Free cooling is a simple yet effective way to reduce the energy consumption of buildings.
Free cooling can save up to 90% of the energy used by traditional air conditioning systems.
The key to successful free cooling design is to understand the principles of free cooling and how to apply them in practice.
Free cooling is based on the concept of using outside air to cool the building, which can be achieved through natural ventilation, evaporative cooling, or air-side free cooling.
The ideal temperature for free cooling is between 10°C and 30°C, outside air temperatures within this range can be used to cool the building.
Cooling Systems
Free cooling is a great way to reduce energy consumption in cooling systems. It uses outside air to cool the process fluid in a heat exchanger, making it an ideal alternative to chillers.
A dry cooler, also known as a free cooler, is a type of cooling system that uses outside air to cool the process fluid. These systems are perfect for businesses seeking energy-efficient and low-maintenance cooling solutions.
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You can combine a dry cooler and a chiller into one unit, known as a hybrid cooling system. This system takes advantage of the free cooling potential of the ambient air when the outdoor temperature is low enough to provide sufficient cooling.
Here are some key benefits of hybrid cooling systems:
- Reduces energy consumption by taking advantage of free cooling
- Provides precise temperature control
- Ideal for environments with fluctuating cooling loads
In a hybrid cooling system, a three-way valve redirects process fluid to the dry cooler when the outdoor temperature is lower than the process temperature set point. When the outdoor temperature rises above that set point, the valve switches back to the mechanical cooling mode, and the chiller compressor is turned on to provide additional cooling.
If this caught your attention, see: Dedicated Outdoor Air System
Operation
Free cooling systems can save energy by using the lower ambient air temperature to cool the water in the system, reducing the need for a chiller and resulting in energy savings of up to 75%.
The installation of an air blast cooler with an existing chiller can achieve this, allowing the system to by-pass the chiller during low ambient temperatures.
Intriguing read: Water Chiller
In winter months, large commercial buildings may need cooling in their interior spaces, even while perimeter spaces may need heating, making free cooling a suitable solution.
Free cooling is not entirely free, as the chiller is still operational, but it can be used generally in the late fall, winter, and early spring in temperate zones.
The percentage of free cooling achieved mid-season is dependent on seasonal temperatures, and partial free cooling commences when the ambient air temperature is 1 °C below the process return water temperature.
In winter, when outdoor temperatures are low enough, the water is chilled solely by the free cooling coil, allowing the chillers' compressors to stop operating and saving significant amounts of energy.
The only electrical power used in winter operation is for fan operation, which can be achieved once the ambient air temperature is 3 °C to 5 °C below the process supply water temperature.
On a similar theme: Sol-air Temperature
How a Dry Cooler Works
A dry cooler, also known as a free cooler, is a cooling system that uses outside air to cool the process fluid in a heat exchanger. This system is ideal for businesses seeking energy-efficient alternatives to chillers.
The hot process fluid, typically water or a water-glycol mixture, is pumped through a heat exchanger, also called a coil, located outdoors. This coil is where the magic happens, allowing the heat from the process fluid to transfer to the air.
A fan blows ambient air across the coil, causing the heat transfer to occur. This process requires a minimum difference of 10°F (~5°C) between the process fluid and the ambient air.
Here's a step-by-step breakdown of how a dry cooler works:
- The hot process fluid is pumped through the coil.
- A fan blows ambient air across the coil.
- The heat from the process fluid transfers to the air.
- The cooled process fluid is then pumped back into the facility.
By using outside air to cool the process fluid, dry coolers can be a more energy-efficient option for businesses. They're especially suitable for climates where ambient temperatures frequently dip below process fluid requirements.
On a similar theme: Thermic Fluid Heater
Cooling Methods
Free cooling is an energy-efficient way to cool your facility, especially in climates where ambient temperatures frequently dip below process fluid requirements. It's a low-maintenance alternative to chillers that can be ideal for businesses seeking to reduce their energy consumption.
