Seasonal flexibilisation: A solution for biogas plants to improve profitability

Abstract

It has been shown that the power demand-oriented operation of biogas plants contributes to the challenges of future energy systems with high shares of fluctuating renewable energies. This flexibilisation is usually short-term and can improve profitability. Long-term seasonal flexibilisation could further overcome present low heat utilisation rates due to the low heat demand of district heating in summer and constant biogas production across the year. To assess the benefits of seasonal flexibilisation for different biogas plants, we apply an existing model approach for analysing biogas repowering and optimising the combined heat and power (CHP) despatch. Plant-specific constraints and historical spot market data are used to determine power revenues, heat utilisation rates, greenhouse gas emissions and the profitability of the biogas plants. For different setups of CHP units and heat demand levels, the seasonal operation mode is compared with the non-seasonal reference mode. The economic benefit of seasonal flexibilisation is on average 10 €/MWhel when comparing the same rated power output and varies with plant size and CHP-setup. Increases in the heat utilisation rate are the main driver. Benefits increase with additional installed CHP capacities and rising heat prices. As gas production changes over the year, higher CHP capacities increase flexibility in winter and align the power market revenues of seasonal and non-seasonal operation. Very high heat prices even offset economies of scale. However, seasonal flexibilisation does not allow economic operation in Germany under current market conditions. The dependence on other sources of revenues and extended support schemes therefore remains.

Keywords

• Seasonal flexibilisation
• Biogas plants
• Despatch optimisation
• Heat utilisation rate
• Market value factor