If you've ever seen yourself through a thermal imaging camera, you know that your body produces a lot of heat. This is actually a waste product of our metabolism. Every square foot of the human body gives off heat corresponds to approximately 19 games per hour.
Unfortunately, much of this heat simply escapes into the atmosphere. Wouldn't it be great if we could use it to generate energy? My research showed that this would actually be possible. My colleagues and I are discovering ways to capture body heat using environmentally friendly materials and store it for energy.
The goal is to create a device that can both generate and store energy, acting like a built-in power bank for wearable technology. This would allow devices such as smartwatches, fitness trackers or GPS trackers to run for much longer or even indefinitely by using our body heat.
The author won the Editor's Choice Award in Vitae's three-minute dissertation competition.
It's not just our body that produces waste heat. Our technologically advanced world generates significant waste heat every day, from the engines in our vehicles to the machines that produce goods.
Typically, this heat is also released into the atmosphere, representing a significant missed opportunity for energy recovery. The emerging concept of “waste heat recovery” attempts to counteract this inefficiency. By harnessing this otherwise wasted energy, industries can improve their operational efficiency and contribute to a more sustainable environment.
The thermoelectric effect is a phenomenon that can help convert heat into electricity. This works because a temperature difference creates an electrical potential by causing electrons to flow from the hot side to the cold side, creating usable electrical energy.
However, traditional thermoelectric materials are often made of cadmium, lead or mercury. These are associated with environmental and health risks that limit their practical use.
The power of wood
But we discovered that thermoelectric materials can also be made from wood – a safer and more sustainable alternative.
Wood has been an essential part of human civilizations for centuries, serving as a source of building materials and fuel. We are discovering the potential of wood-based materials to convert waste heat, which is often lost in industrial processes, into valuable electricity.
This approach not only increases energy efficiency, but also redefines how we view everyday materials as essential components of sustainable energy solutions.
Our team at the University of Limerick, in collaboration with the University of Valencia, has developed a sustainable method to convert waste heat into electricity using Irish wood products, particularly lignin, a by-product of the paper industry.
Our study shows that lignin-based membranes, when soaked in a saline solution, can efficiently convert waste heat into electricity at low temperature (below 200 °C). The temperature difference across the lignin membrane causes ions (charged atoms) to move in the salt solution. Positive ions migrate to the cooler side while negative ions migrate to the warmer side. This charge separation creates an electrical potential difference along the membrane, which can be used as electrical energy.
Since around 66% of industrial waste heat occurs in this temperature range, this innovation offers a great opportunity for environmentally friendly energy solutions.
This new technology has the potential to make a big difference in many areas. Industries such as manufacturing that produce large amounts of residual heat could benefit greatly from converting this waste heat into electricity. This would help them save energy and reduce their impact on the environment.
This technology could be used in a variety of environments, from providing power in remote areas to powering sensors and devices in everyday applications. Due to its environmental friendliness, it is also a promising solution for sustainable energy production in buildings and infrastructure.
The problem with storage
Generating energy from waste heat is just the first step; Effective storage is equally important. Supercapacitors are energy storage devices that quickly charge and discharge electricity. This makes them indispensable for applications that require fast power supply.
However, their reliance on carbon materials derived from fossil fuels raises sustainability concerns and highlights the need for renewable alternatives in their production.
Our research group has discovered that lignin-based porous carbon can serve as an electrode in supercapacitors for energy storage generated by harnessing waste heat using a lignin membrane.
This process allows the lignin membrane to capture waste heat and convert it into electrical energy, while the porous carbon structure facilitates the rapid movement and storage of ions. By providing an environmentally friendly alternative that avoids harmful chemicals and relies on fossil fuels, this approach offers a sustainable solution for energy storage from waste heat.
This innovation in energy storage technology could power everything from consumer electronics to wearable technology to electric vehicles.
Muhammad Muddasar, PhD Candidate, School of Engineering, University of Limerick
This article is republished from The Conversation under a Creative Commons license. Read the original article.
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