This is a final research report from Hort Innovation’s historical archives. Please note that as these reports may date back as far as the 1990s, the content and recommendations within them may be superseded by more recent research.

What was it all about?

This work investigated and proposed a cost energy saving scheme during controlled atmosphere (CA) storage of apples consisting of applying load shifting strategies. The proposed scheme consisted of using electricity during periods of low tariffs (usually during the night), while avoiding electricity usage at periods of high tariffs (peak and shoulder hours). The application of such strategies reduced energy costs but resulted in temperature oscillations within the store which had the potential to result in more rapid quality loss of the fruit.

This study experimentally determined the influence of oscillating temperatures during controlled atmosphere storage on the quality of five apple cultivars: ‘Braeburn’, ‘Fuji’, ‘Granny Smith’, ‘Pink Lady™’ and ‘Royal Gala’. The study showed that temperature oscillations of up to 4°C ± 2°C did not result in increased quality loss for, ‘Royal Gala’, ‘Fuji’ and ‘Granny Smith’ cultivars in comparison to fruit stored at 0.5°C ± 0.3°C and within the recommended shelf life. Oscillations greater than the control (0.5 ± 0.3°C) caused ‘Granny Smith’ to be significantly less firm at 330 days after harvest, but this could be attributed to an unexpected increase in the firmness of the control batch rather than a reduction of the actual firmness caused by higher temperature oscillations. ‘Braeburn’ and ‘Pink Lady’ could reach a maximum temperature of 2.75°C ± 1.25°C (T2) without resulting in reduced apple quality.

Based on this, an energy saving scheme consisting of turning off the refrigeration power during peak hours was proposed for Batlow coolstores. This system had the potential to reduce the cost of energy during the months of operation after reaching the lowest storage temperature. The cost of energy could be reduced by about 45 per cent during that period enhancing the profitability of horticultural industries. However, it was important to clarify that the proposed scheme was specific for Batlow Co-op therefore other industries needed to determine the specific details of the power interruptions (mainly time and duration of the power interruptions) that allowed temperature oscillations on the range that did not affect the quality of the apples.