The sun usually makes things hot, right? Well, Mpho Yengane, a former student of Master’s in Sustainable Energy at the National University of Lesotho (NUL), now a PhD student at UCT, has designed a way to use sun’s power to keep fruits and vegetables cool. No electricity is needed!
His work was presented and published at the 3rd International Sustainable Energy Conference (ISEC 2024), held on April 10 – 11, 2024, Graz, Austria. https://www.tib-op.org/ojs/index.php/isec/article/view/1168
He is supervised by Mr. Sebota Mokeke, and Prof. Moeketsi Mpholo in the project.
Yengane designed a solar-powered cooling system that helps farmers store fruits and vegetables—with no need for electricity!
A lot of farmers in Lesotho lose their crops after harvest because fresh produce spoils quickly without proper storage. But Yangene’s smart system is designed to help keep food fresh for longer, meaning farmers can sell more and waste less.
“In Lesotho, we get plenty of sunshine,” he says. “So why not use it to help farmers?”
His system runs on sun’s energy and powers a special fridge called an absorption chiller. Instead of using electricity, the chiller works with heat from the sun! The setup includes solar collectors that heat water, which then creates a cooling effect – keeping storage areas at a chilly 6°C, just about right for preserving fruits and veggies.
The way the absorption chiller works is fascinating. The hot water from the solar collectors is used to heat up a special liquid inside the chiller. This liquid, often a mixture of water and ammonia or lithium bromide, evaporates when heated. As it evaporates, it absorbs heat from the cooling chamber, making it colder. The gas is then condensed back into liquid form, ready to start the cycle again. This process allows the system to generate cooling without using electricity.
That makes it perfect for off-grid farms.
To make the system even more effective, Yengane included a hot water storage tank. This tank stores excess heat from the solar collectors to ensure that the system can continue to operate even when the sun isn’t shining as strongly. By carefully balancing the size of the solar collectors and the storage tank, he optimized the system to provide steady cooling throughout the day and night.
To make sure his system worked, Yengane ran tests using TRNSYS, a special computer simulation program. He checked different designs and found that the best system used a 12-square-meter solar collector and a 0.2 cubic meter hot storage tank. These provided the perfect amount of energy to power the chiller efficiently. The cooling design maintains a steady temperature, proving that it could work well in real farming conditions.
“I wanted something that’s good for farmers and the environment,” he explains. “This system doesn’t use harmful gases or a ton of electricity.”
And the best part? It makes financial sense.
Over time, cooling with solar energy is cheaper than using electricity. Farmers spend less on power and save more food, which means bigger profits! His research found that the system had a Levelized Cost of Energy (LCOE) of $0.085/kWh. This makes it a smart investment. Plus, since it doesn’t need grid electricity, it can be used anywhere—even in remote areas.
“Imagine a future where no farmer has to watch their hard work go to waste,” Yengane says. “With solar cooling, we can cut down on food waste and help farmers make more money.”
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Pass by MILCO @ Sefika Complex, a store that sells only made in Lesotho products. MILCO was created by the NUL Innovation Hub!
