# Use of Phase Change Materials for Food Applications--State of the Art in 2022
## 2 Food Applications of PCM
### Food Storage and Transport
#### 2.2.5 Small Coolers and Freezers  
The idea to integrate PCM into small coolers and freezers was already investigated in the early 1990s. Latest around the year 2000, the first commercial application was brought to the market: the company Kissmann has coolers and freezers e.g., for small boats, with PCM as thermal buffer [44]. Somewhat bigger storages for food, chest coolers and freezers, e.g., used in households, are for 2 to 8 \({}^{\circ}\)C (cooling) and \(-\)24 to \(-\)18 \({}^{\circ}\)C (freezing). Here, the company PLUSS Advanced Technologies has developed a commercial product; Figure 8 shows how PCM pocules are integrated into the compartment walls. The advantage of the PCM is as backup for the case of power failure, common in countries with no stable grid, like India, and to increase the efficiency of the electric cooler. According tests under the supervision of UNIDO (United Nations Industrial Development Organisation) and CII (Confederation of Indian Industries) described in [45], the freezers and coolers with PCM provide thermal backup up to 16 h at an ambient temperature of 35 \({}^{\circ}\)C to 40 \({}^{\circ}\)C, and the electrical energy consumption is reduced by 20-25%. The return on investment is achieved in 9 months. According to [45] over 50,000 freezers and coolers have already been integrated and deployed with PCM technology in India, equivalent to a market penetration of 2%. Several large- and small-scale manufacturers and a major OEM are commercially adopting the technology on a large scale. More and up-to-date information can be found on the company website ([[https://pluss.co.in/logistic/](https://pluss.co.in/logistic/)]([https://pluss.co.in/logistic/](https://pluss.co.in/logistic/)), accessed on 27 September 2021). While it seems as if there was little R&D in the past on Section 2.2.4, the situation is quite different for Section 2.2.5. Even several reviews on the topic are for example available. Ref. [46] made a literature review concerning different aspects of the use of PCM in conventional refrigeration systems. It covers different aspects like the amount of PCM, its phase change temperature, and position of its integration, investigated by modeling as well as by experimental testing. The PCM can be attached to the evaporator or condenser of the compression cooler, or placed somewhere inside the food storage compartment; each option has distinct advantages and disadvantages being discussed. Ref. [47] has a similar scope, and specifically lists references with respect to the PCM position. Further on, it includes a  
Figure 8: Freezer/cooler (source: PLUSS Advanced Technologies Ltd.). Figure 7: Solar cold room (source: PLUSS Advanced Technologies Ltd.). table with the results of experimental works, specifically the change of COP, and the same for simulations. Ref. [48] reviewed cold storage techniques in food preservation appliances such as refrigerators, freezers, as well as others. With respect to domestic refrigerators and freezers they specifically summarize experimental and numerical results including the PCM used, its placement, the focus of the investigation, and the outcome. Besides the technical and economic advantages for the user, the option to shift electricity demand to off-peak demand hours by energy storage could allow more flexibility for the utility, the electricity supplier. Specifically, the reduction of the peak demand on an electric grid that is based on renewables by shifting demand to non-peak hours, increasing grid stability, is of increasing interest in many parts of the world. Compared to the discussion of \"2.2.3. Cooling Large Food Production, Storage, and Distribution Facilities\", here are many small ones. Ref. [49] investigated the potential for load shifting by domestic refrigerators in smart grids. They argue that these appliances are available for the most advanced strategies of demand-side load management (DSLM), and that by combining smart grid technologies and thermal energy storage by using PCM the full potential of the approach can be realized.