Low Cost Refrigeration Method for Sitaphal
By: Abhi, Aviral, Khyati and Deepak
May 2017
Problem Statement
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Though there are many major problems like unemployment, electricity, the education we sorted out some minor problems like providing an extra value of forest produce and to get the value of medicinal plants. We focused mainly on Sitaphal and problem related to this is about storing of the pulp. Sitaphal degrades, becomes bitter in taste and color changes if it comes in contact to air and if it is kept at required temperature (~10oC). Since there was no electricity available in every village, so the main problem came to design a low cost, non-electric rural chiller. The problem was to store the Sitaphal pulp for at-least 24hrs such that it does not degrade. After that, the pulp collected was transported to the ice-cream company. We are also trying to work if we can also implement changes in the supply chain to that we can provide alternate solutions other than using the refrigerator. Currently, pulp extraction was done at only one village, but Mr. O.P Sharma wanted to expand this work so that he can provide more earnings for tribal people for the betterment of their livelihood.
Mind Map
As seen in the diagram, in Branch 1 the process carried out and the elements involved in written .There are four main steps involved - collection, pulp extraction, storage, transportation and selling in the market.
Branch 2 highlights the uses and values of Sitaphal including money, nutritional and medicinal values of it. It is an extra source of incomes for tribal communities during the season.
Branch 3 focuses on the areas in which Sitaphal is found. Main states are Rajasthan, Andhra Pradesh, Uttar Pradesh, Madhya Pradesh and Maharashtra.
Branch 4 highlights the existing problem in these regions that are mainly of getting low product value due to loss while processing of Sitaphal and other major problems of unavailability of electricity and seasonal unemployment.
Branch 5, mentions the potential solutions that are freezing using Mitti cool, ground pit method, etc. We also came to know about the availability of energy resources like Solar, Wind, and Biomass which is abundantly available.
Field Visit
Understanding the dexterity of these people in identifying and collecting the forest produce, forest department of Rajasthan has started various projects to create employment opportunities by setting up local processing centers for forest produce. These processing centers make soaps, shampoo, incense sticks, flavors for ice cream etc. The products are now even traded on E-Commerce platforms under the brand name of VANRAJ (king of the forest).To get more details about the problem and interact with the stakeholders the team went for a Field visit from Grambharti ( Gandhinagar) to Devla district of Rajasthan. The team was greeted there by District Forest officer Mr.O P Sharma, who explained the problem statement of refrigerating Sitaphal. The team then proceeded to the Devla district which is about 80km from Udaipur city. Forest Ranger Bhupendra Singh accompanied the team for a field visit.
Site 1: Ghatnadi District- Agarbatti sticks and herbal gulal Nirman Kendra
Observation: The site is used by the forest department for providing employment to tribal people. The local women make incense sticks and gulal by using the forest produce. The waste bamboo is collected and made into incense and candy sticks by manually operated machines.
Site 2: Forest Naka Ghogrut- Forest Produce Processing Centre
Observation: At this site, the Range officer Bhupendra Singh showed us the process of producing soaps, shampoo, gel and juice from Aloe Vera. This facility provides employment when aloe vera is ripe after the rainy season. The final products are marketed and sold by name of VANRAJ.
Site 3: Range Karyalaya Devla Sitaphal Processing center
Observation: This is a site where the Sitaphal is processed by VFPMC. The women takes out the pulp manually, then pulp and seeds are separated in a machine. The outer waste is used as manure, seeds have medicinal values and pulp is packed and stored in freezers. A collection van from NGO/ Agricultural Institute transfers the packaged pulp to cold storage for further processing. The revenue generated by this center is about Rs3 Lakh by the rate of 25RS/ Quintal. According to Mr. Bhupendra, each collection van covers 200 to 300 kg per day.
Conversation
1. Rashmi Bai: She is a tribal woman trained by Forest Department for Incense stick making process. She told that her husband works in the city and the VFPMC helps her earn some stable income. Her earnings are in the range of 200-300Rs/Day. According to her, the financial condition has become stable after this project (about 3 years)
2. Megi: She works in Sitaphal processing centre during the season and earns 150Rs/day. During the off-season, she earns by farming and depends on her cattle.
3. Kishan (36): He works as a laborer and shared deeply about the problems faced by him, ranging from non- availability of electricity to faraway marketplaces.
Prototype and Design Concepts
As part of the design we have tried different methods of cooling and on the basis of mentor feedback, we did changes to our prototype. The very first method of cooling we used was natural evaporation.
Evaporative Cooling Method
In this method, we used the concept of simple cooling by evaporation of continuously flowing water stream .by using a honey comb husk ,fan(for forced convection),copper pipe and a insulated thermocol box we performed our experiment as shown in above diagram .the water flowing through the pipe passes by husk and finally collected in insulated chamber Results:- We finally observed Temperature drop of 3 degree Celsius in 12 hours as temperature drop is dependent on humidity level.theoretical limit that temperature cannot drop below wet bulb temperature , 26-27 degrees This model of cooling failed because it does not provides the temperature drop that is required for Sitaphal preservation.
