Cold storage systems integrated with phase change technology

Abstract

Market demand for cold storage systems, a critical component of modern cold-chain logistics, is rapidly expanding. Phase change cold technology offers a low-carbon route for energy savings in cold storage systems and is now a major research focus. This paper outlines the application of cold storage technology, systematically reviews the characteristics of three types of phase change materials (PCMs), and provides a comparative analysis of their advantages and disadvantages. It elaborates on key techniques for enhancing material properties and details the primary encapsulation strategies to address engineering challenges. This study categorizes cold storage systems into active and passive types, and identifies refrigeration units and external heat ingress as the primary sources of energy consumption. Based on this classification, three specific application scenarios for integrating PCMs into cold storage systems are clearly outlined. This study provides a comprehensive summary and analysis of the current development prospects and challenges of phase change cold storage technology. It proposes that future research should prioritize the development of high-performance PCMs, optimization of cold storage panel arrangements, and studies on system-level integration.

1. Introduction

Cold chain logistics is a critical approach that ensures that a specified low temperature is consistently maintained during the storage and transportation of fresh food, thereby effectively safeguarding the quality and safety of food products [1–2]. A cold storage facility or cold room is a type of refrigeration equipment that artificially creates an environment with temperatures or humidity conditions different from the outdoors. It is a crucial component of cold chain logistics and is widely used for storing products such as food, dairy, meat, seafood, poultry, fruits, vegetables, and beverages, ensuring their quality and safety in low-temperature environments [3]. Typically, cold storage facilities maintain temperatures between −10 and −30°C and possess significant cooling capacity and area. In the domestic context, the construction of cold storage facilities in China is rapidly progressing, primarily located in major fruit and vegetable production areas as well as in the suburbs of medium to large cities [4]. With the rapid development of industries such as agri-food processing and biomedicine, the demand for freezing and refrigeration is also increasing rapidly, leading to greater requirements for tonnage, scale, and type of cold storage facilities. New construction concepts for cold stores that emphasize standardization, modularity, and factory-based approaches are gradually replacing traditional building forms and operational models. The cold storage industry in China will further focus on convenience and enhance its facilities to improve the “last mile” service capability of cold chain logistics. Nonetheless, the increasing demand for cold stores has accelerated energy consumption, with cold storage facilities accounting for approximately one-seventh of the total electricity usage of China [5]. Therefore, it is crucial to actively develop novel low-carbon energy-saving technologies for use in cold storage facilities [6–8].

As a novel energy-storage technology [9], phase change cold storage technology can be integrated into cold storage systems. By utilizing a substantial amount of energy absorbed or released by phase change materials (PCMs) during their phase transition process, this approach maintains the temperature at an almost constant level, thereby enabling precise temperature control within cold storage facilities and ensuring that the temperature remains stable within a predefined optimal range [10–14]. This integration advances the twin goals of reducing energy use and emissions. By embedding PCMs, the cooling load on the compressors is reduced, and the power demand decreases. For instance [15], by cooling and storing refrigerants during off-peak hours when electricity is cheaper, their cooling capacities can be effectively utilized during peak daytime hours, thereby reducing reliance on refrigeration equipment. In addition, during power outages or compressor failures, stored cooling in PCMs maintains safe temperatures, prolongs shelf life, and sharply reduces the risk of food spoilage. Moreover, integrating phase change cooling technology between cold storage and cold chain transportation can ensure stable temperatures during transit, particularly in multimodal transport scenarios, thereby enhancing transportation efficiency and reducing losses [16]. As shown in Fig. 1, the application of phase change in cold storage systems primarily involves integrating PCMs with cold storage panels, building envelopes, and refrigeration units.