As temperatures rise around the world, the demand for refrigeration and air conditioning will continue to grow. And this alone will aggravate the crisis situation: the efficiency of modern refrigerators is not so high, and they require a lot of energy, which leads to large emissions and exacerbates the greenhouse effect. Therefore, passive cooling systems are only welcome, and the new invention by MIT scientists promises to increase their efficiency.
A group of scientists from the Massachusetts Institute of Technology occurred Perspective three-layer panel for passive cooling. The technology is said to reduce the panel temperature by up to 9.3 °C compared to the ambient temperature, even in humid climates. For the operation of such a cooling panel, only ordinary water needs to be added. Pretty much water. In hot and dry climates, this must be done more often – once every four days, and in regions with high humidity it is enough to add water once a month.
The installation is similar to a solar panel. Its top layer is an aerogel – a porous, vapor-permeable plastic structure with pores filled with ordinary air. Below the airgel is a hydrogel layer – also a polymer layer but with water in the pores. This layer is similar in many ways to medical hydrogel dressings used to treat open wounds. The third – the bottom layer – is a mirror surface that reflects the sun’s rays back and thus prevents the object to be cooled behind the panel from heating up.
The researchers emphasized that for the first time they combined in one solution long-known principles – this is cooling by the method of liquid evaporation and radiative cooling, when infrared radiation from an object (heat) enters space and does not spread throughout the surrounding space. According to this principle, yes suggested a range of cooling systems that can even keep solar panels running at night. An interesting solution was also the use of an airgel layer as thermal insulation, which additionally protected the cooled object from heating up by the sun’s rays.
The sandwich panel works as follows. The airgel transmits infrared radiation to the hydrogel layer but blocks all other sun rays. Infrared radiation vaporizes the water in the hydrogel layer and the vapor escapes through the airgel. Excess infrared radiation and the panel’s own infrared radiation are radiated into space. Consumable in such a scheme is ordinary water. The prototype showed record-breaking module efficiency, delivering a difference between the ambient temperature and the module of up to 9.3°C.
The proposed solution can be suitable for both houses and containers for transporting and storing food in regions where there are no stable sources of electrical energy. Food pavilion covers can be fitted with similar panels. This helps extend the shelf life of perishable goods by up to 40% in humid climates and up to three times in dry conditions (where the temperature difference between refrigeration and air is greater).
The only obstacle to the commercialization of the development remains airgel, the production of which is still inefficient. Today it is only produced under laboratory conditions in the process of mixing polymer and solvent and then drying it for an extremely long time. Scientists promise to develop a technology to simplify the manufacture of airgel, and then passive refrigerators and passive “boosters” for air conditioning could be widespread.