3D graphene could replace expensive platinum in solar cells

One of the most promising types of solar cells has a few drawbacks. A scientist at Michigan Technological University may have overcome one of them.

Dye-sensitized solar cells are thin, flexible, easy to make and very good at turning sunshine into electricity. However, a key ingredient is one of the most expensive metals on the planet: platinum. While only small amounts are needed, at $1,500 an ounce, the cost of the silvery metal is still significant.

Yun Hang Hu, the Charles and Carroll McArthur Professor of Materials Science and Engineering, has developed a new, inexpensive material that could replace the platinum in solar cells without degrading their efficiency: 3D graphene.

The researchers determined that the 3D honeycomb graphene had excellent conductivity and high catalytic activity, raising the possibility that it could be used for energy storage and conversion.

The cell with the 3D graphene counter electrode converted 7.8 percent of the sun’s energy into electricity, nearly as much as the conventional solar cell using costly platinum (8 percent).

Source:
http://www.mtu.edu/news/stories/2013/august/story94626.html
http://www.kurzweilai.net/3d-graphene-could-replace-expensive-platinum-in-solar-cells

New rechargeable flow battery enables cheaper, large-scale energy storage

MIT researchers have engineered a new rechargeable flow battery that doesn’t rely on expensive membranes to generate and store electricity. The device, they say, may one day enable cheaper, large-scale energy storage.

“This technology has as much promise as anything else being explored for storage, if not more,” says Cullen Buie, an assistant professor of mechanical engineering at MIT. “Contrary to previous opinions that membraneless systems are purely academic, this system could potentially have a large practical impact.”

Buie, along with Martin Bazant, a professor of chemical engineering, and William Braff, a graduate student in mechanical engineering, have published their results this week in Nature Communications.

“Here, we have a system where performance is just as good as previous systems, and now we don’t have to worry about issues of the membrane,” Bazant says. “This is something that can be a quantum leap in energy-storage technology.”

Possible boost for solar and wind energy 

Low-cost energy storage has the potential to foster widespread use of renewable energy, such as solar and wind power. To date, such energy sources have been unreliable: Winds can be capricious, and cloudless days are never guaranteed. With cheap energy-storage technologies, renewable energy might be stored and then distributed via the electric grid at times of peak power demand.

According to preliminary projections, Braff and his colleagues estimate that the membraneless flow battery may produce energy costing as little as $100 per kilowatt-hour — a goal that the U.S. Department of Energy has estimated would be economically attractive to utility companies.

Source: http://web.mit.edu/newsoffice/2013/rechargeable-flow-battery-enables-cheaper-large-scale-energy-storage-0816.html

Vehicle-to-grid (V2G) system

Vehicle-to-grid (V2G) describes a system in which plug-in electric vehicles, such as electric cars (BEVs) and plug-in hybrids (PHEVs), communicate with the power grid to sell demand response services by either delivering electricity into the grid or by throttling their charging rate.[1][2]

Vehicle-to-grid can be used with such gridable vehicles, that is, plug-in electric vehicles (BEVs and PHEVs), with grid capacity. Since most vehicles are parked an average of 95 percent of the time, their batteries could be used to let electricity flow from the car to the power lines and back, with a value to the utilities of up to $4,000 per year per car.
BMW, Continental, Daimler, Fraunhofer, RWE, Siemens, TU Dortmund and VW – the partners in the new research project “eNterop” belong to the German industrial and research scene’s elite. They are now working with domestic proponents of international standardization of “vehicle-to-grid communication” (V2G) for electric vehicle networks on the next stage: an open test platform for the interface between electric vehicles and charging infrastructures. Their goal is the rapid establishment of standards for supply and communications systems between vehicles and electric power grids.

Electric vehicles will have to be able to communicate with grids reliably and charge or supply electricity at charging stations regardless of their make.

Sources:
http://www.iff.fraunhofer.de/en/press/press-releases/2013/electric-vehicles-network-standard.html
http://en.wikipedia.org/wiki/Vehicle-to-grid

Quantum-dot solar cells have great potential for solar cells

There has been great interest in recent years in using tiny particles called quantum dots to produce low-cost, easily manufactured, stable photovoltaic cells.

Now, for the most widely used type of quantum dots, made of compounds called metal chalcogenides, researchers from MIT may have found the key: The limiting factor seems to be off-kilter ratios of the two basic components that make up the dots.

The new findings — by Jeffrey Grossman, the Carl Richard Soderberg Associate Professor of Power Engineering, materials science and engineering graduate student Donghun Kim, and two other researchers — were reported this month in the journal Physical Review Letters.

