Solar Cold Storage - Low cost Solar Vegetable Cooler

Cooling of the vegetables are largely done by farmers in bulk mostly in tons to increase the shelf life of the product. But the main problem in doing the same is the high initial investment. Availability and access to such units also becomes an issue for farmers in remote locations. To mitigate this problem a low cost solar powered refrigeration unit had to be developed.

Our first try was to develop one with a portable home evaporative cooler which runs on less energy. Potato was taken into consideration as the crop of choice and for the design both modern interventions along with traditional methods were tried out.

Detailed Project Report -

Field Visits

The project was done in collaboration with Selco Foundation and together with their team I had visited the farm lands of Maharashtra. We had interacted with more than 20 farmers and surveyed their cultivation areas to get our insights.

Learning the ways of a farmer.

This was an amazing opportunity for me to interact with some of the farmers and was trying my best to learn as much as possible from them. It was quite a fun experience for me personally.

Industrial coolers.

We had also visited some of the high capacity industrial coolers with capacity above 10k metric tons. Was able to understand the working of the same and also sat with the team to learn about the finances and other statistics. The image to the right is a traditional storage unit used by the farmers in their farms. It mainly used wood structure and had a cement floor.

Scouting for an installation site

On having got all the necessary information, now we were in the look out for a site to install our intervention. On of the local farmer helped us with that by lending his abandoned storage area. It was on top of a hill and the view was breathtaking.

Designs

Since the project timeline was fixed to be less than a month I had to get radical with the design process. Evaporative coolers were finalized for the cooling solution due to its cheap investment required as well as easy availability and the rest of the designs were done around the idea. The cool air from the cooler would be funneled on to a section of pipes that would then dissipate them to the potatoes that were gathered around them.

Design constrains

While considering the design traditional models of storage that are sued by the farmers were also taken into consideration. This would involve the potatoes to be staked in a long pyramid structure. Our plan was to keep the cooling pipes in between the structure to cool them off continuously. Hay was also used by the framers to keep the temperature low.

Sourcing of material

Once the designs were done and the list of material was formulated the materials were locally sourced. The farmer helped us with the transportation and my colleague Mr. Daneshwar can be seen in the image overseeing the proceedings.

Journey to the top... in a tractor

This was more of fun at the start and a lot of peril in the process. We had climbed on top of the tractor and was holding on to dear life while the machine was climbing near vertical slopes. Got a chance to ride the tractor too. Fun day.

Local fabricator

All the drawings and 3d models helped me to communicate the designs to the local fabricator.

Tight schedule

A very tight timeline meant we had to work even during the dark hours. Here you can see us doing the final touches to the funnel to the cooler.

Starting the fabrication

The design involved a lot of small components and everything was made in batches and checked in intervals so as we do not waste the materials.

Assembling the design

After all the components were made they were assembled together before the crops arrived.

Operation on the evaporative cooler

The cooler was striped off and disassembled to make a few adjustments. The evaporative cooler uses water to cool its air and this meant storage of water in its tank and to automate the process we had attached a hose to the tap and then attached a float ball valve that closes the water supply as soon as the water is full in the tanks.

Potatoes ready to be stored

We had purchased 5 tons of potatoes for the storage and it arrived right on time.

Preparing the bed

Before the potatoes were stored, a bed had to be made and the structure placed in the middle.

Potato sorting

The potatoes were carefully sorted out in the beds that were prepared.

Remote monitoring system

To detect the temperature, humidity and CO2 levels inside the heal we had installed a remote monitoring system inside the heap that would transmit the data to our PC devices anywhere in the world. This would give us an opportunity to monitor the system and collect data back in our Bangalore office. Here you can see the technician configuring and deploying the device.

Sensors and auto cut off switches.

One of the main component of the design was a auto cut off switch that would detect the temperature inside the heap if it would go below 12 degrees and turn off the cooler. A sensor would be placed inside the heap to help in detecting the temperature. The cooler will also be turned on when the temperature climbs above 15 degrees there by maintaining the coolness and also being energy efficient at the same time.

Final structure

After making sure all the components were kept in place we had closed off the area and covered the structure with hay for natural cooling.

Way forward

An ideal solution would be to develop the an AC module cooler that would address the humidity problem that is faced in case of the evaporative cooler that we deployed but development has to be done to make it energy efficient and low cost.
The factors that need to considered for such an AC system are,
1. How effective is a split AC in a small closed structure?
2. The system should be developed in such a way that the air keeps circulating in a closed loop thus requiring less energy to maintain the cold temperature
3. To what extend will adding a thermal insulating sheet increase in cooling efficiency, and how will it be integrated with the current setup.

Gallery

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