Cooling requirements is continuously growing nowadays. Nevertheless, the energy requirements to obtain it are really high. Most of the technologies used to ‘generate’ cooling are based on electricity. We can also find some passive solutions that make use of shadowed places where air is cooler. These solutions are known as free-cooling. However, we would like to show you an outstanding development of free-cooling that doesn’t depend on shadowed areas. Thanks to metal muscles (or better known as shape memory alloys), a free cooling process is being undertaken in Saarland University.
Metal muscles: shape memory alloys (SMAs)
As we have mentioned, cooling is one of the main energy consumers in buildings nowadays. Therefore, strategies to diminish its enormous waste are highly expected. Some solutions to ‘produce’ cooling rely on refrigerants or electricity that create pollutants or require a vast amount of energy. In order to cut off pollutant emissions, passive strategies based on free-cooling are required.
Researchers from several institutions such as Saarland University or the Center for Mechatronics and Automation Technology (ZeMA) in Saarbrücken, are currently developing a passive solution based on ‘metal muscles’, or better known, shape memory alloys (SMAs). More specifically, they are using a nickel-titanium alloy. This alloy has ‘memory’. That means that elements made of this material can have an initial shape that is recovered after being changed by heat.
Shape memory means that wires or sheets made from a nickel-titanium alloy have a certain ability to remember their original shape: If they undergo deformation, they will return to their earlier shape. So they are able to tense and flex like muscles. The fact that they absorb and release heat when they do so is something we exploit to achieve cooling
The secret is within the crystal structure of the material. When it is deformed or pulled in tension, the crystal lattice structure can change thanks to the phase transition property of the material becoming hotter. When it can relaxed, it cools down even 20ºC below the environment temperature.
Researchers are currently designing a prototype for a complete air-conditioning system. We are looking forward to knowing their results as soon as possible.