@article{EickeRuhnauHirth, author = {Eicke, Anselm and Ruhnau, Oliver and Hirth, Lion}, title = {Electricity balancing as a market equilibrium: An instrument-based estimation of supply and demand for imbalance energy}, doi = {10.1016/j.eneco.2021.105455}, abstract = {Frequency stability requires equalizing supply and demand for electricity at short time scales. Such electricity balancing is often understood as a sequential process in which random shocks, such as weather events, cause imbalances that system operators close by activating balancing reserves. By contrast, we study electricity balancing as a market where the equilibrium price (imbalance price) and quantity (system imbalance) are determined by supply and demand. System operators supply imbalance energy by activating reserves; market parties that, deliberately or not, deviate from schedules create a demand for imbalance energy. The incentives for deliberate strategic deviations emerge from wholesale market prices and the imbalance price. We empirically estimate the demand curve of imbalance energy, which describes how sensitive market parties are to imbalance prices. To overcome the classical endogeneity problem of price and quantity, we deploy instruments derived from a novel theoretical framework. Using data from Germany, we find a decline in the demand for imbalance energy by 2.2 MW for each increase in the imbalance price by EUR 1 per MWh. This significant price response is remarkable because the German regulator prohibits strategic deviations. We also estimate cross-market equilibriums between intraday and imbalance markets, finding that a shock to the imbalance price triggers a subsequent adjustment of the intraday price.}, language = {en} } @article{CloeteRuhnauHirth, author = {Cloete, Schalk and Ruhnau, Oliver and Hirth, Lion}, title = {On capital utilization in the hydrogen economy: The quest to minimize idle capacity in renewables-rich energy systems}, series = {International Journal of Hydrogen Energy}, volume = {46}, journal = {International Journal of Hydrogen Energy}, number = {1}, doi = {10.1016/j.ijhydene.2020.09.197}, pages = {169 -- 188}, abstract = {The hydrogen economy is currently experiencing a surge in attention, partly due to the possibility of absorbing wind and solar energy production peaks through electrolysis. A fundamental challenge with this approach is low utilization rates of various parts of the integrated electricity-hydrogen system. To assess the importance of capacity utilization, this paper introduces a novel stylized numerical energy system model incorporating the major elements of electricity and hydrogen generation, transmission and storage, including both "green" hydrogen from electrolysis and "blue" hydrogen from natural gas reforming with CO2 capture and storage (CCS). Balancing renewables with electrolysis results in low utilization of electrolyzers, hydrogen pipelines and storage infrastructure, or electricity transmission networks, depending on whether electrolyzers are co-located with wind farms or demand centers. Blue hydrogen scenarios face similar constraints. High renewable shares impose low utilization rates of CO2 capture, transport and storage infrastructure for conventional CCS, and of hydrogen transmission and storage infrastructure for a novel process (gas switching reforming) that enables flexible power and hydrogen production. In conclusion, both green and blue hydrogen can facilitate the integration of wind and solar energy, but the cost related to low capacity utilization erodes much of the expected economic benefit.}, language = {en} } @article{RuhnauHennigMadlener, author = {Ruhnau, Oliver and Hennig, Patrick and Madlener, Reinhard}, title = {Economic implications of forecasting electricity generation from variable renewable energy sources}, series = {Renewable Energy}, journal = {Renewable Energy}, number = {161}, issn = {0960-1481}, doi = {10.1016/j.renene.2020.06.110}, pages = {1318 -- 1327}, abstract = {Short-term forecasting of electricity generation from variable renewable energy sources is not an end in itself but should provide some net benefit to its user. In the case of electricity trading, which is in the focus of this paper, the benefit can be quantified in terms of an improved economic outcome. Although some effort has been made to evaluate and to improve the profitability of electricity forecasts, the understanding of the underlying effects has remained incomplete so far. In this paper, we develop a more comprehensive theoretical framework of the connection between the statistical and the economic properties of day-ahead electricity forecasts. We find that, apart from the accuracy and the bias, which have already been extensively researched, the correlation between the forecast errors and the market price spread determines the economic implications - a phenomenon which we refer to as 'correlation effect'. Our analysis is completed by a case study on solar electricity forecasting in Germany which illustrates the relevance and the limits of both our theoretical framework and the correlation effect.