There has been “a lot of excitement” about the potential for quantum dots in applications including electronic devices, lighting and solar cells, Grossman says. Among other potential advantages, quantum-dot solar cells could be made in a low-temperature process, by depositing material from a solution at room temperature, rather than the high-temperature, energy-intensive processes used for conventional photovoltaics. In addition, such devices could be precisely “tuned,” to obtain maximum conversion of specific wavelengths (colors) of light to energy, by adjusting the size and shape of the particles.

To go beyond the efficiencies achieved so far with quantum-dot solar cells, Grossman says, researchers needed to understand why the charges got trapped in the material. “We found something quite different than what people thought was causing the problem,” he says.

Giulia Galli, a professor of physics and chemistry at the University of California at Davis who was not connected with this research, says it is “quite a creative and important piece of work,” and adds that, “I'm pretty sure this will stimulate new experiments” to engineer the stoichiometry of quantum dots in order to control their properties.

In addition to Kim and Grossman, the work was carried out by former MIT postdoc Joo-Hyoung Lee, now at the Gwangju Institute of Science and Technology in South Korea, and Dong-Ho Kim of the Samsung Advanced Institute of Technology (SAIT) in Cambridge, Mass. The work was supported by SAIT, and is part of a larger quantum-dot solar cell program within the SAIT-MIT alliance that includes professors Vladimir Bulovic and Moungi Bawendi.

Source: http://web.mit.edu/newsoffice/2013/balance-key-to-making-quantum-dot-solar-cells-work-0524.html

Lithium-air battery four times as much energy per pound as today’s best lithium-ion batteries

Imaging reveals what happens during charging; could lead to improved batteries for electric cars.

One of the most promising new kinds of battery to power electric cars is called a lithium-air battery, which could store up to four times as much energy per pound as today’s best lithium-ion batteries.

Researchers at MIT and Sandia National Laboratories have used transmission electron microscope (TEM) imaging to observe, at a molecular level, what goes on during a reaction called oxygen evolution as lithium-air batteries charge; this reaction is thought to be a bottleneck limiting further improvements to these batteries. The TEM technique could help in finding ways to make such batteries practical in the near future.

The work is described in a Nano Letters paper by Robert Mitchell, who recently received a PhD in materials science and engineering from MIT; mechanical engineering PhD student Betar Gallant; Carl Thompson, the Stavros Salapatas Professor of Materials Science and Engineering; Yang Shao-Horn, the Gail E. Kendall Associate Professor of Mechanical Engineering and Materials Science and Engineering; and four other authors.

Faster charging

In fact, the rate of lithium peroxide oxidation in these experiments was approximately 100 times faster than the charging time for laboratory-scale lithium-air batteries, and approaches what is needed for applications. This demonstrates that if these batteries’ electron-transfer characteristics can be improved, it could allow for much faster charging while minimizing energy losses.

Source: http://web.mit.edu/newsoffice/2013/real-time-charging-of-lithium-air-battery-0513.html

Unleashing oxygen

‘Superlattice’ structure could give a huge boost to oxygen reaction in fuel cells, increasing their power potential.

New research at MIT could dramatically improve the efficiency of fuel cells, which are considered a promising alternative to batteries for powering everything from electronic devices to cars and homes.

Now that the MIT team has analysed LSC113/214, it may be possible to discover even better materials by conducting systematic searches, Yildiz says; the team is now working on that. “If we can crack this problem, then we can make great strides in improving the performance,” adds Tuller, a professor of ceramics and electronic materials in MIT’s Department of Materials Science and Engineering.

Source: http://web.mit.edu/newsoffice/2013/superlattice-could-boost-fuel-cell-performance-0430.html#.UYEEy6aZqe4.blogger

Major boost in solar-cell efficiency

Throughout decades of research on solar cells, one formula has been considered an absolute limit to the efficiency of such devices in converting sunlight into electricity: Called the Shockley-Queisser efficiency limit, it posits that the ultimate conversion efficiency can never exceed 34 percent for a single optimized semiconductor junction.

Now, researchers at MIT have shown that there is a way to blow past that limit as easily as today’s jet fighters zoom through the sound barrier — which was also once seen as an ultimate limit.

Their work appears this week in a report in the journal Science, co-authored by graduate students including Daniel Congreve, Nicholas Thompson, Eric Hontz and Shane Yost, alumna Jiye Lee ’12, and professors Marc Baldo and Troy Van Voorhis.

Since this was just a first proof of principle, the team has not yet optimized the energy-conversion efficiency of the system, which remains less than 2 percent. But ratcheting up that efficiency through further optimization should be a straightforward process, the researchers say. “There appears to be no fundamental barrier,” Thompson says.

