Energy Storage Density

Energy density - by weight and volume - for some ways to store energy

Energy Storage Density
Energy Storage		Typical Energy Densities
Energy Storage		(kJ/kg)	(MJ/m³)
Thermal Energy, low temperature	Water, temperature difference 100 ^oC to 40 ^oC	250	250
	Stone or rocks, temperature difference 100 ^oC to 40 ^oC	40 - 50	100 - 150
	Iron, temperature difference 100 ^oC to 40 ^oC	30	230
Thermal Energy, high temperature	Stone or rocks, temperature difference 400 ^oC to 200 ^oC	160	430
Thermal Energy, high temperature	Iron, temperature difference 400 ^oC to 200 ^oC	100	800
Conventional Fuels Energy	Crude Oil	42000	37000
	Coal	32000	42000
	Dry Wood	12500 - 20000	10000 - 16000
Synthetic Fuels Energy	Hydrogen, gas	120000 - 142000	10
	Hydrogen, liquid	120000 - 142000	8700
	Methanol	21000	17000
	Ethanol	28000	22000
Electrochemical Energy	Lead-acid batteries	40 - 140	100 - 900
	Nickel-cadmium batteries	350	350
	Lithium ion batteries	700	1400
Mechanical Energy	Hydropower, 100 m head	1	1
	Compressed air		15
	Flywheel, steel	30 - 120	240 - 950
	Flywheel, composite materials	> 200	> 100