Ambient temperature changes, which take place natively in the environment, could power Internet of Things (IoT) sensors indefinitely, say researchers.
The remarkable concept, which the inventors at theMassachusetts Institute of Technology(MIT) call thermal resonating, is highly flexible — unlike previous scientific attempts at developing similar things.
It essentially harvests electricity out of thin air, the group claims. No batteries or solar panel-requiring sunlight is needed.
Around 1.3 milliwatts of power have been created in experiments, writes David L. Chandler in an MIT News article about the discovery. That micro-level power supply could be enough to run some communications gear, too, the researchers say.
“These [temperature fluctuation frequencies] are an untapped source of energy,” Michael Strano says in the article. He is an MIT professor and has been involved in the invention. “It’s something that can sit on a desk and generate energy out of what seems like nothing.”
Getting power from night-and-day temperature fluctuations
The group created the experimental power supply from an 18-degree Fahrenheit temperature change, mimicking the night-and-day changes found many places in the world.
Importantly, it’s the real-world tunability, such as that which could be harnessed by consistent diurnal (night-and-day) temperature changes, that could make this project have legs for IoT.
Basic thermoelectic devices, which generate power when one side of a conductor is a different temperature than a joined other side, have been around for a while. It’s called the Seebeck effect and was invented in 1787. The concept works through hot and cold sides of coupled, but dissimilar, metals trying to get to equilibrium.
In 2014, I wrote about how waste heat from data centers could be converted to electricity using the Seebeck effect and explained some of the limitations in the tech overall: it’s hard to keep the hot bit hot and cold bit cold, being one.
However, this MIT system wouldn’t need heat or cooling sources — it just harnesses ambient air over time. Thus, theoretically, one could implement it and forget it.
“The new system is the first that can be tuned to respond to specific periods of temperature variations, such as the diurnal cycle,” the MIT researchers say. “It could enable continuous, years-long operation of remote sensing systems.”
The group achieve their efficiencies over the traditional Seebeck effect and another concept called pyroelectricity, through the use of cutting-edge materials, including taking advantage of graphene for quick conduction.
Energy for IoT
Energy harvesting development will become increasingly exciting as the IoT takes hold. Just how does one power these potentially billions of devices — many of which will be off-grid in remote and/or in hard-to-access spots? Last month, I wrote about a form of ultrasonic signaling that could wake up sensors as they were needed. That saves traditional power and may be one option.
Solar photovoltaic is another power choice, but as with wind power, the panels require certain environmental thresholds to work. The slabs won’t work at night, obviously. With wind power, turbines don’t function when the wind slacks off.
Simple, diurnal temperature variations that always occur may turn out to be a more consistent power source.
“It is unaffected by short-term changes in cloud cover, wind conditions, or other environmental conditions, and [it] can be located anywhere,” the scientists say.