You are browsing the archives of 2009 September.

A nitride thin film semiconductor material technology captures a wider spectrum of the sun's solar spectrum. (Credit: RoseStreet Labs Energy.)

A Phoenix company said it has created a hybrid solar cell that pairs a gallium-nitride thin film with typical silicon-based PV technology to produce a single unit it claims can achieve an efficiency of 25 percent to 30 percent.

RoseStreet Labs Energy announced the prototype cell Monday, and it expects to start commercial production late 2010, says Bob Forcier, CEO of RoseStreet. When those cells come off the first production line, they should be able to convert 25 percent to 30 percent of the sunlight that falls on them into electricity, he adds.

That kind of efficiency would be significantly greater than what the best silicon cells on the market can achieve today. Currently, the most efficient silicon cells for sale come from San Jose, Calif.-based SunPower, whose cells have 22.5 percent efficiency.

There are other types of cells that use alternative materials and perform much better than SunPower’s, but they also are much more expensive and are developed mostly for solar panels on satellites. The majority of the solar cells on the market today are made with silicon, and their efficiencies are typically in the mid-teens.

RoseStreet’s idea is that by adding a layer of gallium-nitride, PV panels can be tuned to make use of photons from a broader range of spectrum. “With gallium-nitride you can tune it for whatever [part of the spectrum] you want. It’s like a piano versus the ukulele – you get more notes with the piano,” Forcier says. “This technology allows silicon to be supercharged, like adding a big booster without a big cost penalty.”

Gallium-nitride is a common material for making LEDs, so sourcing it wouldn’t pose a challenge, he notes.

The company’s core technology came from Cornell University and the Lawrence Berkeley National Lab. RoseStreet’s chief technical officer is Wladek Walukiewicz, who also serves as a senior scientist at LBNL. Walukiewicz reached LBNL via the Warsaw Institute and at the Massachusetts Institute of Technology.

When the company announced its licensing agreement in 2005, it said the technology could lead to solar energy conversion efficiencies greater than 48 percent.

Although RoseStreet claims it will start production of the hybrid panels in late 2010, it could license its technology to other silicon makers that seek ways to significantly boost their products’ performance, Forcier says.

Interestingly, RoseStreet says its technology is not a one-trick pony. Two weeks ago, the company also announced that it had discovered a way to use a nitride thin film-based photoelectrochemical cell to produce hydrogen gas directly from sunlight.

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We first wrote about the aerogel work of David Schiraldi’s group at CWRU back in June. Now the school and university have produced a great little video about basic steps of processing the materials and some of the applications that have been developed. The possibilities include lightweight kitty litter, green insulation and much more.

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I don’t know much about this other than what was posted at PNNL’s website last week, but I hope to see something published on this soon:

Researchers would like to develop lithium-ion batteries using titanium dioxide, an inexpensive material. But titanium dioxide on its own doesn’t perform well enough to replace the expensive, rare-earth metals or fire-prone carbon-based materials used in today’s lithium-ion batteries. To test whether graphene, a good conductor on its own, can help, PNNL’s Gary Yang and colleagues added graphene, sheets made up of single carbon atoms, to titanium dioxide. When they compared how well the new combination of electrode materials charged and discharged electric current, the electrodes containing graphene outperformed the standard titanium dioxide by up to three times. Graphene also performed better as an additive than carbon nanotubes. Yang discussed this work and provided an overview of the field of electrical storage materials.

Just for the record, it appears from a note on the website that ACerS member Jun Liu partnered with Yang on this research. Yang recently spoke at Oregon State University’s “Micro Nano Breakthrough Conference” held last week in Portland, Ore.

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Volvo C30 battery layout

Volvo Cars is currently evaluating the viability of a fully battery-electric vehicle. This year, Volvo has built and is internally testing a small number of prototype versions of a BEV version of its C30. In addition to focusing on performance and safety, much of the focus is on integration of the electric propulsion system with the rest of the car.

Lennart Stegland, director of Volvo Cars Special Vehicles, said in corporate statement: “The Volvo C30 is the first model we will try out with electric power. This car’s excellent properties in city traffic and its relatively low weight make it particularly suitable, since electric cars are primarily expected to be used in and around cities and for daily commuting.”

