Cold storage helps in preserving perishable foods. In addition to preventing deterioration, cold storage has real economic importance, since it promotes international trade and maintains the quality of agricultural and fishery products. The applications of cold storage to a wide variety of perishable food items have become firmly established over a century since its introduction. One of the most important factors affecting the quality, safety and storage life of agricultural and food products is temperature.
For instance in India, supermarket sales account for 70% of all food sales. Currently, in the light of energy crisis, energy efficiency is crucial for sustainable development particularly in developing countries like India. The energy efficiency is also a strategy for addressing climate change. Increased costs of electricity and alternative fuels force refrigeration primarily based cold storages and business buildings to cut back their energy consumptions and demands or to implement the means for preserving energy. Therefore, there is need to minimize the energy consumption and energy demand, which consequently reduces emissions at the thermal power generating stations. In view of the energy conservation opportunities in industrial, commercial and residential sectors; one of important areas is cold storage industry which needs to be addressed with immediate attention. Preservation of commodities in the cold storage is an energy intensive process and consumes electrical energy. The proper and timely preservation of the perishable commodities is crucial for retaining their quality, natural flavor and for minimizing quantity degradations. The Indian cold storages mainly run on the grid electricity and their energy expenses account approximately 28% of the total costs. However, continuous efforts are being created by researchers and engineers to boost the energy performance within the cold storages. By dominant parameters of temperature, humidity and atmospheric composition, along with utilizing proper handling procedures, cold chain service providers can increase the product life of fresh foods for days, weeks or even months.
Cooling technology for cold storages
The performance of cold storage only depends on the temperature. Lower the temperature inside the cold chamber, greater will be the performance. To achieve the low temperature to storage, a refrigeration system is employed. This refrigeration system works on vapor compression. The refrigerant is used as working fluid for vapor compression refrigeration.
Components of Cold Storage
The cold storage consists of following components:
• Solenoid valve
Compressor: The reciprocal and screw compressors are the most effective to use with refrigerants that need comparatively little displacement and condense at relatively high.
Condenser: It is an essential part of the cold storage plant. It is applied to work at higher side at the constant pressure. Three types of condenser are frequently used in the cold storage – atmospheric or air type, water cooled and evaporative condenser. The condenser fan can also be used to force air. For enhancing the heat transfer, Aluminum fins are employed in condenser with a regular gap of 2 mm.
Receiver: It is basically storage vessel designed to hold excessive amount of refrigerant not in circulation. Liquid receivers are employed at liquid line as near as to the outlet of condenser. The piping between condenser and receiver should be so arranged that it can enable for free drainage.
For uniform and rapid cooling within cold store, product should be so stacked that cold air from evaporator can be enabled to move throughout each individual crate. It is essential that crates are so arranged that air channel can be made in cold store for direct air movement and also there should be some gap between the crates and walls to enable refrigerated air to absorb the heat of conduct through the walls. The arrangements of stack are accomplished by providing the certain gap among the columns of stack. From average temperature distribution, it has been observed that on increasing the gap between the columns of stack, the tendency of achieving low temperature within the cold storage is more. This happened due to increasing the gap between the columns of stack, the width of air channels in different arrangements. The increase in width of air channels give the way to air to be circulated to each individual crate within the cold storage. The increase in gap also influenced the running time of cold storage. Larger gap provides more air circulation, resulting to achieve the optimal temperature of product rapidly.
Use of Renewable Solar Energy in Cold Storage
When solar radiations are interpreted on solar collector then it converts solar energy into the electrical energy which is being stored into the batteries i.e. the batteries are charged by solar energy. The inverter is used to convert electrical energy from 24V DC to 220V AC. This energy is supplied to AC electric motor, which is used to run the refrigerator
The followings are the benefits of using renewable solar energy in cold storages:
• The solar panel can be effectively used in summer to produce refrigeration effect using solar hybrid refrigeration cycle.
• The operating cost of the solar hybrid refrigeration cycle is low.
• It does not need to be connected continuous to power grid nor any consumable fuel as power source.
• Solar hybrid refrigeration systems are more applicable in remote areas where conventional cooling is difficult and solar energy is always available.
• This system is more suitable because pollution free working fluid use as a refrigerant.
Energy Conservation Options in Cold Storages
The energy conservation in the cold storage is now getting more attention throughout the world to protect earth’s environment. The energy potency of cold storage is varied on parameters like arrangement of stack, maintenance of cooling temperature range, type of stored items etc. A few options can be implemented immediately and other can only be incorporated effectively at the time of planning and development stage of cold storage. The exterior surfaces are painted by different colors without taking the advantage of high reflection properties. The energy consumption may be reduced considerably by choosing the color of exterior surface. Nearby plantation and other shading of building might be effective options for immediate improvement in energy efficiency as well as for minimizing the worst environmental effects. The overall energy consumption can be minimized significantly by choosing the optimum aspect ratios and the respective orientation of the cold storage building. The construction materials used in the cold storages are conventional and have not been arranged in any specific manner. The thickness of the different materials needs to be optimized.
To save energy the following practices must be implemented:
1. Reducing Heat Loads
2. Use of latest energy saving equipments
3. Proper Insulation
4. Efficient maintenance practices
5. Automation & Integration.
Moreover, the cold storage should be designed on concrete platform which greatly reduces the heat gain from the soil.
Challenges and Barriers to Cold Storages
While it is difficult to control a business in any international atmosphere, one of the greatest challenges to cold chain expansion in a developing market is the lack of infrastructure to sustain cold chains. Transportation systems in many of these economies in a timely manner are difficult. In addition, lack of reliable power for cold storages, power hookups at ports and transportation hubs, and adequate facilities at the final customer locations add further costs and complications.