It might sound nuts but researchers at the University of Waterloo (UW) have developed a device that can generate enough electricity to power a calculator using only walnut shells and drops of water. “I was eating a hazelnut once in my home and I saw the nut’s structure,” said Nazmul Hossain, a PhD student in mechanical and mechatronics engineering. He then examined the discarded shell pieces under an electron microscope. “Something came to my mind – we can utilize this natural structure to harvest energy,” Hossain said. Where most people might only see dips and divots inside a nut’s shell, he saw the complex network of pores as a potential travel system for electricity. He and a team of researchers tried out different nuts and found they could get the most wattage out of walnuts. Researchers then optimized the shells for that purpose by cleaning, treating, polishing and cutting them into precise shapes. The discovery comes at a time when industries are struggling to find new renewable energy sources. “The good thing is that it’s agricultural waste,” explained Hossain. “We are just throwing it out. We don’t utilize it.” In a nutshell, the team uses a device, known as a water-induced electric generator (WEG), to produce electrical energy as water evaporates from a network of pores that make up the shell’s structure. The method is called hydrovoltaic energy harvesting. As the water moves, it transports electrically-charged ions, which interact with the shell’s surface to create a charge imbalance that generates electricity. “As the water is going through the holes, it generates electricity,” explained Roozbeh Abbasi, who co-supervised the project, as he showed a monitor tracking the electrical current. However long it takes for the water to evaporate is how long it can send an electrical current. The researchers at UW are working to develop wearable WEGs capable of harvesting energy from sweat or rain, and on practical applications such as powering sensors to detect water leaks. “I hope I can utilize this for even further electronic devices, like the smartwatch or small biomedical devices,” said Hossain. “We can even wrap it in our hand just behind the smartwatch so it can be used and bend with the smartwatch.” Researchers have also experimented with wood instead of nut shells. Hossain was supervised by Dr. Norman Zhou, a professor of mechanical and mechatronics engineering, and Dr. Aiping Yu, a professor of chemical engineering.
