Energy Harvesting: A Realistic Approach to Powering IoT Systems

At first energy harvesting sounds like a topic related to free energy, which is a subject that is flooded with fake designs of machines that supposedly create more output power than they require on the input, making them perpetual motion machines. However, it's essential to understand what energy harvesting actually is.

Let's imagine we have an IoT system consisting of a microcontroller and a sensor. The microcontroller's job is to power up every hour, get the sensor's current measurement (e.g., temperature), send this data out to a receiver, and then go into deep sleep. Now, let's assume this system needs 3.3V and draws 10mA for 1 second while gathering data and sending it, but otherwise only draws 3uA in deep sleep.

A common LiPo battery with a capacity of 7.4Wh could theoretically power the IoT system for around 44 years, which sounds good at first. However, have fun replacing perhaps thousands of those batteries all around your factory after practically speaking 10 years and maybe half or more of those batteries will probably be dead and cannot be reused.

One possible solution is to use energy harvesting, which involves converting environmental energy into electrical energy that can power our devices. In this article, we'll explore three common types of energy harvesting: mechanical vibrations, heat, and radio frequencies.

Mechanical Vibrations: A Promising Option

Mechanical vibrations are a promising source of energy for IoT systems. We can use a device called a piezoelectric module, which converts mechanical stress into electrical energy. In this experiment, we attached the piezoelectric module to our washing machine during the spin cycle. The output was relatively low, but it's clear that mechanical vibrations could power our IoT system.

To improve the efficiency of mechanical vibration-based energy harvesting, we can use a Peltier module as a harvester. A Peltier module is a type of thermoelectric device that converts heat into electrical energy. We placed the Peltier module on a pot filled with water at a lower temperature and connected it to another pot filled with water at a higher temperature. The output voltage was relatively low, but by connecting two Peltier modules in series, we were able to reach a high enough voltage to power our red LED.

Heat as an Energy Source

Another promising energy source is heat. We used a Peltier module as a harvester and placed it on top of a pot filled with water at a lower temperature. The output voltage was relatively low, but by connecting two Peltier modules in series, we were able to reach a high enough voltage to power our red LED.

Radio Frequencies: A Skeptical Approach

Radio frequencies (RF) are another type of energy harvesting that involves capturing electromagnetic waves and converting them into electrical energy. At first, I was skeptical about the feasibility of RF energy harvesting because it requires a specific designed antenna for a certain frequency band, as well as a rectifier that can work with high frequencies.

However, there is an example of an energy harvesting IC (integrated circuit) called UB20M from the University of Bristol. When connected to an IR photodiode and an LED, the IC switches its output on and off according to the infrared light sent out by a TV remote. This means that instead of leaving your TV in standby mode, which still draws a small amount of power, we could use such an IC to decrease the TV's standby power even further.

In conclusion, energy harvesting is a real electronics topic nowadays and very important for certain applications. While there are challenges associated with each type of energy harvesting, it's clear that mechanical vibrations, heat, and radio frequencies can be used as viable options to power IoT systems. By understanding how these technologies work and experimenting with different designs, we can create innovative solutions that reduce our reliance on traditional battery-powered devices.

