Harder, better, faster, stronger: understanding and improving the tractability of large energy system models

Energy system models based on linear programming have been growing in size with the increasing need to model renewables with high spatial and temporal detail. Larger models lead to high computational requirements. Furthermore, seemingly small changes in a model can lead to drastic differences in runtime. Here, we investigate measures to address this issue. We review the mathematical structure of a typical energy system model, and discuss issues of sparsity, degeneracy and large numerical range. We introduce and test a method to automatically scale models to improve numerical range. We test this method as well as tweaks to model formulation and solver preferences, finding that adjustments can have a substantial impact on runtime. In particular, the barrier method without crossover can be very fast, but affects the structure of the resulting optimal solution. We conclude with a range of recommendations for energy system modellers

High-resolution large-scale onshore wind energy assessments : A review of potential definitions, methodologies and future research needs

Funding Information: KG, MK, JS, OT and SW gratefully acknowledge support from the European Research Council (’‘reFUEL’’ ERC-2017-STG 758149). JL has received funding from the European Research Council under the European Union's Horizon 2020 research and innovation programme (grant agreement No. 715132). MJ and IS were funded by the Engineering and Physical Sciences Research Council [ EP/R045518/1 ] through the IDLES programme. JW is funded through an ETH Postdoctoral Fellowship and acknowledges support from the ETH foundation and the Uniscientia foundation. The authors gratefully acknowledge the helpful comments of three anonymous reviewers on an earlier version of this paper.Peer reviewedPublisher PD

Supply-side options to reduce land requirements of fully renewable electricity in Europe

Renewable electricity can fully decarbonise the European electricity supply, but large land requirements may cause land-use conflicts. Using a dynamic model that captures renewable fluctuations, I explore the relationship between land requirements and total system cost of different supply-side options in the future. Cost-minimal fully renewable electricity requires some 97,000 km2 (2% of total) land for solar and wind power installations, roughly the size of Portugal, and includes large shares of onshore wind. Replacing onshore wind with offshore wind, utility-scale PV, or rooftop PV reduces land requirements drastically with only small cost penalties. Moving wind power offshore is most cost-effective and reduces land requirements by 50% for a cost penalty of only 5%. Wind power can alternatively be replaced by photovoltaics, leading to a cost penalty of 10% for the same effect. My research shows that fully renewable electricity supply can be designed with very different physical appearances and impacts on landscapes and the population, but at similar cost.ISSN:1932-620

Renewable electricity for all: Untangling conflicts about where to build Europe’s future supply infrastructure

