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    ABSTRACT: Energy system models are often used to assess the potential role of hydrogen and electric powertrains for reducing transport CO2 emissions in the future. In this paper, we review how different energy system models have represented both vehicles and fuel infrastructure in the past and we provide guidelines for their representation in the future. In particular, we identify three key modelling decisions: the degree of car market segmentation, the imposition of market share constraints and the use of lumpy investments to represent infrastructure. We examine each of these decisions in a case study using the UK MARKAL model. While disaggregating the car market principally affects only the transition rate to the optimum mix of technologies, market share constraints can greatly change the optimum mix so should be chosen carefully. In contrast, modelling infrastructure using lumpy investments has little impact on the model results. We identify the development of new methodologies to represent the impact of behavioural change on transport demand as a key challenge for improving energy system models in the future.
    International Journal of Hydrogen Energy 02/2014; 39(5):2345–2358. DOI:10.1016/j.ijhydene.2013.11.021
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    ABSTRACT: Critical energy policy decisions rely on expert assessments of key future uncertainties. But existing modelling techniques that help form these expert assessments often ignore the existence of uncertainty. Consequently, techniques to measure these uncertainties are of increasing importance. We use one technique, expert elicitation, to assess six key uncertain parameters with 25 UK energy experts across academia, government and industry. We obtain qualitative descriptions of the uncertain parameters and a novel data set of probability distributions describing individual expert beliefs. We conduct a sensitivity analysis on weights for a linear opinion pool and show that aggregated median beliefs in 2030 are: for oil price $120/barrel (90% CI: 51, 272); for greenhouse gas price $34/tCO2e (90% CI: 5, 256) and for levelised cost of low-carbon electricity 17.1 US cents/kWh (90% CI: 8.3, 31.0). The quantitative results could inform model validation, help benchmark policy makers’ beliefs or provide probabilistic inputs to models.
    Energy Policy 10/2013; 61:811–821. DOI:10.1016/j.enpol.2013.06.110
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    ABSTRACT: The UK Government has unveiled an ambitious retrofit programme that seeks significant improvement to the energy efficiency of the housing stock. High quality data on the energy efficiency of buildings and their related energy demand is critical to supporting and targeting investment in energy efficiency. Using existing home improvement programmes over the past 15 years, the UK Government has brought together data on energy efficiency retrofits in approximately 13 million homes into the Homes Energy Efficiency Database (HEED), along with annual metered gas and electricity use for the period of 2004–2007. This paper describes the HEED sample and assesses its representativeness in terms of dwelling characteristics, the energy demand of different energy performance levels using linked gas and electricity meter data, along with an analysis of the impact retrofit measures has on energy demand. Energy savings are shown to be associated with the installation of loft and cavity insulation, and glazing and boiler replacement. The analysis illustrates this source of ‘in-action’ data can be used to provide empirical estimates of impacts of energy efficiency retrofit on energy demand and provides a source of empirical data from which to support the development of national housing energy efficiency retrofit policies.
    Energy Policy 09/2013; 60:462–480. DOI:10.1016/j.enpol.2013.04.004
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    ABSTRACT: This paper critically reviews the growing literature optimising hydrogen infrastructure. We examine studies across spatial scales: national scale studies using energy system models; regional scale studies optimising spatially disaggregated hydrogen infrastructure; and local scale studies optimising the siting of filling stations. For the latter two types of study, we critically assess the assumptions made around hydrogen demand, a key exogenous input into these studies. We identify knowledge gaps and issues that have not been sufficiently addressed in the literature, and we suggest areas for further work.
    International Journal of Hydrogen Energy 05/2013; 38(13):5181–5191. DOI:10.1016/j.ijhydene.2013.02.042
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    ABSTRACT: Both fuel cell and electric vehicles have the potential to play a major role in a transformation towards a low carbon transport system that meets travel demands in a cleaner and more efficient way if hydrogen and electricity was produced in a sustainable manner. Cost reductions are central to this challenge, since these technologies are currently too expensive to compete with conventional vehicles based on fossil fuels. One important mechanism through which technology costs fall is learning-by-doing, the process by which cumulative global deployment leads to cost reduction. This paper develops long-term scenarios by implementing global technology learning endogenously in the TIAM-UCL global energy system model to analyse the role of hydrogen and electricity to decarbonise the transport sector. The analysis uses a multi-cluster global technology learning approach where key components (fuel cell, electric battery and electric drive train), to which learning is applied, are shared across different vehicle technologies such as hybrid, plug-in hybrid, fuel cell and battery operated vehicles in cars, light goods vehicles and buses. The analysis shows that hydrogen and electricity can play a critical role to decarbonise the transport sector. They emerge as complementary transport fuels, rather than as strict competitors, in the short and medium term, with both deployed as fuels in all scenarios. However, in the very long-term when the transport sector has been almost completely decarbonised, technology competition between hydrogen and electricity does arise, in the sense that scenarios using more hydrogen in the transport sector use less electricity and vice versa.
