Hydrogen has a high specific energy density by weight. Under normal circumstances however, hydrogen is a gas meaning that the energy density per unit of volume is relatively low.
So storing hydrogen is more challenging than storing liquid energy carriers.
non-toxic & non-irritant
environmentally neutral & non-water pollutin
volatile, 15 times lighter than air
Blue hydrogen is grey hydrogen where the CO2 generated during production is separated and stored using Carbon Capture and Storage technologies (CCS). The CO2 generated during hydrogen production is therefore not released into the atmosphere and the resulting hydrogen can be considered carbon-neutral on balance.
Grey hydrogen is produced from fossil fuels. In general, natural gas is reacted with steam to produce hydrogen and CO2 (steam reforming). The CO2 is not used and subsequently released into the atmosphere, thereby strengthening the global greenhouse effect: producing one ton of hydrogen generates around 10 tons of CO2.
Green hydrogen is produced from water in an electrolysis process that is solely powered by electricity from renewable energy sources. Irrespective of the electrolysis technology used, this hydrogen production method is carbon-neutral because all the electricity is derived from renewable, carbon-neutral energy sources.
At present, hydrogen is still largely produced from fossil fuels like natural gas or coal. However, this process generates large quantities of CO2, which have to be captured and stored at significant expense in order to achieve a positive effect on climate change. Electrolysis, a process in which water is separated into hydrogen and oxygen by passing an electric current through it, is more beneficial in this respect.
The use of renewable energy sources to provide the electricity required is obviously a prerequisite for producing green hydrogen.
Advantages of hydrogen compared to other energy carriers
hydrogen produced by electrolysis makes it possible to chemically store large quantities of surplus, renewably generated electricity and subsequently use that stored energy at a later time.
Conversion into electricity in fuel cells or gas engines for stand-alone applications or for load peak balancing
Mixed directly with gas in the gas network, or used as pure hydrogen
Transported as hydrogen for use in industrial applications
Use as a fuel for vehicles equipped with fuel cell power trains
Challenges associated with exploiting hydrogen
Emissions released when producing hydrogen from fossil fuels
Lack of a nationwide supply infrastructure (e.g. hydrogen filling stations)
Costly storage of significant amounts of energy
Costs still relatively high