I’m a proponent of alternate energy sources, mostly to get us disengaged from Middle East Oil. Often there are schemes floated to produce alternate energy that just don’t balance out when you sum up the energy in versus energy out. Most corn based biofuel processes fall under that category now, so does nuclear fusion, but that may change someday.
So when something dropped in my inbox today called “cold energy” I was immediately skeptical, because it made me think of “cold fusion”, which was a hoax. This one however may be different and it’s concept is simplicity itself.
It’s another form of wind power, but this one has to do with high and low pressure systems on a synoptic scale. Basically the idea is to build open ended pipes between areas that often have strong pressure gradients, such as the Midwest. This map below gives you and idea of how High and Low pressure centers are often separated in the USA.
The pressure difference between the two pressure systems would push air down the pipe, and drive a turbine. The turbine would have reversible pitch blades to capture airflow no matter which direction the High to Low pressure gradient was.
A company called Cold Energy LLC is proposing building just such a system. The hold a patent on the concept, and call it Atmospheric Cold Megawatts (ACM). Here is some descriptive text from their website:
Utilizing a revolutionary new process, the ACM technology is capable of generating power at the scale of coal and hydro plants with virtually no environmental externalities. By leveraging the differences in atmospheric pressure at geographically separated locations, wind speeds approaching sonic levels can be generated within ACM pipelines. This energy may then be converted to a variety of desired forms using existing technology.
No fuel is required or consumed to produce the power. No pollutants are introduced into the atmosphere as the result of the generation process. The cost per KWh is a fraction of traditional (and alternative) generation methods. Because there are few moving parts, maintenance costs are minimal and the projected lifespan of installations is considerably longer than any other generation method.
They claim they can produce power at a cost of .03 to 1 cents per kilowatt/hour. Of course the advantages are huge, with there being no environmental impact other than long pipes either above or below ground. Here is how they say it would work out:
ACM is a system for the generation of energy based upon differences in the atmospheric pressure at geographically spaced sites, and comprises at least one long conduit – in the order of many miles long. In operation, the air flow in the conduit will accelerate to a high velocity wind without the consumption of any materials and without the use of any mechanical moving parts. A power converter, such as a wind turbine, in the conduit converts the high wind velocity generated by even small pressure differences into energy of any desired type.
The opposite open ends of the conduit are located at geographically spaced sites, selected on the basis of historical information indicating a useful difference in barometric pressure. A plurality of conduits, each having open ends in different geographically spaced sites, may be interconnected to maximize the existing pressure differences, and will produce higher and more consistent levels of energy production. The ACM conduit configuration of the invention can transform even barometric pressure differences in the order of one tenth pound per square inch into wind velocities in the sonic range.
I think its totally tubular. 😉 But will it work?
UPDATE: It’s a pipe dream, see reader comments, particularly Brendans.
This look promising
Just a couple of questions:
How will the wind accelerate?
How will the resistance in such long pipes be overcome?
How do they stop the air from taking the way of the least resistance (open air) and to choose the way of more resistance (the pipes)?
Why is this principle not used in gas-pipes, why need gas-pipes pumping stations to keep the gas flowing?
I may be a bit out of my depth but I would guess that the pressure differential would drop across the entire length of the pipe and the difference at a particular point (where a turbine might be located) would be negligible.
There aint no such thing as a free lunch.
Do the calculations to determine how much energy it takes to move any fluid through a long tube. This is the same limitation the sea water temperature difference promoters ran into when they tried to build a practical system. The frictional losses are significant, to say the least.
Here is a simple thought experiment: How much horsepower does it take to get sonic wind speeds in the short length of a wind tunnel?
Wow, that does sound cool.
Would be great to see some small-scale experiments. I would think something could be setup with a pressure tank and room pressure for proof of concept.
Instead of large pipes that are hundreds of miles long and require covering or disturbing vast tracts of land, how about a series of very large poles to which large blades and an energy converter are affixed? They could be placed in remote or very windy areas where pressure differentials are irrelevant.
