Evaporative cooling, or how to use water to cool the air

Sometimes, we need a cooling system to help us cope with the hottest months of the year. However, we don’t want (or can’t) install complex equipment or make significant investments, especially if we live in a rented flat. A good solution in these cases is to opt for an evaporative air cooler.

How does evaporative cooling work?

As its name suggests, evaporative cooling is a system that relies on the evaporation of water to cool a space. It can be used in homes and larger areas, such as industrial warehouses or factories. It is particularly effective in places with low relative humidity.

An evaporative air cooler works by using the action of water. The device draws hot air from outside and passes it through filters or containers that hold cold water or ice. Once the air is cooled, it is blown into the room by fans.

This process mimics a natural phenomenon: in areas with abundant vegetation and high humidity, plants absorb water from the soil and release it through their leaves via evaporation, which helps to humidify and cool the environment. The human body also uses this principle: sweating lowers our body temperature.

An evaporative air cooler has two functions: it cools and usually increases the air humidity. Therefore, they are very useful in places where air humidity is low, enhancing comfort and well-being. Furthermore, they work best in well-ventilated spaces with air flow. This means that using these systems is often combined with good ventilation practices.

The benefits of evaporative cooling

The main advantages are basically summarised in three points: efficiency, energy savings, and low environmental impact. However, we can go into more detail:

• Low energy consumption: generally, it requires less energy than other cooling systems, such as traditional air conditioning.
• Natural refrigerant: using water to cool the air spares the need for gases harmful to the environment (unlike traditional air conditioners).
• Reduced CO2 emissions: by not using fossil fuels, the only emissions are linked to the electrical energy used for operation. If this energy comes from renewable sources, the device is even more sustainable.
• Low installation and maintenance costs: many devices are small and portable, requiring no complex installations.
• Financial savings: benefits arise from the low cost of installation and maintenance as well as its energy efficiency.
• Air humidification: this is very beneficial in areas where low humidity can cause health issues or material damage.
• Compatible with ventilation: it is not necessary to close off spaces for it to work effectively; instead, air circulation enhances its use.

In what contexts is it most efficient?

An evaporative air cooler can be used in homes, commercial spaces, offices, factories, and public buildings like hospitals or schools. For domestic use, the devices are usually small and portable, while they are larger and more powerful for industrial use.

Generally, they work better in dry climates for two reasons: they are more efficient and help increase air humidity. In these conditions, they can lower temperatures by 15ºC to 20ºC.

In parts of the world with long, dry, and hot summers (such as some areas of the US and Australia), this system is commonly and widely used. In Spain, as explained by the Ministry of Health, it is mainly used in industries where cooling is needed at a low cost. For example, in poultry or pig farms, where it reduces animal mortality due to heat stress, or in industries where increased humidity is beneficial, like textiles or paper.

It is also very practical in places where fixed installations are not feasible or desired, such as rental apartments, bungalows, or second homes used only during the summer months.