RF based wireless energy harvesting and its applications

Energy is one of the most important factors for any active system to work.  At any given moment, RF energy is transmitted from millions of transmitters and devices across the globe. There are a lot of advantages if we could harvest this energy from surrounding sources. Let’s find out what is Radio Frequency-based wireless energy harvesting and its applications.

We have been depending on many energy sources for centuries. Since the modern science and electronics industry is growing rapidly, there is a huge demand for various efficient energy sources.

What is wireless (RF) energy harvesting?

The concept of energy harvesting is to receive energy from surrounding sources and convert it into a useful form to power any applications or store the energy for future usage. In wireless (RF) energy harvesting, electromagnetic energy from multiple sources received by an antenna is converted into electric energy and used as a power source for other devices.

Radio Frequency energy harvesting technology allows power to be harvested from RF sources such as cellular towers, Wi-Fi networks, and TV/radio transmitters. The technology converts the RF energy into DC power, which can then be used to charge batteries or provide power for low-power electronics.

History

The first recorded use of RF energy harvesting was in 1908 when Nikola Tesla demonstrated the wireless transmission of electricity. In the early 1920s, Guglielmo Marconi experimented with using RF energy to power light bulbs and motors wirelessly.

In the 1930s and 1940s, several patents were filed for devices that used RF energy to power electronic devices. In 1941, Heinrich Hertz published a paper entitled “On the Possibility of Wireless Transmission of Electrical Energy”. This paper described a system for wirelessly transmitting electrical energy using RF waves.

In 1954, Arthur C. Clarke published a paper entitled “Extra-Terrestrial Relays – Can Rocket Stations Give Worldwide Radio Coverage? “. In this paper, Clarke proposed using satellites to relay radio signals around the globe. He also suggested that these satellites could be powered by solar panels or by beaming RF energy from Earth.

In 1960, Peter Glaser proposed using large antennae to collect solar radiation and convert it into electrical energy that could be beamed down to Earth. This concept is known as power beaming.

In 2001, John Perkin patented a method for harvesting RF energy from ambient sources such as television or radio signals.

How RF-based wireless energy harvesting works

Radio Frequency energy harvesting (RF-EH) technology is a process by which RF energy is converted into electrical energy that can be used to power electronic devices.

There are three main components in a typical RF energy harvesting device. An antenna is designed and perfectly tuned to a specific frequency that receives signals from its surroundings. The antenna converts electromagnetic waves into low-power electrical signals, which will be fed to an AC-to-DC converter. DC voltage will be controlled by a controlling unit that regulates the output to the load or storage.

Sources of radio waves

Any radio-transmitting device can be considered a source for wireless energy harvesting. The frequency range and operating power depend on the specific application of the transmitter.

The most common radio wave sources are mobile base stations, radio broadcasting stations, TV broadcasting, satellites, wireless LAN transmitters (Wi-Fi), and mobile devices.

Applications of wireless energy harvesting

• Battery-less power source
• RF tags for shopping
• Smart lighting applications
• Smart switches for home automation used with ZigBee technology
• Internet of Things applications
• Recharging of devices
• Power source for smart sensors
• Simple design and cost-effective
• Easier implementation

Advantages of wireless energy harvesting

• Conventional power sources can be replaced
• Unlimited spectrum of sources
• Efficient source of energy
• No wastage, green energy
• No need for periodic replacement of the battery
• Extended life for devices due to recharging of storage battery during sleep mode

Future of wireless energy harvesting

There is a lot of potential for wireless energy harvesting for applications like the Internet of Things and home automation projects. Smart sensor technology is capable of producing low-power devices with advanced embedded technology, which typically operates at microwatt input power.

Wireless sensors for temperature, humidity, and proximity sensors are used in the industrial, home automation, and automobile industries. Wire-free charging of any electronic device would be possible with advancements in wireless energy harvesting technology.

Our future mobile devices will be capable of using wireless charging technology as an alternate power source. Wearable devices and medical sensors will be using wireless energy as a power source.

Enhanced security devices with smart sensor technology can make use of power from wireless energy harvesting. It has advantages due to wire-free wireless transmission, compact size, and the modules’ ability to be easily implemented anywhere.

Limitation of wireless energy harvesting

RF energy harvesting is limited by the amount of power that the radio waves can transmit.

The distance between the transmitter and receiver also limits the efficiency of RF energy harvesting. The further the distance, the less power is received by the receiver.

Wireless energy harvesting has a lot of limitations due to its dependency on external sources, which are prone to atmospheric changes, physical obstacles, and radio wave source uptime. Received power from the sources is too low, and the level often varies over time.

System efficiency is reduced over time due to the performance of the components used in the devices, like capacitors, diodes, backup storage batteries, etc.…  The design of receivers in a wide frequency range is often challenging; a device designed to operate at one frequency band is limited only to that spectrum.

Challenges for implementation

The energy in RF waves is very weak. It is only a tiny fraction of the energy in an electrical current. This makes capturing the energy and converting it into useful power difficult.

The energy in RF waves is spread out over a wide range of frequencies. This makes it difficult to isolate the energy and convert it into useful power.

The energy in RF waves is often intermittent. This makes capturing the energy and converting it into useful power difficult.

Conclusion

In conclusion, emerging technologies like the Internet of Things will require an efficient energy source to connect billions of smart devices and sensors for a wide spectrum of applications. Long-term sustainable and reliable energy sources are inevitable for any efficient system. Wireless energy harvesting is an area for future developments to deliver effective solutions for IoT, medical, industrial, and other smart home applications.