Elena Raycheva

Last Name

Raycheva

First Name

Elena

ORCID

0000-0003-2712-1016

Organisational unit

09481 - Hug, Gabriela / Hug, Gabriela

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Publications 1 - 10 of 12

The Value of Flexibility in a Carbon Neutral Power System
Raycheva, Elena; Garrison, Jared; Schaffner, Christian; et al. (2022)
Risk-informed coordinated generation and transmission system expansion planning: A net-zero scenario of Switzerland in the European context
Raycheva, Elena; Gjorgiev, Blazhe; Hug, Gabriela; et al. (2023)
Energy
Power systems around the world are changing due to the rapid transformation of the generation mix. Unprecedented configurations of the power system may increase the exposure to failures, and thus, lower security of supply. At the same time, the secure development of the system cannot neglect cost considerations. This demands for adequate tools to assess and prepare for future scenarios of the energy transition. In this paper, a risk-informed approach for generation and transmission expansion planning is developed. The approach integrates cost-based generation and transmission expansion planning and risk-based transmission expansion planning. Interfacing these two models to perform coordinated generation and transmission expansion planning results in solutions that are cost-effective, account for the risk implications of the systemic changes, and guarantee system security. The risk-informed coordinated generation and transmission system expansion planning is performed for the Swiss power system which is modeled in full detail for the year 2050. To account for electricity exports and imports, the four surrounding countries are considered in an aggregated manner and their 2050 capacities are projected assuming a net-zero scenario. The results of the risk-informed coordinated expansion planning show that the pure cost-minimization approach applied to either generation or combined generation and transmission expansion planning does not necessarily lead to a reliable power supply in Switzerland. In fact, not accounting for reliability leads to expansion solutions that may incur up to 16 times higher demand not served compared to the reference year 2018. This highlights the importance of considering in-depth system security analyses in power system expansion planning.
Flexibility provision in the Swiss integrated power, hydrogen, and methane infrastructure
Akbari, Behnam; Garrison, Jared; Raycheva, Elena; et al. (2024)
Energy Conversion and Management
The renewable energy transition hinges on balancing energy supply and demand across seasons. This paper investigates the potential flexibility of Switzerland’s integrated power, hydrogen, and methane infrastructure to balance temporal mismatches while complying with national energy policies for sustainability and security. It develops an optimization method for energy system expansion and operation planning, filling crucial research gaps by (1) explicitly modeling power and gas transmission networks to guide technology placement and pinpoint network expansions, and (2) incorporating flexibility in power demand via shedding and shifting and in hydrogen and methane demands via price elasticity. The findings suggest that a 6.7-fold capacity expansion of variable renewables (i.e., photovoltaic, wind, run-of-river) by 2050 offsets nuclear phase-out and demand growth. The winter power gap is filled by power imports, hydropower generation, and gas turbines fueled by cost-effective hydrogen or methane imports. However, fuel embargoes escalate winter hydrogen and methane prices, reducing demand by 3.8%–10.4% and increasing domestic fuel production from biomass and excess renewable power in summer. To bridge the seasonal hydrogen and methane supply–demand gaps, up to 1.9 terawatt-hours of gas cavern storage is deployed in geologically viable locations, while costly tank storage plays a minor role. Power-to-gas requirements and power trade restrictions necessitate further renewable expansion, including 8.0 to 9.5 gigawatts of wind installations.
Recent climate impacts on run-of-river hydropower and electricity systems planning in Switzerland
Haddad, Yann Yasser; Gudmundsson, Lukas; Savelsberg, Jonas; et al. (2025)
Environmental Research Letters
The transition towards renewable energies together with climate change is rendering electricity systems more vulnerable to climate conditions and trends. This study examines the impacts of recent climate change and variability on run-of-river (RoR) hydropower production and electricity systems planning. We present an end-to-end pipeline to convert runoff and hydropower specifications into hydropower generation and subsequently integrate it into an electricity systems model. Applying this methodology to Switzerland, we provide a re-analysis of hydropower generation for each RoR power plant with capacities of 300 KW or more for the period 1991-2022. When aggregated on a national scale, our estimations match well nationally reported production and displays a climate-driven year-to-year variability. Our results show an overall tendency towards decreased RoR production in the past decades in Switzerland due to climate change (decrease in water availability). This trend was compensated at a national level with an infrastructure expansion. Based on the derived hydropower time series, we simulate the electricity system under scenarios with either no or a high renewable energy target and showcase contrasting sensitivities of electricity prices to climate variability.
Coordinated Generation Expansion Planning for Transmission and Distribution Systems
Raycheva, Elena; Han, Xuejiao; Schaffner, Christian; et al. (2021)
2021 IEEE Madrid PowerTech
This paper presents a coordinated approach to investments in a wide range of generation and storage technologies on the transmission and distribution system levels by coupling two generation expansion planning models. This coupling allows to account for both the centralized decision maker's perspective as well as the end consumer's perspective. We provide the location, type and capacity of new assets and account for the increased need for flexibility in case of investments in intermittent RES. The capabilities of the developed methodology are demonstrated using Swiss system data for the period 2020-2050. We show that the phased-out nuclear power will be gradually substituted by high shares of distributed PV and investigate the impacts of the replacement on the Swiss electricity exports/imports, electricity prices, investment costs and end-consumers' savings as well as the hourly dispatch.
Generation Expansion Planning in Switzerland Considering Climate Change Scenarios
Raycheva, Elena; Schaffner, Christian; Hug, Gabriela (2022)
2022 IEEE Power & Energy Society General Meeting (PESGM)
