Ming Li Wu
Ming Li Wu
Middle School First Place Winner: 2011 Engineering & Human Service - Relief from a Disaster Essay Contest
North Alabama Friends School
Our Solar Fridge

Haiti is wrecked by a devastating earthquake. With a million people living in tents, cholera and typhoid spread like wildfire. Doctors are desperate to get young children vaccinated, but this is a daunting challenge. An astounding four-fifths of Haiti is covered by mountains and, with many unpaved roads, it’s impossible to transport medicines to country villages except by foot. Billionaire philanthropist Bill Gates ships in vaccines but something is spoiling his vaccination plans.

Vaccines travel in a “cold chain” from factories to storage facilities to medical centers to hospitals and finally to the patient. This means the vaccines need to be refrigerated during transport. But unfortunately, the main transportation system in use is a box filled with icepacks. The icepacks melt and seventy-five percent of the vaccines are ruined by the time they reach Haiti’s children. Bill Gates thinks something needs to be done, and a young First Lego League team looking for a biomedical problem for a competition takes on the challenge. I happen to be part of that team.

Engineering teams start to work on a problem by investigating the project parameters. Our team talked to a pharmacist and an immunologist. Our parameters were: the vaccines needed to stay cool for a few days; the refrigerator needed to fit enough vaccines to treat small villages; and the carrier had to be sturdy, waterproof, and portable.

The team decided to try to modify a small refrigerator. Sticking with the conventional cooling system looked easiest. Unluckily, this system was heavy, bulky, expensive… everything we were trying to avoid. We abandoned that idea. To further our understanding of cooling systems, our coach, who is an electrical engineer, bought some electric picnic coolers from a local store. We did an experiment to see how cold they would get and for how long. They weren’t cold enough and did not stay at a steady temperature. Our purpose required a refrigerator designed to keep the vaccines at a specific temperature of 35-45°F or 3-5°C.

Trying to think like engineers, the team came up with other ways we could use the coolers to our benefit. Dismantling a cooler, we found a little tiny ceramic square—a semiconductor. “Well,” we thought, “this is perfect! The semiconductor is so small that we can just build our own insulated box, attach this system, and put everything in a case!” But there was a small problem: electricity. A semiconductor needs electricity to run. The store cooler ran off a car battery, but few cars were available in Haiti. We found a portable charger, but it weighed about seven pounds and only lasted a few hours. We’d require too many chargers and there are only so many heavy chargers you can lug up a mountain.

The team finally settled on solar panels as a reliable, renewable source of energy. Another company did make a solar fridge, but the panels and fridge were as big as three people. Our solar panel folded and attached to the lid of the case and powered a small battery. Wires from the battery led to three devices: the semiconductor, a fan on the heat sink to keep the semiconductor from overheating, and another fan inside the insulated box, which circulated the air so the vaccines wouldn’t freeze solid.

After experimenting, we decided better insulation would help maximize battery life. A NASA thermodynamics engineer helped us understand more about heat and how to keep heat out of our fridge. Some amazing “space age” insulation called Cryogel® helped provide extra protection. Cryogel® is a thin blanket of fiberglass with tiny silica aerogel particles embedded inside. It’s actually six times more effective than the styrofoam insulation we were using, which is an inch thick, compared to not even an eighth of an inch for the Cryogel®! Lining the case with mylar from an emergency camping blanket along with painting the outside of the case white served to reflect even more heat.

The final product is a suitcase-sized hard plastic watertight case divided into three compartments. An insulated vaccine box fits into one compartment, the battery in another, and a temperature control in the third.

Our solar fridge carries vaccines so that epidemics can be treated effectively in hard-to-reach places that do not have electricity. In the future, when all the little details are refined, we plan to show the fridge to Bill Gates and apply for a patent.

By the way—that First Lego League competition? Well, our team won.

Research for Essay Project
Thermodynamics Engineer: Reginald Alexander, NASA
Immunologist: Roger Lallone, Brookwood Biomedical
Pharmacist: Lisa Jackson, MTM Services and Compounding Arts
BrainPop: Vaccines
YouTube: Dr. Pradip K. Bardhan, cholera expert
Radio: NPR and local stations,
Newspapers: Huntsville Times, Wall Street Journal, New York Times
Internet Sites
Mayo Clinic
New Media Explorer
ASCB Newsletter
Kids and culture.org