Storing Thermal Heat
Thermal energy can be stored as sensible heat in a material by raising its temperature.
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 substance (J/kgoC, Btu/lboF)
dt = temperature change (oC, oF)
| 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 |
| Brick | 1969 | 921 | 1813 | |
| Cast Iron | max. 1150 (melting point) | 7200 | 540 | 3889 |
| Concrete | 2305 | 920 | 2122 | |
| Fireclay | 2200 | 1000 | 2200 | |
| 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 |
| Oak | 769 | 2385 | 1833 | |
| Pine | 496 | 2803 | 1391 | |
| Taconite | 3200 | 800 | 2560 | |
| Therminol 66 | -9 - 343 | 750 | 2100 | 1575 |
| Water | 0 - 100 | 1000 | 4190 | 4190 |
- 1 kJ/kgK = 0.2389 Btu/lbmoF
Example - Thermal Heat Energy stored in Granite
Heat is stored in 2 m3 granite by heating it from 20 oC to 40 oC. The denisty of granite is 2400 kg/m3 and the specific heat of granite is 790 J/kgoC. The thermal heat energy stored in the granite 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/lboF can be calculated as
q = (1 lb) (1.0 Btu/lboF) (1 oF)
= 1 Btu
Thermal Heat Energy Storage Calculator
This calculator can be used to calculate amount of thermal energy stored in a substance. The calculator can be used for both SI or Imperial units as long as the use of units are consistent.
Related Topics
• Thermodynamics
Work, heat and energy systems.
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