In what is believed to be one of the largest projects of its kind in Europe, high efficiency heat pumps based on carbon dioxide as a refrigerant are being installed at a Respond! housing project in Dublin.

Some 130 award-winning Sanyo ECO CO₂ units are being installed by Crystal Air Limited of Clane, County Kildare, working in close collaboration with consultant Brendan Keaveny of Keaveny Engineering Services Ltd. 

The project includes the use of two Sanyo Gas-powered Heat Pump systems, Electric VRF and Sanyo’s air processing fresh air heat recovery units. 

The ECO CO₂ units will provide low cost, low carbon heating and hot water for the social housing apartments at Tallaght, Dublin, which are designed to provide high quality living accommodation for traditional families, one parent families, the elderly, the homeless and disabled people.  

Respond!, established in 1982, is Ireland’s largest non-profit housing association.

The high efficiency ECO CO₂ units were chosen to help the project achieve the demanding energy efficiency standards required for the building and the requirements of Part L of the Building Regulations. The solution fully conforms with the Sustainable Energy Authority of Ireland’s renewable energy technologies requirement, greater than 10kWh/m²y.

Using carbon dioxide as a refrigerant gives the ECO CO₂ a further advantage over other vapour compression heat pumps on the market that use potent greenhouse gasses as refrigerants. Carbon dioxide, a natural substance, has a global warming potential of 1 compared with several thousand for some HFC-based refrigerants. It is therefore much more environmentally friendly.

In addition, due to the unique operating characteristics of carbon dioxide, the ECO CO₂ can deliver hot water at up to 65deg C without the use of an inefficient electric booster heater, required by competing systems.

A number of makes and types of heating systems were considered for the project. However, the Sanyo ECO CO2 units were considered to deliver the greatest end user and environmental benefits - in terms of efficiency, operating temperatures and proven performance.

The inverter-controlled systems – from 4.5 to 45kW capacity – consist of an outdoor heat pump unit, containing the compressor and CO₂ refrigerant circuit, which supplies hot water to a thermal store.

The thermal store can vary in size according to system capacity. The ability of the ECO CO₂ to connect to third-party thermal stores gives flexibility in application, and enables it to become part of a complete integrated solution.

Stored water at 65°C can be used for domestic hot water or washing and can be directly connected to radiators or an under floor system for space heating. The system can also control external devices such as wood burners, solar hot water systems, and biomass boilers – enabling the creation of flexible so-called bivalent systems for use in high efficiency, future-proof sustainable buildings.

At the heart of the system is Sanyo’s ground-breaking carbon dioxide-based compressor, the world’s first two-stage rotary compressor operating on R744.

The compressor is engineered to accommodate the high working pressures generated by carbon dioxide. The whisper-quiet unit operates at 45db(A) and is highly compact, saving significantly on the use of raw materials.

The units at the Tallaght development are now being commissioned prior to the first residents taking up occupation. 

Domnick Ward of Crystal Air said: “It is an outstanding project and makes full use of the exceptional capabilities and performance of the ECO CO₂ system. I have no doubt that, with energy prices continuing to rise for the foreseeable future, the product could become a mainstream solution.” 

Brendan Keaveny of Keaveny Engineering Services said: “Energy efficiency was a key aspect of the building specification. Selection of the Sanyo solution enabled us not only to meet the requirements but exceed them, and ensure a low cost, high quality living environment for residents.”

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