}, language = {en} } @article{BucksteegWiedmannPoestgesetal., author = {Bucksteeg, Michael and Wiedmann, Michael and P{\"o}stges, Arne and Haller, Markus and B{\"o}ttger, Diana and Ruhnau, Oliver and Schmitz, Richard}, title = {The transformation of integrated electricity and heat systems—Assessing mid-term policies using a model comparison approach}, series = {Renewable and Sustainable Energy Reviews}, volume = {160}, journal = {Renewable and Sustainable Energy Reviews}, doi = {10.1016/j.rser.2022.112270}, abstract = {The development of European power markets is highly influenced by integrated electricity and heat systems. Therefore, decarbonization policies for the electricity and heat sectors, as well as numerical models that are used to guide such policies, should consider cross-sectoral interdependencies and need evaluation. Many model-based policy assessments evaluate potential benefits of combined heat and power. However, the extent of benefits, such as emissions reductions, found in existing studies is subject to considerable variations. While scenarios and model inputs may partly explain such variations, differences in results may also be related to the model formulation itself. Against this background, this study is the first to compare electricity market models in the context of potential benefits of integrated electricity and heat systems in decarbonization. Five large-scale market models covering electricity and heat supply were utilized to study the interactions between a rather simple coal replacement scenario and a more ambitious policy that supports decarbonization through power-to-heat. With a focus on flexibility provision, emissions reduction, and economic efficiency, although the models agree on the qualitative effects, there are considerable quantitative differences. For example, the estimated reductions in overall CO2 emissions range between 0.2 and 9.0 MtCO2/a for a coal replacement scenario and between 0.2 and 25.0 MtCO2/a for a power-to-heat scenario. Model differences can be attributed mainly to the level of detail of combined heat and power modeling and the endogeneity of generation investments. Based on a detailed comparison of the modeling results, implications for modeling choices and political decisions are discussed.}, language = {en} } @techreport{TiedemannSanchezCanalesSchuretal., type = {Working Paper}, author = {Tiedemann, Silvana and Sanchez Canales, Jorge and Schur, Felix and Sgarlato, Raffaele and Hirth, Lion and Ruhnau, Oliver and Peters, Jonas}, title = {Identifying Elasticities in Autocorrelated Time Series Using Causal Graphs}, publisher = {arXiv}, doi = {10.48550/arXiv.2409.15530}, pages = {37}, abstract = {The price elasticity of demand can be estimated from observational data using instrumental variables (IV). However, naive IV estimators may be inconsistent in settings with autocorrelated time series. We argue that causal time graphs can simplify IV identification and help select consistent estimators. To do so, we propose to first model the equilibrium condition by an unobserved confounder, deriving a directed acyclic graph (DAG) while maintaining the assumption of a simultaneous determination of prices and quantities. We then exploit recent advances in graphical inference to derive valid IV estimators, including estimators that achieve consistency by simultaneously estimating nuisance effects. We further argue that observing significant differences between the estimates of presumably valid estimators can help to reject false model assumptions, thereby improving our understanding of underlying economic dynamics. We apply this approach to the German electricity market, estimating the price elasticity of demand on simulated and real-world data. The findings underscore the importance of accounting for structural autocorrelation in IV-based analysis.}, language = {en} } @techreport{BucksteegWiedmannPoestgesetal., type = {Working Paper}, author = {Bucksteeg, Michael and Wiedmann, Michael and P{\"o}stges, Arne and Haller, Markus and B{\"o}ttger, Diana and Ruhnau, Oliver and Schmitz, Richard}, title = {The transformation of integrated electricity and heat systems—Assessing mid-term policies using a model comparison approach}, abstract = {The development of European power markets is highly influenced by integrated electricity and heat systems. Therefore, decarbonization policies for the electricity and heat sectors, as well as numerical models that are used to guide such policies, should consider cross-sectoral interdependencies. However, although many model-based policy assessments for the