According to U.S. Department of Energy figures from 2014, our cooling needs amount to 27% of our annual electricity consumption, 13.7% on average for our refrigerators and 14.1% for our air conditioners. While new energy-efficient fridges use only a quarter of the kWh of old models, their energy consumption is still substantial—other estimates put personal fridge energy consumption at 20%-40% of total usage. Cooling amounts to 10% of global electricity usage when industrial and domestic refrigerators and home and car air conditioning systems are included.
But a team of physicists and engineers at the NUST MISIS Department for Functional Nanosystems & High-Temperature Materials and Tver State University has developed a new way to generate cold by using a magnetic cooling system.
In a conventional refrigerator, cooling occurs due to the sudden evaporation of freon or other refrigerants passing into a gaseous state. The Russian scientists used a different principle—the so-called magnetocaloric effect, which is the change of magnetic material temperature during its magnetization or demagnetization.
By introducing a metal bar into a magnetic field, it heats up. When removed from the field it cools down. By creating quick cycles to maintain the temperature difference, the scientists were able to design a small device prototype that’s capable of cooling an entire refrigerator.
“Since the density of the metal alloy is much greater than that of the gas, the stored entropy value (measure of disorder), and therefore its cooling capacity, is greater,” explains one of the project developers, senior researcher at the NUST MISIS Department for Functional Nanosystems & High Temperature Materials Dmitry Karpenkov, “this explains the 30–40% higher energy efficiency of new solid-state devices compared to gas-compression analogues.
By distinguishing the flows of heat transfer fluid from the cold and hot heat exchangers, while allowing the working fluid, being in a magnetized (demagnetized) state, to sequentially move from one flow to another, the scientists were able to use cascade magnetic cooling cycles, which led to an 80% increase in the cooling range.