Naked Science Forum
Non Life Sciences => Technology => Topic started by: Zichichi on 12/01/2006 19:40:22
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What a sorprise.....!
Did you know that NaCl is able to store 250 kwh/m3 of
thermal energy?
Its heat of fusion is formidable, it stores all that heat
at the same fusion temperature.
It's a formidable answer to store solar energy or wind energy in order
to produce electric energy....
Without words!............ [}:)]
nothing is created and nothing is destroyed
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Um, yes, but on the other hand the fusion temperature is pretty formidable too (801 C), so it would require some pretty remarkable insulation to prevent most of the energy being lost to the surroundings. I find it hard to believe this could be achieved with enough efficiency to be worthwhile... tho' of course I may be missing something crucial, and there may be some terrifically elegant and clever way of doing it.
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I don't think it's a great problem.
About wind energy
Wind energy can be stored in this heat of fusion through electric resistences therefore this temperature is not a problem...
About solar energy
If solar flux is more than 30 w/cmq I think it can be sufficient...
The planet Mercury has a solar flux about 1 w/cmq and its temperature is already 400°C!
There are some solar furnaces that are able to obtain a solar flux about 1000 w/cmq and a temperature more than 3000 °C.
nothing is created and nothing is destroyed
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My question wasn't whether you could get the energy into the NaCl. You can do that by generating the electricity and then using that to heat the salt. No problem. It was whether you could get it out again in a usable (electrical) form. I'd expect a lot of the energy to get lost to the surroundings, especially as the peaks and troughs in supply from renewable sources tend to be over at least hours (tidal) if not days or weeks (wind/solar).
I'm sceptical about that!
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Forgive me if I'm being obtuse, but what's wrong with a battery?
For instance, Saft have built a 46 MW battery in Alaska comprising 13000 ni-cads capable of supplying a town of 10,000 for about 20 minutes. It's intended as a backup if the power station goes down (which it frequently does).
Chris
"I never forget a face, but in your case I'll make an exception"
- Groucho Marx
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quote:
Originally posted by rosy
My question wasn't whether you could get the energy into the NaCl. You can do that by generating the electricity and then using that to heat the salt. No problem. It was whether you could get it out again in a usable (electrical) form. I'd expect a lot of the energy to get lost to the surroundings, especially as the peaks and troughs in supply from renewable sources tend to be over at least hours (tidal) if not days or weeks (wind/solar).
I'm sceptical about that!
I don't know if it's a real problem......
An example: the planet Venus has a temperature more high than that of Mercury and the reason is the Venus ability to store a lot of heat with that temperature......
I think that Venus and Mercury show a lot of secrets..about the solar radiation.......
A question can be: Why Venus has a temperature more high than that of Mercury?..........
nothing is created and nothing is destroyed
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I can't see, really, the relevence of the high temperatures of other planets to what I think you're saying. My difficulty with your proposal comes down to basic thermodynamics- if something is hotter than its surroundings it will lose energy to those surroundings, and the greater the temperature difference the faster that heat loss will occur (absolute temperatures are more or less irrelevant).
My sole difficulty with this proposed energy storage system is:
If you have a system at around 1100 K on a planet whose temperature is about 300 K then the hot thing will rapidly heat up its surroundings thereby colling itself down. You don't seem to have addressed that.
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The planet Venus receives the same solar radiation of the Earth
because it reflects a lot of it.
It would have to have the same Earth temperature therefore...all
the solar radiation of the day is good in order to give energy
to our system.
I want to say that solar radiation is not a hot mass in order
to apply thermodynamics...
This is the first point.
The second point is isolation....
If we copy Venus system then we have an energetic balance
between solar radiation on the Earth and a mass that has
a temperature about 480 °C.........
But......
[8D]
nothing is created and nothing is destroyed
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You will need something like a catalytic converter for Na and Cl like that for H2 and O2. Also chlorine gas should be compressed to store in a small volume. I think this can be a alternate energy storing device
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catalytic converter for Na and Cl
The original post was talking about storing thermal energy as hot, molten NaCl (http://en.wikipedia.org/wiki/Solar_thermal_energy#Molten_salt_storage), not using electricity to decompose the salt into (quite dangerous!) Na metal and Cl gas.
This is distinct from batteries that store electricity using molten salt as the electrolyte (http://en.wikipedia.org/wiki/Salt_battery).
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It's potentially quite a a simple system though...
I suppose its efficiency vs. batteries depends upon 1) insulation of the storage vessel 2) conversion efficiency [back] to electricity.
Both of these are quite well-understood sciences.
The insulation issue would probably come down to a matter of bulk and cost, and possibly public safety if considering storing tons of molten salt in built-up areas.
The heat could of course by used directly in community heating systems, but to convert to electricity I wonder if the best approach would be to use well-established steam turbine techniques. NaCl reserviors could even be added to existing thermal power stations to produce combined generation/storage facilities.
How does the melting point (800 degrees odd was it?) compare to temperatures reached in a conventional superheating boiler I wonder?
It may also have advantages over batteries in longevity and the lack of potentially environmentally damaging materials (assuming you don't plough the salt into your fields, that is).
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My town up until 1950 had a 20MW coal fired power station DC of course with a lead acid battery back up, that sort of power station was pretty common in the early part of the twentieth centaury.
I can see no less efficient way of storing electricity than converting it to heat and then generating electricity from the heat.