    International Journal of Hydrogen Energy 03/2013; 38(8):3419–3432. DOI:10.1016/j.ijhydene.2012.12.110
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    ABSTRACT: The UK government has established ambitious policies to address climate change and promote renewable energy, and has set targets both for reducing carbon emissions and for deploying renewables. Scotland, a constituent nation of the UK, has also set its own targets for climate change mitigation and renewable electricity. This paper analyses the energy, economic and environmental implications of carbon and renewable electricity targets in Scotland and the UK using a newly developed two-region UK MARKAL energy system model, where Scotland (SCT) and rest of the UK (RUK) are the two regions. The paper shows that meeting Scotland's carbon targets does not require additional decarbonisation effort if the UK meets its own targets at least cost; and that Scotland's renewable energy ambitions do imply additional costs above the least cost path to the meeting the UK's obligations under the EU renewable energy directive. Meeting Scottish renewable electricity targets diverts investment and deployment in renewables from rest of the UK to Scotland. In addition to increased energy system cost, Scottish renewable electricity targets may also require early investment in new electricity transmission capacity between Scotland and rest of the UK.
    Energy Policy 11/2012; 50:773–783. DOI:10.1016/j.enpol.2012.08.027
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    ABSTRACT: Marginal abatement cost (MAC) curves are a commonly used policy tool indicating emission abatement potential and associated abatement costs. They have been extensively used for a range of environmental issues in different countries and are increasingly applied to climate change policy. However in the past, decisions in the complex field of climate policy have been partially based on MAC curves with methodological shortcomings. This paper investigates how their simplistic use has been misleading and finds that the limits of the MAC curve concept can lead to biased decision making. Nevertheless, MAC curves are a useful policy tool, if not relied on exclusively, providing an illustrative guide for subsequent analysis especially for iterative policy making as more information on costs and policy effectiveness is discovered. This paper identifies some steps to overcome present shortcomings in the generation of MAC curves. These include a systems approach to capture interactions, consideration of ancillary benefits, a better representation of uncertainties and representation of cumulative emission abatement to address time-related interactions.
    Environmental Science & Policy 12/2011; 14(8). DOI:10.1016/j.envsci.2011.08.004
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    ABSTRACT: In order to reduce energy-related CO2 emissions different options have been considered: energy efficiency improvements, structural changes to low carbon or zero carbon fuel/technologies, carbon sequestration, and reduction in energy-service demands (useful energy). While efficiency and technology options have been extensively studied within the context of climate change mitigation, this paper addresses the possible role of price-related energy-service demand reduction. For this analysis, the elastic demand version of the TIAM–UCL global energy system model is used in combination with decomposition analysis. The results of the CO2 emission decomposition indicate that a reduction in energy-service demand can play a limited role, contributing around 5% to global emission reduction in the 21st century. A look at the sectoral level reveals that the demand reduction can play a greater role in selected sectors like transport contributing around 16% at a global level. The societal welfare loss is found to be high when the price elasticity of demand is low.
    Energy Policy 11/2011; 39(11):7224-7233. DOI:10.1016/j.enpol.2011.08.043
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    ABSTRACT: Baselines are generally accepted as a key input assumption in long-term energy modelling, but energy models have traditionally been poor on identifying baselines assumptions. Notably, transparency on the current policy content of model baselines is now especially critical as long-term climate mitigation policies have been underway for a number of years. This paper argues that the range of existing energy and emissions policies are an integral part of any long-term baseline, and hence already represent a “with-policy” baseline, termed here a Business-as-Unusual (BAuU). Crucially, existing energy policies are not a sunk effort; as impacts of existing policy initiatives are targeted at future years, they may be revised through iterative policy making, and their quantitative effectiveness requires ex-post verification. To assess the long-term role of existing policies in energy modelling, currently identified UK policies are explicitly stripped out of the UK MARKAL Elastic Demand (MED) optimisation energy system model, to generate a BAuU (with-policy) and a REF (without policy) baseline. In terms of long-term mitigation costs, policy-baseline assumptions are comparable to another key exogenous modelling assumption — that of global fossil fuel prices. Therefore, best practice in energy modelling would be to have both a no-policy reference baseline, and a current policy reference baseline (BAuU). At a minimum, energy modelling studies should have a transparent assessment of the current policy contained within the baseline. Clearly identifying and comparing policy-baseline assumptions are required for cost effective and objective policy making, otherwise energy models will underestimate the true cost of long-term emissions reductions.
    Energy Economics 03/2011; 33(2-33):153-160. DOI:10.1016/j.eneco.2010.10.009
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    ABSTRACT: As a response to the twin challenges of climate change mitigation and energy security, the UK government has set a groundbreaking target of reducing the UK’s economy-wide carbon emissions by 80% from 1990 levels by 2050. A second key UK energy policy is to increase the share of final energy consumption from renewables sources to 15% by 2020, as part of the wider EU Renewable Directive. The UK’s principle mechanisms to meet this renewable target are the Renewable Obligation (RO) in the electricity sector, the Renewable Transport Fuel Obligation (RTFO), and most recently the Renewable Heat Programme (RHP) for buildings. This study quantifies a range of policies, energy pathways, and sectoral trade-offs when combining mid- and long-term UK renewables and CO2 reduction policies. Stringent renewable policies are the binding constraints through 2020. Furthermore, the interactions between RO, RTFO, and RHP policies drive trade-offs between low carbon electricity, bio-fuels, high efficiency natural gas, and demand reductions as well as resulting 2020 welfare costs. In the longer term, CO2 reduction constraints drive the costs and characteristics of the UK energy system through 2050.
    Energy Policy 11/2010; 38(11-38):6724-6735. DOI:10.1016/j.enpol.2010.06.042
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