Grosse Stadtwerke – theoretische und empirische Exploration eines besonderen Akteurs in der Energiewende Deutschlands und der Schweiz

Urban utility companies are key players in the Swiss and German energy sector. Due to the federalist and subsidiary governance structure of the two countries’ energy sector, they perform highly system relevant tasks, as e.?g. managing the distribution grids or ensuring the public services for “their city”. In the public and scientific discourse on the role of different actor groups in the energy transition, however, not much attention is paid to urban utility companies. This contribution aims at a theoretical and empirical exploration of these particular actors by analysing their characteristics, specific challenges and strategic answers in the context of the energy transition. For this purpose, the article derives analytical dimensions for the analysis of urban utility companies from scholarly literature on transition studies, network industries and public corporate governance and empirically analyses characteristics and the current situation of urban utility companies in Germany and Switzerland. Methodologically, this article is based on an explorative, qualitative study, which synthesises results from a literature analysis, a document analysis, 38 expert interviews in both countries (in 2017) and two expert workshops conducted in Switzerland (in 2018). The study shows, how the characteristics of urban utility companies can be explained based on public corporate governance and network industries literature. This also allows to identify and understand their particular challenges, as e.?g. the fields of tension among public and private interest in the firms and the multi-dimensional relationship of owner or the particularities of network industries. Finally, this article points out, that the role of urban utility companies in the Swiss and German energy transition is neither just “inhibitor” nor pure “innovator”, but can be labelled as “intelligent follower” and “engineer of the energy transition”.     

Ein Jahr danach: Erste empirische Ergebnisse der Ausschreibungen für Windenergie an Land gemäß EEG 2017

The sixth amendment of the German Renewable Energy Sources Act (Erneuerbare-Energien-Gesetzes [EEG]) came into force at January 1st, 2017. Especially regarding onshore wind energy, it includes fundamental changes. Having set raised market integration as well as market compatibility and cost-efficiency as the main three goals, market-based tendering shall be the instrument to reach them.Meanwhile, the first three calls have been completed. This enables the opportunity for a first evaluation of the tendering as a system to fund onshore wind energy in Germany and a comparison of the criticism which came along with the newest amendment. At first glance, several improvements can be found: Especially a—previously expected—forced competition on the market but also low bid and tender values show a massive potential of cost reduction. However, the analysis further shows that energy cooperatives are disproportionally privileged, which leads to a distortion of competition and the risk of a future non-continuous development. Additionally, the current system results in regional disparities, coming along with disadvantages especially for the southern states. 10 suggestions for improvement show possible answers concerning the main shortcomings.     

Wann kommt die Kostenwende bei der EEG-Umlage?

The apportionment of the German Renewable Energy Sources Act (EEG-Umlage) constitutes a significant portion of the electricity price for domestic and commercial customers. First, the authors outline the implemented apportionment mechanism, the historical development as well as a couple of the lack of misjudgments. Subsequently, they investigate the question whether and when a reduction of the EEG apportionment can be expected. A model based on the current remuneration rules of the EEG, which is validated based on forecasts conducted by the transmission system operators, is used for the calculation of the EEG apportionment. The calculations show that an increase of the EEG levy to over 8?ct/kWh can be expected in the reference case, followed by a reduction from 2025 onwards. In the context of sensitivity calculations, various uncertainty factors are identified, such as the development of the wholesale price or the magnitude of the remuneration. Those factors significantly influence the EEG levy and thus underline the challenges in the development of a reliable forecast.     

State of the German Short-Term Power Market

The paper at hand provides a comprehensive overview of the current state of the German short-term power market with focus on trading and efficiency. The pivotal question is whether current market designs are appropriate to maximise social welfare. If this can’t be confirmed, trade-offs between technical restrictions, transparency requirements, the structure of the supply side and regulators focusing mainly on consumer surplus are analysed, which prevent markets from being fully efficient. The emphasis is on Germany due to it’s central location in Europe, it’s sheer size and the rapid increase of renewable generation in recent years. This development forced the German power market into a state of transition. As a result, developments in Germany might serve as a blueprint for other European countries. The introduction of negative day-ahead prices, the implementation of a very liquid intraday trading, a quarter hourly auction and market-based systems for the procurement of Ancillary Services are just some examples of Germany’s pioneering role. On the other hand, negative effects of the rapid changes such as the excessive use of non-market based redispatch measures and system endangering imbalance price regimes shall also be explored. As a matter of course, cross-references to other European countries and harmonisation projects are included as the German market is well interconnected with neighbouring markets.     

