Heating and cooling systems are among the most energy intensive systems, driving the vicious cycle of climate change and driving the use of heating and cooling. Now, Berkeley Lab engineers have developed a new technique that heats and cools materials by switching them between solid and liquid states, inducing large temperature changes from small voltages.
Most air conditioning and refrigeration systems in use today work by vapor compression, in which a refrigerant circulates between a liquid and a gas. Refrigerant in liquid form absorbs heat from a room or space, becomes a vapor, is compressed and condenses back to a liquid, releasing heat in the process. The liquid eventually re-enters the evaporator and the cycle continues.
The problem is that these systems are not very environmentally friendly. Not only do they consume large amounts of energy, but the steam used is a powerful greenhouse gas when released into the atmosphere. Scientists are developing alternative technologies, but finding one that is effective, efficient and environmentally friendly is difficult.
To better contain refrigerants, scientists are investigating other types of phase change materials that change between solid and liquid rather than liquid and gas. They appear in clothing, coffee cups, and building materials, and the changes are usually caused by forces such as pressure, torsion, magnetism, and electric fields.
Jenny Nath/Berkeley Lab
In a new study, a team at Berkeley Lab has developed a new phase-change material that acts on another trigger, the flow of ions. This substance consists of salts of iodine and sodium and an organic solvent called ethylene carbonate. When an electric current is applied to a solid material, ions are added to it, absorbing heat from its surroundings and melting it. Conversely, ions are pulled away from the material, crystallize back into a solid, and release their stored heat.
The team calls this process “ionic calorie cooling.” In experiments, this system has been very effective. The material changed temperature by 25 °C (45 °F) with just 0.22 volts. This is much higher than other phase change cooling systems.
In these early stages, the team says the technology looks promising in terms of efficiency, environmental friendliness and cost. But there is still a lot of work to be done to investigate how well it can scale and test different kinds of materials that work on the same principle.
A study was published in a journal chemistry.
Source: Berkeley Lab
