Water (R718) – the natural safety refrigerant

The right choice of refrigerants is an ongoing issue in the industry, especially after the European F-Gas Regulation took effect on 1 January 2015, further restricting the use of HFCs (hydrofluorocarbons). The eChiller uses water as a refrigerant, therefore making it the optimal solution – environmentally and economically.

Water as a refrigerant is the unrivalled alternative. None of the environmental and safety regulations relating to the current and future operation and maintenance of refrigeration units apply to water (R718). That lowers the equipment, operating and maintenance costs, secures your investment, and has a positive effect on the future of our global climate.
After a lifetime of use in the eChiller, the water contained in its closed-loop system can be released back into the environment.

There is simply no better solution – economically or environmentally – to your cooling applications.

Water as a refrigerant – past and present

Since the end of the 17th century, water has been used industrially on a significant scale as a refrigerant in absorption systems, initially together with sulphuric acid and later with lithium bromide. Water is also frequently used in adsorption processes, especially because of its outstanding evaporation enthalpy and environmental friendliness.

The use of water for stream blasting refrigeration, by contrast, is a niche application. Until now, water as a refrigerant in compression chillers has not been economically viable. Despite numerous attempts, series production readiness remained beyond reach.
But Efficient Energy achieved this quantum leap. Thanks to a revolutionary approach and many years’ development work, the eChiller is now available as a series product!



In refrigeration technology, water (H2O) is referred to as R718 because of its molar mass of approx. 18 g/mol.

Water - colourless, odourless, tasteless and non-toxic

In addition to these properties, water is also a very stable molecule with neither greenhouse nor ozone-depletion potential. When water is used as a refrigerant, there is another important property that makes its unrestricted use possible: water is non-flammable. When used in a refrigeration system, water occurs in liquid and gaseous form. The thermodynamic cycle takes place in vacuum.

The figure on the right-hand side shows the vapour pressure curve of water compared to a selection of customary refrigerants. While CO2 (R744) has the highest vapour pressure of all refrigerants, in conventional cooling applications above 0° C the vapour pressure of water lies between 10 and 140 mbar. Water at temperatures below 0° C is not generally used in compression refrigeration systems.

Water has further outstanding properties

The density of liquid water in vacuum is 1,000 kg/m3. This compares with a density of approx. 20 g/m3 in gaseous state. Due to this enormous density ratio and, consequently, the low volumetric cooling capacity, compressors with high refrigerant mass flows are needed (turbo compressors). Apart from that, water as a refrigerant has excellent material and thermodynamic properties. In the environment, water for refrigeration technology is readily available in adequate quantities.

Physical advantages

  • Low pressure level
  • High evaporation enthalpy

Chemical advantages

  • Chemically stable
  • Non flammable
  • Natural
  • Colourless

Physiological advantages

  • Non toxic
  • Odourless

Economic advantages

  • Highly efficient
  • Available at "no cost"
  • Not legally regulated
  • Amply available in nature

Environmental advantages

  • Environmentally friendly
  • Sustainable
  • ODP = 0, GWP = 0