Energy is, and always has been an integral part of everything we do, whether that be gas and electricity, or the energy needed to perform daily tasks such as taking your dog for a walk, making the bed or playing a game of tennis. When we carry out any of these activities or use gas and electricity in our homes, we need a source of energy that allows us to do so. In both the creation and output of this energy, there is a huge amount that is lost in the process, most of which going completely to waste.

A prominent example of this is when electricity is generated in a power station; roughly two thirds of potential energy stores from the source are lost, primarily as heat which is released into the environment.

Unfortunately, as the earth’s population and demand for energy continues to expand rapidly, this level of efficiency simply isn’t sufficient. As such, many researchers and renewable energy enthusiasts are focusing their efforts on a concept called ‘energy harvesting’. This basically means that any energy that would usually be lost in the creation or output process, namely through heat, light, vibration and movement will be harvested and used to create self-sustaining technologies and increase efficiency rates.

What is Energy Harvesting?

Energy harvesting can be described as a process of capturing and amassing byproduct energy when it is readily available and can be converted into usable electrical energy – such as operating a microprocessor within its limits. Energy harvesting is of great importance for both low-voltage and low-power applications in a wide range of portable or mobile markets such as consumer devices, medical equipment, transportation, industrial controls and military.

It is also crucial for applications that need a backup battery, especially if the battery is located in a remote location that is difficult to reach. Perhaps, the biggest hope is that energy harvesting would help new market applications and products that are currently not possible or even thought of yet. The energy can be derived from a lot of sources that would otherwise get wasted or remain unusable for any practical purpose.

This process, also called energy scavenging, is about capturing residual energy as a byproduct of a natural environmental phenomenon or industrial process and can be also considered to be “free energy.” Quite often, this residual energy gets released into the environment as waste.

Examples of this scenario would be mechanical energy because of vibration, thermal energy produced by heat escaped from furnaces, stress and strain, combustion engines and other heating sources. Other important sources are biological, solar energy coming from all types of light sources; coils and transformers; electromagnetic energy captured via inductors, wind and fluid energy coming from air and liquid flow; chemical energy from naturally recurring or biological processes; and the mammoth amount of RF (Radio Frequency) energy in the environment due to the ubiquitous radio transmitters and television broadcasting.

Few known sources of harvesting energy that are available in the environment 

Why Harvest Energy?

As we all know, the majority low-power electronics, such as embedded devices and remote sensors, are powered by batteries. However, even when it comes to long-lasting batteries, they have a limited existence and need to be replaced every few years. The replacements can turn out to be extremely costly as there are hundreds of sensors in remote locations. Whereas, energy harvesting technologies supply unlimited operating life of low-power equipment and even remove the need to replace batteries where it is costly, unfeasible, or unsafe.

Most of the energy harvesting applications are made to be self-sustaining, cost-effective, and also require minimum or no servicing for many years. Additionally, the power is used closest to the source, which completely eliminates transmission losses and long cables. When the energy is enough to power the device directly, the application or device powered by the energy can operate without batteries.

How Energy Harvesting Works?

The entire process of energy harvesting can be classified in various forms depending on their source, amount, and type of energy being converted to electrical energy. In its simplest form, the energy harvesting system needs a source of energy such as heat, light, or vibration, and these three key components.

  • Transducer/harvester: This is the energy harvester that is responsible for collecting and converting the energy from the source into electrical energy. Typical transducers comprise of photovoltaic for light, inductive for magnetic, thermoelectric for heat, RF for radio frequency, and piezoelectric for vibrations/kinetic energy.
  • Energy storage: Such as a super-capacitor or battery.
  • Power management: This conditions the electrical energy into a suitable form for the application. Common conditioners are regulators and complex control circuits that can run the power, based on power needs and the available power.

Energy Harvesting Technologies

When it comes to harvesting electrical power from non-traditional power sources with the help of thermoelectric generators, piezoelectric transducers, and solar cells always remain a challenge. All of these need a form of power conversion circuit for efficiently collecting, managing, and converting the energy from these sources into usable electrical energy for wireless devices, microcontrollers, sensors, and other low-power circuits.

Converting waste energy to heat?

A more reliable method of generating electricity is to combine heat and power (CHP), which is an efficient, clean, and reliable approach to producing electricity and heat energy from a single fuel source such as natural gas, biomass, and biogas, coal, waste heat, or oil. This is possible by using cogeneration plants, which generate energy on-site at manufacturing facilities.

Waste heat to electricity uses less fuel to produce a given energy output and avoids transmission and distribution losses that occur when electricity travels over power lines. It also decreases the impact of outage

Benefits of Energy Harvesting

There is abundant energy in the environment, which can be converted into electrical energy for powering a variety of circuits.

Energy harvesting is useful as it offers a means of powering electronics where there are no conventional power sources. It also eliminates the need for replacing batteries frequently and running wires to end applications. It also opens a lot of new applications in many remote locations, difficult-to-access locations and also underwater where batteries and conventional power are not practical to use.

Applications for Energy Harvesting Technologies

Alternative power sources help increase the battery life of remote sensors in industrial, commercial, and medical applications. It also helps the installation of standalone sensors in hard-to-reach or remote areas to provide a variety of information and warnings. These sensors can effectively supervise and warn when it comes to air pollution, bridge stresses, worn-out bearings, forest fires, and more.

Other applications include:

  • Remote corrosion monitoring systems
  • Implantable devices and remote patient monitoring
  • Structural monitoring
  • RFID
  • Internet of Things (IoT)
  • Equipment monitoring

Therefore, the whole concept of harvesting energy from nonconventional sources in the environment has gained popularity over the last few years as many designers are looking for alternative energy sources for low-power applications.

Conclusion

Today, energy harvesters do not usually produce enough energy to perform mechanical work. However, they provide small amounts of power to support low-energy electronics. In most cases, the “fuel” for energy harvesters is naturally present and may be considered free.

Using natural sources such as solar power, thermal energy and wind energy in remote areas for energy harvesting is an attractive alternative to inconvenient utility and battery power. These natural energy sources may be available maintenance-free for a lifetime. Energy harvesting can also be an alternative energy source that supplements the primary power source and enhances its reliability. 

Energy harvesting, as a technology, is still in a nascent stage of maturity. It is by no means the answer to all our energy woes. However, it does hold tremendous promise when it comes to powering low-power electronics. With the rapidly expanding IoT market, this spells massive potential for this technology.

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