The Technology Which Could Harvest Energy from Our Footsteps

The first law of thermodynamics is quite widely known: energy can not be created or destroyed, it can only be transferred into different kinds of energy. A lot of our technologies take advantage of the transfer of energy. For example, the concept of hydropower uses the kinetic energy of moving water to produce mechanical energy or electricity.

A grist mill with a stationary water wheel. Source: paulbr75.

In our day to day lives we use a lot of energy; and not only in terms of forgetting to turn the bathroom light off. Every time we walk up the stairs. Every time we prance down the street. Or every time we light up the dance floor. All of these situations can be interpreted as a wasted opportunity to harness energy. 

There are many different fields of science, and in the current day there is a big focus on developing sustainable technologies. While everyone knows the biggest competitors, there are also others being developed. One such technology is that of piezoelectric energy harvesting.

Under pressure

Piezoelectric materials are in particular being developed by Professor Beatriz Noheda. She works at the Zernike Institute for Advanced Materials at the University of Groningen. While studying there, I had the chance to talk to her about them and learned quite a lot in the process. 

Like most words and symbols in science, piezoelectric has roots in the Greek language, with ‘piezo’ meaning ‘to push’. Essentially, piezoelectric materials produce electricity when put under pressure. These materials are already widely used in sonar and ultrasound technologies, and even in vending machines. 

However, these materials could also be used to harvest energy. Professor Noheda told me that the main idea behind energy harvesting was self sufficient devices. One example she gave was pressure sensors in cars. The sensors will measure the tyre pressure while simultaneously using the vibrations of the car to power itself. This is a win-win when it comes to reducing the carbon footprint of the vehicle as the tyre pressure itself affects energy usage.

Bumps along the road

While you could argue a bump along the road could be a benefit for the previous example, in a metaphorical sense it certainly isn’t. Right now, using these materials in a broader sense isn’t really possible. This is because they are currently quite toxic, as the best piezoelectric materials contain lead. Finding less toxic alternatives is one of the main areas of the Professor Noheda’s work. 

However, there are some distinct benefits if this issue were to be addressed. While these materials have a low energy density compared to solar – you need a surface 100 times bigger to produce the same energy – they have an advantage in that they don’t require the sun and can be hidden from sight. As such, they can be utilised at all times of the day. 

Step-by-step

Given the low energy density of piezoelectric materials, it will certainly be a while before there is wide spread application of the energy harvesting technique. Nonetheless I’m imagining a future in which our staircases are lined with these devices, lighting our way as we pass, as well as our dance floors flickering in response to footsteps. 

Footsteps in the sand. Source: blue budgie.

In the end, it is in every aspect a step-by-step process. As our technologies advance, the energy our devices use also decreases. Further down the line we could end up with a Tinder-style situation where the energy usage of our devices matches the energy piezoelectric devices can produce.

To me, this seems like a technology of the future. For now, our focus should be on getting to a point where we can enjoy it properly. For the present, I’m just preparing myself to be like a piezoelectric material in building my career: effective under pressure. 

 

*This post is a rewrite of a post already written by Jack in 2016, published by Energy Academy Europe. 

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Jack McGovan is a recent graduate in chemistry with a specialisation in ‘Energy and Sustainable Chemistry’ from the University of Groningen, the Netherlands. Following a job as a student journalist covering the energy transition, he has moved to Berlin where he is following his passion for working towards creating a fairer and more sustainable world. Seeing a gap in the way in which the world of science was communicated, he founded Delta-S. By writing source based content, he hopes to communicate his findings to a wider audience.