Energy Storage in Water - kWh

Thermal energy stored in water

Water is commonly used to store thermal energy. Energy stored - or available - can be calculated as

E = c_p dt m             (1)

where

E = energy (kJ, Btu)

c_p = specific heat capacity (kJ/kg^oC, Btu/lb ^oF) (4.2 kJ/kg^oC, 1 Btu/lb_m^oF for water)

dt = temperature difference between water stored and the surroundings (^oC, ^oF))

m = mass of water (kg, lb_m)

Example - Energy stored in a 1000 liter water reservoir

If water is heated to 90^oC and surrounding temperature (where the energy can be transferred to) is 20^oC - energy stored can be calculated as

E = 4.2 (kJ/kg^oC) (90 (^oC) - 20 (^oC)) 1000 (liter) 1 (kg/liter)

    = 294000 kJ

    = 81.7 kWh    

• 1 J (Joule) = 0,1020 kpm = 2.778x10^-7 kWh = 2.389x10^-4 kcal = 0.7376 ft lb_f = 1 (kg m²)/s² = 1 watt second = 1 Nm = 1 ft lb = 9.478x10^-4 Btu

Energy Stored in Water - Liters / kWh

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