded or has any degradation of joints or gaskets, it will either explode or allow the pressure to escape with an ear-splitting hiss.
Only natural gas pipelines are designed to contain a gas at high pressure. With water pipelines, there may be a little bit of dribbling at the joints, and as long as only a small amount of water is lost, it’s not a huge deal. Even oil pipelines do not need to be built to the same standards for pressure containment, as oil is a thick viscus fluid that does not easily flow out of the tiniest flaws in seals. For super high pressure gas, however, the pipeline would need to exceed all exiting standards for pipelines.
Pneumatic Power Transmission History:
The use of pneumatics for power transmission is nothing new, and indeed it continues ton be used, at least on a small scale. If you’ve ever worked in a well equipped machine shop, repair garage or other such establishment, it’s likely that you’ve used a pneumatic power system. In shops, a large central compressor and tank feed a series of pipes which carry the air to work stations, where they often terminate at retractable hoses or connectors. If there is no central air compressor in a shop, or if air tools are being used in the field, then there are simple and compact air compressors that can be used to provide power where it is needed.
Compressed air powered tools have many advantages. They tend to be very light weight and can produce large amounts of power and torque in a small package. They are especially well suited to tasks that require reciprocation or high power impact force, which is why most nail guns, impact wrenches and jackhammers are pneumatic. The pneumatic systems in shops also come in handy for tasks like inflating tires or blowing away dust and debris from a machine. One thing pneumatic systems are NOT, however, is effecient. In fact, they’re about the most inefficient means of powering tools around, which is why they’re only used in circumstances where the advantages of pneumatic power outweighs the inefficiency.
However, compressed air power systems were once used on a scale far larger than a single machine shop.
City-wide pneumatic power systems enjoyed a brief period of success in the mid to late 1800’s. These should not be confused with pneumatic tube systems, which were used to send capsules from one location to another, as the power systems existed only to provide compressed air power to various motors or other applications. Dresden, Birmingham and Buenos Aires all had compressed air systems that served large city areas. The largest and one of the earliest such systems, however, was in Paris. The Paris system came into existence in 1880 and grew to include several small compressor stations as well as a large central power plant, located at St. Fargeau Station.
The initial purpose of the Paris system was to power and synchronize clocks. It relied on puffs of air to deliver synchronized time to each of the clocks, with the brief bursts of pressure pushing the minute hand forward. This would seem to be a fairly crude system, by modern standards, especially given that compressed air is not instantaneous, but travels, at best, at the speed of sound, and often much less. Apparently, however, the system was satisfactory for the relatively small distance covered. The “Pneumatic distribution of time” was first tested in Vienna in 1877.
The Paris system started off with six miles of pipe but grew to 16 miles of pipe, much of which was run through the Paris sewer. The use of compressed air for clocks was quickly eclipsed by the use of compressed air for various general purpose motors and power applications. The Paris compressed air power system provided power for not just clocks, but also factory equipment, church organs, sewing machines, fans and other small devices. Even homes were connected to the system, which had meters for billing, in a manner similar to the modern electricity grid. These homes were mostly those of the wealthy, who could power various small gadgets (clocks, fans, etc) on compressed air, thus showing how up to date they were.
While some cities used compressed air to transmit power, others used water. The London Hydraulic Power Company was created by an act of Parliament in 1883. One of the major intentions of the system was to relive the noise and smoke produced by the small steam engines that provided power to machinery. The system pumped water directly from the Themes, and although it was occasionally used to provide water for fire hydrants, the water itself was not the product, but rather the energy that the water provided. The water was pressurized to about 800 PSI by a number of steam-driven power stations. At its height, the system provided a total of 5.2 megawatts of power through a network of 150 miles of pipe. Other similar systems existed in Liverpool and other cities.
Decline:
These systems may have enjoyed some early success, but they came at almost exactly the wrong time. In the 1880’s, the industrial use of electricity and large commercial electric motors were just coming on the scene. Thus, pneumatic and hydraulic power distribution systems were obsolete almost as soon as they were built. Electricity is not only far more effecient as a means of power distribution, but it is much cheaper to run wires than to build large, high pressure pipelines. While most of the energy in a compressed air system is lost, electricity can be transmitted with losses of only a few percent.
