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England recently had a snowfall, which is unusual nowadays. We had
a few tens of centimetres in some places, less in others. I'm
guessing that the average snowfall across England was on the order
of 10cm.
New-fallen snow typically has a density of 10% of water. Given the
land area of England,
this means that about 2x 10^15 grams of ice
was lying around.
Most of the snow was simply left to melt, and a tiny proportion of it
was snowploughed to other places.
I modestly propose that we should have harvested the snow using all
available technology.
Water has a latent heat of fusion of about 300 J/g, meaning that the
snow covering England had a total latent heat of fusion of about
10^18 Joules. The average Englishman uses, on average, something
like 1kW of power, and hence the total English power demand is
about 60GW.
So, the latent heat of fusion of the recent snowfall would provide all
of England's power for about 192 days, or half the year.
I therefore propose that we build power stations which use a cycle of
a refrigerant gas to run modified steam-engines, with snow acting as
the cold side of the system. Even given a 10% efficiency, huge
amounts of energy are available - perhaps even enough to power the
many snow-harvesters which would need to roam the countryside.
Vapor pressure
http://en.wikipedia...wiki/Vapor_pressure
chemical that is your favorite pressure at 0c [MercuryNotMars, Feb 10 2009]
[link]
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The only problem is that the latent heat of fusion
is not still in the snow. It's in the air from which
the snow fell. |
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But we surely could use the snow to cool things
next summer. They used to harvest ice for that
purpose; maybe we still should be doing it. |
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It is obvious that there is energy to be harvested because there will be a thermal gradient. Your idea has partial merit. Wouldn't you be better served by harvesting sea ice or lake ice or building a structure to allow water to freeze and be stored effeciently. It is a bit much to be traversing the entirty of the countryside. I am not sure if this is a joke idea //perhaps even enough to power the many snow-harvesters which would need to roam the countryside.// It seems a bit too appropriatly half baked. I guess the idea was mainly use snow in the summer. |
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But have you weighed the benefits of using sustainable energy (i.e from snow) against the positive effects arising from the country being covered in snow - and hence having a lower albedo - in countering global warming? |
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... iceberg-powered ships ? |
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I thought it's the condensation step, the one your snow would take care of, of a refrigeration cycle where you would get power if it were used as a power cycle. |
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Unfortunately, you can't extract energy by making heat flow backwards! |
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The latent heat you are talking about is the energy required to melt the snow, rather than being energy ripe for harvesting. There are some systems in use near freezable lakes that use a heat pump on this principle, using a rotating drum to pick water from the lake and freeze it (thus heating the refrigerant, and transferring the latent heat, to be released into a building when compressed) with the ice scraped off the far side of the barrel. |
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Nice idea - but you've just calculated the energy supplied to the snow by the ground and air. Possibly you could save some energy by dumping large amounts of snow in the sea/rivers and give us warmer weather sooner, but I doubt if it's gonna work out as a gain overall, given the area required to be covered. |
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A suitable delivery mechanism might be in the form of huge snowballs rolled along the roads by massive robots - both collecting energy, and keeping the roads clear in one fell swoop (except for the massive robots and their snowballs blocking the roads) |
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...and the massive amounts of energy to power the massive robots... |
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//Unfortunately, you can't extract energy by making heat flow backwards! // |
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fortunatly you can extract energy by making heat flow forwards. |
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Waste heat disapation is a limiting factor in producing energy. |
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You can use any liquid/gas that has a vapor temperature above 0c at some pressure. Technically you can use all gas too, but there is a pressure such that you can use a classic boiler model and the temperature gradient will creat a pressure gradient capable of producing mechanical energy. |
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Think of a steam locomotive it uses boiling water to push the piston it is also pushing agains the atmosphere. If it was in a vacuum it would work better and/or do the same thing without much heat. but you would have to do work to gather the water in the first place. Place the whole engine in a condenser if the box is cold enough the water will form and pressure will be the vapor pressure of water. Maxwell is proposing that the box be made 0c and that the pressure could be the vapor pressure of water at 0c for example. This does the work of gathering water and getting it out of the way of the way of the machine. with this help water will even boil at room temperature in this box. |
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sp. snowplowed
NOT snowploughed |
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that didn't look intentional |
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Always assuming that any noun can be verbed, snowploughed is probably OK. It ploughs the snow, y'see? |
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//sp. snowplowed NOT snowploughed// Either spelling is
fine (though obviously the English one is better) - just as
"plow" and "plough" are both valid. |
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a stirling engine would run happily on snow - well, on atmospheric heat. just keep your snow cold until the middle of summer, then fire up the stirling. as a bonus, the exhaust air could help cool buildings etc. |
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We always want to add that extra step //as a bonus, the exhaust air could help cool buildings etc.// idealy you would probably just add this straight to your neuclear power plant cycle or just cool the building. If our heat source is summer air then you would use a lot of air to get the boiler up to optimum temp. Idealy to get the most energy out there the coldness of the air is diluted to where the air unnoticably cooler. |
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Nothing wrong with the airconditioning idea it is probably the most efficient use, just make sure everyone understands that when you stack on a heat gradient you only divide the power. |
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Lace the paving stones with piezoelectric crystals and wire them together. Seed the clouds when the conditions are good for snow, then harvest the power of your fellow citizens falling on their backsides. |
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With the right spin, saving the planet etc it might work and possibly bring in enough revenue to off-set the legal bills. You could even sell the CCTV footage to TV companies and bring in a few more pennies. |
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