Compressed Air Storage Calculations

Calculations for a 1kWhr System

• From Compressed Air Energy Storage results, it takes 170 cubic meters of air to deliver 1kWhr of usable stored energy.

Calculator

See https://www.tribology-abc.com/abc/thermodynamics.htm

According to the calculator, a 50 l tank of air at 3000 psi will release about 0.5kWhr via adiabatic expansion, and 2.5x this with isothermal expansion.

Rough Calculations

• Air tools require 30 cfm for 1 hp [1]
• A 300 cuf tank thus gives 10 minutes, about, of 1 hp power. With radial piston motor - at 10-20 the efficiency, easily gives 1 hp hr. Let's get specifics.
• 6 cylinders would thus give 1 hp hr. Not great, but we can get much better efficiencies from a better air engine.

Air Engine

• Rotary air engine - [2]
• 0,75 hp $200 30 cfm [3]
• Rotary vane, 1.8 hp $200 [4]
• Radial Piston Motor - 20x more efficient at full load than rotary! [5]
• Radial vs axial piston motors - [6]
• Data curve - 25 cu ft/min for 0.8 hp at 100 psi [7]

Cylinder Sourcing

• Firefighter supply - 300 cf $300 [8]
• 250 cf - $285 [9]
• 250 cf = $330 [10] K size?
• T-size 300 cf - [11]
• T goes up to 390 cf - [12]

Compressor

• Scuba compressor - $243, 1800W - [13]

Technical

• Compressed Air Index - [14]

Links

• Compressed Air Energy Storage
• Low Tech Magazine on Compressed Air Storage
• Gas Cylinders.
• Radial Piston Motor