Piezoelectric energy harvesting on the cheap. - Page 1
Forum section: electronics / beginners

author: MattiStef
author_rank: Newbie
timestamp: April 29, 2014, 03:55:39 pm
content: Hello people of knowledge.I am working on a buoy system that needs to be deployed for long periods. The system currently is designed to use solar-cells to extend the lifetime but sun is only viable for 3-5 months of the year at the arctic circle. I want to test piezoelectric energy harvesting using wave motion but all the ones I find like Midé Volture are to expensive for a student.I thought I might check if anyone here had any ides before I glue a bunch of buzzers to a plate.

author: DenzilPenberthy
author_rank: Frequent Contributor
timestamp: April 29, 2014, 04:05:35 pm
content: A magnet with a decent amount of mass suspended from a spring moving through a coil rigidly attached to your buoy which is moving up and down might harvest a decent amount of power and be cheap and easy?

author: Rick Law
author_rank: Super Contributor
timestamp: May 01, 2014, 12:38:31 pm
content: It may well be cheap and easy comparing to taking a boat up to the arctic circle to change battery...

author: SeanB
author_rank: Super Contributor
timestamp: May 01, 2014, 01:13:22 pm
content: If the buoy will freeze you will have issues, but the magnetic charging using basically a shake and light torch, with a spring each side of the magnet to allow it to oscillate freely in the coil will probably work well. You probably will need a few working together, or a longer tube with a few magnets spaced apart that drives a energy harvester IC to charge a battery. Shariar ( thesignalpath) did a video on the IC's and how they work, and providing the load is light enough this will probably provide enough power.What power requirements do you have and what battery are you using?

author: Legit-Design
author_rank: Frequent Contributor
timestamp: May 01, 2014, 01:20:31 pm
content: Quote from: SeanB on May 01, 2014, 01:13:22 pmhttp://www.instructables.com/id/Salvaging-a-%241-Fake-Shake-Light/http://www.ebay.com/gds/Fake-shake-LED-flashlights-/10000000001237892/g.htmlthere are batteries inside those shake magnet lights, after the batteries are empty the device doesn't produce any light except maybe tiny tiny flicker with rigorous shaking. Most don't even produce that tiny flicker.

author: Rick Law
author_rank: Super Contributor
timestamp: May 02, 2014, 05:11:15 am
content: Most of the wave motion would not be directly up/down or even close to the vertical axis. That apart from reducing vertical to just a percentage, also reduce efficiency in another way. Any side way movement not only is wasted, it creates an energy lost in friction. Imagine if a block of weight sliding down a pole, the friction between the pole and the block of weight will drain energy.An alternative way perhaps is to design something that spins instead of up/down movement so you extract more energy out of every cycle of up/down.I think it would be more advantageous to look at something that spins than going up and down. Think of an alternator/generator with the spin axial bolted to something like a extended half-flywheel. Each time when the vertical axis of the buoy tilts, this half flywheel will fall towards low side and spin the generator axial. (Let say spinning it clockwise)Now imagine if another half-fly-wheel is mounted to the generator housing such that when the wheel is falling, it is geared so that the generator rotates in the opposite direction. (Counter clockwise)So, when the buoy tilts in any direction, one or both fly wheel "fall" toward the low side, it spins either the generator housing counter-clockwise (let say), or the generator axial clockwise, or both. This should improve efficiency significantly ... I think ... Prototype will be helpful.Such setup may gather a lot more energy than just capturing the vertical movement.Now even if this works, the harsh environment would mean this would freeze, or corrode, or... But I think at least this will extract more energy than up/down only movement, and if a prototype tests positive, you can attack the freezing problem.

author: kolbep
author_rank: Frequent Contributor
timestamp: May 02, 2014, 05:42:08 am
content: IIRC, it is the cheap shake lights that use 2 non-rechargeable button cells in series, this is so that it will last just long enough to get past the couple of weeks guarantee, then you get to buy a new one...I am sure a more decent one will have a supercap or 2 in it so that it does not wear out.there are batteries inside those shake magnet lights, after the batteries are empty the device doesn't produce any light except maybe tiny tiny flicker with rigorous shaking. Most don't even produce that tiny flicker.