Balancing services by run-of-river-hydropower at low reservoir amplitudes: Potentials, revenues and emission impacts

•Low reservoir amplitudes in run-of-river hydropower enable extensive grid balancing.•1 MW of hydropower can facilitate grid integration of up to 11.6 MW of wind or PV.•Potentials for negative balancing services significantly higher than for positive.•Providing balancing services reduces overall energy production.•Nevertheless balancing services can increase the total incomes. The increasing shares of wind energy and photovoltaics in many countries challenge the energy systems in a twofold way. On one hand, there is an increased need for balancing energy in order to compensate abrupt changes in load or power generation. On the other hand, fossil plants being important providers of balancing services are gradually driven out of the system creating a need for renewable substitutes. Due to strict requirements on the upstream water level regime German run-of-river (ROR)-hydropower has until now remained largely unused for providing positive balancing services. However, in this paper we present a novel optimized operation scheme allowing ROR-plants to exactly keep their production schedule and, in addition to that, provide positive and negative balancing services even under these constraints. Our simulations on an exemplary power plant with a very low head show that huge unused balancing power potentials can be expected for ROR-hydropower in Germany enabling a multiplication of fluctuating renewable energy sources. Next to these potentials under current market conditions, this paper elaborates the economic and ecologic aspects of balancing operation.