The European Union aims to fully decarbonise its electricity system by 2050 and relies largely on renewable electricity to reach this goal. A complete decarbonisation requires a large expansion of electricity infrastructure, such as wind farms, solar farms, and transmission lines. The expansion is controversially debated, with different preferences about which infrastructure should be built and where. Preferences diverge for four reasons. First, infrastructure competes with other uses of land and alters landscapes. Second, location and size of renewable infrastructure projects determine ownership structures: large, centralised installations are better for large investors, while small, decentralised installations are better for small investors. Third, cost of electricity varies by region, based on the quality of locally available renewable resources. Fourth, the more electricity countries, regions, and municipalities generate locally, the less they must depend on imports. In building upon the diverging preferences regarding these impacts, three dominant logics determine where and which renewable infrastructure should be built. Within the first logic, it should be driven by cost and thus built where it is cheapest. Within the second logic, it should be driven by location of demand and thus built within local communities. Within the third logic, it should be built in such a way that reduces impairment of landscapes. Because the three logics are conflicting, there is no consensus regarding infrastructure allocation. This lack of consensus may serve as a problem, as it increases opposition against developments and thus may slow or even stop the energy transition. Within three contributions, I analyse the technical feasibility, economic viability, and land requirements of the three logics. My objective is to determine the extent to which the logics are possible, the extent to which they conflict, and whether compromise solutions exist that may relieve conflicts. In the first contribution, I analyse the technical possibility of the demand-driven logic. By determining solar and wind generation potentials and contrasting them with today’s electricity demand, I identify whether self-sufficiency is possible, or whether imports are necessary. I find that the generation potential of Europe and all countries within Europe is large enough to satisfy annual electricity demand. On the regional (subnational) and municipal scales, most places have the potential for self-sufficiency, though some do not -- in particular, those with a high population density. My findings show that the demand-driven logic is technically possible in most places within Europe but that some places require electricity imports. In the second contribution, I analyse the economic viability of the demand-driven logic and contrast it with the cost-driven logic. Using a dynamic model of the electricity system, I determine cost of electricity when there is unlimited trade on the continental scale (cost-driven logic), and when trade is limited to within countries or subnational regions (demand-driven logic). I find that cost increases with smaller scales and that the demand-driven logic leads to the highest cost. However, I find also that cost is primarily driven by where and how renewable fluctuations are balanced rather than where and how electricity is generated. While a trade-off between cost and scale exists, cost penalties of the demand-driven logic must not be large as long as fluctuations of renewable generation are balanced at continental scale. In the third contribution, I analyse land requirements and the economic viability of the landscape-driven logic. Using the same model as before, I analyse the relationship between cost and land requirements of the electricity system by varying shares of solar and wind supply technologies. I find that the cost-minimal case (cost-driven) is based in equal parts on onshore wind and solar power on fields and requires some 2% of Europe’s land, roughly the size of Portugal. Land requirements can be reduced by replacing onshore wind with offshore wind or solar power, but land must be traded-off against cost. Cost penalties, however, are not substantial: half of the land requirements can be avoided for an expected cost penalty of only 5% when onshore wind turbines are moved offshore. The findings demonstrate the economic viability of the landscape-driven logic. My findings have two important implications for European energy policy and the transition to a decarbonised electricity system. First, I show that renewable electricity based on any of the three logics is technically feasible and economically viable almost everywhere in Europe. However, the logics have very different impacts on landscapes, economies, and societies. The question of where and which renewable infrastructure should be built is a normative question. Second, I show that renewable electricity is feasible not only when strictly following one logic, but also by mixing aspects of the logics, and that necessary trade-offs must not be strong. For example, a system supplied primarily by solar power on the regional scale with continental trade for balancing, has low cost, low land requirements, and high local independence. Similarly, a system supplied by primarily offshore wind and solar power on the national scale has low cost, low land requirements, and high national independence. Such compromise solutions may not be ideal in any logic, but they may be acceptable to all, and thus have the potential to relieve conflicts and enable a faster energy transition

timtroendle/urban-occupants-paper: v1.1

This is a paper and all scripts creating the results of the paper that resulted from the Knowledge Transfer Partnership between the Energy Efficient Cities initiative (EECi) of University of Cambridge and Improbable Ltd. To learn how results can be replicated see ./README.md. This library is released under the MIT license, see ./LICENSE

Public support for phasing out carbon-intensive technologies: the end of the road for conventional cars in Germany?

Limiting the global mean temperature increase to 1.5 degrees C requires phasing out fossil fuel combustion almost entirely within the next three decades and replacing carbon-intensive technologies with low-carbon alternatives. Such socio-technical transitions are politically feasible only if public acceptance is sufficiently high. Here we investigate German citizens' views on the phase-out of internal combustion engine vehicles (ICEVs) using a random forest (decision trees) classification and logistic regression model. We surveyed a demographically representative sample (N = 1,663) in 2021, finding that the majority of respondents (67%) approve of an ICEV phase-out by 2040 or hold a neutral stance. Acceptability is best predicted by the degree to which environmental problems are attributed to ICEVs, followed by respondents' willingness to abandon cars altogether or adopt electric vehicles (EVs). Our results further indicate that acceptability can be increased by providing people with information that present EVs in a more favourable, and ICEVs in a less favourable light. When the European Commission proposed to ban the sale of ICEVs by 2035, we conducted a follow-up survey to investigate whether this had influenced acceptability in Germany - with the result that it had not. In terms of concrete policies, pull measures such as public transport or electric vehicle purchase subsidies are preferred by the public over more restrictive policies such as taxes or bans. The findings of this study shed light on different dimensions of public opinion and their important implications for policymaking and the political feasibility of this socio-technical transition. Insights from this research can help policymakers in designing effective yet widely acceptable transport decarbonization policies.ISSN:1752-7457ISSN:1469-306

