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Thursday, July 19, 2018

Energous: It's Worse Than We Thought

A contributor to SeekingAlpha has recently posted an article highlighting data from an FOIA request to the FCC regarding Energous' approval for their mid-range transmitter last December. They appear to show concern from the FCC officials as to how the system was performing, and understanding the system behavior. There's also discussion regarding the safety limits, which I think are one of the key issues and concerns surrounding this approval, and covered them in several posts. The author has provided the FOIA documents for download here.

For some background, I wrote several posts on the FCC approval in December last year, you can find them starting here.

Interestingly, earlier this year I did a FOIA request for all of FCC Chairman Ajit Pai's communications regarding Energous (along with several other keywords) and was told there was nothing. Given Ajit Pai's (IMO clearly illegal) use of the official FCC communications to promote a private company, I suspect there are documents there, just not available. I may revisit that.

One of the key images that has been redacted from the FCC report, but is floating around from another source, shows the actual specifications for their desktop system.


There are some key points in here:
  • The system works for only 1 receiver at a time
  • Output is from 12 antenna, each antenna is 1.8W (32.5 dBm) - 21.6 Watts total output
  • Receive power at 30cm is 190 mW, at 1m is 60mW
  • Max range 1 meter
  • Receiver is 6.5 cm in diameter
  • No mention of safety limit distance
There is no clear detail is that received power is actual RF power at target, or power to battery at target - I suspect the former. This is a higher output power than the system shown in FCC documents in the Part 18 Approval (21.6W vs 10W), and the receive power slightly lower - I was estimating 100 to 150 mW at 50 cm, some were estimating higher. That implies a "Wall to Battery" efficiency of 0.2% at 30cm and 0.06% at 1 meter, assuming 90 Watts in at the wall socket (thanks to a reader for pointing out my initial mistake here). That would mean a phone would take over a day to charge at 30 centimeters, and nearly 4 days at 1 meter - and that's assuming 100% efficiency on receive, and I also suspect those numbers are ideal and real world will be worse. You might say it's more appropriate for IoT or small item charging, however the receiver, at 6.5cm diameter, is wider than my phone. I expect it's multiple dipole antenna and they need it that size to get even that terrible efficiency. I can see why Myant didn't want this receiver in their underwear.

So charge times are obscenely long, it's incredibly inefficient, only one target receiver at a time, the receiver is larger than a phone, and it needs a safety cutoff if you get too close. Did I miss anything? 

Apple must be chomping at the bit to get hold of this technology...

I'll dig into the released documents in more detail later, but at first glance it doesn't quite match with prior statements from the Energous CEO as to system capabilities.

"Here is a brief summary of the results of the amount of actual power delivered to a device at varying distances with a single WattUp transmitter. Power received at zero to five feet measured 5.55 watts compared to our targeted performance of 4 watts. Power received at five to 10 feet measured 3.74 watts compared to our targeted performance of 2 watts and power received at 10 to 15 feet measured 1.06 watts compared to our targeted performance of 1 watt."

5.5 Watts vs an actual 0.19W - only a factor of around 29. Remember that when viewing the statements from at-distance wireless power companies as to their performance specs, compared to what they have to write in the legally required documents and spec sheets.

There's an update to this post, reading the releases in more detail, here.

(Since I always seem to need say this - I have no financial position, short or long, in Energous or any related company)

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