Can Lignite Take a Back Seat?

Transmission grid extension is a central aspect of the future energy system transition in Germany. This stems from the diverging occurrence of renewable energy feed-in and consumption as well as the targeted nuclear and currently discussed carbon phase-outs. After realizing the retirement of the domestic nuclear energy fleet by 2022, a next policy objective could be the phase-out of domestic lignite generation. The German electricity grid was not designed to accommodate these emerging challenges. Hence, the following paper addresses the impact of decommissioning lignite power plants on the most cost-effective grid extensions by 2030. To determine the optimal transmission grid design, efficient methods for techno-economic analysis are required. The challenge of conducting an analysis of grid extensions involves lumpy investment decisions and the non-linear character of several restrictions in a real-data environment. The following paper introduces the application of the Benders Decomposition, dividing the problem into an extension and a dispatch problem to reduce the degree of computational complexity. The results show that lignite phase-out can significantly increase the number of grid extensions in Germany. All scenarios simulating a lignite phase-out by 2030 lead to higher overall system costs but lower CO\({}_{2}\) emissions.     

Risks of the German Power Supply System

The German power supply system is experiencing a phase of radical change. The insurance industry designed this transformation not only as a property insurance donor, but also as an institutional investor. The emphasis of this commitment is based on their own assessment of the risks to which this supply system has been exposed. This study compares risk assessment designs from the insurance industry with that from technical network managers and shows in which the assessments significantly differ. For example, the insurance company’s risk assessment of natural disasters and cyber-attacks is much greater in terms of probability of occurrence and the potential of damage than the assessment of energy experts.     

Die Berücksichtigung von Spitzenkappung in der Anreizregulierung

The model of temporary disconnection of renewable energy in case of high energy injection and low demand is thought to be an effective method for reducing investments in electricity networks. However, plant owners need to be reimbursed for foregone sales. According to the currently discussed draft of the Amendment of the German Incentive Regulation Ordinance, these costs can be rolled over to the consumer on a yearly basis, but are part of the cost benchmark with their base year values. This paper shows that this model sets incentives for optimal investments in electricity networks, but violates the participation constraint: Net operators will be exposed to a severe risk of worsening their position in the cost benchmark. In expectation, they will generate losses and investors have no incentive to invest in electricity networks. This problem can be solved by allowing net operators to roll over costs to customers, while considering average reimbursement fees in the cost benchmark.     

Prognose der Day-Ahead Wind- und Photovoltaikstromerzeugung – Einflussgrößen und Zuverlässigkeit

In the future, the percentage of renewable energies in the electricity generation is expected to increase continuously. Especially weather-dependent wind and solar power plays a substantial role. These energy sources are partly characterized by a fluctuating and imprecisely predictable power generation. To cover the residual load and to balance the forecast errors a rising number of flexible producers and consumers will be needed in the future. This is necessary to ensure the high security of supply of the German electricity grid.Against this background, the objective of the following investigation is to analyse the day-ahead forecasting quality of the feed-in from wind and photovoltaic systems in the control areas of Germany’s transmission system operators and in the entire area of Germany for the years 2010 to 15. The aim of this analysis is to identify the crucial parameters that influence the forecast error. Subsequently, the share of the wind and photovoltaic power forecast which can be considered as reliably predictable for the following day is estimated. In addition, the increase in this reliable prediction through a higher level of detail in the assessment of the forecast error is quantified. Based on these results, the need of flexibilities through the weather-dependent electricity supply from wind and photovoltaic systems can be estimated, and the impact on the electricity system can be evaluated.     

