We need energy flexibility to overcome major challenges in the energy transition in the best possible way.
S2 is a communication standard for energy flexibility in homes and buildings, designed to keep you comfortable.
You can jump to the Github or Whitepaper immediately, or keep reading for an introduction in the S2 Standard.
What is energy flexibility?
Energy flexibility is the ability to alter the use of energy without a significant impact on comfort. PV systems, EV chargers, batteries, and (hybrid) heat pumps are very suitable for this purpose, especially when they are combined in a smart approach.
Some examples of energy flexibility:
As long as an electric vehicle is sufficiently charged an EV charger might delay charging to a later moment.
A heat pump might generate a bit more heat at some point, so it needs less energy later.
Why do we need energy flexibility, and a standard for it?
We need energy flexibility to overcome major challenges in the energy transition.
Take for example all-electric homes: they can easily generate 5 x as much energy flows compared to conventional homes.
Electrification of transportation, heating, and industry is also surging. This boosts electricity demand and peak load, stressing the grid. Despite growing sustainable electricity production, the energy system faces challenges meeting rising demand and supply. Grid upgrades lag, forcing grid operators to seek alternative solutions.
Using the flexibility within the energy system, where users adjust consumption or store energy, can ease grid strain. It also allows us to integrate more renewable energy into our power grid. However, lacking a standard for managing millions of devices complicates this and raises costs. A standardized approach to energy flexibility is crucial.
S2 is such a standard. S2 is a communication standard for energy flexibility and energy management. S2 helps to simplify the use of energy flexibility of smart devices in homes and buildings.
S2 works with energy usage characteristics, which makes it a particularly future-proof standard. It gives prominence to user convenience and manufacturer choices.
The S2 standard
In S2, there are two entities that communicate with each other. The Customer Energy Manager (CEM), which orchestrates the flexibility provided by the appliances in the building.
Based on optimisation targets and additional external information and incentives, it decides how to use that flexibility by sending instructions to these devices. These instructions are sent by using the S2 communication protocol.
The CEM does not connect directly to the devices, but to the Resource Managers (RM) of these devices. This Resource Manager communicates the energy flexibility information of the device to the Customer Energy Manager (CEM), and only that. Resource Managers can be integrated into the smart appliance, but they can also work remotely, for example in a cloud service.
"In S2, the Resource Manager is concerned with how a flexible device can behave.
The Customer Energy Manager is concerned with why it should behave a certain way."
Focus on Energy Management
S2 focuses on the exchange of standardised energy flexibility information between energy management systems (EMS) and energy equipment in buildings. It has been a conscious decision not to extend that scope to include other functionalities such as device configuration and remote maintenance functionality.
S2 works with eight so-called 'Energy Flexibility Patterns', rather than relying on specific use cases for each type of device. Limiting the scope to energy flexibility makes it easy to implement and maintain S2. Because the energy management capabilities are generic, it is easy to add devices in the future, making it energy transition-proof.
S2 benefits for manufacturers (OEM’s)
S2 is not meant to replace existing protocols, but rather to provide a universal language for energy flexibility.
S2 offers freedom and security for manufacturers of Energy Smart Appliances.
Both the Customer Energy Managers (CEM) and Resource Managers (RM) can be integrated into the (firmware of the) smart energy devices, but can also run alongside them, for example in cloud services, in the meter box or smart meters, or on smart home controllers such as Apple TV.
This flexibility also means that phased implementation is possible: start with the cloud and integrate later in the firmware.
The S2 approach also ensures the integrity of OEM devices and OEM business approaches. S2 does not overwrite or interfere with internal logic and security of devices, nor does it require other OEM information such as runtime, or maintenance information.
S2 is not a replacement for existing OEM protocols. S2 is modelled in SAREF, which is a shared model of consensus that facilitates the matching of existing assets in the smart applications domain. S2 can also be easily integrated with other protocols.
Resource managers can be created for all kinds of smart energy devices, such as EV chargers, heat pumps, inverters, batteries / storage devices, white goods, as well as swimming pools and commercial cold stores.
S2 is published as an official European standard under the reference EN 50491-12-2. The management of S2 is open and well managed by the standardisation body CENELEC.
A WebSockets and JSON based protocol specification implementing the EN50491-12-2 "S2" standard for home and building energy management.
The backend of the s2 analyzer is tasked with processing, forwarding and validating all messages between the S2 resource manager (RM) and the customer energy manager (CEM). To use this backend, the RM and CEM connect with the S2 analyzer instead of connecting directly with each other.