What about AMI battery life?
Water utilities throughout the United States are evaluating advanced metering infrastructure (AMI) as a way to improve meter read accuracy and reduce operational costs. In virtually every planning meeting, the topic of AMI battery life bubbles up. AMI devices are battery powered, and once the battery fails, the device must be replaced. Premature battery failure results in unrealized savings and increased costs.
For the most part, vendors’ story on battery life hasn’t changed in the last decade: vendors will provide a twenty-year warranty to cover full replacement for battery failures in the first ten years, and a prorated/declining replacement for failures over the remaining ten years. Along with this warranty comes a number of caveats, including the schedule for transmitting meter reads, the frequency of on-demand reads, and the number of firmware upgrades over the meter’s life. Some vendors will negotiate better or longer battery warranties, but these arrangements will usually be priced at a premium.
Significant changes to battery technology are unlikely in the near-term, but emerging technologies could improve AMI battery life in the next decade – and hopefully increase vendors’ AMI battery warranties.
Energy harvesting (EH) takes energy from external sources, then stores it within a wireless device. Electric fields resulting from the flow of water through a water meter could enable AMI devices to be powered by EH, assuming the EH device receives a specified minimum current.
Piezoelectric technology could enable an EH-powered water meter. Piezoelectric devices are easy to make – essentially sandwiching dissimilar metal surfaces together. Mechanical stress on the surface of the piezoelectric device creates a small electrical charge which can then be harvested.
We have seen rapid advancement and application in piezoelectric technology via wearable devices like Fitbits and Apple Watches. By weaving piezoelectric threads into wearable items, you get the dual benefit of (1) producing an electric charge that can be harvested, while at the same time (2) having those charges reflect the area and amount of movement exhibited by the user.
Harnessing piezoelectric EH technology in a water meter hasn’t happened yet – but it is possible, and something we hope to see in the future from AMI vendors. This concept is not without challenge. For example, if water consumption is low (or zero), will the meter stop communicating, since there is no flow to charge the piezoelectric device? Because of challenges like this, EH is more likely to augment a battery in the early years, rather than fully replace it.
Battery life will make or break an AMI business case – either enabling the utility to see a return on their investment over 15–20 years, or resulting in unrealized savings/increased costs based on premature failure. Emerging technology like EH AMI devices could help vendors increase the length of battery warranties, and increase water utilities’ confidence that AMI devices will reach their anticipated useful life — enabling the utility to fully realize savings.
As your utility evaluates AMI, what useful life are you planning for, and how are you protecting yourself via appropriate AMI battery warranties given the current technology limitations?