The V2X ecosystem proposed in the Ev4Energy project aims to endow buildings, that have renewable energy generation and Vehicle-to-Grid chargers, with a better use of this energy, reducing costs and ensuring a high operational level for both the building and the vehicles. Therefore, the Ev4Energy project has as main objectives:
- Enabling the use of energy stored in car batteries connected to the building's V2X chargers to meet their energy needs;
- Integrated management of battery charging according to the profiles (and schedule) of individual vehicle use and anticipated energy needs for the building;
- Integrate “green” energy generation into the building's ecosystem, optimizing its use according to the characteristic production cycles;
- Enable the building's energy ecosystem to operate in "island" mode in the event of power outages in the public power grid;
- Ensuring the supply of the building's energy needs uninterruptedly, even when there are power outages in the public power grid;
- Equip the developed equipment with standard communication technologies that ensure its interoperability with other current and future commercial equipment.
The concept of energy ecosystem for buildings addressed in this project is generic and extensible to different application contexts. It can either be instantiated in a domestic context, in which the household building has two (or more) V2X chargers (and corresponding electric vehicles) and low/moderate power photovoltaic generation, or in a business context, in which the building/campus it can have tens, hundreds or thousands of V2X chargers and high power mixed generation (photovoltaic and wind).
The innovation of the proposed system results not only from the innovations intrinsic to the equipment that compose it, but, above all, from the combination and unique integration resulting from them. In this context, several elements are represented, namely:
- Public electric power distribution: supplies energy to the building when necessary;
- rivate electric power distribution: local network of the building that interconnects V2X chargers, local inverters (solar, stationary battery, or others), meters and loads.
- Building Energy Management System (SGEE): supplies energy to the building when needed;
- Charging Station Management System (SGEC): supplies energy to the building when needed;
- Solar Inverter (IS): Photovoltaic AC generation system. Included as an architecture validation element since it does not require development within the scope of the project;
- Bi-directional Stationary Battery System (SBBE): tationary (or second-life) battery charging and discharging system capable of rapid response to the occurrence of failure in the electric power distribution;
- Real-Time Communications Network: low-latency data network (Time Sensitive Network) for interconnection between the SGEE, V2X chargers and the SBBE.
- Meters (solar, building, …): equipment for measuring energy consumption connected to the SGEE through different communication technologies.
The proposed system addresses a wide range of challenges, of which the ability to instantly detect and react to the occurrence of the “island” mode of operation stands out, that is, when for some reason the distribution network is disconnected from the private distribution network of the building. The detection of the “island” mode is particularly difficult to detect in scenarios in which the local production at a given moment is close to the aggregated consumption of loads in the private network. Additionally, the system's reaction time is vital, as it must immediately isolate the private network from the outside (in order to prevent the flow of energy to the outside) and ensure that the quality parameters of the energy supply to the local loads do not exceed the standard nominal limits.
The following diagram shows the architectural view of the proposed solution.
Due to the response time of V2X chargers, which can even exceed 2 seconds after a power setpoint command, an element in the system is needed capable of reacting quickly and generating the pilot signal, keeping the system in operation during the transition period until the V2X chargers are capable of, possibly together with local renewable generation, supplying the energy needs of the building. This grid element is the Stationary Battery Bi-Directional System (SBBE).
Using the Building Meter, the Building Energy Management System (SGEE) detects the occurrence of “islanding” events and instantly activates, through the Real-Time Communications Network, the SBBE so that it generates the pilot signal that the remaining elements supplying energy to the local network (IS and V2X chargers) will use as a reference. Additionally, using information on the state of charge of the batteries and consumption forecast of the available electric vehicles, the SGEE controls, via the Bidirectional Stationary Battery System (SBBE), the start-up of the V2X chargers with setpoints suitable for their operation.
After the start-up of the V2X chargers, in view of the need to preserve the SBBE battery and not requiring its contribution to the system, the SGEE commands the transition of the generation control of the pilot signal from the network to one of the active V2X chargers through trading on the network Real-Time Communications Network.