Contributions of flexible power generation from biomass to a secure and cost-effective electricity supply-a review of potentials, incentives and obstacles in Germany

Background: With wind power and photovoltaics, volatile renewables have emerged as central pillars of the energy transition. This increases the demand for flexibility options to compensate fluctuations in power generation. Focussing on the role of bioenergy as a renewable flexibility option, this article seeks to address two questions. The first is whether there is an option value of bioenergy as a provider of low-carbon flexibility in a future power system, which might justify continued technology-specific deployment support. The second question is whether existing market and policy incentives are effective in activating flexibility potentials, and what perspectives exist for increasing flexibility incentives. Methods: The article follows an interdisciplinary approach. First, technical potentials for flexible bioenergy plants and potential systemic contributions are examined. This is followed by an economic assessment of what flexibility incentives are provided by relevant market and policy framework conditions. Findings: Power from biomass can be well suited to provide flexible generation for grid stabilisation and residual load balancing. Biogas plants require an increase of nominal power over rated power, whereas the technical flexibilisation potential of solid biomass plants depends on specific technologies. Particularly, small-scale combined heat and power systems can deliver fast responses. For existing biogas plants, the Renewable Energy Sources Act's (EEG) flexibility premium and balancing market revenues have incentivised some changes in the production behaviour and investments in plant flexibilisation. However, decreasing spot market price levels and decreasing price variance reduce incentive strength. This also limits flexibilisation incentives for solid biomass plants. For new biogas plants, the EEG's remuneration rules set effective flexibility incentives, but 2014 reductions in remuneration rates have significantly slowed down the expansion. Conclusions: Given high technical potentials for flexibility provision, there is an option value of keeping bioelectricity in the technology mix until more is known about its future competitiveness with other low-carbon flexibility options. To maintain this option value, there is a case for setting policy incentives in a way that continued technological development remains possible. A stringent climate policy could accelerate structural change in the electricity sector, to allow for market price signals which incentivise low-carbon flexibility provision.