In this work a formulation of the generation expansion planning problem is applied to the detailed Swiss power system to study the impacts of possible climate-driven changes in hydro inflows on the country's generation portfolio in 2050. To capture the influence of electricity trade on the investment decisions, we include an aggregated representation of the production capacities of the surrounding countries under a net-zero GHG emission scenario and market-based tie line constraints. Our results show that investing in new generators in Switzerland is more economically viable than relying only on imports regardless of the simulated hydrological conditions. Despite the projected annual decrease in hydro inflows during a typical hydrological year impacted by climate change, the total system costs are lower compared to a typical year under current climate conditions. This is due to the fact that in the future we expect wetter winters and thus more water during months when the system load is higher.
The role of hydrogen storage in an electricity system with large hydropower resources
Gabrielli, Paolo; Garrison, Jared; Hässig, Simon; et al. (2024)
Energy Conversion and Management
Hydrogen is considered one of the key pillars of an effective decarbonization strategy of the energy sector; however, the potential of hydrogen as an electricity storage medium is debated. This paper investigates the role of hydrogen as an electricity storage medium in an electricity system with large hydropower resources, focusing on the Swiss electricity sector. Several techno-economic and climate scenarios are considered. Findings suggest that hydrogen storage plays no major role under most conditions, because of the large hydropower resources. More specifically, no hydrogen storage is installed in Switzerland if today's values of net-transfer capacities and low load-shedding costs are assumed. This applies even to hydrogen-favorable climate scenarios (dry years with low precipitation and dam inflows) and economic assumptions (high learning rates for hydrogen technologies). In contrast, hydrogen storage is installed when net-transfer capacities between countries are reduced below 30% of current values and load-shedding costs are above 1,000 EUR/MWh. When installed, hydrogen is deployed in a few large-scale installations near the national borders.
High Resolution Generation Expansion Planning Considering Flexiblity Needs: The Case of Switzerland in 2030
Raycheva, Elena; Garrison, Jared; Schaffner, Christian; et al. (2020)
Nexus-e: A platform of interfaced high-resolution models for energy-economic assessments of future electricity systems
Gjorgiev, Blazhe; Garrison, Jared B.; Han, Xuejiao; et al. (2022)
Applied Energy
Energy systems are transitioning toward sustainable power generation largely due to new policies that are motivated by climate and renewable generation targets. This transition is felt throughout the entire economy and is affecting the long and short term operations of the energy system. In the last decade, the research community has made significant efforts to model the energy transition and its impacts. Typically, these models focus on a limited subset of the different components of the energy-economic system, including investments in centralized and distributed generation, electricity markets, electric power grids, security of supply, and macro-economic effects. However, there are research questions that require the analysis of how these different aspects are connected to each other and how they may interact. Therefore, the research community has stressed the need to leverage models across domains to enhance the capabilities and robustness of their results. Due partly to the high complexity of combining models developed in tangential domains, few attempts have been made to model in full the interactions among the interdependent components of the energy-economic system. The Nexus-e: interconnected energy systems modeling platform aims to show how this gap can be filled by demonstrating that an interdisciplinary set of models can be integrated in a model framework by linking them through structured interfaces. This platform combines four bottom-up models that capture different aspects of the electricity system and one top-down macro-economic model to represent a much broader scope of the energy-economic system as compared to traditional stand-alone modeling approaches. In this paper, we study the benefits and limitations of the interfaces established among the modules in Nexus-e with reference to the Swiss electricity system in a European context. We demonstrate that prominent changes in operational behavior could drive investments and should therefore be assessed in a framework that considers both transmission and distribution systems in a coordinated manner. We show that the bottom-up investments and operations (transmission and distribution) can have an impact on the overall economy, which in response can affect the demand for electricity. Moreover, we demonstrate that the changes in generation mix and operation behaviors may have a significant impact on system security. For policymakers, the approach can provide spatially detailed power system transformation options that enable decisions that are socially, politically, and technically acceptable.
Modeling and Validation of Hydro Cascade Operation Considering Price Uncertainty
Libsig, Maxime; Raycheva, Elena; Garrison, Jared; et al. (2021)
Proceedings of the ASME 2021 Power Conference (POWER 2021)
Most studies involving the use of hydropower in an electric power system tend to consider the point of view of the system operator even though under liberalized markets in Europe, the operation of hydro units is set by the owner to maximize their profits. Such studies also often neglect uncertainties related to hydropower operation and instead assume perfect knowledge of the system conditions over the simulation horizon. This paper presents a methodology to overcome the aforementioned limitations. We optimize the operational choices of a hydropower cascade owner with multiple linked hydro assets and the ability to participate in several energy and reserve markets while also accounting for the impact of market price uncertainties on the owner’s operating decisions. The versatile optimization model created includes a detailed representation of any selected hydro cascade’s topology, constraints to reflect the machinery characteristics, and a rolling horizon approach to account for the price uncertainties in the daily operating schedule. The model is first validated using historical data for a hydro cascade in Switzerland and a perfect-knowledge approach. Next, price uncertainty is added to improve the historical simulation results and find a trade-off between accuracy and computational time.

Publications 1 - 10 of 12

Elena Raycheva

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