Nowadays, the average global temperature is 1.2 degrees higher than before industrial times. It is estimated that by 2050 the difference would reach 2 degrees. The weather is getting hotter and the demand for air conditioners is growing. In many many developing countries the Air Conditioners are still considered a luxury item not a necessity. The demand for coolers and air conditioners would grow fast in the coming years. The energy which is consumed by the ACs is a critical matter. First of all, at the hottest days of summer the demand for air conditioning would sky rocket, this puts an extra pressure on the electricity grid which leads to long power outages in less developed countries with weaker grids. On the other hand the amount of carbon emissions produced by ACs are larger than the total aviation industry, reducing the energy consumption for ACs is also important for decarbonizing and reaching net zero emission.
Air conditioners currently employ this electricity to suck in heated air and pass it over a cool refrigerant that evaporates as it absorbs the heat from the air. The cooled air is returned to the room, and the refrigerant condenses back into a liquid, releasing its contained heat outdoors.
Conventional machines also dehumidify the air as they cool it. This is partly due to necessity: water that naturally condenses on the metal surrounding the refrigerant must be removed before it can cause any damage. However, unintentional dehumidification can make a space feel colder because low humidity allows human sweat to drain more easily, keeping skin cool.
However, juggling both tasks at once is extremely inefficient. American scientists’ research, which was published in the energy journal Joule in 2022, found that nearly one-third of the electricity required for air conditioning is utilized only to remove moisture. Over time, that percentage might rise. Because the fastest-growing countries for air conditioning are developing nations like Indonesia and India, which have higher relative humidity than affluent areas. Global average humidity is also predicted to rise because warmer air has a greater capacity to retain moisture.
One technique to reduce the amount of dehumidification work an air conditioner unintentionally must do, is to expose the incoming air to a water-absorbing chemical known as a desiccant. Though desiccants have been tested in the past, most are either restricted in their ability to absorb water or require significant amounts of energy to be reusable. Transaera, a Massachusetts-based start up, has instead focused on crystalline structures known as metal-organic frameworks. These are molecular cages that can be precisely tailored to capture specific “guest” particles and then release them when subjected to heat.
The company applies a MOF-based coating to a wheel inside the AC devices. As the wheel turns,It absorbs the water molecules and particles and an efficient heat generator would turn the water particles to liquid water. Field studies conducted over the summer indicate that an air conditioner equipped with this device consumes 40% less energy than conventional ACs. Transaera is collaborating with existing air-conditioning manufacturers to integrate its technology into their designs.
Trellis is also looking into alternative methods of dehumidification. It is working on a technology for filtering air using a selectively permeable membrane. The company expects that this will make a space seem cooler while requiring less active cooling.
Source: Economist
