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The future of energy
A bridge sways. A raindrop falls. Your body stays warm despite cooler temperatures outside. These constant, fluttering changes in our environment produce tiny amounts of energy.
Amazingly, this energy can now be harnessed as power. Texas Instruments (TI) is working with customers to develop devices that harness energy from moving buildings and changes in body temperature. The devices could power a number of applications, including sensors or temperature control gadgets.
"There are serious sources of power around us," said Martin Izzard, vice president and manager of TI's Digital Signal Processing Solution Research and Development, in a 2008 webcast.
"We're on the verge, a test-chip stage, of building things that are extremely low power," he continued. "Low enough power to practically run off of scavenged power, things that might take energy out of your body heat."
It's also known as energy harvesting.
What is energy harvesting?
Energy harvesting is a way to capture, store and use miniscule amounts of energy from naturally occurring sources.
The concept is not new. Small outdoor pathway lighting systems use solar panels, and emergency roadside telephones are powered by the sun. But as the ability to harvest this ambient energy gets better, and as microprocessors use less energy, applications are growing exponentially.
"We are reaching what we would call an inflection point," Izzard said. "We are able to make practical, useful systems down at the milliwatt or lower range. At that range, it becomes possible to actually look around us and harvest some energy out of the environment."
Energy harvesting requires technology development on a number of fronts. First, engineers must figure out how to pull the energy from the environment, be it from the sun, the wind, vibrations from a bridge or the impact of a human foot hitting the ground.
Next, they must develop highly efficient chips that use these miniscule amounts of energy to operate. They might also employ low-power wireless radio frequency devices to transmit the data that the chips gather.
Sensors
Energy harvesting has been used in products such as TI-enabled wireless light switches and temperature controls. The wireless approach may have the additional benefit of improved safety.
The next wave of industry interest is in the development of battery-free, electrical cord-free sensors. Networks of these tiny sensors, using very small amounts of power, could be spread over wide areas such as forests or water utility pipes.
The sensors would then use wireless technology to communicate, providing valuable information. "You would be able to glue sensors all over a bridge, for instance," Izzard said. "People are driving across this bridge, and the bridge is vibrating all the time.
"The sensors absorb energy from the vibration of the bridge and over time can give you data on things like corrosion and how much vibration load the bridge has been through."
This vision, known as "smart" infrastructure, is intended to help assure that buildings and bridges are safe to use. It is also efficient, electronically obtaining data that's currently gathered by researchers in the field. And it will save money by alerting engineers to make needed repairs to bridges and roads before serious problems occur.
New sources of energy
Engineers can already harvest energy from vibrating bridges. So researchers at TI's Kilby Labs are now looking into more unconventional sources.
For example, your skin is usually hotter than room temperature. The difference between the two temperatures is a source of energy.
TI researchers are investigating a harvester that feeds off body heat to power simple circuits that could be used in health care applications, such as a hearing aid.
"Parts of this research already been done," said Ajith Amerasekera, director of the Dallas-based Kilby Labs, a TI research hub.
But Kilby Labs researchers still need to solve challenges associated with the devices' size, composition and vibrational frequency, he said.
The need for low power
No matter what the source, harvested energy provides just a tiny amount of power. Therefore, the chips that use this power must be very small and ultraefficient.
So aside from looking to new energy sources, TI is pioneering breakthroughs in ultra-low-power microprocessors.
In 2008, researchers at the Massachusetts Institute of Technology and TI unveiled a chip that uses one-tenth the energy of TI's widely used MSP430 microcontroller.
Although it's probably five years from reaching the market, the ultra-low-power chip has tremendous potential, including use in cell phones. A more energy-efficient chip means that cell phone users can add applications such as Internet surfing and video watching without rapid battery drain. Low-power chips can also more effectively power implantable medical devices.
Ultra-low-power processors are another step toward developing chips that can live on ambient energy alone.
"When you look at the next 10 years, a lot of electronics will need to be autonomous," Amerasekera said. "They will need to be supported without wires or operate for long periods with just one battery charge."
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