This Power-Generating Shoe Isn’t Ready for Prime Time Yet, but This Kid’s Project is Still Pretty Cool

This is a video by a Angelo Casimiro, a 15-year-old Filipino participating in this year’s Google science fair. And he has seriously tweaked his shoes to do something cool: they spark. And I don’t mean spark like  those kids’ shoes that have stripes that dimly light as you walk that you really wanted to try but evidently you couldn’t wear because none of them could support your ankles (okay, that last part may not have applied to everyone else…). Angelo’s new shoes actually generate a little bit of electricity each time he takes a step. This is incredibly cool.

But just because I can, I’m going to bury the lede for a bit, because I want to contextualize this. Angelo did this as a test to see if it could work AT ALL, and he says he’s nowhere near a final product that you might buy. So before dreams of daily jogging to power your iPhone and laptop dance in your head, we need to look at the electricity we can create and how much we actually use.

Duracell’s basic alkaline non-renewable AA battery has a charge of about 2500-3000 miliampere-hours (mAh), which I estimated based on multiplying the number of hours it was used by the constant currents applied in the graphs on the first page here. The two basic rechargeable NiMH AA batteries have charges of 1700 and 2450 mAh. The battery in my Android smartphone has a charge of 1750 mAh, based on dividing the energy (6.48 watt-hours) by its operating voltage (3.7 V). Based on Angelo’s best reported current of 11 mA on his Google science fair page, it would take 159 hours to fully charge my phone. That’s nearly a week of non-stop running! (Literally! There’s only 168 hours in a week. You could only spend 9 hours doing anything besides running that week if you wanted to charge the phone, or replace one of the two AA batteries it takes to power my digital camera) However, I might be overestimating based on his averages. At around the 3:50 mark in the video, an annotation says that Angelo was able to charge a 400 mAh battery after 8 hours of jogging. That would translate to about 33 hours of jogging to charge my cell phone. No one I know would want to do that, but that is significantly less than jogging non-stop for almost 7 days.

But as Angelo points out, while you not be able to power your phone with his shoe, lots of sensors and gadgets that could go into smart clothes could be powered by this. In the video, he says he was able to power an Arduino board. An Arduino is a common mini-CPU board with extras people often use to make nifty devices, from how Peter Parker locks his room door in The Amazing Spider-Man movie to laser harps you can play by touching beams of light (note that the Arduino isn’t necessarily powering all the other components it is controlling in these cases), so you could potentially control smart clothes that respond to your moving.  A study by MIT’s Media Lab also looked at putting piezoelectric material in shoes and found they could power an RFID transmitter, which can be used to broadcast information to either devices. So perhaps your gym shoes could also act as your gym ID. The 400 mAh battery Angelo mentions is pretty close to the charge of batteries in small blood sugar monitors and over double the charge of some smaller hearing aid batteries.

But in relation to another recent science fair controversy, let’s put Angelo in context. No, he did not “invent” a new way to “charge your phone with your shoes“. Angelo himself points out that his work is more like a proof of concept than anything close to a product, and his numbers show you really won’t want to charge energy heavy devices with it. And MIT and DARPA, that branch of the US Department of Defense that funds crazy research schemes, have both looked at similar systems. (DARPA has looked at piezo-boots that could help power soldiers’ electronics.) Angelo and DARPA also both realize the limits of this: with our current materials, there’s only so much you can stuff into footwear before you run out of room or make it harder to walk. So instead, people have shifted to different goals for piezoelectricity: instead of having the material move with a single person who has to provide all the energy, we can place it where we know lots of people will walk and split the work. In Europe, high foot traffic areas have been covered with piezoelectric sidewalks to power lights, and in Japan, commuters walking through turnstiles in Tokyo and Shibuya stations help power ticket readers and the signboards that guide them to their trains.

Two distinct images. The left image shows a turnstile for ticketing. There is a black strip of material running through it. The right image shows a figure with an explanation in Japanese describing the power-generating nature of the strip.

