Thanks for looking at it in more detail.
And to get it, you are building a huge, unnecessary structure. How long will it take to recoup the energy invested in building it?
At Chena, Alaska they installed
2 Carrier/UTC ORC's with a medium grade geothermal source.
I have talked to the project manager several times, and my major question was why they wouldn't air cool rather than use surface water when they have -10C to -50C ambient air for most of the year. The second unit went in with forced air cooling using a standard
forced air condenser:
Gwen, the project manager says that it draws 24kW, but the performance of the second air cooled unit is much better than the first water cooled ORC.
24kW is a fairly substantial constant draw in this size of plant. They cannot use an evaporative cooling tower due to the sub-zero temperatures, but if they built a convection cooling tower, even if they partially forced air, it has to be a performance improvement. In this case, they have diesel generators as the main power source, so any power saving is based on diesel cost.
A
large scale natural draft example.
In this case they are fairly small scale, but a galvanized steel or concrete chimney isn't a large expense to save the 24kW at the fans. A large steel grain bin without the roof would work.
A chimney like this would have added $20-40k to the project, but at $0.25/kW for diesel power, the $6/hour the fans are costing them would recover that in ~200 days.
Irrational fear of technology is never a good thing. Right now its either nuclear or fossil fuel, and we're poisoning ourselves by choosing the latter. See
this thread for more.
That is why I am attempting to design a location independent clean power system. I'm not that irrational, I read through the
Chernobyl assessments and I work at a
Crown Corporation just like
AECL and have worked at 2 other Crowns. My department does high availability redundant databases and systems and although we are usually past 5-9's (99.99999) uptime, bad things happen. Saying that nuclear accidents never happen or that there aren't waste disposal problems is irrational. Accidents are very rare but a "big deal" when they do happen is a rational statement.
Ideas can be patented without proving practicality. A patent is not a valid source for such information. No spray-downdraft tower has ever been built, so it is simply unproven theory at this point.
The water spray idea has some fundamental problems. It depends on having a large water supply in an arid region (which is an oxymoron without massive construction) and water vapor is less dense than air, so cooling air by evaporating water creates cool 100% relative humidity air, which is much less dense than dry air at the same temperature.
I already told you why free-fall is a bad estimation. Drag is an extremely significant force in the acceleration of falling masses when the fluids involved have similar densities. Try filling a balloon with air and dropping it. The balloon is slightly more dense than the ambient air because of the material in the balloon itself. When you drop it, it will not fall with an acceleration anywhere near 9.8m/s^2. Instead, it will slowly drift to the floor.
I don't know your location, but my personal experience with relatively short updraft chimneys in -20C ambient air tells me that expecting a 20m/s airflow in a 100m chimney isn't unreasonable. There are a lot of variables and it needs prototyping.
What is the problem with forced convection? You seem intent on removing some pumps or fans from the system, and to do so you have incorporated a complex and expensive system (which requires pumping power itself) that will not do the job as well.
The pressurized anhydrous ammonia doesn't require pumping up the tower. The aqueous ammonia is pumped to pressure, but the solar regenerator provides the anhydrous ammonia pressure.
There is a reason free circulation is never used to drive coolants in power plants -- because free circulation provides extremely poor heat transfer coefficients. Forced convection heat transfer coefficients are typically one or two orders of magnitude higher than free convection ones. That means you get 10-100 times as much heat transfer for the same temperatures.
I don't know what you mean. As far a air, natural convection cooling towers are common in large systems. I don't have anything in the design with natural flow of thermal fluids.
I do not have the time to do so, and I would have to research gas/gas flows (I specialize in two-phase flows).
Thanks for the time you spent looking at it now.
You don't need to see the exact equations, however, to understand that the assumptions you make in this regard are faulty.
Fear mongering at it's finest. The idea that the US is going to come after Canada for oil is absurd.
NAFTA guarantees Canadian exports into the U.S. and Canada will do it's best to meet the agreements. When we run out, we run out.
It's not apparent in oil yet like it is with gas (I used to work for the main Gas Transport company here), but the U.S. imports 15% of it's natural gas from Canada, but it is 50% of our natural gas production. The current natural gas shortages in the northern U.S. are more due to lack of storage and transport, but when we cannot meet domestic demand, something has to give. This isn't unreasonable or absurd. It will happen much sooner with natural gas than oil, but when it comes down to who is freezing in the dark, people will start fighting. You are applying the last 60 years of relative peace that is based on cheap energy to a situation that will have different parameters. GWB and crew have publicly stated to expect war for the rest of our lives, not me. We probably won't see Canada run short of gas/oil in my lifetime, but I have 3 kids.
You implied that a good blacksmith and stonemason could build a 100 meter tall, 20 meter wide hourglass shaped free-standing structure complete with power plant, solar arrays, and massive underground heat storage system. I say they couldn't. Simply naming two large scale, government/church managed projects does not refute my claim.
