The use of HC-744 (CO2) as a refrigerant in both commercial and residential continues to be discussed, tried, and used. And while it is being successfully used in subcritical applications in the United States, it is more of a challenge in transcritical situations because of demanding compressor technology and high pressures. The United Kingdom (UK) office of Sanyo Air Conditioners recently issued two case histories showing the refrigerant being used for heat pumps in commercial applications.

CAT

The Centre for Alternative Technology (CAT) in Machynlleth, Wales, has installed a Sanyo air-source, CO2-based heat pump as part of its sustainable technology program.

The center’s David Hood said, “Heat pumps have been around for some time, but the technology has been evolving to make it more energy efficient. The Sanyo system uses an inverter-driven compressor, which is more responsive and energy efficient than previous versions. The system also uses carbon dioxide as the refrigerant. It has a major environmental advantage over other vapor compression heat pumps.”

He added, “Carbon dioxide also has the potential to operate at higher temperatures, which fits in better with the way we use heat in our homes. There are currently only a few heat pumps of this type installed in the UK, and we are excited to have the opportunity to investigate it at CAT.”

The center is using an ECO CO2 system from Sanyo to heat one of its buildings at its campus. CAT technicians will monitor the system to see how well it performs under a range of climatic and occupational conditions.

The system is being used as a demonstration plant for the centre’s heat pump installer program, and as part of its MSc in Renewable Energy in the Built Environment course.

The heat pump has been donated to CAT by Sanyo and distributor Oceanair (UK) Ltd. Tony Evanson of Oceanair said, “The Sanyo carbon dioxide system is pioneering technology, and is stimulating a great deal of interest. The fact that it combines high-efficiency inverter control with a low or negligible GWP [global warming potential] refrigerant such as carbon dioxide makes it unique in the market.”

Sanyo’s Graham Wright, who heads up the company’s heating division, said, “There are now several hundred successfully installed in the field, in applications ranging from modern homes to 16th century priories and castles.”

CAT is an independent organization that deals with technology issues in relation to energy, sustainability, pollution, and climate change.

CARE

A care home in Nottingham, UK, is using CO2 heat pumps from Sanyo to “extract renewable energy from the air to reduce its heating bill and cut carbon emissions,” according to a case history report.

As part of the drive to improve efficiency and environmental standards at Beechdale Manor Care Home, there was a requirement that 10 percent of the energy used by the building should come from renewable sources.

The mechanical and electrical contractor specified an ECO CO2 system.

Tony Boughey of the contractor Drayton Beaumont said, “Our engineers attended a dedicated training course organized by the distributor Oceanair UK and Sanyo. It was excellent and provided a solid grounding in the technology and how to apply it.”

The course covered both the theoretical and practical aspects of carbon dioxide-based heat pumps, and included hands-on instruction on installation and commissioning.

There are five Sanyo ECO CO2 9-kW systems installed at Beechdale Manor, delivering a total of 45-kW heating capacity.

The system is able to deliver hot water at up to 65°C (149°F) without the use of an electric booster heater, officials said.

In this installation, the heat pump is being used to preheat water to a lower temperature before being fed to gas-fired boilers for use in the home’s domestic hot water supply, for use in washing, bathing, and showers.

Commenting on the project, Evanson of Oceanair said, “We have been involved with a number of very successful applications using Sanyo CO2 heat pumps with AVC tanks, and we have been very impressed with their combined performance. The recovery rate is exceptional.”

Boughey said, “The installation went smoothly and according to plan. We would definitely use the Sanyo system again and recommend it to others in the future. It’s well engineered and enables a quite challenging renewable target to be met.”

Publication date: 04/04/2011