When working with consumer devices that plug into a smart grid, there's no substitute for field testing, particularly of mobile, battery-operated devices. In addition, the use of home gateways can simplfy testing for utilities and give consumers more choice.
Those are two of the lessons we learned at the Sacramento Municipal Utility District (SMUD) in the last several years working on our SmartSacramento smart grid program.
Fueled by a $127.5 million grant from the Department of Energy (DoE), we deployed 615,000 smart meters to our customers running on a two-way advanced metering infrastructure (AMI) network that connects those meters to Home Area Network (HAN) devices.
Between 2012 and 2013, we also deployed about 6,700 HAN devices. SMUD chose to deploy only ZigBee SEP 1.1 HAN devices to capitalize on their stronger security and the ability to upgrade to SEP 2.
In 2011, we recognized the need for a certification and testing program for the various HAN devices. At that time, many of the large California utilities had developed their own in-house testing labs. Given the pressure of our DoE deadlines, we took a hybrid approach, using both internal and external testing.
We selected the National Technical Systems to:
- Test new firmware of previously certified ZigBee SEP 1.1 devices
- Re-run AMI network compatibility tests
- Perform basic functionality tests
- Test 5% of the devices we purchased in bulk
In addition, the SMUD internal lab performs end-to-end functional testing over ZigBee on our AMI network and over broadband on our demand-response management system. We also perform customer experience tests.
We found the effect of environmental factors on different HAN devices varies widely. For example, we found programmable, communicating thermostats had high connectivity rates because they were hardwired and stationary. However, some in-home displays have low connectivity rates due to range issues and poor power management algorithms in firmware leading to weak signal strength.
Interestingly, electric vehicle supply equipment was found to have low connectivity rates due to environmental interference from metal garage doors, among other things. In some cases, detached garages caused range issues, too, even though the end devices were hardwired and stationary.
In the future, SMUD intends to test and support only one or two HAN gateways certified to work with our meters. This approach will provide customers additional choices among devices -- like digital thermostats, home energy displays, and electric vehicle chargers -- that interoperate with our gateway.
The HAN gateway/router will act as an additional security firewall behind the meter. The intent is for the gateway to be pre-certified, provided and supported by SMUD to any residential customer who enrolls in any smart grid program. The HAN gateway will also provide two communication paths to the connected HAN devices, a primary ZigBee path through the meter, and a backup broadband path for customers with Internet access.
The SMUD-certified gateway will allow our customers the flexibility to purchase any retail HAN device compatible with SEP 2 over ZigBee or broadband communications supported by the gateway. Our customers will not be limited to only those devices the utility tests and certifies.
Just as in the telecom model, customer device support issues will be directed back to the retailer or HAN device manufacturer. This limits the scope of utility testing and support to one device, the HAN gateway.
Overall, our smart meter network has become a catalyst for a closer two-way partnership between the utility and its customers who work together to improve energy efficiency and reduce peak demand.
— Don Jacobs was the overall technology adviser for the $127.5 million SmartSacramento program. He also led the Smart Grid Project Management Office responsible for 51 smart grid projects. He shared some of his experiences in a webinar on May 22, 2014.