Project undertaken in course year 2017-2018 with the Precourt Institute for Energy

Project Goal

Enable low-cost cold storage solutions for guava at the Producer Company (PC) in Rajasthan, India, that can preserve guava for longer periods of time. This will reduce produce losses at the PC, reduce frequency of shipments to market, and maximize farmer profit.

Project Motivation

  • 327 million metric tons of food are wasted in India each year, largely attributed to underdeveloped supply chain that lacks the means to extend the shelf life of produce

  • Guava farmers in India opt to sell their produce as soon as possible for fear of spoilage

  • A cold storage solution that could preserve the guavas would reduce spoilage, while also giving farmers more control over when they deliver produce to market


In India, about 40% of produce perish before reaching consumers due to a lack of cold storage facilities. This spoiled produce equates to a value of approximately $8.3 billion per year.

Team working with Producer Company on visit to Rajasthan, India

High Priority Requirements

  • Hold two tons of guavas

  • Maintain temperature between 10-15C

  • Variable and controllable temperature settings to accommodate seasonal produce

  • Upfront cost < $3000

  • Operational cost less than $3.85/ton/day

  • Keep guavas cool during blackouts of up to four hours

Ethical Considerations

  • Product failure would result in economic losses to farmers

  • The design must consider sustainability of materials, technical accessibility, and energy sources used


Our system consists of a storage chamber, an air conditioner unit attached to a CoolBot to continue to drive at lower temperatures, and a mist cooling system to decrease air temperature in the cold storage unit.

The system has been donated to the O'Donohue Farms at Stanford, build plans have been prepared for the O'Donohue Farms and for the Reliance Foundation in India

System Schematic

The system consists of a mist cooling system, air conditioner, and CoolBot to drive the air conditioner to lower temperatures

The Mist tubing

The metal tubing before being installed into the system. Note the smaller black tubes, which is where the water is delivered and misted in to the metal tubes

Insulating the chamber

Here the team are preparing the inside of the chamber with insulation

System view

Internal view of the chamber. The tubing at the top is used for the mist system, with mist inside the tubing to keep it cool.

Steady state temp

Temperature inside the trailer remains below 10C, meeting requirements. Apples were used as a surrogate for guavas, this result shows how apple temperature was affected

Temp over time

Test results comparing cooling of system with and without misting. The addition of misting is more effective at cooling the apples.

Summary results

The addition of misting results in 2.2C greater cooling of the Apples, though requiring almost double the power. The added power is required to run the pumps for the water.

Student team

Area of focus

The focus region for the project is in Rajasthan, India

Members of the team visit India

Future Work

  • System is deployed and being used at O'Donohue Farms on Stanford Campus

  • Discussions underway to continue development in India

  • Improvements: better airflow in trailer, recycle water in misting system, refine misting system, and clean energy for off-grid power