Rice unveils super-efficient solar-energy technology: Solar Steam

Rice University scientists have unveiled a revolutionary new technology that uses nanoparticles to convert solar energy directly into steam.

The new “solar steam” method from Rice’s Laboratory for Nanophotonics (LANP) is so effective it can even produce steam from icy cold water.

Details of the solar steam method were published online today in ACS Nano. The technology has an overall energy efficiency of 24 percent. Photovoltaic solar panels, by comparison, typically have an overall energy efficiency around 15 percent. However, the inventors of solar steam said they expect the first uses of the new technology will not be for electricity generation but rather for sanitation and water purification in developing countries.

“This is about a lot more than electricity,” said LANP Director Naomi Halas, the lead scientist on the project. “With this technology, we are beginning to think about solar thermal power in a completely different way.”

The efficiency of solar steam is due to the light-capturing nanoparticles that convert sunlight into heat. When submerged in water and exposed to sunlight, the particles heat up so quickly they instantly vaporize water and create steam. Halas said the solar steam’s overall energy efficiency can probably be increased as the technology is refined.

“We’re going from heating water on the macro scale to heating it at the nanoscale,” Halas said. “Our particles are very small — even smaller than a wavelength of light — which means they have an extremely small surface area to dissipate heat. This intense heating allows us to generate steam locally, right at the surface of the particle, and the idea of generating steam locally is really counterintuitive.”

To show just how counterintuitive, Rice graduate student Oara Neumann videotaped a solar steam demonstration in which a test tube of water containing light-activated nanoparticles was submerged into a bath of ice water. Using a lens to concentrate sunlight onto the near-freezing mixture in the tube, Neumann showed she could create steam from nearly frozen water.

Steam is one of the world’s most-used industrial fluids. About 90 percent of electricity is produced from steam, and steam is also used to sterilize medical waste and surgical instruments, to prepare food and to purify water.

Most industrial steam is produced in large boilers, and Halas said solar steam’s efficiency could allow steam to become economical on a much smaller scale.

People in developing countries will be among the first to see the benefits of solar steam. Rice engineering undergraduates have already created a solar steam-powered autoclave that’s capable of sterilizing medical and dental instruments at clinics that lack electricity. Halas also won a Grand Challenges grant from the Bill and Melinda Gates Foundation to create an ultra-small-scale system for treating human waste in areas without sewer systems or electricity.

“Solar steam is remarkable because of its efficiency,” said Neumann, the lead co-author on the paper. “It does not require acres of mirrors or solar panels. In fact, the footprint can be very small. For example, the light window in our demonstration autoclave was just a few square centimeters.”

Another potential use could be in powering hybrid air-conditioning and heating systems that run off of sunlight during the day and electricity at night. Halas, Neumann and colleagues have also conducted distillation experiments and found that solar steam is about two-and-a-half times more efficient than existing distillation columns.

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via Rice University
 

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Egyptian Student Finds New Way to Solar Energy

He’s a young man from Egypt who refused to give in to hard conditions that threatened his passion for science.

Though the unprofessional educational system forced him to study something he doesn’t like, yet he succeeded in swimming against the stream and came up with an idea of a new remarkable invention that could benefit humanity.

Mohamed Gooda, 24, was born in El Faiyoum, in north central Egypt. Although he studies commerce, the love he has for science always drives him to read science books, and this has directed him to come up with a new concept in the field of solar energy and solar panels, which he’s currently trying to make it real in the hands of ordinary individuals.

What are the concepts and the idea of your invention?

The idea of my invention is based upon the concept of “Stimulated Emission of Electrons”, a theoretical physics expression which first appeared in 1999 in a research that was conducted by three scientists and got published in the “Brazilian Journal of Physics”. The expression is concerned with a kind of solid matters which are able to stimulate the Secondary Electrons in a range between zero and 50 volts.

Afterwards, the expression appeared once again in 2006 in a research published on a website, Archive.org, and was focused on sodium electrons and stimulating them.

