Technical and Economic Assessment of Battery Storage and Vehicle-to-Grid Systems in Building Microgrids

Abstract

In an electrical microgrid, distributed renewable generation is one of the main tools used to achieve energy sustainability, cost efficiency and autonomy from the grid. However, reliance on intermittent power sources will lead to a mismatch between generation and demand, causing problems for microgrid management. Flexibility is key to reducing the mismatch and providing a stable operation. In such a context, demand response and energy storage systems are the main factors that contribute to flexibility in a microgrid. This paper provides an assessment of the technical and economic impacts of a microgrid at the building level, considering photovoltaic generation, battery energy storage and the use of electric vehicles in a vehicle-to-building system. The main novel contributions of this work are the quantification of system efficiencies and the provision of insights into the design and implementation of microgrids using real on-site data. Several tests were conducted using real on-site data to calculate the overall efficiencies of the different assets during their operation. An economic assessment was carried out to evaluate the potential benefits of coordinating battery storage with a vehicle-to-building system regarding the flexibility and cost-efficient operation of the microgrid. The results show that these two systems effectively increase the levels of self-consumption and available flexibility, but the usefulness of private electric vehicles in public buildings is constrained by the schedules and parking times of the users. Furthermore, economic benefits are highly dependent on the variability of tariffs and the costs of energy storage systems and their degradation, as well as the efficiency of the equipment used in the conversion chain.

The Potential of Vehicle-to-Home Integration for Residential Prosumers: A Case Study

“…The efficiencies determined ranged from 78% for charging and discharging with 2.8 kW to 86.5% for charging and discharging with 11.0 kW. Correia et al [20] were able to show, however, with regard to bidirectional DC charging, that a significant improvement in efficiency could be achieved by using a dedicated inverter. Measurements with a conventional inverter at 2.5 kW charging and discharging power resulted in an overall efficiency of 64.6%, and at 10 kW charging and discharging power in an overall efficiency of 80.4%.…”