ORKNEY'S ENERGY FUTURE
RESULTS
CO2 SAVINGS
The 2019 Orkney energy audit [1] and UK Government [2] reports of energy demand per fuel type was used to calculate the annual CO₂ emissions of the current energy system (Table 1). The 2019 audit is based on data from 2018. Conversion data from the UK Government were used to convert the energy use into tonnes of CO₂ emitted [3]. Electricity drawn from the National Grid was considered to have associated CO₂ emissions. However, only 1.8% of Orkney’s electricity was imported in 2018; the remainder 98.2% of electricity was assumed to be generated by renewable sources on Orkney and therefore have zero emissions. The emission intensity used for electricity was 0.085 kgCO2₂/kWh, the average daily National Grid intensity for Northern Scotland in 2020 [4]. Total CO₂ emissions were calculated to be 149 kilo tonnes (kt CO₂).
Table 1: Orkney energy consumption and CO₂ emissions of fuels based on 2018 energy use.
The CO₂ emissions saved for each sector (Domestic Heating, Road Transport and Marine Transport) per year between 2021 and 2030 based on the suggested implementation timelines were calculated. The carbon intensity of the National Grid for these years was assumed to be 0.050 kgCO₂/kWh [5]. In 2030, there would be a 40.9% reduction in emissions from 149 to 88.1 kt CO₂ for Scenario 1.
If batteries are not used when the demand is greater than supply then electricity would be imported from the National Grid at amounts that were calculated to be different for Scenarios 2a and 3a and 2b and 3b. Therefore, CO₂ emissions in 2030 were also calculated to be different, but the difference is considered to be negligible (Table 2).
Table 2: Electricity sourced from National Grid and resulting CO₂ emissions for all scenarios.
Although not being proposed by the implementation timeline, it has been calculated that the surplus electricity in Scenario 2b would be sufficient provide the hydrogen fuel required for the two Aberdeen-Kirkwall-Lerwick ferries. Considering the ‘Orkney contribution’ of these ferries only [6], the reduction in CO₂ emissions in 2030 would be 47.2% from 149 to 78.7 kt (Figure 1).
Figure 1: Graph showing the reduction in CO₂ emissions per sector and resulting overall CO₂ emissions of the energy system after decarbonising chosen sectors.
Using capital costs presented in the Domestic Heating, Road Transport and Marine Transport sections, the capital expenditure to decarbonise each sector was calculated to determine which would be the most cost-effective (Table 3).
Domestic heating was found to be the most cost-effective sector to decarbonise as it has the lowest expenditure per kt CO₂ saved (Figure 2). If all petrol and diesel vehicles were replaced with EVs in future, cars were found to be the most expensive sector to decarbonise.
Table 3: Capital cost and CO₂ emissions saved per sector.
Figure 2: Comparison of capital expenditure to save 1 kt CO₂. Domestic heating is the most cost-effective sector to decarbonise.
AVAILABLE DOWNLOADS
The spreadsheet with the CO₂ savings calculations is available here.
REFERENCES
[1] Orkney International Science Festival, "Orkney's Energy Revoution: Hydrogen & Energy Systems," YouTube, 3 September 2020. [Video File]. Available: https://www.youtube.com/watch?v=TCfYGdsSXSc&t=2389s. [Accessed 1 February 2021].
[2] UK Government, "Road transport energy consumption at regional and local authority level," 25 June 2020. [Online]. Available: https://www.gov.uk/government/statistical-data-sets/road-transport-energy-consumption-at-regional-and-local-authority-level. [Accessed February 2021].
[3] UK Government, "Greenhouse gas reporting: conversion factors 2018," 18 July 2018. [Online]. Available: https://www.gov.uk/government/publications/greenhouse-gas-reporting-conversion-factors-2018. [Accessed 22 March 2021].
[4] Nuclear Industry Association, "Scotland has UK’s cleanest power mix in 2020," 18 December 2020. [Online]. Available: https://www.niauk.org/media-centre/press-releases/scotland-uks-cleanest-power-mix-2020/. [Accessed 29 March 2021].
[5] Scottish Government, "Climate Change Plan Monitoring Report," December 2019. [Online]. Available: https://www.gov.scot/publications/climate-change-plan-monitoring-report-2019/pages/3/. [Accessed 29 March 2021].
[6] Orkney Renewable Energy Forum, "Orkney-Wide Energy Audit 2014 Addendum," August 2015. [Online]. Available: https://www.oref.co.uk/wp-content/uploads/2015/09/Orkney-wide-energy-audit-2014-Addendum-2015.pdf. [Accessed March 2021].