Techno-economic analysis of grid-connected PV and second-life battery systems for net-zero energy houses

Net-zero energy houses (ZEHs) rely on energy-efficient building design and the incorporation of distributed generation and battery energy storage units. Nevertheless, two primary concerns arise: high investment cost of these units and harmful environmental impact of batteries. Using second-life batteries can overcome these concerns by reducing the cost of photovoltaic (PV)-battery systems and mitigating the adverse environmental effects of battery supply chain. Therefore, this study examines the techno-economic feasibility of utilizing second-life batteries for PV storage in grid-connected ZEHs in two provinces (Antalya and Istanbul) of Türkiye. First, two ZEHs with air-to-water heat pumps are designed using BEopt software. Next, the optimal PV-battery capacity in the ZEHs is determined using HOMER Grid software. Finally, the economic feasibility of using three types of batteries (new lead acid, new Li-ion, second-life Li-ion) in ZEHs is compared. The optimal design for a typical ZEH comprises a 5.92 kW PV and an 8.96 kWh second-life Li-ion battery in Istanbul (northern Türkiye), yielding an NPV of $10,906, and a 7.54 kW PV and an 11.52 kWh second-life Li-ion battery in Antalya (southern Türkiye), yielding an NPV of $16,402. The results indicate that using second-life Li-ion increases the NPV of PV-battery systems by 15 % in Istanbul and by 21 % in Antalya. The feasible system configuration categories for Türkiye's economic and climatic conditions are ranked as: PV-second-life Li-ion > PV-no battery ≅ PV-new Li-ion > PV-new lead acid. Incentivizing the use of second-life batteries due to their environmental contribution could result in an even higher NPV increase.