# Use of Phase Change Materials for Food Applications--State of the Art in 2022
## 2 Food Applications of PCM
### Food Storage and Transport
#### 2.2.4 Small, Solar Cold Rooms/Houses  
While in developed countries fast collection of newly produced food like milk, fish etc. is quite efficient, or immediate cooling at the production site using grid electricity is available, this is often not the case in developing countries. The previously discussed milk cooler and the solar freezer/pre-cooler are already applications in this context. Consequently, local, and thus smaller cold rooms/houses that allow cooling close to sites of food production are also needed. Actually, the solar freezer/pre-cooler solutions, previously discussed in Section 2.1. Food Processing, mobile (Figure 4) or stationary, are already for cold storage, but specifically also with a significant capability of cool-down power and thus were discussed earlier.  
In many parts of India, there is a lack of cold storage facilities, because electric power is not available, or because the use of diesel generators as electric power source is too expensive. As a consequence, a significant part of the fresh food produced must be sold immediately, often at times of peak supply, or it loses quality during storage, in the worst case is even completely lost. All this leads to a low income for farmers. The same situation exists in many developing countries around the world. Many of them have lots of sunshine, so a solution to make cold storage space available are solar powered cold rooms. Ref. [12], in their analysis of costs and benefits of clean energy technologies in the milk, vegetable and rice value chains, also analyze different options for solar cold storage. These are PV driven cooling with electric storage (batteries), the same with thermal storage using PCM (ice) or with a chemical process, cooling by thermal sorption refrigeration, and cooling by passive and sorption combined systems. According the report, PV driven cooling with batteries is the most common solution and largely available on the market; solutions typically allow storage between 0 \({}^{\circ}\)C and 15 \({}^{\circ}\)C for up to seven days without sun. Systems with an ice bank typically allow storage in the same temperature range for up to three days, and similar those using a chemical process. The other two options are usually not recommended for the vegetable chain due to limits in performance and volume to cool, or are still in the R&D phase. In their analysis of costs, specifically of commercial products, from all PV driven cooling options the examples with ice storage have the lowest cost with one exception. For systems using batteries they also mention that a major expense is replacing the batteries every 6 to 7 years.  
The commercial solutions analyzed in [12] however cover few products on the market. Figure 7 shows a solar cold room from PLUSS Advanced Technologies, also called Himacool TM. The solar cold room allows storage of fresh fruits, vegetables, etc., in the temperature range 2 \({}^{\circ}\)C to 8 \({}^{\circ}\)C, or \(-25\)\({}^{\circ}\)C to \(-15\)\({}^{\circ}\)C, cooled by a compression cooler driven by solar PV panels mounted on the rooftop, and buffered at a temperature depending on the PCM used, thus not only ice. More detailed information has [40], as well as the corresponding Himacool TM brochure [41]. Ref. [42] has an interview with a representative of the company Inficold, describing many technical details of their solar cold storage houses, the market size, significant reductions of food loss achieved, and decision to scale the technology for larger applications. Ref. [43] specifically discusses the business case for solar PV cooling with ice storage in Africa, stresses that compared to electrical energy storage it is less complicated, requires less maintenance, and has no limited lifespan, and that the investment payback period is less than three years. The advantages of ice storages compared to batteries in solar cooling applications are also discussed at several applications in [12].