Building a better circuit for renewable energy harvesting

[David], [Ian], and [Sajjad] finished and submitted their entry to the ChipKIT challenge just under the wire. They designed and built a maximum power tracking circuit for use with renewable sources. That is to say, this is a voltage regulator for use with solar cells and other generative sources like wind or water power. The idea is to use the best concepts of switch-mode power supply design, but replace the more wasteful parts with circuits that can harness and roll the loss back into the output.

We have to admit, following their development choices from the write-up at the top is a bit rocky. But luckily they filmed an in-depth description of the design choices, as well as a demonstration of the circuit along with various test measurements. If you’ve got twenty minutes and some patience all will become clear in the video after the break.

This will go along great with that bucket-based hydro generator you built.


  1. theIdeaMen says:

    I did a MPPT as my senior design lab back in ’03 using an 8051. These guys make it look easy. Well done!

  2. erdema says:

    What’s advantage of using it? What is efficiency they get? I build some buck-boost converters before and I can say, it’s look that circuit does NOT efficient as they advertised. Latest topologies uses MOSFET instead of that schottky diode which doesn’t drops the voltage, increases efficiency.

    Also using single LTC3780 circuit will give you %98 efficiency for a buck-boost converter (~$6 IC). You can control it via external micro controller and could tune maximum power ratio easily, which is far more cheaper that this solution…

    • David says:

      The novel part isn’t that the boost circuit is particularly efficient-the novel part is that it uses the power from the renewable source, and delivers it to the load, wasting the minimum amount of power possible.
      A typical boost circuit, using the relationships that we derived, can be designed to work efficiently for one input voltage/output resistance combination, whereas this circuit will automatically adjust for a wide range of combinations.

      • erdema says:

        Shortly, just wondering real “values” about if this circuit does increases harvested power vs other topologies. If increases harvested power than tell us how much? Yes matching to impedance is good idea but If you cannot increase harvested power vs standard approach at all, what is the meaning of using this HW? I have doubts on this point. Your site keep silent about values. How much power gain via ChipKIT? %1, %0.1 Or %10???

        It’s not hard to buy 2x small solar panel and benchmarking ChipKit and another low input boost circuit. Don’t you wonder how much successful your circuit vs others that doesn’t uses impedance matching?

        -It looks like my messages are sent actually. Site give me error, but put my messages after… I was rewrite them again and again. (Thanks JavaScript, I don’t like you)-

  3. erdema says:

    LTC3780 chip gives %98 boost efficiency for $6.
    Does this circuit make %99?

    Also circuit uses schotty diode instead of mosfet. Latest topologies uses it for increasing efficiency. So I believe this doesn’t increase efficiency as advertised.

    I believe that, using LTC 3780 with a micro controller like arduino/attiny will give higher power ratio than this for cheaper!

  4. erdema says:

    Also chipKit uses schotty diode. Latest topologies uses mosfet for increase conversion efficiency. That means their conversion kit has lower conversion efficiency than others.

    Might be they could pull maximum energy from solar panel etc… but they waste it at boost circuit.

    LTC3780 gives %98 conversion ratio for buck boost converter for $6 chip. Driving it with a MCU like attiny85 give you better power ratio than this for cheaper!

    • SwitchModeProfessor says:

      Dear erdema, it appears you are operating in discontinuous mode… This project clearly is all about implementing a maximum power tracking algorithm using the ChipKIT and not competing on converter efficiency. Furthermore, your beloved LTC3780 has a minimum input voltage of 4V, which essentially renders it useless for tracking maximum power for low voltage sources such as thermoelectric generators and other. Read their project description. Also, ‘tune maximum power ratio’ is not a valid expression for this engineering topic, nor is ‘more cheaper’…

      • erdema says:

        Well, sounds good but what is the meaning of pulling maximum power from source if you don’t gonna use that energy efficiently? I have doubts on that point.

        Putting some power-efficiency values vs. ordinary boost circuits gives idea to us if this circuit is valuable piece of HW or just a meaningless engineering sample.

        LTC3780 might require 4V but I believe there are many boost ICs allows lower level inputs or you can also stack TEGs…

  5. smoketester says:

    Looks real interesting. Looking forward to reviewing the writeup and code. I wonder if the proposed shield mentioned in the video will be for the ChipKit Mega version only, or be built for the Uno32??

  6. Grasslandx says:

    Reblogged this on 听风.

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