h a l f b a k e r yViva los semi-panaderos!
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Solar, wind and other renewables have a problem with intermittency. For solar (thermal), there are no real solutions (molten salts, not yet; pneumatic systems, not really). For wind, the situation remains difficult as well (batteries are out).
Create a well insulated space close to the renewable
energy facility. Make sure water is available. Use the excess electricity to turn the water into ice. Once you have big blocks of ice, transport it to urban/industrial areas, and use it for cooling spaces or processes.
In the 1970s, a person (who used to design nuclear space rockets), developed an "ice pond", a kind of a dome in which he stored ice, and then used it year-round to cool the campus of the university of Princeton. The system seemed to work, but then cheap air conditioning replaced it. The carbon footprint of air conditioning was not taken into account, back then.
Today, given that large footprint of air conditioning, it might be more efficient and less polluting to transport and use ice which stores excess energy from renewable power plants - even taking into account the CO2-emissions coming from transport (100+ g/km-ton for trucks) and the energy losses incurred during the conversion of water into ice.
(But I'm not sure.)
see also
Ice_20Pond_20Refinement
[mouseposture, Feb 20 2011]
Thermal Energy Storage Unit
http://www.calmac.c...roducts/icebank.asp
"With a full-storage configuration, a building’s entire cooling load is shifted to off-peak hours. The chiller only runs during off-peak nighttime hours in order to store ice for use the following day." [ldischler, Feb 21 2011]
[link]
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It might be better for the ice (or chilled water) to be produced where it will be used, but still taking advantage of peaks of energy generation. It would surely be cheaper to transport electricity than ice. |
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Perhaps we can use the ice to supercool transmission lines? |
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The person in the 1970s was Theodore B. Taylor (<link> #2 in
the linked idea). |
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re: transporting large quantities of ice, you'll need a carbon-
neutral way of doing that. In the past it was done with
horses (not carbon neutral) and sailing ships. Maybe you
could tow icebergs with sailing ships? |
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I wonder you could use the water supply to provide coolth? |
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Imagine a biiiig pipeline carrying water from a watermaking
factory to a city. Now insulate the pipeline and run it past a
renewable energy place, where it would be cooled using the
method [django] alludes to. |
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Then, run the near-freezing water through air conditioning
systems in the city before using it for its regular purpose. |
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//horses (not carbon neutral)// So how do horses produce more carbon than they consume? |
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As far as I know, horses don't do atomic fission or fusion, so
they can't release more carbon than they consume. |
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However, I did think horses released carbon that was locked
up in cellulose, etc., to a gaseous form more likely to affect
climate. It wasn't a very carefully thought-through
statement, but my reasoning was as follows: First, I assumed
they fart methane, like cows. Second, I assumed their
decomposing manure releases methane. |
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A tiny proportion of the carbon eaten by a horse will decay to nitrogen while in the horse's body. However, apart from possibly shielding an occasional nitrogen atom from cosmic rays, and thus preventing the creation of a carbon atom, the horse can hardly be held directly responsible. |
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So basically, horses are carbon neutral (ignoring, of course, the meaningless usage of the term popular with the media and stupid people). (Ahem. Present company excepted, [mouseposture], since you admit to not having thought it through.) |
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// the horse can hardly be held directly responsible // |
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Yes it can; they are guilty, without exception. Kill 'em all ! |
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Thank you, [pocmloc]; I enjoyed the paradox: burning
hydrocarbons is carbon-neutral, but nuclear power isn't. |
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(More seriously: it was the science I hadn't thought through,
not the usage: I stand by that. Feel free to condemn me as
an unprincipled descriptivist.) |
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//However, I did think horses released carbon that was locked up in cellulose, etc., to a gaseous form more likely to affect climate. It wasn't a very carefully thought-through statement, but my reasoning was as follows: First, I assumed they fart methane, like cows. Second, I assumed their decomposing manure releases methane.// |
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My understanding is that cows produce a relatively large amount of methane, because of how their digestion works. They have bacterial symbiotes in one of their stomachs, which allows them to digest cellulose, and hence get more energy from grass. Extra methane is a side-effect, and is burped out. |
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In spite of this I would suggest that even cows are strictly speaking essentially carbon neutral (in the widely recognised 'fossilised carbon released to the biosphere' sense) - provided their feed is not grown with fertiliser produced using fossil fuel. |
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This is how it used to be done. Even the terminology used today--tons of air conditioning--refers to the tons of melting ice that would be required to achieve the same effect (or the tons of ice that could be made). Ice houses were invented almost four thousand years ago, and modern air conditioning dates from the nineteenth century. Initially ice was manufactured in a central location and delivered in trucks (as they used to do when frozen ponds were the source), but this industry collapsed after WWII when home units were widely marketed.
