Tonight I was asked a question in IM (instant messenger) that I thought was interesting. It ran along the lines of … and this is paraphrased …
“If you had a shipping container full of dirt, how much more energy will it have when it is 20 degrees hotter?” I am assuming it was 20 degrees Celsius due to the EU origin of the question.
In a 20 foot by 9 by 9 foot shipping container you have about 33 cubic meters.
Lets use sand since it is cheap and easier to store and deal with than water. Sand has roughly half the heat storage capacity of water.
Heat stored in 33 m3 sand heated 20 C can be calculated as
q = (33 m3) (1800 kg/m3) (835 J/kgC) ((90 C) – (70 C))
= 991,980 kJ
= (991,980 kJ)/(3600 s/h)
= 275.55 KwH
So for a 20 degree C rise in temperature, in 33 cubic meters of sand, you have stored a quarter of a megawatt hour of energy. To bring that into perspective, that is a 255 hp gasoline powered car, on a track, all out for a full hour, or a mid sized house for a week. All stored in a shipping container full of dirt.