Heating and cooling systems are among the biggest guzzlers of energy, contributing to a vicious cycle of climate change that then drives higher use of heating and cooling. Now engineers at Berkeley Lab have developed a new technology that heats and cools by switching a material between solid and liquid states, inducing a large temperature change from a small voltage.
Most air conditioning and refrigeration systems currently in use work through vapor compression, where a refrigerant cycles between a liquid and a gas. In its liquid form, the refrigerant absorbs heat from a room or space and becomes a vapor, which is then compressed and condensed back into a liquid, transferring the heat away in the process. The liquid eventually re-enters the evaporator and the cycle continues.
The problem is that these systems aren’t very green. Not only do they consume a lot of energy, but the vapors used are potent greenhouse gases if and when they escape into the atmosphere. Scientists are developing alternative technologies, but it’s hard to find any that are effective, efficient and environmentally friendly.
To better contain the refrigerants, scientists are investigating other types of phase-change materials that shift between solid and liquid instead of liquid and gas. These have shown up in clothing, coffee cups and building materials, and the change is usually triggered by forces like pressure, twisting, magnetism or electric fields.
In the new study, the Berkeley Lab team developed a new phase-change material that works on a different trigger – the flow of ions. The material is made up of a salt of iodine and sodium, plus an organic solvent called ethylene carbonate. When a current is applied to the solid material, ions are added to it and it melts, absorbing heat from its surroundings. In reverse, the ions are drawn away from the material and it crystalizes back into a solid, releasing its stored heat.
The team calls this process “ionocaloric cooling.” In experiments, the system was quite effective – the material changed its temperature by 25 °C (45 °F) under as little as 0.22 volts, which is far greater than other phase-change cooling systems.
In these early stages, the team says the technique looks promising in regards to efficiency, environmentally friendliness and cost. But there’s still plenty of work to do to investigate how well it might scale, and test different types of materials that work on the same principle.
The research was published in the journal Science.
Source: Berkeley Lab
