Heat Storage Capacities:
Heat capacity or thermal capacity is a measurable physical quantity equal to the ratio of the heat added to (or removed from) an object to the resulting temperature change. The SI unit of heat capacity is joule per kelvin. Specific heat is the amount of heat needed to raise the temperature of a certain mass by 1 degree Celsius.
Example - Heat stored in Granite
Heat is stored in 2 m3 granite by heating it from 20 oC to 40 oC. The heat stored can be calculated as
q = (2 m3) (2400 kg/m3) (790 J/kgoC) ((40 oC) - (20 oC))
= 75840 kJ
qkWh = (75840 kJ) / (3600 s/h)
= 21 kWh
Example - Heat required to to heat Water
The heat required to to heat 1 pound of water by 1 degree Fahrenheit when specific heat of water is 1.0 Btu/lboFcan be calculated as
q = (1 lb) (1.0 Btu/lboF) (1 oF)
= 1 Btu
The heat or energy storage can be calculated as
q = V ρ cp dt
= m cp dt (1)
where
q = sensible heat stored in the material (J, Btu)
V = volume of substance (m3, ft3)
ρ = density of substance (kg/m3, lb/ft3)
m = mass of substance (kg, lb)
cp = specific heat of the substance (J/kgoC, Btu/lboF)
dt = temperature change (oC, oF)