The benefits of thermal energy storage for cold chain applications

Thermal energy storage was one of the key topics of the 7th IIR International Conference on Sustainability and Cold Chain held in April 2022. 

 

• Z. Ure (1) recalled that TES, which is the temporary storage of energy at high or low temperature for later use, makes it possible to bridge the time gap between energy needs and energy consumption. By running refrigeration machines during off-peak hours, it is possible to benefit from lower energy tariffs, which can significantly reduce the overall operating cost of many cold chain applications. In addition, using the lower nighttime ambient temperatures can significantly lower energy consumption compared to the daytime. Therefore, a TES load transfer technique not only reduces operating costs, but through the use of off-peak power and operation in lower ambient conditions, considerable environmental and economic benefits are possible. 
• C. Parker and B. Churchyard (2) presented the results of a study of the costs of integrating Phase Change Materials (PCMs) in several sectors of ASDA, a UK-based retailer. The model developed shows that diesel transport vehicles, including home delivery and heavy goods vehicles have the highest financial savings and favourable payback time due to the relatively high cost of diesel per kWh of useable energy. However, cold rooms located in retail shops and depots have a relatively long payback period at the time of the study. 
• Transport and storage of food in an insulated box equipped with PCMs is common for last-mile delivery thanks to easy implementation and low cost. However, problems of maintaining recommended temperatures and temperature heterogeneity are often encountered in practice. After an experimental study, T. Leungtongkum et al (3) conclude that PCM position is a determining factor on the coldest and warmest areas while spacing underneath the load decreases the heterogeneity of its core temperature  
• In the same domain, A. Ilangovan et al. (4) have experimentally evaluated the thermal performance of a new prototype fruit packaging box with PCMs embedded in the cells. From the evolution of the product temperature during the cooling and heating processes, it was verified that the new prototype is particularly suitable for extending the shelf life of peaches outside the storage chamber. When used with the cell containing PCM, the results are even more expressive, allowing the peaches to be kept in adequate storage conditions for an even longer period. 
• In the field of refrigerated transport and insulation of vehicle body walls, M. Calati et al. (5) have studied the effect of incorporating a 0.5 cm PCM layer in a traditional 5 cm polyurethane insulation layer using CFD numerical simulations. The hourly solar irradiance profile was obtained for a typical summer Italian day, aiming at estimating and applying the external heat loads on a 10-hour daily route of a reference truck. With a 25% food load, the air temperature remained below 3 °C for around 7 hours (almost double the period compared to the empty refrigerated body scenario), reaching a maximum of 6°C at the end of the simulation. The heat of respiration did not significatively affect the great potential of the proposed TES system even if it played a role in increasing food temperature. Moreover, considering a 6 m-long truck, only about 100 kg of PCM are needed. 

 

Sources

(1) Ure Z., Thermal Energy Storage for Cold Chain Applications, link. 

(2) Parker C. et al., Theoretical Impact of Phase Change Materials in Food Cold Storage and Delivery, link.

(3) Leungtongkum T. et al., Optimization of Food Transportation and Storage in an Insulated Box: Effect of Phase Change Material Position and Spacing Underneath the Load, link. 

(4) Ilangovan A. et al. Improving the Thermal Performance of Fruit Packaging Boxes by Using Alveolus with Phase Change Material, link.

(5) Calati M. et al. Passive System Based on PCM for Thermal Management of Refrigerated Trucks, link.