Some researchers who interpreted my idea mistakenly thought that I use laser instead of sunlight and solar radiation as a source of energy for the solar cells, but this is not the concept of my new laser solar cells. This new solar cell uses the similar mechanism of how laser works through stimulated emission of electrons, yet, it’s based upon electrons and not photons like in laser. This takes place through special organising of the properties of the cesium sola cell.

What’s the difference between your new laser solar cells and the old photovoltaic solar panels?

Cesium solar cells and other photovoltaic panels are manufactured to work, but with dependence on the photoelectric effect. This simply means that there are some chemical elements which have “easy-going” electrons at their outer electron shells that get stimulated and freed easily at little amount of energy. Meaning that such cells directly converts the luminous energy to electric energy.

An important aspect of solar cells is the energy conversion efficiency which indicates the powerfulness of the solar cell. So far, all the previous types of solar panels don’t exceed the production of just 40% of the input solar energy gathered by them.

On the contrary, according to my theoretical research’s calculations and equations, the energy conversion efficiency of my laser solar cell reaches 70%. Furthermore, its cost doesn’t exceed the ones of the old photovoltaic panels except for around 10% that represents the increase of energy produced by the new cell. Moreover, about 90% of the currently used solar panels are made of silicon which is a very expensive element. Instead of that, I manage to use organic photoelectric cells which are cheaper.

Additionally, next August God Willing, I’ll start trying to advance my new laser solar cells to make them able to absorb and benefit from additional five types of spectrum, beside the already used visible light. This is actually a revolutionary idea which is still being experimented in some physics labs which aim to make use of 3 types of spectra beside the visible light of sunlight.

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via OnIslam
 

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New nanocrystals let solar panels generate electricity and hydrogen gas

These are very durable crystals compared to their organic counterparts

At first glance, photovoltaic solar panels are brilliant. They’re self-contained, need no fuel and so long as the sun is shining, they make lots of lovely electricity. The trouble is, they’re expensive to make, batteries are poor storage systems for cloudy days, and the panels have a very short service life. Now, Dr. Mikhail Zamkov of Ohio’s Bowling Green State University and his team have used synthetic nanocrystals to make solar panels more durable as well as capable of producing hydrogen gas.

Solar panels using inorganic molecules as part of their construction have a short service life. The effects of UV radiation and heat degrade them, and they end up with a life of only about 20 years. Given how expensive it is to make solar panels, it’s not surprising that the cost per kilowatt is so much higher than conventional energy sources. In a video paper published in theJournal of Visualized Experiments (JoVE), Zamkov outlines his team’s process that involves replacing the organic molecules with two inorganic nanocrystals made from zinc selenide and cadmium sulfide, with a platinum catalyst added.

According to Zamkov, “The main advantage of this technique is that it allows for direct, all inorganic coupling of the light absorber and the catalyst.” In other words, these are very durable crystals compared to their organic counterparts. Not only are they less susceptible to heat and UV radiation, they also don’t suffer from degradation problems that plague their organic counterparts – where those are often irreversibly “poisoned” while in service, the nanocrystals can be recharged with a methanol wash.

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via Gizmag – David Szondy
 

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Solar energy covers turn maxed-out landfills into solar farms

Light on Landfills

Hickory Ridge landfill outside of Atlanta, GA, is full. Like most landfills that reach capacity, it was capped to contain its noxious mix of debris that will slowly degrade over the decades and centuries to come. But unlike most, Hickory Ridge glistens on a sunny day due its over 7,000 thin-film photovoltaic solar panels plastered to a geomembrane that has been stretched over the hill like a swim cap.

The goal for this new capping system is to create an alternative to traditional landfill covers that will create revenue, boost renewable energy use, and utilize obsolete land, said Mark Roberts, Senior Project Manager for HDR Engineering Inc., the company which developed the technology.

Normally when a landfill closes, the waste is sealed using a polyethylene cap, buried under a couple feet of compacted soil and seeded with grass. The grassy knoll is then effectively useless, albeit somewhat pleasing to the eye.

