Nanotechnology Now

Our NanoNews Digest Sponsors


Heifer International

Wikipedia Affiliate Button

Home > Press > Steam from the sun: New spongelike structure converts solar energy into steam

On the left, a representative structure for localization of heat; the cross section of structure and temperature distribution. On the right, a picture of enhanced steam generation by the DLS structure under solar illumination.

Courtesy of the researchers
On the left, a representative structure for localization of heat; the cross section of structure and temperature distribution. On the right, a picture of enhanced steam generation by the DLS structure under solar illumination.

Courtesy of the researchers

Abstract:
A new material structure developed at MIT generates steam by soaking up the sun.

The structure — a layer of graphite flakes and an underlying carbon foam — is a porous, insulating material structure that floats on water. When sunlight hits the structure's surface, it creates a hotspot in the graphite, drawing water up through the material's pores, where it evaporates as steam. The brighter the light, the more steam is generated.

Steam from the sun: New spongelike structure converts solar energy into steam

Cambridge, MA | Posted on July 21st, 2014

The new material is able to convert 85 percent of incoming solar energy into steam — a significant improvement over recent approaches to solar-powered steam generation. What's more, the setup loses very little heat in the process, and can produce steam at relatively low solar intensity. This would mean that, if scaled up, the setup would likely not require complex, costly systems to highly concentrate sunlight.

Hadi Ghasemi, a postdoc in MIT's Department of Mechanical Engineering, says the spongelike structure can be made from relatively inexpensive materials — a particular advantage for a variety of compact, steam-powered applications.

"Steam is important for desalination, hygiene systems, and sterilization," says Ghasemi, who led the development of the structure. "Especially in remote areas where the sun is the only source of energy, if you can generate steam with solar energy, it would be very useful."

Ghasemi and mechanical engineering department head Gang Chen, along with five others at MIT, report on the details of the new steam-generating structure in the journal Nature Communications.

Cutting the optical concentration

Today, solar-powered steam generation involves vast fields of mirrors or lenses that concentrate incoming sunlight, heating large volumes of liquid to high enough temperatures to produce steam. However, these complex systems can experience significant heat loss, leading to inefficient steam generation.

Recently, scientists have explored ways to improve the efficiency of solar-thermal harvesting by developing new solar receivers and by working with nanofluids. The latter approach involves mixing water with nanoparticles that heat up quickly when exposed to sunlight, vaporizing the surrounding water molecules as steam. But initiating this reaction requires very intense solar energy — about 1,000 times that of an average sunny day.

By contrast, the MIT approach generates steam at a solar intensity about 10 times that of a sunny day — the lowest optical concentration reported thus far. The implication, the researchers say, is that steam-generating applications can function with lower sunlight concentration and less-expensive tracking systems.

"This is a huge advantage in cost-reduction," Ghasemi says. "That's exciting for us because we've come up with a new approach to solar steam generation."

From sun to steam

The approach itself is relatively simple: Since steam is generated at the surface of a liquid, Ghasemi looked for a material that could both efficiently absorb sunlight and generate steam at a liquid's surface.

After trials with multiple materials, he settled on a thin, double-layered, disc-shaped structure. Its top layer is made from graphite that the researchers exfoliated by placing the material in a microwave. The effect, Chen says, is "just like popcorn": The graphite bubbles up, forming a nest of flakes. The result is a highly porous material that can better absorb and retain solar energy.

The structure's bottom layer is a carbon foam that contains pockets of air to keep the foam afloat and act as an insulator, preventing heat from escaping to the underlying liquid. The foam also contains very small pores that allow water to creep up through the structure via capillary action.

As sunlight hits the structure, it creates a hotspot in the graphite layer, generating a pressure gradient that draws water up through the carbon foam. As water seeps into the graphite layer, the heat concentrated in the graphite turns the water into steam. The structure works much like a sponge that, when placed in water on a hot, sunny day, can continuously absorb and evaporate liquid.

The researchers tested the structure by placing it in a chamber of water and exposing it to a solar simulator — a light source that simulates various intensities of solar radiation. They found they were able to convert 85 percent of solar energy into steam at a solar intensity 10 times that of a typical sunny day.

Ghasemi says the structure may be designed to be even more efficient, depending on the type of materials used.

"There can be different combinations of materials that can be used in these two layers that can lead to higher efficiencies at lower concentrations," Ghasemi says. "There is still a lot of research that can be done on implementing this in larger systems."

###

Written by Jennifer Chu, MIT News Office

####

For more information, please click here

Contacts:
Kimberly Allen
MIT News Office

617-253-2702

Copyright © Massachusetts Institute of Technology

If you have a comment, please Contact us.

