Welcome to the Technology Buzz for March, 2017! This month, we take a peek into the murky truth of urine batteries, learn about a new FM radio trick that blasts data to your smart phone via posters or clothing, and we’ll see how the Doppler radar, used to track storms, is helping forecast falling accidents by seniors weeks in advance.
Wasted Effort? Can Human Urine Be Used For Power?
Bad jokes aside, it’s long been known that human urine can conduct electricity and for that matter, experimenters have also long had a certain fascination with using urine for generating electricity. And why not? While the stuff is mostly water, the largest fraction is urea (CH4N2O ), followed by much smaller amounts of chlorides, sodium, potassium, and sulfur (to name just a few).
But apart from the fact that NASA examined the properties of urine in the years leading up to the SkyLab space station, there doesn’t seem to have been a lot researchers interested in that kind of project. However, with energy needs increasing world-wide, that seems to have since changed.
Back in 2012, a story from Maker Faire Africa came out about four young women in Nigeria who were using urine to power a generator. Unfortunately, the headlines was ill worded. Urine was only used as a water source to create hydrogen which in turn fueled an electric generator. In fact, even though extracting hydrogen from urea is easier than getting it from water, this system actually consumed more energy than it produced. Still, that it worked at all showed that in arid locations, hydrogen could be successfully harvested from less than ideal sources.
Fast forward to July, 2016, where researchers at the University of the West of England created a bacteria battery, or “microbial fuel cell”, that worked by having little organisms feed on urine to produce electrons. Currently, a stack of six fuel cells put out about 2.5 volts and is used to charge a cell phone for 6 hours.
As it turns out, the secret to making electricity from urine lies in separating out the urea and then using the urea as an electrolyte in a battery. The trick was to find the right kind electrodes for such a battery to work.
Recently Stanford chemistry Professor Hongjie Dai and doctoral candidate Michael Angell discovered that by using aluminum and graphite electrodes, they could produce a battery that could charge rapidly and also cycle through charge/discharge cycles thousands of times. Known now in the research literature as an aluminum-ion battery, it is made with some of the cheapest and most abundant materials you can find on Earth —urea, aluminum, and graphite. Each cell charges in 45 minutes to roughly 1.73 volts and though the capacity (mAh) is currently low when compared to Li-ion batteries, the cell can be cycled twice as long as Li-ion, about 1,500 times. Like Li-ion, it also has a high Coulombic efficiency (how much charge exits the battery per unit of charge taken during charging) of 99.7%. Most important of all — none of the components are flammable.
Dr. Dai believes the aluminum-ion battery is just the thing for utility scale grid batteries: highly efficient, long life from inexpensive materials, that are both safe and eco-friendly. Commercial development is underway.
Clothing and Posters Go On the Air
American cities are deluged with all kinds of radio signals, including FM radio stations. FM radio stations broadcast their signals at hundred kilowatts on one of the 100 FM channels between 88.1 to 108.1 MHz. With the right antenna and equipment, all that energy can be harvested right out the air and used to broadcast data without the need for additional power supplies or batteries.
The technique is called “ambient backscattering” because it takes advantage of ambient radio signalsto convert the signals to energy and then reflect a new signal with encoded data. A few weeks ago, a group of University of Washington students demonstrated how ambient backscattering could be used to create smart cities where information about concerts, traffic crossings, perhaps even parking information could be broadcast to activated FM receivers in smart phones (sorry but not iPhone) and FM receivers in carswithout the need for conventional power supplies. Since the system uses just a few microwatts, the range is only a few feet and they also don’t have an effect on the original radio signals. The students also created a smart shirt complete with an antenna custom-stitched with metallic thread into the shirt so that it could transmit data from bio metric sensors to a smart phone without the use of batteries.
Caught By Radar, Safely
For the elderly, falling is a real danger that can result in broken bones, head injuries, even death. One out of four older people falls each year, one out of five falls cause a serious injury. As boomers age, both the potential danger for accidents and the increasing costs to treat injuries are driving researchers to look more closely at the causes behind falls in seniors. A few months ago, a combined research project by the Sinclair School of Nursing and the College of Engineering at the University of Missouri were able to identify ow changes to walking gait can contribute to the potential for an individual to fall.
The project involved setting up Doppler radar devices were placed in non-intrusive boxes in some of the resident’s homes at an independent senior living community. Doppler radar was used because it measures velocity and in this case, researchers wanted to track the speed of subjects’ walking gait patterns. By studying images made by the data, the researchers were able to predict how changes in an individual’s gait, such as stride length, speed, and frequency, could result in a fall. The system also created email alerts for nurses when irregular motion was detected.
Changes in gait by as little as 5 centimeters per second were associated with an 86.3% probability of falling within the following three weeks. Shortened stride lengths were also associated with falls within the three week period by 50.6%. By intercepting falls before they happened and getting the person to see a doctor sooner, the senior is able to live independently longer and in better health.