Since man first learned to harness and use the electron, there has been a constant struggle to find new and more efficient ways to generate electric power. The Greeks rubbed animal hides against amber (as they called it ἤλεκτρον or ēlektron) while much later, European scientists devised the electrostatic generator and Leyden jar. While these discoveries and technologies are elegant exploitations of the laws of physics (and great for entry-level electrical science courses), they were ultimately too inefficient to provide any real benefit to society.
As a result, we typically generate electricity by spinning the wheel of an electromagnetic generator whether it be by burning coal, damming a river, or digging a very deep hole in the ground. We have also made major efficiency gains in our use of this power. LED bulbs use less power than incandescents, and today’s smartphones can perform calculations millions of times faster than yesterday’s vacuum tubes using a fraction of the energy.
Some recent efforts have tried to combine these two themes by taking what was once a wasteful byproduct and turning it into an energy source making an entire process more efficient. Hybrid and electric vehicles use regenerative braking where a car’s kinetic energy is captured and converted back into electric energy during stops, and in some gasoline cars, a turbocharger will use exhaust to compress the air going to the engine causing it to deliver more power more efficiently.
There are always a trade-offs though. The methods used to capture waste energy are usually highly inefficient, so you need to seek out a large source of waste to make it worthwhile. Sure, your breathing could be used to spin a turbine and a bodybuilder could be hooked to a generator instead of a weight machine, but the amount of energy created these ways compared to the cost and complexity associated with capturing that energy make them ultimately useless.
So let’s talk about Ampy and Juse.
If the crowdfunding scene is any indication, mankind’s biggest struggle after death, disease, and male pattern baldness is the small size of smartphone batteries. We’ve already covered Zendure, Ark, Hydrobee, and LockedUSB which all claim to help charge your phone faster or keep it charged longer. The funds raised are an obvious indicator of how pertinent of a problem this is, and the diversity of solutions indicates how open the market is for a good solution. Nobody seems to have the problem totally nailed down.
Juse and Ampy are two more attempts to keep your phone charged by generating energy from every day tasks that you already perform. Juse is a smartphone case with an integrated solar cell that claims to generate energy even in indoor lighting conditions while Ampy contains some kind of proprietary inductor technology that can capture energy from the user’s normal motion. Before evaluating either of these devices, it’s important to first understand the size of the problem they are trying to solve.
How big is a phone battery?
So how much energy does a phone’s battery store anyway? While this number will obviously vary from model to model and decrease over time as a phone’s battery wears out, here’s a table of a few popular phone models with their stated battery capacities (information provided by GSMArena) that should help give an idea:
|iPhone 6 Plus||2915mAh|
|Samsung Galaxy S4||2600mAh|
|Samsung Galaxy S5||2800mAh|
A “mAh” is a milliamp-hour, and while not technically a unit of energy, when multiplied by the standard 3.7 volts of a lithium polymer battery, the result can be directly converted into Joules which are. 1000mAh at 3.7V works out to 13,300 Joules. To give you an idea, this is the amount of energy required to lift a 50 pound weight to the top of a six story building. Of course, actually performing such a task won’t be 100% efficient, so it will take more energy once you take friction and other losses into account.
I’m sure most reasonably fit people could generate that much energy in a matter of minutes, but not without at least breaking a sweat. So how are our two contenders managing?
How does it work?
Ampy has been extremely vague about how they plan to generate energy from a user’s motion. The idea of capturing energy from motion brings up images of shakeable flashlights on late-night TV commercials, but these devices typically don’t get much brighter than a cheap keychain flashlight and require an awful lot of shaking to keep them going.
Shaking one of these flashlights moves a magnet past a coil of wire (inductor) which, thanks to Faraday’s Law, induces an electric charge. This is more or less how the turbine in a power plant works except in a straight line instead of a rotating shaft. Now, these flashlights require a pretty substantial amount of work to generate a pittance of energy, so it’s no wonder Ampy has adamantly stated that their technology is better:
Thanks to the proprietary “patent pending” nature of their technology, I can’t know for sure exactly what they’re doing, but there are some clues in their video that might help.
In one scene of their ad, the three product creators are standing around a whiteboard presumably discussing the inner workings of their product, and almost everything they’ve scribbled down points to a very similar technology to the shaking flashlight above.
- Full-wave rectifier – A method for converting alternating current into direct current. As the magnet moves through the coil, the current will change directions. This circuit element “rectifies” this so that it only moves in one direction which allows it to be used to charge a battery.