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Vapour Absorption Cooling (Icy Ball Method)
It is an example of gas absorption refrigerator but they do not require to use electricity for cooling. It can run for a day on 2 hours of sunlight, allowing rural users lacking electricity to utilize the benefits of refrigeration. Earlier the scientist who used this method, took two metal ball: a hot ball, which is fully charged absorber and a cold ball containing liquid ammonia. These are joined by the pipe in the shape of an inverted U. The pipe allows ammonia gas to move in either direction. When the cold ball fully charged with liquid ammonia the device turned around, placing the hot ball in the cold water. As the hot ball cools ,the pressure in the system falls, eventually dropping o the point where the liquid ammonia in the cold ball begins to evaporate and the cold ball begins to cool. In the place of metal balls, we took two pressure cooker. First one is filled with water and second is filled with ammonia . The cooker filled with ammonia is heated up with burner instead of sunlight and second cooker is placed in water. After 4 minute we put off the flame and placed the hot cooker in the water as the hot ball cools , the pressure in the system falls, eventually dropping o the point where the liquid ammonia in the cold ball begins to evaporate and the cold ball begins to cool. We did not use the proper equipment because of unavailability , we faced the problem of leakage of ammonia. We got temperature drop of only 5 degree. We discussed this idea with the mentor they suggested to not use this method because ammonia is dangerous to health.
Phase Change Material
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As suggested by one of our mentors (Ted), we also tried of cooling using PCM. PCMs have property of releasing heat when transforming from liquid to solid form and absorb heat when transforming from solid to liquid phase. Most commonly used PCMs are Glycerol and Saltwater. These once frozen remains cool for 24 hrs and are used in refrigerators used by ice-cream vendors. We made 2 chambers in which the inner chamber is to store the fruit and after that is the bigger container which acts as a cooling jacket and it contains mixture of glycerol and water which has melting temperature between -12 to 0 degree Centigrade. We can freeze the mixture using electricity or using liquid Nitrogen. Doing this we can maintain temperature of the inside chamber for 24 hrs. But due to lot of cost involved in it, this prototype failed.
Thermo-electric
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After failing with these ideas we got input from Dr. PVM Rao to use the concept of thermoelectric, and on the bases of which we made our final prototype. We have used Peltier plates in which when electricity is passed one side gets heated and the other get cooler. The amount of cooling we get depends on the amount of heat we remove from the other side. We have designed a heat exchanger using aluminum block and copper tubes in which water flows as a coolant. The inside chamber contains copper coil to cool the chamber, and the chamber is insulated to avoid heat transfer. Power to the system can be provided directly using solar panel, so no extra requirement of electricity is there. Since we need the temperature of inner chamber around 8-10oC, so we have installed controller to minimize power usage.
Challenges
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There are two main challenges:
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To increase the heat transfer from the hot side to surrounding as fast as possible so as the cooling increases.
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To increase the efficiency by making proper insulation
These two challenges when solved will drastically improve the prototype.
Future Scope
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This can be very useful in we can somehow utilize the heat evolved in the system. Also it is very good for water cooler purpose, because the temperature required in that case is around 10oC. Further work can be done on using solar thermal to cool the refrigerator. Also another device can be made which can work as water cooler. The peltier plate can also be used for dew harvesting in coastal regions.
Project Summary
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Sitaphal is a fruit which is mainly found in forest areas. It is found mainly in the regions of Rajasthan, Madhya Pradesh, Uttar Pradesh, Maharashtra and Andhra Pradesh. Sitaphal is one of the major forest produce in tribal regions of Devla district near Udaipur, Rajasthan. It has nutritional value and it also good in taste. Its seeds has medicinal values and are highly demanded in the market. It is a seasonal fruit and is an extra source of income for tribal people. Sitaphal is mainly collected by women and children in the family and the pulp is extracted which provides them some extra value of the fruit. Few years before, when there was no Pulp Extraction Processing Centre, they used to sell Sitaphal on roadside which gives them very low value of the fruit. This initiative was taken by the DFO of Udaipur, Mr. O.P. Sharma to provide employment and extra earnings for tribal people. Pulp was more value than Sitaphal and is used for flavoring ice-creams and as mentioned the pulp has value of Rs.250/kg which Sitaphal sold there are Rs.20-25/kg. The problem regarding Sitaphal was to store the pulp. Sitaphal degrades, becomes bitter in taste and color changes if it comes in contact to air and if it is kept at required temperature (~10oC). Since there was no electricity available at every village, so the main problem came to design a low cost, non-electric rural chiller. The problem was to store the Sitaphal pulp for at-least 24 hrs such that it does not degrade. Keeping the above constraints in mind we have developed a prototype for cooling and work using Solar Energy. The final prototype is a small 1/30 scale of the required refrigerator. The proposed solution’s concept is to use a refrigerator at centralized location to freeze PCM/ Glycol. Then the collector will transfer it to small processing centre during collection time. The model works using thermo-electric material while for actual product either thermo-electric or compressor refrigerator can be used depending on system size. The details for the actual system required are attached in a report. The key details of final system are as follows:
User's needs: Constant over the year average 5.0 kWh/Day
No. Of Solar PV Modules: 4
Power of each module: 340 WP
Array global power Nominal (STC) 1360 WP
Module area 7.8 m²
Battery: 6 units of 250Ah System voltage: 24 V
The details of the prototype are as follows:
Peltier Device: TEC1-12706
Power: 2 units of 65 watt each
Power by 75 watt module
Place dimensions: 40mm*40mm
