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MIT Develops Solar-Powered Sensor To Keep IoT Data Flowing

Tom Jowitt is a leading British tech freelance and long standing contributor to TechWeek Europe

Researchers invent solar-powered sensors to harness Internet of Things potential

The Internet of Things will increasingly rely on sensors to gather all types of data, but one of the drawbacks is to with powering those sensors, which could run for months at a time between charges.

Now MIT researchers in America believe they have the answer, with sensors that are designed to extract energy from the environment in order to charge.

Solar-Powered Sensors

Sun solar power sunspot energy © solarseven ShutterstockThe researchers have effectively invented a new power converter chip designed for extremely low-power sensors. The prototype chip was made by the Taiwan Semiconductor Manufacturing Company’s University Shuttle Program.

In the past, ultralow-power converters had efficiencies of only 40 or 50 percent, but the MIT researchers have revealed a new power converter chip that can harvest more than 80 percent of the energy trickling into it, even at the extremely low power levels characteristic of tiny solar cells.

This is an interesting development, as not only can the new power converter chip achieve 80 percent efficiency – but the MIT boffins have included some additional capabilities. The new power converter chip can use the tiny solar energy to both charge a battery, as well as power the device directly from the battery.

All of this is achieved because the new power converter chip boasts a single inductor – its main electrical component – that does both operations. This not only saves on circuit board space but increases the circuit complexity even further. Despite that, the chip’s power consumption remains low.

“We still want to have battery-charging capability, and we still want to provide a regulated output voltage,” said Dina Reda El-Damak, an MIT graduate student in electrical engineering and computer science and first author on the new paper.

“We need to regulate the input to extract the maximum power, and we really want to do all these tasks with inductor sharing and see which operational mode is the best,” she added. “And we want to do it without compromising the performance, at very limited input power levels – 10 nanowatts to 1 microwatt – for the Internet of things.”

According to the MIT researchers, the main job of a circuit is to regulate the voltages between the solar cell, the battery, and the device the cell is powering. If the battery operates for too long at a voltage that’s either too high or too low, for instance, its chemical reactants break down, and it loses the ability to hold a charge.

The single inductor in the new power converter chip is the main development that the MIT researchers have developed. In order to control the current flow across their chip, El-Damak and her advisor, Anantha Chandrakasan, used an inductor, which is a wire wound into a coil. When a current passes through an inductor, it generates a magnetic field, which in turn resists any change in the current.

“One of the things that’s most notable about it is that it’s really a fairly complete system,” said Brett Miwa, who leads a power conversion development project at the chip maker Maxim Integrated. “It’s really kind of a full system-on-a chip for power management. And that makes it a little more complicated, a little bit larger, and a little bit more comprehensive than some of the other designs that might be reported in the literature. So for her to still achieve these high-performance specs in a much more sophisticated system is also noteworthy.”

IoT Developments

The Internet of Things is attracting a lot of interest from the technology players of late, as well as academic research.

Indeed, earlier this year, Anantha Chandrakasan, professor of electrical engineering at MIT, solved an IoT problem in that if a sensor is waiting to be polled so it can answer with a snippet of data, the radio has to be in a state where it can be woken up. However, when the device is off, you want the least possible leakage currents. She came up came up with a new transmitter design that reduces power leakage by 100-fold.

And last month, Samsung looked to blow open the IoT space with a complete and open hardware platform aimed at making it easier than ever before to build connected devices.

Earlier this year, IBM announced a major expansion of its Internet of Things (IoT) business. It pledged $3 billion (£2bn) over the next four years in building up a new IoT unit that is able to deal with the increasingly huge amounts of data being produced every day.

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