I'm in I.T. now, but I owned a construction company and my family has run heavy equipment for generations. One of my aquaintances ran a basement forming/concrete business and they used to build grain silos like this:
Usually a 4 man crew. It's not rocket science, you setup the forms and steel, pour, set and repeat. For an hourglass shape, you need to change forms, that's it.
I still think the idea is silly. It is an overly complex system whose design is based on basic calculations and overly simplistic assumptions.
The largest solar plant in the world, the trough collector
CSP at Kramer Junction
has a system like this:
This classic CSP/SEGS design is nothing more than taking a standard traditional fueled steam power plant and changing the heat source. There was no real re-thinking of the system, they have just changed the heat source and built a steam power plant.
I am proposing that by building a
solar chiller with the same trough collection system and using a natural flow convection tower. I believe with some thought in the system you can get close to a 1:1 heat transfer from the ambient air if that heat is moved to a colder location and double the thermal output of the plant.
This design isn't much more complex:
The proposed system is not overly complex, it's a solar chiller and a chimney with a few turbines. A block diagram of my house plumbing is much more complex than this system.
For every concept that succeeds, there are thousands that fail because they are not practical. Engineers do more than just enhance technology, they make it useful. They are the ones who can tell you if the idea will work in the real world like it says it will on paper. This engineer is telling you that this idea won't.
OK. I have 20+ years of practical system design experience and have been working on this for several months. There are hundreds of details to work out, but I think that the basic idea of using a solar chiller to transfer additional heat from the air and utilizing pressurized ammonia and thermal storage for reliability is a fundamental performance enhancement to already feasible SEGS/CSP systems.
--
Any gains from using free circulation instead of forced will likely be lost in the need for larger, more powerful pumps to push the Ammonia around the heat exchanger.
I don't understand this part. I assumed that if you expanded liquid ammonia at the top of the tower that it would evaporate, continue to expand and descend through the heat exchanger without additional force. The liquid ammonia would be at 200psi at the top expansion valve and as soon at it starts boiling it will continue to expand. My understanding is that this constant expansion in the heat exchanger will push the ammonia vapour through the coils, especially downhill.
Not only is water going to condense, but it is going to freeze.
I thought about the freezing issue a lot. The classic A-coil does pretty well with not freezing. I thought that possibly a toggling system to allow portions of the coils to defrost would work. It's a difficult problem.
I didn't want to put either orientating the intake/output with prevailing winds or a vortex airflow into the simplified drawings, but my mental picture is to have the intake orientated to the wind, build the heat exchangers to align the airflow into a vortex to increase the angle of attack at the wind turbine and then exhaust with the prevailing wind. I am having difficulty incorporating that idea with capturing the condensation, but my mental image is having a descending spiral heat exchanger design with the transfer fins angling the air into a vortex.
I didn't re-quote everything you wrote regarding heat transfer, but I will spend time reading and trying to understand it. Thanks for putting that effort in.
Also, it should be pointed out that it will snow inside the tower. This is not a good thing from an analytical point of view (it moves energy around), from a design point of view (what will you do with the snow), and from a maintenance point of view.
In my visualization, I would think that the cooling/condensation system would want to keep the condensate above freezing. The condensed water at the tower top has high value. I probably should have used a +1C target air temperature in the calculations. I would imagine snow in a 20m/s wind stream would exhaust and not build up anywhere. In my mind, the bigger issue is ice buildup prevention.
Next, I'm interested to see how the plant will react to variations in conditions. All your calculations seem to work with averages and typical values. When the temperature and other weather conditions undergo minor changes, it will affect the system significantly. What will you do to smooth out energy transfers and power outputs that undergo variations with changing conditions?
It would be a more economic system to have very controlled conditions and alternators, but D.C. generators/inverters as in regular wind turbines would work if it's too difficult to build the control systems. Regardless of the variations, the system should be much more stable than natural wind. I would think that controlling the ammonia flow based on ambient temperature wouldn't be that difficult of an algorithm.
When there are large changes in conditions (specifically when there is a day/night change), how long will it take for the tower to react? You cannot simply flick a switch and expect the flow in the tower to reverse. The cold heat exchanger is going to stay cold for a long time after it is disengaged. The hot heat exchanger is going to stay hot for a long time after it is disengaged. In cases where you want to switch from downflow to upflow (or vice versa), you have to deal with reversing the flow of 3000 m^3/s of air. That is not going to be a picnic.
I was thinking of a mechanism in the wind turbine similar to a helicopter with variable pitch blades. In a location with day/night cycling the pitch could be flattened to idle, the heat exchangers swapped and then the pitch reversed without losing all of the rotational velocity in the turbine.
Thanks again for all of your time on this, this is great input. I would like to put a line of credit for your input on the
project news/updates page, please email me what you want for your info on the page, or I can just use pvt1863 and reference this thread.
