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I did my PhD on energy harvesting (specially focussing on hostile environments with high temperature or high radiation) around 15 years ago and harvesting from

I did my PhD on energy harvesting (specially focussing on hostile environments with high temperature or high radiation) around 15 years ago and harvesting from stray EM radiation was the holy grail for room temperature stuff where vibrations or heat gradients couldn’t be found. If you’re willing to sacrifice always on connectivity and have a node report in on an infrequent basis then I always figured EM harvesting would be the way to go for most applications since even a tiny amount of energy can build up over time to become a useful amount. I knew I’d gone deep into this world when I started thinking that micro watts was a large amount of power!

zoomablemind 3y ago
Does this sort of harvesting rely upon some internal accumulator like a capacitor before the energy could be fed elsewhere? Also a question if such harvester need its own power source to be able to operate? They cite a super wide range of EM freqs from Hz to MHz, and an efficient antenna...
- simonbarker87 3y ago
  Yes, you need a reservoir to store the charge (energy) which in my case was the limiting factor to deployment in high temperature environments as capacitors get very leaky as temperature increases. Harvesters don’t need their own power supply and ideally the system can come back to life from totally empty (meaning it doesn’t need to be deployed with any charge level) I was doing my thing back before the packaged harvester management chips were available and I made a PIC based microcontroller system that could monitor the charge level in a capacitor fed from a piezoelectric vibration energy harvester and decide when to wake up and transmit a data reading based on the capacitors charge level. The trick was getting the PIC’s sleep current draw low enough that the capacitor was charging even at milli g level vibration levels - from memory you can get a PIC’s sleep current well down in the tens of nano amp range. PICs have a built in voltage reference that is stable (a zener or schotkey diode from memory of 0.6V?) and a way to read what the Vsupply (basically the capacitor) is compared to it. So the PIC would wake up every 30 seconds, check Vsupply to the built in reference and, when high enough fully wake up, take and transmit a reading and go back to sleep. From memory I got it running at 50mg transmitting every few minutes. I got a nice journal publication in IEEE for that work.
  - zoomablemind 3y ago
    Cool project. Thanks for sharing the details! So the harvester sustains itself, keeps filling up the bucket, and periodically reports out the progress. I guess it's a balancing game, as the filling up process is probably slow, so the target's draw needs to be low too.
    - simonbarker87 3y ago
      Thanks, it didn’t report back progress of charging, it was connected to a sensor (light sensor in this case but could be anything really) and would transmit that back to a base station. The main use of energy harvesting is for powering wireless sensor nodes, so this was a simple implementation of that.
  - biomcgary 3y ago
    Don't be so modest. Citation needed. :-)
    - simonbarker87 3y ago
      Lol, thanks - best link I can find: https://digital-library.theiet.org/content/journals/10.1049/iet-wss.2010.0053 https://digital-library.theiet.org/content/journals/10.1049/... Looks like it was an IET journal, I think my IEEE publications were all conferences.
      - biomcgary 3y ago
        The linked paper made sense once I realized mg is not milligrams. You sound like a former academic like me. All those papers/citations were so important (publish or perish), but now you just have to get things done, not so much writing.
helpfulContrib 3y ago
About 10 years ago I did a research/what-if project, involving energy-harvesting tracker tags .. essentially a smaller/lighter version of the AirTag. It used energy-harvesting for the sensor packages, essentially charging caps if things got wet/moved/etc., but would boot up to do the sensor-data processing and communication (BLE/ANT) .. my lead on the project brought his dusty old home phone in, to give us all a stable power source, but we didn't really need it much - lots of 800mhz-900mhz in the city. Was fun to realize, even back then, that we are literally surrounded by energy and don't really have an energy problem. We have an energy management problem, which we have yet to localize at the individual, and are instead spreading the problem across our society. But, in between builds on this project, I would often daydream of a scenario where computing devices ran simply on background radiation, and there was no longer any need for cables, really, in order to compute. Its fun to note we're getting closer and closer to that point. Okay, I could build a solar powered computer and also feel such satisfaction, but .. an all-in-one wafer that simply ran on cosmic noise? Hell yeah, gimme that, sparkies!!!
- user_7832 3y ago
  Specifically for moving object like air tags, watches “automatic” movements are already a “solution” that would be easy enough to implement, and probably even provide up to a few joules (!!) per day. (If you want to start a business off this idea feel free to contact me ;) half joking but half serious)
  - simonbarker87 3y ago
    Where were you when I was wrapping up my dissertation? I’ve been in start ups ever since pretty much but not in that area sadly.
    - user_7832 3y ago
      Haha I realised this idea after a fair bit of mulling, if it gives any comfort. I’m also coincidentally finishing my thesis, albeit a master’s. In what areas of startup’s have you been in? More of electrons or software or something?
jacquesm 3y ago
How did you deal with the 'black start' scenario where you need to bring up the harvester after it is first assembled? Did it require a jump start with an external energy source or did it auto start? And did you use Silicon or something more exotic?
- simonbarker87 3y ago
  Black start wasn't problem as the current draw from the PIC waking up to check vref was so tiny it didn't stop the system charging (so long as there was a base line minimum amount of vibration). I forget the minimum amount but so long as there was more than say 20 mG (milli-gravity) of vibration acceleration then it could harvest from empty.
  - jacquesm 3y ago
    That's super cool. Lots of these systems never get past the blackstart issue and I think that pre-charging the system is cheating because if the system then ever goes for a long time without enough energy input it will die for real. So really neat to see your system did not suffer from that.
    - simonbarker87 3y ago
      Thanks, to answer your other question (that I somehow missed). This project was with totally off the shelf components - it basically formed the back bone to my literature review as current state of the art. However, the research group I was in was focussed on using silicon carbide devices for hostile environment sensors (think high temp gas sensors primarily) and looking at how to make FETs from SiC that could work in high temp/high radiation environments etc. This is why my thesis and papers primarily focussed on testing energy harvesting devices at temperature - batteries won't work at 300degC and running power cables up and into a volcano fumarole is a tad awkward. I had this feeling though that if I didn't get a room temperature, off the shelf components, system working I would have missed a key part of the learning - I just got lucky that the system was novel enough for a paper publication.
deleted 3y ago
[deleted]

