Comparative multi-criteria assessment of frequency containment reserve technologies – A case study of the German hybrid regulating power station

Abstract

In times of scarce resources and climate change, countries around the world have committed themselves to a carbon-neutral energy supply. Particularly mentionable in this endeavor is the German Energiewende, an undertaking which aims at cutting greenhouse gas emissions to 65% by 2030 compared to the year 1990 and reforming the German energy sector. More precisely, the future energy system relies more on a decentralized energy generation, realized by smaller and distributed generation units. The change from a centralized power generation, with bigger, conventional power plants, such as coal or gas plants, towards a decentralized power generation, requires more options for flexibility in order to handle the volatile character of renewable energy sources and to address the increased number of players in the energy system. An essential role to ensure grid stability in the energy system play the so-called ancillary services which help to stabilize the grid frequency when fluctuations occur. One tool of the ancillary services is the frequency containment reserve (FCR) which provides fast, regulating power to graduate short-term load changes and the concomitant changes in the grid frequency. Thus far FCR is mostly provided by fossil-based power plants. With the planned phase-out of coal power plants from the German energy mix new alternatives to provide FCR need to be assessed. In this thesis four technologies that are able to provide FCR are assessed on a multi-criteria scale: the HyReK, a hybrid regulating power station that combines a battery storage with power-to-heat modules, a 2nd life HyReK, which utilizes refurbished batteries from e-mobility, an electrolyzer in combination with a battery storage, as well as a pumped hydro storage (PHS). These technologies were assessed on four dimensions including eleven assessment criteria. The applied MCDA method was PROMETHEE, as it allows the graduation of uncertainties to some extent and is not allowing trade-offs between the assessment dimensions. No stakeholders were involved in the course of the thesis, instead five weighting scenarios were established to represent different preferences. In order to analyze the impact of the preference thresholds that need to be defined for PROMETHEE, a sensitivity analysis was conducted. In total 25 iterations of the MCDA were performed. It was concluded that the HyReK is the most preferable technology, being ranked first in 13 out of 25 iterations, followed by the PHS which was ranked first in ten out of 25 iterations. Although both technologies were ranked almost equally, the PHS is relying on natural and geographic preconditions and so was assumed to be less favorable than the HyReK. The technology 2nd life HyReK was ranked third in most of the iterations. It was concluded that, with room for improvement in the future, thistechnology would become more favorable, as some of its negatively influencing criteria are caused by the prototype character of the technology. The electrolyzer was ranked fourth in all iterations and can be seen as not favorable for the provision of FCR. It is expected that studies of FCR technologies will gain more attention in the next few years as technical alternatives will be needed in order to replace fossil-based power plants in the future.