How science can pull power out of thin air

Cosmic rays and other sources of electromagnetic radiation are all around us, but usually dissipate too quickly to be of any use. Now scientists at the American University of Sharjah have come one step closer to tapping that power's potential.

Dr Lutfi Albasha has developed a radio chip that can harvest energy out of empty space. Charles Crowell for The National

SHARJAH // We are all familiar with solar energy. From tiny bands on pocket calculators to rooftop panels used to heat your home to the industrial-scale solar power plants springing up across the UAE, the energy from the sun is increasingly being used as a source of alternative energy for our ever-more power-dependent lives.

But light isn't the only electromagnetic radiation out there. We are surrounded by innumerable sources of electromagnetism, ranging from cosmic rays to the heat from the Earth itself. All of them contain energy - and almost all of it dissipates to nothing. What if that energy could be harvested?

A Dh1.1 million project is hoping to do exactly that. Researchers at the American University of Sharjah are developing an antenna that can pick up radiation from space and convert it into electricity to power wireless sensors.

The device is part of a project, launched in 2011, that will allow the sensors to power themselves in otherwise hostile environments - areas with very high temperatures, high voltages and desert environments where it would otherwise be impossible to physically change batteries.

"This is called energy harvesting," said Dr Lutfi Albasha, an associate professor in electrical engineering at AUS. "It searches for vibrations in the tool or electromagnetic radiation from the air. Pressure and temperature changes are all wasted energy that we can recycle and reuse."

The team is developing a small multiband single antenna, about the size of a packet of cigarettes, that uses a technique called impedance-matching, which allows waves to smoothly reach the circuit from the antenna.

An analogy would be to think of someone standing on the first floor of a building who wants to get to the ground floor. If he jumps he will injure himself, but with a ladder he can climb down smoothly with minimum exertion. The antenna is the ladder for the waves.

It uses "high-K" materials, which are substrates that help to shrink the electromagnetic waves, to collect their energy. The circuit board has a sub-antenna for each targeted wavelength, to maximise the range that can be collected.

The wavelengths that are being harvested can be measured in centimetres and millimetres - far shorter than TV signals, for instance, but far longer than light, whose waves measure less than a thousandth of a millimetre. With a dedicated antenna, scientists can harvest energy from four or five useful sources.

"The sensor needs to be extremely small, and it needs to search the area for any frequency radiating there that we can take energy from."

Once the energy is captured, microelectronic circuits convert the waves into electric current, using threshold cancellation techniques.

These work by reducing the voltage needed to activate and operate electronic circuits. They work in a way that the coming waves do not need to be at a high level of energy to turn them on as they work with the smallest level of wave energy.

"This means we can make use of waves that are very weak and too faint to operate normal circuits," said Dr Albasha. "The novelty of these circuits is their great sensitivity in picking up very weak signals ,and it's much better efficiency."

Once the energy is harvested, it will be converted into electricity to power wireless sensors.

"Our focus is on developing ultra-low power, electronic harvesting circuits that can empower wireless sensor networks so that these sensor networks can stay there for as long as their life guarantees without the need of intervention from people or operators.

The sensors have many possible uses - to measure the temperature over a long period of time near the mouth of a volcano, or to pick up the vibrations caused by cars passing over a bridge to investigate fatigue in the structure.

"It's like a drop-and-forget electronic circuit," said Dr Albasha. "We come close to them every now and then and collect the data."

So far, the team has developed a simulation of antenna. They still need to complete a microchip's design and send it for fabrication by the microchip maker Globalfoundries.

The ultimate aim will also be to improve the efficiency of the harvesting system.

"For that, we need to have the best antenna. They're like windows to allow power to come into a system," said Dr Nasser Qaddoumi, a professor in electrical engineering at AUS. "You need a small antenna but it should act as a big one."

So far, they are only able to use five to 10 per cent of the energy that is theoretically available. "The rest is lost," said Dr Albasha. "One of our objectives is 30 per cent efficiency.

"Energy harvesting is becoming the buzz word in electronic research. It's the new big thing."

The project is expected to wrap up in October next year.