Physics
posted by Janaih .
Compressed air can be pumped underground into huge caverns as a form of energy storage. The volume of a cavern is 5.60 105 m3, and the pressure of the air in it is 8.40 106 Pa. Assume that air is a diatomic ideal gas whose internal energy U is given by U = 5/2 nRT. If one home uses 14.0 kWh of energy per day, how many homes could this internal energy serve for one day?

Well, PV=nRT, so U= 5/2PV.
That will be in Joules. To convert to kWh (kJ3600sec), divide by 1000, then divide by 3600. That will be the energy in kWh of stored energy.