This topic contains 100 replies, has 9 voices, and was last updated by Avatar Brian H 9 years, 11 months ago.

Viewing 15 posts - 16 through 30 (of 101 total)
  • Author
    Posts
  • #3722
    Avatar
    Aeronaut
    Member

    You lost me there, Jimmy, I don’t know either of those words. My formal training is as an electronics technician, and I’m self-taught in thermodynamics, mechanical engineering, and machine shop. Lots for me to learn.

    17M BTU/hr is too much energy to be tossed out the window, and if thermodynamics works like electricity, we’re allowed to max one variable while reducing another, like transformers do with voltage and current.

    #3723
    Avatar
    Rematog
    Member

    And, there is a vast difference between a what, 25,000 hp machine with 3 stages and a 21 stage, reheat, 750,000 Hp machine. I would assume even these small, relatively low pressure turbines had a main steam temperature of around 800 or 900 F.

    One of my points that your last post ignored is that, if this boards estimates are anywhere near correct, then a turbine, with it’s necessary appurtenances such as a condenser, feedwater systems, boiler feed pumps, etc. cost MORE then a FF module to generate the same power. I.E. it is cheaper to buy another FF module(s) to generate the power then to buy the equipment needed to use waster heat to generate the same amount of power.

    As to the case of power DISTRIBUTION reliability, that has nothing to do with the TRANSMISSION grid. These are different things. Transmission goes from power plants to sub-stations (transformer yards in your area) DISTRIBUTION is the local lines that get the power from the substation to your home or business. You didn’t mention if those few hours involved a storm or not. If so, during those few hours, people were out in the rain, dark, etc. working to restore downed lines so that that vital power could be restored in only a few hours. So even if FF is highly distributed to the local Substation level, DISTRIBUTION reliability will be the responsibility of the local utility. Unless of course you can afford your own million dollar power plant (I.E. one FF module, installed).

    By the way, it takes less Btu/lb to heat steam to any given temperature at a higher pressure (water is weird stuff). I am assuming a constant feedwater inlet temperature. That is because the amount of superheat in the steam is greater at a lower pressure. Just look it up, enthalpy of 1000F, 2400 psig steam is 1460 Btu/lb, but for 1000F, 1200 psig steam, enthalpy is 1499 Btu/lb…..hmmm… I’ll grant, at a more likely steam condition for your ship, say 800F, the 1200 psig steam’s enthalpy is slightly lower, 1378 Btu/lb, but it can also do less work in the turbine.

    That is why utility power plants have such high pressures, efficiency. 2400 psi is now the low end. 3000 psig is not uncommon, and 3600 psig and more are being considered for supercritical, once thru boilers. ‘Course, we won’t build any more due to the Global Warming issue. But boy, is China building them faster then we ever did…..hmmm….

    #3724
    Avatar
    Rematog
    Member

    No, Jimmy, it does not work the same way as electricity. If you reduce the pressue, it gets colder, not hotter. Just think about what happens with compressed air when you drop it’s pressure… it gets cold.

    With steam, you really need to look the conditions up in a steam table.

    Enthalpy is the measue of the energy in a fluid at a given temperature, pressure and state (liquid, gas or solid). It’s given (in US units) in Btu/lb

    Entropy is a measure of the “randomness” of the fluid, or it’s state of “organization”. It’s units are, like the concept itself, confusing, Btu/lb F.

    You just need to understand that it is very important at what temperature the thermal energy is. That defines how practical it is to run a heat engine (like a steam power plant), using that heat energy. It’s the “potential” difference between the high temperature and the low temperature (condenser cooling water) your machine runs the heat energy thru that controls it’s effiency and the cost the equipment needed.

    #3725
    Avatar
    Aeronaut
    Member

    I stand both enlightened and confused, Rematog. I had no idea we were talking that much pressure or that many stages. Something else that’s adding to my confusion is the apparent very high temperatures (degrees C, K, electron volts, etc.) at or barely off the electrodes that must be removed.

    One of the reasons I keep hammering away at this is that engineering this “waste” heat into existing infrastructure could make our 5MW plant marketable as a 7 to 9 MW, greener than grass plant thats in step with the times.

    Another, even more important reason is that for every high profile idea there is some jerk(s) who will grab headlines by attacking it. That is why I believe we better build an efficient system. Imagine trying to sell the world the concept of millions of these little power plants, each throwing off more heat per hour than I can really wrap my head around.

    In the marketing world, perceptions are more important than facts, and that many new BTUs is screaming to be labeled as the Polar Blowtorch that’s going to submerge half the world.

    The only parts that I don’t believe we’ve really touched on are the temperature of the formerly cryogenic helium transferring 17M BTU/hr into our feed water, along with the size and energy requirements of helium cooling loop.

    I’d like to see FF locomotives as well as ships. Seems that getting it to work in a utility setting would be the first size/mass/net output hurdle.

    #3726

    Rematog wrote:

    With steam, you really need to look the conditions up in a steam table.

    Enthalpy is the measue of the energy in a fluid at a given temperature, pressure and state (liquid, gas or solid). It’s given (in US units) in Btu/lb

    Entropy is a measure of the “randomness” of the fluid, or it’s state of “organization”. It’s units are, like the concept itself, confusing, Btu/lb F.

    Well, I am learning something. And here, for those of you who are interested, is a link to a steam table. Who knew?

    http://www.engineeringtoolbox.com/saturated-steam-properties-d_101.html

    #3727
    Avatar
    Aeronaut
    Member

    That’s a goldmine, Admin. Now it’s down to temperatures, pressures, and flow rates expected for both loops of the heat exchanger. (I’m from Missouri). I just printed the steam tables and thermodynamics, but I can see a lack of information coming up fast.

    Rematog, how are your plants fueled, and what temperature is the flame? Thanx.

    #3728
    Avatar
    Rematog
    Member

    We burn coal. In the past, oil and natural gas were burned, but today those fuels are not normally burned in utility sized boilers (too expensive, now only used in gas turbine and combined cycle plants). The furnace operates with a flame temperature of between 2000 and 3000 F at the burner, but this cools rapidly and by the time the gas exits the boiler, it is down to below about 1200 F.

    The article on boilers in wikipeda is poorly done. The one titled “Fossil fuel power plants” is much better. There is some information on the B&W;site, babcock.com

    If you want a very good guide book, I highly recommend “Steam – It’s generation and use” published by Babcock & Wilcox. This tome is about the size of a phone book and is in it’s 41th edition. It will not be easy to find in a library, you would likely have to request it from an inter-library loan. I just checked, and it is for sale on Amazon, but is expensive (used copies being sold for $140 and up. It is not sold new, but only given away to customers by B&W;.

    By the way, I don’t work for B&W;, never did. They are one of the “Big 2” boiler manufacturers in US, and so have put out a lot of info on the subject. Our plant has one B&W;boiler and two Riley boilers. Riley was a smaller company and is now under a different name. The other “Big 2” company was Combustion Engineering. CE is was also sold off, to ABB, and is now a subsiderary of that company.

    Enjoy

    Rematog

    #3729
    Avatar
    Aeronaut
    Member

    Thanx for the info, Rematog. B&W;built the 1200# / 30,000 SHP plant (circa ~1960) that I’ve been using as a steam to torque model. Actually, the ship was commissioned in ’63 with a 600# plant and was being upgraded to 1200 when I got there in ’76.

    So FF just might work in a steam turbine, depending on the heat exchanger’s input temperature and transfer efficiency. I was going through some notes earlier today and was reminded of the distinction between combustion turbines and steam turbines. I also read a thread yesterday on a flameless turbo/ramjet engine. Do you think that might be applicable to the utilities industry?

    #3730
    Avatar
    Rematog
    Member

    I think Eric will confirm that the FF modules cooling needs (the controlling factor) will require that the exit temperature from the FF module be way below any practical power generation input temp for a a steam cycle.

    And, as mentioned before, the cost of the steam cycle equipment is projected, by this board, to be lower then the cost per unit of capacity (normally given in terms of $/kw capacity) of a steam generator/turbine/feedwater system. So why do it? Note, power companies don’t tend to spend 10’s or 100’s of millions of dollars just be be “Politically Correct” with regards to equipment selection. And that IS what a large steam turbine system costs to install.

    Gas turbines are used for quick start and peaking applications (peaking is the high load experience for short durations, such as a hot summer afternoon). An exteral air heater is technically possible. But again, no suitable high temp energy source is available, and an this would again, based on my industry experience, be more expensive, in $/kw installed, than the boards estimate of FF modules.