The hydraulic power systems began their decline in the late 1800’s. By 1904, the hydraulic system of London had lost most power customers, who switched to electricity. The system began replacing steam-driven pumps with electric motors around this same time. By the 1930’s, the London Hydraulic company had lost nearly all its power customers – only a few elevators continued to use the power source by World War II. The system continued to work in a limited capacity until 1977, however by that time, it was only being used to provide high pressure water to fire hydrants and building fire hose connectors.
Most of the pneumatic systems began to fall out of use around the turn of the 20th century. By 1890, the main power plant of the Paris system had been converted to also generate electricity, in addition to compressed air. Compressed air also continued to be used to drive electrical generators in Paris for a short time.
It turned out to be electricity generation that kept the compressed air system alive, at least for a short time. As electrical systems of the late 1800’s were generally DC based, power stations had to be close to the end users. Thus the compressed air system continued to be used to power the generators at these stations from a central station. This eventually lead to a conflict between the Popp company (who operated the pneumatic system) and the city of Paris over the fees charged for the laying of pneumatic pipe on city property. The dispute arose from the fact that the city was charging pneumatic power and electrical transmission lines based on the total power produced. The city planned to tax the lines for the transmission of pneumatic power to electrical generators based on the power generated. However the Popp company pointed out that “a great part of the air had been used at a complete loss.”
Of course, this arrangement was short lived, as the introduction of AC power there was no longer any need to transmit power to small, local electrical generators and the Paris pneumatic system, and all others around the world were eventually shut down. The last portions of the public pneumatic service of Paris closed in 1927.
Conclusion:
In addition to the dubious claim of unused pipeline, pneumatic and hydraulic power transmission simply cannot compete with electricity due to its inherent cost and inefficiency. The idea of using these kind of systems for long distance power transmission is nothing new, and in fact, it has been done, but it ceased because these systems are so inferior to electricity. This whole concept is ridiculous.
This entry was posted on Thursday, February 25th, 2010 at 3:45 pm and is filed under Bad Science, Enviornment, Good Science, History, Obfuscation, Politics. You can follow any responses to this entry through the RSS 2.0 feed. You can leave a response, or trackback from your own site.
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February 25th, 2010 at 4:43 pm
Compressed air is one of the most expensive sources of energy in a plant. The overall efficiency of a typical compressed air system can be as low as 10-15%. For example, to operate a 1 hp air motor at 100 psig, approximately 7-8 hp of electrical power is supplied to the air compressor. For some facilities, compressed air generation may account for 30% or more of the electricity consumed. It is such an expense that comprehensive compressed air system audits are available from several specialized firms that do these as a business.
Based on this alone, why any competent engineer would have anything to do with these schemes is beyond me, unless they know that they are involved in some complex fraud.
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February 25th, 2010 at 4:48 pm
If this is a “Much better idea,” I’d hate to see a worse one!
Well, the air car is a worse idea. See http://en.wikipedia.org/wiki/Motor_Development_International
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February 25th, 2010 at 4:55 pm
Wow.
How did this guy get far enough past PV = nRT (implying that /\P ~= /\T, at which point thermodynamics eats your lunch) and still think that transmission over pressure is even remotely a good idea?
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February 25th, 2010 at 5:36 pm
Paul Studier said:
I’m just not sure which is the worse idea. You could make a case for either one. Both are horrible ideas, so the question is really only which one might be the more horrible.
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February 25th, 2010 at 6:57 pm
The nitrogen may be a safety requirement. With compressed air at sufficiently high pressures, the partial pressure of oxygen will present a significant fire or corrosion risk to steel pipelines. And that’s what high-pressure pipelines are made of.
Nitrogen would need to be extracted from air at the turbines, or returned on a secondary low-pressure pipeline network (still needing some compression to achieve this though). The same pipeline _cannot_ be used, as it would require you to magically repressurize the gas that you have just extracted a boatload of pressure energy from. Take note, McConnell.
