Reducing the use of energy provides financial saving if such savings through technology can offset any additional costs incurred in the implementation of energy-efficient technology. Reducing energy use can also been seen as a key solution to the problem of emissions. According to the 'International Energy Agency,' the improved energy efficiency in all spheres could reduce the world's energy needs in 2050 by 1/3rd and help control global emissions.
The Bureau of Energy Efficiency (BEE), a statutory body under ministry of power, Government of India, has come out with several schemes and targets to offer energy-efficient products and systems both in the users' and the national interest. There is, however, no substantial movement on energy efficiency with respect to the refrigeration systems. Most of the food items are perishable in nature under normal temperature & humidity conditions and hence would necessarily need the support of cold chain. The food preservation through cold chain is highly energy-intensive and it is essential to look at the energy efficiency as part of cold chain development in India. The manufacturers and users are therefore required to look at this aspect critically, although there is no regulation that exists currently in this country, so that when the BEE comes out at a later date with the norms of energy labelling of refrigeration system, the users are not constrained or compelled to make changes in their system.
Food Preservation
Many food products are produced in large quantity in India which essentially needs in the times to come, an energy-efficient preservation system. India ranks first in the global rating on milk production; second in fruits and vegetables; third in marine production; fifth in livestock; sixth in meat. In short, India can hold a large food basket for the global consumption if care is taken on the food preservation.
The Indian food processing industry can be broadly classified as "Commodity- based processing" and "Value-added processing." The processing of commodities include wheat, rice, spices etc. and the value-added processing would include bakery items, milk products, ready-to-eat (RTE) and ready-to-cook (RTC) items.
The commodity based processing is roughly contributing to about 2/3rd of the processed food market and the 1/3rd is held by value-added processing.
The market size of value-added processing is currently estimated to be Rs 3,00,000 crore and these food items will essentially require refrigeration system for preservation. India is an evolving market in the food consumption habits. For long, processed food is considered to be the survival need which is progressively moving towards mass marketing, convenience snacking and finally towards quality and hygiene through high technology.
The technology engagement of refrigeration systems for the preservation of food items will be needed for the following categories:
Sl No.: Major Categories: Sub-Categories
1. Dairy: Cheese, paneer, butter, ice cream, yogurt etc.
2. Seafood & meat: Chicken, meat, fish etc.
3. Convenience foods: RTE, RTC, snacks, chips, pasta, noodles etc.
4. Fruits & vegetables: Juice, squash, jam, cut fruits, puree etc.
The need for refrigeration system in these categories is much higher and it is therefore essential to have energy-efficient technology to meet various purposes as mentioned in the preamble.
Refrigeration System for Food Preservation
While the air-conditioning and refrigeration systems are by and large working under the same principle of vapour compression cycle, the refrigeration system for cold storage in India is at very nascent stage. Many manufacturers have entered the fray and vacated the space, fully or partially due to scalability issue in short term. So nothing worthwhile has happened in terms of introducing energy-efficient refrigeration system for the benefit of the user in particular and the nation in general.
The designing of energy-efficient system will provide following tangible benefit to the user:
" Enhanced reliability
" Reduced maintenance cost
" Relatively longer life-time
The design and engineering of the refrigeration system will vary very widely for the products to be preserved. The requirement of the room condition for various perishable food items will be different in terms of temperature, relative humidity, carbon dioxide content, ethylene content etc. The complexity increases when these perishable products are subjected to transportation across places. The major focus therefore is required depending upon the products to be stored, for energy-efficient refrigeration system which can be broadly classified as under:
" System characteristic
" Choice of the compressor
" Selection of evaporators and condensers
" Choice of refrigerant
System characteristic: It is an important parameter to ensure that the refrigeration systems are designed as closely as possible to the anticipated load. Over engineering and sizing of the system will invariably meet with higher capital cost besides significantly increased running cost. This subject has to be seen in relation to the needs of capacity variation that may be required during the periods of operation. A sound knowledge on configuring multiple compressors with various load condition (low to high) is essential on the part of system design engineers. Many produce which are subjected to refrigerated control will require higher capacity during the 'pull down' time period which will substantially come down when the 'hold on' temperature is needed. The rack system with multiple compressors is aimed towards this objective by regulating the mass flow rate to meet the load with minimum energy consumption.
Choice of the compressor: The selection of compressor is related to the refrigerant choice while deciding the suitability of compressor for each application. The technology of compressor has developed very well in the recent past globally and is available with substantial power saving for various applications, if selected properly. There are many types of compressors available for consideration depending upon the food products to be stored. It is important to design any system with the knowledge of the manufacturers 'co-efficient of performance' (COP) to examine which compressor choice will be most suitable at full and part load.
Selection of evaporators and condensers: The key design criteria while selecting the evaporators and condensers is the temperature difference between the refrigerant and the medium to be cooled. Adequate care must be taken in the design of heat exchangers for both evaporator and condenser depending upon the application and the constraint attached with. Water cooled condensers are more efficient than the air cooled. However, wherever air cooled equipment are needed the high efficiency motors could be an option for energy efficiency.
Choice of refrigerant: The most efficient and the environmentally benign refrigerant is a complex subject and yet very important in designing the system. Often system constraints dictate the use of few refrigerants although there are many blends available that require a specialist appraisal.
Conclusion
The energy-efficient refrigeration system for food storage can be better addressed by understanding the following:
a. The thermo-physical properties of the food items to be preserved
b. The selection of various components in the refrigeration system to meet the preservation objective with least energy consumption
c. The customer usage profile of loading the food preservation chambers
The cold chain development in this country has met with several road blocks - investment shortages, low returns on capital, political climate, erratic power positions in many parts of the country etc. - despite a serious approach by the government departments and the private sector at various times. Nevertheless, the country cannot miss the energy-efficient food preservation system for two major reasons:
1. Global food security concern.
2. Alarming rate of increase in the cost of power generation and distribution.
