Question

Calculate the thermal energy in a cubic meter of air at room temperature and one atmosphere. Is it possible to extract this energy to charge your mobile phone? Explain.

Answer 1

Answer:

312 kJ

Explanation:

The thermal energy contained in a cubic meter of air at room temperature (20 C) and one atmosphere (101 kPa) would be.

H = Cv * T + p * V

Being

Cv: specific heat of air at constant volme (0.72 kJ/(kg*K))

T: temperature in absolute scale (20C is 293 K)

Then:

H = 0.72 * 293 + 101 * 1 = 312 kJ

The only way to extract thermal energy from a body and turn it into useful work (such as charging a phone) is to exchange heat with it and a another colder body. So, with just the air at room temperature it is impossible to extract its heat energy.