For the energy transition to work, electricity consumers, decentralized and centralized electricity producers as well as storage elements must be intelligently connected in future. This is where electric vehicles come into play: they are not only power users but also potential storage systems for electric energy that could be used to stabilize the grid – provided electric vehicles are part of the communication system for the smart grid. IAV has a wealth of experience with the requisite communication protocols and is helping to enhance them through its involvement in standardization bodies.
The energy transition is turning our power supply upside down. Instead of generating energy to plan with a few centralized power stations, the future is set to see more and more decentralized systems deliver electricity with yields that are virtually impossible to predict. The aim is to generate power from renewable energies (like wind farms, photovoltaic systems) and optimize the availability of energy for the consumer in line with demand using appropriate storage systems and intelligent control (smart grid). Supply and demand must always be balanced in the power grids – otherwise there is the risk of blackouts. This is why the power companies still need to keep operating many of their conventional power plants to hedge any deficit.
Alternatively, surplus energy could be stored and fed back into the grid whenever needed. With this in mind, we are doing extensive research into new storage technologies, such as hydrogen storage and Redox-Flow batteries. “Electric vehicles with their high-voltage batteries lend themselves as decentralized systems for electricity storage”, explains Ursel Willrett, senior technical consultant for e-mobility infrastructure systems at IAV. “These days, they come with storage capacities of 20 to 30 kilowatt hours. Proceeding from a million electric vehicles in Germany, this produces a total storage capacity of about 20 gigawatt hours, comparable with the capacity of all German pumped-storage power plants.”
Stabilizing energy supply
Particularly in combination with the decentralized production of solar power, electric vehicles make ideal energy storage systems. Many private homes now have solar panels and generate part of their energy need themselves. Any excess production is fed into the grid. If more energy is needed than the domestic system can provide, connection to the grid makes up the balance. In future, it will be possible to avoid some of this interaction with the public power grid because with the introduction of electric mobility more and more households will have electric vehicles and hence battery storage capacity. “An electric vehicle at home could help to stabilize the supply of energy and ease strain on the power supply”, Willrett says. “It would not be necessary to upgrade building service connections at high cost to recharge electric vehicles or feed surplus solar power into the public grid.”
Smart-home concepts will be essential for using electric vehicles as decentralized electricity storage systems. They are an Internet of Things application and have the aim of intelligently connecting all system components, such as photovoltaic system, thermostats or lighting in the home, and in this way permit local load management. “An electric vehicle can be integrated into a home energy management system (HEMS) as an energy storage device”, Willrett says. “Surplus energy from the photovoltaic system is stored in the vehicle and used either for driving or for feeding it back to other power users in the home.”
Open standards for integrating future devices
This demands an intelligent communication system that integrates various system components. “Some solutions available on the market work with proprietary communication protocols. They often come with the drawback of not being compatible with new components”, Willrett reports. “This is why we need open standards that are supported worldwide by many manufacturers and permit a straightforward integration of future elements, such as electric vehicles, by plug and play.” Today, the protocols most of the world uses for home energy management systems are SPINE (driven forward in Europe by the EEBus initia- tive), SEP 2.0 (USA) and Echonet Lite (Japan).
Recharging stations in Europe today use the Open Charge Point Protocol (OCPP) which, among other aspects, controls contract management. In future, this is to fall under international standard IEC 63110 which is currently being drawn up. The specifications for communication between vehicles and the charge point (at home or in public) are laid down in ISO standard 15118. This describes all functions that are needed for data communication – such as for accessing tariff information, scheduling recharging times and bidirectional charging. The electric vehicle’s communication protocol can be translated into the communication protocol of the smart grid or smart home via a gateway.
IAV is actively involved in various standardization projects. “We benefit from comprehensive expertise in communication protocols, system architecture and concept formulation as well as in integrating various devices into smart grids and smart-home systems”, Willrett says. “This puts us in a position to provide support in integrating all of these elements – e-vehicles in particular – into the smart grid or into smart-home systems.”