Sunlight can produce steam, scientists say
Research could lead to cheap, compact devices for poverty-stricken areas
Posted: Nov 19, 2012 3:01 PM ET
Last Updated: Nov 19, 2012 3:00 PM ET
Scientists today are describing a revolutionary new way to use sunlight to produce steam and other vapors without heating an entire container of fluid to the boiling point.
The advance, reported in the American Chemical Society (ACS) journal ACS Nano, has potential applications, especially in the poverty-stricken areas of the developing world, that include inexpensive, compact devices for purification of drinking water, sterilization of medical instruments and sanitizing sewage.
"This research opens up a revolutionary new application of nanoparticles in solar energy," said Paul Weiss, Ph.D., editor-in-chief of ACS Nano, one of more than 40 peer-reviewed scientific journals published by ACS, the world's largest scientific society.
"The authors show that sunlight can be used to create steam with virtually no wasteful heating of the surrounding liquid. The potential societal benefits are staggering. They include more energy-efficient distillation of alcohol, a new and highly practical strategy for desalination and water purification and compact solar-driven sources of steam for sterilization and sanitation in resource-poor locations," said Weiss.
Naomi Halas, D.Sc., Peter Nordlander, Ph.D., and colleagues note in the report that metallic nanoparticles (so small that 1,000 would fit across the width of a human hair) absorb large amounts of light, resulting in a dramatic rise in their temperature. They are with Rice University in Houston, Texas. That ability to generate heat has fostered interest among scientists in using nanoparticles in a range of applications. These include photothermal treatment of certain forms of cancer, laser-induced drug release and nanoparticle-enhanced bioimaging.
Scientists in the past also explored the use of nanoparticles in solar energy applications. However, that research focused mainly on using nanoparticles to improve the ability of fluids to conduct heat. Until now, scientists had not reported on the use of nanoparticles, mixed into fluids, to capture sunlight, heat up and change the fluid into steam or other vapor.
The new report explains that nanoparticles illuminated by light can quickly rise to temperatures above 100 C, the boiling point of water. Steam forms around the surface of each nanoparticle, billons of which can be placed in water or other fluids. Eventually, the vapor escapes from the particle, forming nanobubbles that float to the top of the surface and escape as water vapour or steam, vapors of ethanol in the case of distillation of alcohol for beverages or fuel, or other vapours.
It describes the use of this approach to measure and document solar steam generation in water solutions illuminated by sunlight containing different kinds of nanoparticles. One solution contained silicon dioxide/gold nanoparticles and another contained carbon nanoparticles. The nanoparticles began to produce steam within five to 20 seconds after shining sunlight into the solutions. The gold nanoparticle solution produced steam in small "microexplosive" bursts. The scientists used the gold nanoparticles to distill alcohol from water and got higher yields of alcohol than would have occurred by boiling the solution.
An impressive 82 per cent of the sunlight absorbed by the nanoparticles went directly to generating steam. The overall energy efficiency of the steam generation process was 24 per cent, and the scientists had made no effort to optimize the process.
"These results clearly indicate that solar steam generation is a process that has significant potential for use in a wide variety of energy- and sustainability-relevant applications," the report states. "Solar-driven, stand-alone waste processing or water purification systems could be developed based on this process.
High-temperature steam (about 115 C and above) produced directly using sunlight could also be used for compact sterilization or sanitation purposes, from the processing of medical waste to the cleaning of medical or dental equipment, minimizing the resource, time and input chemical requirements demanded by current methods.
With further development, this approach may be adaptable to higher pressures and other working fluids to drive turbines in solar energy harvesting applications. This approach may also be modified to harvest radiant energy from sources other than the sun, for instance, for the capture of waste energy from geothermal, residential or biological sources."
Top News Headlines
- 3 more suspects arrested in slaying of U.K. soldier
- British police investigating the savage killing of an off-duty soldier in London have arrested three more suspects. more »
- Hockey Canada votes to ban bodychecking in peewee hockey
- Neil Macdonald: How serious is Obama about curbing the drone surge?
- In a key speech this week, the U.S. president set out a host of supposed new safeguards for America's controversial practice of remote-controlled rough justice. But as Neil Macdonald writes, the underlying rationale for drone use has not fundamentally changed. more »
- Ontario man lost in Australian mountains has survival skills
- The sister of an Ontario man who disappeared in Australia's Snowy Mountains nearly two weeks ago says she remains hopeful he will be found, partly because of his training as a Canadian Forces reservist. more »
Latest Technology & Science News Headlines
- 1976 Apple computer sells for $668,000
- An auctioneer says one of Apple's first computers — a functioning 1976 model — has been sold for a record $668,000 US. more »
- 3D printers give rise to 'desktop manufacturing'
- Customizable objects from plastic dollhouse furniture to medical prosthetics can now be designed and printed out by almost anyone at the press of a button, and is going to lead to an 'explosion of new stuff,' predicts author Chris Anderson. more »
- Google Street View captures Galapagos Islands
- Few have explored the remote volcanic islands of the Galapagos archipelago, an otherworldly landscape inhabited by the world's largest tortoises and other fantastical creatures that inspired Charles Darwin's theory of evolution. more »
- King Richard III buried in 'untidy' grave
- New information has surfaced in the odd tale of the British king buried in a car park. King Richard III's remains, which were discovered August under a parking lot in Leicester, England, were laid to rest in a grave researchers are now saying was "badly prepared" and "untidy." more »
Bob McDonald's Blog
- Chris Hadfield: The gravity of gravity May. 17, 2013 9:58 AM After five months of being Superman and a media superstar, Canadian astronaut Chris Hadfield is now beginning the challenging task of adapting his mortal body and brain to life back on Earth.
- McDonald's CEO chastised by 9-year-old B.C. girl
- Will Rob Ford's supporters leave Ford Nation?
- Toronto Mayor Rob Ford denies using crack cocaine
- Dog snared on baited hooks near Vancouver's Grouse Grind trail
- Washington police blame bridge collapse on Alberta trucker
- 3 more suspects arrested in slaying of U.K. soldier
- Wallin may be forced to repay thousands in travel expenses
- Canada ranks 3rd last in paid vacations
- Toronto mayor's brother says he never dealt drugs