SoundEnergy, a Dutch company, has demonstrated a thermal acoustic engine which takes heat from any source and produces a powerful cooling effect without requiring power from any other source – potentially providing air conditioning or refrigeration from industrial waste heat or solar energy.
The device combines two technologies which have been understood for a long time but, to date, have had only niche application.
The ability of heat to produce sound was noted by glassblowers centuries ago. In the 1850s experiments showed that a temperature differential drove the phenomenon.
In 1859, the Dutch physicist, Pieter Rijke, demonstrated that a heated wire mesh placed at the point of greatest air pressure greatly magnified the sound. The effect is the result of heat convention from the mesh interfering with sound wave in the tube.
The SoundEnergy device sets up a sound wave in argon gas in a closed loop and applies heat, which can come from any source, at the appropriate points to greatly amplify the sound.
The other technology employed by SoundEnergy is the Stirling cycle which was first used in an engine patented by the Scottish inventor, Robert Stirling, in 1816. There are various types of Stirling Engine but, basically, they use the differential between the hot and cold ends of a closed cylinder to expand and contract a gas within the cylinder. This expansion and contraction is used to drive a cylinder and do work.
Unlike other heat engines, the Stirling cycle is completely reversible. That is, the motion of the piston can be used to produce hot and cold.
The SoundEnergy device uses the vibrations of the amplified sound wave to drive a reverse Stirling cycle and produce cooling.
The system has no mechanical moving parts, uses no refrigerants, no precious metals or expensive materials. It uses argon gas, which is plentiful and has no global warming effect. The company says that the device makes about as much noise as a running shower, is scalable and can produce cooling temperatures as low as -25°C. It requires no maintenance and has and has an estimated lifespan of 20 to 30 years.
The first large units, which currently cost about $us50,000, have been sold including to Dubai. SoundEnergy says that smaller units for residential purposes are possible at much lower prices.