Heating our buildings without creating greenhouse gas emissions is vital in reaching net-zero. In this blog ClimateXChange research fellow Jonathan Bowes looks at the Scottish domestic heat targets, and options for reaching them.
Heat demand currently makes up over 50% of final energy demand in Scotland1 and decarbonising heating will be vital to meeting the governments legally binding target of a 75% reduction in emissions by 20302.
Total final energy consumption by sector 2019: transport 24.7%, heat 50.7%, electricity 21.6%, other 3.0%. Source: BEIS
Long description ends.
There are a number of ways to achieve zero emission heating. These include;
- replacing natural gas boilers with hydrogen created from low carbon electricity;
- using direct electric heating or heat pumps in houses;
- burning sustainable biomass; or
- connecting houses to heat networks supplied by any of the three heat sources above.
The Scottish Government Hydrogen Policy Statement sets out the intention to generate 5GW of renewable and low-carbon hydrogen by 2030. How and where this hydrogen will be used is uncertain.
Hydrogen (H2) production is expected to ramp up - particularly in the north east of Scotland -with projects like H2 Aberdeen pioneering Hydrogen buses and development of Acorn hydrogen. However, if hydrogen production is slow to take off, it may mean it could have a limited impact in terms of meeting Scotland’s 2030 heat ambitions . Similarly, it may be that biomass will likely be reserved for sectors other than heating, and the capacity for production in Scotland currently falls far short of the heat demand. If hydrogen and bioenergy are unable to make a significant contribution to the 2030 heat target, this would mean that heat networks and heat pumps, using electricity mostly supplied by renewables, are likely to be the most suitable solutions for decarbonising domestic heat.
The challenge therefore is to determine a pathway that is balanced between short term and long term decisions. Choices made now must be on the basis of meeting the 2030 target while accounting for the uncertainty beyond 2030. This will require “low regret” options concerning technology choices for heating to be made to off-set climate change risks.
There are two types of “low regrets'' choices that could be prioritised for retrofit:
- The first is installing heat pumps in houses burning heating oil or LPG that are not connected to the gas grid (around 170,000 in Scotland3). If hydrogen does become a dominant vector for heat, it will be distributed by existing gas network, but this network is very unlikely to be expanded to connect remote houses that are not connected now. In addition, LPG and heating oil emit far more CO2e for equivalent heat supply than natural gas, further incentivising targeting these properties first to meet emissions reductions targets.
- The second low regret choice is developing heat networks in areas with a high density of heat demand. These networks offer a cost effective solution in locations with concentrated heat demand such as blocks of flats or offices and can make use of heat obtained from rivers, waste industrial heat and even mine water geothermal energy. These sources would be coupled with large industry scale heat pumps and could be supplemented with hydrogen heating in the future if that becomes a feasible long term solution.
Reaching the 2030 targets
So how does all of this stack up? How close to the 2030 targets do these low regrets options get us? The total emissions budget for buildings in 2030 is 2.6 MtCO2e4, compared to 8 MtCO2e in 2020. Based on published documents from Scottish Government, the pathway to achieve the heating element of these reductions looks like this:
- Almost all off gas grid domestic properties using oil or LPG will be converted to zero emissions heating (170,000) - likely to be mostly air source heat pumps.
- In addition to all high emissions off gas properties, least 1 million additional domestic properties currently connected to the gas grid and 23% non-domestic properties (50,000) will need to convert to zero emissions heating5 by 2030.
- 6 terrawatt hours (TWh) of heat will be supplied by heat networks annually by 2030 (equivalent to 400,000 - 600,000 average houses depending on size) across both domestic and nondomestic heat demand. This is a statutory requirement of the recently passed Heat Network Act
- From 2024, all new build properties will use zero carbon heating6
To reach an estimate of the number of installed heat pumps, we can remove the heat network suitable properties from the total of 1.167 million properties, giving between 517,000 and 717,000 domestic properties required to install heat pumps by 2030 to meet the climate targets. There may be the opportunity to reduce that number through the use of hydrogen, if both the production of hydrogen develops quickly and we find ways to convert parts of the gas network to deliver 100% hydrogen to homes.
Scaling up the roll-out
The proposed pathway is clearly challenging. Currently Scotland installs 3000 low carbon domestic heating systems a year across all technology types. To meet these targets, that rate must quickly ramp up over the next few years.
All of this will require huge amounts of work - digging up roads to lay pipes for heat networks and new hydrogen ready gas pipes, upgrading electricity networks, training new engineers, and building technology supply chains. We also need to reconcile the large upfront costs of heat pumps compared to gas boilers, and ensure that vulnerable and fuel poor consumers are protected.
3) Scottish Government. (2020), Scottish Household Survey (2019), Table 3.1., (Scottish Government), URL: https://www.gov.scot/publications/scottish-household-survey-2019-annual-report/ (last accessed: 20/06/2021).
4) Update to the Climate Change Plan 2018 - 2032: Securing a Green Recovery on a Path to Net Zero, page 253, https://www.gov.scot/publications/securing-green-recovery-path-net-zero-update-climate-change-plan-20182032/documents/