Bsky
Active Member
Liquid nitrogen (kinda condensed air) has about the same energy storage capability as a lithium ion battery. It's about 100-110 wh/kg. Its energy density is not that terrible either. I have thought of using that in place of batteries for a non-combustion engine in an UL. As only the weight of the storage tank is figured into the 254 government limit, this would be better than installing heavy batteries. Of course, the world is not quite so perfect.
Its energy density is not that terrible as compared to compressed air, but it is not high enough to get the job done. Suppose a plane gobbles up energy at rate of 11200watts (approx 15hp) and has 19.2 L (5gal) of liquid air in the old duct tape reinforced pop bottle storage tank. Therefore, it holds about 15kg of N2 which is enough for about an 8 minute flight.
The above calc may be a bit on the simple side, but i think it provides a fairly well-defined upper bound on the potential use of liquid air in ULs. You can add to this an inefficient pneumatic motor, frosting problems, acquisition problems, expense and you get nothing but bad air.
Of course, liquid air is hundreds of time more dense than the old-fashioned kinda air. This implies that compressed air is much worse and that if you are thinking about using compressed air--don't! Use liquid air instead. You get more bang for you buck. This seems to sort out all the compressed air argument for vertically-challenged vehicles as well, I think.
Its energy density is not that terrible as compared to compressed air, but it is not high enough to get the job done. Suppose a plane gobbles up energy at rate of 11200watts (approx 15hp) and has 19.2 L (5gal) of liquid air in the old duct tape reinforced pop bottle storage tank. Therefore, it holds about 15kg of N2 which is enough for about an 8 minute flight.
The above calc may be a bit on the simple side, but i think it provides a fairly well-defined upper bound on the potential use of liquid air in ULs. You can add to this an inefficient pneumatic motor, frosting problems, acquisition problems, expense and you get nothing but bad air.
Of course, liquid air is hundreds of time more dense than the old-fashioned kinda air. This implies that compressed air is much worse and that if you are thinking about using compressed air--don't! Use liquid air instead. You get more bang for you buck. This seems to sort out all the compressed air argument for vertically-challenged vehicles as well, I think.
