MIT Perfects The Low Cost Artificial Leaf

Back in July 2011 we published an exciting little post on MIT’s work with artificial leaves - MITs Artificial Leaf  - based on a silicon solar cell.

The leaf consists of a thin, flat, three-layered silicon solar cell with catalysts bonded to both faces of the silicon. Placed in water and exposed to sunlight, silicon absorbs photons of sunlight, generating electrons with enough energy to conduct through the silicon.

The process leaves behind positively charged electron vacancies called “holes” that can also move through the material. The holes migrate to a cobalt-containing catalyst painted on one face of the silicon cell, where they strip electrons from water molecules, breaking them into hydrogen ions (H+), and oxygen atoms. The catalyst then knits pairs of oxygens together to make O2. Meanwhile, the H+ ions migrate to another catalyst on the opposite face of the silicon cell, where they combine with conducting electrons to make molecules of H2. In principle, the H2 can then be stored and either burned or run through a fuel cell to generate electricity.

This is Photocatalytic water splitting, world meet the ARTIFICIAL LEAF!

Professor Daniel Nocera’s work has finally borne fruit. Nocera’s team developed the catalyst three years ago, the first practical artificial leaf has now been developed, and this new technology may help to deliver efficient carbon neutral energy to the world’s poor and developing nations.

Building on their previous research, the researchers at MIT in Boston have created an artificial leaf that, unlike earlier devices is made from inexpensive materials, and employs  low-cost engineering and manufacturing processes :: Read the full article »»»»

Online Education Revolution, MITx

In the world of Science and Technology three little letters on your resume can make all the difference, especially if those three letters are MIT.  Massachusetts Institute of Technology - MIT – is one of the worlds leading education institutions  that is also a powerhouse for research and development. Not only are MIT’s course subjects leading edge but the way courses are being delivered is going through an online revolutionary.

MIT’s latest education initiative, MITx isn’t just a platform to make their courses available online, they’ve been doing that for 10 years through the OpenCourseWare – OCW – program that has served over 2,100 courses to more than 100 million people world-wide. Instead MITx is a complete open source education platform. Other education institutions – public or private -  are free to join and integrate MITx into their own education platform.

“MIT has long believed that anyone in the world with the motivation and ability to engage MIT coursework should have the opportunity to attain the best MIT-based educational experience that Internet technology enables. OpenCourseWare’s great success signals high demand for MIT’s course content and propels us to advance beyond making content available. MIT now aspires to develop new approaches to online teaching.” said MIT President Susan Hockfield Read the full article »»»»

MIT Simplified 3D Nano-structure Building

The making of three-dimensional nanostructured materials  - structures that have distinctive shapes at insane scales of a few billionths of a meter — has become a fertile area of research, producing materials that are useful for electronics, photonics, phononics and biomedical devices. But the methods of making such materials have been limited in the 3-D complexity they can produce. An MIT team has found a way to produce more complicated structures by using a blend of current “top-down” and “bottom-up” approaches.

The work is described in a paper published in June in the journal Nano Letters, co-authored by postdoc Chih-Hao Chang; George Barbastathis, the Singapore Research Professor of Optics and Professor of Mechanical Engineering; and six MIT graduate students.

One approach to making three-dimensional nanostructures — a top-down approach — is called phase-shift lithography, in which a two-dimensional mask shapes the intensity of light shining onto a layer of photoresist material (in the same way a photographic negative controls the amount of light reaching different areas of a print). The photoresist is altered only in the areas reached by the light. However, this approach requires very precisely manufactured phase masks, which are expensive and time-consuming to make. Read the full article »»»»

MIT’s Themo Photovoltaic

Power, electrical power is the life blood of our modern world, a constant heartbeat that drives every gadget on the planet. MIT scientist have demonstrated a huge breakthrough in power, a Zippo lighter sized power station that’s three times as powerful as lithium-ion batteries and runs off a tiny cap of methanol. The technology behind the tiny device is able to convert any source of heat into electricity. Called a Thermo-Photovoltaic system – TPV -, the Zippo generator is able to convert heat into specific frequencies of light which is used by a tuned PV cell – solar cell – to generate electricity. While it may sound complicated, there are no moving parts, nothing to wear out and it is made of cheap materials. The team of MIT researchers have managed to produce a cheap and efficient take on the technology previously only available to NASA. Will the Zippo make a come back as every iPhones best friend, maybe.

