Engineering Could Save One-Third of Panama’s Onions

Panamanian researchers have created a prototype to guarantee the good condition of the country’s critical onion crop. The work may be a big step in increasing the volume of the vegetable that comes to market. Presently, about one-third of the country’s crop rots because of inadequate drying conditions. 

Coclé is a Panamanian province on the southern coast, on the Pacific Ocean, and is famous for its rich soil. Located in the center of the Caribbean country, Coclé generates up to 200,000 quintals, or more than 44 million pounds, of onions annually. The crop is harvested in the spring.

However, the local industry suffers  heavy losses due to poor drying of the crop. Experts estimate that 30 percent of the total harvest is lost in the first 15 days after harvesting. This not only prevents farmers from recovering their investment but also reduces employment and the amount of onions that go to market.

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To reduce the impact, researchers at the Center for Innovation and Technology Transfer of the Technological University of Panama have developed a project aimed to dry the crop more efficiently.

"The specific applications of this project are a post-harvest treatment for onion drying,” said César Almanza, an engineer and project leader. “This process is carried out using hot air flow inside the structure of the cargo containers where the onion will be placed. Through temperature and humidity sensors inside, the data is fed to a control module that will activate the constituent elements.”

The researchers initially have developed a mobile prototype powered by solar photovoltaics that allows the platform to opérate off the grid, so it can be moved to the fields where the onions are harvested.

"Directly, the photovoltaic system gives energy support to the prototype. Through solar convection transfer in the daytime, the temperature inside it is raised, said Almanza. “This allows it to be used away from the energy supply of the conventional network in the farms. At the same time, energy is also stored in a liquid medium, which is initially wáter.”

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The prototype uses a reserve tank, located in its upper part of the dryer, for this application. The liquid is heated during the day by solar equipment and it is used at night when the temperature demand changes.

Researchers have conducted tests to measure the drying quality provided by the prototype. For these tests, they introduced the onions into the equipment in bags of up to 50 pounds, as well as plastic boxes. 

Almanza said 900 pounds of onions were loaded into the unit for  first test. Of that amount, 18 pounds , or approximately 2% of the total, were unrecoverable, translating to a 98% efficiency rate.

“The second test consisted of drying 5.2 tons, distributed in 230 50-pound bags,” Almaznza said. The results were similar, with 2.2% losses and 97.8% effectiveness, he reported.

The team will continue to carry out validation tests. In particular, they hope to expand the amount of product inside the prototype through other forms of distribution in the available space.
Although the prototype has significant support, researchers still must overcome some challenges. Gaining acceptance from farmers may be one of the largest.

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"We have had to promote a paradigm-shifting culture among farmers. Many of them, once the harvest cycle is completed, choose to put their products on the market immediately, said Almanza. “This frees the producer from some problems, but in reality, these are passed on to the user.”

Calibration of the control system has also presented difficulties. This is due to the location of the crop and the fact that there is only one harvest per year. Researchers have the disadvantage of very short periods to optimize.

The project has been supported by Panama's National Secretariat for Science, Technology and Innovation, with a small fund from the Korean Intellectual Property Office. Researchers hope to expand the project, depending on further funding.

Claudia Alemañy Castilla is a science and technology journalist based in the Canary Islands. She is the Engineering for Change Editorial Fellow. For more on development engineering, check out Engineering for Change.