Das Umlaufvermögen von Verteilnetzbetreibern

How much current assets are needed to operate a distribution system in Germany? The German “Energiewende” requires tremendous amounts of investment in the distribution network over the next years. The return of invested capital is regulated by § 7 Strom/GasNEV (German network tariff regulations). Current assets are principally included in the regulatory asset base in order to determine the regulatory equity yield rate. The regulatory authorities and distribution system operators have different point of views regarding the proper amount of current assets needed for operating a distribution network. This debate seems quite significant when considering that the average ratio of current assets to total assets is 25%. On the other hand, one could argue that distribution system operators do not need current assets at all. In order to address the issue of the proper amount of current assets for distribution system operators, business specific processes (such as the “EEG process”) should be examined. Furthermore, the provision of current assets causes costs of capital, which reduces the shareholder value and makes the acquisition of capital more challenging. This paper analyses such interrelations between current assets and shareholder value in regulated markets. Moreover, the current regulatory practice of cutting current assets in the regulatory asset base to a standardized amount does not seem appropriate. Rather there is a need for a multi-level and item-by-item based valuation scheme: Is the item required for the business? Is the amount limited to the efficient minimum? Is the amount comparable to other businesses? Concerning this matter, this paper examines proper instruments, such as the cash flow statement. In addition, this paper benchmarks the current (liquidity) ratio of distribution system operators and non-regulated companies. Based on this benchmark, the current assets of distribution system operators appear comparatively efficient. The results point out a need of action regarding current regulatory practice.     

Markt- und Systemintegration von erneuerbaren Energien im Rahmen der Systemtransformation – Ein Beitrag zur definitorischen Abgrenzung

The reconstruction of the electricity system is one of the main challenges of the German energy transition (Energiewende). The expansion of renewable electricity generation should enable the phase out of nuclear and fossil power generators in the long run. The Renewable Energy Sources Act (Erneuerbare Energien Gesetz) aims at increasing renewable generation up to a share of at least 80?% in gross electricity consumption by the year 2050. There are many possible ways to reach this target. Today, the characteristics of the future energy systems become apparent through the legal framework and long term energy scenarios.Economic, social and regulatory hurdles will need to be overcome to enable the transition of the electricity system. In this context, specific measures are evaluated with respect to their contribution on the system transformation, system integration and market integration. Up until now a consistent framework for evaluating political actions and scientific that should effectively support the energy political objectives is not present. The concepts of power system transformation, power system integration and market integration are differentiated and defined to close this gap. Based on this framework, a practical example is evaluated. The exact definitions will help to objectify the political and scientific debate. Furthermore, it contributes to develop regulatory and market mechanisms.     

Kurzfristige Kehrtwende bei der Beschaffung neu zu errichtender Anlagen für die Netzreserve in Deutschland

Shortly before the decision of the Electricity Market Law on June 22, 2016 took place, the Federal Ministry for Economic Affairs and Energy (BMWi) changed its mind with respect to the procurement of new power plants for the German grid reserve. Other than originally planned, this is no longer organized via a competitive bidding process. Instead, the responsibility for the procurement will be transferred to the transmission system operators, which therefore face the challenge of implementing an appropriate procurement mechanism. This paper presents an economic explanation for this short-term change. Our analysis reveals that the proposed transfer of the concept for the procurement of spare capacity to the procurement of the grid reserve was not appropriate. The bidders would have been exposed to significant risks, in particular due to high cost and calculation uncertainties, which are also critical with respect to the achievement of the objectives of the grid reserve. Therefore, we consider the decision of refusing the original procurement concept as the right step, although we consider a competitive procedure advantageous. However, such a procedure has to take the special requirements of the grid reserve into account. Yet this problem remains even after the transfer of responsibility from the BMWi to the transmission system operators.     

Modellgestützte Bewertung des Kraft-Wärme-Kopplungsgesetzes 2016 anhand ausgewählter Anwendungsfälle in Wohngebäuden

Cogeneration is a promising technology in the energy transition amongst other things in view of its energy efficiency and its broad applicability in the household, tertiary and industry sectors. For the promotion of cogeneration technologies, support schemes are in place in German energy policy. Amongst other things the Combined Heat and Power (CHP) Act serves as the main instrument for the promotion since 2002. In the new version of the CHP Act of 2016 the German Federal Government strives towards a more market-oriented design resulting in significant amendments featuring inter alia a highly case-dependent tariff design with modified levels and durations of remuneration. It is therefore the aim of the present study to assess these modifications with respect to technical, economic and ecological aspects in a model-based approach by means of selected use cases at different levels of spatial aggregation for residential buildings. Results point to an economic advantageousness for cases of the medium energy consumption level (streets and blocks of houses) under the new regime as well as the reversal of this attractiveness for objects of high consumption (neighbourhoods, districts). Particularly, CHP plants tend be dimensioned comparatively smaller with a greater number of full-load hours under the new regime. Furthermore, implications with regard to technical and ecological aspects are shown in this contribution.     

