3.8. Fluctuations and storage http://www.ck12.org
Figure 26.14:Some properties of storage systems and fuels. (a) Energy density (on a logarithmic scale) versus
lifetime (number of cycles). (b) Energy density versus efficiency. The energy densities don’t include the masses of
the energy systems’ containers, except in the case of “air” (compressed air storage). Taking into account the weight
of a cryogenic tank for holding hydrogen, the energy density of hydrogen is reduced 39000 Wh/kg to roughly 2400
Wh/kg.
(a)
TABLE3.12:
fuel calorific value
(kWh/kg) (MJ/l)
propane 13.8 25.4
petrol 13.0 34.7
diesel oil (DERV) 12.7 37.9
kerosene 12.8 37
heating oil 12.8 37.3
ethanol 8.2 23.4
methanol 5.5 18.0
bioethanol 21.6
coal 8.0
firewood 4.4
hydrogen 39.0
natural gas 14.85 0.04(a) Calorific values (energy densities, per kg and per litre) of some fuels (in kWh per kg and MJ per litre).
TABLE3.13:
battery type energy density (Wh/kg) lifetime (cycles)
nickel-cadmium 45–80 1500
NiMH 60–120 300–500
lead-acid 30–50 200–300
lithium-ion 110–160 300–500
lithium-ion-polymer 100–130 300–500
reusable alkaline 80 50(b) Energy density of some batteries (in Wh per kg). 1 kWh = 1000Wh.