1.  Woods Energy Seminar, Oct 4, Prof. Sweeney on  Energy Efficiency

2.  Oct 6:  Ethical Issues in Sustainable Building Design

3.  Volunteers may still be needed for Solar Power 2006

4.  Holmes on Global Energy Scenarios for the 21st Century, Oct 11

5.  More Efficient Solar Cells?  New LBNL semiconductor with 3 energy bands

*********************************************

Fall Quarter

Listed in CourseWork as CEE 301: The Energy Seminar

Wednesday 3:30 to 5:00, Building Room 550, Room 550A

October 4, Professor Jim Sweeney

Energy Efficiency Improvements:  Want to get involved?

(sorry for the last minute notice!  snuck up on me... gm)

****************************

On Friday, Oct 6 from 12-1pm in the Peter Wallenberg Learning Theater (on the first floor of Wallenberg Hall http://wallenberg.stanford.edu/classresources/rooms/pwlt.html), Professor John Kunz of the Civil Engineering Dept will be talking about ethical issues in sustainable building design. An abstract and speaker bio follows:

Ethical Issues in Sustainable Building Design

By Professor John Kunz

"Sustainable" building means building for economy, ecology and equity. Personal and societal ethics issues abound as we consider these "triple bottom line" goals. To build economically, ecologically and equitably, it is necessary to manage multi-discipline and ethics issues with high knowledge, sensitivity and cooperation of all building stakeholders. This talk will introduce some of the rich ethical issues concerning building in the world today and what Stanford students can do to participate effectively in the process.

*******************************

Solar Power 2006

America's Largest Solar Event

October 16-19

San Jose, CA

The organizers need volunteers to help on Sunday the 15th and are willing to provide free conference registration  contact  Michelle Brownstein at mbrownstein@seia.org if you are interested or:

Julia Judd

Executive Director

Solar Electric Power Association

805 15th St NW Ste 510

Washington, DC  20005

202-857-0898 x4

desktop fax: 480-393-5631

*************************************

 Policy and Economics Research Roundtable seminar

series is starting up next week with Holmes Hummel:

Wednesday, October 11, 12:00 - 1:00pm

Building 160, Room 318

Holmes Hummel will present dissertation research on the policy implications

of global energy scenarios for the 21st century, particularly those that

stabilize climate change via transitions in energy technology and energy

use.

More than a dozen research teams have generated hundreds of such scenarios

over the last decade, confounding policy analysts and scientists who seek to

gain insight by analyzing scenarios to explore uncertainty in the future.

Drawing directly on some of the most recently published scenarios, Holmes

will present techniques for interpretation that can be applied to the

results of any global energy and emissions model with sufficient energy

sector detail.

**********************************************

A semiconductor material with three energy bands uses more sunlight, by trapping low-energy photons.

By Prachi Patel-Predd, Oct 24, 2006 MIT Technology Review

Researchers at Lawrence Berkeley National Laboratory (LBNL) have created a new type of semiconductor material designed to improve the efficiency of solar cells by capturing low-energy photons.

Traditional solar cells respond only to a narrow spectrum of sunlight, making them highly inefficient. In the language of physicists, solar cells convert light with wavelengths corresponding to the energy it takes for electrons to jump from the valence band to the conduction band. Photons with lower energy pass right through the material.

The new semiconductor material can capture these low-energy photons for electricity, which could make solar cells with efficiencies of around 45 percent, compared with 25 percent for conventional cells that use a single semiconductor and 39 percent for cells with layers of mixed semiconductors.

The new semiconductors have three energy bands instead of the usual two (valence and conduction). The third band lies below the conduction band, effectively splitting the gap between the valence and conduction bands into two smaller parts. "This helps low-energy photons to participate in the process because they can excite [electrons] to the [intermediate] band and then up. It's like a stepping stone," says Wladek Walukiewicz of LBNL's Materials Sciences Division, who developed the semiconductor with colleague Kin Man Yu.

The researchers found that introducing a few atoms of oxygen into a zinc-manganese-tellurium (ZnMnTe) alloy splits the compound semiconductor's conduction band into two parts. Similarly, adding nitrogen to a semiconductor such as gallium arsenide phosphide will also give a multi-band semiconductor.

LBNL has licensed the technology to RoseStreet Labs, a startup in Phoenix, AZ, which plans to commercialize solar cells made from these multi-band semiconductors. Because it's an entirely new technology, though, it's hard to say when such a solar cell will be available, Walukiewicz says.

Existing solar cells with the best efficiencies--those as high as 39 percent--convert light into electricity by using different semiconductor materials with different band gaps, which are stacked on top of each other to capture a broader spectrum of light wavelengths. But these solar cells are expensive, limiting their application to uses in satellites. A device made from a single, multi-band semiconductor would likely be cheaper and easier to make, says Walukiewicz.

Nonetheless, adding oxygen to the ZnMnTe alloy is hard, because oxygen does not mix readily with tellurium. To make the new materials, then, the researchers have developed a method that implants highly energetic oxygen atoms into the alloy using an ion beam. Then they use "a very short pulse of laser to melt the material and rapidly regrow it so that the oxygen is all trapped inside," says Yu.

Making a solar cell from gallium arsenide phosphide should be easier, the researchers say, because gallium arsenide compounds can be grown layer by layer.

To reach 40 percent efficiency, though, the semiconductor material and solar cell will have to meet some fundamental requirements of physics, says Sarah Kurtz, a senior scientist at the National Renewable Energy Laboratory in Golden, CO. For instance, efficiency goes down if the material has defects or if electrons and "holes" combine in the solar cell and create photons. But, says Kurtz, if the LBNL researchers are able to overcome these challenges, "this would represent a breakthrough."