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February 25th, 2010 at 7:17 pm
Submarines use 4500psi compressed air systems for deballasting (surfacing) as well as other services. O2 partial pressure is not a concern but other things are:
Entrained oil (picked up from the compressors) can cause “dieseling” if isolation valves are opened too quickly.
Moisture in the air is a significant concern. It can freeze up valves and lines if the pressure is dropped too quickly. In fact this is one of the things that killed USS Thresher.
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February 25th, 2010 at 7:24 pm
Why not use CO2? That way you could sell credits for carbon sequestration. (Until it leaks.)
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February 25th, 2010 at 7:31 pm
Thanks Chuck. I know that submarines use a lot of special materials, though, and the proposal was to use existing pipelines. If that is not possible, as seems likely, installing a high-pressure pipeline would be needed – which still says mild steel to me, for cost. This scheme simply looks worse and worse.
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February 25th, 2010 at 7:39 pm
Bill, the more I think about it, the return loop is simply not feasible, so you wouldn’t be sequestering anything – you would have to bleed it at the generator.
Also CO2 is horrible stuff to have in steel pipelines. Any water ingress and you can get ferocious corrsion rates.
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February 25th, 2010 at 8:21 pm
Bryan Elliott got it in one, the Ideal Gas Law rules in any compressed gas energy system. There is no practical way to cope with the thermal loses, or replace them as the system scales, without taking a major hit in efficiency. Consequently you’re screwed going in, and screwed again going back out.
The fact that these ideas keep turning up and getting any play at all, is a grim testament to the state of basic science education in high schools. No in the old days not everyone knew the gas laws, but enough did, that anyone floating an idea like this would have been laughed out of the room.
But watch, I predict that some commenter is going to eventually show up in this thread, lecturing us all for being narrow-minded for not thinking that somehow someone will find a way to violate the laws of thermodynamics, because this in his/her mind is how science traditionally works.
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February 25th, 2010 at 8:39 pm
Well there’s one other thing: If it used regular air then at least the cycle of compression and usage can be open-ended, but if they use nitrogen, then you can’t just vent that when it’s used, because then replenishing he system would mean having to produce nitrogen from atmospheric distillation at an enormous expense of energy.
Therefore, you would need to return the nitrogen, but because the nitrogen is both an energy carrier and a storage medium, you need the nitrogen to go into another tank – a much lower pressure tank, as mentioned in comment #5. However, if the pressure is much lower in the return storage tank versus the energy tank, then it has to be much bigger. Since you want as much pressure as possible in the system you might have the pipeline at a couple thousand PSI and the storage at about one atmosphere (~14.25 PSI) So the tank would have to be enormous and accommodate the flow of low pressure gas without reducing flow as it fills up.
Maybe they could use a gasometer (self-inflating low pressure gas holder) for this – or rather, many thousands of gasometers the low pressure end.
Then when energy is being produced, the system would have to suck the nitrogen back (through different pipes) to the wind mills where it is once again re-pressurized.
Of course, using all that nitrogen adds more danger to a possible leak. Now a leak also means losing your valuable gas and the danger that if the leak is great enough or somehow indoors or something, it could asphyxiate by displacing oxygen
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February 25th, 2010 at 9:37 pm
There are already existing plans to use windmills to pump air into aquifers to store the energy as compressed air, and the compressed air from the aquifer used to run a generator. Not the most efficient use of wind-power, but it enables the wind power to be stored so that you don’t need a backup generator for when the wind drops off.
Since the energy lost by transmitting the power as high-voltage AC over existing power lines is likely to be far less, or at least not much more than the energy lost by transmitting the power as air through pipelines, the plan to pump the air through pipelines makes no sense.
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February 26th, 2010 at 2:00 am
It just goes to show you what an achilles heel energy storage is for renewables.
Of all the kooky and impractical approaches to storing renewable energy that I’ve seen so far, I think the idea some japanese researchers came up with is the most charming; build depleted uranium or neptunium(!) redox flow batteries.
E.g. http://www.imr-oarai.jp/en/research/research4-5.html
In order to store even a small amount of energy, say a gigawatt*day(~15 minutes of storage for the entire japanese grid), if it could achieve as high energy density as vanadium redox flow batteries(20 Wh/litre) you would need more than a million cubic metres of aqueous uranium or neptunium solutions of various oxidation states(a cube with the side 100 metres!). Storing a million cubic metres of any kind of harmless liquid under clean conditions is a crushingly expensive proposition in itself, without the complication of the chemical toxicity and the radiophobia.