- Rectified sine wave – This is the output you get when you pass a sine wave through a rectifier. The horizontal line may be indicating the average voltage or RMS power of the sine wave, but it’s hard to tell given the inaccurate hand-drawn scale.
- Lithium polymer battery charge profile – Lithium polymer batteries typically operate from a range of 3.0V to 4.2V though they can sometimes dip below 3.0V into “deep discharge”. This graph shows a typical charge of a battery. It is quickly pulled out 2.5V of deep discharge to 3.0V to resume normal current limited charging until the voltage reaches 4.2V where it enters constant voltage mode.
- Faraday’s law – mentioned above. Used to calculate the electricity induced in a coil passed through a changing magnetic field.
- Magnet passing through coil – Looks a lot like the shake flashlight, no?
- Inductor – The circuit element that is apparently providing the alternating current for their rectifier.
- Voltage on coil as magnet passes through – This is the output of a pretty standard physics experiment where you drop a magnet through a coil. As the magnet enters the coil, the field inside the coil gets stronger and induces a voltage in one direction. When it’s inside the coil, the field is constant and produces no voltage, and when it exits the coil, the field gets weaker and produces an opposing voltage. I found a good example of this here.
Now, it’s pretty obvious that this portion of the video is staged. For starters, there is absolutely no reason to ever write up Faraday’s law on a whiteboard outside of a classroom or otherwise academic environment. The multivariable calculus involved can only be solved by hand for very simple situations. Modeling a real life device accurately requires some sort of automation such as a computer model.
The rest of it is just a bunch of vague technobabble meant to look impressive.
If there is any useful information to glean from this whiteboard, it’s that their product probably uses the same sort of electrical technology as a standard shake flashlight. I doubt they would go through the effort of writing all of that on the board if it had nothing to do with their product.
There are a dozen ways to turn AC from an inductor into DC with varying levels of efficiency, so if the Ampy team really has something novel here, it has to be in their inductor technology.
All I can glean from their product page is that these inductors are apparently made from pieces of chalk:
Kidding aside, I have no idea what’s inside those things, but if someone was going to design a super novel patent pending inductor technology, it might be three PHD candidates in the field of material science.
One of the challenges of creating a good inductor for this kind of application is getting a large number wire windings around a core in the smallest amount of space possible. More windings in a smaller space generally means more energy is captured from each motion. There are simple physical limitations you come across as you do this though. Thinner wire is more fragile and harder to work with from a manufacturing standpoint. Likewise, thin wire doesn’t conduct electricity as well as thick wire.
Of course, scientists have worked with structures that are very thin and very small for years. Tejas Shastry from the team for example has done extensive work with carbon nanotubes. If there is any novel element to this design that truly sets it apart from what’s out there now, it’s inside those white rods, and it might involve some very interesting material science.
The first question I ask with any kind of “free energy” device is always “how much energy does it make?” We’ve seen plenty of pie in the sky concepts in the past boasting about unbelievably high yields, but this time we’re lucky that Ampy has an actual prototype.
You’d think that the inclusion of a fully functioning prototype would allow for them to provide an incredibly detailed characterization of its performance, but you’d be wrong:
Hrm. They like to use the unit “hours of use”. A smartphone’s battery life can vary by orders of magnitude depending on how much you use it. So what exactly is an “hour”? Is it an hour of talk time? an hour of standby? gaming?
Now, the amount of energy the Ampy provides is highly variable on how much the user actually moves, so it’s understandable that the team would want to be slightly vague. They don’t want a couch potato to cry foul when their Ampy doesn’t perform as advertised.
That being said, they’ve continued to be very vague even when answering very specific questions:
Why not just say how long it takes to charge its battery? Why not record results in “percentage of battery” instead of “hours of use”? Two weeks after that conversation, they finally released a live demo of their device showing it actually generating power through user motion.
It’s impossible to get solid numbers from this gif, but the readout on the multimeter does help provide a rough order of magnitude. Let’s say that it’s outputting an average of around 20mA of current while the user is running. Heck, let’s be nice and round up to 100mA.
They clarified for me that the current measurement was taken at the battery, so we can assume that all of the inefficiencies of their circuit are already accounted for. At 100mA, it would take over 10 hours of running to fully charge the device’s integrated battery (charging slows down as the battery gets close to full). That battery stores 1000mAh at 3.7V, but getting it into a smartphone requires converting it to 5V for the USB connection and then back down to 3.7V inside the phone. Let’s assume that this whole process is 90% efficient.
That means that 30 minutes of running would produce about 45 milliamp hours worth of energy in the phone’s battery. That is under 2.5% of an iPhone 6 battery. They’re calling that “three hours of use”.
