Load Control through Smart Meters
Smart meters offer a number of ways to control and monitor loads in the home. This capability is sometimes called Demand Side Response or DSR. There are three basic methods of load control, the customer themselves acting on a signal, using meter itself to switch the load or, to use the HAN (Home Area Network) to switch a load remotely.
Why do we need to involve the Smart Meter in this process? The Smart Meter holds the tariff information and therefore is one of the key information sources in understanding when and how the load should be managed. It also records the amount of load reduced or increased under this control mechanism at half hourly intervals to match the way electricity is priced in the wholesale market.
These load control features are an optional part of the SMETS specification meaning that suppliers do not have to offer them to customers. If offered it is the customer's choice whether to use these services or not.
Currently only suppliers can use this functionality with the customer's permission, other parties such as DNOs (Distribution Network Operators) cannot use it. This is because the customer needs to give permission and understand the benefits and costs; only the suppliers are in a position to have this interaction with customers. Therefore it is likely that any load control for the electricity system will be through services offered by suppliers using their customer base.Customer advantages
- Save money
- Earn money
- Reduce emissions
- Control appliances.
- Balance supply and demand
- Improve security of supply
- Reduce expenditure on generation
- Help to integrate renewable energy
- Reduce expenditure on new distribution networks or the reinforcement of existing networks.
Customer acts on signal
This is the simplest, requiring just a message to the customer saying that they should reduce or increase load if they want to. The customer would already have agreed a contract showing the payment or price for the service they are providing. Here a Smart Meter is only needed to record the level of customer participation in changing their load.
Auxiliary load control switch
Smart meters with 5 terminals have an auxiliary load control switch (ALCS) within the meter itself which can be used to switch a second electrical circuit off and on. The switching pattern can be set via:
- A calendar in the meter providing the schedule, or
- The supplier sending ad hoc commands as required.
The second option here would allow the supplier to act in case of a system emergency, for example when wind generation is suddenly higher or lower then expected.
In both cases the customer has to agree to the overall process before the supplier can use it.
HAN Connected Auxiliary load control switch
Smart meters can also control circuits by sending on and off commands across the HAN thus removing the need for a circuit to be wired back to the meter. This method of control is known as HCALCS. Through this method up to 5 devices can be controlled independently (one of these could be the hardwired ALCS circuit mentioned above).
Electric car charging is a good example of how this could be used.
Smart Vehicle Charging
New smart meter-enabled tariffs can reward consumers that charge their electric vehicles (EVs) during off-peak times, such as at night, by passing through savings from using energy at lower price periods.
When combined with smart chargers consumers can automate this process, not only making it easier to shift charging to cheaper periods but also increasing the responsiveness of their vehicle to real time signals such as excess renewable generation or local grid constraints.
New two-way smart chargers can even enable vehicles to act as mini power stations, supplying energy back to the grid or even directly to consumers’ home. Given that cars spend over 90% of their time parked this opens up significant new capacity that would otherwise be wasted. Electric vehicles can also help optimise onsite generation such as solar by providing a battery bank to use surplus green and free energy that would otherwise be exported to the grid.
What is smart charging?
Smart Charging is when the charging cycle can be altered by external events, and the EV effectively integrates with the whole power system in a grid.
This means that, when permitted by the user, the charging of an EV can be paused or the rate of charge increased or decreased in response to commands received from energy network operators. A key feature of smart charging is that the user remains in ultimate control, setting the parameters to suit their needs while allowing some level of autonomy in return for lower energy costs.
Ultimately, smart charging will allow the user to specify when they require their vehicle (e.g. by 8:00am) and the system will provide the optimal charging profile to deliver lowest cost while ensuring the vehicle is ready when needed. At times of low demand, the system may charge immediately in one time block or at other times may charge in a series of time blocks in response to fluctuating demand, local network pressure and availability of renewable power but will always meet the specified needs of the user.
Proportional Load Control
The load control methods above have a serious limitation in that they can only switch a load on or off, ideally it would be useful to control some loads proportionally, for example to reduce to charging rate on an electric vehicle to half power.
This capability is being added to version 5 of the SMETS2 specification.
The new capability will be called the Auxiliary Proportional Controller (APC) and can be used in two ways:
- APC functionality that can be used in the same way ALCS
- HAN-connected Standalone Auxiliary Proportional Controller (SAPC) functionality that will connect to the HAN via the Communications Hub.
Questions & Answers
If the solar panels haven't been registered for FIT, then you can only get SEG (Smart Export Guarantee) payments. (Updated: 2021-04-21)
We suggest you check with your own supplier whether they can support export yet. (Updated: 2021-02-12)
- Active energy import (Wh) - this is what we are billed for normally
- Reactive energy import (varh)
- Active energy export (Wh) - this is your useful export power
- Reactive energy export (varh).