There are three ways to use free cooling: dry coolers, free cooling systems, and outside air damper systems. Dry coolers, also known as free coolers, use outside air to cool the process fluid in a heat exchanger.
Dry coolers have a straightforward and sustainable principle: the hot process fluid is pumped through a heat exchanger located outdoors, and a fan blows ambient air across the coil to transfer the heat to the air.
Free cooling systems, on the other hand, use a modulating three-way valve connected to the building load or load side of the chilled water system, the chiller system, and the free cooling system. This allows for highly reliable and surprisingly simple operation.
For another approach, see: Water Heat Recycling
In an integrated system, there is a water coil sandwiched directly against the normal copper tube/aluminum fin refrigerant coil being used as the condensing surface of the air-cooled chiller. This setup allows for maximum savings to be achieved.
Here are the different operating modes of free cooling:
- Free Cooling: The compressor of the chiller system remains off, completely saving the cooling energy normally required.
- Mid-Range or Pre-Cooling: The three-way valve begins to open to the free cooling coils between 2°F (-16 °C) and 4°F (-15 °C) below the chilled water set point.
- Winter Operation: The system can achieve 100% of its capacity with the free-cooling coils when the temperature reaches the range between 5°F (-15 °C) and 9°F (-12 °C) below its chilled water set point.
- Limitations: The system will throttle back to avoid overcooling and maintain set point when cooling demand is exceeded.
Advantages and Efficiency
Free cooling is an excellent way to save energy, and it's not just a theoretical concept. In the UK, the government made a concession in 2013 to exempt data centers from the Carbon Reduction Commitment (CRC) and allow them to produce their own Climate Change Agreement (CCA).
The UK government's move is in line with the European Commission's goal to reduce EU greenhouse gas emissions by 40% by 2030. This shows that free cooling is a serious solution to a pressing environmental issue.
Cooling data centers or server rooms requires a lot of energy, which is why free cooling can be an ideal solution to save energy. In fact, dry coolers, also known as free coolers, are a type of cooling system that uses 'free' outside air to cool the process fluid in a heat exchanger.
Here are some key advantages of direct free cooling:
- Maximum energy efficiency thanks to the direct use of Free Cooling
- Excellent system scalability – no hydraulics (pipework, pumps, valves)
- Lower investment costs compared with conventional Indirect Free Cooling systems
- Much lower energy requirement than all conventional systems
Dry coolers are ideal for businesses seeking energy-efficient, low-maintenance alternatives to chillers, especially in climates where ambient temperatures frequently dip below process fluid requirements.
Design and Implementation
Free cooling systems can be designed to work with existing air conditioning systems, using the outside air as a heat sink to cool the building.
The simplest form of free cooling is evaporative cooling, which uses water to cool the air.
A well-designed free cooling system can reduce energy consumption by up to 70% compared to traditional air conditioning systems.
Free cooling systems can be implemented in various configurations, including hybrid systems that combine free cooling with traditional air conditioning.
A hybrid system can provide cooling during periods of high demand, while using free cooling during periods of low demand.
By integrating free cooling with existing systems, building owners can reduce their energy bills and carbon footprint.
Expertise and Experience
We've already accomplished numerous Free Cooling projects around the world, so we have a deep understanding of the requirements of different countries and continents.
STULZ has developed scalable air conditioning systems that are perfectly adapted to the specific parameters of your location, providing reliable, individualized, and precise solutions.
It's crucial to check which type of Free Cooling best matches your needs, requirements, and intended use, as some solutions offer greater potential savings than others.
Indirect Dynamic Free Cooling from STULZ offers the greatest potential savings, making it a highly beneficial solution for many applications.
Frequently Asked Questions
When can free cooling be used?
Free cooling can be used when outside air temperatures are low enough to provide sufficient cooling without the need for compressors. This typically occurs when the temperature drops to a level that allows for efficient cooling.
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