Renewable Energy Sources (RES) are expected to become the most relevant source of energy and will replace traditional carbon-based energy. RES are usually being used to provide electrical energy, these only count for around 20% of the primary energy being utilized, the residual part is energy for heating and cooling, for the industry, and mobility purposes.
The plan is to use RES to support heating/cooling and mobility: the approach is called “sector coupling.” Typical ways of using electrical energy for heating and cooling are heat pumps, in mobility, electric vehicles (EVs) play the dominant role. The batteries of the EVs will be used to desynchronize the generation and consumption of electrical energy.
With the generation of green hydrogen and the feeding of thermal reservoirs, another way of storing energy is available. In this article, the focus will be on the utilization of EVs and fixed batteries supporting e-mobility. EV batteries do not only provide flexibility while being charged and storing energy (V1G) but also offer the technology to inject power into the local distribution grid – vehicle to grid (V2G).
In an EU Horizon-2020 funded research project, MEISTER, the potential of the V2G technology has been checked based on 3 use cases:
• Injecting power when the load in the low voltage grid segment is high: this reduces the power transfer across the transformer;
• Injecting power with a controlled phase shift between current and voltage: this improves the efficiency of the energy transfer whenever reactive power is disturbing the grid; and
• Taking power from the grid by charging and injecting the same amount of power in the same grid segment whenever grid harmonics occur, which exists whenever a wrong frequency is being fed into the grid by a local generation site.
V2G technology has improved the technical situation of the 3 use cases and reduced problems with harmonics. The selection and control of the charging devices have been performed by a Virtual Power Plant (VPP) from CERTH/ITI (Greece) at the request of the local Grid Control Center (GCC) or even faster, by the Supervisory Control and Data Acquisition (SCADA) level. The communication is based on standard IEC protocols, in this case, IEC 60870-5-140.
The easier use cases of V1G character are the reduction of charging power – thus reducing the load in the grid and the start of charging when local RES generation is too high – thus avoiding the shutdown of RES devices in the grid. By that, it could be shown that the EV batteries can provide relevant flexibility and stabilization services to the electrical grid as a value add function – without additional investments into grids and devices and by control of a smart VPP.