We propose an index to quantify and analyse the impact of climatological variability on the energy system at different timescales. We define the climatological renewable energy deviation index (credi) as the cumulative anomaly of a renewable resource with respect to its climate over a specific time period of interest. For this we introduce the smooth, yet physical, hourly rolling window climatology that captures the expected hourly to yearly behaviour of renewable resources. We analyse the presented index at decadal, annual and (sub-)seasonal timescales for a sample region and discuss scientific and practical implications. credi is meant as an analytical tool for researchers and stakeholders to help them quantify, understand, and explain, the impact of energy-meteorological variability on future energy system. Improved understanding translates to better assessments of how renewable resources, and the associated risks for energy security, may fare in current and future climatological settings. The practical use of the index is in resource planning. For example transmission system operators may be able to adjust short-term planning to reduce adequacy issues before they occur or combine the index with storyline event selection for improved assessments of climate change related risks.@en

In power system modelling the unit commitment problem is used to simulate the wholesale electricity market. A solution to the unit commitment problem is a least-cost schedule that contains information regarding the capacity factors of each generator, the total CO2 emissions, and unserved energy per hour. However, since there might be a large variety of (sub)-optimal solutions, these characteristics might be arbitrary and conclusions about them may be presumptuous.In this article, we illustrate this by running multiple experiments on a future European power system. Each scenario was run multiple times by adding additional terms to the objective function such as the minimization and maximization of generator capacity factors, carbon emissions, and loss of load hours. The results showed that schedules can be equivalent in terms of cost, but that relative capacity factors, emissions, and loss of load hours could differ by large factors.@en

We model the evolution of the Central Western Europe power system until 2040 with an increasing carbon price and strong growth of variable renewable energy sources (vRES) for four electricity market designs: the current energy-only market, a reformed energy-only market, both also with the addition of a capacity market. Each design is modelled for two decarbonisation pathways: one targeting net-zero emissions by 2040 for a 2 °C warming limit, and the other targeting −850 Mt CO₂ y‾ for a 1.5 °C warming limit. We compare these scenarios against the high-level objectives of delivering low-carbon electricity reliably to consumers at the lowest possible cost. Our results suggest that both 2 °C and 1.5 °C compliant systems could be achieved and deliver electricity reliably. In terms of cost, we find the 1.5 °C warming scenarios lead to system costs which are twice as high as the 2 °C scenarios due to the high cost of negative emission technologies – in particular direct air carbon capture (DAC). To make a 1.5 °C target more affordable, policymakers should investigate lower cost alternatives in other sectors, and increase research and development in DAC to reduce its cost.

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District heating represents a viable way to reduce carbon dioxide emissions in the built environment. This paper aims to assess the extent to which the market revenues of multiple heat production technologies can cover their fixed costs in a competitive wholesale district heating market. Marginal-cost pricing is applied in a case study of the Netherlands. A linear programming model incorporating heat supply and demand is developed to obtain hourly dispatch and heat market prices. It is concluded that low carbon heat generation technologies tend to have low short-run marginal costs. All examined heat producers have an under-recovery of fixed costs in a range between 60% and 90% except the waste incineration combined heat and power plant. It has an overall return on investment of 44% and 12% within the reference and heat pump scenario respectively. Although marginal-cost pricing may ensure cost-efficient dispatch, the market revenues are far from enough to recoup the investment costs for the majority of the heat producer, let alone the network costs. Significant additional remuneration is required to sustain a competitive heat market and ensure sufficient investment in new generation capacity in the long run.@en