Bereitstellung von Regelleistung durch Elektrofahrzeuge: Modellrechnungen für Deutschland im Jahr 2035

The German government has set ambitious goals for both the expansion of renewable energy supply and electromobility. According to its Energiewende policy, electricity supply from fluctuating renewables is supposed to further increase considerably. This will tend to require a greater provision of balancing reserves. At the same time, supply from conventional dispatchable plants, which used to provide the bulk of reserves, will decrease. Against this background, this article analyzes the scope for an assumed fleet of 4.4 million electric vehicles to supply balancing reserves in 2035. Examining two different future power plant scenarios, it explores the potentials of reserve provision with and without the option of feeding electricity from vehicle batteries back to the grid. Results from an extended open-source power system simulation model show that the assumed vehicle fleet can efficiently provide a substantial share of reserve requirements, also in case the vehicle-to-grid option is not available. Arbitrage on wholesale markets, on the other hand, is negligible under basic assumptions. Likewise, total system cost savings are minor when compared to a pure cost-optimal loading of vehicle batteries. Under alternative assumptions on the future power plant portfolio as well as on battery degradation costs, however, wholesale arbitrage, reserve provision, and system cost savings can be substantial.     

Operating Strategies for Battery Storage Systems in Low-Voltage Grids to Limit the Feed-In Power of Solar Power Systems Using Fuzzy Control

Germany’s energy turnaround is leading to an increasing integration of photovoltaics (PVs) throughout its distribution grid. To ensure safe grid operation in times of high solar radiation, PV plants must either be throttled back to comply with the feed-in limitation or store a portion of their excess electricity in batteries. This paper presents a grid-optimized operating strategy for PV storage systems based on a Fuzzy Logic Controller that reduces peak feed-in and thus also PV curtailment losses. The Fuzzy Logic Controller uses data on PV power surplus and battery charge level as input variables. To obtain good results, the set of numerical parameters of the membership functions is enhanced by evolutionary programming.The energetic assessment shows that even small electrical storage capacities (<<5?kWh) reduce curtailment losses considerably when using the grid-optimized operating strategy. The economic assessment shows that, in 2016, investments in PV storage systems with large PV plants and small batteries have small (positive) Internal Rates of Return. The system efficiency of the battery storage has a small impact on the profitability of PV storage systems, whereas the cycle stability and the electricity purchase price have a large impact. Moreover, there is an economic benefit for plant operators to switch from the simple to the grid-optimized operating strategy. Solar forecast inaccuracies and variations in load and generation profiles have a negligible impact on the performance of the control algorithm.     

Price Sensitivity of Hourly Day-ahead and Quarter-hourly Intraday Auctions in Germany

The introduction of the quarter-hourly intraday auction in 2014 for the German market confirms a tendency towards short-term energy markets. The reason for the new market was the need to trade shorter periods than just hours a day-ahead to minimize open positions in the more volatile continuous intraday trading. The increased production capacity of solar power boosted this requirement for new short-term power products. The quarter-hourly market shows a distinctive zigzag price formation. We identify two influencing factors: first, the solar residual that combines the trading of solar power ramps around midday as well as the gradients of consumption and thermal power plant ramps throughout the course of the day, and second, a characteristic two stage market design with higher liquidity for the hourly than for the quarter-hourly auction. Therefore, demand, solar generation and inflexible ramps of thermal power plants are hedged at the hourly day-ahead auction and use the quarter-hourly auction only to balance the remaining differences. To prove this argument the price sensitivities of the hourly day-ahead and quarter-hourly intraday auctions in Germany are compared based on actual bid and ask curves from 2015 and 2016. Finally, the development of an adequate design of future spot markets is discussed.     

Grid Load Contributions Through Electric Vehicles and Their Uncertainties

With the numbers of electric vehicles on the increase, their additional electricity demand can no longer be neglected. From a power systems’ perspective, it is the time dependent electricity consumption that matters. In particular, the peak demand is increased in the case of uncontrolled charging, imposing additional stress on the system. Unfortunately, since there is an absence of representative electric vehicle driving patterns, a quantification of such temporal charging requirements is challenging. To overcome this problem, we developed a detailed model, which maps combustion engine vehicles onto electric vehicle equivalents. The model’s main strengths are the consideration of the diversity within the vehicle fleet as well as the differentiation into the boundary cases of pure battery electric vehicles and plug-in hybrid electric vehicles. Applied to a German traffic study, load curves for these two cases were generated. In addition, the existing uncertainty in between was quantified using Monte Carlo method. We show that the peak energy demand through electric vehicles is much greater on working days than on weekend days. Moreover, we find that the distinction between pure and plug-in-hybrid electric vehicles matters, at least for the time being. Apart from the numerical results, the model is well suited to generate input for more sophisticated investigations of charging strategies within energy system simulations.     