Oh, wait, I think someone may have already tried that successfully. Of course, the energy produced doesn’t really cover the cost of building and maintaining those… shall we call them windmills… but they have worked for centuries for various applications.
Another idea that has also worked are generators using tidal/wave power. Some think that you can generate electricity from solar power as well.
The point is, the wind is free, the waves are free, and the sun is free, so why not use those free lunches, too? “Watt’s up with that?”
Assuming a 10 meter (diameter) pipe and a 30 mph windspeed through the pipe the theoretical power available would be about 115.5 kw.
Power varies with the cube of speed and square of the pipe diameter.
Subtract from that the inefficiency of the turbine/generator and considerable friction losses from moving the air through a very long pipe.
I would think it would be testable with a length of a natural gas pipeline that already exists. Run it during summer when usage is low. I’m leaning toward frictional loses being the spoiler.
No experiments are necessary. This is a simple bernoulli problem. Not wanting to take a whole lot of time (and then spending way too much time), I used an online calculator. I assumed incompressible fluid and a steel pipe. Forget the 1 m pipe diameter, I used 10 to minimize pressure drops (the 1 m pipe diameter would get you about 7 km…). Try it yourself. I used the calculator at
http://www.efunda.com/formulae/fluids/calc_pipe_friction.cfm#calc
(Beware, you only have a few opportunities to use it before they want you to sign up) My inputs are 102.4 kPa, velocity, 2 m/s, D 10 m, pipe roughness, 0.0005 m/m, pipe length ~ 675 km, no elevation gain, fluid density 1.2 kg/m^3 and fluid viscosity 0.0182 cP. Your output is 99.6 kPa… If your pressure at point b is less than 99.6, you have a physics problem of trying to get water to flow uphill. This isn’t exact – I should have iterated around the mass flow rate, or changed the pipe diameter (I got the approximate intial velocity from the simple form of Bernoulli – for air it will change as you add pressure drop and changes in property along the line), but its good enough to show that you won’t get hardly any movement. I used your map, and found the great circle distance between austin, tx/kansas city, mo and chicago. 675 km is somewhere in between. Now try to put a turbine to get useful work out of it. Forget it. Anthony – feel free to email me about things like this if you have questions in the future…
Thanks Brendan. That’s why I made the title “Pipe Dream or Viable Energy”. This had a flavor on par with a perpetual motion machine.
No free lunch here, I wonder how they got this one past the patent office?
Anthony –
I forgot to mention. I love your site and what you are doing… I keep meaning to try to check out the Livermore site for you, but don’t have a good gps and haven’t found someone to borrow a good one from yet. Keep up the good work!
Brendan beat me to it. I started doing the calcs
One can patent practically anything in this country. The folks at the USPTO don’t check to see if the device works, their only concern is if it violates an existing patent. You could patent custom-fit left nostril inhalers if you wanted (unless someone already has).
Regarding ocean thermal gradient systems: I remember reading (in an article by Jerry Pournelle about 25 years ago) about a prototype that generated a few hundred kilowatts off Puerto Rico about 80 years ago. The problem they had was corrosion, not friction losses.
Correction to previous:
It was 1930, off Cuba.
Plant was destroyed in a tropical storm.
Addition to the correction:
22 kilowatt gross output.
http://www.cogeneration.net/ocean_thermal_energy_conversion.htm
Sheesh!
Too many years; not enough coffee!
I think about it like this. There is an even greater pressure gradient between air two miles straight up and at sea level, so we just make a tower tube with intake nozzles at the ground floor, and the air should rush in at sonic speed then spill out of the top in the rarified upper atmosphere.
Except for gravity.
What about a solar chimney would it work? I first saw it in a SF book but seems like the idea would work.
the start of chapter 2
Carnifex-ARC by Tom Kratman – Baen Books – Chapter 2
A solar chimney dominated the island’s skyline, rising several hundred meters above its highest elevation, the otherwise unnamed Hill 287. From the base of that chimney, a thick tube of reinforced concrete, ran an extension northward, toward the equator, along the side of the hill. This ended at one of the three largest greenhouses on the planet, the other two also being the foundations for solar chimneys. Fixed mirrors, sighted to reflect the maximum amount of sunlight into the greenhouse with the least expense and for the least effort, sparkled on the hillside.
