Thermoacoustic generator from a beer can

I will continue the topic of alternative lighting sources that work from the heat of heating stoves. In this article, I smoothly approach an interesting topic. Stirling engineoperating on the principles of thermoacoustic effect. But the Stirling engine is more complex than the diagram below.

First, a little theory. Thermoacoustic effect Is the process of converting thermal energy into energy of oscillation of the air with a frequency that we can hear as a hum. This happens according to the scheme: hot air in a flask in a flame zone of some source, heating up - expands, passes through a heat exchanger-cooler, in which it is cooled and compressed. It turns out a cyclic process of oscillations of the air environment inside the bulb.

A striking variant of the models demonstrating this effect is the Stirling engine:

Scientific gifts from Chinese manufacturers. A similar model can be purchased at aliexpress

The Stirling engine is arranged like this. A coil of thin steel wire is placed in a glass flask, and at the end there is a metal radiator (to increase efficiency, it is better to wrap it with a wet cloth). Inside the flask there is a piston with a connecting rod, which drive the wheel in rotation. If the engine is of sufficient size and power, it will be able to rotate a small generator from a spirit lamp or candle (for example, a motor from a DVD drive). But about this option - in the next article.

The energy of fire through the thermoacoustic effect does not need to be transformed into translational and then into rotational motion. Air vibrations can be converted directly into electricity. By means of piezoelectric elements installed on the resonator-membrane. For example, made from an aluminum can:

The lid of the can is cut off and a lid with a hole for a plastic flask is installed. The cost of the piezoelectric element is low:

Piezoelectric element of Soviet and Chinese production. It is a simple element that can convert vibrational energy applied to it into an alternating electrical voltage. And vice versa: electrical vibrations in air vibrations, sound.

There is a wider selection of them on aliexpress, but the prices do not differ much:

Glass flasks (preferably tempered glass) are purchased from organizations that sell chemical dishes, chemical reagents.

The assembly and demonstration of the thermoacoustic generator is shown in the video:

Where can this effect and a simple device be applied? For lighting? But the flame of a candle is already a source of light. Because the power is small, then there is little light, only for decorative lighting. But such generators can be assembled in several pieces. Install the edges of the flasks on a stove-stove, and remove the wiring from the piezoelectric elements where necessary. Option for lighting houses for hunters, tourists (brought it once and use it) while burning firewood in the stove.

The downside of this generator is the hum. You can get rid of it by assembling a slightly different soundless thermoacoustic generator with high efficiency. But more on that in the next article ...

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Photo taken from open sources, from Yandex. Pictures

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