Asleep Yet Aware Technology and Energy Harvesting Improves Sensor Efficiency

More and more manufacturers are putting sensors in parts and products to collect and transmit data. That data can be used to improve equipment performance, run self-diagnostics, automate service calls, improve safety, and track and manage inventory. However, all these sensors need electricity to run.

Electricity is not a problem when a power source is readily available. Deploying those parts and products is less practical in remote locations or where the equipment is embedded within an infrastructure. Locations where you cannot just plug your machinery into a wall and call it a day.

In order to continue to collect and transmit data, you must provide an independent power source such as a battery or super capacitor. While batteries seem to be the obvious solution, they have problems of their own. Batteries only last so long, and even rechargeable batteries have a limited life.

Sending someone to service and swap out batteries in remote locations can be extraordinarily costly. Imagine someone making the trip to swap out the batteries on the Mars Rover once they degrade and can no longer re-charge.

For some, servicing equipment is not so much costly as it is deadly. The military uses sensors to detect vibration, light, and sound to monitor the environment, perimeters, and infrastructure. Those sensors are always active which means they constantly consume power giving them a useful life of just a few weeks or months. Every time someone has to redeploy a power depleted sensor they are exposed to danger.

That is why Defense Advanced Research Projects Agency (DARPA) launched the Near Zero Power RF and Sensor Operations (N-ZERO) program. Organizations and academic institutions have been challenged by DARPA to develop wireless, event-driven sensing capabilities that would allow physical, electromagnetic and other sensors to remain dormant—effectively asleep yet aware—until an event of interest awakens them.

The goal is to create sensors that use less than ten nanowatts during the sensor’s asleep-yet-aware phase. Ten nannowatts is about equivalent to a watch battery’s discharge during storage, and 1000 times lower than sensors available today.

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“By advancing state-of-the-art sensing capabilities for national security through N-ZERO, DARPA could help make the Internet of Things more efficient and effective across countless scenarios and environments, thus transforming the way people live,” said Troy Olsson, DARPA program manager.

While we are waiting for DARPA to break the asleep-yet-aware code, we have another option, which is energy harvesting. That is, to use ambient energy to create electricity. Most notably solar energy, but also thermoelectric and piezoelectric generators.

We are seeing some of this energy harvesting being deployed commercially, but it is not widespread. Jeff Sather, VP of technology and customer solutions at Symbet, says that part of the reason for this is the upfront engineering work has to occur during the design phase which makes it harder to get products to market quickly.

Designers and engineers have to think about the environment in which the customer will deploy the transducers. Not all environments are the same so either you have to design for the worst-case scenario, which leads to over-spec’ing many of the components, or you get into the custom product business, which is hardly sustainable.

While we are waiting for DARPA to break the asleep-yet-aware code, we have another option, which is energy harvesting. That is, to use ambient energy to create electricity. Most notably solar energy, but also thermoelectric and piezoelectric generators.

“That’s going to be a real obstacle to mass deployment of energy harvesting based sensor nodes if every application is different enough that there has to be customization on the manufacturing or customer side,” said Sather.

All of this means higher upfront costs, which results in manufacturers backing off of energy harvesting and simply adding a bigger battery. However, you need to compare those upfront costs with the cost of sending people out to service equipment in a remote location. When you add those costs up the initial investment does not seem too bad.

Between DARPA’s N-ZERO project, the trend of batteries getting smaller in size yet lasting longer, and sensors using less power, manufacturers will be able to add sensors to more and more parts and products regardless of the environment in which they will operate.

These smart parts will be able to gather and transmit data for three to five years instead of months. Add energy harvesting to the components and now you can deploy equipment to even the most rugged environment and not worry about making a service trip for ten or fifteen years.

Traci Browne is a freelance writer specializing in manufacturing, engineering and science. You can find out more about her at www.TraciBrowne.com.

The work was originally commissioned by Aptera Inc.

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