An Introduction to Energy Harvesting Technology

We live in exciting times! The Internet of Things (IoT) has brought us many devices that make our lives easier and more enjoyable. As they are developed, network technology companies create the cabling that makes it all possible. However, a considerable portion of IoT devices are powered by batteries. And billions of devices need perhaps trillions of batteries to keep them running. The kind of devices we are talking about are things like:

• Calculators
• Digital cameras and camcorders
• Electric razors and toothbrushes
• Laptops
• Portable radios and TVs
• Power tools
• Smartphones
• And more

Trillions of batteries are a logistical nightmare; however, more than that is the damage discarded batteries do to the environment. Improperly discarded lithium-ion (Li-Ion) batteries leak into the soil, cause fires, and even explode. A recent case in point: On June 30, 2021, 100 tons of lithium batteries stored in a former paper mill in northern Illinois exploded and caused the evacuation of 1,000 homes in the vicinity.

The Need for Energy

Healthcare focused semiconductor company ONiO states:

Globally, we use about 607 quintillion joules of energy each year. Our energy needs are only increasing, with our rapid population growth, and global energy expenditure is expected to be around 777 quintillion joules by the year 2040. These are mind-bending figures, and it is no wonder then that issues of energy and energy shortage feature so prominently in global policymaking.

With the prediction that the raw materials used to make lithium batteries will be scarce by 2050 and the fact that disposal is so unmanageable and dangerous, many researchers and companies are developing a technology called energy harvesting.

Energy Harvesting

Maxim Integrated defines energy harvesting as follows:

Energy harvesting (also known as power harvesting or energy scavenging) is the process in which energy is captured from a system’s environment and converted into usable electric power. Energy harvesting allows electronics to operate where there’s no conventional power source, eliminating the need to run wires or make frequent visits to replace batteries.

An energy harvesting system generally includes circuitry to charge an energy storage cell, and manage the power, providing regulation and protection.

Simply put: Energy harvesting captures small amounts of ambient energy and converts it into electricity.

Ambient Energy

Ambient energy is all around us and it is going to waste. For example, there is:

• Heat energy from wasted energy from heaters, friction, engines, furnaces, etc.
• Light energy from the sun or artificial lights
• Kinetic energy from ocean waves, river currents, sound waves, even movement of people as they walk
• RF energy from radio, cellular and TV transmitters, satellites, and wireless communication systems

Researchers feel that all this ambient energy can one day be captured, turned into electricity, and used to power our world. Energy harvesting is still in its infancy; however, this technology is being used today to power low-power devices.

The Components of an Energy Harvesting System

In its most simple form, an energy harvesting system has three major components:

1. Transducer: This is the energy harvester. Depending upon the source of the energy, the transducer will be in one of these forms:

• Thermoelectric (heat)
• Photovoltaic (light)
• Piezoelectric (kinetic)
• RF (radio frequency)

1. Energy storage: This will be in the form of a battery or supercapacitor.
2. Power management: This consists of regulators and complex control circuits that make the power suitable for its intended application.  

Figure (A): Basic components of an energy harvesting system

The Main Applications for Energy Harvesting Technologies

Today, energy harvesting systems are capturing ambient energy, converting it to electricity, storing the electricity, then delivering it to small autonomous sensors such as those developed using micro-electromechanical systems (MEMs). These tiny sensors are found in commercial, medical, and industrial applications such as:

• Equipment monitoring 
• Implantable medical devices (eg., pacemakers) and remote patient monitoring
• Internet of Things (eg., wearable electronics)
• Remote corrosion monitoring systems (e.g., air pollutions, forest fires)
• Radio Frequency monitoring (RFID)
• Structural monitoring (e.g., worn out bearings, bridge stress) 

Summing Up

According to the EE Times:

Energy-savings initiatives are a key driver in the growth of the energy harvesting equipment market. Companies are considering a whole series of tools necessary for energy harvesting to satisfy the growing demand for energy.

There is true potential for this cutting-edge technology. Even though the energy being harvested for any one application is measured in mere milliwatts, it can be used to power wireless sensors and other low-powered devices. Pairing this with things such as PoE lighting, and other smart building measures, they can add up to real energy conservation.