This isn’t the only example of overly ambitious battery life predictions. The screenshot of their iPhone app shows that 2.96 watt hours of energy equates to 12 hours of smartphone battery life:
If this were actually true, it would mean that the phones listed in the table above would get a whopping 24 to 41 hours of use between charges. What’s going on here?
When questioned on their estimates, they provided a little more clarity:
Overlooking the blatant “you’re addicted to technology” shaming coming from a company who aims to help people use their phones more, their method for estimating “use” is unconscionably deceiving. By “three hours of use” they actually mean “30 to 60 minutes of use”. This method of estimation is not mentioned anywhere else in their campaign and it is the lynchpin from which their entire product hangs. They are literally saying that you are “using” your smartphone while it is asleep into your pocket.
Even taking that into account, they’re still being extremely generous with the capabilities of the product they’ve demonstrated; 45mAh still isn’t enough energy to last an entire hour with any reasonable amount of interaction or wireless usage. Even gaining back the other two thirds of every hour, the only way I can reconcile their demonstration with the numbers they’ve provided is if there was something wrong with their lab setup. I challenge them to provide better data.
But even assuming the product works as advertised, is it even a good product?
Is that free energy really free?
The project’s video starts off with:
We put a lot of energy into our days. What if we could get some of that back?
The implication here is that you are wasting some amount of energy every day, and there might be a way to recapture it and put it to use. Later on, there’s this:
As mentioned above, kinetic energy capture is something that electric cars do to make them more efficient. This happens in the form of regenerative braking where the car captures its kinetic energy to recharge its battery. As you might have already figured out, capturing kinetic energy necessarily involves slowing something down. Cars are heavy and we want to slow them down often. People don’t like being slowed down.
So really Ampy isn’t recapturing some amount of wasted energy every day, it’s simply making you work harder to perform the tasks you already perform.
Now, I suppose the idea is that by capturing a small, unnoticeable amount of power over a very long period of time (a week), Ampy is giving you “something for nothing”. In order to really assess that, you would need to know what it feels like to wear an Ampy. At 140 grams, it weighs more than my smartphone, and it’s a little too bulky to comfortably fit under my jeans. I recommend you take some measurements and consider your comfort before backing.
But then the other question is why generate electricity at all? Could it be because of your concern for the environment?
According to CNN, charging your iPhone 6 up every day for a year only consumes a grand total of 3.83 kilowatt-hours of energy. Your phone is already one of the most energy efficient devices you own. There isn’t much to be gained by making that small amount of energy “green.” If you’re really concerned about the environment just drive your car for 15 minutes less per year. It’s the same amount of savings (assuming 25HP engine output into phone charging). This isn’t even taking into account the energy required to manufacture and ship an Ampy to your door or the environmental impact of trashing it or recycling it when it finally wears out.
So maybe you buy an Ampy because you don’t want to get stuck without power. In the video, Co-founder Alex Smith says:
We all had the same problem. Our phones would die before the end of the day.
But Ampy isn’t even advertised to solve that problem. While they do have a few of the specific activity => “hours of use” conversions worked out (using their absurd definition of “use”), the general implication is that the Ampy holds a week’s worth of activity:
If it takes a week to generate half the energy stored in your smartphone, why not just buy a backup battery? Anker has some nice 3200mAh models that charge overnight and can fully charge your phone up every day. And they only weigh 80 grams!
Will it ship?
I think that Ampy will be delivered to backers. In fact, given the prototype, Dragon Innovation stamp of approval, and seven month lead time, I’d even say that it will ship on schedule. To some degree, Ampy works. There is a physical prototype which is more than I can say about half of the projects we review. And hey, maybe the team will be able to improve its performance before shipment.
What I’m worried about is how backer expectations have been managed. Ampy’s usage calculations are misleading, and I think that many backers will be upset when their sweaty 30 minute workout with a brick strapped to their ankle doesn’t even offset the energy used to play music during that time. Their product pitch assumes a very small amount of phone interaction, and the people shopping for Ampy are specifically the kinds of people who use their phone a lot.
Similar to the Carbon wristwatch, Juse claims to use a solar panel integrated into the back of a phone case to passively collect sunlight throughout the day. While the solar panel on Juse is a healthy amount larger than Carbon, there are some other factors in their campaign that don’t add up.
