Solar Disinfecting Device for the Developing World

The ever-industrious engineering students at Rice have made another promising device with medical applications. They’ve modified a solar power apparatus, tweaking it so that it can reach temperatures sufficient to sterilize surgical instruments. The technology could potentially bring effective sterilizing techniques to parts of the developing world that have traditionally lacked them.

The Rice students’ sun-powered autoclave is a modification, essentially, on a much older device, the Capteur Soleil, invented by the Frenchman Jean Boubour. The Capteur Soleil looks something like a metallic swingset, with curved panels to capture solar power. The Rice students then added a specially insulated box containing the autoclave.

Here’s how the system works. The sunlight’s energy is channeled and used to generate steam. A less inventive design might have simply sent that steam right into the autoclave to sterilize instruments. Instead, the team decided to use the steam to heat a conductive hotplate. The circular hotplate was designed in such a manner as to equally distribute the hot steam as it enters. A YouTube video explaining the project shows the hotplate (it’s around the 0:50 mark), which looks something like crop circles, or a circular labyrinth. As the steam gets ferried through the loops in the labyrinth, it gives “a nice, even heat transfer to the bottom of the autoclave,” says William Dunk, one of the students behind the project, in the video.

The hot plate essentially renders the whole apparatus a stovetop. The autoclave, which a press release describes wonderfully colloquially as “like a tricked-out pressure cooker,” is in a plywood frame and features silicon-based Thermablok insulation, which is derived from no less than NASA research on how to insulate the space shuttle.

Maintaining an autoclave at 121 degrees Celsius for a half-hour is the benchmark set by the Centers for Disease Control and Prevention for an environment that renders instruments sterile, “and we’ve found we’re able to do that pretty easily,” one of the students, Sam Major, recently said. They ran a test using some biological spores from a test kit. After running them through the autoclave, all the spores were dead.

The Rice team isn’t the only group interested in using solar power to sterilize instruments. The World Health Organization has posted information (PDF) on a research group called Solarclave that developed a similar apparatus in partnership with universities and NGOs. As for the Rice team’s device, it’s really “the latest iteration of a much larger project,” in the words of the team’s faculty adviser, Doug Schuler.