zoomablemind 3y ago

Does this sort of harvesting rely upon some internal accumulator like a capacitor before the energy could be fed elsewhere? Also a question if such harvester need its own power source to be able to operate? They cite a super wide range of EM freqs from Hz to MHz, and an efficient antenna...

simonbarker87 3y ago
Yes, you need a reservoir to store the charge (energy) which in my case was the limiting factor to deployment in high temperature environments as capacitors get very leaky as temperature increases. Harvesters don’t need their own power supply and ideally the system can come back to life from totally empty (meaning it doesn’t need to be deployed with any charge level) I was doing my thing back before the packaged harvester management chips were available and I made a PIC based microcontroller system that could monitor the charge level in a capacitor fed from a piezoelectric vibration energy harvester and decide when to wake up and transmit a data reading based on the capacitors charge level. The trick was getting the PIC’s sleep current draw low enough that the capacitor was charging even at milli g level vibration levels - from memory you can get a PIC’s sleep current well down in the tens of nano amp range. PICs have a built in voltage reference that is stable (a zener or schotkey diode from memory of 0.6V?) and a way to read what the Vsupply (basically the capacitor) is compared to it. So the PIC would wake up every 30 seconds, check Vsupply to the built in reference and, when high enough fully wake up, take and transmit a reading and go back to sleep. From memory I got it running at 50mg transmitting every few minutes. I got a nice journal publication in IEEE for that work.
- zoomablemind 3y ago
  Cool project. Thanks for sharing the details! So the harvester sustains itself, keeps filling up the bucket, and periodically reports out the progress. I guess it's a balancing game, as the filling up process is probably slow, so the target's draw needs to be low too.
  - simonbarker87 3y ago
    Thanks, it didn’t report back progress of charging, it was connected to a sensor (light sensor in this case but could be anything really) and would transmit that back to a base station. The main use of energy harvesting is for powering wireless sensor nodes, so this was a simple implementation of that.
- biomcgary 3y ago
  Don't be so modest. Citation needed. :-)
  - simonbarker87 3y ago
    Lol, thanks - best link I can find: https://digital-library.theiet.org/content/journals/10.1049/iet-wss.2010.0053 https://digital-library.theiet.org/content/journals/10.1049/... Looks like it was an IET journal, I think my IEEE publications were all conferences.
    - biomcgary 3y ago
      The linked paper made sense once I realized mg is not milligrams. You sound like a former academic like me. All those papers/citations were so important (publish or perish), but now you just have to get things done, not so much writing.

