Hydrogen economy

What is it? In the context of the energy transition, the hydrogen economy is a systemic proposal for the supply of energy to the economy. It refers to a vision of the future using hydrogen (_H2) as a low-carbon energy source. It currently has different applications, such as storage vector or renewable energy recovery, as a complement to natural gas, fuel (e.g. replacing gasoline for transport, or natural gas for heating) or other applications associated with stationary or mobile fuel cells. It is considered an attractive energy vector, given:

 

• Offer a high energy density per unit mass (33kWh/kg) – i.e. three times more energy per unit mass than gasoline, and 2.5 times more than natural gas; it should be borne in mind, however, - as a disadvantage, its transport is ineffective in offering a low energy density per unit volume, being less dense 15 times and 3 times that of oil and natural gas, respectively for comparable pressure and temperature conditions;
• Water (H2O) is the sole product of the reaction when processed to produce heat, or combined with oxygen from the air to produce electricity in a fuel cell.

 

On Earth, although there is hydrogen in large quantities in combined form with other elements, hydrogen in elemental form is extremely rare. It therefore means that - when necessary, it is necessary to produce it, using energy to dissociate it from different compounds, such as natural gas, biomass, some alcohols or water.

 

 

For this reason, its impact on the greenhouse gas emissions balance depends on a carbon footprint per energy unit produced – along its value chain, and subsequent end-use. It is currently produced predominantly from natural gas, and in this condition, a car with a fuel cell generates 70-80g CO2 per km travelled – similar to a modern hybrid petrol vehicle, or an electric vehicle with a battery charged with current grid electricity. The resulting emissions can be reduced to close to zero if H2 is produced by electrolysis of water using renewable electricity sources, or carbon capture and storage (CCS).