Themo-Photovoltaic cells – TPV – like the Zippo convert heat into photons which are converted to electricity by solar cell like layer. First demonstrated in 1956 by Henry Kolm, TPV’s didn’t become practical to produce until Pierre Aigrain’s lectures on the subject in 1960. While the basic TPV principle here is the same the technology leap here is based on very tiny holes etched into tungsten. The source of the heat used by this system is virtually unlimited, a camp-fire battery charger could be placed near a fire to charge your phone, exhaust heat from combustion engines becomes a power source. The most contentious heat source of all can even be used, sources of the radioactive type. Used for a long time in space craft there are actually radioactive variants that are very safe, last 30-50 years and burn the radioactive material completely. Read the full article »»»»

MIT’s Sun Free Photovoltaic

A new photovoltaic energy-conversion system developed at MIT can be powered solely by heat, generating electricity with no sunlight at all. While the principle involved is not new, a novel way of engineering the surface of a material to convert heat into precisely tuned wavelengths of light — selected to match the wavelengths that photovoltaic cells can best convert to electricity — makes the new system much more efficient than previous versions.

The key to this fine-tuned light emission, described in the journal Physical Review A, lies in a material with billions of nanoscale pits etched on its surface. When the material absorbs heat — whether from the sun, a hydrocarbon fuel, a decaying radioisotope or any other source — the pitted surface radiates energy primarily at these carefully chosen wavelengths.

Based on that technology, MIT researchers have made a button-sized power generator fueled by butane that can run three times longer than a lithium-ion battery of the same weight; the device can then be recharged instantly, just by snapping in a tiny cartridge of fresh fuel. Another device, powered by a radioisotope that steadily produces heat from radioactive decay, could generate electricity for 30 years without refueling or servicing — an ideal source of electricity for spacecraft headed on long missions away from the sun.

According to the U.S. Energy Information Administration, 92 percent of all the energy we use involves converting heat into mechanical energy, and then often into electricity — such as using fuel to boil water to turn a turbine, which is attached to a generator. But today’s mechanical systems have relatively low efficiency, and can’t be scaled down to the small sizes needed for devices such as sensors, smartphones or medical monitors.

“Being able to convert heat from various sources into electricity without moving parts would bring huge benefits,” says Ivan Celanovic ScD ’06, research engineer in MIT’s Institute for Soldier Nanotechnologies (ISN), “especially if we could do it efficiently, relatively inexpensively and on a small scale.”

It has long been known that photovoltaic (PV) cells needn’t always run on sunlight. Half a century ago, researchers developed thermophotovoltaics (TPV), which couple a PV cell with any source of heat: A burning hydrocarbon, for example, heats up a material called the thermal emitter, which radiates heat and light onto the PV diode, generating electricity. The thermal emitter’s radiation includes far more infrared wavelengths than occur in the solar spectrum, and “low band-gap” PV materials invented less than a decade ago can absorb more of that infrared radiation than standard silicon PVs can. But much of the heat is still wasted, so efficiencies remain relatively low. 

The solution, Celanovic says, is to design a thermal emitter that radiates only the wavelengths that the PV diode can absorb and convert into electricity, while suppressing other wavelengths. “But how do we find a material that has this magical property of emitting only at the wavelengths that we want?” asks Marin Soljačić, professor of physics and ISN researcher. The answer: Make a photonic crystal by taking a sample of material and create some nanoscale features on its surface — say, a regularly repeating pattern of holes or ridges — so light propagates through the sample in a dramatically different way.

“By choosing how we design the nanostructure, we can create materials that have novel optical properties,” Soljačić says. “This gives us the ability to control and manipulate the behavior of light.”

The team — which also includes Peter Bermel, research scientist in the Research Laboratory for Electronics (RLE); Peter Fisher, professor of physics; and Michael Ghebrebrhan, a postdoc in RLE — used a slab of tungsten, engineering billions of tiny pits on its surface. When the slab heats up, it generates bright light with an altered emission spectrum because each pit acts as a resonator, capable of giving off radiation at only certain wavelengths.