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February 26th, 2010 at 2:08 am
Sorry, the uranium redox flow battery that I linked to is not based on aqueous solutions, but the neptunium battery is. Then you have the additional complication of the cost of whatever aprotic solvent(doesn’t accept or donate protons) and you use.
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February 26th, 2010 at 2:35 am
Neptunium? But… if you’re making neptunium then you don’t need an big flow battery in the first place…
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February 26th, 2010 at 2:52 am
drbuzz0 said:
There you go, spoiling a good idea with the facts again.
Honestly, some people have no imagination. [/sarcasm]
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February 26th, 2010 at 12:56 pm
Hi. I agree that compressed air is about the worst way to store energy, but it seems a lot of backers of wind power are really pushing for it to become a standard. They want to store compressed air in salt domes, depleted gas fields, aquifers, caverns and such.
I was reading a few things about this and a few problems with safety have already been noted. One is that if you pump air at high pressure some will leak into the ground and there are some who are pointing out that constant pressurization and depressurization of underground spaces could cause a stability problem and this may lead to sinkholes opening up. Each time its pressured there is stress on some underground formations and it could push water away and then when depressurized a sink hole could occur.
The other danger hat has been pointed to is natural gas mixing with air underground. If a gas field is filled with air, even if it was supposedly depleted, a lot of gas can be found in small pockets and if those pockets rupture or there is gas that seeps into the air storage area and mixes with air then it could cause an explosion, if, for example, a rock fracture causes a spark or something. It’s been known to happen with mining when pockets of natural gas seep into the mine. That is why they have air monitors and fans to constantly circulate the air in and out.
Comments? Do these dangers seem credible? I think they could be a concern.
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February 26th, 2010 at 3:13 pm
Rat-Fink said:
They could very well be credible if these schemes were actually done. I could see how sink holes or ground collapse could be a real problem if you pumped air into an aquifer and displaced the water in the process and then released the air faster than the water could fill the void, for example. Obviously if you’re going to pump compressed air into the ground, there will also be letting it out, and if the ground structure is disturbed, there could easily be a subsidence problem.
As for a gas explosion, I don’t know, but I suppose it could happen if enough gas seeped into the area and mixed with air. If the process of compressing air were to fracture some gas pockets and then the air was let back out, then the gas might fill the void and when the area is repressurized with more air, you could get a hazardous fuel/air mixture. Or alternatively, if some of the air seeped into gas pockets, that could be a problem too.
I’m not sure how likely that is though. Mines, manholes and such do occasionally explode if gas seeps in and mixes with air, but there is a fairly narrow ratio that is ignitable.
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February 26th, 2010 at 3:24 pm
I will nitpick here a bit and point out a couple things about gas dynamics:
* Under conditions of high compression and|or low temperature gases definitely do NOT follow the Ideal Gas Law. Instead at a minimum you need to get hold of a Generalized Compressibility Chart and incorporate the Z value in your calculations for P V = Z n R T. Specific tables of thermodynamic properties for the gas to be used would be better.
* The Ideal Gas Law, by itself, is not what gets you. But rather it’s the specific heat ratio, y = Cp / Cv. Specifically if a gas is compressed instantaniously, P V^y == constant; and if it’s compressed with infinite slowness, P V == constant. In practice compression takes place between these two extremes; and during storage heat leaks out of the tank which reduces the pressure in the tank proportionally.
I do agree that pressure-based storage of energy is an inferior method.
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February 26th, 2010 at 4:54 pm
There are actually several problems – ideal gas law is not the only one.
1. Layman explanation of the PV^y bit above from Burya: Even if the gas was ideal, we wouldn’t be able to extract all the energy it contained, because as it approaches ambient pressure, the pressure difference gets lower and only the pressure difference determines how much energy can be extracted. However, if we had an ideal gas we could asymptotically approach 100% efficiency. (Carnot efficiency doesn’t apply because you are not attempting to transform heat into work.) There are other problems though.
