ORKNEY'S ENERGY FUTURE
DOMESTIC HEATING
BACKGROUND
HOUSING STOCK
The most recent figures for household estimates in Orkney show that there are 11,308 homes and 10,155 households. The difference between these figures is due to the high prevalence of vacant homes (6%) and second homes (4%) [1].
Orkney has a high proportion of older properties within its housing stock; the percentage of pre-1919 homes is as high as 49% in the Isles (all islands outside of Mainland Orkney), compared to only 19% of homes in Scotland [2]. There is a disparity in the age of the housing stock between different areas (Figure 1). This contributes to the variation in levels of fuel poverty, as older homes tend to be larger and therefore consume more energy, especially those in rural areas such as the Isles [3].
Figure 1: Age band of properties in different areas of Orkney using data from Orkney’s Fuel Poverty Strategy 2017-2022 [2].
FUEL POVERTY
The rate of fuel poverty in Orkney is more than double that of Scotland (57% and 25%, respectively) [4] [3]. Orkney Islands Council attributes this to five main factors [2]:
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Older housing stock
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Below average income
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High cost of heating homes
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Orkney’s climate
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Household lifestyle choices
There is a clear link between age of property and level of fuel poverty experienced (Figures 2 and 3). These maps also highlight that the proportion of homes suffering from fuel poverty in the Orkney Isles is greater than that of Mainland Orkney.
Figure 2: Percentage of properties built pre-1919 by data zone.
Figure 3: Percentage of households living in fuel poverty by data zone.
FUEL TYPES
There is no gas network in Orkney [5] and therefore no gas central heating. The 2011 Scotland Census showed that 44% of homes in Orkney used an electric form of heating, with the remainder being heated using either oil (46%) or solid fuels, such as coal (8%) [6].
However, the proportion of electrically heated homes is likely to have increased since 2011 [7]. Therefore, current figures for fuel types were estimated based on the assumption that:
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All new homes built since 2011 are electrically heated.
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Of all the Domestic Renewable Heat Incentive (RHI) installations in Orkney, 61% were previously oil-heated homes being fitted with heat pumps (based on UK average statistics) [8].
Figure 4: Breakdown of fuels used for heating of domestic buildings in Orkney.
Based on there being 10,155 households in Orkney and 48.6% using non-electric heating (Figure 4), this means approximately 4,900 homes require their heating system to be decarbonised.
DECARBONISATION TECHNOLOGY
The technologies considered for decarbonising domestic heating were solar thermal, hydrogen (H₂) boilers and ground source (GSHP) and air source heat pumps (ASHP). These options were given scores based four criteria (Table 1):
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Capital cost of installation
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CO₂ savings associated with installation of the technology
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Ease of installation
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Extra space required for the new system
Table 1: Decision matrix used to score potential decarbonisation technologies on different criteria.
The main considerations when completing the decision matrix were as follows:
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Cost is not as important as CO₂ savings because initial costs will be compensated for by the Domestic RHI.
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Solar thermal will require a back-up system for days when there is low solar irradiation and therefore will have lower CO₂ savings in comparison to other technologies.
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Using H₂ boilers will create complications as there is currently no gas network.
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The space required for a GSHP is considerable (~700 m² [9]) and may not be feasible for all homes.
Based on this, ASHPs are the preferred technology and will be used to model the decarbonised domestic heating electricity demand.
REFERENCES
[1] Scottish Government, "Household Estimates," National Records of Scotland, [Online]. Available: https://statistics.gov.scot/data/household-estimates. [Accessed 6 April 2021].
[2] Orkney Islands Council, "Orkney's Fuel Poverty Strategy 2017-2022," Orkney Islands Council, 2017.
[3] Scottish Government , "Scottish House Condition Survey: 2019 Key Findings," National Records of Scotland, 2020.
[4] Orkney Renewable Energy Forum, "Fuel Poverty," [Online]. Available: https://www.oref.co.uk/orkneys-energy/fuel-poverty/#:~:text=In%20Orkney%2C%20as%20of%202018,(figures%20provided%20by%20THAW).. [Accessed 6 April 2021].
[5] Aquatera, "Orkney-Wide Energy Audit 2014: Energy Sources and Uses," Orkney Renewable Energy Forum, 2015.
[6] National Records of Scotland, "Scotland's Census 2011," Scottish Government, 2011. [Online]. Available: https://www.scotlandscensus.gov.uk/census-results. [Accessed 6 April 2021].
[7] L. Fraser, Interviewee, Central Heating Types by Area. [Interview]. 22 February 2021.
[8] Department for Business, Energy and Industrial Strategy, "RHI deployment data: January 2021," UK Government, 2021.