What is free cooling?
Chillers with free cooling
FAQ 06.06.2023The English term "free cooling" is often translated incorrectly to other languages. The correct translation should actually be cooling that costs nothing. Free cooling uses the outside air – the difference in temperature between the inside and outside environment – which does not cost anything, to cool rooms. For situations that require constant cooling year round, e.g. computer centres or process applications, free cooling offers significant energy savings.
In addition to reducing the annual costs of energy, this technology also decreases CO₂ emissions and maintenance costs as a direct result of less effort being required for mechanical cooling. The result is a rapid amortisation of the investment and an extension of the useful life of the chiller as well as its value retention over time.
How do chillers work with free cooling?
Mode of operationFree-cooling units
Unlike other chillers, chillers with free cooling have an additional air-cooled heat exchanger mounted on the air side in front of the condenser. In this heat exchanger, the medium is cooled in the consumption circuit by the outside air to the extent that the temperature outside permits. When the difference between the water inlet temperature and the outside air temperature is at least approx. 2 K, free cooling can begin. The highest power of free cooling is achieved when the temperature differential reaches approx. 10 K. This enables substantial energy savings with short amortisation times.
Mechanical cooling
SummerChillers with free cooling in summer mode
Free cooling is deactivated in the summer and the medium in the consumption circuit is cooled only by the cooling circuit. In this case, the unit operates with a traditional air-cooled chiller with mechanical cooling. Mechanical cooling always requires a compressor, the resulting power consumption leads to energy consumption.
Hybrid cooling
TransitionChillers with free cooling in transition mode
In the autumn, the medium is cooled partly by the free cooling heat exchanger and partly by the compressor. When the outdoor temperature is slightly lower than the water inlet temperature of the chiller, the 3-way valve is triggered, causing the water to be channelled into the additional free cooling heat exchanger. The free cooling portion is a factor of the difference between the outside temperature and the inlet temperature of the medium. This can mean substantial savings in transition mode. The system temperatures and the location of the unit are decisive.
100% free cooling
WinterChillers with free cooling in winter mode
When the temperature difference between the outside air and the medium inlet air is great enough, the medium is cooled only by the free cooling heat exchanger. The cooling circuit is deactivated. The unit is most efficient in free cooling mode, because the only energy required is that to drive the fans. To prevent the medium outlet temperature from falling below the unit's setpoint when the outside temperature is low, the fan speed is gradually reduced when the setpoint is reached. When the unit is operated at very low outside temperatures or when there is a significant difference between the minimum outside temperature and the system temperature, it is best to use a modulating 3-way valve. In this case, the medium at the unit inlet is added to the outlet of the free cooling heat exchanger at the unit, thus preventing the temperature from falling below the setpoint.
When do chillers make sense wit free cooling?
Planning & designNotes on planning and design
Units with free cooling are the best solution when intensive cooling is needed all year round or in the spring and autumn.
Examples:
- Data processing facilities
- Production processes
- Switchboards
- Building with a lot of glass walls / with high internal loads
The system temperatures have to be increased as much as possible to save the most energy. Another way to optimise free cooling is to increase the temperature difference of the medium. Not only does this save drive power for the pump, but also opens up the possibility of starting free-cooling operation earlier. Another benefit of the optimised system temperatures is that a smaller free cooling unit is sufficient. This not only saves initial costs, it also means that the unit requires less space.
Example:
- Required cooling: 500 kW
- Energy costs; €0.2/kWh
- Operating time: 24/7, year round
- Location: Frankfurt am Main
Notes on planning and design
In regard to the cost of investment and operation of the chiller, the new system temperatures can save up to 10,000 Euro in ten years of operation when the above parameters are applied. Take into consideration adjustment of the consumers to modified system temperatures and differentials. Also comply with the limits in regard to dehumidification that may be required.
Free cooling - Products
ProductsChillers by Mitsubishi Electric, Climaveneta and RC IT Cooling
From commercial and hotel applications to IT, industrial and process applications – our chillers offer the perfect solution for every project. Whether you just want to cool, heat and cool or just to heat – you can expect a customised energy-efficient and sustainable solution developed to meet your individual needs. Relying on a wide range of equipment features, we can find the the perfect solution for your specific project.
We support you throughout the process.
ContactsWe focus on service: We are happy to assist you during the planning phase and calculation of projected costs, and to work with you to find the most efficient solutions for your individual projects. We actively advise and support you throughout the process – from planning to well beyond commissioning of your system.