In contrast, a solar energy cover aims to eliminate the typical maintenance costs of mowing and soil replacement, and instead allows a closed landfill to continue being useful by generating revenue through renewable energy production. This new system uses a durable geomembrane constructed for roofs and fastens it to the landfill with vertical anchor trenches. The geomembrane-covered landfill slopes then serve as a secure and clean surface for the solar panels.

Much of the cost associated with solar caps occurs during the initial stage of buying and installing the solar panels (the project at Hickory Ridge cost roughly $5 million, $2 million of which was offset by federal stimulus money through the Georgia Environmental Finance Authority). This cost (Republic Services, the owner of Hickory Ridge landfill, was unable to disclose the agreed rate) will slowly be regained as the solar energy is sold back to the local utility.

This is exactly what’s taking place at Hickory Ridge. It’s now the world’s largest solar cap, producing 1 megawatt (MW) of electricity, which is enough to power about 225 homes, or offset the total energy use of the landfill itself. And, it’s not the lone example.

The first solar energy cover was installed in San Antonio, TX., in 2008 at a landfill called Tessman Road. Others exist in Mass., NY, and NJ. According to the Environmental Protection Agency, there are about 10,000 old municipal landfills in the United States that could potentially serve as the groundwork for renewable energy projects. Many of these landfills are located on the outskirts of cities and already possess the necessary infrastructure for solar power. Hickory Ridge landfill did.

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via Scientific American – Robynne Boyd

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Hybrid Solar System Makes Rooftop Hydrogen

While roofs across the world sport photovoltaic solar panels to convert sunlight into electricity, a Duke University engineer believes a novel hybrid system can wring even more useful energy out of the sun’s rays.

Instead of systems based on standard solar panels, Duke engineer Nico Hotz proposes a hybrid option in which sunlight heats a combination of water and methanol in a maze of glass tubes on a rooftop. After two catalytic reactions, the system produces hydrogen much more efficiently than current technology without significant impurities. The resulting hydrogen can be stored and used on demand in fuel cells.

For his analysis, Hotz compared the hybrid system to three different technologies in terms of their exergetic performance. Exergy is a way of describing how much of a given quantity of energy can theoretically be converted to useful work.

“The hybrid system achieved exergetic efficiencies of 28.5 percent in the summer and 18.5 percent in the winter, compared to 5 to 15 percent for the conventional systems in the summer, and 2.5 to 5 percent in the winter,” said Hotz, assistant professor of mechanical engineering and materials science at Duke’s Pratt School of Engineering.

The paper describing the results of Hotz’s analysis was named the top paper during the ASME Energy Sustainability Fuel Cell 2011 conference in Washington, D.C. Hotz recently joined the Duke faculty after completing post-graduate work at the University of California-Berkeley, where he analyzed a model of the new system. He is currently constructing one of the systems at Duke to test whether or not the theoretical efficiencies are born out experimentally.

Hotz’s comparisons took place during the months of July and February in order to measure each system’s performance during summer and winter months.

Like other solar-based systems, the hybrid system begins with the collection of sunlight. Then things get different. While the hybrid device might look like a traditional solar collector from the distance, it is actually a series of copper tubes coated with a thin layer of aluminum and aluminum oxide and partly filled with catalytic nanoparticles. A combination of water and methanol flows through the tubes, which are sealed in a vacuum.

“This set-up allows up to 95 percent of the sunlight to be absorbed with very little being lost as heat to the surroundings,” Hotz said. “This is crucial because it permits us to achieve temperatures of well over 200 degrees Celsius within the tubes. By comparison, a standard solar collector can only heat water between 60 and 70 degrees Celsius.”

Once the evaporated liquid achieves these higher temperatures, tiny amounts of a catalyst are added, which produces hydrogen. This combination of high temperature and added catalysts produces hydrogen very efficiently, Hotz said. The resulting hydrogen can then be immediately directed to a fuel cell to provide electricity to a building during the day, or compressed and stored in a tank to provide power later.

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