Batteries may be the go-to power for IoT devices today, but energy-harvesting options are emerging and destined to play a big role in creating ultra-low power systems.
IoT deployments require the use of smart, miniaturized silicon-chip sensors that transmit data on a regular basis. Powering these oftentimes set-it-and-forget-it devices, sometimes installed in hard-to-reach or dangerous locations, is no easy feat.
Until now, batteries have been primarily viewed as a starting point for powering IoT. However, energy-harvesting technologies, which derive power from external sources such as solar, thermal, wind and vibration, have set their sights on IoT. In fact, many new IoT systems now combine batteries with energy-harvesting capabilities to take advantage of ambient energy while having the assurance of a battery backup.
So, what’s the best way to power an IoT system — energy-harvesting technology or batteries or both? As with any decision, it depends.
“The powering of IoT devices varies widely by industry,” said Christian Renaud, analyst at 451 Research. “What works for factory equipment is different than for a semi-truck or agricultural sensor. It varies by industry and even sub-use case.”
Energy harvesting emerges as a real-world IoT power option
So far, energy harvesting hasn’t really taken off, despite its enormous potential to power IoT. There are plenty of IoT use cases in which batteries are a great choice, especially if they involve only a handful of sensors. But smart cities or large industrial installations with thousands of sensors with batteries that need to be changed often — even every few years — open the door to a risk of losing data.
Christian Renaud, analyst, 451 ResearchChristian Renaud
“In smart buildings, where there may be retrofit or brownfield applications, we’re seeing energy-harvesting use cases for occupancy sensors for lighting, heating, ventilation and air conditioning to lower energy costs for the building,” Renaud said.
Energy-harvesting technologies have come a long way in the past 10 years. Early installations for building energy management systems — for example, turning lights off and rerouting airflow from areas no one is using — were efficient and saved money, but really only made sense for buildings in excess of 55,000 square feet.
“The installation costs early on were unreasonable for many players, so we decided to reduce the installation part and simplify it, which opens up a larger section of that market,” said Christian Pennisi, director of operations at Jennova, a provider of energy-harvesting technologies.
Energy harvesting offers the reliability of hardwiring, but with the versatility of simplified installation you get from a battery. “We recommend an integrated backup battery with the energy harvester so that you’re able to keep that battery above 70% capacity, and it can provide power if needed,” Pennisi said. “We view it as a fusion between energy harvesting and battery storage — instead of being one or the other.”
Jennova offers a power management circuit designed to work with any energy-harvesting transducer. “You have your transducer, which depends on how you want to harvest energy — piezoelectric, thermoelectric, turboelectric, vibration, photovoltaic or whatever it might be — and this one circuit board takes the input and converts it into usable power, amplifies the voltage and makes sure you’re getting good DC out,” Pennisi explained. “It also has an integrated battery management chip that’s intelligent enough to help keep the battery recharged to power the device directly when enough energy harvesting isn’t available.”
While Jennova is currently still doing R&D into other types of energy harvesting, the company’s moving toward what it expects to be the “big three” energy-harvesting platforms: photovoltaic, ambient wireless energy and vibration. “These will probably be the winners, because we can get the costs down to a point that the market will bear,” Pennisi said, adding that “they’ll also be the least intrusive installations.”
Enterprises are finally seeing the value of energy harvesting, so they’re starting to take action. “Instead of being hype, people are understanding the benefits and asking if there’s a solution that might work for them,” Pennisi said. “Companies are more likely to engage in finding those solutions now.”
Don’t count batteries out just yet
While energy-harvesting is making inroads in IoT, many companies are taking the IoT power challenge into their own hands, lowering the power consumption of their devices to alleviate demands placed on batteries. Key areas of design affecting power consumption are connectivity and range.
For example, the more remote the deployment, the longer the battery life needs to be to remove the requirement for frequent replacements. Every truck roll means lost margins and a longer ROI curve, according to Renaud. “This is helping drive interest in low-power wide area networking, such as LoRa and [Narrowband-IoT], because traditional cellular connections would blow through even larger batteries within days or weeks,” he explained.
In short, connectivity drives power requirements.