Considering the targets of the Paris agreement, rapid decarbonisation of the power system is needed. In order to study cost-optimal and reliable zero and negative carbon power systems, a power system model of Western Europe for 2050 is developed. Realistic future technology costs, demand levels and generator flexibility constraints are considered. The optimised portfolios are tested for both favourable and unfavourable future weather conditions using results from a global climate model, accounting for the potential impacts of climate change on Europe's weather. The cost optimal mix for zero or negative carbon power systems consists of firm low-carbon capacity, intermittent renewable energy sources and flexibility capacity. In most scenarios, the amount of low-carbon firm capacity is around 75% of peak load, providing roughly 65% of the electricity demand. Furthermore, it is found that with a high penetration of intermittent renewable energy sources, a high dependence on cross border transmission, batteries and a shift to new types of ancillary services is required to maintain a reliable power system. Despite relatively small changes in the total generation from intermittent renewable energy sources between favourable and unfavourable weather years of 6%, emissions differ up to 70 MtCO2 yr−1 and variable systems costs up to 25%. In a highly interconnected power system with significant flexible capacity in the portfolio and minimal curtailment of intermittent renewables, the potential role of green hydrogen as a means of electricity storage appears to be limited.@en

In this study, we model seven scenarios for the European power system in 2050 based on 100% renewable energy sources, assuming different levels of future demand and technology availability, and compare them with a scenario which includes low-carbon non-renewable technologies. We find that a 100% renewable European power system could operate with the same level of system adequacy as today when relying on European resources alone, even in the most challenging weather year observed in the period from 1979 to 2015. However, based on our scenario results, realising such a system by 2050 would require: (i) a 90% increase in generation capacity to at least 1.9 TW (compared with 1 TW installed today), (ii) reliable cross-border transmission capacity at least 140 GW higher than current levels (60 GW), (iii) the well-managed integration of heat pumps and electric vehicles into the power system to reduce demand peaks and biogas requirements, (iv) the implementation of energy efficiency measures to avoid even larger increases in required biomass demand, generation and transmission capacity, (v) wind deployment levels of 7.5 GW y−1 (currently 10.6 GW y−1) to be maintained, while solar photovoltaic deployment to increase to at least 15 GW y−1 (currently 10.5 GW y−1), (vi) large-scale mobilisation of Europe's biomass resources, with power sector biomass consumption reaching at least 8.5 EJ in the most challenging year (compared with 1.9 EJ today), and (vii) increasing solid biomass and biogas capacity deployment to at least 4 GW y−1 and 6 GW y−1 respectively. We find that even when wind and solar photovoltaic capacity is installed in optimum locations, the total cost of a 100% renewable power system (∼530 €bn y−1) would be approximately 30% higher than a power system which includes other low-carbon technologies such as nuclear, or carbon capture and storage (∼410 €bn y−1). Furthermore, a 100% renewable system may not deliver the level of emission reductions necessary to achieve Europe's climate goals by 2050, as negative emissions from biomass with carbon capture and storage may still be required to offset an increase in indirect emissions, or to realise more ambitious decarbonisation pathways.@en

With the growing penetration of zero-marginal-cost wind and solar photovoltaics leading to falling electricity wholesale prices in the energy-only market, several European countries have implemented capacity remuneration mechanisms (CRMs) in an attempt to ensure security of supply (SoS). However, the literature is far from conclusive whether CRMs are indeed a necessary and/or cost-effective way of ensuring SoS. In this study, we quantitatively compare three different market designs under different levels of wind and PV growth for the interconnected systems of Germany, France, Belgium and the Netherlands. Preliminary results show that average electricity prices decrease in markets supplemented with a CRM, as does the volatility of electricity prices. Whether or not the contribution of a CRM to SoS is worth the cost (and its possible adverse impact on energy market functioning) of implementing a CRM also remains to be evaluated.@en

