After the previous post I've been thinking about what to do as a harvesting project; I'd like to make something fun, but not completely useless, even think of what the technology might mean on a larger scale. I'd also like to make something that shows both the energy harvesting AND the low-power microcontroller features. Last week I got an email from element14 anouncing the deadline for the design challenge. That's when I felt I really had to make up my mind on what to make. Here we go....
Harvesting from the shower
As stated previously, I wanted to harvest energy from the thermostatic tap in my shower. As Gelmin showed, running water gives enough heat flow to harvest from, and the thermostatic tap even has a hot AND a cold side with low thermal impedance (flowing water), so it should be easily possible to charge! I tried to do this, but couldn't make a good mechanical construction to mount the peltier. I gave up on this track, because I couldn't find a good way to solve this. The target of the design challenge is to make something that could be used on a larger scale. I think items that could be made with this source could be shower timers (Very green! shower timer to preserve energy running on energy harvesting....), or maybe a shower radio (less green, saving batteries, but probably extending your stay under the shower).
Still want to cook eggs....
OK. Have to cut ties. Make decisions. I'm going to cook eggs.
I had the idea of making an egg timer, and I'll still go for it, although my original idea wouldn't work. Originally, I wanted to make an egg timer in the shape of an egg. Now I found out it wouldn't work, I'll adapt a pan to do the equivalent thing. I bought a pan with a nice flat lid in a thrift store, and that lid will be the mounting point for my hardware.
Pan, with peltier+heatsink, with thermally conductive glue (look at that label! Guess the glue isn't food save...)
Why cook an egg?
The egg cooking in itself doesn't need energy harvesting. The Point of this project is that it will show Energy Harvesting technology, combined with calculations on the EFM32 to determine the 'hardness of the egg'. Also, on a larger scale, this could be developed in food safety programs, think about cooking water long enough to kill bacteria, or sterilize by cooking long enough. This will work even in places with no electricity or stable energy sources at hand, for example third world situations or disaster areas.
Mounting the peltier element
To mount the peltier element, I used thermally conductive glue. Since I didn't have a glue clamp at hand, I took my 3kg axe. Ah, the subtleties of prototyping.