Volvo’s battery choice for the C30 BEV is designed and developed in the U.S. by EnerDel, Inc., Ener1’s U.S. battery subsidiary. This adds to the recently announced collaboration with Volvo on the V70 model plug-in hybrid demonstration vehicles being road tested in Europe starting this fall, which are also using the EnerDel lithium-ion batteries.

Volvo C30 BEV

EnerDel’s EV chemistry, hard carbon and mixed oxide in a lithium-ion battery pack, yields gross nominal power of 24 kWh lithium-ion battery pack and is said to be considering a 12 kWh pack. The EnerDel Volvo battery set is custom-made and is described as a split battery pack. With an energy content of more than 24 kWh nominal energy, Volvo plans that 22.7 kWh is used to power the car.

While the electric motor is located under the hood, one of the priorities of the Volvo project is to find the optimal placing of the battery. Most likely it will be the “prop shaft tunnel” and where the fuel tank normally is located. These locations are within the car’s optimized crumple zone in the most common collision scenarios.

Recharging the C30’s EnerDel battery pack via a household supply at 230V, 16A would take about eight hours. That’s connection comparable to what would be required for a laundry dryer or mid-sized window air conditioner.

The C30 BEV is limited to a top speed of about 130 km/h (80 mph)—more than sufficient, Volvo says, for a city car application. Acceleration from 0 to 100 km/h (62 mph) will take less than 11 seconds. The car would have a range of up to 150 kilometers (93 miles)—longer than the distance 90% of all Europe’s motorists drive per day and surely covers a wide swath of U.S. motorists as well.

So is this the beginning of the end for the gas-guzzling SUVs, suburbans and minivans, or is this just the birth of a new class of city-savvy cars? If Volvo is finally jumping on the electric bandwagon - a company that didn’t introduce its SUV until 2003, well after most drivers already owned one, it’s sure to be the true car of tomorrow.

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Transmission electron microscope micrograph of calcium phosphate nanoparticles. Credit: ACerS

What may be a new and effective alternative to insulin injections is being reported in a paper (subscription required) to published in an online edition of ACerS’ International Journal of Applied Ceramic Technology. Researchers Willi Paul and Chandra Sharma, working in India, report favorable in vitro results from tests in which insulin was bound to nanoparticles of calcium phosphate.

Diabetes sufferers are always looking for an alternative to the standard multiple daily needle injections for delivery of their insulin. Some have sought relief from alternatives delivery–transport systems such as insulin pump systems and transdermal patches. An inhaled form was introduced in 2007 but pulled from the market by the maker after several problems were documented.

The holy grail for insulin therapy is is to find a satisfactory oral transport system. Among the benefits of the injection systems is that dosage and timing can be controlled, and the insulin isn’t altered by injection. Thus, any replacement system will have to meet these three minimum requirements.

One particularly difficult challenge for oral delivery methods to to have the insulin be attached to a carrier without fundamentally changing the insulin. Then, the system has to move the protein through the stomach intact so that it can later be absorbed in the gut. Several companies, including Oramed, are already working to bring one such product to market. The exact mechanisms these companies are using are uncertain and are closely held proprietary technologies, but it is assumed that these probably use some type of polymer system.

Now, however, it looks like Paul and Sharma may have devised a ceramic-based competitor (I recently wrote about another ceramic system that uses nanodiamonds to deliver insulin or genetic therapeutics). The method the duo uses is to first activate the phosphate group of the CaP. They then conjugate it with lauric acid and give it a chitosan spacer. Insulin is then loaded onto this substrate. Finally, the nanoparticles are given a coating of alginate that gives each particle a pH-dependent sustained release mechanism.

A battery of tests demonstrated that these ceramic particles had excellent biocompatibility with insulin:

Lauric acid conjugated CaP nanoparticles are highly compatible with insulin and the CaP–CH–LA system can deliver insulin in a sustained manner in the physiological pH of the intestine with no degradation or conformational changes of entrapped insulin. These nanoparticles are having a size distribution with majority of the particles <100 nm and have been demonstrated to be noncytotoxic. Because it is known that fatty acid complexation can improve uptake of particles across epithelium, the lauric acid conjugated CaP nanoparticles may be used as a carrier for delivering insulin orally.

While these results are exciting, much more work needs to be done, including in vivo tests. One issue that still needs to be documented is how quickly the CaP particles break down. Degradation within 24 hours would be ideal.

Paul and Sharma’s paper can be accessed via the ACT “Early View.”

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