Technology is moving more mobile. The power supply is becoming a problem for electric vehicles, autonomous robots, wearables, and portable electronic devices. Because of the battery’s limited capacity and weight, as well as their long and slow charging times, mobility and flexibility are severely restricted. This could be solved by wireless power transmission or, more consistently, power generation in the mobile device.
Transferring energy through space has been around for a while. This process has been used by the sun for over 4.5 billion years. The losses are enormous. Most solar energy is lost to space; only a tiny fraction reaches celestial bodies orbiting around it. Only a fraction can be harnessed. This is true for wireless energy transmissions over distances more significant than a few millimeters. Their efficiency, which measures the ratio of usable energy and total energy expenditure, drops rapidly with distance.
Bundling electromagnetic energy is one solution. Emrod is a New Zealand-based cleantech company that uses a beamforming method to convert electricity into an electromagnetic beam. This beamforming technique sends the beam from one antenna directly. Emrod demonstrated proof-of-concept wireless power transmission at a beamforming efficiency greater than 97% one year after its foundation. Greg Kushnir, CEO and founder of Emrod, explains the critical innovation. “We achieve high efficiency using electromagnetic metamaterials. They can be used to bundle electromagnetic energy in the transmitting radio antenna. We can achieve an efficiency of more than 80 percent by improving the transmitting and receiving sides, which are the most vulnerable. Depending on where you are located, and the losses that may be incurred due to power theft, power transmission over high-voltage lines has an efficiency of 60-95 percent. Metamaterials such as those made of composites of metal or plastic have “unnatural” optical and electrical properties. If the structures are not smaller than the wavelength, they can interact with electromagnetic waves unexpectedly. Metamaterial, for example, can direct radar beams around it in a way that is invisible to radar.
Field tests are currently being conducted
Kushnir says: “The metamaterials we design and construct are distinguished by their smart property such as their precise shape, geometry and size, orientation, and arrangement which allow us to block, reduce, amplify, redirect or amplify electromagnetic energy.” Emrod Wireless power transmission uses frequency 5.8 gigahertz. This frequency is used for wireless power transmission and is independent of weather conditions. The beamforming technology was developed by Emrod The energy is transmitted via relay antennas from the transmitting antenna to the receiving antenna as a tightly bundled “rod”. This technology is also used to name the company: Em stands for electromagnetic and rod for rod. With the New Zealand power supply Powerco , Emrod A larger indoor prototype has been developed and a wireless system is being planned to be built to allow for further expansion. Powerco’s Supply network. The system is expected to provide power to remote areas and reduce the need to install copper cables in difficult terrain. The wireless system will also reduce maintenance costs and impact on the environment. Kushnir says that wireless power transmission is a key technology to transport energy to consumers in a sustainable manner, especially for renewable electricity generation. Transport by cable is difficult because of the large number of substations and transmission towers. It also requires many materials, such as copper, and significant maintenance and repair.
Where conventional wired connections are too expensive, complicated to install or maintain, permanent Emrod units may be used.
Photo illustration of an antenna truck that can be used for power supply in disaster zones.
Transmitting energy wirelessly over short distances is already part and parcel of everyday life. To keep losses low, wireless energy transport over long distances is a complex task. This is why Emrod’s highly-specialized antenna design is so important. Low-loss energy transport through air is possible if the receiver and transmitter are just a few centimetres apart. This is the state of the art. The transmitter and receiver are simply two coils that face each other at a short distance.
