Quote:
Originally Posted by jamesqf
There's another potential problem for automotive use. Compressing a gas creates heat (and uncompressing it absorbs heat), which is why scuba tanks are generally filled in a water bath. What happens to that heat in a car? Especially when you're doing something like descending a mountain?
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A good point james, compressing the gas in an accumulator means compressing the heat energy in the gas, most of the time measured in kelvin degrees. Decompressing the gas means it cools rapidly as it heats rapidly when compressed. The concentrated heat energy also contributes to the pressure of the compressed gas. I would think you would want to insulate the accumulator to conserve the heat energy for better overall efficiency.
In situations where you are faced with prolonged downhill grades where your capacity is not suffecient for recovery of all of the available energy you have two choices. In crease the size of the accumulator or bypass the accumulator with fluid passing through a variable restrictor to provide braking energy, but also loosing the potential energy you might recover otherwise.
This would require consideration of the driving environment and sizing the accumulator accordingly. In an electric vehicle, excess energy could be returned to the battery.
This scenario is also where all electric vehicles would also suffer dramatic range reductions. Consider the range of a Nissan Leaf if you drove it up Pikes Peak at maximum speed. It might not make it the 12 mile distance of the course.
regards
Mech