Energy, in its many forms, is what keeps the world turning in more ways than one. We eat energy, we drink energy, we sell energy, but we can never destroy energy. Energy cannot be destroyed, nor can it be created, only converted. You may hear the phrase ‘wasted energy’, which usually refers to the generation process of gas and electricity; however, this does not mean that the wasted energy disappears forever; it means that the potentially useable energy that the original material had was converted into an energy type that is useless to us, unless converted once again. A good example of this would be in a power plant: when electricity is generated almost two thirds of potential energy stores are lost to the environment, primarily as heat energy. At present, this energy is simply released into the atmosphere through cooling towers. However, what if there was a way of recovering this energy and converting it into something useful?

What is energy harvesting?

Energy harvesting is a practice that has fairly recently received much more attention and funding. The main aim behind it is to convert ‘wasted’ energy from a variety of actions and turn it into useable electricity. A common way in which it achieves this currently is to create self sustaining models that use the energy used in powering the device to once again power itself in a continuous fashion. It is not, however, very developed at present, and as such is not quite ready for total commercial deployment, but nevertheless is an enormous step in the right direction for sustainability and efficiency.

How has it been used so far?

So far, energy harvesting technologies have been used in a variety of devices; however, not many of them have been released onto the mass markets. The majority of energy harvesting devices are contained to rather small devices, mainly because they don’t need as much energy to function and thus can be tested and adapted much easier. There are exceptions, however, which you can see below along with some of the smaller devices.

Mobile phone chargers

Important in today’s day and age, self-sustaining chargers are becoming rather in-demand. This has been achieved through energy harvesting using the following methods:

  • Kinetic charger which uses the energy generated through movement, mainly exercise, to power your phone.
  • Temperature powered charger that uses the temperature, whether it be hot or cold, of an item, such as a hot beverage, to power your phone.
  • Wind powered charger much like a small wind turbine, these chargers use the power of wind energy to charge your phone.

Movement sensors

By using the heat emitted from an approaching person, the sensor is powered by converting this energy into useable electricity. This is one of the only energy harvesting forms that has been sold on a semi-mass scale. You may still find it difficult to get your hands on one in your local DIY shop, but they’re certainly more popular than most devices.

Pressure powered remote control

Using a larger button that acts as the source of power, once pushed down, enough electrical potential is generated to communicate multiple requests to your television. This hasn’t left the prototype phase as of yet, but there are fully functioning versions of it.

Kinetic floor tiles

Using the pressure placed on the tiles by people’s footsteps, the technology inside the tiles translates this energy into useable electricity and is being used to power such things as ticket gates. During the Paris Marathon in 2013, kinetic floor tiles were used to create 4.7 kWh of electricity, enough to power a laptop for two days.

Types of energy harvesting

This is the technical part. There are three main types of micro energy harvesting, which is used in the majority of the abovementioned devices. These are named and described as follows:

Piezoelectric harvesting

This type of energy harvesting is when we use materials in which electricity results from pressure. Basically, when if you apply pressure to a material, it creates electrical potential. This is the type of harvesting used to power the remote control and the kinetic floor tiles.

Thermoelectric harvesting

This type of energy harvesting uses the opposition of two temperatures to create electrical potential. This is when two materials of contrasting temperatures meet and create an electrical charge. This method has been used to create a coaster phone charger and generator for cars and lorries that converts the heat lost in the engine.

Pyroelectric harvesting

Not to be confused with thermoelectric, this type of harvesting uses temperature change over time to power its subject. When temperature increases or decreases over time there is a temporary voltage created, which is then harnessed and used as electricity. This is used in the abovementioned movement sensors.