Hydrogen is not energy it is a way of storing energy just as fossil fuels are. Hydrogen is not widely present on the earth in large quantities energy, so it is necessary to manufacture hydrogen. Energy is released by either burning hydrogen to produce heat (similar to gas) or through combination with oxygen in a fuel cell to produce electricity.
Combination of hydrogen with oxygen forms water which is a harmless material, however burning hydrogen in air will produce nitrogen oxide NOXs which are a pollutant damaging air quality causing diseases in humans and also damage the ozone layer. Due to the faster speed of burning compared to natural gas, hydrogen actually releases higher quantities of NOX than gas, so is potentially more polluting.
Types of Hydrogen
It is possible to capture any pollutants produced in combustion processes, whether this is CO2 or NOX, however these are extra processes which require investment in suitable engineering, ongoing maintenance, ongoing input of energy to run the capture processes and either somewhere to “dump” the pollutant or a use for the pollutant. Removal of CO2 is talked about mainly as “carbon capture and storage” which envisages pumping CO2 at high pressure into underground storage (old oilfields), where the CO2 will be trapped for geological timescales. In the long term there is hope that this CO2 will be a raw material that will be used to make new materials, however any process must not be energy intensive as this would just create more energy demand.
Environmental Impact of Hydrogen
Hydrogen is often discussed in the same sentence as wind and solar energy, but this ignores a “big elephant in the room”. Whenever energy is transformed from one form to another the processes are not 100% efficient so energy is lost in every transformation. So some energy is lost when wind energy is translated to electrical energy, in terms of “green hydrogen” energy is lost when renewable energy used to manufacture hydrogen, energy is lost when the hydrogen to burnt to produce heat and if that heat is used to generate electricity then energy is lost when that heat is used to make electricity. In an internal combustion energy, whether the fuel is gas / petrol / diesel / hydrogen only about a maximum of 60% of the energy is turned into motive power, the rest is wasted as heat. Efficiency of an engine can be improved by using the heat, so a power station burning gas can also provide heat for local buildings.
How should hydrogen be used?
Hydrogen has been talked about for heating houses and powering cars, both of these uses have serious problems such as capture of pollutants and large energy losses which can’t be overcome in a million installations. However, a few large industrial installations could be engineered to capture pollution and improve efficiency – that extra engineering has both capital and running costs plus energy usage.
So hydrogen should be only used in situations where renewable energy can not be used directly such as heavy transport and industrial processes such as cement, chemical and steel making.
When the UK has a massive excess of renewable energy sources then hydrogen may have a role to level out the peaks and troughs of energy production. Hydrogen produced on sunny windy days could be either stored directly or combined with biomass to make synthetic fuels, which could then be used to generate electricity on dark windless nights.