Piezoelectric strip in ticket turnstile in Japanese subway station, from 2008

But none of this means that Angelo hasn’t done good technical work. It’s just that his effort falls more on the engineering side than the science side. Which is perfectly fine, because Google has categories for electronics and inventions and that other big science fair everyone talks about is technically a science AND engineering fair. Angelo’s shoe modification is posted on instructables and is something you could do in your home with consumer materials. The MIT Media Lab study still worked with custom-made piezoelectrics from colleagues in another lab. So the fact that Angelo could still manage to charge a battery in a reasonable (if you don’t need power right away) amount of time is incredibly impressive. And he also seems quite skilled at designing the circuits he used. As a 15 year old, he easily seems to know more about the various aspects of his circuit he needs to consider than I did through most of my time in college (granted, you didn’t need to know any particularly complicated circuity to be a physic majors). He’s definitely on to a great start if he wants to study engineering or science in college.

Making Fuel Out of Seawater Is Only One Part of An Energy Solution

So I recently saw this post about a recent breakthrough the Navy made in producing fuel from water make a small round on Facebook from questionable “alternative news” site Addicting Info and it kind of set off my BS detector. First, because this story is a few months old. It actually turned out the article was from April, so part of my skepticism was unfounded. But the opening claim that this wasn’t being reported much in mainstream outlets is wrong, as several sites beat them to the punch (even FOX NEWS! Which would probably make Addicting Info’s head explode.). The other thing that struck me as odd was how the Addicting Info piece seemed to think this technology is practically ready to use right now.  That surprised me, because for nearly the last two years, my graduate research at UVA has been focused on developing materials that could help produce fuel from CO2.

This Vice article does a pretty good job of debunking the overzealous claims made by the Addicting Info piece and others like it. As Vice points out, you need electricity to make hydrogen from water. Water is pretty chemically stable in most of our everyday lives. The only way the average person ends up splitting water is if they have metal rusting, which would be a really slow way to generate hydrogen, or by putting a larger battery in water for one of those home electrolysis experiments.

The Naval Research Lab seems kind of unique among the groups looking at making fuel from CO2 in that they’re extracting hydrogen and CO2 from water as separate processes from the step where they are combined into hydrocarbons. Most of the other research in this area looks at having metal electrodes help this reaction in water (nearly any metal from the middle of the periodic table can split CO2 with enough of a negative charge) . Because of water’s previously mentioned stability, they often add a chemical that can more easily give up hydrogen. A lot of groups use potassium bicarbonate, a close relative of baking soda that has potassium instead of sodium, to help improve the conductivity of the water and because the bicarbonate ion really easily gives up hydrogen. In these set-ups, the goal is for the electricity to help the metal break off an oxygen from a CO2 to make CO, and when you get enough CO, start adding hydrogen to the molecules and linking them together.

A chemical diagram shows a CO2 molecule losing a carbon atom on a copper surface to make CO. When another CO is nearby, the two carbon atoms link together.

Carbon atoms are initially removed from CO2 molecules on a copper surface, forming CO. When CO get close to each other, they can bond together. From Gattrell, Gupta, and Co.

But basically, no matter what reaction you do, if you want to make a hydrocarbon from CO2, you need to use electricity, either to isolate hydrogen or cause the CO2 to become chemically active. As the Vice article points out, this is still perfectly useful for the Navy, because ships with nuclear reactors continually generate large amounts of electricity, but fuel for aircraft must be replenished. If you’re on land, unless you’re part of the 30% of the US that gets electricity from renewable sources or nuclear plants, you’re kind of defeating the point. Chemical reactions and industrial processes always waste some energy, so burning a fossil fuel, which emits CO2, to make electricity that would then be used to turn CO2 back into fuel would always end up with you emitting more CO2 than you started with.

However, this process (or one like it) could actually be useful in a solar or wind-based electricity grid. Wind and solar power can be sporadic; obviously, any solar grid must somehow deal with the fact that night exists, and both wind and solar power can be interrupted by the weather. (Nuclear power doesn’t have this issue, so this set-up would be irrelevant.) However, it’s also possible for solar and wind to temporarily generate more electricity than customers are using at the time. The extra electricity can be used to power this CO2-to-fuel reaction, and the fuel can be burned to provide extra power when the solar or wind plants can’t generate enough electricity on their own. This is also where the Vice article misses something important. Jet fuel can’t have methane, but methane is basically the main component of natural gas, which is burned to provide about another 30% of electricity generated in the US today. And because methane is a small molecule (one carbon atom, four hydrogen atoms) it can be easier to make than the long hydrocarbons needed for jet fuel.