    Rematog

    #3731
    Avatar
    Aeronaut
    Member

    No, they certainly won’t buy until it makes rock-solid business sense. Something that just dawned on me- are you saying that the cryogenic helium chiller is going to absorb over 70% of the excess heat, and that that’s why the temperature’s too low to run your turbines?

    #3732
    Avatar
    JimmyT
    Participant

    This isn’t going to be cryogenic helium. The temperature at which it enters the focus fusion device is probably going to be 250 to 300 Degrees Fahrenheit or so. It’s exit temperature will probably be on the order of 800 to 900 Fahrenheit degrees. So the entire operating temperature range is going to be way above what could be could be considered cryogenic.

    One unusual thing about helium (and hydrogen) is they are already above their Boyle temperatures even at room temperature. So they do not undergo Jule Thompson cooling even at room temperature. In fact they become hotter when expanded adiabatically. So any cooling must be strictly by heat transfer.

    If any of these terms are unfamiliar to you. I can explain them.

    #3733
    Avatar
    Henning
    Participant

    I’m actually wondering why gaseous substances are used as they have a bad thermal conductivity (or actually heat capacity) per volume. I see that Hydrogen and Helium are advantageous because of their low Z (protons) so they don’t absorb the x-rays as the cooling cycles have to run through the photovoltaic layers. But maybe the cooling of the outer layers should be done by a liquid beryllium-hydrogen or boron-hydrogen compound to get more heat transferred. Or are they too corrosive? Maybe resort then to liquid carbon-hydrogen.

    #3734
    Avatar
    Henning
    Participant

    Ok, I kind of gotten it. Turbines go with steam of much higher temperatures as it is an widespread and tested technique. I’m just worried about the pressure the photovoltaic elements have to withstand, as they are just layers of foils which have to maintain vacuum on one side whilst running high pressures through them. Maybe do the plumbing with beryllium?

    #3735
    Avatar
    Aeronaut
    Member

    Thanx for helping me narrow the gap, Jimmy.

    I just reread page 1, so now I see why Rematog insists it won’t run his turbines. The only way I can see that temperature range carrying off 17M BTU/hr is one heckuva high velocity gas flow.

    So let’s turn this thing around, since utes are likely early adopters in relatively small numbers. In small numbers, these “producing prototypes” could dump the excess heat without a public backlash, since they will be perceived as big boys’ toys.

    What would happen if we used the 5MW to electrically heat the boilers, perhaps using induction heating? I’d like to see at least 50MW usable output rating, but even 10MW is 2:1 leverage, while eliminating all of the fuel hassles.

    Now your ROI is how long it takes you to burn ~2M$ of coal. The deal can be sweetened by eliminating all of the labor, space, machinery, and emissions, both direct and indirect, of burning coal. Rising oil and gas prices will have similarly rapid breakevens.

    #3736
    Avatar
    Rematog
    Member

    Whoo, liquid carbon-hydrogen? Remember, this is not a physics lab, it’s a power plant. And, it’s supposed to be mass produced by the 10’s of thousands and run by people who have a high school degree. And be cheap to make.

    The reason I used helium in my analysis is 1) the low Z thing (about at the edge of my understanding of nuc physics). 2)the gas is commonly available on a commerical scale, and non-hazardous and non-corrosive.

    The reason for the air cooler, as opposed to a wet cooling tower is that I was pointing out “installation” costs for FF modules designed for “distributed” locations. A wet tower does not scale down this small, esp for unattended ops. The dry type (gas to air) is better for this kind of thing. The temps were in the 500F hot out of the FF module and 200F cool back into the FF module. I picked the high (500F) temp so that the delta T to the ambient air would be very high and 200F back so the approach (cool gas to cool air delta T) would be high, this keeps the heat exchanger small and relatively cheap.

    There is no way you can make something use cyrogenic gases and be cheap to make. I don’t know if there is any reason the physics of a FF module would require it (Eric?), but if not, avoid it and apply the KISS principle. (Keep it Simple & Stupid). That is how you control costs. You don’t optimize engineering performance, you optimize economic return.

Viewing 15 posts - 16 through 30 (of 101 total)

You must be logged in to reply to this topic.