25-March-2020 By Jeffrey Cooper

Energy Advances for IoT

I’m a big proponent of IoT solutions, but they does post a lot of challenges for some types of installations. I do think big when developing a solution or concept, but also try to then reasonably scale back to what is achievable today, with a plan to build out functionality as it becomes practical. I give such an example in the Immersive Spaces article on this website.

For reasons described here, I like to keep up on new advances in energy systems, both batteries and generation. In small deployments on a smaller scale, such as beacons and a few sensors, today’s batteries will suffice and yearly replacement is not a big hassle. For deployments with hundreds of sensors, it begins to get problematic, even in an easily-accessible location such as a gym or big box retail.

If you’re outfitting civic structures with sensors, it becomes a much bigger problem. There are a couple of solutions. Once is to wire them together so they get permanent power from an external source. Another solution in some deployments, is energy harvesting.

Energy Harvesting

Energy Harvesting has a lot of potential, but today, other than solar or a small wind turbine, there aren’t many other options. It is possible to extract energy from thermal differences, motion (think self-winding watch), sound and even humidity, but these are going to return scant amounts of power and aren’t useful at this point.

We all are familiar with solar cells, which work well in sunlight and can work indoors for low power uses. For indoor use, whether they can power an IoT mote’s radio would depend on which radio technology is uses (newer standards are lower power) and the frequency at which the data is transmitted.

Enerbee, a French company, has another approach. I met them years ago at a Qualcomm conference. I was hopeful for them, and checked back recently and see they have focused on airflow-generated power. It’s a highly efficient, piezo-magnetic turbine that generates power at low speeds, enough to power a sensor and radio for intermittent (infrequent) data bursts.

For many applications, you don’t need data to be sent continuously. Frequently, seconds or minutes (or longer) is sufficient.

In the diagram above, I show a meshed outline of the Golden Gate Bridge, which could be outfitted with sensors. The sensors either need to be wired and powered by solar cells (with enough power stored for overnight transmission), or wind powered. I live in the Bay Area, and I can attest to the fact that most of the time, it is windy around that bridge.

With thousands of sensors deployed across a large structure, you also don’t want to rely on the mesh alone to deliver the messages to the edges. Placement of hubs that communicate with clusters of sensors, which have a source of continuous power would be best in these circumstances. Deployed as such, a mesh could continuously monitor a large structure like a bridge, providing real-time data on stresses from wind, earthquakes, traffic and the effects of aging, as parts deteriorate and need to be replaced.

Batteries

Batteries themselves need to get better. Scientists have pushed lithium ion batteries close to their limits. They can pose dangers, as occasionally seen in a few mobile phones and cheaper, imported variants of popular products. They only take recharging for a limited number of cycles.

A recent article in the Wall Street Journal discussed a new, solid state lithium battery that replaces the graphic anode with metallic lithium. You get an immediate 60% increase in capacity for the same size cells. These are now being manufactured by Murata Manufacturing and TDK for small uses, which would result in a longer life for low power, low frequency IoT sensor motes and beacons. Longer term, they will be developed and get better. For now, they are more expensive, but as production of lithium metals scales up, costs will come down. And they are much safer than today’s fire-prone lithium ion batteries. Note: The WSJ link requires a subscription to read the entire article.

We will always be in a race for more power and less energy. It’s the nature of the progress of technology. But each new level of form and function that gets deployed means ever more complex and useful systems can be built, whether it be for a gym, retail store, or a bridge. These in turn will improve safety and efficiency, and improve the human experience in an immersive, responsive world.