An overview of the concept and technology, initial field tests and linking with a Smart Meter Gateway
Demand Response (DR) programs can help energy suppliers and grid operators to control consumers and decentralized generators and can result in flexible pricing in California, Japan and Europe. One widespread program is the open source interface OpenADR 2.0b, now also implemented in the Hamburg ELBE project.
OpenADR supports utilities in managing the growing pool of Distributed Energy Resources (DER), which includes renewable energy, energy storage and charging of electric vehicles. The standard supports communication with all DER facilities to manage changes in load curve, energy usage and performance characteristics.
ChargePoint and partners currently analyse latency times, scalability and a second wireless area network interface in parallel to the SMGW
The energy supplier or network operator takes on the role of the "Virtual Top Node" (VTN), while customers - e.g. a charging network operator (CPO) or a building manager - take on the role of the "Virtual End Node" (VEN). The signals can be sent with a time advance of days or hours, the commands can be set in percentage or absolute terms, e.g. in kW or amperes.
2. Technical implementation:
In the ELBE project, a minimal implementation of OpenADR 2.0b was first carried out in order to test the chain of commands from the VTN (here: distribution network operator StromnetzHamburg) to the VEN (here: CPOs like ChargePoint) and from the VEN to the charging infrastructure. The network operator sends a command for a "grid ID", i.e. a network connection point, to the CPO's backend.
Implementation of OpenADR 2.0b in Hamburg:
We chose OpenADR because of its simplicity, efficiency and yet high security level (TLS 1.2).
Currently, a daily load reduction - an event - takes place for 30 minutes to 50% of the load at the grid connection point.
Both distribution network operator and CPO know which charging capacity is installed behind this point. At each event, the CPO automatically controls the charging infrastructure according to the rule agreed with his customer, for example that all charging points reduce load equally.
Since 2020Stromnetz Hamburg and ChargePoint carried out several hundred field tests. This example took place at a car dealer in August 2020:
1. Time:3:59:55 p.m.: Charging at full power (21.3 kW)
2. 4:00:00 p.m.: DNO sends event to reduce load to 88kW (to 25% of max. power) for 5 minutes, sends to grid ID.
3. 4:00:20 p.m.: station reduces load (reduction starts 20-30 seconds after command, reaction time depends on vehicle), to 15,8kW.
• Message to customer on Smartphone:
Warning: the supplier has reduced the power supply to xxx due to high demand. Possibly your vehicle is not being charged at full speed.
A standardized DR program is now available thanks to the IEC standardization initiative: The OpenADR 2.0b specification has been recognized as an IEC standard, see IEC 62746-10-1 ED1. (https://webstore.iec.ch/publication/26267). In the UK, it will be introduced as a national standard.
In Germany there is a need for action, as there are a variety of technical specifications from distribution network operators: Since 2019 load management must be installed for charging stations with a connected load of 12 kVA or more. This results from the Technical Application Rules (TAR) (e.g. VDE- AR-N 4100, VDE-AR-N 4110). However, how these TARs are implemented has not yet been uniformly regulated. The ELBE project and OpenADR is one recommended path for DR. Next step will be a call for experts on the basis of the HamburgOpenADR version.
The project also discusses the inclusion of a smart meter gateway architecture given the coming rollout by the distribution network operators in Germany:
The network operator communicates a shed load signal via OpenADR to the CPO and the CPO’s backend then routes this signal through a smart meter gateway (SMGW) architecture to the charging stations. This is end to end encrypted via the controllable local systems channel provided and via the provision of TLS 1.2 from CPO backend via SMGW to the charger. ChargePoint and partners currently analyse latency times, scalability and a second wireless area network interface in parallel to the SMGW.
The potential in other markets like California can show how charging tariffs might evolve in Europe:
Example: California, energy supplier Pacific Gas and Electric (PG&E)
PG&E offers two tariff plans for electric vehicles for private customers:
- Home Charging, EV2-A combines the electricity costs of the vehicle with those of the home.
- EV-B includes the installation of an additional meter that separates the electricity costs of the vehicle from those of the home.
Both EV2-A and EV-B are tariffs where the consumer pays based on the time of day when electricity is used. EV-B should be more comparable with the situation in Germany, where a separate meter is usually installed for charging, at least in the wallbox itself. Therefore EV2-B is visualized.
The cost of EV-B is lowest from 23.00 to 7.00 when demand is at its lowest, so this is the best time to recharge an electric vehicle.
Prices for private households in cent per kWh, EV2-B tariff: