Optimisation of machine cooling systems that use water as a refrigerant

Gebrüder Schwarz GmbH | Sempact AG

Gebrüder Schwarz GmbH from Rottweil-Neukirch modernised its machine and tool cooling system. It reduced power consumption by implementing a variety of measures. Further emissions were reduced by changing the coolant from R134a to water.

The Schwarz factory

Participating companies

Gebrüder Schwarz GmbH/Sempact AG

Project location



Plastics technology

Technologies used

Optimisation of the cooling system: free cooling or adiabatic cooler and cooling with water instead of R134a (120 kW)

Energy efficiency

Reduction of energy consumption (estimated): 300,000 kWh/yr (electric)                                                           

Additional heating oil consumption due to the elimination of heat recovery (estimated): 39,510 kWh/yr (thermal: petroleum)

CO2 savings

Via electricity savings: 150 t CO2e/yr
By changing R134a to water: 59.5 t CO2e/yr



Payback period

4.3 years

Funding programmes

Federal funding for energy efficiency in the economy, module 4, grant (BAFA): €105,133 (approximately 34% of the investment costs)


Gebrüder Schwarz GmbH in Rottweil-Neukirch is a modern technology company in the field of plastics and tool technology. In July 2021, with the support of the energy consultancy company Sempact AG, the company commissioned a new cooling system for machine and tool cooling.

A chiller with two compressors was previously in operation at Gebrüder Schwarz GmbH to provide cooling. The cooled water had to be pumped from the attic to the basement and distributed from there to the injection moulding machines. A heat recovery system for ventilation was connected to the cooling system. The energy consumed during the cooling process was measured for five and a half days in order to evaluate its efficiency. The measurement showed an intermittently high level of energy consumption due to the heat recovery. This analysis was the basis for optimising the cooling system.

Energy was able to be saved by simply by changing the location of the recooler (closer to the machines that need cooling), as the average ambient temperature around the recooler was reduced by at least five degrees Kelvin. The recoolers are operated as free coolers or adiabatic coolers in order to increase the efficiency of the overall system. Approximately 5,300 hours of free cooling operation and 900 hours of mixed operation are expected each year. Chillers that have water as a refrigerant are now being used as part of the cooling process Using R718 (water) as the refrigerant instead of R134a (a hydrofluorocarbon) reduces the global warming potential (GWP) from 1,430 to zero. The new cooling system thus reduces electricity consumption and costs, as well as GHG emissions. The reduction of the individual parameters was forecast; the actual savings can then be determined after a certain period of operation.

Project + TEAM Tool Cooling


Adiabatic machine and tool cooling that uses a natural refrigerant can be used in manufacturing industries that generate process heat that needs to be removed. This is especially true for the plastics industry, but also for other industries, such as metal processing. In addition, the units can be used to cool server rooms and control cabinets and for air conditioning in buildings.


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Pictures: Gebrüder Schwarz GmbH