highly interconnected European electricity system exist, international studies that consider interactions with the heat sector are rare. In this contribution, we systematically study the potential benefits of integrated heat and power systems by conducting a model comparison experiment. Five large-scale market models covering electricity and heat supply were utilized to study the interactions between a rather simple coal replacement scenario and a more ambitious policy that supports decarbonization through power-to-heat. With a focus on flexibility provision, emissions reduction, and economic efficiency, although the models agree on the qualitative effects, there are considerable quantitative differences. For example, the estimated reductions in overall CO2 emissions range between 0.2 and 9.0 MtCO2/a for a coal replacement scenario and between 0.2 and 25.0 MtCO2/a for a power-to-heat scenario. Model differences can be attributed mainly to the level of detail of CHP modeling and the endogeneity of generation investments. Based on a detailed comparison of the modeling results, implications for modeling choices and political decisions are discussed.}, language = {en} } @article{HirthKhannaRuhnau, author = {Hirth, Lion and Khanna, Tarun M. and Ruhnau, Oliver}, title = {How aggregate electricity demand responds to hourly wholesale price fluctuations}, series = {Energy Economics}, volume = {135}, journal = {Energy Economics}, publisher = {Elsevier BV}, issn = {0140-9883}, doi = {10.1016/j.eneco.2024.107652}, abstract = {Electricity needs to be consumed at the very moment of production, leading wholesale prices to fluctuate widely at (sub-)hourly time scales. This article investigates the response of aggregate electricity demand to such price variations. Using wind energy as an instrument, we estimate a significant and robust short-term price elasticity of about -0.05 in Germany and attribute this to industrial consumers. As the share of consumption that is exposed to real-time prices (currently less than 25\%) expands, we expect the aggregated price elasticity to grow.}, language = {en} } @article{RuhnauStieweMuesseletal., author = {Ruhnau, Oliver and Stiewe, Clemens and Muessel, Jarusch and Hirth, Lion}, title = {Natural gas savings in Germany during the 2022 energy crisis}, series = {Nature Energy}, journal = {Nature Energy}, doi = {10.48462/opus4-4944}, url = {http://nbn-resolving.de/urn:nbn:de:kobv:b1570-opus4-49445}, abstract = {Russia curbed its natural gas supply to Europe in 2021 and 2022, creating a grave energy crisis. This paper empirically estimates the crisis response of natural gas consumers in Germany—for decades the largest export market for Russian gas. Using a multiple regression model, we estimate the response of small consumers, industry, and power stations separately, controlling for the non-linear temperature-heating relationship, seasonality, and trends. We find significant and substantial gas savings for all consumer groups, but with differences in timing and size. For instance, industry started reducing consumption as early as September 2021, while small consumers saved substantially only since March 2022. Across all sectors, gas consumption during the second half of 2022 was 23\% below the temperature-adjusted baseline. We discuss the drivers behind these savings and draw conclusions on their role in coping with the crisis.}, language = {en} } @techreport{HirthKhannaRuhnau, type = {Working Paper}, author = {Hirth, Lion and Khanna, Tarun and Ruhnau, Oliver}, title = {The (very) short-term price elasticity of German electricity demand}, abstract = {Electricity is a peculiar economic good, the most important reason being that it needs to be supplied at the very moment of consumption. As a result, wholesale electricity prices fluctuate widely at hourly or sub-hourly time scales, regularly reaching multiples of their average, and even turn negative. This paper examines whether the demand for electricity responds to such price variations in the very short term. To solve the classical identification problem when estimating a demand curve, we use weather-driven wind energy generation as an instrument. Our robustness checks confirm that wind energy is indeed a strong and valid instrument. Using data from Germany, we estimate that a 1 €/MWh increase in the wholesale electricity price causes the aggregate electricity demand to decline by 67-80 MW or 0.12-0.14\%, contradicting the conventional wisdom that electricity demand is highly price-inelastic. These estimates are statistically significant and robust across model specifications, estimators, and sensitivity analyses. At average price and demand, our estimates correspond to a price elasticity of demand of about -0.05. Comparing situations with high and low wind energy (5-95th percentile), we estimate that prices vary by 26 €/MWh, and the corresponding demand response to wholesale electricity prices is about 2 GW, or 2.6\% of peak load. Our analysis suggests that the demand response in Germany can be attributed primarily to industrial consumers.