Dezentrale Steuerung eines Pools von Wärmepumpen auf Basis spieltheoretischer Methoden

An intelligent coupling of the power and the heat sector offers huge possibilities for the integration of electric energy from fluctuating, renewable energies. In this regard heat pumps depict a highly efficient way of power-heat-coupling. However, for a pool of heat pumps this potential can only be exploited effectively with a suitable control methodology. Such a control methodology makes it possible to enforce – depending on the specific case of application – a system-compatible behavior of the pool of heat pumps. In this respect a decentralized control approach offers a higher scalability compared with a centralized control approach. Thus a decentralized control approach based on game-theoretic methods is developed and presented here. For this purpose three game-theoretic optimization algorithms are examined. Their performance is analyzed and evaluated for two specific cases of application (reduction of peak load and tracking of a predefined load profile) by means of simulation. The results of both case studies illustrate, that game-theoretic control is easily applicable and can effectively be used to control a pool of heat pumps. Furthermore the developed control methodology can principally be adapted and utilized for all other electric loads with inherent storage functionality.     

Verlustwärme von Offshore-Gleichstrom-Seekabelsystemen – Entstehung und Übertragung

In Germany heat dissipation of subsea cables for power transmission from offshore wind farms into the sea floor is regulated. The precautionary value to be adhered to is a maximum temperature increase of 2?K in 20 to 30?cm sea bed depth. Such a temperature increase is defined by a number of influencing factors and boundary conditions and is extremely difficult to physically measure. Thus the purpose of this paper is to simulate the heat generation of DC submarine cables and the dissipation into the surrounding sea floor using the Finite Element Method (FEM). Herewith crucial parameters and influencing factors can be identified. The results show that the strongest influencing factors on the sediment temperature in 20 to 30?cm sea floor depth are the average load or longer-term preload of the cable, the burial depth and the thermal resistance of the sediment. Overall, during standard operation of wind farms and the corresponding cable systems the 2?K limit is adhered to safely. In general, this also applies to special wind and load situations.     

Gleichzeitigkeit als Leistungsgröße: Inter- und Intra-Klassen-Leistung volatiler EE-Einspeiser

The energy transition focuses on the expansion and enhancement of distribution grids and the integration of decentralized renewable generation plants. The integration of decentralized plants presents a major challenge for distribution system operators in particular. The planning and dimensioning of energy grids requires knowledge of all integrated generating units and power consumers, as well as their power ratings. Furthermore, knowledge about the diversity of renewable power plant types enables distribution system operators and scientists to selectively or cumulatively assess the maximum feed-in capacity. This is particularly important for the assessment of case studies or border scenarios. The purpose of this article is the evaluation of the maximum simultaneous feed-in power of PV and wind power plants. Furthermore, the ratio of the installed power to the maximum power generated by renewable power plants is also investigated. The diversity factor describes the ratio of the sum of all individual load’s maximum powers to the number of loads. This simultaneity can also be adapted to renewable power plants. However, it is differentiated here between simultaneous power within one renewable power plant type (intra-class performance) and simultaneous power of different renewable power plant types (inter-class performance). In cooperation with one of the largest national distribution network operator, regression lines are approximated by statistical analyzes, in order to determinate the diversity of the Central German area.     

Kurzfrist-Lastprognose für die Day-Ahead- und Intraday-Stromnachfrage bei sich systematisch ändernden Lasten

Load forecasts are used in various fields of the German energy economic to plan and to optimize the schedule of the power generation or the purchase of power from the markets based on the results of the forecasts. Therefor accurate load forecasts are necessary. But many load forecasting models reach their limits when dealing with systematic changes in the profile of the energy demand, since the model is usually calibrated by historic data so the relation between the load and the input parameters are estimated. Due to changes in the load profile the load level is moving to another level compared to the historic one. While the forecasting model is still calibrated on the old level, this can lead to higher forecasting errors and these can in turn have negative consequences on the following optimization steps. That is why a methodological approach is presented so that the forecasting model is able to adapt a systematic change in the load profile. Therefor the presented approach is at first applied to a case of application, before it is applied to two more extreme variations of the load profile to identify possible limits of the presented approach.