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What is Energy Harvesting?

We all use energy in everything that we do, whether that be gas and electricity, or the physical energy needed to carry out daily tasks, such as walking to work, hoovering the carpet or lifting weights at the gym. Each of these activities, including the usage of gas and electricity, 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 store is lost, primarily in heat that is released into the environment. This level of efficiency is just not good enough, which is why much research and development has been put into ‘energy harvesting’ in recent years, which in basic terms, means taking the energy that would be otherwise lost in such ways as heat, light, vibration and movement, and utilising them, allowing for more self-sustaining technologies and higher efficiency rates.

How does it work?

Energy harvesting, or energy scavenging as it is sometimes referred to as, is still in its early developmental stages. Its full potential has not yet been reached and is still being used on quite a small scale. The main aim for much of the energy harvesting technologies is to improve efficiency to the point where devices can be self-sustaining, using the energy lost in their functionality to power themselves in a circular process. There are a number of ways in which this is carried out, primarily linked to the manner in which electrical voltage can be picked up from energy wastage. Below you’ll see some of these methods, and although their names my sound extremely complex, they can be explained in quite basic terms:

Piezoelectric harvesting

Meaning: Using materials in which electricity results from pressure.

Using this method, we can target sources of energy such as human motion, low frequency vibrations or acoustic noise, where pressure on a surface creates a small electricity voltage. Using piezoelectric harvesting we could carry out such things as:

Batteryless remote control

The force that is used in order to press down a button on the remote control is sufficient enough in itself, if it is equipped with the sufficient harvesting technology, to sustain and power itself using energy emitted from its own functionality. A great example of this is the infrared, batteryless remote developed by Arveni in Grenoble, France. As pictured below, you can see that the remote has a central, larger button, that once pressed down has the ability to send up to 9 signals to your television set.

Source: Arveni
Bateryless remote

Piezoelectric floor tiles

When pressure by form of footsteps is applied to certain materials, the composite atoms are disturbed and electrical potential is therefore created. Technology is now being developed that can harvest this electrical voltage and convert its potential into usable electricity. Kinetic tiles, as they’re often called, are being used in circumstances with large crowds such as festivals and concerts in order to power things such as ticket gates. A good example of piezoelectric floor tiles being used was at the Paris Marathon in 2013, when 4.7 kWh of electricity, enough to power a laptop for two days, was generated solely from the runners steps on the floor.

Thermoelectric harvesting

Meaning: Using multiple materials that create a voltage by means of their temperature opposition.

This method harvests the voltage created by the difference in temperature between two dissimilar objects. If the two opposing materials remain at a constant temperature, the intercepting ‘middle object’ will see a steady voltage. Harvesting this charge, we can develop technologies such as:

Temperature powered phone charger

The ‘onE Puck’ thermoelectric charger developed by Epiphany Labs is a fantastic example of how thermoelectric harvesting can be used to create a self-sustaining electrical system. By placing a hot or cold item, ideally a drink, on the coaster-style product, you’ll be able to charge your phone due to the conversion of the voltage created by material temperature. As you can see in the image below, this small device is proof of what thermoelectric harvesting can achieve.

Source: Epiphany Labs
Renewable energy coaster charger

Thermoelectric generator for cars and lorries

Generators that use thermoelectric harvesting convert the heat that is created in the general operation of cars and lorries and convert it 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 reduced fuel consumption by around 5%. This does not create a self-sustainable model; however, it does increase efficiency and reduces the amount of fuel needed to power the car.

Pyroelectric harvesting

Meaning: Using materials that are subject to temperature change over time.

The method of pyroelectric harvesting relies on the creation of a temporary voltage caused by temperature change in some materials. Its main usage at the moment is in sensors. It is worth noting that this method is not quite ready for commercial systems.

Pyroelectric sensor

A good example of this is in a passive infrared (PIR) sensor that can be used in such scenarios as outdoor lights that will turn on when motion is detected. The pyroelectric element uses the small voltage created from the heat emitted by the person approaching to power the light. This creates a self-sustainable model from the most unlikely of sources.

What about large scale energy loss?

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? Well, although most of it, predictably, goes to waste, more and more effort is going into harvesting these energy sources as time goes by. Millions and millions of pounds worth of investment has gone into the development of renewables, and solar and wind are two of the main methods.

Wind Energy

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. The difference is, the waste energy is not coming from a man made process like the heat loss from power stations. Increasingly, renewable energy companies all around the world are investing more and more time and energy into capitalising on wind energy generation. In the United Kingdom, electricity generated through wind turbines accounted for around 11% of all electricity used in 2015. 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 smaller scale, wind harvesting is being used for such things as camping stoves and phone chargers. Like the below example, the iFan phone charger designed by Tjeerd Veenhoven uses wind to power its small generator and therefore charge up your iPhone. These sorts of small innovations are baby steps towards integrating renewable, self-sustaining technologies into our daily lives.

Solar Energy

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 miniscule amount of that energy is actually being converted into useful electricity for the earth’s usage. The main problem with solar energy at present is that the equipment needed to convert the 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; however, with time this is improving gradually. At the moment, electricity coming from solar energy generation represents around 1.2% of all electricity used in the United Kingdom, the largest amount of which coming 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 some incredible products being developed, namely those with regards to remote usage scenarios, such as camping. 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.

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