Climate change and increasing heat waves in cities around the world have led scientists and engineers to develop more efficient and sustainable cooling solutions. One of the most promising developments has been the development of passive cooling systems, which allow the temperature of buildings to be reduced without the need to use electricity, which represents both an economic and environmental improvement.
Passive cooling: a new era of energy efficiency
Researchers at Stanford University have taken an important step in this direction with the development of a system that uses reflective panels installed on the roofs of buildings dissipates heat from the inside to the outside. This system, based on the principle of passive radiative cooling, promises a reduction of internal temperature by up to 5°C, which would significantly reduce energy consumption for air conditioning systems, especially in urban areas.
This advance could be decisive, since, in the United States alone, it is estimated that 15% of the electrical consumption of buildings is used for cooling systems. The implementation of these systems would allow a significant reduction in environmental impact and the costs associated with air conditioning.
How passive radiative cooling system works
The passive cooling system developed by Stanford is based on the ability to reflect solar radiation and dissipate the heat accumulated on the surface of buildings through a window of transparency in the atmosphereThis allows the accumulated heat to be radiated directly into outer space without heating the surrounding environment.
The key component of this system is the reflective panels, made from a 1.8-micron layer of silicon dioxide and hafnium oxide on a thin sheet of silver. This combination of materials acts as both a radiator and a mirror, reflecting infrared radiation at specific wavelengths that pass through the atmosphere without being absorbed by the air surrounding buildings.
In addition, the system has been tested in direct sunlight conditions, proving that it can reduce the temperature of a building by up to 5°C. This makes it a ideal solution for urban areas, where heat islands exacerbate temperatures during the summer months.
Using ancestral systems as inspiration
One of the most interesting features of passive cooling is that, although it is based on modern technologies, some of the principles used already existed centuries ago. For example, systems inspired by buildings of the Ancient Egypt use ventilation towers to capture air and cool it by evaporating water. In other regions of the Middle East, so-called malqafs They allowed adiabatic cooling by taking advantage of air and water currents.
These types of solutions are still viable today and are being modernized. One example is TerraCool, where it is used terracotta using a natural evaporation system to cool buildings without energy consumption. Likewise, the TerraMound project developed in the Bartlett College of Architecture combines clay and geometric design to maximize airflow, creating structures that cool without the need for electricity.
Evaporative cooling: another viable option
In regions with drier climates, other technologies such as evaporative cooling have also proven to be very useful. This method uses the evaporation of water to generate a decrease in ambient temperature. Cities such as AhmedabadIn India, passive systems based on this principle have been implemented in advanced research centres to improve air conditioning.
Unlike traditional air conditioning, which consumes large amounts of electricity and emits greenhouse gases, these systems use nature to reduce the temperature, taking advantage of a resource as basic as water.
For example, the Pearl Academy in Jaipur, India, employs a design inspired by traditional lattices that, together with an indoor pool, generates fresh air currents that cool the building without the need for electricity.
The technological evolution of passive systems
Passive cooling is not only based on old principles, but is constantly evolving, combining Advanced technology with innovative materials. Examples such as Hydroceramics, recently developed, use the porosity of ceramics and hydrogel to absorb and store water which then evaporates on hot days, cooling the surrounding air.
Another promising technology is the airgel used in projects such as the one developed in the MITThis ultra-light material allows for optimized evaporative cooling without consuming electricity. Aerogel-based devices can reduce internal temperatures by up to 9,3°C, providing an efficient and clean alternative to conventional systems.
Furthermore, as they do not require large amounts of energy, these systems are applicable in areas with scarce resources, especially in developing countries or isolated communities.
The implementation of passive systems in modern architecture not only results in energy savings, but also in more sustainable buildings and a better quality of life for the inhabitants.
As climate change continues to intensify, it is essential to find alternatives to air conditioning that do not deplete natural resources or worsen the environmental situation. Passive cooling systems are proving to be one of the best solutions and we will surely see growth in their adoption on a global scale in the future.