A cogeneration thermal power plant in Ferrera Erbognone, Italy.

A cogeneration thermal power plant in Ferrera Erbognone, Italy. Credit: Mattia Luigi Nappi.

UK heating must be virtually zero-carbon by 2050, says the Committee on Climate Change (CCC).

Options to reach this goal include district heating schemes, low-carbon hydrogen in the gas grid and electric heat pumps, the CCC says, in a new report on decarbonising heat. Each option poses problems and will take time to develop.

Yet deployment cannot wait until the 2030s, the committee says. It must start now in order lay the groundwork for roll-out later on. The UK also needs a new approach to improving energy efficiency, the CCC says, which could include direct regulation of home performance.

Carbon Brief sets out the challenge of heat and the options for reaching near zero carbon.

Challenge

The UK is legally bound to cut its emissions 80% below 1990 levels by 2050. At some point, in order to comply with the Paris Agreement, it will need to reach net-zero emissions. (See Carbon Brief coverage of what the Paris Agreement means for the UK’s climate targets).

The 2050 limit only leaves space for the hardest-to-eliminate emissions, such as those from aviation, industry and farming. As a result, UK heat must be virtually decarbonised by 2050.

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Provisional UK greenhouse gas emissions in 2015, by sector (left hand column). The 2050 target and expected emissions from hard-to-treat sectors (right hand columns). Source: Next Steps for UK Heat Policy, Committee on Climate Change.

Today, the heating and hot water needs of UK buildings account for 40% of energy use and 20% of greenhouse gas emissions. “It will be necessary to largely eliminate these emissions by around 2050,” the CCC says.

Adding to the problem is the strongly seasonal need for heat energy. UK electricity demand varies between lows of around 30 gigawatts (GW) and highs of a little more than 50GW. In contrast, heat energy demand ranges from lows of 25GW in summer to peaks of 300-350GW in winter.

Demand for heat and electricity in the UK. Source: Managing Heat System Decarbonisation, Imperial College Centre for Energy Policy and Technology.

Demand for heat and electricity in the UK. Source: Managing Heat System Decarbonisation, Imperial College Centre for Energy Policy and Technology.

Zero-carbon alternatives to the UK’s predominantly gas-fired UK heating infrastructure would, therefore, need to be able to meet peak demand some five or six times higher than peak power demand. This would be eased if there were a way to store zero-carbon energy across seasons.

The challenge of decarbonising heat is amplified by the lack of clear technological solutions.

At a briefing for journalists, Lord Deben, CCC chair said:

“The two areas where we have not achieved very much [on cutting UK CO2 emissions] are in construction and transport. With transport you can see very clear technological advances which might well contribute the ability to do that. In construction it is obviously true that we’ve still got millions of houses which have not been made as efficient as they could be, and we are still building houses which we’re going to have to retrofit in a very short period of time.”

Options

The CCC identifies three main options for decarbonising heat supplies. The first is low-carbon district heat networks, most suitable for densely populated cities. These can use waste heat, large-scale heat pumps that draw warmth from rivers and potentially hydrogen, the CCC says.

The government has earmarked £320m for investment in heat networks out to 2020. The level of ambition this represents would have to be scaled up in the 2020s, the CCC notes. Building heat networks can be highly disruptive because it requires pipes in the ground.

The second option is heat pumps powered with zero-carbon electricity. Enthusiasm for heat pumps is low in the UK, even though they are widely used in many other countries, the CCC says. A recent report for thinktank Policy Exchange said heat pumps were costly and disruptive to install.

Installations are running at around 20,000 a year. To decarbonise heat using heat pumps alone, this figure would need to rise 50-fold to 1 million a year from the mid-2030s, the CCC says. It would also necessitate heavy investment in additional zero-carbon electricity generating capacity.

The third option is to repurpose the existing gas grid with hydrogen. This would involve less disruptive changes for households but would necessitate a zero carbon source of hydrogen, with uncertain costs.

Hydrogen could be produced from gas, alongside carbon capture and storage (CCS), as advocated by the UK shale gas industry. “Before a decision to proceed with hydrogen, it would be essential that CCS is under active development in the UK,” the CCC says.

Alternatively, hydrogen could come from electrically-driven hydrolysis, though the CCC notes that this would once again impose a heavy burden on electricity supplies.

All of these options for low-carbon heat are imperfect, as the grid below shows. In a paper on the future of energy systems governance, energy regulator Ofgem says:

“Conversion of heating to either district heat or hydrogen will require coordination and restrictions on choice – it will probably not be possible for individual households to choose whether or not to join the new network.”

Costs and impacts of options for low-carbon heat. Source: Managing Heat System Decarbonisation, Imperial College Centre for Energy Policy and Technology

Costs and impacts of options for low-carbon heat. Source: Managing Heat System Decarbonisation, Imperial College Centre for Energy Policy and Technology

Action

These challenges are daunting and it will take time to develop new strategies, governance arrangements and pilot schemes so as to evaluate the costs and benefits of each option.

The CCC says:

“At present the best balance between hydrogen and heat pumps, alongside heat networks, is unknown. More evidence is required about costs, industry’s capacity to deliver and preferences of households and business.”

It adds:

“Government must set out the role of hydrogen for buildings on the gas grid in the next parliament…It will have to decide on whether there is a role for hydrogen…alongside other technologies such as heat pumps.”

Meanwhile, there is much that must be done in the interim in order to keep on track with the UK’s climate goals, the CCC says. A 2016 report on heat from Imperial College says:

“Decarbonising heat at scale will need to be well underway by the 2030s and continue beyond 2050 to meet the legally binding carbon reduction targets set in the Climate Change Act.”

The government’s ambition to install a million energy efficiency measures during this parliament is completely out of step with the requirements set out by the CCC. It says that seven million lofts and cavity walls should be insulated by 2030, at a rate some 2.5-fold faster than current efforts.

One option would be to extend existing regulations on minimum energy efficiency requirements for private rented accommodation. A report on decarbonising heat from the UK Association for the Conservation of Energy says government “must bite the bullet” by setting mandatory minimum energy efficiency standards for all buildings, at the point of sale.

The CCC’s report floats the idea of standards for the emissions performance of buildings that would tighten over time but stops short of recommending regulation. Lord Deben told journalists:

“[Improving energy efficiency] is something that has to be done if you are going to meet your targets…It is for government to decide the mix between regulation and incentives.”

Conclusion

Decarbonising heat will be a vital piece of the puzzle if the UK is to meet its climate targets and comply with the Paris Agreement. It’s a daunting challenge with a range of possible solutions.

All of the options present problems, from disruptive infrastructure or home retrofit needs to potentially high costs or requirements for much more extensive roll-out of zero-carbon power.

Yet the time needed to resolve some of these issues must not be wasted, the CCC says, since many investments make sense now regardless of the path we choose in future. Chief among those is energy efficiency, without which the already steep challenge of heat would become harder still.