ECOGuavo!
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
Background
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
Solution
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