Thermoacoustics would have remained a theoretical science for laboratories and physics rooms, if not for previous inventions in another branch of physics - thermodynamics. It received a new period of revival with the invention of the Stirling heat engine. This happened back in the 19th century, and almost immediately led to a revolution in the technical field. Thermal energy began to be widely used in all kinds of engines. But the invention we are examining today relates specifically to thermoacoustics - the science of the interaction of sound and heat. You may ask, what does the engine and generator have to do with it? Let's sort it out in order.
Operating principle of a thermoacoustic motor
This improvised device is literally assembled from scrap materials, or even their remains. However, this does not prevent it from being called an engine-based generator, producing electricity from heat. This phenomenon is based on the principle of creating acoustic waves passed through a resonator with two membranes that create resonance. On the top of them there is a magnet that vibrates from these waves with a certain frequency. This results in the formation of a magnetic field that is captured by the inductor. It, in turn, is capable of producing electric current transmitted to the consumer.
The basis of this invention is the upper module - a thermoacoustic converter or engine. Essentially it is a glass tube, which is divided into three zones:
- Heating zone – air or gas is heated in it;
- Regenerator zone - a substance that alternately comes into contact with cold and hot air;
- Cooling zone – in which the air temperature decreases.
Materials and tools
To create an engine generator we will need the following ingredients:
- Glass heat-resistant tube;
- A piece of metal pipe;
- Several PVC plumbing corners;
- A piece of cardboard tube;
- Rubber ball or glove for membranes;
- Insulating tape;
- A roll of steel wool or dishwashing sponge;
- Neodymium magnet;
- Inductor;
- A small piece of cloth for washing dishes;
- Wooden lining for an external socket or switch;
- Sealant, glue.
Among the tools, we can recommend having something that a true tinkerer should always have on hand: a knife, pliers, wire cutters, a screwdriver, a glue gun and a silicone gun.
Assembling a thermoacoustic generator
The engine design is assembled on the basis of frame copper tubes and one glass tube. What unites them is a resonator - an important and unusual part of this engine. This is where the sound waves created by the regenerator move.
This is a simple cardboard tube, in the middle of which there is a membrane that prevents air from circulating. If we exclude this element, then there will simply be no vibrations in the upper membrane, which is located in the neck of the resonator.
The author of the video chose to cut the tube in half and stretch a piece of rubber medical glove over one of the parts as a lower membrane. He wrapped the seam of the connected resonator fragments with electrical tape.
He expanded the neck of the resonator specifically to enhance the effect of sound vibrations from the regenerator on the upper membrane. He made it from the denser rubber of a balloon. At the bottom of the tube there is a wooden backing for an external switch or socket for installation stability.
The glass tube-motor is a test tube with a piece of steel wool or shavings placed in the middle. After the regeneration zone, air cooling should occur, which is facilitated by a piece of cloth soaked in water and wrapped around the base of the test tube. Due to the movement of air through two opposite temperature environments, intense generation of sound waves occurs.
The final part of the motor is a small but powerful neodymium magnet. It then creates small but very frequent vibrations transmitted from the membrane under the influence of sound.
To turn this thermoacoustic motor into a generator, we need an inductor or a simple solenoid.You can make this element yourself by winding copper wire onto a reel, for example, from fishing gear. The main condition is that its internal diameter must be larger than the diameter of the magnet.
As a thermal energy transmitter for small installations, you can use an ordinary candle or a piece of dry alcohol, and at the same time compare the power received from different heat sources.
In the experiment, the author demonstrates the effect of bringing the inductor closer to the magnet and moving it away. Since there is no storage capacity in this electrical circuit, the difference is noticeable instantly.
By fixing the coil in the magnetic field zone, you can receive electricity from such a generator to power, for example, an LED panel or lights.
Conclusion
Of course, such an invention today cannot be considered completely finished and complete. It requires improvement, since the author himself admits that the vibration from sound waves is quite noticeable. The engine housing is light and does not contain any stabilizer, and the design itself is flimsy. However, the very fact of generating electricity from heat cannot be ignored. Perhaps your modernization of this installation will lead to a grand breakthrough in the field of alternative energy, and the world will finally receive a source of cheap clean energy without harm to our planet.