2. Ideal gases do not change temperature when they are expanded or contracted. When you decrease the V of an ideal gas, it only responds by a change in p. However, there is no ideal gas. When you compress a real gas, its temperature rises – you bring the molecules closer together, allowing them to interact through van der Waals forces, so some extra energy is released. You get a high-pressure gas that is also hot. As the gas cools when it travels in the pipeline or sits in storage, some energy is lost.
3. When a real gas expands, it cools down. That’s because it has to overcome the intermolecular interactions you increased when you compressed it, and some of the thermal energy is consumed. You get an ambient pressure gas that is cold. That’s why most compressed air storage proposals, like the one in the ridiculous renewables-only article in SciAm, call for heating up the air with a natural gas burner before recovering the energy. (Bonus: if you run the gas in a closed loop with the decompression point inside a thermally insulated box and the compression point outside it, you have… that’s right, a refrigerator. AC works in a similar way.)
4. At high pressures, viscosity of the gas is non-trivial. Lots of energy are lost when pushing the air to the other end of the system.
5. The compressor is not going to be 100% efficient. This takes away a few extra %. It would probably be best to put a mechanical compressor right in the wind turbine, but no industrial scale wind farm works this way.
6. After point 4 the system is (wild guess) about 60-70% efficient if you only have a big storage tank with no pipeline, and the power is low in comparison to the capacity of the tank. However, approaching even that is hard. The best way to do it is to have something that works like a steam engine but the hot steam source is replaced by a compressed air source. Needless to say, such devices are expensive, because they involve extreme precision when machining the cylinder, and there is some friction loss. Small devices are likely to use something like a paddle wheel propelled by a stream of decompressing air. This second method is highly inefficient and gets you down to a few %.
7. Finally, you have to have a HUGE storage tank – so huge that the daily variation in its content is no more than a few % of the pressure. That’s because when the tank is not small, you can no longer ignore the pressure drop inside the storage. Not only the gas that has expanded is cold, the gas still remaining in the tank is also cooling down! You can observe this effect by spraying a can of “compressed air” (it actually contains haloalkanes rather than air). After a few seconds the can gets freezing cold. You don’t lose anything, since you only need to wait for the gas to warm up to ambient temperature to recover the rest of energy, but it limits the power that can be drawn from such system. It also ruins your chances of cheating by trying to keep the gas hot after compression using lots of thermal insulation. Transmission systems where the pressure is kept constant don’t suffer from this effect.
For those reasons, pumped hydro is the cheapest and the only practical large scale energy storage technology so far.
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February 26th, 2010 at 5:24 pm
I read the article closely. I think he’s not a total snake oil seller, and the system has some merit.
He apparently wants to use some existing pipelines as the storage tanks – this is NOT a transmission system, it’s a storage system. This also looks sensible if there’s an unused pipeline in good shape. More importantly the work required to get it working is orders of magnitude small than an underground cavity that is in unknown shape.
Second, he says that “Nitrogen is returned to the pipeline”. If that’s true, then there are actually 2 tanks: a low pressure tank and a high pressure tank. For storage, the gas is pumped from one gas to another. When releasing energy, the gas is released from the high pressure tank (which is now hot) to the low pressure one (which is now cold). This way you don’t lose the temperature gradient that was created during compression – you can use it to get much closer to 100% efficiency than with an open cycle system, as long as the gas temperature doesn’t equalize to ambient between compression and decompression.
Finally the renewable angle seems to be only for positive publicity. He uses a wind-powered compressor to sell this as a green energy source whereas in fact it’s a peaking system. As such it’s the missing piece required for a nuclear-only grid: modern nuclear power plants can load follow fairly quickly (up to 50MW per minute), but don’t have peaking capability, for which natural gas is usually used.
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February 26th, 2010 at 6:12 pm
What sets my teeth a’grinding is that my tax dollars are funding this garbage. As demonstrated here, simple high school physics and a little common sense show it to be highly inefficient. How can anyone with a lick of sense approve funding for this? (rhetorical question – they don’t have a lick of sense)
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February 26th, 2010 at 6:29 pm
leg said:
Actually they’re not funding this one. I mean, they may be funding as ridiculous concepts in the US. In this case, the tax payer money is coming from “Canada Foundation for Sustainable Development Technology Act” – a government subsidy agency for the development of “Sustainable technology.”
