Optimized Energy Management of a Solar and Wind Equipped Student Residence with an Innovative Hybrid Energy Storage System

Grid-connected Energy Storage Systems (ESS) are vital for transforming the current energy sector. Lithium-Ion Battery (LIB) technology is presently the most popular form of ESS, especially because of its fast response capability, efficiency, and reducing market prices, but is not always preferred for long-term storage, due to its relatively shorter lifetime. A Redox Flow Battery (RFB) on the other hand has a higher lifetime and better long-term storage capability, but has a higher upfront cost and reduced round trip efficiency. A Hybrid ESS (HESS) consisting of LIB and RFB offers the advantages of both technologies, thus making the ESS more economical and flexible to use while also improving the cycle lifetime of individual ESS. Such a grid-connected HESS is planned and installed for a student residence at Bruchsal having 126 apartments for 150 students and equipped with 220 kWp photovoltaics and 10.5 kWp wind-power. Real-time high-resolution data of the residence’s electrical load and energy generation are collected and used to optimally control the HESS. Additionally, the RFB is also used as heat storage, which supports partial heating requirements of the residence. In the present work, an Energy Management System (EMS) is deployed which not only controls this conglomerate but also optimizes its operations in real-time. The HESS is optimized two folds where it is operated with a fixed priority based strategy to improve the operational efficiency. Secondly using solar and load predictions, optimal charging schedules of the individual ESS are estimated. Based on the schedules the ESS are charged at its optimal charging points thus increasing charging efficiency and at the same time it avoids the ESS from staying at high SOC ranges for long time thus reducing ageing. Results based on real life operations based on the proposed methods are provided in this work.