helpfulContrib 3y ago

About 10 years ago I did a research/what-if project, involving energy-harvesting tracker tags .. essentially a smaller/lighter version of the AirTag. It used energy-harvesting for the sensor packages, essentially charging caps if things got wet/moved/etc., but would boot up to do the sensor-data processing and communication (BLE/ANT) .. my lead on the project brought his dusty old home phone in, to give us all a stable power source, but we didn't really need it much - lots of 800mhz-900mhz in the city. Was fun to realize, even back then, that we are literally surrounded by energy and don't really have an energy problem. We have an energy management problem, which we have yet to localize at the individual, and are instead spreading the problem across our society. But, in between builds on this project, I would often daydream of a scenario where computing devices ran simply on background radiation, and there was no longer any need for cables, really, in order to compute. Its fun to note we're getting closer and closer to that point. Okay, I could build a solar powered computer and also feel such satisfaction, but .. an all-in-one wafer that simply ran on cosmic noise? Hell yeah, gimme that, sparkies!!!

user_7832 3y ago
Specifically for moving object like air tags, watches “automatic” movements are already a “solution” that would be easy enough to implement, and probably even provide up to a few joules (!!) per day. (If you want to start a business off this idea feel free to contact me ;) half joking but half serious)
- simonbarker87 3y ago
  Where were you when I was wrapping up my dissertation? I’ve been in start ups ever since pretty much but not in that area sadly.
  - user_7832 3y ago
    Haha I realised this idea after a fair bit of mulling, if it gives any comfort. I’m also coincidentally finishing my thesis, albeit a master’s. In what areas of startup’s have you been in? More of electrons or software or something?

jacquesm 3y ago

How did you deal with the 'black start' scenario where you need to bring up the harvester after it is first assembled? Did it require a jump start with an external energy source or did it auto start? And did you use Silicon or something more exotic?

simonbarker87 3y ago
Black start wasn't problem as the current draw from the PIC waking up to check vref was so tiny it didn't stop the system charging (so long as there was a base line minimum amount of vibration). I forget the minimum amount but so long as there was more than say 20 mG (milli-gravity) of vibration acceleration then it could harvest from empty.
- jacquesm 3y ago
  That's super cool. Lots of these systems never get past the blackstart issue and I think that pre-charging the system is cheating because if the system then ever goes for a long time without enough energy input it will die for real. So really neat to see your system did not suffer from that.
  - simonbarker87 3y ago
    Thanks, to answer your other question (that I somehow missed). This project was with totally off the shelf components - it basically formed the back bone to my literature review as current state of the art. However, the research group I was in was focussed on using silicon carbide devices for hostile environment sensors (think high temp gas sensors primarily) and looking at how to make FETs from SiC that could work in high temp/high radiation environments etc. This is why my thesis and papers primarily focussed on testing energy harvesting devices at temperature - batteries won't work at 300degC and running power cables up and into a volcano fumarole is a tad awkward. I had this feeling though that if I didn't get a room temperature, off the shelf components, system working I would have missed a key part of the learning - I just got lucky that the system was novel enough for a paper publication.

deleted 3y ago

[deleted]