Also, one thing I’m surprised I never see come up when talking about this is using this for long-term human space exploration as a way to prevent to maintain a breathable atmosphere for astronauts and to build materials. If you can build-up the carbon chains for jet fuel, you could also make the precursors to lots of plastics. The International Space Station is entirely powered by solar panels, and solar panels are typically envisioned as being part of space colonies. Generally, electricity generation shouldn’t be a major problem in any of the manned missions we’re looking at for the near future and this could be a major way to help future astronauts or space colonists generate the raw materials they need and maintain their environment.

If you want to read more about the Naval Research Lab’s processes, here are some of the journal articles they have published lately:

If Only Billy Mays Were Still Around

There’s been a bit of a buzz in battery research lately as chemists have made great strides in truly powering life by the “air you breathe“.  What on earth does that mean aside from being a pointless reference to infomercials I’m obsessed with?  (Aside:  This is actually a problem, I once watched the full half-hour Magic Bullet infomercial because I was bored).  While my previous post talked about researchers redoing a battery idea of Edison’s, this team at the University of Southern California was tinkering with a more  recent design:  “breathing batteries”.  Breathing batteries are basically powered by the rusting of iron by oxygen, though it seems the “breathing” is a bit of a misnomer since the journal article mentions the chemical reactions occurring in liquid (although a lot of literature still uses the term “air”).

Iron rusting actually produces a lot of energy.  If you’ve ever had one of those disposable hand warmers, odds are it was mostly filled with just iron filings and a few other chemicals to speed up the reaction.  But all the heat is coming from the iron corroding REALLY fast.  Iron-air batteries have been around for decades and became very popular during the 1970s energy crisis.  But like the Edison batteries, they fell out of favor when other battery chemistries proved to be more efficient.  Aside from oxygen rusting the iron, there’s a second reaction in the battery that takes charging current and produces hydrogen, and this could take up to half of the energy.  They’ve come back into vogue for similar reasons to the iron-nickel batteries:  the materials are abundant (and cheaper) and safe for both people and the environment.  The Department of Energy hopes improving their efficiency could make for reasonable energy storage in a shift to a renewable energy power grid.

Fine iron particles in the USC battery. Everything looks pretty under electron microscopy.


So what made the USC batteries so much better than before?  Pepto-Bismol.  Seriously.  The active ingredient of Pepto-Bismol, bismuth sulfide, was added to the iron electrode. The bismuth prevented hydrogen formation, and reduced the energy loss to only 4%.  It also helped improve how much energy the battery could hold and how quickly the energy could be released, both of which are important factors for storing energy meant for the power grid.

Thomas Edison Strikes Again

Chemists at Stanford have helped bring a battery designed by Thomas Edison into the modern age.  Like us, Edison was also interested in electric cars, and in 1901 he developed a iron-nickel battery.  In a case of buzzwords being right for a reason, the Stanford team used the same elements as Edison, but structured them on the nanoscale.  Edison’s original design sounds like it was essentially just one alloy of iron and carbon for one electrode and one of nickel and carbon for the other electrode.  The new battery consisted of small iron pieces grown on top of graphene (that wonderful form of carbon we’ve talked about before) for the first electrode and small nickel regions grown on top of “tubes” of carbon (which probably means nanotubes).

The new battery is 1000 times more efficient than traditional nickel-iron batteries, but the improvement means it only now is about equal to the energy storage and discharge abilities of our modern lithium ion batteries.  Although there’s lot of research being done on improving our lithium ion batteries, there are some unique advantages to the nickel-iron batteries.  For one, there’s a lot more iron and nickel than lithium, meaning the batteries could be cheaper.  Nickel-iron batteries also don’t contain any flammable materials, while lithium batteries are capable of exploding.  While the nickel-iron batteries might not appear everywhere, their inability to explode could be a boon to electric car manufacturers.