Energy density

Date: 2015-10-07; view: 481.

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The energy density of coal is roughly 24 Megajoules per kilogram. It is perhaps more useful to put this into another unit of energy, kilowatt-hours. This is the unit that electricity is most commonly sold in. In that case, the energy density of coal is 6.67 kW*hours/kg.

One can put this information to use to figure out how much coal is needed to power things. For example, running one 100 Watt computer for one year requires this much electricity:

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The maximum Thermodynamic efficiency of coal power plants is about 30%. Of the 6.67 kW*hours of energy per kilogram of coal, about 30% of that can successfully be turned into electricity - the rest is waste heat. Coal power plants obtain ~2.3 kW*hours/kg of burned coal.

Plugging in this information one finds how much coal must be burned to power a typical computer for one year:

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It takes 838 pounds of coal to power a computer for one full year.