Journals Proceedings

Abstract

In many large office buildings, hospitals and hotels AC cooling is affected by chilled water generated by a refrigerating plant which rejects its heat to the environment by means of cooling tower water or, increasingly so, by air cooled condensers and adiabatically assisted air-cooled condensers. Hot water for space heating, AC reheat and sanitary purposes is usually provided by a boiler. Using a COAG, the Council of Australian Governments, data base on annual energy consumption per m2 of building, it is shown that significant reductions in the electrical energy, natural gas and cooling water consumption may be achieved when using transcritical CO2 refrigerating systems for building cooling, heating and sanitary hot water, thus saving gas and attendant emissions, and cooling water. It is shown that the specific energy consumption measured in kWh/m2.annum reduces about 30% when retrofitting trans-critical CO2 systems to existing Australian buildings and about 55% in new buildings. These numbers range from about 10% to 50% in hospitals. Supermarkets with all CO2 refrigeration would save about 37%. The natural refrigerant CO2 is non-toxic, non-flammable, low cost and energy efficient. CO2 also has superior heat transfer properties and its GWP=1. As such CO2 is a sustainable refrigerant and will future proof any system against the serious implications of the impending phase down, and ultimate phase out, of the high GWP HFC refrigerants by the amendment to the Montreal Protocol, known as the Kigali amendment, where it was agreed to by the 197 signatories to the Montreal Protocol on 15 October 2,016.