kap4: Storage

1) Compressed

• mostly used for transport

• just as safe as petrol

• loses 4-8 % of energy input

2) Liquid

• mostly relevant for large quantities and long transport

• Density: 3x higher than CGH2 at 300 bar

3) Chemical storage

• Ammonia and methan: temporary energy carriers: must be converted back to pure H2

• both are toxic

• can be stored like other chemicals

• can be stored and transported at room temp and atm pressure

-> you cant differ between gas and liquid hydrogen

-> yes, with higher pressure there is a higher boiling point

• mechanical compressors:

  • direct conversion of mech. energy into gas energy, most common, used to fill vehicles

  • Piston compressor

• non- mechanical compressors:

  • thermal: Hydrogen storage in metal hybride

    no moving parts - less maintance, low sound and vibration, modular, easy to scale up, high safty, low operating costs

  • electrochemical: more efficient than mech. compressors for small volumes, used for small scale up compression to high pressure

No plants which produce liquid hydrogen in norway

• takes a lot of energy to get produced

• duration of storage is limited: at some point it starts to boil (after ca. 16 days)

  (tanks not always cooled, heat goes through isolation and so liquid Hydrogen becomes gas, pressure rises)

Advantages compressed:

• easier to produce

• liquefaction work requires 20-30 % more energy

• Cheap final price -> from natural gas 12 kr/kg H2 CH2 vs. 25 kr/kg H2 LH2

• Technically simpler to store and transport

• Low operating costs (keeping -253 °C over time is energy demanding)

• Currently produced in Norway (facilities for liquefaction operations are not available in Norway today, but are being planned?!)

Advantages liquified:

• Higher energy density can be used on longer distances and larger ships / vehicles

• Tanks take up less space

• Shorter filling time

• More scalable

• Operational pressure is much lower than for compressed

Advantage:

• common gas in industry,

• low risks

• very high volmetric density

Disadvantage:

• toxic

• Ammonia is corrosive

• must be converted back -> energy loss -> efficiency low

future:

- bad to hava an extra step in line

+easier to store and sometimes you can use it directly

+if inprovment in efficiency than theres a future

Hydrogenation Haber -Bosch-Process:

Delta H= -92 kJ/mol

T= 400°-450°C

Dehydrogenation:

2 NH3 -> N2 + 3 H2

delta H= 92 kJ/mol

T= 700 -1000°C

• LOHC (FOHB): hydrocarbons upgraded to higher hydrogen content

• Temporary energy carrier must release the hydrogen again before use

• Can be stored at room temperature and atmospheric pressure poses lower risk

• Typical hydrogen content: 5- 6 weight%

• Required catalyst: Ni is widely used for hydrogenation, Pt for dehydrogenation

• can be stored at Room temperature

• can be stored at atmospheric pressure

  -> poses lowe risks

alpha Phase:

• hydrogen seperated on the metal surface

• hydrogen atoms are absorbed to the metal surface in a random pattern

beta Phase:

• hydrogen atoms are arranged in a special configuration with the metal atom -> metal hybride phase

+: • large amounts can be stored at low pressure

• no compression

• H2 density high, often higher than liquid H2

•safe

-: • Conversion and reconversion require energy

• Immature technology, barely commercially available

• Discharged oil must be transported back for recharging

• Need to be cleaned/distilled after n number of cycles

• Weight