Flat Spiral Spring energy

Five watts may be "tiny". But a five-watt-hour is not.

Hi,

bending is not very efficient in storing elastic energy. Try to design a flexure in tensioning. Calculate yourself!

Energy stored in an incremental volume is square of stress divided by elastic modulus.

So integrate over available volume you will get the total stored energy.

May be you should switch from steel to aluminum or glass,carbon,Kevlar-Epoxi. Look at the materials data.

RHABE

Basically I was planning to light up a 5 w LED cluster- as a rural lantern without battery storage or photovoltaic panel. The enrgy was to be stored in a spring mechanism and energy to be released slowly over say 1 hour. From a search of web sites I got a feeling that such spring mechanism could be nearly 60 to 70 KGs and could occupy a huge space.

Now I thought of a weight lifted to a height - say manually- and as it slowly comes down- it can rotate a generator to light up 5 w LED for say 1 hour. Here again I find potential energy stored is = mgh where m is kilograms, g = about 9.8 meters / sec^2 and h is in meters.. So if we assume 2 meters height we need 1.31 tonnes or 1,311 kgs of mass to be lifted to 2 meters !!!

So unwillingly I am coming to the conclusion that there is still no alternative to battery and wind or solar panel.

Trevor Bayliss managed to power a radio using this method and the product is highly portable. I would think that the power amplifier consumption of the radio must be in the order of 5 Watts to achieve meaningful volume levels. Try googling "crank operated radio" for more on this.

I do not dispute what you have said as I have seen it on BBC. Lots of people now-a-days go around with headsets in their ear connected to a mobile phone- they are listening to FM etc for hours. Now you can listen to radio at even miliwatts of power without disturbing others. A wall clock runs for a week on a wound spring. Unfortunately - when power is involved- it does seems to be bulky.

I Had seen free power from Permanent magnet etc etc - on website. I did see one French lab showing 20 w CFL lit from static permanent magnet- with voltage, current, waveforms, circuit schematic etc etc. They never mentioned - how long the bulb remained lit- may be just 1 or 2 minutes - with the most powerful magnet known on earth !!! Their effort was highly laudable - but not of practical value as of now.

So I have already concluded (with scientifically backed calculations) that my goal of lighting 5 w LED with just spring power for minimum 1 hour is not practical - unless someone is willing to keep winding spring every 2 to 5 minutes !!!!