Hydrogen Fuel Cells today achieve electricity outputs of 23kWh per kg Hydrogen input exhausting 9 liters of reusable water. Depending on the fuel-cell technology used such power generation can accommodate intermitting cycles to mitigate idling operations. In today’s fossil fueled power mix coal represents 73% of the fossil Carbon use for electricity, whereof 30% are just squandered during idling operations. Replacing 8.7 Peta Watt hours [PWh] by Wind Turbines would need additional Hydrogen Fuel Cell Power back-up.
Based on data from “Windenergy Germany” Electrolysis employing 6MW windmills at 30% nominal with 66% average usage rate 50% of coal power might be directly substituted by 0.27mln windmills. The other 50% including back-up need an order of 180mln tonnes Hydrogen requiring 1.1mln Power to Hydrogen installations globally. Approximately up to 35% of this Hydrogen from PtG-Electrolysis will have to be stored economically. This would be 0.7trl m³ and equivalent to 20% of the Natural Gas [NG] used today. Although volumetrically it would be technically possible to blend Natural Gas volume with up to 30% Hydrogen, existing infrastructure is deemed to safely cope with 4% at maximum only. Therefore 75% of the storage would need to undergo a Methane synthesis. If done with captured CO2, 50% of the Hydrogen input gets lost in water.
Looking at the 50% Recyclable Terrestrial Carbon of agriculturally not meaningfully compostable global turnover, 1.9 Giga tonnes [Gt] (60 Exa Joule) stored chemical energy are left after covering primary plastics industry’s raw material needs. Splitting water with it into 550mln tonnes of Hydrogen, 13.7 PWhel Fuel Cell Power generation can be enabled at 0,55 tonnes CO2 per MWhel footprint from steam reformed Recycled renewable Carbon. Equivalent electricity from Coal and Natural Gas together cause 0,95 tonnes CO2 per MWhel off fossil imports from earlier eons! Since release of energy stored in the Carbon can be largely modulated to match grid load with demand, above cited direct 50% coal-power (4.3 PWhel) substitution by 0.27mln windmills would not leave 172mln tonnes Hydrogen unconsumed plus add 20% Power to Gas [PtG] negative regime energy storage potential. If 1.3% of the Recycled Carbon was used to store such 8.5mln tonnes Hydrogen PtG electrolysis (less than 3% of NG volumes consumed) in a CO-based Methane Synthesis, storage-output could be increased to 140% of PtG Hydrogen input (8.5 -> 12mln tonnes).
Transportation fuels consuming 25% of fossil imports from earlier eons blast more than 50% of its Carbon into atmosphere during refining prior to fuel use. This could be replaced by just 110mln tonnes of Hydrogen. With the total Hydrogen potential from Carbon Recycling in combination with PtG and a transformation of the energy sector to Hydrogen Economy the COP21 Climate Protection Accord’s aspired exit from fossil energies could be delivered by 555mln tonnes (non-volatile) renewable Hydrogen plus 300,000 additional windmills or solar electricity equivalents. These mass balances include storage release energy requirement while storage input transformation energy is assumed to be balanced against gross input surplus.
Separating Hydrogen after Steam reforming or from the NG-blend by Dry Thermo-Catalytic Dissociation [DTCD] prior to Hydrogen use in Fuel Cells can eliminate energy intensive Pressure Swing Absorption [PSA]. When steam reforming the synthetic NG [SNG] taken out storage reaction CO2 could be bottled for Food & Beverage or other industries due to cleanliness of the DTCD Methane derived Carbon.
Further considering the possibilities to produce Hydrogen with Concentrated Solar [CSP] or photo-synthesis in future, there will be comfortable headroom going forward implementing Hydrogen Economy.