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Energous and FCC Approval for Mid Range Device - What Does It Mean?

Six months ago wireless power company Energous claimed they'd have FCC approval for their at-distance charging, and I was highly skepti...

Wednesday, December 27, 2017

Energous and FCC Approval for Mid Range Device - What Does It Mean?

Six months ago wireless power company Energous claimed they'd have FCC approval for their at-distance charging, and I was highly skeptical of the claim. Yesterday the FCC did approve their mid-range device under Part 18 - the company stock price doubles, doubters are proved wrong, and the sky is the limit for Energous. I was so wrong, I'm here to apologize and beg for everyone's forgiveness as to my stupidity.

Yeah, right, of course I'm not. I'll do a quick analysis below (next day thoughts were added here) as to what has happened but it's essentially this - Energous have done what they did with the Watt-up Mini, which is to have done the bare minimum to get an approval on a essentially pointless and impractical device that doesn't actually charge at a noticeable rate, but that turns the charge light on, and as it's such a technically complex issue very few people understand what it means, see "FCC Approval", and that's it.

Energous press release is here, the conference call is here. (Skip to 19 minutes for Q&A). You can read my many Energous posts here, but the one on FCC approval in particular is here. The key quote was:

So, basically, unless they either get the FCC to change the rules, in opposition to a vast entrenched business interest and wreck WiFi for everyone, or reduce their power output to the point where it is an utterly pointless product, then I just don't see FCC approval for their devices.

And this is what's happened as far as I can see - they've put out a useless device hobbled to meet FCC guidelines for part 18, and it seems most people are dumb enough to fall for this. Part 18 rules can be found here.

While I'm still reading through and analyzing the FCC reports, here's a summary of my opinion of this 'product':

  • Fails to charge a phone with a measly 100 mW at best (about 10x lower than needed)
  • Unsafe for humans or animals closer than 50cm
  • Highly inefficient, around 99% loss
  • Weak safety measures to limit unsafe exposure
  • Incompatible with previous products as claimed earlier
  • Obtrusive impractical transmitter
  • Small useful area of operation
  • Very limited ability to steer the beam
  • Huge "pockets" of energy about 50cm in diameter

The product
Energous have two approvals for the devices in the FCC database, one at 913 MHz and the other at 2.4 GHz. I assume the 2.4GHz approval is because they use the 2.4GHz range for communication with the receiver, not for power transfer. The previous Watt-up Mini operated at 5.8GHz so unless another approval appears soon, there is no interoperability with their previous devices, as they had claimed.

The device itself is a curved bar, certainly not flat and unobtrusive. It would be very hard to place on the wall, or anywhere in a room without becoming an obstacle. Why curved? Well I'd guess it simplifies the beamforming so they can create as tight a focus as possible and maximize the power transfer at the expense of steering. As they have only 12 antenna in the bar, it would be unlikely that they would have fine control over beam steering anyway.

As the transmitter is a bar it's a pretty limited area that can be irradiated - about +/-45 degree up and down, and +/-30 degrees side to side. At the 90 cm mark that means a region about 2 meters up and down, and 1 meter side to side - a pretty small and inconvenient target area, and that's the biggest it gets. Previous claims of charging Internet of Things devices all around your room aren't supported by this arrangement.

Why 913 MHz? I assume the FCC just said no to them putting huge amounts of power out in the wifi range and stopping that from working, so given allowable bands it was that or 24 GHz.

While not stated explicitly, it appears that the system won't charge if there is any movement within 50cm, so it may be that there's a minimum distance over which it will charge. This needs clarification.

The 'pocket'
Energous have always talked of how they create 'pockets' of energy - which is marketing spin as the laws of physics prevent such pockets being arbitrarily small. The larger the transmitter and more elements it has the smaller the focus, down to a limit set by the wavelength of the energy. The power is to be transferred at 913 MHz, which is a 33 cm wavelength, and that's about as low as you would expect - a 'pocket' that is a sphere 30cm in diameter, about the size of your head. This is backed up by their FCC test data, you can see here that the half power points (-3dB) make it about 50cm across.

As you can see in the image below, depending on how the beam is 'steered' you don't get a "pocket" as much as a "smear" - have your phone on one side, but power is definitely going elsewhere. The image below from the FCC

The safety measures
To meet the FCC guidelines, Energous had to implement a number of safety features which prevent the system from working when anyone is in the field of operation. Basically, it appears the amount of power a person would absorb would be illegal and unsafe so there are motion detectors that switch the system off if movement is detected within 50cm of the transmitter - which is, to me, a shockingly weak safety system.

This is one of the frustrations of dealing with amateurs when it comes to safety. You don't build safety systems based solely on common use cases, you think of all the edge cases because customers are annoying that way and will do things you never imagined with your product. Things also change when you aim a product at millions of users - tests on even tens or hundreds of thousands of cases simply won't show up what happens in the field. If you have a product that can't cause harm then there's no issue other than annoyance, but with real health implications like transmitted RF power, there are serious consequences to failures. Quite how their sensing system deals with a sleeping person, pet, or child I'm not sure, I see it as a major flaw. These flaws are easy to see and it's an accident and a lawsuit waiting to happen - another reason I don't ever expect to see this as a real product.

