Installation & deployment of hydrogen vs. ground source
The greatest attraction of hydrogen is that, hypothetically, it could have the potential to flow through the existing gas network – supposedly minimising change for consumers, replacing gas and decarbonising heat across the UK. It’s not as easy as it sounds though. Vitally, the greatest obstacle is that there is no proven blueprint for this conversion. In fact, the UK would have to pioneer this; as of 2020, not one place in the world supplied pure hydrogen to homes or businesses.³
A dedicated study into hydrogen and heat decarbonisation suggests it’s unlikely that zero-carbon hydrogen supplied via a repurposed mains network will be available for the foreseeable future. There are a number of reasons to support this: it could be a major delivery risk to incorporate a new infrastructure for an unproven technology on a large scale and it is unclear who will guarantee and accept liabilities for in-building gas pipework switchover.4 The mass deployment of hydrogen relies on numerous issues being solved – if we wait for the technology to be ready but all of these issues cannot be solved, the delay could be detrimental to the planet.
What happens in the next decade could be the measure of success or failure in achieving net-zero carbon. The longer we wait for hydrogen to create a solid solution, the closer we are to the tipping point.
Without further delay in the journey to decarbonisation, we see a great role for hydrogen alongside ground source heat pumps: to produce electricity and low-grade heat when the local grid is under strain. A hydrogen-powered fuel cell or generator could be connected to a Shared Ground Loop Array. This fuel cell can deliver electricity into the grid around, say, 10% of the time in rare cases when wind and solar output is low. As well as this, the waste heat that comes out of the fuel cell can be delivered into the ground array, which improves the efficiency of the heat pumps and reduces electrical demand all at once.
Rather than competing, the two technologies can in fact work together – with hydrogen improving the efficiency of the ground source heat pump system further and vice-versa. Hydrogen is going to be expensive to make; it makes sense to burn the expensive hydrogen during low renewable generation periods and only support the grid when it really needs it.
Heat pumps are ready to be deployed now. Compared to gas, they can already reduce carbon emissions by 77% in properties. As we build more and more renewable electricity generation onto the grid, the carbon savings will continuously improve – and there will be no need to revisit the properties in order to reach net-zero carbon.
In Kensa’s view, the key to the mass deployment of ground source heat pumps is the ground array infrastructure. The low-carbon alternative to traditional district heating, Shared Ground Loop Arrays, can be implemented on a street-by-street basis, mimicking the gas network and connecting to heat pumps in individual homes. An ambient temperature circulates around the distribution pipework at -5°C to 20°C, with each heat pump upgrading the heat to the required temperature for heating and hot water.
This will need infrastructure and investment in the electric grid and in the low-carbon generating technology attached to it, but nowhere near as much as you might think. Grid balancing concepts such as local energy storage, grid-storing batteries and ‘load shifting’, which a ground source heat pump can do when coupled with smart controls, will reduce strain on the grid as more and more heat pumps are deployed.
As for the installation training itself, the skills challenge is surmountable and the skills of gas heating installers are certainly transferable to heat pumps. This is particularly true once you separate out the ground array district infrastructure elements from what happens in the house, in the same way as we currently do for gas infrastructure and boiler installation. All in all, both options present a challenge and change to the way we heat our homes, but it’s certainly worth the momentary disruption that is inevitable in the stretch to net zero.