}, language = {en} } @article{RuhnauEickeSgarlatoetal., author = {Ruhnau, Oliver and Eicke, Anselm and Sgarlato, Raffaele and Tr{\"o}ndle, Tim and Hirth, Lion}, title = {Cost-Potential Curves of Onshore Wind Energy: the Role of Disamenity Costs}, series = {Environmental and Resource Economics}, journal = {Environmental and Resource Economics}, doi = {10.1007/s10640-022-00746-2}, abstract = {Numerical optimization models are used to develop scenarios of the future energy system. Usually, they optimize the energy mix subject to engineering costs such as equipment and fuel. For onshore wind energy, some of these models use cost-potential curves that indicate how much electricity can be generated at what cost. These curves are upward sloping mainly because windy sites are occupied first and further expanding wind energy means deploying less favorable resources. Meanwhile, real-world wind energy expansion is curbed by local resistance, regulatory constraints, and legal challenges. This presumably reflects the perceived adverse effect that onshore wind energy has on the local human population, as well as other negative external effects. These disamenity costs are at the core of this paper. We provide a comprehensive and consistent set of cost-potential curves of wind energy for all European countries that include disamenity costs, and which can be used in energy system modeling. We combine existing valuation of disamenity costs from the literature that describe the costs as a function of the distance between turbine and households with gridded population data, granular geospatial data of wind speeds, and additional land-use constraints to calculate such curves. We find that disamenity costs are not a game changer: for most countries and assumptions, the marginal levelized cost of onshore wind energy increase by 0.2-12.5 €/MWh.}, language = {en} } @techreport{StieweRuhnauHirth, type = {Working Paper}, author = {Stiewe, Clemens and Ruhnau, Oliver and Hirth, Lion}, title = {European industry responds to high energy prices: The case of German ammonia production.}, pages = {6}, abstract = {Since September 2021, European natural gas prices are at record-high levels. On average, they have been six to seven times higher than pre-pandemic price levels. While the post-pandemic recovery of global natural gas demand has driven up prices around the world, the most important drivers for European gas prices were Russia's less-than-usual supply since mid-2021 and its invasion of Ukraine in February 2022. Western efforts to abandon Russian gas imports altogether mean that high natural gas prices are likely to stay for longer. While high gas prices may be the new normal, there is uncertainty about the economic reaction to this shock. How do energy-intensive industries react? Do global value chains collapse if intermediate goods produced in Europe become uneconomic because of high energy prices? Our preliminary analysis shows that industry response to has in fact been visible from the very onset of the energy crisis. A closer look at German fertilizer production, which heavily relies on natural gas as fuel and feedstock to produce ammonia as an intermediate product, reveals that increased ammonia imports have allowed domestic fertilizer production to remain remarkably stable.}, language = {en} } @techreport{RuhnauMuessel, type = {Working Paper}, author = {Ruhnau, Oliver and Muessel, Jarusch}, title = {Update and extension of the When2Heat dataset}, abstract = {The "When2Heat" dataset comprises synthetic national time series for heat demand and heat pumps' coefficient of performance (COP) in hourly resolution. Heat demands for space and water heating are computed by combining gas standard load profiles with spatial temperature reanalysis data and population geodata. With this update, we extend the dataset to 28 European countries and the period from 2008 to 2019, including new, state-of-the-art data sources. For the geographical extension, we propose a novel approach, shifting established German heat demand curves based on country-specific heating thresholds to account for regional differences in thermal insulation and user behavior. Using the example of Italy, we illustrate the effect of shifting heat demand curves. The dataset, scripts, and input parameters are publicly available under an open-source license on the Open Power System Data platform.