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WEBVTTKind: captionsLanguage: enAt first energy harvesting sounds like a topicrelated to free energy which is a subjectthat is flooded with fake designs of machinesthat supposedly create more output power thanthey require on the input which makes themperpetual motion machines.But of course there does not exist such amachine which is why I even exposed two designsof such fake machines in my free energy BSvideo.But what is energy harvesting then, you mightask?Well let’s imagine we got an IOT systemwhich for example consists of a microcontrollerand a sensor.The microcontrollers job is to power up everyhour, get the sensors current measurementwhich can be for example the temperature,send this data out to a receiver and thengo into deep sleep.Let’s imagine this system needs 3.3V anddraws 10mA for 1 second while gathering thedata and sending it but otherwise the systemonly draws 3uA in deep sleep.That means such a common LiPo battery witha capacity of 7.4Wh could theoretically powerthe IOT system for around 44 years which soundsgood at first.But have fun replacing perhaps thousands ofthose batteries all around your factory afterpractically speaking 10 years and maybe halfor more of those batteries will probably bedead and cannot be reused.So wouldn’t it be awesome to just harvestenergy from nearby available energy sourceslike the sun light, mechanical vibrations,heat or radio frequencies and power our IOTsystems with that.And I know this sounds a bit crazy but itis partly easily possible and I will testit out in this video to find out whether energyharvesting makes any sense at all.Let’s get started!INTROThis video is sponsored by JLCPCB!Feel free to visit their website JLCPCB.comto not only find out what awesome PCB andAssembly services they offer but also to easilyupload your Gerber files and thus order affordableand high quality PCBs quickly.First off I have to say that using sun lightto power electronics is certainly not crazynowadays and widely known as a photovoltaicsystem.I even made several videos about the topiclike building a photovoltaic off grid systemin my garage or creating my own solar paneland that is why I will not talk much furtherabout this topic in this video.But let me just say that you can get sucha small solar panel for relatively cheap andthey can easily output more than enough powerfor our imaginary IOT circuit.With that out of the way let’s move on tomechanical vibrations which you can commonlyfind in factories due to motors and a goodexample for that in your household is yourwashing machine which I will be using as atest subject in a second.Before doing that though we have to thinkabout what makes up an energy harvesting system.At the beginning we obviously need a harvesterwhich turns our source energy into raw electricalenergy.Then we need a conversion circuit that takesour raw electrical energy which was maybean AC voltage and turns it into a DC voltagewhich we can then use to charge up the nextpart of the system, the energy storage.This can be a normal or supercapacitor withenough capacity to power the last part ofthe system, the electronic load.And now that we are familiar with the basicstructure let’s try to come up with a completesystem for the mechanical vibration energy.As a harvester we can use such a piezoelectricdisc which after soldering wires to its twoplates outputs an AC waveform whenever wehit it.But as you can see such a tiny disc cannotreally output big voltage spikes which wewill definitely need.That is why I got myself a bigger disc whichcan certainly output higher voltages.Next we need a conversion circuit which turnsthe AC voltage into a DC voltage and for thatwe need such a full bridge rectifier circuitwhich I created with the help of four 1N5822Schottky diodes.Those diodes are suitable for this job sincethey feature a low forward voltage and theyalso work with high frequencies.So after hooking up the rectifier to the disc,all we have to figure out was a suitable capacitorvalue for which I firstly chose a 22uF oneas a test.After hooking that up to the rectifiers outputand then connecting my oscilloscope probesto it, I hit the disc with the handle of oneof my screw drivers continuously and as youcan see the voltage went up to a value of5V within just 7 seconds.The gathered energy was even sufficient topower a 5mm red LED for a brief moment whichis why I wanted to push this system even furtherby hooking up a 220uF capacitor.As you can see the voltage took a quite abit longer to increase up to 5V but this timewe can let the LED light up longer and evena tiny bit continuously which was a very goodsign.So as a final test I used double sided tapeto attach the disc to my washing machine,selected the spin option and hit start.As you can see on the oscilloscope the voltageclimbed super slowly and never reached valuesto illuminate the LED.By switching to a smaller capacitor value,the rise time did decrease quite a bit buthitting the disc was certainly more effective.But nevertheless even though the last testwas not perfect, I strongly believe that mechanicalvibrations could power our IOT system.And with that being said let’s move on toheat for which we can use a Peltier Moduleas a harvester.When we heat up one side of it while keepingthe other cool, then the module will outputa DC voltage which we can hopefully use.The real life example in a factory would simplybe an oven or something similar and a goodexample for excess heat at home would be myinduction cooking field right after I am donepreparing my meal.With a temperature of around 80 degrees Celsiusit should be able to deliver a bit of energywhich is why I simply placed the Peltier moduleon it, onto which I then positioned a potfor cooling the other side.Sadly though the module only output around1V which was not enough for my red LED butby simply connecting two Peltier modules inseries we can easily reach a high enough voltageand also draw enough power to light up theLED without a problem which is why I thinkthat using heat as an energy source for anIOT system is definitely possible.But if you do not believe me yet then feelfree to watch my video about creating a thermoelectricgenerator.And that brings us to the last energy source,radio frequencies which was the energy sourceI was most skeptical of.I mean yes, according to this picture of theUnited States Frequency Allocations, thereseems to be lots of radio frequencies aroundus all so there should be some that we canuse.But the problem is that you need a specificallydesigned antenna for a certain frequency bandsand your rectifier also needs to be able towork with such high frequencies and let’snot forget that you need to live near a radiofrequency broadcaster to get any useful power.So no matter which RF energy harvester circuitfrom google images you try out, you will mostlikely never get any decent results whichwhy I can say that RF energy harvesting willwith high probability not power our IOT system.But nevertheless in the end we can say thathaving 3 of 4 energy harvesting options towork out in a positive way is definitely nota bad result.And nowadays there even exist energy harvestingICs like this UB20M one I received from theUniversity of Bristol.By hooking up an IR photodiode to its inputand connecting an LED and power source toits output we can see that by using a TV remotethe IC switches its output on and off accordingto the infrared light sent out by the TV remove.The reason is that the IC is actually poweredby the energy of the infrared light and turnson its output as soon as a threshold voltagevalue on the input is reached.That means instead of leaving your TV in standbymode, in which the TV still draws a smallamount of power, we could use such an IC inorder to decrease the TVs standby power evenfurther and thus saving energy.And I hope that with this final example younow understand that energy harvesting is areal electronics topic nowadays and very importantfor certain applications.I hope you enjoyed this video, if so don’tforget to like, share, subscribe and hit thenotification bell.Stay creative and I will see you next time.