Inductive coupling is a well-established principle
An alternating current can be sent through the transmitter coil to induce an alternating voltage in its receiver coil. This principle of inductive coupling is already used by wireless charging stations for smartphones and electric toothbrushes. These advanced systems transmit electricity wirelessly up to two meters with high efficiency. Passive RFID transponders (RFID = radiofrequency identification) are also widely used. They don’t require external power supplies or batteries. These tiny transponders can be used as smart cards for access control, car immobilizers and radio tags to mark goods. The transponder’s energy is also transmitted by the beams from the reading device. The Transrapid is a German-developed high speed monorail train that uses magnetic levitation. It can also be supplied with wireless power through inductive coupling. This technology will be especially important for electric cars. The future could see car batteries being recharged while driving along a charging lane on a road with embedded coils or plates. This would allow for extended battery range of thousands of kilometers. The challenge for e-mobility, industrial applications and RFIDs is much greater than it is for small devices and small RFIDs. With a power consumption of just 5 watts, a smartphone battery can be recharged quickly. For electric vehicles, such as autonomous mobile robots, floor conveyors, and industrial equipment, you will need 1,000 times more wireless power. These systems are still in the infancy stages. A team from the University of Colorado Boulder presented recently a test setup that can transmit 1 kilowatt in excess of 12 centimetres.
This team employs capacitive coupling rather than inductive, which is energy transmission that relies on a high frequency electric field. Future feasibility studies will be required to determine if the principle can easily be scaled up to industrial use. Industrial sectors require solutions that reduce energy losses, but also standard designs and components that can withstand harsh production conditions.
Experts agree that the Industrial Internet of Things (IIoT), which enables the interconnection of machines, warehouses and commercial vehicles as well as robots and sensors, is only possible when components are completely free from cables. This makes them more mobile and adaptable, as well as less likely to have contact issues and leaks. However, wireless power transmission is still a transitional technology. Researchers at the University of Massachusetts Amherst have recently revealed Air-gen, which is a generator the size of a fingernail that generates electricity from air or moisture in the air. Jun Yao and Derek Lovley, a microbiologist, are leading the team. They use electrically conductive protein Nanowires made by Geobacter bacteria. The Air-gen is made up of an 8-micrometer thick film of these protein nanowires (ePNs). The e-PNs create a loose network of nanochannels that allow water molecules to move through. The film is laid on a gold electrode measuring 5×5 millimeters in size. The film is partially covered by a 1×1 millimetre smaller gold electrode. This allows it to absorb the water and conduct it down through the channels. Because water cannot penetrate deeper layers it is more difficult to get into them, there is a constant concentration gradient.
Airgen currently supplies 20 hours of electricity
Yao, an assistant professor in the department of Electrical and Computer Engineering explains how electricity is generated: “A water molecule attaches to an ePN emits a partial electrical charge to it. Because of the concentration gradient, charge density in the upper layers of the film is higher than in the lower ones. This generates current flow and voltage between the electrodes. The Airgen prototype supplies continuous electric current for small electronic components at 0.5 Volts for 20 hours. The mini-cell then recharges in humid atmosphere for approximately 5 hours before it repeats the cycle. It can increase output power significantly by modeling e-PN properties. The team at Amherst believes that it can even exceed the power density of solar cell by stacking multiple Airgens. Airgen technology has many advantages over other renewable energy sources like wind and solar. Airgen works day and night, humidity is everywhere so it can even be used indoors. It is also independent from weather conditions. Professor Lovley is the head of the Department of Microbiology. He believes that Airgen can produce environmentally friendly energy. It’s far more flexible than other sustainable methods and less dependent on location. Researchers are working on small Airgen units to power smartwatches, health and fitness monitors, and other wearable devices. Later, combining multiple units will make smartphones completely battery-independent. Yao states that the long-term goal is to create large commercial units that can make a significant contribution towards sustainable power generation. Lovley says that Geobacter is not suitable to be used for the production of e–PNs in mass quantities. We genetically modified Escherichia coli, a robust bacterial strain, to make e-PNs with high yield. Glycerol, a byproduct of biodiesel manufacturing, can be used to grow large amounts of E.coli cultures at low costs. This opens the door to sustainable mass production from renewable feedstocks of Airgen generators. It will take many years of research before this technology becomes mainstream or if it can make a significant impact on the industrial and daily lives.