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San Francisco Mayor Gavin Newsom: Cities and Time

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Previous FORAtv comments:
Periergeia Avatar
Periergeia
Posted: 06.14.10, 11:47 PM
Compressed air is not an energy source. It is, at best, a mediocre energy storage mechanism. In case of cars, it's a pretty poor storage mechanism. Why? Thermodynamics... again. When gas is compressed, it heats up. Part of the energy used to compress the gas is in the heat. In order to store the gas in compressed air tanks, this heat has to be removed by cooling. So now all that heat energy is lost (unless one had e.g. an endothermal chemical process coupled to it that can use some of this heat... but the options are rather limited). And that's only the first loss... there is still the decompression part! When the now cold compressed gas runs through the car's engine (which is really nothing else than a compressor running in reverse), the gas cools down very considerably. So in the end, we have cold decompressed gas, which has a much smaller volume than originally at room temperature when it entered the compressor in the "compressed air station". Of course, one can use part of that cold air for air conditioning. One can also heat it with a gasoline or natural gas burner on board the car... which is kind of a hybrid concept. The energy stored in the chemical fuel would be used with fairly high efficiency in this case... certainly a lot more efficiently than in a combustion engine. The resulting engine is just a lot more complex than the simple compressed air engine. So how useful is this concept? Depends on how the energy used to compress the air is generated. It certainly makes next to no sense to use conventional thermal power plants for this purpose. However, intermittently available solar or wind energy might be close to ideal since the peak power is either going into some sort of storage or is lost... The same would be true if we expanded our nuclear power plant capacity far beyond base load like the French. In that case, because there is excess energy that would be lost otherwise, the compressed air for transportation could come for almost free. Of course it still requires a non-trivial infrastructure investment to build the fueling stations and the update to the electrical grid.
Frankystein123 Avatar
Frankystein123
Posted: 06.04.10, 12:26 AM
Now this is a truly revolutionary idea that can actually have a big impact on being environmentally friendly.
pokerandwine Avatar
pokerandwine
Posted: 06.12.09, 01:11 PM
What about cars that run on compressed air? This is sustainability as good as it gets. Will it ever become a reality? http://www.youtube.com/watch?v=ztFDqcu8oJ4
Vasil Avatar
Vasil
Posted: 06.11.09, 02:10 PM
I wonder if Gavin Newsom’s concept in treating cars as cell phones by purchasing miles instead of minutes would in a way limit unnecessary driving by charging extra fees as it happens when you go over minutes on your plan. Great idea of electric cars and parking spaces with sensors and rechargeable meters, however, needs to be adopted around the states; otherwise San Francisco will become a secluded community.
MithShrike Avatar
MithShrike
Posted: 04.16.09, 02:16 PM
The actual link he was referring to for the solar mapping is http://sf.solarmap.org/ .
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