NHP Technical News
On this basis, NHP does not recommend this approach as a
primary method to achieve load management.
Where this solution may be appropriate would be as a back-up
method to other solutions employed for the load management
task. For example, if a cloud-based billing and authentication
system is being used to perform load management, its
performance will be compromised whenever communication
between the EV charger and the cloud-based server performing
the system control is lost. The weakest link in the system is the
local telecommunications infrastructure – even the most reliable
cellular networks in Australia are offline once or twice each year
in some regions.
An implementation of electrical load management in
combination with cloud-based management could be set up
such that the contactors would only open in the event that
conditions indicating requirement for load shedding have been
met, and the load has not actually been shed by the cloud-based
system. The contactors shedding the load would be the last line
of defence before the medium and large circuit breakers at the
site started tripping, cutting both the EV charging loads and
potentially other loads at the site.
Local Smart Load Management
To avoid negatively impacting the batteries in the vehicles,
the load management system needs to communicate with
the charger, which is in communication with the in-vehicle
charge controller, and define a lower maximum charging rate.
For example, if the charger is capable of delivering 7kW, the
load management system might instruct it to reduce its peak
allowable draw to 1 or 2 kW for a period of a couple of hours,
while other loads in the building are high.
This approach is similar to the electrical load management
approach described above, in that the energy meters would read
the real-time usage of energy in the building, and a small smart
controller would then compute the available headroom for EV
chargers. The key functional difference is that instead of taking
chargers offline with a contactor (either individually or in groups),
the smart controller communicates with the network of chargers
via a gateway to command a reduced charging rate, or stop the
charging process in a managed way.
This solution is better for the vehicle batteries, and will allow for
much better control over energy in the building. Importantly,
this is a solution which is purely local in its execution. There is no
requirement for an internet connection, or an ongoing cloud-
based service subscription.
It is also vendor agnostic, from the point of view of the EV
charging equipment and upstream power distribution hardware
involved.
It should be noted that a smart system like this one cannot
readily co-exist with a cloud-based authentication and billing
system, or with an externally managed demand response system.
Two or three different systems all trying to track and modify the
charging behaviour in real-time, without coordinating with each
other, will not work.
System integrators and building automation contractors will be
able to customise system behaviours for individual sites. There
may be a desire to prioritise charging in certain parking locations,
for example, or have an override control in place to start charging
immediately if required.
Cloud-Based Load Management (Incorporating billing,
authentication, and reporting)
Systems enabling EV chargers to communicate with cloud-based
software have been developed around the world to enable user
authentication and billing. These systems typically involve apps
that can be downloaded to the smart phone of the EV owner,
with the EV owner’s credit card details stored by the operator or
an associated third party for billing purposes, much like Uber.
Some of these are proprietary to specific types of charging
equipment, or to specific energy companies, but increasingly
we are seeing open systems which will support any EV charger
supporting an up to date OCPP protocol.
While the primary purpose of these systems is billing and
authentication, the fact that these systems take a degree of
control over the charging process means that making them co-
exist with other smart load management systems is challenging,
as noted above.
The standard protocol that EV charging equipment uses is
OCPP, which is primarily designed for cloud-based billing and
authentication, but can also be used for load management. In
cases where billing and authentication are not required (see ‘No
Billing Systems/ Indirect Billing’ and ‘Billing for site access, not for
the usage’), this protocol could be used locally over EtherNet to
the charging equipment, either via CAT5 cable or WiFi.
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