Study of an nZEB Office Building with Storage in Electric Vehicle Batteries and Dispatch of a Natural Gas-Fuelled Generator

Abstract

The rapid electrification of vehicles has led to a great increase in numbers of charging stations and a growing appetite for charging power, with stochastic charging behaviours heavily loading the electricity grid. The upcoming difficulties and increasing costs associated with electricity production will require a rapid development of smart grids and city networks. Smart micro-grids established in nearly zero-energy buildings (nZEB) are a promising strategy to support grid stability and resilience at a reduced cost. A significant amount of electricity storage capacity is necessary for optimal dispatch of the self-produced photovoltaic electricity. For office buildings, this capacity can be provided by the aggregate battery storage of the employees’ electric vehicles, which connect to the smart grid during working hours for charging and, if allowed, for discharging. An additional, fully controllable electricity source that is necessary to support an optimal micro-grid is the internal combustion engine-powered generator that is present in every commercial and office building as an emergency power supply. In the current study, a preliminary investigation of a smart micro-grid in a near zero-energy office building with a 218 kWp rooftop photovoltaic installation is carried out. The required electricity storage capacity is supplied by the employees’ electric vehicles, which stay connected to the building’s in-house chargers during working hours. The optimal rating of the natural gas-fuelled GenSet is determined based on a system’s operation and control study. Optimal dispatch of the different power sources to support the building’s autonomy and seasonal timing of electricity export to the grid is studied versus the electricity demand profiles of the electricity grid.

The Interaction between Short- and Long-Term Energy Storage in an nZEB Office Building

“…During working hours, the car batteries may discharge, when necessary (up to a 30 kW maximum total discharge power) to cover building loads. An Soc min optimization study has already been carried out using GenOpt for a similar system, giving the value of Soc min = 0.36, which is adopted here [40].…”

“…On the other hand, another electric power source is already available as standard equipment in commercial and public buildings in the form of diesel-powered engine generator sets for emergency power supply. A study of the effect of fueling a building's genset using natural gas [40] pointed to its optimal sizing as an additional power source, resulting in limited electricity imports from the grid. Now, the problem with this type of configuration is caused by the lack of long-term electricity storage.…”