As for a way of storing energy, creating blocks of ice has to be one of the most inefficient, yet it is done. For instance, if you make ice at night when it is cool, this takes less energy (and cheaper energy) than during the day, and then you can cool your building with it and save money. Typically, you don't transport the ice anywhere, you use it where you make it. |
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One method of energy storage I'm quite keen on is ground-heat storage. You dig a massive hole in your garden and coil a matrix of pipes down there. Then, during the summer, you heat-exchange all the extra warmth in your house out into the ground storage (essentially heating the ground beneath your garden while cooling your house) and then, in the winter, you re-use all of that stored heat by exchanging it back again into the house. |
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The trouble with this system is all the digging tends to spoil the rose-bushes, so it's only ever really done on 'greenfield' sites that can be conveniently returfed after the JCBs have gone - so I quite like the idea of compartmentalising it - perhaps converting one of the rooms of the house into a 'cold' room, and another one into a 'hot' room, insulating them both to buggery, and having a heat-exchanging central heating system pass through both using different pathways depending on whether you're setting the controls to 'heat' or 'cool'. |
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Finally, there must be a better material than water/ice/steam H2O for energy storage - perhaps oil of some kind, that remains at a more stable volume/density based on its thermal energy. |
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Zen, ice is used because of it's high latent heat. This is several times what it takes to get it from room temp to freezing. |
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I've never actually understood why they use a hose instead of a large tank: much less surface-area on the latter: a tank of water which is refreshed from the summer sun, and a tank of water/glycol (or something less poisonous) which is refreshed by winter nights. They'd have to be large tanks, mind. |
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I wonder how big the iceberg would be to cool New York during the summer. |
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[zt] water is used because both it's heat-capacity in all phases in terms of energy stored/released per degree Kelvin, and its latent heat of evaporation/condensation and fusion/unfusion are higher than anything else. |
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//As for a way of storing energy, creating blocks of ice has to be one of the most inefficient, yet it is done. For instance, if you make ice at night when it is cool, this takes less energy (and cheaper energy) than during the day, and then you can cool your building with it and save money.// |
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What do you mean by inefficient? It isn't inefficient energetically, or the example you give wouldn't make sense.
Certainly a large volume and mass of water is required, compared to that needed for an aircon unit.
I'm with you about not transporting the ice - I suspect that it would be much more efficient (as well as easier) to generate it where it can be used. |
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Also to be pedantic, ice used like this doesn't store energy, it stores the ability to absorb heat.
... although it would be possible to recover some useful energy from the temperature difference between the ice and what you're trying to cool. That would be fun. |
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//I suspect that it would be much more efficient (as well as easier) to generate it where it can be used.//
Efficiency is relative. |
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In any big city, the amount of space needed to make and store ice would be better used, from the property owner's point of view, to rent out as living/working space. |
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//What do you mean by inefficient?// |
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It has thermodynamic inefficiencies when you make the ice, and again when you use it. Obviously, this isn't important when you're using it for cooling, but for any other use--such as generating electricity--there are better ways of storing energy. (And you're right. It isn't storing energy, it's creating an energy sink.) |
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//In any big city, the amount of space needed to make and store ice would be better used, from the property owner's point of view, to rent out as living/working space.// |
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That's the thing I don't quite understand about big cities - the space ought to be less desirable for offices &c, because commutes are long and difficult due to congestion, and (particularly where it usually gets hot) cooling is more difficult - because of all the aircon and other activity, there's even more heat... and the price of land is very high.
And yet, companies all set up offices together in the centre, rather than going somewhere nearby which doesn't have these disadvantages. |
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// set up offices together in the centre, rather than going somewhere nearby which doesn't have these disadvantages // |
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But then they ALL move, which just translates the problem somewhere else (Boca Raton ?) |
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//Zen, ice is used because of it's high latent heat.// Yes, I guess that's true - and it is of course very generally available (at least in one form or another) - it's just a shame that it can't also be used to reliably sending down pipes in temperature ranges between ±100°C on account of the huge density changes it goes through (density changes that perhaps account for the high latent-heat values?) - not to mention it going solid at temps < 0°C and explosively gaseous at > 100°C - Both reasons for which it isn't generally used as the coolant fluid in refridgeration, air-conditioning, or other high temperature-range application. Which means that in any such system (i.e. one that uses water) you're either going to have to use steam/water/ice for storage and have another medium to transmit your energy, or keep it all water and just make sure no part of the system goes outside the operating parameters. |
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Zen_tom, slush ice (or slurry ice) is pumpable, and used for refrigeration (eg on fishing boats) already. |
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Hmmm, not heard of that - but that would do it - thanks! |
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Brine, or glycol/water mixes, are both extensively used as heat transfer media. Althouh corrosive, brine has the advantage of being cheap, and acceptable for food contact, and is thus widely used in the food processing industry. |
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Somwhere in CA, USA they make ice on terrace at night when electricity is cheaper and use the ice during day for AC. |
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Why not just transfer to potential mechanical energy by lifting
heavy weights? |
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