Eight ways to save energy in cold stores
Researchers from Enviros Consulting analysed cold storage at 13 frozen food manufacturers and cold store operators in UK for the report "Improving the energy efficiency of the cold chain" released by the British Frozen Food Federation (BFFF). Energy saving opportunities equivalent to 4800 tonnes CO2 per year were identified at the host sites. Some cold stores were run at unnecessarily low temperatures. Four of the cold stores were operated several degrees colder than the store to which products were subsequently sent. A simple adjustment to the store control system, combined with an equivalent adjustment to the suction pressure control, can provide significant savings. The suction pressure in one of the cold stores could be raised by about 6°C, corresponding to an energy saving of over 15%. The evaporating temperature of 2 plants was excessively low compared with the air temperature. Whilst the store temperature was reasonable, at around -21°C, the evaporating temperature was -36°C and -40°C respectively. Efficient cold stores operate with a 7 or 8°C difference between the evaporating temperature and the air temperature. If the evaporating temperature can be raised by 4°C, from -32 to -28°C, savings of about 11% can be achieved. The report highlights 37 recommendations which fall into 8 groups: raising of cold store air temperature, reduction of temperature difference (air-refrigerant), seasonal adjustment of evaporating temperature, avoiding air temperature fluctuations, splitting blast freezers and cold stores, avoiding over-cooling in blast freezers, using variable speed drive fans, ensuring a flexible and effective defrost system. The lack of electricity sub-metering on refrigeration systems was identified as a barrier to the identification of good energy saving projects.