How it Works

Score is a high efficiency woodstove that uses about half the wood (or dung) of a regular wood fire, creates an even smaller fraction of the smoke (a health hazard with regular fires indoors) and uses the waste heat of the stove to power a thermoacoustic generator to create electric power to power some LEDs and/or charge cellphone batteries. Later versions will power a computer.

Aside from the obvious fuel saving and health advantages to the users of the stove, the efficiency of the device reduces the amount of carbon that ends up in the atmosphere.  Some estimates place the impact of wood cooking stoves at close to 18% of the total greenhouse gasses,  creating 800,000 metric tons of soot worldwide a year. With half of the worlds population using wood stoves to cook and nearly half the wood in the world being used for cooking, this stove (and similar devices) could change the world.

The thermoacoustic innovation is a big bonus because it’s cheap, very reliable (one moving part) and uses heat that was going to be wasted up the smokestack. It works by  exploiting the fact that a properly dimensioned tube that is heated at one end and has a porous heat absorbing substance (steel wool…) separating it from the cooler end of the tube will generate a sound (Google thermoacoustics).

If you attach a loudspeaker to the open end of the tube the sound will oscillate the coil in the speaker and that moving coil will generate electricity (this is how microphones work).

The refrigeration part is a little trickier. If you take the same tube and drive a sound into it, the air moving past the heat absorber, the air compressing (and heating) and decompressing (and cooling) will cause one end of the tube to get hot and the other to get cold. So if you combine two of these devices, with one using heat to generate sound and the other using the sound to pump heat out of a small fridge with a modified loudspeaker/generator between the two, you  have an extraordinarily clever and useful device.

All of this for only £20, ($40)!

Explanation courtesy of Michael Crumpton,