Free-cooling utilizes cool outdoor air to lower the temperature of indoor spaces or cooling media (such as water or glycol), instead of relying solely on energy-intensive compressors and traditional air conditioning. The result: lower electricity consumption and reduced operating costs.
When the outdoor temperature is lower than the temperature required inside the building or within the cooling circuit, free-cooling systems use the external air as a natural source of cooling. This limits the operation of chillers, thereby reducing electricity usage and lowering the overall system's maintenance expenses.
It is most effective when the outdoor temperature is significantly lower than the indoor requirement or the return fluid temperature. In practice, it is most efficient at outdoor temperatures up to approximately 16°C. Above this threshold, compressor support is usually required.
Yes. In Poland, "air-sourced" cooling is available for a significant part of the year. A well-designed system can cover over 40–50% of the annual cooling time (depending on the facility type and required temperatures). The greatest gains are achieved during spring and autumn, as well as during cool summer nights. These benefits are even more pronounced for buildings with high cooling demands, such as server rooms or offices with high densities of computer workstations.
Energy Savings: Reduction in energy consumption by up to 80% annually compared to systems without free-cooling.
Operational Efficiency: Reduced compressor workload leads to lower bills, longer equipment lifespan, and fewer breakdowns.
Rapid ROI: In industrial applications, the return on investment can occur within 2–3 seasons.
Sustainability: A lower carbon footprint due to reduced electricity demand.
Server Rooms / Data Centers: Constant 24/7 demand; compressors can often be turned off for months at a time.
Office Buildings / Shopping Centers: High internal heat gains; effective use of night cooling modes during summer.
Manufacturing Plants: Indirect free-cooling via dry-coolers or towers; in autumn and winter, it is often possible to shut down chillers completely.
Free-cooling is less effective during hot, humid summers and in facilities without significant internal heat gains (where there is no excess heat to remove). Its effectiveness strictly depends on the quality of the automation system and the correct sizing of air handling units and heat exchangers.
1.Direct Free-cooling
Cool outdoor air is supplied directly into the building or ventilation system instead of air cooled by a refrigeration circuit.
Example: An Air Handling Unit (AHU) with a free-cooling function. When the outdoor temperature drops below the indoor setpoint (e.g., at night), the automation system closes the heat recovery exchanger (recuperator) and opens its bypass. The mechanical cooling is switched off, and fresh, cool outdoor air is directed into the rooms.
Process: Before entering the interior, the air undergoes basic processing (filtration, and de-humidification or humidification if necessary) to maintain air quality and comfort.
Requirement: It requires an AHU equipped with a proper mixing box and automation that monitors temperatures in real-time.
2. Indirect Free-cooling
This variant involves cooling an intermediate medium (e.g., water or a glycol solution) using outdoor air. The cold outdoor air does not enter the rooms directly; instead, it cools the refrigerant flowing through an additional heat exchanger.
Process: When the outdoor temperature falls below the required level for the medium (e.g., below its return temperature), the valves redirect the fluid through the free-cooling exchanger. The fluid is cooled without compressor involvement and then supplied to the standard cooling coil in the AC system.
Application: Widely used in chilled water systems. It can operate even at slightly higher outdoor temperatures, as long as they remain lower than the return temperature of the cooling medium in the installation.