| Well now I guess I have to do the math: W = P(b)V(b) ln(P(a)/P(b)) (https://en.wikipedia.org/wiki/Compressed_air_energy_storage) CPAP requires roughly 10 cm of water pressure = 0.01 Bar
Sea level atmospheric pressure is roughly 1 bar
So the device has to pressurize to 1.01 Bar
Now I’ve looked it up, and a typical CPAP machine moves 20 to 60 liters per minute
Let’s say 30 liters per minute = 1800 liters per hour W = (1.007)(1.8)ln(1/1.007) = (1.81)*(-00698) = 0.0127 MJ = 3.53 Watt Hour So assuming perfect efficiency you would still need 28.64 watt hours of battery, just to do the compression. 470 Wh/kg for Zinc-air battery implies this device requires a 60gm battery (2 oz to those of us of a certain age) I looked up CPU fan efficiency (what they say they derived it from) and PEAK fan efficiency only approaches 25% http://www.nmbtc.com/fans/white-papers/fan_efficiency_import... So, you’d really need an 8 oz battery hanging from your nose to make this work, not counting what you need to run the electronics, etc. |
Part of the claimed innovation here is that the thing sticks directly into the user's nose. If it seals well, it's plausible that there's very little wasted air, which would account for the factor of roughly five.
(Also, you used the formula for isothermal compression, I think. A tiny little device like they showed would probably move air quickly enough through its fan that it would be closer to adiabatic. This doesn't matter much for the small pressure change involved.)