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Thermal energy can be stored in a material as sensible heat by raising its temperature.
The heat storage can be calculated as
q = V ρ cp dt
= m cp dt (1)
where
q = sensible heat stored in the material (J)
V = volume of substance (m3)
ρ = density of substance (kg/m3)
m = mass of substance (kg)
cp = specific heat capacity of the substance (J/kg oC)
dt = temperature change (oC)
| Material | Temperature Range (oC) |
Density - ρ - (kg/m3) |
Specific Heat - cp - (J/kgoC) |
Energy Density (kJ/m3 oC) |
| Aluminum | max. 660 (melting point) | 2700 | 920 | 2484 |
| Cast Iron | max. 1150 (melting point) | 7200 | 540 | 3889 |
| Fireclay | 2100 - 2600 | 1000 | 2100 - 2600 | |
| 50% Ethylene Glycol - 50% Water | 0 - 100 | 1075 | 3480 | 3741 |
| Dowtherm A | 12 - 260 | 867 | 2200 | 1907 |
| Draw salt - 50% NaNO3 - 50% KNO3) (by weight) | 220 - 540 | 1733 | 1550 | 2686 |
| Granite | 2400 | 790 | 1896 | |
| Liquid Sodium | 100 - 760 | 750 | 1260 | 945 |
| Molten Salt - 50% KNO3 - 40% NaNO2 - 7% NaNO3 (by weight) | 142 - 540 | 1680 | 1560 | 2620 |
| Taconite | 3200 | 800 | 2560 | |
| Therminol 66 | -9 - 343 | 750 | 2100 | 1575 |
| Water | 0 - 100 | 1000 | 4190 | 4190 |
Heat stored in 2 m3 granite heated from 20 oC to 40 oC can be calculated as
q = (2 m3) (2400 kg/m3) (790 J/kgoC) ((40 oC) - (20 oC))
= 75840 kJ
= 21 kWh
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