While today’s commercial solar panels typically have an efficiency of at most 25 percent, a silicon solar cell harnessing singlet fission should make it feasible to achieve efficiency of more than 30 percent, Baldo says — a huge leap in a field typically marked by slow, incremental progress. In solar cell research, he notes, people are striving “for an increase of a tenth of a percent.”

Solar panel efficiencies can also be improved by stacking different solar cells together, but combining solar cells is expensive with conventional solar-cell materials. The new technology instead promises to work as an inexpensive coating on solar cells.

Source: http://web.mit.edu/newsoffice/2013/photon-to-electron-conversion-0418.html?utm_source=feedly

New world-record efficiency for thin-film silicon solar cells

EPFL’s Institute of Microengineering has reached a remarkable 10.7% efficiency for a single-junction microcrystalline silicon solar cell, surpassing the previous world record of 10.1% held by the Japanese company Kaneka Corporation since 1998.

The efficiency increase was also achieved with with only 1.8 microns of photovoltaic active material — 100 times less material than with standard wafer-based crystalline silicon PV technology.

Thin-film silicon technology indeed offers the advantages of saving up on raw material and offering low energy payback time, thus allowing module production prices as low as 35 €/m2 (47 $/m2), reaching the price level of standard roof tiles.

Work leading to this result was supported by the Swiss Federal Office of Energy (SFOE), the EU-FP7 program, the Swiss National Science Foundation (SNSF), and the Commission for Technology and Innovation (CTI).

Source: http://www.kurzweilai.net/new-world-record-efficiency-for-thin-film-silicon-solar-cells

Flexible, light solar cells could provide new opportunities

MIT researchers have produced a new kind of photovoltaic cell based on sheets of flexible graphene coated with a layer of nanowires. The approach could lead to low-cost, transparent and flexible solar cells that could be deployed on windows, roofs or other surfaces.

The new approach is detailed in a report published in the journal Nano Letters, co-authored by MIT postdocs Hyesung Park and Sehoon Chang, associate professor of materials science and engineering Silvija Gradečak, and eight other MIT researchers.

While most of today’s solar cells are made of silicon, these remain expensive because the silicon is generally highly purified and then made into crystals that are sliced thin. Many researchers are exploring alternatives, such as nanostructured or hybrid solar cells; indium tin oxide (ITO) is used as a transparent electrode in these new solar cells.

The new material, Gradečak says, may be an alternative to ITO. In addition to its lower cost, it provides other advantages, including flexibility, low weight, mechanical strength and chemical robustness.

Source: http://web.mit.edu/newsoffice/2012/hybrid-flexible-light-solar-cells-1221.html

Solar energy and batteries

Scientists develop fast recharging material for lithium-ion batteries
A group of South Korean scientists has developed a new material for a secondary or rechargeable battery that can be fully recharged in just a matter of minutes. The new battery, on the other hand, uses the same type of nanoparticle materials that are first resolved in a solution that contains graphite, which later is carbonized to form a dense network of conductors all throughout the electrodes of the battery.

As a result, all energy-holding particles of the new battery start recharging simultaneously while the same particles in conventional batteries begin recharging in order from the outermost particles to the innermost. This cuts down on the time needed to recharge the new type of battery to between 1/30 and 1/120 of that of existing rechargeable batteries.

The research team, partly funded by the science ministry, also includes four doctoral students of the Ulsan university -- Lee Sang-han, Cho Yong-hyun, Song Hyun-kon and Lee Kyu-tae. Their paper, titled "Carbon-Coated Single-Crystal LiMn2O4 Nanoparticle Clusters as Cathode Material for High-Energy and High-Power Lithium-Ion Batteries," was published earlier this month in the international edition of the weekly journal Angewandte Chemie.

Bron: http://english.yonhapnews.co.kr/techscience/2012/08/13/8/0601000000AEN20120813001600320F.HTML

Update: 06-06-2012
Solar Impulse’s first intercontinental landingTAKE-OFF TIME: 05:22 (UTC+2) 05.06.12
LANDING TIME:  23:30 (UTC+1) 05.06.12
FLIGHT DURATION: 19 H 8 MIN
AVERAGE GROUND SPEED: 51,8 KM/H
HIGHEST ALTITUDE REACHED: 8’229 M (27’000 FT)
FLIGHT DISTANCE: 830 KM

“This flight marks a new stage in the history of the project because we have reached another continent,” added André Borschberg, in consensus with Mr. Bakkoury’s comments “After almost 20 hours of flight we landed with a full set of batteries. This is extraordinary as it represents an increase in confidence in new technologies."

