There is no doubt that Hydrogen grabs most headlines in clean energy promotion , seems all so simple the fuel cell can work with H2 gas and air and produce a decent amount of electrical energy .Things start getting a bit different for trying to move heavy loads or where large amounts of power are needed as what is termed the energy density starts to become important , Diesel has a very high energy density and liquid fuels in general give battery/fuel cells a good run for the money in power terms.
Things are changing , but fuel cells remain at around 60% efficient and bit more for the very hot solid oxide ones.
There is also the development of Hydrogen to be blended in natural gas mixtures for use in Gas turbines at around 20% by volume which has been successful and now the 100% hydrogen gas turbine is being developed , given gas turbines have recently broken the barrier for heat engines with 64% efficiency ,then this could well replace the fuel cell.
The main problem with hydrogen and particularly liquid hydrogen is the energy used to get it to liquid , 95% of all the worlds hydrogen used in mainly ammonia production comes from the steam reforming/gas shift reaction of natural gas which creates CO2 , 1000kg of liquid Hydrogen produced by this method produces 9-12 tonnes of CO2 (CO2 is quite heavy) , efficiency of energy in ammonia plants has improved but 1000kg of Ammonia uses 27,000,000 KJ , But here's the strange thing there is actually more Hydrogen in 1000m3 of Ammonia than in 1000m3 of liquid Hydrogen (146 kg of H2 in 1000m3 of Ammonia vs 71kg of H2 in 1000m3 of H2) . To keep it liquid great pressures are required for Hydrogen as well as vessels needing low thermal loss properties . A typical H2 fuel tank will need to be able to handle 350 bar which isn't far off the sorts of pressures found at the sea bed where the Titanic now rests , in old money that's 5000 lbs per sq inch.
according to IEA stats
1.4 GT of CO2 comes from the chemical industry
2.3 GT of CO2 comes from cement making (where calcium carbonate is heated/sintered driving off the CO2)
2.1 GT of CO2 from steel making
However the IEA stats don't really delve into the CO2 of steam reforming of natural gas , if we add the CO2 from oil the unit of the Barrel (around 40 us gallons 159 litrs ) produces a minimum of 317kg of CO2 and we use 95,000,000 Barrels a day.
1 Giga Tonne of CO2 is around 505,000,000m3 of CO2 , coal fired power stations put out around 10GT of CO2 globally
So back to Hydrogen , how much Hydrogen is made annually … mmm this is a tricky figure to get hold of and hoping this is correct I found 164,000,000,000 KG of H2 are produced every year mostly (95%) by steam reforming of natural gas so I get that to (9-12 tonnes of CO2 per tonne of Hydrogen) to 261 to 348 million tonnes of CO2 for making the so called clean fuel Hydrogen (or 131-175 million M3 of CO2)
Flares , no not my fashion statement from the 1970s but the flaring of CH4 from gas and oil wells as part of the extraction process world bank report today has 150,000,000,000 m3 of natural gas flared off annually , enough to meet the gas requirements of sub Saharan Africa , which is kinda wasteful even if pretty in the night sky.
If we move to electrolysis of water current PEM technology claims to convert 75% of the electrical input , the hot alkaline variant 85% , but 1kg of Hydrogen needing 60kwh of electrical energy to make , soo 1000kg of H2 would require 60,000 kwh , so 164,000,000 tonnes of hydrogen for Ammonia I get to 9,840,000,000,000 KWh and this produces CO2 unless from a renewable source . (unsure if figure quoted is inclusive of 25% electrical loss or not if so 1kg of H2 would be 80kwh and not 60kwh)
Its getting complicated which direction to take , more electricity to make green hydrogen , more electricity to power the electric car , hows the world going to do this ???
Well perhaps a start is for Hydrogen from water electrolysis to make Hydrogen for Ammonia then at least that's the 261-348 million tonnes of CO2 from ammonia taken care of.
mmm 2,300,000,000 tonnes CO2 from cement making , I mean wow gee if we could only do something with that ?
