Welcome to the September 2016 installment of the Direct Energy Buzz! The apples are already ripening, which means the autumn harvest is not too far away. With that in mind, we’re going to look at some new technologies being used to harvest energy, from fish bio-waste to our own body heat – and even from dangerous spent nuclear fuel rods.
Scaleable Energy Generation
The problem for electric medical implants, like a heart pacemaker, is that they need a power source to work. Battery packs are commonly implanted under the skin, but they need to be replaced — which means additional surgery. Wouldn’t it be nice to have a device that could harvest electricity from movement of the heart to power the pacemaker? Such a device would reduce the number of surgeries and potential problems from a battery pack, and all it would need to do is generate a little electricity from your body. Sounds totally fictional, right?
Not entirely! When some materials, such as amber, crystals, or bone, are put under pressure, they give off a piezoelectric charge. All it takes to generate power, therefore, is a little bending or vibration, which can be caused by your body’s natural, day-to-day movements.
And it exists! Researchers at Jadavpur University in India took fish scales (which, like bone, have collagen fibers that possess a piezoelectric property) and converted them into flexible bio-piezoelectric nanogenerators (BPNG).
How much power does this device produce? Repeatedly touching the BPNG produced enough current to light up 50 blue LED lights – that’s roughly over 230 volts. The great things about the BPNG is that it’s biodegradable, can be manufactured in one step, can be used for a variety of applications, and comes from a plentiful waste product. There’s probably no fishy odor, either.
It’s like Star Trek technology come to life!
The Power of Your Body Heat
If you’ve ever glanced through AdaFruit’s wearables section you already know this technology has been active for a while — especially for military applications. Powering these devices is another matter. The little generators use piezoelectric effect, but this requires you to be moving. If you need more power, either you need to carry more batteries, or you need to move around more. And unless you’re extra fidgety, the average adult working in an office doesn’t move that much.
Human bodies, however, continually give off lots of heat (even when sitting in a desk chair). Harness it, and you’ve got a constant, reliable source of power. A thermoelectric generator (TEG) does just that: it converts heat directly into electricity by harnessing the temperature difference between the wearer’s skin and the air around them.
Called the Seebeck effect, it works when a circuit is made of two different metals and one part is heated. The heated end will have excited electrons rushing towards the cooler end, while the cooler electrons will wander towards the heated end. In order to make a TEG work efficiently, it needs to be made of the right kind of materials, balance the temperature differential, and put out a useful amount of electricity.
More science fiction, right? Wrong.
Researchers at North Carolina State University (NCSU) have created a new wearable a TEG that’s lightweight, comfortable, and can produce electricity efficiently. This small, thin self-adhesive patch, less than a quarter inch square, works by using a polymer that retains heat and then passes it into the TEG. These are then Embedded into a t-shirt that can generate six microwatts per square centimeter. Further research created more power by placing the TEG on an arm band which hit 20 microwatts per square centimeter.
Peeking in Pandora’s Box
Spent nuclear fuel rods are so dangerous that they must be sealed against the outside and their condition monitored. The problem is that, once they’re sealed inside their metal and concrete storage tubes, you can’t actually monitor them very well. And you just can’t insert cables or electronics, the radiation will destroy it.
So, how exactly can we check on the status of those fuel rods to ensure they’re not harming us or the environment?
Lei Zuo, associate professor of mechanical engineering at Virginia Tech, has devised a system that would take advantage of the radiation in the storage tubes to power ultrasound sensor equipment that monitors the contents and the environment. The goal is to insert a tungsten plate to act as a thermal target. Relying again on the Seebeck effect, the plate will use the thermal difference between itself and the outside of the metal tube’s wall to power the sensors. Since there’s no external power requirement, the monitoring sensors could last decades.
Professor Zou is no stranger to energy harvesting. This past August he was awarded a grant by the US Army to develop an energy harvesting backpack.
Do you have any leads on new energy technology you want to see us discuss in future installments of the Direct Energy Buzz? Share with us in the comments!