Carbon Budget Scenarios for Ireland Energy System to inform energy and climate policies delivered to CCAC CBWG, 2024-50

CARBON BUDGET ANALYSIS WITH THE TIMES-IRELAND MODEL (TIM)

Third iteration of modelling to support CCAC Carbon Budgets Working Group

Scenario assumptions

The TIM scenarios incorporate two types of carbon budget constraints for different periods:

(1) CB 2021-2050: This is the overall carbon budget constraint that sets the maximum allowable CO2 emissions from energy systems for the period 2021 to 2050.

Five different Carbon Budgets (CB) for the period 2021-2050 are modelled.

450Mt CO2

400Mt CO2

350Mt CO2

300Mt CO2

250Mt CO2

The specified amount reflects the limits in scenario names. For example, the 350Mt scenario assumes a maximum of 350 million tonnes of CO2 emissions from energy systems from 2021 to 2050.

(2) CB 2021-2030: This budget represents the maximum allowable CO2 emissions from energy systems for the period 2021 to 2030. In core scenarios, it is assumed that Sectoral Emissions Ceilings (SECs) are met, as outlined in the Table 3.2 Climate Action Plan. The total SECs for the periods 2021-2025 and 2026-2030 have a maximum limit of 275 Mt of CO2 and is fixed across all carbon budget scenarios, apart from WEM and WAM scenarios. In these scenarios, it is assumed that there is an overshoot of the SECs in the period to 2030 according to the emissions as projected by the Environmental Protection Agency, under current and planned policies.

The figure below shows the CB allocations for various scenarios. In the 250Mt scenario, the CB allocated for 2021-2030 is greater than the total budget for the entire period from 2021 to 2050. The model has limited ability to counterbalance emissions with a negative emissions technology, Bioenergy with Carbon Capture and Storage (BECCS). If in a given scenario the model cannot deliver a given carbon budget considering all the constraints applied, then a "backstop" negative emissions technology is deployed, at a cost of €2000 per tonne of CO2.

Core scenarios

These scenarios have an overall carbon budget of 250Mt to 450Mt applied from 2021 to 2050. All five CB scenarios are modeled using a business-as-usual (BAU) demand projection and do not have a suffix, such as "250Mt".

Other scenarios

Low Energy Demand (LED): Four of the lower CBs are modelled using a LED projection. They have LED suffixes such as "250Mt-LED". For the detailed assumptions of LED scenarios see Gaur et. al (2022) Article.

WAM & WEM: In these scenarios, emissions projections from the Environmental Protection Agency are used as the lower bound for emissions in the pre-2030 period.

However, the overall CBs remain the same for the 2021-2050 period, using BaU energy demand projections. For example, "350Mt-WEM" indicates an overall carbon budget of 350 million tonnes for 2021 to 2050 and 310 million tonnes for 2021 to 2030.

LowBio: This scenario group restricts biomass imports to current levels, and no increase is allowed beyond the existing import levels, such as "250Mt-LowBio"

HighSolarPV: This scenario significantly increases solar PV adoption, with the maximum allowable capacity rising from 10GW in the core scenarios to 18GW.

Acknowledgements 

We acknowledge and are grateful for the contributions of past and current members of UCC’s Energy Policy and Modelling Group, particularly those who contributed to the development of TIM and its predecessor, the TIMES-Ireland Model. We are also thankful to the CCAC and members of the CBWG, particularly SEAI’s energy modelling team and Prof. John FitzGerald, for constructive feedback on previous iterations of this research, and others who provided comments on the draft report. This research was part-funded by the Department of Environment, Climate and Communications through the CAPACITY project - Climate and Energy Modelling Services to the Climate Action Modelling Group (CAMG) (grant no. RFT2022/S 164-466018).