Saarland researchers flex ‘muscle’ in innovative heating/cooling system

German researchers have prototyped an innovative heating/cooling system that stresses and unloads nickel-titanium “muscle wires” to create heated and cooled air at twice the efficiency of a heat pump or three times the efficiency of an air conditioner. The device is being heralded as a more environmentally-friendly way to heat or cool a space, thanks to its capability to reduce energy use and the fact it does not use refrigerant gases.

The prototype device was developed by a research team led by Professors Stefan Seelecke and Andreas Schütze at Saarland University using nickel-titanium or nitinol, a shape-memory material that absorbs significant amounts of heat when it’s bent out of shape, and then releases that heat when it’s allowed to revert to its normal shape.

The EU Commission and the US Department of Energy have both assessed the new process and consider it to be the most promising alternative technology to existing vapour-compression refrigeration systems.

Saarland, a small southwestern state and industrial hub in Germany, is making strides in the area of heating and cooling, thanks to engineers at Saarland University and at Zema, the Center for Mechatronics and Automation Technology, a research hub for collaborative projects involving researchers from Saarland University, Saarland University of Applied Sciences (htw saar) and industrial partners. Zema is home to a number of projects looking at new concepts for cooling, including the DFG-funded priority programme ‘Ferroic Cooling’. Refrigeration is one of the main sinks of the German and European electricity consumption and accordingly contributes to worldwide CO2 emissions.

The prototype is the first continuously operating machine that cools air using this process. A rotating cylinder is covered in nitinol wire bundles. The wires are loaded up as they pass through one side, sucking heat out of the air and storing it up. Then as they rotate past the other side, they’re allowed to snap back into shape, dumping the heat on the second side. Air is blown through chambers on each side, giving you one feed of heated air and another feed of cool air, so the device can therefore be operated either as a heat pump or as a refrigerator.

The Saarland University team claims that “the heating or cooling power of the system is up to thirty times greater than the mechanical power required to load and unload the alloy wire bundles” depending on the type of alloy used.

Professor Stefan Seelecke, the university’s Chairman of Intelligent Metal Systems, adds: “Our new technology is also environmentally friendly and does not harm the climate, as the heat transfer mechanism does not use liquids or vapors. So the air in an air-conditioning system can be cooled directly without the need for an intermediate heat exchanger, and we don’t have to use leak-free, high-pressure piping.”

The team of Saarbrücken engineers will exhibit the technology at Germany’s Hannover Messe in April, the leading industrial trade show.

Via: Saarland University, New Atlas)