Compressed Air Calculations: Difference between revisions
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[[File:caespower.png|300px]] | [[File:caespower.png|300px]] | ||
*Type K Gas cylinders are 50l, or 1/20th cu m. Bottom line for compressed air: at about 3000 PSI - energy in a cylinder is 50MJ/m3 at 50% extraction efficiency. Thus, one Type K cylinder has 2.5MJ of energy storage - or 0.7kW hr. WTF????? | *Type K Gas cylinders are 50l, or 1/20th cu m. Bottom line for compressed air: at about 3000 PSI - energy in a cylinder is 50MJ/m3 at 50% extraction efficiency. Thus, one Type K cylinder has 2.5MJ of energy storage - or 0.7kW hr. WTF????? Right. That is theory, but off-the shelf parts (see [[Air Motors]]), even piston ones - are rather pathetic. | ||
**Does this check? 20,000*ln(20/0.1)=100,000 kJ/M3 = 100MJ/m3 at 100% efficiency, or 50MJ/m3 with 50%. | **Does this check? 20,000*ln(20/0.1)=100,000 kJ/M3 = 100MJ/m3 at 100% efficiency, or 50MJ/m3 with 50%. | ||
**This is rather impressive - 50% efficiency of expansion gets 0.7 kWhr - but heat must be added here to increase the energy output of the expansion engine. | **This is rather impressive - 50% efficiency of expansion gets 0.7 kWhr - but heat must be added here to increase the energy output of the expansion engine. | ||
Revision as of 17:48, 28 February 2021
Calculations
- For example, compressed air at 2,900 psi (~197 atm) has an energy density of 0.1 MJ/L calculated from P*deltaV. [1]
- Pressure - N/m2 - 3000 psi = 2E7 Pa. Delta V - of 1 liter or E-3 cu meter - to 214E-3 cu meter.
- PdeltaV=2E7*214E-3=214E4=2E6 = 4MJ for that one expanded liter, as max possible work - but this is just PdeltaV without considering real thermodynamics underneath. Ballpart ok.
- Need to use PV-Work Calculator -https://www.geogebra.org/m/KAZHEN8c
- See formula for energy density - [2]. This shows 50MJ/m3 = 0.05 MJ/l at 50% efficiency
- From [3]
- Type K Gas cylinders are 50l, or 1/20th cu m. Bottom line for compressed air: at about 3000 PSI - energy in a cylinder is 50MJ/m3 at 50% extraction efficiency. Thus, one Type K cylinder has 2.5MJ of energy storage - or 0.7kW hr. WTF????? Right. That is theory, but off-the shelf parts (see Air Motors), even piston ones - are rather pathetic.
- Does this check? 20,000*ln(20/0.1)=100,000 kJ/M3 = 100MJ/m3 at 100% efficiency, or 50MJ/m3 with 50%.
- This is rather impressive - 50% efficiency of expansion gets 0.7 kWhr - but heat must be added here to increase the energy output of the expansion engine.