Hannah Daly

Indirect CO2 Emission Implications of Energy System Pathways: Linking IO and TIMES Models for the UK

Radical changes to current national energy systems-including energy efficiency and the decarbonization of electricity-will be required in order to meet challenging carbon emission reduction commitments. Technology explicit energy system optimization models (ESOMs) are widely used to define and assess such low-carbon pathways, but these models only account for the emissions associated with energy combustion and either do not account for or do not correctly allocate emissions arising from infrastructure, manufacturing, construction and transport associated with energy technologies and fuels. This paper addresses this shortcoming, through a hybrid approach that estimates the upstream CO2 emissions across current and future energy technologies for the UK using a multiregional environmentally extended input-output model, and explicitly models the direct and indirect CO2 emissions of energy supply and infrastructure technologies within a national ESOM (the UK TIMES model). Results indicate the large significance of nondomestic indirect emissions, particularly coming from fossil fuel imports, and finds that the marginal abatement cost of mitigating all emissions associated with UK energy supply is roughly double that of mitigating only direct emissions in 2050.

National climate policy implications of mitigating embodied energy system emissions

Rapid cuts in greenhouse gas emissions require an almost complete transformation of the energy system to low carbon energy sources. Little consideration has been given to the potential adverse carbon consequences associated with the technology transition. This paper considers the embodied emissions that will occur to replace the UK’s fossil fuel-reliant energy supply with low carbon sources. The analysis generates a number of representative scenarios where emissions embodied in energy systems are integrated within current national climate and energy policy objectives. The embodied emissions associated with a new low carbon energy system are lower than the emissions reduction associated with the low carbon energy sources, confirming that there is a carbon return on investment. However, even if the UK reaches its 2050 territorial climate target, it is estimated that by 2050 an additional 200 Mt CO2 emissions are generated overseas (compared to 128 Mt generated within the UK) in the production of imported fuels and infrastructure components. The cost-optimal model results suggest that more electrification would need to occur, supported by nuclear energy, mainly in replacement of natural gas to mitigate these emissions. However, due to a number of deployment barriers, other policy interventions along the energy supply chain are likely needed, which are discussed alongside the model results. There could be more emphasis on an absolute reduction in energy demand to reduce the scale of change needed in supplying energy; new business models oriented towards performance and not sales; and existing trade schemes and international effort-sharing frameworks could be extended.

Modal Shift of Passenger Transport in a TIMES Model: Application to Ireland and California

Climate change mitigation clearly requires a focus on transport that should include improved representation of travel behaviour change in addition to increased vehicle efficiency and low-carbon fuels. Energy system models focus however on technology and fuel switching and tend to poorly incorporate travel behaviour. Conversely, transport demand modelling generally fails to address energy and climate policy trade-offs. This chapter seeks to make energy systems analysis more holistic by introducing modal choice within passenger transport in a TIMES model, to allow trade-offs between behaviour and technology choices explicit. Travel demand in TIMES models is typically exogenous—no competition exists between alternative modes. A simple illustrative TIMES model is described, where competition between modes is enabled by imposing a constraint on overall travel time in the system. This constraint represents the empirically observed travel time budget of individuals, constraining the model choosing between faster and more expensive modes (e.g. cars) and slower but cheaper mode (e.g. buses or rail). Further, a new variable is introduced, called travel time investment, which acts as a proxy for infrastructure investments to reduce the time associated with travel, to enable investment in alternative modes of transport as a means of CO2 mitigation.