Health & Wellbeing

Solar steam sterilization system could clean up in the developing world

Solar steam sterilization syst...
Rice University graduate student Oara Neumann, left, and scientist Naomi Halas with their solar steam-powered autoclave (Photo: Jeff Fitlow/Rice University)
Rice University graduate student Oara Neumann, left, and scientist Naomi Halas with their solar steam-powered autoclave (Photo: Jeff Fitlow/Rice University)
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Rice University graduate student Oara Neumann, left, and scientist Naomi Halas with their solar steam-powered autoclave (Photo: Jeff Fitlow/Rice University)
Rice University graduate student Oara Neumann, left, and scientist Naomi Halas with their solar steam-powered autoclave (Photo: Jeff Fitlow/Rice University)

Last year, researchers at Rice University revealed a new way to convert solar energy directly into steam using light-absorbing nanoparticles. At that time, the technology had already been used to create a solar steam-powered autoclave for sterilizing medical and dental equipment and the project had been awarded a grant from the Bill and Melinda Gates Foundation to turn the technology to the task of sanitizing human waste. The researchers have now put both applications to the test.

The heart of both systems are nanoparticles that heat up so quickly when submerged in water and exposed to sunlight that the surrounding water instantly vaporizes to form steam. As an example of its effectiveness, the system even works with icy-cold water and boasts an overall energy efficiency of 24 percent. This is superior even to commercial photovoltaic solar panels that typically have an overall energy efficiency of around 15 percent. Despite the electricity-generation potential of the system, the researchers chose to first focus on sterilization applications for the developing world.

“Sanitation technology isn’t glamorous, but it’s a matter of life and death for 2.5 billion people,” says Naomi Halas, the director of Rice’s Laboratory for Nanophotonics (LANP) and lead researcher on the project. “For this to really work, you need a technology that can be completely off-grid, that’s not that large, that functions relatively quickly, is easy to handle and doesn’t have dangerous components. Our Solar Steam system has all of that, and it’s the only technology we’ve seen that can completely sterilize waste.”

The researchers tested the solar-steam autoclaves in two set ups – one for sterilizing medical and dental equipment and another for sanitizing human waste. They found the heat and pressure generated by the steam was not only sufficient to kill even the most heat-resistant living microbes, but also spores and viruses.

“The process is very efficient,” says Rice graduate student Oara Neumann, the lead author on the PNAS study who created the light-harvesting nanoparticles. “For the Bill & Melinda Gates Foundation program that is sponsoring us, we needed to create a system that could handle the waste of a family of four with just two treatments per week, and the autoclave setup we reported in this paper can do that.”

The research team hopes to partner with waste-treatment company Sanivation in conducting the first field tests of the solar steam waste sterilizer at three sites in Kenya.

The team’s paper detailing the technology appears online in the Proceedings of the National Academy of Sciences Early Edition.

Halas and Neumann describe the technology in the following video.

Source: Rice University

Solar steam used to clean human waste in the developing world

I have seen many hundreds of these or similar ideas but nothing ever comes of them and they just sit on the shelf until the next one.
The problem is getting it out of the lab and into the field quickly.
By quickly i mean like yesterday.
Atul Malhotra
U hit the nail on the head esecallum !
And we need a device that costs no more than 200 USD for a smal scale level, and 2000 USD for a village level for it to work in the poor countries where it is needed most !
Barry Dennis
There are many. many research grant-established technologies that aren't comercailly viable, or are threatening to existing power sstructures and restrained in some ways from reaching needed markets. While I certainly appreciate the testing of technologies in foreign countries with "PC" status", like Kenya and other African countries, where a lot os these ideas seem to be directed, I wonder if we could consider using similarly needy U.S. based communities for some of these technology trial programs.
Research grants? Sit on the shelf? $2000/200 ?? What technology are we talking about here? Sounds like another money grabbing exercise to suck more money out of the poor. Make them more in debt and desperate. Keep them on the hook !
The key here is education. Make those with the needs aware of what is possible to empower them to help themselves.
Here's another option. Go to the scrap yard and gather materials,... for free !!
1. Bash out a wok from an old car door or hood. 2. Sand it back with rocks. 3. Polish it with silt and water from a nearby river or creek. 4. Rub goat (or any animal) fat on the surface to prevent surface rust and bring out the shine. 5. Bend a metal free standing bracket to hold a jar upright. 6. Prep the wok to face the sun 7. Place the jar so it aligns with the wok's focus. 8. If it doesn't focus quite right, make a few finer adjustment with the hammer (or flat metallic bashing device), then repeat the process.
Yes, its not perfect, and it won't win any architectural awards. Nor will it boil the water great efficiency in 2 min. But it will boil it (or make water hot enough to kill bacteria) in under an hour.
Obvious parallel. Egyptians did this thousands of years ago for the purpose of channeling light into pyramids. And they had to actually smelter copper out of rocks. Shaping a flat rectangle of consistent thickness is by comparison a simple task.
S Michael
Put in Kenya and it will be gone within a week; stolen, stripped of it precious metals a thrown on the junk pile. Need something more simple. waste of money.
Gregg Eshelman
Want to do this on the cheap? Start collecting some of the many thousands of old C-Band TVRO satellite dishes, any of the solid types will do.
Clean them up, paint them real smooth, then spray with ALSA "Killer Chrome" paint, or one of the several other processes that have been developed to produce a mirror smooth reflective surface that is NOT chromium.
There's your good enough parabolic reflectors for concentrating solar thermal energy, and at 6, 8 or 10 feet diameter that's serious "solar death ray" energy concentration...