The greenhouse contained air heated by the local sun. The air escaped along the tube that ran along the ground and up the hill before making its final exit at the top of the chimney. Along the way, the wind thus created turned turbines that produced the electricity needed for the island’s twenty-one thousand legionary personnel and their families plus those of the thirteen thousand legionaries deployed to the war. Intended, eventually, to provide electricity almost twice that many, the chimney operated at less than half capacity.
Cold fusion wasn’t a hoax. The Fleischmann/Pons experiment has been replicated hundreds of times. Whether there is a viable energy source there is anyone’s guess, but the possibility that there might be sent the crowd for whom cheap, plentiful, pollution and CO2 free energy would be a disaster into denial overdrive.
They are trying to get a chimney going in austrailia but the cost of the structure makes its prospects grim.
They have a solar tower/solar chimney in Spain already:
I am reminded of my youth in the Los Angeles basin plagued by smog–blamed at different times on the back-yard incinerators (which turned out to have been a source of life-saving activated charcoal, some said; the butadiene and other refineries, the Fontana steel mill, ….
Among the solutions offered were tunnels through the mountains or fans atop them to blow the crude into the desert.
Must have worked, it seems to be smog all the way across some days.
Rube Goldberg would be proud.
And as for America’s “dependence” on Arab oil, it is the dammed environmentalists keeping on us that path by blocking ANWR oil .
Well how do you like that?
Free lunch is back in play fellas.
So the Spanish heat tower proves the theory, now lets refine it a bit and adapt it to the modern world.
As Anthony has been steadily pointing out, NOAA and GISS are mostly measuring urban heat islands. We don’t need a fancy collection grid to heat the city air for a contraption such as this if it is set in an urban area.
Suppose instead of just an ac/heating plelum, elevators, electrical bus, and plumbing;that all skyscrapers included their own heat tower as a core. All it needs is an unobstructed intake. Say maybe the floor just above the parking.
They did this experiment on TV the other day in Japan where they attached a vacuum cleaner on one end of a long hose and suck a tissue paper. The goal was to find out at what length the suction of the vacuum cleaner loose out to friction. They also had three college professors theorize the limit via calculation.
The estimate by the college professors were anywhere from 80m to about 900m.
The result. At 2km they ran out of hose and the vacuum cleaner was still able to pull the tissue through the hose. The only “problem” was that longer the hose, longer it was taking for the suction to build up enough to make the draw on the tissue. At 2Km I believe it took almost a minute before sufficient pull was generated to suck in the tissue.
From looking at this experiment, I think the biggest problem for this scheme would be the duration of time before sufficient pressure difference is built up and time it takes to create sufficient pull. It may take hours at the distance we are looking at…. By which time, the difference pressure may have reversed itself. Not a very reliable generator of power.
The last question isn’t one about Bernoulli – its a matter of seal and your pump. If you have perfect seal, a pump will be able to create a “vacuum” on just about anything – minus the efficiency of the pump. (There are different levels of seals on pumps as well, and pumps reach a point where the removed gas is equal to the amount of gas that slips back in – real vacuum pumps for lab environments are very expensive, because of the engineering…) The professors probably tried to use Bernoulli’s eqn, but its the wrong application for this environment.
The thermal tower may work – but its likely a matter of economics. There are lots of energy systems that one can build, but if they can’t meet marginal rate of return, then forget it. AS an example, wave based power systems (mentioned above) could possibly work in some of the more intense wave environments, but here its a matter of economics and durability – building something that meets the required roi and survives 20-40 years in one of the most brutal environments on the planet (the wild ocean) is pretty daunting. Check out http://www.oceanpd.com that has probably the best of these systems. Great for Europe, somewhat good in environments North of SF Bay and North of MA – there’s not enough wave action in the summer months when demand is high to justify (at current prices) a system like this south of those points…