Issuers of news releases, not 7th Wave, Inc. or Nanotechnology Now, are solely responsible for the accuracy of the content.

Bookmark:
Delicious Digg Newsvine Google Yahoo Reddit Magnoliacom Furl Facebook

Related Links

Gang Chen:

Archive: A new way to harness waste heat:

Archive: Solving a mystery of thermoelectrics:

Archive: Cooling when there’s too much heat:

Related News Press

News and information

Penn team uses nanoparticles to break up plaque and prevent cavities July 28th, 2016

Beating the heat a challenge at the nanoscale: Rice University scientists detect thermal boundary that hinders ultracold experiments July 28th, 2016

WSU researchers 'watch' crystal structure change in real time: Breakthrough made possible by new Argonne facility July 27th, 2016

Enhancing molecular imaging with light: New technology platform increases spectroscopic resolution by 4 fold July 27th, 2016

Discoveries

Penn team uses nanoparticles to break up plaque and prevent cavities July 28th, 2016

Beating the heat a challenge at the nanoscale: Rice University scientists detect thermal boundary that hinders ultracold experiments July 28th, 2016

WSU researchers 'watch' crystal structure change in real time: Breakthrough made possible by new Argonne facility July 27th, 2016

Enhancing molecular imaging with light: New technology platform increases spectroscopic resolution by 4 fold July 27th, 2016

Materials/Metamaterials

WSU researchers 'watch' crystal structure change in real time: Breakthrough made possible by new Argonne facility July 27th, 2016

New lithium-oxygen battery greatly improves energy efficiency, longevity: New chemistry could overcome key drawbacks of lithium-air batteries July 26th, 2016

Designing climate-friendly concrete, from the nanoscale up: New understanding of concrete’s properties could increase lifetime of the building material, decrease emissions July 25th, 2016

Attosecond physics: Mapping electromagnetic waveforms July 25th, 2016

Announcements

Penn team uses nanoparticles to break up plaque and prevent cavities July 28th, 2016

Beating the heat a challenge at the nanoscale: Rice University scientists detect thermal boundary that hinders ultracold experiments July 28th, 2016

WSU researchers 'watch' crystal structure change in real time: Breakthrough made possible by new Argonne facility July 27th, 2016

Enhancing molecular imaging with light: New technology platform increases spectroscopic resolution by 4 fold July 27th, 2016

Interviews/Book Reviews/Essays/Reports/Podcasts/Journals/White papers

Penn team uses nanoparticles to break up plaque and prevent cavities July 28th, 2016

Beating the heat a challenge at the nanoscale: Rice University scientists detect thermal boundary that hinders ultracold experiments July 28th, 2016

Ageing can drive progress: Population ageing is likely to boost medicine, nanotechnology and robotics, but increase political risks July 27th, 2016

WSU researchers 'watch' crystal structure change in real time: Breakthrough made possible by new Argonne facility July 27th, 2016

Energy

New nontoxic process promises larger ultrathin sheets of 2-D nanomaterials July 27th, 2016

Designing climate-friendly concrete, from the nanoscale up: New understanding of concrete’s properties could increase lifetime of the building material, decrease emissions July 25th, 2016

An accelerated pipeline to open materials research: ORNL workflow system unites imaging, algorithms, and HPC to advance materials discovery and design July 24th, 2016

Researchers discover key mechanism for producing solar cells: Better understanding of perovskite solar cells could boost widespread use July 21st, 2016

Solar/Photovoltaic

New nontoxic process promises larger ultrathin sheets of 2-D nanomaterials July 27th, 2016

An accelerated pipeline to open materials research: ORNL workflow system unites imaging, algorithms, and HPC to advance materials discovery and design July 24th, 2016

Researchers discover key mechanism for producing solar cells: Better understanding of perovskite solar cells could boost widespread use July 21st, 2016

The future of perovskite solar cells has just got brighter -- come rain or shine: Korean researchers at POSTECH have succeeded in developing high-efficiency perovskite solar cells that retain excellent performance over two months in a very humid condition July 21st, 2016

NanoNews-Digest
The latest news from around the world, FREE




  Premium Products
NanoNews-Custom
Only the news you want to read!
 Learn More
NanoTech-Transfer
University Technology Transfer & Patents
 Learn More
NanoStrategies
Full-service, expert consulting
 Learn More











ASP
Nanotechnology Now Featured Books




NNN

The Hunger Project







Car Brands
Buy website traffic