So it’s actually Gordon, DV82XL and all their fellow citizens bleeding out on this one. Not that there aren’t plenty of equivalent examples in the US. There’s one guy who has a “company” (website run out of his home) which wants to pave streets with solar cells – yeah, replace asphault with semiconductor strips. He’s getting federal funding to do it.
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February 26th, 2010 at 8:23 pm
Tweenk said:
Ideal gases, don’t have phase transitions, (change in entropy) but they certainly do change temperature in response to changes in PV.
It is true that in reality the atmosphere is not an Ideal gas, but PV=nRT is good enough to explain why the thermodynamics make CASE systems a lose, because the atmosphere (or nitrogen) in the end will preform worse than an Ideal gas. Thus if the system fails with the best theoretical working fluid it could possibly have, it’s not going to get better in the real world.
Burya is right in that other factors kill the system sooner than the Ideal gas law effects do, but that’s not the point. The point is that you can’t win – ever – because the loses will always scale up faster than the capacity.
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February 26th, 2010 at 8:55 pm
The ideal gas laws are not going to make 100% acurate predictions. They come damn close, but the thing is that there’s no such thing as an ideal gas in practice. An ideal gas would be made up of infinitely small particles which have no interactions. It’s damn close though. It’s one of those things where the minor imperfections don’t preclude making a good prediction.
There’s really no such thing as a single point isotropic radiator (All antennas have to take up some space). There’s no such thing as a perfect voltage source (all electricity sources will vary in voltage if you draw enough current off of them) There’s no such thing as a perfect black body radiator.
If anything, this means that in practice, the outcome will be slightly **worse** than the ideal gas laws would predict.
AS for keeping the system effecient by containing heat: yea, some have proposed something like this: it’d be more effecient if the gas were not cooled in any way. Compress it, let it heat up and keep it super-heated. Well… this won’t actually work much. In addition to the imperfect insulation on all the plumbing and storage tanks, the gas is going to get super hot at the time its compressed. Therefore, as more and more gas is compressed, the compression chamber will get hotter and hotter until the compressor melts. You’d end up with even higher pressure and heat and there would be a huge drop in temperature when it’s used still.
That is just not going to work.
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February 27th, 2010 at 12:48 pm
Those uranium/neptunium flow batteries are fascinating.
The actinides have really complex quantum chemistry – really interesting magnetic properties, really interesting potential as catalysts, really interesting potential in batteries, etc, in ways that are even more complex and fascinating than the d-block transition metals.
But where would you get all that neptunium from?
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February 27th, 2010 at 12:49 pm
DV82XL said:
OK, I agree that with the part about an ideal gas not changing T during expansion wasn’t 100% correct, and I used “transition” instead of “process” (sorry, not an English native):
1. When an ideal gas expands, it increases entropy (obvious).
2. During an isothermal process is doesn’t change T (by definition).
3. It can change T during an adiabatic process.
4. Theoretically we can get arbitrarily close to the isothermal process.
5. Therefore the ideal gas law does not limit the total efficiency to less than 100%, but there is a trade-off between efficiency and energy extraction rate. The quicker you try to extract the energy, the more losses there will be.
BTW I also think it won’t work as a power transmission system or as a large scale storage system. I think it might work as a peaking storage system (e.g. store energy for at most 1-2 hours to protect against events like 30 million people turning on their electric teapot simultaneously during a commercial break).
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February 27th, 2010 at 2:33 pm
Tweenk said:
… or millions of people turning their lights back on following “earth hour;”
http://depletedcranium.com/earth-hour-use-as-much-electricity-as-you-possibly-can/
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February 27th, 2010 at 4:15 pm
Tweenk said:
In a perfectly insulated system, if the (ideal) gas is not expected to do work theoretical efficiency can approach 100%
The point however is to provide an understandable explanation, to those who may only have a smattering of high school science why this scheme will never work. To that end the simple issue that heat is lost during compression, and must be supplied during expansion, is sufficient to show that the efficiency of the system is very low.
