ACR Journal

CMYK / .ai CMYK / .ai CMYK / .ai acrjournal.uk 23 REFRIGERATION Liam Grice, Lead Electrical Project Engineer at Arctic Circle, said: “Schneider PLCs were used for both the primary and backup controllers for this project. The flexibility of the PLCs meant that bespoke software could be created within Arctic Circle; optimising the unique requirements of the LT Only transcritical booster system. “Resilience was important to the customer so the pack was configured with the N+1 format. The bespoke software meant the number of compressors running at a given time could be limited whilst equalizing the run hours for even wear and automatically starting a spare compressor if a fault occurred. “To aid commissioning and maintenance, 7” colour HMIs were used displaying a full pack schematic with operating conditions. For external communication sharing pack information the MODBUS standard was used.” Exciting year The Arctic Aurora has been extensively system modelled using Arctic Circle’s bespoke software, which has been developed over the course of six years in collaboration with customers, suppliers and partners. It incorporates a verification stage where real time energy consumption of the system is collated and compared against theoretical modelling. This allows for the e–ciency data to be as fluid and true to real life as possible. The refrigeration industry has been pressured to ensure that energy consumption remains low and system verification modelling shows that the pack o—ers a 6% reduction in energy consumption against a typical transcritical system. The industrial specification means the system has been designed with a number of additional provisions to ensure it is fit for purpose. These include additional liquid holding capacity, increased design pressures, extra-large suction accumulators to protect against liquid flood back or condensation within the suction line, full back-up PLC controls and instrumentation and back-up high pressure control valve and flash gas control valve. 2020 is proving to be an exciting year for Arctic Circle, with the appointment of Mike Gittoes as Managing Director at the beginning of April and the celebration of its 35th anniversary this November. The company believes the Arctic Aurora to be an outstanding demonstration of its proven ability to drive innovation in the market. BITZER compressors for transcritical CO 2 applications have been used around the world since 2004 with great success. The six- cylinder units employed in the Arctic Circle application are from BITZER’s ECOLINE semi- hermetic range, designed for high e–ciency transcritical CO 2 projects. Available in 2-, 4- and 6-cylinder versions, they are said to be suitable for use in a wide range of applications, delivering excellent reliability and environmental protection. The latest generation employs a new housing design with optimised suction and discharge gas channels and high e–ciency motors. Key technical features include: • The capacity range covers displacements from 3.3 to 38.3cu m/hr. The six-cylinder units specified by Arctic Circle include the largest in the range, the ECOLINE 6CTE-50K. Powered by two motors, this behemoth has a cooling capacity of more than 81kW (at -10°C), and weighs in at over 240kg. • Energy e–ciency is a key design priority. To help optimise this, the units include: - suction gas-cooled motors; - cylinder heads with separate, thermally isolated high and low pressure chambers; - a highly e–cient valve design. • Use of the latest Line Start Permanent Magnet (LSPM) motors increases motor e–ciency and seasonal performance. A strong seasonal performance is important in reducing both Total Equivalent Warming Impact (TEWI) and the end user’s operating costs. As a result of performance improvements in the most common operating range, LSPM motors can increase annual e–ciency by up to 14%. • ECOLINE units have a high pressure housing that does not require the use of a bottom plate, enabling maximum permissible pressure levels of up to 160Bar on the high side, and 100Bar on the low side of the system. • To enhance reliability and extend working life, compressors run on multi-layer bearings and wear-resistant drive gear. • Units are designed to optimise oil management to ensure smooth operation and extend working life. This also helps minimise noise and vibration. The BITZER IQ Modules used on the project carry out multiple tasks, acting as an intelligent overseer, monitoring, protecting and analysing compressor operation. Important performance parameters are monitored in real-time. These include motor and discharge gas temperature, high pressure switch and oil level and pressure. It provides early warning of potential problems, flagging operating conditions approaching specified safe limits. Technicians and end users can access stored logs of alarms and warnings, with a full archive of run-time and load statistics for more detailed analysis. Kevin Glass, Managing Director of BITZER UK, said: “Carbon dioxide systems, and transcritical applications in particular, require compressors with a combination of strength, reliability, e–ciency and control. The ECOLINE range has proved its abilities in all of these key areas. The addition of the IQ Module adds the other vital ingredient – intelligent oversight. It is a powerful package that delivers for contractors, end users and the environment.” Brains and brawn behind BITZER’s ECOLINE