How can I power Raspberry Pi Zero / 3B in forest where I don't have enough sun?

Question

I'm making an authonomous robot (like Phoenix probe but very simple and cheap and made for Earth, no moving parts, just sensors). It controlled by Raspberry Pi and will live in forest shadowed by trees. So, I guess I can't use the solar panel in this case (or that panel will be extremely huge).

Also, I don't want that my robot sleep during charging. Ideally, if it can record data 24/7.

I need at least 10W output for RPi powering and some additional power for battery charging (for situations when generator can't produce energy).

Which types of generators are available that can produce needed power, silent and compact enough (I don't want to bring petrol generator to forest). Also, I don't want to go to forest often to replace discharged batteries.

And I don't have any rivers and don't have powerful wind here.

I want to record video and audio (when motion is detected), and ideally run OpenCV and TFLite to recognize birds and animals.

Is it possible? Can I found a way to power it for at least a week without human interaction?

Answer 1

Redesign it with a low-power bare-metal microcontroller. Many microcontrollers use something like 0.05W when active, and 0.00001W when in deep-sleep mode. Then, you can easily power the device with a solar panel even though limited light is available.

Your code needs to conserve power by using the microcontroller's sleep mode as much as possible. For example, if you only want to measure every 5 seconds, the microcontroller should sleep for 4.9 seconds and then use 0.1 seconds to perform the measurement.

I suspect that downgrading to a microcontroller will give you plenty of power even if you leave it running all the time, so you won't need to be too fussy about sleeping.

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You indicated you need to do some video processing which really does need the computing power of the Raspberry Pi. Your main goal is still to decrease power consumption as much as possible, but you can't do it by just downgrading the computer. You need the Pi to sleep as much as possible. If it's running Linux, this is probably quite difficult, because Linux will take several seconds to go to sleep and to wake up, unlike a microcontroller that takes a few milliseconds, and this severely limits your ability to make it sleep much.

You could try underclocking and undervolting it.

You could try using a low-powered device (such as a PIR sensor or Arducam) to watch for movement and wake up the Pi when it detects some.

You could do the video processing in batches - with a low-power device recording video all the time (or when there's movement), and a high-power device running every now and again to process the recorded data.

In fact, do you really need to do the processing in the field at all? What if you bring the memory card back home after a week, and then do the video processing on your own computer? If you choose that route, you may find it better to use an off-the-shelf motion-activated video camera, instead of making your own.

Answer 2

Raise a solar panel to the top of a tree?

If you have wind, use the movement of the branches to drive a ratchet system connected to them with rope to spin a generator with each stroke