Compressed air works fine, in some applications it is simply the best way to go. But there are limits that will prevent systems employing this energy carrier to grow above certain dimensions, and that in the end is the crux of the matter.
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February 27th, 2010 at 4:46 pm
I should point out, regarding using a gas to transmit energy, natural gas pipelines operate at a fairly high pressure, but the loss of flow just from the gas traveling in the pipeline is great enough that long distance pipelines require pump stations along their length. These stations use some of the gas to power big turbine pumps to keep it flowing. That’s how lossy it is: Without boost stations the system would not be able to effectively pump gas very far.
Also, despite the high pressure, by the time the gas reaches its destination, the actual amount of energy from the flow is orders of magnitude less than the chemical energy of the gas when burned.
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February 28th, 2010 at 3:02 am
drbuzz0 said:
Well, that really does not make me feel any better! However, I’ve seen so much of this stuff in the US, Canada, Europe, Australia and even Japan, that it seems like the industrial societies of the world are all in a big race to the bottom to see who can lose the most money on these idiotic concepts.
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February 28th, 2010 at 2:19 pm
Gordon said:
Japan seems more rational than the rest. For example their fast reactor program is still operating, and they are continuously developing uranium seawater extraction. The irrationality crown should go to the European Union (which I’m unfortunately a citizen of). It has very restrictive GMO regulation. It has the most anti-nuclear attitude in the world (e.g. in Austria nuclear power is illegal; several countries considered a nuclear phase-out at some point in time; they forced Lithuania to shut down Ignalina as a condition of accession because they were scared of RBMK; similarly they blackmailed Romania into shutting down 4 of 6 units at Kozloduy even though 4 of them were judged safe by IAEA). It pours a lot of money into pointless countryside development projects. Wasteful pseudo-environmental practices like organic farming are popular and even encouraged. The renewable energy scam is stronger than ever. The most tragic development is that as it’s becoming increasingly apparent that renewable energy is a scam, the turn is not towards expansion of nuclear power, which the hordes of brainless anti-nuclear idiots turned into a third rail issue, but towards the planet-killing coal power and untested Rube Goldberg machines like CCS.
It’s ironic that the most rational government at the moment when it comes to energy policy (and several other things) is the Chinese Communist Party. It shows some important weaknesses of democracy.
Back to the article. I think the fact that they mentioned a pipeline is unfortunate. I doubt they are seriously proposing to see this as a transmission system. The quotations from the project leader indicate they’re just reusing an abandoned pipeline as a large storage tank, and the transmission system part was made up by the journalist to make the story sound more interesting.
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February 28th, 2010 at 2:29 pm
Tweenk said:
I try not to get too much into the whole national-centrism thing and always point out that all countries have their own brand of stupid. However, in the case of GMO food in Europe, I find it just about comical, coming from an American perspective.
The whole anti-GMO thing in the US is not as strong as in Europe (it exists, but not as much), I think in part that’s because the cat is out of the bag here. The first genetically engineered crops were introduced in the US in the late 1980’s and early 1990’s and basically became ubiquitous within a few years. There’s little point in protesting it at this point. The genie can’t be put back in the bottle and everyone here has been eating it for many years with no ill effects.
For that reason, I think it’s a bit ridiculous seeing these blockades of GM crops at ports or lobbying for bans on it in Europe. I’m sitting here eating food which probably contains gmo crops and I’ve done so for many years.
It’s so annoying hearing this BS about how GM crops are the reason for the American obesity and diabeties problems. No, they have the same caloric and nutritional values in general. The reason everyone is so fat is because more and more people prefer to eat an oversized fried burger and milkshake at a fast food place for dinner instead of making something healthier.
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March 2nd, 2010 at 7:54 am
Tweenk said:
A while ago I read an article about such a pressurized air peak storage system. They had refined the idea and used a special two-part gas turbine instead of just a pressure engine for electricity generation. If they had pressurized air in storage, they would shut down the compressor part of the turbine – if not, they could still run it as a regular peak-power gas turbine but at a lower power rating because they had to couple in the compressor. During nighttime, the compressor would run alone on electrical power to fill the reservoir.