The power
Here we get to the juicy part - how much power will it transmit? Well with around 12 antenna each at around 0.8 W, the total power it can send out is around 10 Watts. Fantastic, right? Well that's not what is received at the target - looking at those numbers and using the Friis equation, (and some estimation, not enough data to be 100% sure) we get around 100 mW at 0.5 meters, and around 30 mW at 0.9m. A phone will need somewhere between 500 mW and 1000 mW to really start charging and be useful, so the power sent is essentially enough to switch the charge light on, and not much more. To even match their rather wimpy Watt-up Mini they'd need to improve it by 10x.

That has to be wrong? It has to send more than that! Well, when asked in the conference call as to the power sent the CEO replied that the power is "not that significant" and dodged the question.

The efficiency
10 Watts transmitted, and 100 mW received gives around 1% efficiency. 99% of the energy is lost as heat, which granted isn't too much, but essentially you've created a very expensive method of mildly warming a small part of your room, and failing to actually charge your phone in the process. This is a generous estimate as well, it does not account for the loss from the wall socket to antenna emission, so that 1% efficiency is a ceiling and goes down from there.

The conference call
The conference call was as expected - very little actual data and dodging of the few limited questions that were asked. The CEO makes clear the power received is minimal and doesn't want to give that number it's so bad. They instead stress that this is an new door that is open and it's all up from here, and give vague comments of partners selling devices in the future. Talk of useful power is deliberately downplayed. Brilliant marketing and bamboozlement of a non-technical audience. Once again, Energous show their genius in extending this run - they'll no doubt be issuing stock or some other form of capital raise to keep paying those executives that ~$5 million a year.

Stock price
The stock price is up near 100% today, back to where it was in early summer - but surprisingly not higher. Shouldn't it be trading above that now it has FCC "approval"? Let's give it time to see.

Any big name customers? Can we expect Apple to be buying them up? Well, IMHO, Apple isn't dumb, and neither are any other big guy. This is going to be the unsavvy public putting in money again and again on the hopes of a big win. I don't expect to change their mind, at this point it's near a religion to many, and all I'm doing is pointing out the obvious.

The roller coaster ride just keeps going...

I wrote four more posts on Energous in the subsequent 5 days, you can find them here, here, here, and here.


  1. Ur so much smarter than the FCC. Calling Trump. Will put you and kushner in charge

    1. I assume you are being sarcastic. Could you point to the places in this post where I am in error? I'd like to know and will correct accordingly.

      Otherwise, comparing me to Kushner might just be the worst insult I've had in a long time...

  2. I may have missed it, but do you have a direct link to the FCC approval and its supporting documentation? My Google-fu may not be the best but as far as I can see this is a press release by Energous, not a formal approval.

    1. Sorry, found it https://apps.fcc.gov/oetcf/eas/reports/ViewExhibitReport.cfm?mode=Exhibits&RequestTimeout=500&calledFromFrame=N&application_id=B6rKOmC6QGs13hWdV%2FM5%2Fg%3D%3D&fcc_id=2ADNG-MS300

    2. Yes, that's it. It is available in the link within the text above, same as for their 2.4GHz approval for the communication component.

  3. This is how you go about legally robbing stupid people. I can make millions this way but I wouldn't able to live with myself.

  4. Wireless power is and never will be practical or safe at any usable power level, period. You can pretend all you want. Or radiate yourself until you are sterile your choice. None for me.

    1. Just checking, but you do understand that I'm pointing out the ridiculousness of the Energous claims, right? Sarcasm doesn't always translate well in text...

    2. I'm pretty sure the same "can't be done" arguments were made about the telephone and television.

    3. This is not how science is done. Someone does not get to make a ridiculous claim then demand everyone prove them wrong. If their claims are beyond what science currently shows is possible, then the onus is on them to prove it is, not the other way around.

      Energous are making the ridiculous claims, not me. Burden of proof is on them. In fact, they've made multiple claims over the years they have failed to live up to, on delivery dates as well as performance.

      What data Energous have shown, especially with the FCC data they were forced to make public, has proven what the skeptical among us have been saying all along.

      And since you're "pretty sure" that such arguments were used with TV and telephone, perhaps you can provide us with some valid references to that? If not, please don't go making such claims.

  5. Technically smart?...maybe. However, I believe where he stated (multiple times) "Energous have" should be Energous "has."

  6. Christyna. Thanks for your comments. I prefer to have an actual debate and discussion on the topics, perhaps a criticism of my assumptions, or I've used an incorrect simplification, or my maths is wrong. Since you don't engage me there, I assume you agree with what I wrote?

    You are picking on the minor point in my grammar. When it comes to whether a company name is a collective noun or a singular entity for use of 'has' or 'have' then for American English you are correct, singular is the preferred choice. Here's the unfortunate thing - I'm British and American, and I occasionally switch back and forth between the two. Check the link below for a further demonstration.

    If that's the best argument you can come up with for why I'm not worth listening to, then I'm pretty pleased.


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