In this blog post, we explore the principles and potential of harvesting technology, which collects the minute energy wasted in everyday life.
Smartphones, watches, laptops, light bulbs, heating. What do they all have in common? They are powered by energy. Almost every device we use requires energy, which is converted into various forms for use. Some devices convert electrical energy into light energy for use, while others transform electrical energy into kinetic energy. For example, the light bulbs we commonly use convert electrical energy into light energy, and cars burn fuel to obtain kinetic energy. However, during this process, most of the energy is released and lost in the form of heat energy. This is a common phenomenon in daily life, yet it’s also something we easily overlook.
Energy efficiency refers to the ratio of useful energy output to the energy input. For instance, a fuel cell’s energy efficiency is about 60%, which is quite high. Yet, the remaining 40% of energy is still lost as heat, which can be highly inefficient. We often think we use electricity efficiently, but in reality, a significant amount of energy is wasted. Energy losses in large-scale industries or transportation are especially greater than we imagine. Efforts are needed to reduce losses occurring during energy conversion, thereby maximizing the utilization of energy resources.
In this context, a technology gaining recent attention is energy harvesting. Energy harvesting is the technology of collecting energy that might otherwise be discarded in daily life and converting it into electricity, utilizing various forms of energy we often overlook. It collects thermal energy emitted when the aforementioned devices operate, or converts the minute pressure or friction energy generated when we touch our smartphones or press laptop keyboards into electricity. On a larger scale, it can even collect and utilize vibrations or heat generated during the operation of cars or airplanes.
For energy harvesting, devices capable of effectively gathering energy emitted from the surroundings are necessary. Several principles apply to these devices. The first is the piezoelectric effect. This effect converts mechanical energy—such as vibrations, pressure, or impact—into electrical energy through piezoelectric materials. This principle is easily observable in daily life; for instance, it is used in recorders that store sound waves as electrical signals. Applying this principle to energy harvesting enables the production of electrical energy from the pressure generated when a person bends their knee or elbow joint, or the development of remote controls that convert the kinetic energy from pressing buttons into electricity. This represents one method for efficiently utilizing energy that naturally occurs in daily life.
Another principle applied to energy harvesting devices is the thermoelectric effect. This phenomenon describes the relationship between thermal energy and electrical energy. Specifically, the Peltier effect states that when two materials with different temperatures are joined, a voltage difference arises due to the temperature difference, causing a current to flow. Attaching such a device to equipment allows the heat generated by our bodies or machinery to be converted into electrical energy for use. For example, applying this technology to portable electronic devices allows the heat energy generated when the user walks to be converted into electricity to charge the device.
Additionally, principles like the photoelectric effect and electromagnetic resonance can be used for energy harvesting. The photoelectric effect occurs when light of a certain frequency or higher strikes a metal, causing electrons to move and generate a current. This can be utilized to convert the light energy from sunlight or light bulbs into electrical energy. Using this technology allows for efficient production of electricity from light energy without directly harnessing solar power. Next, electromagnetic resonance generates electrical energy when an external alternating magnetic field causes the electrons or nuclear spin systems of atoms possessing magnetic moments to absorb energy at the resonance frequency. This principle can be used to develop systems that convert the magnetic field energy generated when swiping or tapping a card into electricity.
Energy harvesting technology is still in its early stages and not yet commercialized, but its potential is limitless. The examples presented here are technologies currently under development or in the experimental phase. However, if all these energy collection methods are perfected and integrated in the future, we will no longer need to charge devices separately or carry batteries. Innovative devices like wearable computers will emerge, capable of absorbing various types of energy emitted from their surroundings and utilizing it as their own power source. An era may arrive where simply wearing a device on your wrist, in contact with your body, allows it to effectively absorb and utilize diverse energies generated during daily life.
Furthermore, energy harvesting technology might potentially slow the depletion of Earth’s dwindling resources by maximizing energy efficiency. This could play a crucial role in solving the energy challenges we face and make a significant contribution to environmental protection. If this technology becomes commercially available, it is expected to have a positive impact not only on the environment but on humanity as a whole. I hope this groundbreaking technology becomes a reality in the near future and am curious about how the changes it brings will transform our lives.
