Electrical vehicle charging and energy management
Many countries worldwide have announced plans to phase out the use of fossil fuels for mobility and want to impose the use of electric vehicles. By Ian Richardson.
Although these are very challenging targets, many countries are very serious about this. By 2030:
- Under the emissions projection report released by the Australian Federal Government in December 2020, the uptake of electric vehicles is projected to increase from one percent to 26 percent of new vehicle sales, equating to more than one million electronic vehicles (EVs) operating in the light vehicle sector.
- The Biden Administration is expected to deploy more than half a million new public charging stations in the US.
- The UK wants to ban fossil fuel cars altogether.
- With its Green Deal, the EU commission wishes to lower its emission by at least 55 percent compared to 1990.
This clearly shows that while the eCar may still be scarce on the road today, this could be about to change dramatically. If one in four households has an eCar ten years from now, those homes will need to manage a new, energy-hungry element. If taking the car to work, several of these hungry elements will want to be fully charged again by the end of the working day. If not charged during working hours, the hungry element will seek to satisfy its energy appetite when it arrives home.
It will therefore be paramount that we make the best use of our available energy, preferably green energy rather than just tapping into energy that is converted from fossil fuels. The ideal scenario would be that what we consume can be produced entirely at the site where the charging happens and there is still sufficient energy to also run the rest of the applications we have in the building (lighting, HVAC appliances, etc).
It would be just as ideal that we can also use the storage capacity of our eCars – in addition to
a stationary battery storage – to save energy when it is abundant and to tap energy when grid production is low.
It is therefore clear that homes and buildings will need to evolve to be able to manage this. There will be a need for a ‘manager’ of the customer’s energy requirements instructing the different energy consuming/producing elements in a home or building and keeping an eye on whether there is sufficient energy to go around.
There are already solutions on the market that allow buildings to solve this exercise of performing load management in a home that also has a charging station and it can be easily integrated into existing KNX smart buildings.
KNX is a control system that was developed to allow products from various manufacturers to work seamlessly together. The system operates on a standardised bus cable with a common language, allowing different products to work together. It controls all aspects of building control such as: lighting, heating, cooling and ventilation, blinds/shutters, security and door communication systems, audio and video, metering, and energy management.
With KNX there are no more problems of isolated devices or systems not being able to talk to each other. It also means all building control functions can be controlled through the one central system without the need for additional control centres.
As an example, consider a commercial building with multiple charge stations. Many EV chargers are utilising a ModBus RTU interface which is then integrated in a KNX system, allowing multiple charging stations to be monitored and managed. ModBus RTU is a common industrial communication system which can easily interface to the KNX building management system.
The interface provides the ability to:
- view the last charge and overall energy consumption
- view the real-time loading current
- view the charging start and end time, and
- is able to perform the required load management.
When it is required to utilise more sophisticated energy management algorithms, the EV charger can then also be combined with an extra KNX server or visualisation software.
A further product is currently under development from another KNX member that will allow the connection between a smart meter and a possible charging station.
However, in international standardisation, there are currently activities that wish to solve this exercise in a technologically neutral way. The standard prEN 50491, General requirements for Home and Building Systems (HBES) – Part 12-2: Smart grid – Application specification, is designed to provide a technology independent means to manage consumption and production of energy in smart homes and buildings. KNX has been helping to shape this standard and will provide KNX members with specifications on how this can be realised with KNX technology. The standard will abstract all energy consumers and producers in a home or building as elements called ‘resource managers’ (RMs). Such RMs can be a single product (like a charging station), however they could just as well ‘hide’ an entire application domain (like lighting control) or even an entire system (like a complete KNX installation). All RMs are directed by a central intelligence, the Customer Energy Manager (CEM). The interaction between the CEM and the RMs is defined by several different control strategies, which are referred to as ‘control types’.
As for eCar charging, such a resource manager would be the charging station, as the communication between the charging station and the car is laid down in another standard, the ISO 15118-2 and upcoming part 20. This standard defines two charging strategies, the dynamic and scheduled mode, the basic difference being that:
- in the case of scheduled mode, the eCar keeps the complete control over the charging process, and
- in dynamic mode, the charging station acts as charging controller, once the energy demand, the departure time and other charging parameters have been exchanged between the car and the charging station.
The control types from the prEN 50491-12-2 that is most ideal for the eCar charging application in dynamic mode is without any doubt the fill rate-based control type, as in this type the eCar is regarded as a storage/buffer and the departure time can be modelled as the fill level target. For the scheduled mode, the power enveloped based control defined in prEN 50491-12-2 seems the best option to keep the EVs power consumption over time between certain limits.
The above concepts could already be fulfilled using KNX classic methods like Group Communication. New KNX IoT devices using the KNX IoT Point API with IPv6 will allow communication of larger data sets which will provide greater flexibility.
Our mobility world is changing, the inevitable implementation of a growing EV based transport society will require additional approaches to our energy management needs. Fortunately, the KNX system, compliant with the Australian Technical specification SA/SNZ TS ISO/IEC 14543.3, is poised to take up these challenges and integrate them into the home and building automation system.
Ian Richardson is chairman of the KNX National Group Australia.