Drives & Controls September 2022

32 n ENERGY EFFICIENCY September 2022 www.drivesncontrols.com Change to CO 2 is just what the doctor ordered I t is becomingmore common to use carbon dioxide (CO 2 ) as a refrigerant for cooling and heating systems. This is a result of pressure to phase out synthetic HFC (hydrofluorocarbon) refrigerants which are potent greenhouse gases with high global warming potential (GWP) and long lifetimes. Unlike the fluorinated gases, CO 2 is a naturally occurring gas that is low cost, safe, and doesn’t affect the environment. The European Union’s F-gas regulations and Eco Design directive require users to shift to low-GWP refrigerants such as CO 2 (R744) and to high-efficiency compressors that use VSDs to increase their cooling capacities and raise their Coefficients of Performance (CoPs). St Olav’s Hospital in Trondheim, Norway, has been retrofitted with a CO 2 -based system to reduce its carbon footprint and impact on the environment, as well as saving energy. A Norwegian refrigeration specialist, Sinop Technoblock, designed and implemented the installation which includes a laboratory, an on- site hotel and a canteen. It chose a controller from the Danish supplier Reftronix to ensure that the system operates with optimal efficiency under all conditions. Modern compressors usually incorporate high-efficiency permanent magnet motors controlled by variable-speed drives. The Reftronix controller adjusts the speed of the hospital’s compressors in combination with VSDs from theWelsh drives-maker, Invertek. Varying the speed the compressor motors makes themmore energy-efficient than the start/stop systems typically found in systems using HFC refrigerants. The VSDs control the speed of the compressors depending on temperatures and other conditions. The controller measures temperatures and pressures, calculates the optimal performance, and adjusts fan speeds and the opening of electronic valves. The combination of the controllers and VSDs is said to ensure precise control of the refrigeration process, as well as providing remote access to live data, alarms and settings. According to Reftronix’s general manager, Henrik Christensen, the combination ensures that the refrigeration systems are as accurate and efficient as they could possibly be. The St Olav’s installation is using ten of Invertek’s 400V Optidrive Eco VSDs, including four 2.2kW, four 1.2kW, one 5.5kW and one 11kWmodels. The drives are connected to the controllers via Modbus, allowing them to be configured via Reftronix’s online portal. Any alarm or trip warnings are highlighted via aWeb page, which also makes the status and live data available remotely via the cloud. “The controller user interface is aWeb page whichmakes it easy to commission and provides a good graphical overview of the runtime conditions,”explains Sinop Technoblock’s founder, Kjell Robert Overlev.“All of the controllers are on the same Ethernet network. This means you can link the controller Web pages, making it possible to look at a pack. With the press of a button, you can view the cold room controller. There is no need for a systemmanager or front end which saves a lot of upfront cost. “The new refrigeration systems at St Olav’s Hospital are a great demonstration of how CO 2 HVAC-R systems are not only helping reduce energy use and creating greater efficiencies, but are supporting the work in reducing harmful emissions and climate change,”he adds. Big refrigeration users, such as retailers, are already converting to CO 2 systems to cut energy use andmeet tighter emission regs. n A Norwegian hospital has upgraded its cooling systems to using environmentally friendly CO 2 as a refrigerant. VSDs are being used both to control the compressors and to save energy. Variable-speed drives control the speed of the hospital’s compressor motors accurately to optimise their performance and cut energy use