Impact of flexible bioenergy provision on residual load fluctuation: a case study for the TransnetBW transmission system in 2022

Abstract

BackgroundThe transition towards a renewable based power system in Germany largely depends on variable renewable energy sources (vRES) like wind power and solar PV. Their high variability over time poses new challenges for power system stability. Bioenergy as a renewable source has already been established in recent years and has the capability to offset fluctuations from wind and solar PV and can therefore play a new role in coming years.MethodsThis paper describes how existing bioenergy plants can be operated in order to offset fluctuations in power systems, performing a power system modelling based on time series data. As sample transmission system (TS), TransnetBW has been chosen, one of the four German transmission systems. We modelled two different types of bioenergy plant clusters, one including solid biomass plants and the other cluster covering biogas plants and other plants with comparable characteristics. For the modelling of the operation of these clusters, we used registered time series of the years 2011 and 2012 for a total load and feed-in from wind and solar PV, which were projected for the year 2022. The flexible bioenergy clusters are operated in order to minimize fluctuations in residual load (RL). This approach served as the basis to assess how concepts for flexible bioenergy provision can contribute to the task of balancing future power systems based on vRES.ResultsBioenergy plays an important role in the renewable power supply of the TransnetBW TS, as it holds a share of 23.3% among the renewables projected for 2022. A flexible bioenergy (BE) provision allows for a reduction in daily residual load fluctuations by 30% compared to the non-flexible power generation from BE. Flexible BE effectively offsets high fluctuations originated from the feed-in of the substantial solar PV installations in the TS and also contributes to serve the peak load. But in contrast to regions with higher renewable shares from vRES, the amount of avoided BE power production in times of negative RL (excess power from renewables) is still negligible for the 2022 time frame investigated and thus reducing the immanent requirement for flexible BE.ConclusionsIn line with existing studies, the results show that bioenergy is already a valuable asset to achieve the targeted REN shares and can support the integration of the large vRES capacities in coming years, if produced flexibly. Operating biomass installations in a flexible manner effectively reduce daily fluctuations in RL, allow for a better integration of vRES and contribute to cover peak power demand. But from the findings of this case study, we conclude that the focus in the near-term should be on the efficient utilization of BE as the top priority until the demand for flexible BE provision is progressively increased with rising shares of vRES. Giving the regional differences, it should be stressed that the regional context, the relative share of wind and solar PV in the power system and therefore the investigated time horizon are important for defining the role of flexible bioenergy in the years to come.