Energy disruption: Chips that snatch power from multiple sources

Researchers at MIT have developed chip sets that draw power from heat, light and vibrations.

Researchers at MIT have developed chip sets that draw power from heat, light and vibrations.

Computer and wireless-communication chips that can operate at very low power levels have been the focus of work from the lab of MIT professor Anantha Chandrakasan. The latest development from the lab, carried out in collaboration with doctoral student Saurav Bandyopadhyay, is a new kind of chip that may be able to harness energy from heat, light and vibrations -- optimizing power delivery for devices that are not powered by standard battery systems.

The energy-combining circuit is described in a paper to be published this summer in the IEEE Journal of Solid-State Circuits.

"Energy harvesting is becoming a reality. The key here is the circuit that efficiently combines many sources of energy into one." says Chandrakasan, the Keithley Professor of Electrical Engineering and head of MIT's Department of Electrical Engineering and Computer Science.

The first stage in developing very low-power chips that can collect and relay data remotely is securing sustainable power sources to facilitate such use. The new design pulls together multiple power sources into a single device -- a huge advantage as sustainable energy can often be unpredictable or intermittent.

Energy sources for these chips can come from a variety of sources. Many of which, we may assume to be inconsequential. Ever think the vibrations caused by someone walking across a bridge? This, in itself, can generate energy -- it isn't just about the more well-known sources like solar power.

Instead of the usual method of switching among sources where most energy is being generated at a given time, the chips have been designed to draw power from every source continually. Typically, each of these chips comes inbuilt with a sophisticated control system, which has to be tailored towards specific requirements.

Circuits that focus on harvesting thermal energy typically produce 0.02 to 0.15 volts, photovoltaic cells generate between 0.2 and 0.7 volts, and vibration systems can produce up to 5 volts. Coordinating these separate circuits have proven to be one of the trickiest processes in developing the chips, especially if they are to be useful in real-time scenarios.

David Freeman, chief technologist for power-supply solutions at Texas Instruments, commented on the development, saying:

"The work being done at MIT is very important to enabling energy harvesting in various environments. The ability to extract energy from multiple different sources helps maximize the power for more functionality from systems like wireless sensor nodes."

Only in recent times have companies developed low-power microcontrollers and wireless transceivers that could be powered by sources like multiple circuit boards. These kinds of chips could ultimately be used in biomedical devices, environmental sensors and gauges in areas that are difficult to continually access.

"With innovations like these that combine multiple sources of energy, these systems can now start to increase functionality," Freeman says. "The benefits from operating from multiple sources not only include maximizing peak energy, but also help when only one source of energy may be available."

The work has been funded by the Interconnect Focus Centre, a combined program of DARPA and companies in the defence and semiconductor industries.

(Source: MIT)

Image credit: Stefano Mortellaro

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