Weighing the ZigBee Broadband Gateway Solution for Demand Response

Weighing the ZigBee Broadband Gateway Solution for Demand Response

In a recent article, I discussed the strengths and weaknesses of a ZigBee-based advanced metering infrastructure (AMI) system for demand response (DR). In the second installment of this series, I will be exploring an alternative communication option for DR that offers more benefits and fewer disadvantages: a ZigBee broadband gateway.

As AMI systems started to be deployed and the ZigBee standard completed its development in 2009, some utilities have looked for two-way DR system alternatives that are outside of AMI. There are several possible reasons for this need:

1. An AMI deployment for the utility is not planned
2. The AMI business case is not cost-effective
3. Recent capital investments into an automatic meter reading (AMR) system have not fully depreciated and cannot be replaced with an AMI system
4. DR solutions that offer more functionality with a richer customer experience than what is available from an AMI system are desired

One alternative that became popular with utilities is to use a broadband gateway. Simply stated, a gateway is a device that connects two networks. Similar to the AMI system, a broadband gateway uses the customer's broadband network as the communication backbone and it creates a ZigBee home area network (HAN) inside the customer's premise for device control. Like any network architectures, the broadband gateway solution works well in some circumstances and is less ideal in others, as I'll discuss below.

Case Studies

One Comverge customer wanted their demand response program to drive customer engagement and provide greater "customer stickiness" in a competitive retail environment. They needed to offer the capability for customers to interact with their thermostats remotely to save on their energy bills by conveniently changing thermostat settings.

These preferences pointed to the need to run the program through a high-speed, low latency connection such as broadband. As I discussed last month, the ZigBee Smart Energy Profile (SEP) has limitations when it comes to functionality, such as remote thermostat programming, that supports a customer engagement program. For this client, we resolved that issue by supplementing the SEP protocol with a manufacturer-specific profile (MSP) protocol that allowed us to put in our own commands and functions to enable the level of customer engagement that was sought.

Another Comverge client had already deployed an AMI system needed to read interval meter data, but needed a DR system that automated the response to the varying price tiers. With the broadband solution, customers can program their thermostat, water heater and pool pump behavior to the varying price tiers over the Internet, making it easier to use and program. Price tier and critical-peak pricing (CPP) signals are sent over the broadband network to initiate the DR device responses. Tier usage can be determined at the backend, matching the tier intervals with the interval data from the AMI meter.

A third utility customer runs a similar varying price tier program, but with one major difference: it does not have an AMI system deployed. To address this, Comverge enhanced the broadband gateway solution to not only perform the DR command and control, but also to bring interval meter data back by joining the gateway to a standalone AMI meter. The standalone AMI meter registers and stores all of the energy consumption internally. The broadband gateway then acts as an in-home display (IHD) client, reading the meter data on a regular basis and uploading that data back to Comverge's IntelliSOURCE demand response management system, in which billing determinants are created and fed to the billing system.

Utilities we work with that have deployed two-way DR programs using broadband networks with a ZigBee gateway solution find that it meets most of their needs. For the main objective of creating a two-way DR network, a broadband gateway offers plenty of advantages, including high bandwidth, low latency, no recurring monthly cost to the utility and the potential for rich customer experience and engagement. On the negative side, it costs approximately $100 more per customer, is based upon a customer-controlled network in which some percentage of devices are always disconnected, and has inherent complexities that make it less manageable than other options that I will discuss in my next blog post.

Our customers have demonstrated that a broadband gateway solution can work well for two-way demand response. For any utility on the path of finding a communications network to deploy DR, it is simply a matter of understanding the limitations in each system and your own priorities with the program.

Source: Energy Central

SMART GRID Bulletin April 2017


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