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Bottom-up energy system models have been used extensively to analyse future energy scenarios, addressing a wide variety of policy questions. This paper focuses on energy efficiency, a key energy, climate, and economic policy area where several examples of energy system model applications can be found in the literature. This paper analyses how different studies implement energy efficiency scenarios in energy system models and explains how the approach taken can affect the results significantly, potentially affecting policy decisions. This analysis contributes to understanding how this type of modelling framework considers energy efficiency policy issues and the extent of insight provided, or not, on different dimensions. With the aim of identifying 'best practice' in using energy system models to inform effective analysis of energy efficiency policy, the UK TIMES energy system model is used to implement five different energy efficiency scenarios for residential heating following different modelling approaches and replicating scenarios available in the literature. The study concludes that energy efficiency scenarios, implementing the same target, produce significantly different results in terms of technology mix, energy use, emissions and costs. Additionally, the outcomes show that there is no overall best energy efficiency scenario, as each impacts on different policy targets, which could come into conflict with each other. [ABSTRACT FROM AUTHOR]

With the European Green Deal, the European Union (EU27) aims to achieve an ambitious decarbonization of its electricity supply, while actively involving its citizens. Scenarios from energy and electricity sector models seek to inform this transition, although it is unclear to what extent these scenarios are aligned with the views of the citizens. In this study, four multi-organization, multi-model ensembles of existing electricity supply scenarios have been compiled for France, Germany, Poland, and the whole EU27 in 2035, leading to 612 scenarios in total. These scenarios were then compared with 601 preferred scenarios elicited from French, German, and Polish citizens in a survey with an interactive scenario tool. Results show that model-based and citizens’ preferred scenarios converged only on having moderate shares of onshore and offshore wind power and low shares of biomass and waste incineration. In contrast to the majority of model-based scenarios, most Polish and German citizens preferred a deeper decarbonization for their national electricity supply, while French citizens preferred a deeper denuclearization. Additionally, most citizens of all three countries used significant shares of solar photovoltaics and low shares of fossil fuels with carbon capture and storage, hence diverging from model-based scenarios. Similar patterns were found for the EU27 scenarios: many model-based scenarios included large shares of nuclear power, natural gas, and coal, while surveyed citizens preferred scenarios dominated by diverse renewable sources. European modelers should now quantify these missing scenarios so that the EU27 energy transition can be informed by modeling that is in line with citizens’ perspectives.

Bottom-up energy system models have been used extensively to analyse future energy scenarios, addressing a wide variety of policy questions. This paper focuses on energy efficiency, a key energy, climate, and economic policy area where several examples of energy system model applications can be found in the literature. This paper analyses how different studies implement energy efficiency scenarios in energy system models and explains how the approach taken can affect the results significantly, potentially affecting policy decisions. This analysis contributes to understanding how this type of modelling framework considers energy efficiency policy issues and the extent of insight provided, or not, on different dimensions. With the aim of identifying ‘best practice’ in using energy system models to inform effective analysis of energy efficiency policy, the UK TIMES energy system model is used to implement five different energy efficiency scenarios for residential heating following different modelling approaches and replicating scenarios available in the literature. The study concludes that energy efficiency scenarios, implementing the same target, produce significantly different results in terms of technology mix, energy use, emissions and costs. Additionally, the outcomes show that there is no overall best energy efficiency scenario, as each impacts on different policy targets, which could come into conflict with each other.

Energy scenarios should ideally account for societal feasibility and hence they could be informed by surveys on citizens’ preferences. This study surveyed consensus among citizens of France (N = 202), Germany (N = 199), and Poland (N = 200) on their national and EU electricity supply for 2035, considering different demographics, political orientations, and attitudes towards the transition and its governance. Results showed a broad consensus among surveyed citizens who positively viewed hydro, rooftop and open field solar, onshore and offshore wind power, biomass, and electricity savings, and who negatively viewed Carbon Capture and Storage (CCS) and net electricity imports. Citizens on average preferred diversified national and EU scenarios with rapid decarbonization and denuclearization, limited imports from neighboring countries, and small shares of CCS. Such scenarios should be now evaluated by modelers.

