What is an evaporative cooling system and how does it work?

The evaporative cooling system is aligned with other advancements in cooling techniques, all reflecting a growing emphasis on technological innovation towards energy efficiency and sustainability

However, the truth is early versions of evaporative cooling technology have been known and used since the early days of human civilization. For instance, ancient Egyptians are believed to have used clay vessels filled with water to dispense cooling thanks to placing them in air currents. Additionally, early Iranian architectural feats include the use of towers acting as wind catchers, which also employed wet rags to benefit from evaporative cooling. 

The focus on the enhanced energy efficiency of evaporative cooling systems is crucial today, as estimates for world energy consumption continue rising. In fact, the rise implies that demand levels of 2005 will be increased by 50% in 2030. 

This is by all means an outstandingly unsustainable escalation if cooling technologies continue to rely on carbon-intensive, inefficient methods.  

In this context, let’s go through some of the advantages of  evaporative cooling technology and its most promising applications, including the use in turbine inlet air cooling.

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What is an evaporative cooling system?

An evaporative cooling system is a method of cooling air that employs water evaporation of water. Put simply, this type of technology takes advantage of the fact that water evaporation absorbs heat from its surroundings, causing a cooling effect. 

Also known as adiabatic cooling, the main working principle is using water as a refrigerant as it goes from liquid to gas, via the energy extracted from the air in the form of heat. 

There are at least 2 different approaches to evaporative cooling: 

  • Direct or single-stage: in this case, the air passes through a single phase of evaporation. This is a rather straightforward approach and can be experimented with residential cooling applications in arid or semi-arid climates (so that the air has the capacity to absorb moisture).
  • Indirect or multistage: these systems involve multiple stages of cooling. The first stage means air is pre-cooled, so that its temperature is already low before entering the second stage, where its temperature is lowered further. These systems can overcome some of the limitations of direct technologies, such as the possibility of operating in more humid climates. At the same time, they present an improved efficiency to achieve lower temperatures. 

The working principle of an evaporative cooling system

As we’ve mentioned above, evaporative cooling works based on the heat absorption that takes place during the process of water evaporation. 

The basic concept involves the transformation of liquid water into vapor. This process requires energy, which is extracted from the surrounding air, resulting in a cooling effect. This is why an evaporative cooling is highly efficient in dry or low-humidity conditions, as there is a greater capacity for air to absorb moisture. In humid environments, on the contrary, the air may already be close to saturation, limiting the potential of evaporative cooling.

A typical evaporative cooling system works by using fans to force hot outside air through wet cooling pads. These are moistened using systems that deliver water, such as a water pump. As liquid water transforms into gas, it absorbs heat. This now cooled outcome air can be used for cooling purposes. 

The effectiveness of evaporative cooling is influenced by factors such as ambient humidity levels. In arid climates, where the air is dry, the cooling effect can be substantial. However, Evaporative cooling is energy-efficient and environmentally friendly, making it a popular choice for cooling in certain regions and applications.

In direct evaporative cooling, the result is a cooling down of outcoming air in percentages between 60 and 90 %, being able to reach temperatures of between 10 to 15 °C. However the humidity is high, so that this direct evaporative cooling is typically not employed for residential environments. 

When it comes to multi-stage or indirect evaporative cooling, it can result in temperatures 7 °C lower, with up to 70% less humidity than direct systems.

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The advantages of evaporative cooling

Enhanced energy efficiency and lower costs

Evaporative cooling requires less electricity to operate, using only 10% of the energy needed in mechanical cooling systems.

Evaporative cooling technology uses the same amount of power irrespective of outside air temperatures. In fact, when ambient air is at its highest, the performance and cost-efficiency of an evaporative cooling system increases. This is particularly advantageous compared to conventional refrigerated systems, which typically need more power as outside temperatures rise. 

The low operating costs are directly related to this system’s working principle, as the energy expenses are related to water circulation and fan operations, typically more economical than mechanical air conditioning systems. 

A push towards sustainability

Evaporative cooling systems don't rely on the use of refrigerants, some of which can have negative environmental impacts. At the same time, because of their enhanced efficiency, they represent an eco-friendly option in terms of responsible resource use compared to other cooling systems. 

High versatility

Evaporative cooling is applicable in various settings, including residential, commercial, industrial, and agricultural environments.

Its applications in Turbine Inlet Air Cooling are particularly promising, enhancing the efficiency of power generation by reducing the temperature of the air entering gas turbines. As such, evaporative cooling technology is employed to enhance power plant performance, especially in hot climates.

When is an evaporative cooling system the right choice?

As we’ve mentioned above, evaporative cooling systems are particularly effective in arid or semi-arid climates with low humidity, while their effectiveness can be limited in areas with high humidity.

In addition, evaporative cooling consumes big amounts of water so water availability is crucial. It is also important to mention that the temperatures that can be achieved with evaporative cooling are much higher than with chillers technology. This is the reason why evaporative cooling is limited to very few cases, when the desired power output increase is not more than 3 - 5%.

Some of the current successful applications of evaporative cooling technology include industrial cooling and cooling for commercial facilities (building from these systems’ cost savings for cooling large spaces), temperature control for agriculture and data center cooling. 

Particular attention is paid to the benefits of evaporative cooling for Turbine Inlet Air Cooling (TIAC). The use of a gas turbine evaporative cooler is able to reduce temperature of the air entering gas turbines, thus boosting their efficiency and power output. 

At ARANER, we’ve put our expertise in thermal engineering to work by devising cutting-edge Turbine Inlet Air Cooling systems that make the most of evaporative cooling to improve turbine performance. 

Get in touch with us and learn more about our work and how we can help you use the potential of this technology to our advantage.

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