Abstract

To provide flexibility in power systems, hydropower frequently operates in strong hydropeaking schemes (i.e. resulting in severe flow flashiness) that harm the downstream river ecology. Energy storage systems are becoming an accessible source of flexibility, and when combined with new transmission infrastructure, could alleviate hydropeaking. Here, we explore how these technologies can mitigate severe hydropeaking with an emphasis on the temporal and spatial river flashiness. More precisely, in a case study on Chile for a fully renewable system (planned with a multi-objective framework, LEELO), we illustrate the costs of mitigating hydropeaking, select efficient solutions, and discuss the overall resulting storage needs. Our findings are relevant for decision makers related to river ecology. From the found trade-offs, we see how system-wide flashiness can be mitigated for little extra cost: 5-9% by relying more strongly on other storage technologies (depending on the level of flashiness), and only 1-4% if transmission expansion is considered. When focusing on the main reservoirs of each basin and the seasonality of their flashiness index, we observe that to avoid sacrifice zones the prescribed system-wide hydropeaking index needs to be very small. Minimizing hydropeaking requires more power capacity but less energy capacity from other storage technologies.