An alternative to storing electrical energy in batteries is storing energy in the form of hydrogen. Hydrogen cam be easily generated by electrolysis.

Liquid Hydrogen Properties: H2 density = 0.07 g/cm3 ( gasoline 0.75, water 1.0) Energy storage of H2 = 2.6 that of gasoline per unit mass Liquid hydrogen needs 4 times the volume to give same energy as gasoline

15 gallon automobile gas tank contains 90 lbs of gasoline 15 gallon automobile gas tank contains 90 lbs of gasoline. To get the same energy output would need 60 gallons of hydrogen , but the hydrogen would only weigh 34 lbs.

Electrolysis: 1 gallon water produces 1250 gals (4.7 m3) of hydrogen (gas) Power consumption: 4 kwh per 1m3 of H2 produced Voltage required: 1.8 to 2.6 V

Compression of Hydrogen

An alternative to burning H2 as a fuel in an internal combustion engine (to run a generator) is to use a fuel cell to generate electricity directly from H2

A single fuel cell produces approximately 0. 7 volts A single fuel cell produces approximately 0.7 volts. Individual cells are stacked to attain higher voltage outputs. This is shown in the following slide.

Possible hydrogen storage sites include the tower structure for a wind turbine electricity source (followed by electrolysis). H2 storage

Assumptions: Tower height = 100 ft. Tower Diameter = 8 ft. Tower hollow with wall thickness = 1 in. Store H2 at 10 atm (150 psi) pressure Volume of tower is approximately 5000 ft3 At 1 atm of pressure 11.1 m3 ( 392 ft3) of H2 = 1 kg of H2 (ideal gas law pV = nRT) At 10 atm 39.2 ft3 = 1kg of H2

Capacity of tower = 5000 ft3/39.3ft3/kg = 128 kg of H2 Energy content of H2 is approximately 30 kWh/kg Total energy of stored H2 is 38,400 kWh. Some of this energy will be used to pump the H2 to 10 atm pressure – see next slide