Solar panels come in a number of different shapes and sizes. The most common used today are polycrystalline and monocrystalline. Polycrystalline are the familiar blue panels; they’re typically the cheaper of the two which comes at a cost of efficiency. Monocrystalline are black and are usually cut into octagon shapes. Both of these technologies involve growing crystals of semiconductor materials. You can actually see the crystals in polycrystalline cells, while monocrystalline are exactly that. The entire piece is made from a single contiguous crystal structure.
Crystals are defined as a formation of atoms or molecules in a highly ordered fashion. These atoms form rigid structures of certain geometries. This also makes them inflexible and hard.
So if Juse’s “High efficiency crystalline silicon” is made of some sort of rigid crystal material, how is it curved?
Seriously, it’s not an illusion. Even their 3D cutaway shows a non-flat solar panel.
My guess is that they haven’t yet worked out any of the actual 3D for this device and are currently displaying industrial design concepts. This single fact could draw into question the entire industrial design. If you think Juse would look good on your phone, prepare for it to look different if and when it arrives.
How much power?
Juse claims that their solar panel is rated for 2 watts. Assuming unobstructed sunlight on a clear day (1000W/m^2) and panel dimensions 80% the surface area of an iPhone 6 Plus, a 24% efficient panel will have 2.36 Watts to work with. That gives them enough incident power to meet some of their claims, and it also matches up with their claim that the device can charge its 1550mAh battery to 75% in two hours:
I actually worked out 2 hours 10 minutes, but i’ll let it slide.
Now the iPhone 6 Plus is a pretty big device. These guys also offer models for phones as small as the iPhone 5s. Doing this same calculation with a phone that has 58% of the surface area brings the maximum output to 1.36 Watts. This won’t be enough to charge their battery to 75% in two hours, but then again, how are they going to fit a battery with the same capacity into a case that’s almost half the size?
Again, not a whole lot of thought done here.
Power Management System
Juse claims that their device is more than just a solar panel and battery charger. Their proprietary Power Management System and algorithms will apparently enable it to perform well even in low light.
Well, it also contains some maximum power point tracking hardware from Texas Instruments. Though they don’t say which chip, the diagram from their page points to the BQ25570. They just erased the part number for some reason.
The biggest problem with this part is that it’s designed for very lower power applications and as such won’t be able to keep up with the 2 watts they’re are claiming from their panel. This guy craps out at 0.4W:
And it also kind of upstages them. It’s designed to be an energy harvesting solar panel controller as it can very efficiently pull just the right amount of current from a solar panel to keep it operating at peak efficiency. It even goes a few steps further and includes an integrated battery charge management controller and an integrated step down voltage regulator for the output. Basically, it can charge a battery from a solar panel and then discharge that battery at a fixed voltage to a circuit. While the Juse team will have to add something between this controller and the phone to step up that output to the 5V necessary for charging, one wonders what their fancy Power Management System can possibly do to improve the performance and efficiency of the solar panel. Where is their “MPPT Software” supposed to run?
Even more interesting; an earlier version of the campaign page didn’t include the blurb about Texas Instruments. It was only added after a vigilant DropKicker reader asked about it in a private message to the company. It sounds like their proprietary system isn’t as proprietary as once thought.
Will it ship?
March 2015 is five months away, and they have no prototype. Furthermore, what details they have leaked about their hardware indicate that it will not function as they think it will. I wouldn’t count on them shipping on time.
There are a few things that are pretty interesting about this campaign though. Firstly, despite the fact that they’re utilizing Indiegogo’s new campaign deadline extension feature, the team has limited how many phone cases they’re making available. They only have 1000 cases available, and have filled up their other backing tiers with tshirts and plaques. This is definitely unorthodox for an Indiegogo campaign, but it’s also smart. They’re likely testing the waters and considering market viability, but they don’t want to make themselves liable for an unmanageable number of orders before they have their production locked in. I think Ritot could learn a thing or two from this practice.
The second interesting thing is that someone named Michael Stewart is one of their cofounders. This guy has his name on a boat load of solar related patents and has a ton of other relevant experience that will be useful when designing a solar powered phone case. I’m a little curious about what his level of involvement is in this campaign so far as he obviously would already know about rigid solar panels what took me 10 minutes to google. Considering that the entire campaign at this point is being managed by Tom Lam, whose previous experience includes “High Tech Fashion” and “Reality TV Host”, I would speculate that no part of this project as shown on the page has been run past an engineer or scientist.
This isn’t a huge cause for alarm though. There is a pretty decent amount of energy coming from the sun, and when it’s the size of a 5.5″ smartphone, even an inefficient solar panel can harness a useable amount. The concept of a somewhat useful solar phone case isn’t too outlandish, and given a decent amount of competence, I can see them eventually shipping one.