The IoT’s Power Struggle
From a power standpoint, IoT implementations would be relatively straightforward if you could just plug them into an electrical line. The problem is that many IoT devices have a pesky tendency to reside in remote areas with no direct access to the power grid.
Just think of how diverse the IoT ecosystem is, comprising everything from household light bulbs and door locks to sensors on electronic highway signs, oil rigs, aircraft, and missiles. Power management for household devices is easy enough, as you can plug them in or regularly replace their batteries. But things get more complicated with sensors in remote areas monitoring oil pipelines, farming equipment, water source levels, animals in the wild, or cargo on freighters.
Integrators, therefore, must keep power management in mind whenever planning an IoT deployment, says Michael Lamp, director of IoT business development, Americas, for technology solutions distributor Avnet. Too often, IoT implementers try to leverage the same solution for every environment, he notes. “When we’re talking about power and performance, that doesn’t always work.”
In roughly half of IoT implementations, Lamp says, it’s possible to leverage an available power supply, such as an electrical connection or vehicle alternator. But in many instances, those power sources aren’t easily accessible.
Batteries, meanwhile, have obvious limitations, especially if they drain quickly like the ones in cellphones. It’s estimated that 55 percent of the IoT will be wireless, but if all wireless implementations used only cellular communications, they would get expensive fast and require frequent battery recharging. For many applications, cellular isn’t cost-effective or practical because of power requirements.
For certain uses, the answer is to leverage a low-power wide-area network (LPWAN) such as LoRaWAN or Sigfox. If IoT sensors and trackers need only send a small message once or twice a day, for example, you can keep them in the field for years before replacing the battery. These devices are in sleep mode most of the time, waking up only when they need to transmit data.
“Devices on the Sigfox LPWAN enter and exit sleep mode at will and do not expend any energy communicating with the network during the sleep-wake transition. Depending on the number of messages sent per day, battery life can be predicted and last upward of 10 years,” says Kristi Mason, communications director at Sigfox USA.
Device makers are experimenting with green alternatives for power too. Some devices can switch to a second source such as solar when batteries get low, says Lamp. But at this point, he adds, eliminating batteries altogether isn’t feasible.
Manufacturers are also exploring energy-harvesting techniques, according to Joe Miller, lead hardware engineer at hardware maker PNI Sensor. “Examples of energy-harvesting power sources include light (either sunlight or room light), electromagnetic waves, and mechanical movement such as a moving limb, impact and stride from walking, or even a bicycle wheel,” he says. (See “Vendor to Watch: PsiKick” for a description of energy harvesting via temperature difference).
Such options only work for specialty applications and applications with small payloads or bandwidth, though, Miller says. “These applications have the prerequisite that the primary power source be at-hand at regular intervals or when the device is active.”
When evaluating power options for IoT implementations, integrators need to consider factors such as power consumption, battery life, device size, range of radio transmission, and cost. Avnet’s Lamp encourages integrators to get planning help from his company; Miller says component manufacturers can assist as well. “Battery manufacturers provide leakage and predicted capacities under user-defined loads and temperatures,” he notes.
Power management will remain a challenge as the IoT widens its reach. There is no ready-made, single solution, but with thought, planning, and consultation, integrators can work to minimize the impact of the IoT’s power struggle.
Pedro Pereira is a Massachusetts-based writer who has covered technology and the IT channel for two decades. He can be reached at firstname.lastname@example.org.