They also stored heat in a liquid medium to warm up the cold, expanding air coming up from the reservoir.
Of course, energy storage is always at a big loss, but there are only so many places you can build a pumped storage plant.
Satan_Klaus
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March 5th, 2010 at 5:04 pm
Tweenk said:
Yeah, I think The West has been in decline since the early 1970’s. I put the symbolic peak at the moon landings, say 1969. With a few exceptions, things have been pretty much downhill since then. People seem to be less well educated, in the sense that they don’t really understand how the world works. And, they’re less motivated, more willing to strive for the minimum. Democracy can be a great system, but it has morphed into the notion that 100 million people can’t be wrong. We are doomed…
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May 9th, 2011 at 9:04 am
Hello all,
Apologies for reviving a dead body – I was researching the feasibility to marry a domestic wind turbine with a pressurized pneumatic/hydraulic hybryd system, for decoupling energy generation/storage and actual usage at home (wind patterns versus power usage patterns at home), and found this very interesting site/discussion. I have some suggestions/questions that might put this into possibly slightly different light (well maybe not the original idea, which I consider a “pipe” (sic!) dream myself
, but domestic-size hybrid system):
. Obviously though, one would need both the accumulator and the fluid storage tanks scaled appropriately to the energy consumption needs, so I don’t see it happening in the original idea discussed here, for practical reasons 
1. Why hydraulic/pneumatic hybrid? From what I’ve learnt doing my research, hydraulic motors/pumps efficiency is way better than pneumatics. But then, coupling hydraulic fluid after the compressor with hydraulic accumulator, seems to me is 1:1 conversion in pressure, I can’t see where loses could come from apart from compression heat loses. Just different way of pumped hydro, one might say, possibly feasible on a domestic scale – where water head pressure is replaced by pneumatic pressure
2. Someone mentioned refrigerator above – a heat pump, in general (I personally think that line of thought should be reinforced and pursued whenever possible). Going back to the discussion – well, one need to be extra careful when providing any definitive efficiency figures for the system as a whole, traditionally ruling out the potential to tap on the heat of environment, and IMHO many (if not all) systems that involve pneumatic pressure transformations, could potentially benefit from that concept, a stationary system in particular (air car, dismissed briefly above as well, is worth at least brief Wikipedia research, regarding overall system efficiencies, engine concepts and how it taps on the heat of the environment – person(s) who dismissed it above certainly didn’t do that part of their homework
– no offence meant, but check for yourself, it is worth it, it actually is quite clever idea). Depending on design and use case, but heat pumps potential, in yet more ingenious and maybe yet to be invented designs, is IMHO enormous… So one need to be very careful, again, dismissing compressed air as a storage medium, as it is a well established practical fact, that overall COP of commercially available heat pumps is in the range of 300%-400%, and let’s do not forget that traditional phase-changing process and supersonic expansion valve in mainstream heat pumps are hardly very high-efficient things!
Is it possible to scale enough to be feasible for grid applications – I don’t know, but if we are not ruling that factor a’priori out of the equation, we could end up with very interesting overall efficiency figures indeed
. Again, I am not a trained engineer, only a fellow that liked and kinda understood basic physics up until high school (my high-school class was profiled for mathematics/physics), when my fascinating encounter with physics ended (went into software side of things, sometimes I really regret this 
).
What do you think about it, does it possibly shed some new light/sparks new ideas in your educated minds? Any criticism welcomed, though I will not be able to argue based on equations and tables and specific figures, and would rather welcome higher level/layman terms discussion, kindly. Basically, is there anything that stops us from (let’s say as a figure of thought) to introduce heat pump BEFORE the compressor to cool down the air being compressed (so effectively we would be putting more gas/energy into the storage tank), and another to heat up the air from the tank BEFORE it “hits the road” (does our usable work)?
Best Regards
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September 2nd, 2011 at 6:24 am
Atmospheric air contains 78.09% nitrogen, the gas is slightly lighter than air and slightly soluble in water.
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September 2nd, 2011 at 12:27 pm
Yes, but why do we need some stupid spammer who doesn’t understand rel=nofollow to tell us that?
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