Long-range energy scenarios are commonly used to inform national energy policy decisions. Although the scenario approach aims to expand the spectrum of futures considered, in the past energy scenarios have not been diverse enough to include less expected real-world developments. We use a bottom-up energy system model EXPANSE with Modeling to Generate Alternatives (MGA) to assess the diversity of the existing ensemble of multi-organization, multi-model Swiss electricity supply scenarios. We show that both for 2035 and 2050 existing scenarios cover well the various possibilities in deployment of individual electricity generation technologies in terms of installed capacity or produced electricity. When analyzing scenarios as a whole, we find that in 2035 there is a lack of scenarios with high electricity demand and greater deployment of renewable technologies occurring simultaneously, as well as scenarios with a negligible or negative share of net electricity import. In 2050, there is also a lack of scenarios that depict high electricity demand and conservative deployment of new renewable technologies, especially solar PV. We propose six additional scenarios to be included to increase the diversity of the ensemble of Swiss electricity supply scenarios and achieve better understanding of the future possibilities and uncertainties. [ABSTRACT FROM AUTHOR]

Bottom-up energy system models rely on cost optimization to produce energy scenarios that inform policy analyses, debates and decisions. This paper reviews the rationale for the use of cost optimization and questions whether cost-optimal scenarios are adequate proxies of the real-world energy transition. Evidence from ex-post modeling shows that cost optimization does not approximate the real-world UK electricity system transition in 1990–2014. The deviation in cumulative total system costs from the cost-optimal scenario in 1990–2014 is equal to 9–23% under various technology, cost, demand, and discount rate assumptions. In fact, cost-optimal scenarios are shown to gloss over a large share of uncertainty that arises due to deviations from cost optimality. Exploration of large numbers of near-optimal scenarios under parametric uncertainty can give indication of the bounds or envelope of predictability of the real-world transition. Concrete suggestions are then made how to improve bottom-up energy system models to better deal with the vast uncertainty around the future energy transition. The paper closes with a reflective discussion on the tension between predictive and exploratory use of energy system models. [ABSTRACT FROM AUTHOR]

[Display omitted] • Retrospective cost-optimal scenarios are generated in 31 European countries in 1990–2019. • 24 accuracy indicators from literature are used for evaluating 34 model outputs. • The most informative smaller set of five accuracy indicators is identified, using clustering-based dissimilarity analysis. • Modeled scenarios in 31 countries are assessed by applying this small set of accuracy indicators. Retrospective evaluation of energy system models and scenarios is essential for ensuring their robustness for prospective policy support. However, quantitative evaluations currently lack systematic methods to be more holistic and informative. This paper reviews existing accuracy indicators used for retrospective evaluations of energy models and scenarios with the aim to find a small suite of complementary indicators. We quantify and compare 24 indicators to assess the retrospective performance of D-EXPANSE electricity sector modeling framework, used to model 31 European countries in parallel from 1990–2019. We find that symmetric mean percentage error, symmetric mean absolute percentage error, symmetric median absolute percentage error, root-mean-squared logarithmic error, and growth error together form the most informative suite of indicators. This study is the first step towards developing a model accuracy testbench to assess energy models and scenarios in multiple dimensions retrospectively. [ABSTRACT FROM AUTHOR]

Energy scenarios should ideally account for societal feasibility and hence they could be informed by surveys on citizens' preferences. This study surveyed consensus among citizens of France (N = 202), Germany (N = 199), and Poland (N = 200) on their national and EU electricity supply for 2035, considering different demographics, political orientations, and attitudes towards the transition and its governance. Results showed a broad consensus among surveyed citizens who positively viewed hydro, rooftop and open field solar, onshore and offshore wind power, biomass, and electricity savings, and who negatively viewed Carbon Capture and Storage (CCS) and net electricity imports. Citizens on average preferred diversified national and EU scenarios with rapid decarbonization and denuclearization, limited imports from neighboring countries, and small shares of CCS. Such scenarios should be now evaluated by modelers. • Systematic evaluation of citizens' consensus on future EU electricity supply. • Positive views on hydropower, solar and wind power, biomass, and electricity savings. • Negative views on CCS and net electricity imports. • Citizens prefer faster decarbonization and denuclearization than current policy targets. • Modelers should evaluate such scenarios as a way of incorporating feasibility considerations. [ABSTRACT FROM AUTHOR]