Date Published: May 2022
The Hydrogen Distraction
Nicola Terry, of Cambridge Carbon Footprint, has blogged about Heat pumps or hydrogen: How to decarbonise heating”. We recommend you read her blog, including useful references, in full. She explains why hydrogen is not a sensible option for heating homes.
This page summarises her key points.
Blue hydrogen has at best a third of the carbon emissions of fossil gas
The processes to make hydrogen from methane are well developed and could be scaled up fairly easily. The processes for capturing and storing the carbon are reasonably well developed, though we have done very little storage so far. Still, “blue hydrogen” is not as clean as we need and is not compatible with Net Zero. It is impossible to capture all the carbon and even if you did, there is always some methane leakage at the gas well and on the way to the processing plants. Methane is a major greenhouse gas, with a global warming potential 56 times that of CO2 over 20 years. Estimates of the GHG emissions of blue hydrogen are about half that of natural gas. Some estimates are more favourable – about a third. So taking the blue hydrogen route only reduces emissions by two thirds, at best.
Green hydrogen would need five times more wind farms than heat pumps
We have long known how to make hydrogen from water by using renewable electricity and electrolysis but the efficiency has been poor until recently. Now, after a lot of research we are up to about 80%. Further development would be useful to run the process intermittently, when there is spare power available cheaply. At the moment, we only have spare power occasionally, but this will be more common as we increase our wind and solar power generation.
The real trouble with this approach is that, in comparison with heat pumps, our boilers are terribly inefficient. This chart shows the difference. With boiler efficiency around 86%, compared to heat pumps at 280% (a conservative estimate) it is better to use the hydrogen in a power station to generate more electricity for driving heat pumps than it is to burn it in your boiler. If we were to run our boilers on green hydrogen from electricity, rather than using the electricity directly in a heat pump we would need five times as much electricity.
All gas appliances would need to be converted to burn hydrogen
Our boilers and other gas appliances would all need converting or replacing. This is because hydrogen ignites and burns differently from methane. Safety is critical and we cannot afford to make mistakes.
Converting the gas grid to hydrogen cannot start until all appliances converted
Converting the gas grid needs to be done a segment at a time. For each segment, we would need to shut off the gas, convert the appliances, and turn it on again. To make this practical, all the equipment needs to be ‘hydrogen ready’, so that engineers can do the adjustments or fit the new parts quickly.
There will be a place for hydrogen – but not for home heating
Hydrogen cannot be produced sustainably or economically at sufficient scale to replace all our gas heating, and even if it could, it would take too long to convert the gas grid to hydrogen. However, there will be a place for hydrogen in the zero carbon economy. It will be needed for some industrial processes that currently use gas, where heat pumps are not suitable (for example where high temperature heat is needed).
Heat pumps are available now
Heat pumps are an easier solution because they can run on renewable electricity, they are very efficient and they are available now.
Heavy lobbying from the oil and gas industry is stalling government policy
Unfortunately, the government is subjected to heavy lobbying from the oil and gas industry and the gas boiler industry who stand to lose an awful lot of business as we move over to heat pumps instead. Their campaign aims to persuade officials that the switch to heat pumps will be unpopular and expensive. However, this does not mean that the hydrogen approach is better, or affordable, or as low in carbon.