This powerful approach — co-developed by John D. Joannopoulos, the Francis Wright Davis Professor of Physics and ISN director, and others — has been widely used to improve lasers, light-emitting diodes and even optical fibers. The MIT team, supported in part by a seed grant from the MIT Energy Initiative, is now working with collaborators at MIT and elsewhere to use it to create several novel electricity-generating devices.

Mike Waits, an electronics engineer at the Army Research Laboratory in Adelphi, Md., who was not involved in this work, says this approach to producing miniature power supplies could lead to lighter portable electronics, which is “critical for the soldier to lighten his load. It not only reduces his burden, but also reduces the logistics chain” to deliver those devices to the field. “There are a lot of lives at stake,” he says, “so if you can make the power sources more efficient, it could be a great benefit.”

The button-like device that uses hydrocarbon fuels such as butane or propane as its heat source — known as a micro-TPV power generator — has at its heart a “micro-reactor” designed by Klavs Jensen, the Warren K. Lewis Professor of Chemical Engineering, and fabricated in the Microsystems Technology Laboratories. While the device achieves a fuel-to-electricity conversion efficiency three times greater than that of a lithium-ion battery of the same size and weight, Celanovic is confident that with further work his team can triple the current energy density. “At that point, our TPV generator could power your smartphone for a whole week without being recharged,” he says.

Celanovic and Soljačić stress that building practical systems requires integrating many technologies and fields of expertise. “It’s a really multidisciplinary effort,” Celanovic says. “And it’s a neat example of how fundamental research in materials can result in new performance that enables a whole spectrum of applications for efficient energy conversion.”

source: MIT

source: David L. Chandler

Source: Nancy W. Stauffer 

………..


……….

MIT’s Printable Paper Solar Cell

Clearly always inovating,  MIT has developed materials that make it possible to produce photovoltaic cells on paper, nearly as simply as printing a document.

Almost as cheaply and easily as printing a photo on your inkjet, an inexpensive, simple solar cell has been created on that flimsy sheet, formed from special “inks” deposited on the paper. You can even fold it up to slip into a pocket, then unfold it and watch it generating electricity again in the sunlight. The new technology, developed by a team of researchers at MIT, is reported in a paperin the journal Advanced Materials, published online July 8. The paper is co-authored by Karen Gleason, the Alexander and I. Michael Kasser Professor of Chemical Engineering; Professor of Electrical Engineering Vladimir Bulović; graduate student Miles Barr; and six other students and postdocs. The work was supported by the Eni-MIT Alliance Solar Frontiers Program and the National Science Foundation.

The technique represents a major departure from the systems used until now to create most solar cells, which require exposing the substrates to potentially damaging conditions, either in the form of liquids or high temperatures. The new printing process uses vapors, not liquids, and temperatures less than 120 degrees Celsius. These “gentle” conditions make it possible to use ordinary untreated paper, cloth or plastic as the substrate on which the solar cells can be printed.The resilient solar cells still function even when folded up into a paper airplane. In their paper, the MIT researchers also describe printing a solar cell on a sheet of PET plastic (a thinner version of the material used for soda bottles) and then folding and unfolding it 1,000 times, with no significant loss of performance. By contrast, a commercially produced solar cell on the same material failed after a single folding. Read the full article »»»»

MITs Artificial Leaf

Scientists at MIT have demonstrated the first practical artificial leaf. This doesn’t mean the oak tree out the front of your house should be worried, these leaves will never hang from a branch.

Nor do they look like a leaf, with a silicon cell immersed in a cylinder of bubbling water they are more laboratory ready than they are garden ready. Instead of simply using the solar cell to produce electricity the cells use a special coating on the silicon along with the power from the cell to split the water into its hydrogen and oxygen components.

Being able to directly convert water and sunlight into storable gas provides solutions to the biggest problems with solar power, no light no power. At night the gas could be fed to a fuel cell to convert the gases back into electricity and water. The holy grail of renewable power just got one step closer.

Based on a silicon solar cell with a special catalyst coated on the surface, professor Daniel Nocera developed the catalyst three years ago. The  catalyst and electricity interact to cause the water to split into hydrogen and oxygen ready to be stored :: Read the full article »»»»