Auto Economics, the AIR CAR Arrives

Discussion in 'Economics' started by libertad, Jan 10, 2008.

  1. maxpi


    I guess the transfer of energy is much more efficient with a compressor directly connected to the power grid and transferring the energy via compressed air.... makes sense now that I think of it... transferring energy to a battery is lossy, there are losses in the conversion from the grid to the battery voltage, losses across the batteries' output resistance putting the energy in, and losses across the batteries' output resistance taking the energy out... an engineering exercise that I recall was to calculate the energy loss when a fully charged capacitor was paralleled with a fully discharged capacitor.. it was astoundingly high, 50% exactly in fact, the battery situation may be similar... losses in the air pressure transfer have to be a lot lower than that... maximum power is limited however to air tank strength and size...
  2. hmm - wonder how hydraulic would work rather than air. It has much more compressive power, I think...?
  3. Hydraulics are a medium of energy *transfer* but of no use for energy storage in automotive technology. Hydraulics energy storage would be applicable say in dams or other large masses of water/fluids only.

  4. With air compressor charging stations powered by a nuclear power grid, the air car would find a way to completely circumvent the need for crude oil. I like the concept although I don't care for Tata.
  5. I love Tata's.
  6. Here is a new engine design that has been tested with compressed air:

    What if liquid nitrogen was used instead of compressed air? CO2 is stored as a liquid and used as a gas in paint ball guns, perhaps liquid N2 could be more space efficient?
  7. 9999


    Me too!!

    But seriously, the question will be how much $$$ (in my case €€€) it takes to produce the compressed air, and by what means.....
  8. I understand that liquid C02 is used in paint ball guns because it is effectively a self-regulating gas supply - whenever the storage vessel is pressurised enough to liquefy, the pressure of the remaining gas does not go up any higher. In other words, it doesn't matter if the storage chamber is 9/10s full or 1/10 full the gas pressure is the same, as it is fixed at the vapour pressure of the liquid. This results in a much simpler mechanism for the paint gun, as it doesn't need to accommodate decreasing pressures as the gas is used (until there is no liquid in the vessel left, only gas).

    Compressed air has a much higher vapour pressure than C02, due to the much lower boiling points of the gases, so it will have a much higher pressure and more energy to release. Basically the harder the gas is to liquefy, the more energy can be pushed into it by compressing it. Although liquid nitrogen at normal pressure - such as highly cooled in an open container doesn't have so much potential energy because it needs to gain heat to expand. Nitrogen (or air) compressed to the extent that it liquefies at normal temperature would have tremendous potential energy. I'm not sure if the proposed car system does use air compressed to this extent - possibly isn't necessary and would just require thicker storage tanks.

    In any case I assume a hydrogen tank would still have a higher energy density than compressed air.

    Which is more efficient overall, electrolysing water or compressing air?
  9. That flies in the face of every chemistry class I have ever taken at my university. I thought that PV=nRT
    #10     Jan 11, 2008