Natural gas has traditionally been the fuel source for heating our homes, with 85% of UK dwellings having a gas connection. However, with domestic heating responsible for one-third of the UK’s carbon emissions, finding sustainable alternatives will be crucial for a greener tomorrow.
Many solutions exist to decrease carbon emissions and maximise energy efficiency in future homes, but doing the same for existing domestic dwellings provides a more complex challenge. The UK has an incredibly varied housing stock, ranging from detached and semi-detached properties to terraced homes and apartment blocks, with many unsuitable for heat pumps or district heating due to space or cost constraints.
Future-proofing our existing housing stock
According to the Office for National Statistics, a property’s age is the biggest factor in determining its energy efficiency – and the UK has one of the oldest housing stocks in Europe. One in six homes in England (15%) and a fifth of homes in Wales (23%) were built before 1900, while 46% of English homes and 39% of Welsh homes were built between 1930 and 1982. Homes built after 2012 are much more likely to have an EPC rating of C or above, representing only 7% of English and 5% of Welsh dwellings.
80% of the buildings that will exist in 2050 are already built. Therefore, the UK faces a big challenge to retrofit existing properties with low-carbon heating systems to meet net zero targets by 2050.
The limitations of heat pumps
Heat pumps are frequently cited as an efficient means of reducing a household’s energy bills and carbon emissions. Indeed, the Government’s Boiler Upgrade Scheme is intended to incentivise this technology’s uptake further.
Yet, according to the International Energy Agency, just 1% of UK buildings have a heat pump installed. Cost is likely a limiting factor. An air source heat pump typically costs between £6,000 and £13,000, depending on the model and size, whereas a ground source heat pump can range between £14,000 and £19,000.
And while the installation of heat pumps is beginning to increase in more rural areas, the technology does have some limitations for properties like terraced houses and flats, which account for 57% (13.6 million) of England and Wales housing stock, and are particularly concentrated in urban areas.
The limited available space in these homes can be a real issue. While the indoor unit of most heat pumps is similar to that of conventional boilers, air source heat pumps also require a bulky outdoor unit, while ground source ones need outside space for digging a borehole or trench.
Renewable energy supply vs demand
To decarbonise energy in its broadest sense, the government’s Net Zero Strategy has a strong focus on electrification – including heat pumps and EVs. The strategy also predicts that electrification will increase power demand by up to 60%. The challenges arising from this increase have to be considered, including how quickly capacity can be brought online to meet the new demands.
Renewable energy from solar and wind is inescapably intermittent and would need tremendous battery storage to maintain demand on overcast and still days or weeks. With battery technology some distance from meeting the scale needed, the UK can’t yet sustain itself on 100% renewable sources.
Currently, grid constraint is also an issue. When too much energy is being produced for the electricity grid to manage, wind turbines are switched off and renewable projects are put on hold. In 2020, when consumer demand fell as a result of the Coronavirus lockdown, National Grid spent an unprecedented £826 million balancing the grid, primarily in the form of payments to wind farms to cease generation.
Until the grid has been upgraded to support a growing number of renewable energy projects, we need an alternative low-carbon fuel to heat our homes. And whichever route is taken to decarbonising current gas demand, it will need to replace the 738TW of energy that natural gas produces annually.
The crucial role of hydrogen
As a low-carbon, clean gas, hydrogen represents a promising solution to decarbonise domestic heating with minimal disruption. Early trials proved that up to 20% hydrogen blends can be safely deployed into our existing gas network. The safety case for 100% hydrogen is currently being concluded, and trials are underway to supply 100% hydrogen to a neighbourhood, a village and potentially a town by the end of the decade, in line with the UK Government’s ten point plan for a Green Industrial Revolution.
Project Union – a project to connect hydrogen production centres to industrial, heat, transport and power consumers – is gaining pace. As a result, hydrogen could soon provide an answer to decarbonising properties like terraced houses and flats. Delivering a 2,000km hydrogen ‘backbone’ for the UK, Project Union will repurpose existing assets alongside new ones to create this infrastructure, which will represent around 25% of the UK’s current natural gas transmission pipelines.
This approach will be five times more cost-effective than building a completely new system, and will minimise the environmental impact of construction work. Using the existing gas network could also accelerate emissions reductions for domestic heating, as well as minimise consumer disruption and reduce unnecessary expenditure.
By getting a better understanding of consumer demand, the needs of the UK housing stock, and how to accommodate flexibility in the power system, government and energy industry stakeholders can work towards an energy transition that benefits all.