Source: http://solarimpulse.com/

Datum: 27-04-2012
Liquid batteries to store wind and solar energy



Renewable energies have great potential to solve diminishing natural resources but they are unreliable - if the wind doesn't blow or the sun doesn't shine they simply don't work.

But imagine if the energy that they generate could be stored in a giant battery?

Such a battery would need to be to be low-cost, a problem which has until now prevented such developments.

"In the past battery research has been driven by advanced chemistry that was expensive with the hope that mass production would see the price fall.

"The major difference with my group was that we would only consider components that have a chance of meeting the right price point," said Prof Sadoway.

Source:
http://www.bbc.co.uk/news/technology-17214914
http://lmbcorporation.com/
http://www.thegatesnotes.com/Topics/Energy/We-Need-A-Battery-Miracle

Update: 27-APR-2012

“The way things stand, electricity demand must be in balance with electricity supply.” The problem is: coal and nuclear plants can’t address demand fast enough. How do we deal with the problem of intermittency?

Sadoway thinks he has the answer, and in this hugely well-received talk, he outlines his invention of a liquid metal battery he thinks might act as a blueprint for the future. “If we’re going to get this country out of its current energy situation, we can’t conserve our way out, we can’t drill our way out, we can’t bomb our way out. We’re going to do it the old-fashioned American way: we’re going to invent our way out, working together,” says MIT professor, Donald Sadoway.

The 36-inch-wide “Bistro Table” battery is not yet ready for prime time, but a future variant is designed to produce the daily electrical needs of 200 American households with a battery that is “silent, emissions free, has no moving parts, is remotely controlled, and is designed to the market price point, without subsidy.” 

Source: TED Blog | Reinventing the battery: Donald Sadoway at TED2012

Datum: 24-Feb-2012
Light management leads to ultra-efficient solar cells, possibly 70%

It has long been thought that conversion efficiency of solar cells cannot exceed 34 percent. A thermodynamic limit is responsible for this practical limitation. By clever light management, however, an efficiency of 70 percent is achievable.
How this can be done is described by AMOLF director Albert Polman and his colleague Harry Atwater from the California Institute of Technology in a commentary article in Nature Materials that appears on Tuesday, February 21.

A solar cell is a device that converts sunlight into electrical power. This conversion process, however, is not very efficient: in a conventional solar cell a large fraction of the energy of the sunlight is lost. Blue and green light are converted to electricity with an efficiency less than 50%, while infrared light is not absorbed by a solar cell at all. The highest efficiency realized by a silicon solar cell is only 27 percent.

Albert Polman: "The solar cell community is very conservative. It is often assumed that only extremely simple solar cells can be made at low costs. But if you can reach an efficiency larger than 50% a much higher cost of the solar cell is acceptable. Solar panels with a high efficiency take up much less space, because you need fewer panels to generate the same amount of power. That saves costs of land, installation and infrastructure. With a slightly more complex solar cell it becomes possible to convert all colors of the light from the sun to electricity. An efficiency of 70% is achievable.

Bron: http://www.amolf.nl/news/detailpage/article/light-management-leads-to-ultra-efficient-solar-cells//chash/7ece18f9a69a891cddf38b40498927a1/

'Artificial leaf' makes cheap and clean energy from water

'Artificial leaf' makes hydrogen from solar cell | Green Tech - CNET News
Massachusetts Institute of Technology professor Daniel Nocera thinks he can draw cheap and clean energy from water.
At the National Meeting of the American Chemical Society, Nocera yesterday presented results from research on making an "artificial leaf" to split water to get hydrogen fuel and oxygen. The goal is to use the solar cell to make hydrogen, which would be stored and then used in a fuel cell to make electricity.

Read more: http://news.cnet.com/8301-11128_3-20047814-54.html#ixzz1Hu2G2Jpq

MIT's new paper chase: Cheap solar cells | Green Tech - CNET News

MIT's new paper chase: Cheap solar cells | Green Tech - CNET News

MIT showed prototypes of paper solar cells able to generate enough current to light a small LED display. A commercial solar paper device could be available in five years, said chemical engineering professor Karen Gleason, whose lab is doing the work.

Read more: http://news.cnet.com/8301-11128_3-20019885-54.html#ixzz12oep383v

Silicon Ink to generate power

Innovalight is working on a product called "Silicon Ink" that can be used to replace solar cells. According to the company the product is a lot more environmentally friendly and a lot more flexible than the current solar panels.

This invention has the potential to become an additional power source for mobile devices.

Key attributes of silicon nanocrystals:
Tunable (absorption and emission wavelengths)

• Non toxic
• Solution process capable
• Stable and reliable
• Low cost manufacturing

Red Harring: Conrad Burke’s InnovaLight is aiming to mobilize the solar power market