Home-made or imported: On the possibility for renewable electricity autarky on all scales in Europe

Because solar and wind resources are available throughout Europe, a transition to an electricity system based on renewables could simultaneously be a transition to an autarkic one. We investigate to which extent electricity autarky on different levels is possible in Europe, from the continental, to the national, regional, and municipal levels, assuming that electricity autarky is only possible when the technical potential of renewable electricity exceeds local demand. We determine the technical potential of roof-mounted and open field photovoltaics, as well as on- and offshore wind turbines through an analysis of surface eligibility, considering land cover, settlements, elevation, and protected areas as determinants of eligibility for renewable electricity generation. In line with previous analyses we find that the technical-social potential of renewable electricity is greater than demand on the European and national levels. For subnational autarky, the situation is different: here, demand exceeds potential in several regions, an effect that is stronger the higher population density is. To reach electricity autarky below the national level, regions would need to use very large fractions or all of their non-built-up land for renewable electricity generation. Subnational autarky requires electricity generation to be in close proximity to demand and thus increases the pressure on non-built-up land especially in densely populated dense regions where pressure is already high. Our findings show that electricity autarky below the national level is often not possible in densely populated areas in Europe

Most industrialised countries have peaked carbon dioxide emissions during economic crises through strengthened structural change

As the climate targets tighten and countries are impacted by several crises, understanding how and under which conditions carbon dioxide emissions peak and start declining is gaining importance. We assess the timing of emissions peaks in all major emitters (1965–2019) and the extent to which past economic crises have impacted structural drivers of emissions contributing to emission peaks. We show that in 26 of 28 countries that have peaked emissions, the peak occurred just before or during a recession through the combined effect of lower economic growth (1.5 median percentage points per year) and decreasing energy and/or carbon intensity (0.7) during and after the crisis. In peak-and-decline countries, crises have typically magnified pre-existing improvements in structural change. In non-peaking countries, economic growth was less affected, and structural change effects were weaker or increased emissions. Crises do not automatically trigger peaks but may strengthen ongoing decarbonisation trends through several mechanisms.ISSN:2662-443

Harder, better, faster, stronger: understanding and improving the tractability of large energy system models

Acknowledgements: Not applicableAbstract Background Energy system models based on linear programming have been growing in size with the increasing need to model renewables with high spatial and temporal detail. Larger models lead to high computational requirements. Furthermore, seemingly small changes in a model can lead to drastic differences in runtime. Here, we investigate measures to address this issue. Results We review the mathematical structure of a typical energy system model, and discuss issues of sparsity, degeneracy and large numerical range. We introduce and test a method to automatically scale models to improve numerical range. We test this method as well as tweaks to model formulation and solver preferences, finding that adjustments can have a substantial impact on runtime. In particular, the barrier method without crossover can be very fast, but affects the structure of the resulting optimal solution. Conclusions We conclude with a range of recommendations for energy system modellers: first, on large and difficult models, manually select the barrier method or barrier+crossover method. Second, use appropriate units that minimize the model’s numerical range or apply an automatic scaling procedure like the one we introduce here to derive them automatically. Third, be wary of model formulations with cost-free technologies and dummy costs, as those can dramatically worsen the numerical properties of the model. Finally, as a last resort, know the basic solver tolerance settings for your chosen solver and adjust them if necessary. </jats:sec