A Simple Guide to Energy Harvesting Technologies
Also known as power harvesting or energy scavenging, energy harvesting simply means capturing ambient energy that would be otherwise lost into the surroundings - such as heat, light, vibration and movement - and converting it into electrical energy. Read on to find out how small scale energy harvesting technology works and discover some of its potential uses.
What is meant by energy harvesting?
Energy harvesting makes the most of free and renewable energy sources, as opposed to costly, large-scale generation. We all use energy in everything that we do, whether through using gas and electricity to heat our homes and power our devices, or the physical energy needed to carry out daily tasks, such as walking to work or making the bed. Each of these activities requires both the creation and output of the energy required to carry them out.
In both cases, there is a lot of energy lost in the process, which generally goes to waste. One of the biggest examples of this is when electricity is generated in power stations, in which almost two-thirds of the potential energy conversion is lost into the environment.
Energy harvesting means taking energy that would usually be lost in the creation and output process - in particular, heat, light, vibration and movement - and harvesting it to power self-sustaining technologies and increase the efficiency rates of others.
Why is energy harvesting important?
As we grow in numbers worldwide, it’s becoming increasingly important to increase our energy efficiency. Energy harvesting could be a way to collect otherwise wasted energy and use it to power electronic devices as an alternative to conventional power sources.
In addition to helping the environment, it could also be applied in remote and difficult to reach areas, and also in places where batteries and conventional power sources are not practical, such as underwater.
As energy harvesting is still very much in its early developmental stages, its full potential has not yet been reached. The main aim for energy harvesting is to improve reliability to the point where devices can be self-sustaining, using energy lost in their own functionality to power themselves in a circular process.
While solar panels and wind generators are the most well known and utilised sources for energy harvesting, in this article we’ll take a look at some of the lesser-known methods and how they can be employed in our daily lives.
Piezoelectric energy harvesting
Some materials produce an electric current when pressure is applied to them. This is known as piezoelectrical energy. Crystals, certain ceramics and bone are all considered piezoelectric materials.
With the piezoelectric effect, we can utilise sources of energy such as human motion, low-frequency vibrations or acoustic noise, with pressure applied to a piezoelectric actuator creating a small voltage.
What could piezoelectric energy harvesting be used for?
Piezoelectric energy harvesting can be used to power low-consumption devices such as wearable technology, LED lights and GPS receivers by converting energy from the human body into electrical energy.
Other examples of technologies that make use of piezoelectric energy harvesting include:
Piezoelectric floor tiles
Some tech companies, such as Pavegen Systems, also hold ambitions for piezoelectric energy harvesting to be used on a larger scale in the near future, helping to power our cities through utilising kinetic flooring in high traffic areas. This could see lighting, mobile phone charging stations at bus stops and interactive displays powered by foot traffic alone.
Batteryless remote controls
On a somewhat slightly smaller scale, the force that is used to press down a button on the remote control has enough potential to enable a self-powered tv remote. A great example of this is the batteryless remote developed by Arveni in Grenoble, France.
Reducing our reliance on batteries for small electronic devices does not just make environmental sense but will also help bring down consumption costs, reduce hazardous battery waste and improve efficiency in the long run.
Thermoelectric harvesting collects the voltage created by the difference in temperature between two dissimilar objects, rather than just wasting this heat. This method of energy harvesting requires multiple materials that create a voltage using their temperature opposition.
What could thermoelectric energy harvesting be used for?
By harvesting thermoelectric energy charge, we can develop technologies such as:
Temperature powered phone charger
Lightweight thermoelectric generators that use heat as an alternative power source to charge electronic devices such as phones, tablets and wearable tech demonstrate how this form of energy harvesting can be used to create a self-sustaining electrical system.
By placing a hot item, such as a cup of tea or coffee, on the thermoelectric generator panel, you can charge your phone due to the conversion of the voltage created by material temperature.
Thermoelectric generator for cars and lorries
Generators that use thermoelectric harvesting convert the heat that is created through the general operation of cars and lorries and convert that into electricity. This puts less pressure on the engine and battery, meaning fuel efficiency can be increased.
Studies have shown that installing cars and lorries with these generators could reduce fuel consumption by around 5%. While this does not create a self-sustainable model, it does increase efficiency and reduces the amount of fuel needed to power the car.
RF Energy Harvesting
Radiofrequency energy (RF energy) is broadcast from radio transmitters across the globe, such as mobile phones, televisions and laptops. These signals that are being generated around us all the time can be converted to direct current power with energy harvesting receivers.
RF energy harvesting has the potential to wirelessly charge a wide range of low-power devices, such as GPS trackers, wearable tech and e-book readers. RF energy harvesting is also considered as a promising alternative to batteries to power devices as part of a smart home system.
Energy harvesting on a large scale
The above examples of energy harvesting are, at present, very much generating electricity on a small scale. However, what about the 173 trillion kilowatts of energy that hit the earth from the sun and the endless amounts of wind that has enough energy to blow down trees? Although most of it, predictably, goes to waste, more effort is going into harvesting these energy sources as time goes by. Millions of investment has gone into the development of renewable electricity sources, and solar and wind are two of the main methods.
On a large scale, wind turbines are a form of energy harvesting, using energy that would otherwise go to waste to power our homes and businesses. Increasingly, renewable energy firms around the globe are investing more time and energy into capitalising on wind power generation.
In the United Kingdom, electricity generated through wind turbines accounted for around 22% of all electricity used in 2020. One wind farm alone, like the Whitelee Wind Farm in Glasgow, has the capability of generating 539,000 kW, enough to power 761,000 homes.
On a much smaller scale, wind harvesting is being used for such things as camping stoves and mobile phone chargers, such as the iFan charger, which uses wind to power its small generator and therefore charge your phone. These sorts of small innovations are baby steps towards integrating renewable, self-sustaining technologies into our daily lives.
The earth receives roughly 173 trillion kW of energy from the sun at any given moment, which is 10,000 times more than the whole world’s population uses. However, at present, just a minuscule amount of that energy is actually being converted into useful electricity.
The main problem with solar energy at present is that the equipment needed to convert sunlight is extremely expensive. Not only this, but the amount of money spent does not reflect the amount of return. As of yet, the efficiency of most solar panel systems is still quite poor, though with time this is improving gradually.
At the moment, electricity coming from solar energy generation represents around 4.5% of all electricity used in the United Kingdom. The largest amount of this comes from Chapel Lane Solar Farm in Bournemouth, which covers an astounding 310 acres, the size of 175 football pitches.
On a small scale, solar power has been powering everyday appliances such as calculators and torches for years. However, huge advances in solar technology have seen a number of innovations. Large remote solar panel systems can now be transported and used wherever you are, accompanied by solar integrated devices too such as skylights, phone chargers and speakers.
While still in its early stages, energy harvesting could play a huge part in helping reduce our global carbon footprint. Harnessing as much of this otherwise wasted energy as possible can help contribute to efforts to reach Net Zero carbon emissions by 2050 and protect our planet for future generations.