hydrogen as an energy carrier

percentage of oil and petroleum consumption related to energy production

80 to 85%

loss in energy due to transmission

estimated >10%

efficiency of wall adaptors

70-87%

GaN chargers

past 5 years new technology has gallium nitride

transitioning from fossil fuels

• Solar kinetic energy of photons (solar radiation)

• Mechanical potential energy (hydraulic - water, osmotic) and kinetic energy (wind). Recharging movement (kinetic)

• Thermal energy (geothermic), but localised heat pumps appear to be very efficient

• Chemical bonds (water, glucose, etc)

• Weak force (nuclear decay and fission)

• Strong force (nuclear fusion)

oxidation of hydrogen

leads to the formation of water

hydrogen bond energy

relatively high bond energy (436 kJ/mol)

what is cleaner than hydrogen

fuel cells are cleaner and more efficient in conversion of electrical energy

sources of hydrogen

• current technologies rely on natural gas steam reformation - sulphur is a problem

• electrolysis of water - efficiency moderate

factors that contribute to water electrolysis efficiency

• Free energy change is 237 kJ/mol is high - upper limit efficiency is 83%, practically only 70% is achieved - partially due to surface effects

• Development into new types of electrodes is very important to increase efficiency (electron transmission)

natural hydrogen sources

• Mantle hydrogen from radiolysis

• Bacterial action

• Large reservoirs of hydrogen in France, Russia and Mali but are currently difficult to access

Useable direct usable hydrogen energy

120 MJ/kg or 33.3 kWh/kg

problem with hydrogen

not compressible at room or higher temperature

what is compression measured by

Z-factor

what range does hydrogen form explosive mixtures

4-75% in air

PEM

proton exchange membrane

electrolytic membrane Nafion

 a fluorinated ionic polymer, very thin

how does the membrane work

Induces proton hoping across the RSO₃ groups in the polymer - 50 μm (large distance). Membrane prevents gases (O2, H2) from passing. Membrane must be wet/moist at all times. Cathode/anode is Pt - very easily poisoned.

parasitic energy

cooling is required to prevent temperature over 80 degrees C

MOFs

metal organic frameworks

what is a MOF

a metal coordination compound with extended 3D network, ligands are extended aromatic groups with opposite binding sites - termed linker

surface area

key to MOF efficiency - a search for different linkers is necessary to achieve a surface area better than graphite

NU-100

a crystalline MOF, SA of 1 expanded out covers 1.5 American football fields

physisorption of H2

an exothermic process, so it will occur spontaneously. Highly advantageous for uptake, but not for release - problematic (need to heat the system to release)

formic acid - disadvantages

• CO₂  component represents the majority of the weight. Limits storage capacity to a max of 4.8% (Must carry onboard H₂O)

• separation of the H₂ and CO₂ gas stream - possible, but limits pressure output of H₂

metal hydrides

utilising ionic compounds that contain M-H where M is a metal (alkali, earth alkali, B, Al, Ga or a transition metal)

metal hydride advantage

metal hydrides are normally quite pure and produce a clean H2 gas stream

disadvantage

Safety (highly reactive with water- serve explosions possible)

synthesis

generally easily but the material must be ball milled to produce a fine powder = high surface area