Climate Change: Which Cooler is Suitable for Where?

With the Earth warming in recent years, even parts of the globe that previously did not require cooling systems now find themselves in need of such systems, while other areas have become so hot that no cooling system is effective. The question arises: what system is effective in these conditions and for where? Cooling systems around the world are categorized into several types; they can be divided into water coolers, gas coolers, natural coolers, and chillers (chillers are not discussed in this article). Each system has its own advantages and disadvantages, and some methods can only function acceptably in certain regions. In simple terms, cooling systems follow the laws of thermodynamics; according to these laws, heat transfer occurs naturally from a warm environment to a cold one, and work must be done to reverse this process. Refrigerators operate exactly based on this principle. Natural coolers are the oldest type of cooling systems, and Iranians have been pioneers in this method globally with windcatchers, making it possible to live for years in the very hot regions of the Iranian plateau. Essentially, in ancient times, Iranians used wind power to cool their homes. Windcatchers were built above water reservoirs, basements, or pools. In homes, airflow was transferred inside through the windcatcher. In some mosques on the edge of the desert, such as the old mosque in Ardakan and the Jameh Mosque of Firuzabad in Yazd province, the windcatcher opening is located directly above the prayer niche, allowing airflow to enter various parts of the building. In the windcatcher of the Dowlatabad Garden, the airflow, after entering, passes over a small stone pool and fountain before moving to other rooms. The room under the windcatcher, which contains the pool and fountain, is octagonal and has multiple doors. When cooling is needed in any part of the house, the door to that section is opened. In windcatchers, wind pressure is used to draw fresh air into the building, and the reaction force, i.e., suction, is used to expel warm and polluted air. In other conditions, airflow in windcatchers occurs due to temperature differences. When there is no wind outside the house, this method operates effectively. During the day, the southern part of the windcatcher becomes warmer due to sunlight, causing warm air from inside the house to flow out through the southern part of the windcatcher. As air is drawn in from below, a slight vacuum is created, and airflow enters the windcatcher and the house from the northern section. The drawback of the windcatcher system is the infiltration of dust and insects. Water coolers are suitable for hot and dry areas and are practically ineffective in hot and humid regions or where there is excessive heat. Nevertheless, the electricity consumption of this type of cooler is lower than that of other types, and it is also cheaper. The mechanism of these coolers is simpler, but they have high water consumption, and it can be said that given the water scarcity crisis in Iran, these coolers exacerbate the crisis (each water cooler consumes between 20 to 45 liters of water per hour on average, depending on its capacity). In this device, the heat inside the cooler is used for the evaporation of the walls' water, cooling the temperature inside the cooler. The internal fan of the cooler also transfers the cool air into the house. Water coolers are usually produced in two types: straw wall and cellulose wall. These coolers lose their effectiveness at temperatures above 40 degrees and can turn into a breeding ground for germs and pollution if the straws are not replaced. In cellulose type, the wall pad changes from straw to cellulose pads. This type of water cooler has a greater water absorption capacity and allows less dust and pollution to pass through. These coolers can perform better in warmer conditions and have relatively good performance up to 45 degrees. Gas coolers operate similarly to refrigerators. These coolers perform well at temperatures above 45 degrees and can be effective in southern Iran, where some days reach temperatures above 50 degrees due to rising heat. In some models, these coolers can even purify the indoor air from pollution and eliminate germs. Additionally, they can reduce indoor humidity in humid environments. Gas coolers are produced in various models. One example is portable models. To transfer heat from these coolers to the outside environment, special hoses must be used. These coolers have an opening for cool air flow and a hose for expelling warm air outside the house. This portable model is usually cheaper but does not have the necessary efficiency compared to other models and takes up a lot of space. Window gas coolers are another example of these devices. Half of this cooler is inside the house, and the other half is outside through windows. This model emits cold air from the inside and warm air from the outside. Wall-mounted gas coolers have good efficiency. These coolers take up less space inside the house. The compressor of this type of gas cooler is placed outside the house. Essentially, these coolers have two main parts; one part is placed on the wall of the house, and the other part, which is the compressor, is installed outside the house. These two parts are connected by pipes. These coolers generally have higher efficiency than other models. Additionally, because the compressor is located outside the house, they produce less noise inside. However, wall-mounted gas coolers are more expensive than other models. Smart gas cooler models that have inverters adjust and optimize their compressor speeds based on the house temperature. Therefore, they consume 10 to 50 percent less energy. Gas coolers with a capacity of three thousand watts can cool an average room during peak heat hours. This figure is significantly higher than the capacity of a water cooler, which ranges from 500 to 900 watts, and also has higher consumption. The lower you set the temperature of gas coolers, the more electricity consumption increases. The temperature at which both electricity is consumed efficiently and the room air is bearable is between 24 to 26 degrees Celsius. The cooling capacity of gas coolers is based on the British unit, which is more commonly used in Iran, BTU. At high temperatures, a figure between 500 to 1000 BTU should be considered for each square meter. This figure in areas with less heat is between 200 to 500 BTU. A 30-square-meter room in very hot areas requires about 30,000 BTU per hour, which is about 2.5 kilowatt-hours. With this approximate figure, you can calculate your electricity bill based on the consumption rate per kilowatt-hour.