}, language = {en} } @article{Ruhnau, author = {Ruhnau, Oliver}, title = {How flexible electricity demand stabilizes wind and solar market values: the case of hydrogen electrolyzers}, series = {Applied Energy, Elsevier}, volume = {307}, journal = {Applied Energy, Elsevier}, doi = {10.1016/j.apenergy.2021.118194}, abstract = {Wind and solar energy are often expected to fall victim to their own success: the higher their share in electricity production, the more their revenue on electricity markets (their "market value") declines. While in conventional power systems, the market value may converge to zero, this study demonstrates that "green" hydrogen production, through adding electricity demand in low-price hours, can effectively and permanently halt the decline. With an analytical derivation, a Monte Carlo simulation, and a numerical electricity market model, I find that - due to flexible hydrogen production alone - market values across Europe likely converge above €19 ± 9 MWh-1 for solar energy and above €27 ± 8 MWh-1 for wind energy in 2050 (annual mean estimate ± standard deviation). This lower boundary is in the range of the projected levelized costs of renewables and has profound implications. Market-based renewables may hence be within reach. simulation, and a numerical electricity market model, I find that - due to flexible hydrogen production alone - market values across Europe likely converge above €19 ± 9 MWh-1 for solar energy and above €27 ± 8 MWh-1 for wind energy in 2050 (annual mean estimate ± standard deviation). This lower boundary is in the range of the projected levelized costs of renewables and has profound implications. Market-based renewables may hence be within reach.}, language = {en} } @article{RuhnauQvist, author = {Ruhnau, Oliver and Qvist, Staffan}, title = {Storage requirements in a 100\% renewable electricity system: Extreme events and inter-annual variability}, series = {Environmental Research Letters}, journal = {Environmental Research Letters}, publisher = {IOP Publishing}, doi = {10.1088/1748-9326/ac4dc8}, abstract = {In the context of 100\% renewable electricity systems, prolonged periods with persistently scarce supply from wind and solar resources have received increasing academic and political attention. This article explores how such scarcity periods relate to energy storage requirements. To this end, we contrast results from a time series analysis with those from a system cost optimization model, based on a German 100\% renewable case study using 35 years of hourly time series data. While our time series analysis supports previous findings that periods with persistently scarce supply last no longer than two weeks, we find that the maximum energy deficit occurs over a much longer period of nine weeks. This is because multiple scarce periods can closely follow each other. When considering storage losses and charging limitations, the period defining storage requirements extends over as much as 12 weeks. For this longer period, the cost-optimal storage capacity is about three times larger compared to the energy deficit of the scarcest two weeks. Adding other sources of flexibility for the example of bioenergy, the duration of period that defines storage requirements lengthens to more than one year. When optimizing system costs based on single years rather than a multi-year time series, we find substantial inter-annual variation in storage requirements with the most extreme year needing more than twice as much storage as the average year. We conclude that focusing on short-duration extreme events or single years can lead to an underestimation of storage requirements and costs of a 100 \% renewable system.}, language = {en} } @techreport{RuhnauStieweMuesseletal., type = {Working Paper}, author = {Ruhnau, Oliver and Stiewe, Clemens and Muessel, Jarusch and Hirth, Lion}, title = {Gas demand in times of crisis. The response of German households and industry to the 2021/22 energy crisis}, pages = {8}, abstract = {Europe is in the midst of the most severe energy crisis in a generation, at the core of which is the continuously plummeting supply of Russian natural gas. With alternative supply options being limited, natural gas prices have surged. This paper empirically estimates the response of natural gas demand to the price increase, using data from Germany—the so far largest consumer of Russian natural gas. We identify the crisis response of small and large consumers separately, controlling for temperature, gas-fired power generation, and economic activity. For small consumers, including mostly households, we find a substantial demand reduction of 6\% from March onwards—most likely due to political and ethical considerations after the start of Russia's invasion of Ukraine. For industrial consumers, demand reductions started much earlier in August 2021, when wholesale prices for natural gas started to surge, with an average reduction of 11\%. We conclude that voluntary industrial demand response has played a significant role in coping with the energy crisis so far.}, language = {en} }