39 TWENTYFOURSEVENBIOPHARMA Issue 1 / March 2025 STERLING PHARMA SOLUTIONS requiring individuals and organisations to transition to less environmentally harmful refrigerants. Like CFCs and HCFCs, hydrofluorocarbons (HFCs) are efficient and stable refrigerants with high heat capacity, but unlike CFCs and HCFCs, do not contain chlorine, and are not harmful to the ozone layer. They are, however, detrimental to the environment: they are classed as greenhouse gases, with a high global warming potential (GWP), comparable to that of CFCs and HCFCs, and consequently, actions have been taken to reduce dependency on HFCs in many regions. On 1 January 2019, the Kigali Amendment to the Montreal Protocol came into force, under which, countries promised to reduce the use of HFCs by more than 80% over the next 30 years. To date, 157 states, including the United States, United Kingdom, and all members of the European Union have ratified the Kigali Amendment. Carbon dioxide R744 has seen increased use in refrigeration because it is minimally toxic, easy to obtain, and has low ozone-depleting and global warming potential. However, it does operate at a far higher pressure than typical HFC refrigerants, increasing the potential for leakage and the incumbent component costs. Further costs are then incurred due to the need for carbon dioxide packs and condensing units, which require special components, more controls and further safety features than an equivalent HFC unit. In comparison, ammonia is known for its heat transfer properties, efficiency and sustainability, and unlike CFCs, HCFCs and HFCs, has no global warming or ozone-depleting potential. Compared to other refrigeration methods, ammonia has low operating costs, functioning well under moderate pressure, with any leaks easier to detect than when other refrigerants such as carbon dioxide are used. However, ammonia can present hazards when handling high concentrations or large volumes, and is flammable under certain conditions. This means that a cooling system requiring only limited amounts of ammonia is ideal to realise the advantages of the cooling technology while minimising the safety risks involved. Case study: Sterling Pharma Solutions and KGM refrigeration As part of its focus on environmental sustainability, Sterling Pharma Solutions partnered with UKbased KGM Refrigeration, to pilot a new 150kW ultra-low charge ammonia chilling technology at its manufacturing site at Cramlington, UK. The new chillers have been designed to overcome the need for a conventional flooded evaporator, which typically increases the size of the equipment required, as well as the quantity of refrigerant charge, and the energy necessary to drive the pumps and machinery. The key to the new design is the charge reduction: by working with very low superheat, which maximises efficiency, together with a reduced volume of pipework, the quantity of ammonia refrigerant within these chillers has been reduced by around 75%, from a typical total of 40kg to only 10kg. This means that the unit offers greater energy efficiency and lower operating costs. The expected working life of the equipment is 20-25 years, which is longer than standard chiller units, and when combined with reduced running costs, offsets the capital expenditure of installation. As the chillers are compact and lightweight, they can be easily mounted on a facility’s roof, avoiding the need for additional risk mitigation measures, such as high capacity exhaust ventilation, that are required in plant room applications. In the event that a leak does occur, a high-level outdoor release will disperse the small volume of ammonia with limited safety or environmental consequence. The technology utilises a synchronous reluctance IE5 motor, which is known for its high levels of energy efficiency and is believed to be the first of its kind in Europe. The cooling load at the location is highly variable, and provided the opportunity to validate the chiller’s ability to respond rapidly to changes in demand. Since its installation, the unit has run for over 5,000
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