The integration of more variable renewable energy sources (vRES) like wind and solar photovoltaics (PV) is expected to play a significant role in reducing carbon dioxide emissions from the power sector. However, unlike conventional thermal generators, the generation patterns of vRES are spatially dependent, and the spatial distributions of wind and PV capacity can help or hinder their integration into the power system. After reviewing existing approaches for spatially distributing vRES, we present a new method to optimise the mix and spatial distribution of wind and PV capacity in Europe based on minimising residual demand. We test the potential of this method by modelling several scenarios exploring the effects of vRES penetration, alternative demand profiles, access to wind sites located far offshore, and alternative PV configurations. Assuming a copper-plate Europe without storage, we find an optimum vRES penetration rate of 82% from minimising residual demand, with an optimum capacity mix of 74% wind and 26% PV. We find that expanding offshore wind capacity in the North Sea is a ‘no regret’ option, though correlated generation patterns with onshore wind farms in neighbouring countries at high vRES penetration rates may lead to significant surplus generation. The presented method can be used to build detailed vRES spatial distributions and generation profiles for power system modelling studies, incorporating different optimisation objectives, spatial and technological constraints. However, even under the ideal case of a copper-plate Europe, we find that neither peak residual demand nor total residual demand can be significantly reduced through the spatial optimisation of vRES.@en

Contemporary combined heat and power (CHP) systems are often based on fossil fuels, such as natural gas or heating oil. Thereby, small-scale cogeneration systems are intended to replace or complement traditional heating equipment in residential buildings. In addition to space heating or domestic hot water supply, electricity is generated for the own consumption of the building or to be sold to the electric power grid. The adaptation of CHP-systems to renewable energy sources, such as solid biomass applications is challenging, because of feedstock composition and heat integration. Nevertheless, in particular smallscale CHP technologies based on biomass gasification and solid oxide fuel cells (SOFCs) offer significant potentials, also regarding important co-benefits, such as security of energy supply as well as emission reductions in terms of greenhouse gases or air pollutants. Besides emission or air quality regulations, the development of CHP technologies for clean on-site small-scale power generation is also strongly incentivised by energy efficiency policies for residential appliances, such as e.g. Ecodesign and Energy Labelling in the European Union (EU). Furthermore, solid residual biomass as renewable local energy source is best suited for decentralised operations such as micro-grids, also to reduce long-haul fuel transports. By this means such distributed energy resource technology can become an essential part of a forward-looking strategy for net zero energy or even smart plus energy buildings. In this context, this paper presents preliminary impact assessment results and most recent environmental considerations from the EU Horizon 2020 project "FlexiFuel-SOFC" (Grant Agreement no. 641229), which aims at the development of a novel CHP system, consisting of a fuel flexible smallscale fixed-bed updraft gasifier technology, a compact gas cleaning concept and an SOFC for electricity generation. Besides sole system efficiencies, in particular resource and emission aspects of solid fuel combustion and net electricity effects need to be considered. The latter means that vastly less emission intensive gasifier-fuel cell CHP technologies cause significant less fuel related emissions than traditional heating systems, an effect which is further strengthened by avoided emissions from more emission intensive traditional grid electricity generation. As promising result, operation "net" emissions of such on-site generation installations may be virtually zero or even negative. Additionally, this paper scopes central regulatory instruments for small-scale CHP systems in the EU to discuss ways to improve the framework for system deployment.@en

During recent years comprehensive work has been done on the development of small-scale solid biomass based combined heat and power generation technologies but still only few systems are available, their efficiencies are rather moderate, their fuel flexibility is restricted and their market penetration is poor. Against this background, the on-going Horizon 2020 project FlexiFuel-SOFC aims at the development of a new, highly efficient and fuel-flexible micro-scale biomass CHP technology for a capacity range of 25 to 150 kW (fuel power). The technology consists of an updraft gasifier, a gas cleaning system and a solid oxide fuel cell (SOFC). The new technology is developed with a main focus on (i) the further development of a small-scale fixed-bed updraft gasifier technology towards higher fuel flexibility and integration into the SOFC based CHP system, (ii) the development of a novel and compact gas cleaning unit and (iii) the further development of a SOFC system (stack efficiency of ~40 % with product gas from the updraft gasifier). A first testing plant has been designed, constructed and is presently taken into operation. @en