Is your inverter 'DRM compliant'?

30 November 2016 by
Is your inverter 'DRM compliant'?
AC Solar Warehouse Pty Ltd, Rob Birchall

As of October 9 2016, all grid connect inverters installed in Australia have to meet the full requirements of AS4777.2:2015.  This resulted in a significant shake up of the inverter market, with literally hundreds of models of inverters being withdrawn from the market due to non-compliance.

A key requirement of AS4777.2:2015 is Demand Response Mode (DRM) which enables the inverter to respond to signals sent to it remotely. These signals trigger the inverter to change the mode of operation, potentially turning it off, on, or ramping the output up or down.  AS4777.2:2015 Section 6.2.1 states: “The inverter shall support the demand response mode DRM 0 of Table 5. The inverter should support the other demand response modes of Table 5.” So while support for all demand response modes is not currently mandatory, all inverters are required to support demand mode DRM 0 (which disconnects the inverter when the signal is received).

Why would a solar system owner be interested in implementing DRM functionality?

A remote DRM signal could come from any source, but the most commons ones might be a building management system, an electricity utility, or a load aggregator.

A building management system might control a PV system to minimise export, or pre-emptively adjust system output to match anticipated changes in load.  A utility may offer a financial incentive to customers if they allow them to have some control over their system for demand management purposes. Perhaps the most likely and lucrative use of DRM in the future might be if the system owner chooses to participate in a group scheme run by a load aggregation company.  In this situation the customer would be paid by the load aggregator to provide them with access to some basic controls over their solar (or battery) system.  With load aggregators like Reposit Energy becoming more active in the market over the last year or so, it’s quite possible that this will become one of the most common uses of the DRM functionality.  So although system owners may not be specifically aware of the benefits of DRM capability at the moment, they may well want to take advantage of this feature in the future.

Is your inverter DRM ‘capable’ or DRM ‘compliant’?

In response to the new standards requirements, some inverter manufacturers have redesigned their inverters to incorporate full DRM functionality.  These inverters are referred to as DRM ‘compliant’, and within the AC Solar sector, Enphase Energy inverters are currently the only fully compliant microinverter available.  When you purchase Enphase microinverters and install them with the Envoy-S Metered+DRM communications gateway, the entire system is DRM compliant and ready to accept and respond to DRM signals.  Many string inverters, including the SMA Sunny Boy range, do not come standard with the DRM functionality. These inverters are referred to as DRM ‘capable’ but an additional module is required to be purchased and installed on the inverter, which could cost the system owner $1,000 or more should they want or need to implement the DRM capability in the future.  Unfortunately, many homeowners are not being made aware of this situation and may think they are getting a bargain, when in fact they could be facing significant additional costs in the future.

So installers should check to see if the inverters they are using are DRM ‘capable’ or DRM ‘compliant’, and always ensure the customer is fully informed of this when the system is sold.  The risk with selling DRM ‘capable’ inverters is that customers could potentially demand retailers or installers to return to install the DRM capability at their cost if/when they find out that the inverter doesn’t have this capability and they weren’t informed of this when the system was purchased.

If you supply and install a solar system that does not have Demand Response Mode (DRM) you are supplying a solar system that does not comply with Australian Standard AS4777.2:2015

More information about the DRM functionality of Enphase Microinverters can be found here.