Second-life batteries for intermittent renewable energy sources: economic optimization for a 2.1 MW Danish PV plant

Renewable energy sources are crucial against climate change, while intermittent nature brings challenges. Besides, excess generation often faces curtailment due to grid limitations and demand fluctuations. Second-life batteries (SLB) can offer a cost-effective and, more importantly, sustainable solution for energy storage. This paper presents a simulation-based case study analyzing the economic profits of integrating a 4.3 MWh SLB into a 2.1 MW photovoltaic (PV) plant. The recorded one-year high-resolution PV generation data from May 2014 and the tariff from the El spot market are used. Three scenarios are explored: 1) Directly selling PV production, 2) Optimizing the operation of the 4.3 MWh SLB, and 3) Optimizing the operation of a new battery where the capacity ratio between the new and the above SLB ranges from 0.5 to 1.0. To account for recent electricity price shifts due to the 2021 Global Energy Crisis, the study includes a comparative analysis using the 2022/2023 tariff. Results show that in 2014/2015, utilizing the SLB increased profit by 7.4%, while a new battery could achieve that with less than 60% of the SLB’s capacity. After the energy crisis, earnings from the SLB increased by 19.4%, and a new battery would require around 60% of the SLB’s capacity to achieve this increase. Furthermore, the post-crisis scenario showed a 496% profit increase for directly selling the PV production and a 563% increase with the SLB, underscoring the significant impact of rising energy prices on the viability of PV-battery energy storage systems.