Tuesday, October 07. 2008Better Solar for Big Buildings - Du soleil en tube
By Kevin Bullis
Solyndra, a startup based in Fremont, CA, has developed a novel type of solar panel that's cheaper to install and produces more power than conventional panels. Unlike conventional solar panels, which are made of flat solar cells, the new panels comprise rows of cylindrical solar cells made of a thin film of semiconductor material. The material is made of copper, indium, gallium, and selenium. To make the cells, the company deposits the semiconductor material on a glass tube. That's then encapsulated within another glass tube with electrical connections that resemble those on fluorescent lightbulbs. The new shape allows the system to absorb more light over the course of a day than conventional solar panels do, and therefore generate more power. What's more, arrays of these tubes offer less wind resistance than conventional flat solar panels, which makes them easier and cheaper to mount on roofs, the company says. Chris Gronet, Solyndra's CEO, says that these advantages ultimately reduce the cost of generating solar power, although he won't say by how much. The company has raised $600 million in venture funding and has orders for $1.2 billion worth of solar panels, which it sells through installers exclusively for commercial rooftops. It started shipping its products earlier this year and is now ramping up production at its factory, which will eventually produce enough solar panels every year to generate 110 megawatts of electricity. The company soon plans to start construction on a 420-megawatt-capacity factory. Solyndra is one of several companies that have recently received hundreds of millions of dollars to develop thin-film solar cells. Miguel Contreras, a senior scientist at the National Renewable Energy Laboratory, in Golden, CO, which developed the semiconductor deposition method used by Solyndra, notes that several other companies have developed solar cells based on thin films using the same combination of semiconductors; these thin films are making possible a range of new forms for solar cells, including flexible solar cells and solar roofing materials. "There's a lot more flexibility with thin films than there is with [conventional silicon] wafer technologies," Contreras says.
The cylindrical design also allows the solar panels to absorb more light. Solar panels work best when light hits them directly, such as when the sun is directly overhead. To get more power from solar panels, they're often mounted on tracking systems that keep each panel pointed at the sun all day. But these tracking systems don't work in high winds, add cost, and take up space that could be occupied by other solar panels. The cylindrical solar cells provide another way to increase the power from a solar panel. At any point in the day, some part of the curved surface is facing the sun more or less directly, and therefore absorbing a large share of that light. The trade-off, of course, is that the other side of the cylinder is shaded. With highly reflective white roofs, however, this is less of a problem. Light passes through the same spaces between the cylinders that allow wind to flow through. It reflects off the roof and is absorbed by the shaded side of the solar cells. Also, the other surfaces of the solar cell absorb some diffuse light from the sky. This adds up to greater energy production over the course of a year than a conventional system, the company says. Combined with low installation costs, this significantly lowers the cost of solar power. Gronet says that within a few years, the company plans to produce solar systems that generate electricity competitive with the average cost of electricity in the United States (about 10 cents per kilowatt-hour) by optimizing manufacturing and increasing production volumes. The company, however, does not plan to expand out of the commercial rooftop business, where its specialized design has an edge. Other solar-panel technologies may prove more affordable for other applications, such as residential installations and large-scale projects for utilities. Copyright Technology Review 2008.
Related Links:Simplified Displays - Energy efficient
By Kate Greene
In 2005, Mary Lou Jepsen joined Nicholas Negroponte, founder of MIT's Media Lab, to build a $100 laptop for each of the poorest children of the world. As CTO of the One Laptop per Child (OLPC) project, Jepsen discovered that a laptop could be many times cheaper and more power efficient if the display was made differently. Thus, she designed a liquid-crystal display (LCD) that consumes only a fraction of the power of normal displays. And to ensure that it could be manufactured cheaply, she made certain that it could be built using existing LCD manufacturing technology. Earlier this year, Jepsen cofounded Pixel Qi (pronounced "Pixel Chee"), a startup based in San Francisco that will make displays using her 48 patents on display technology. Next year, she says, displays from Pixel Qi will be on the market. Jepsen recently spoke at the Grace Hopper Celebration of Women in Computing conference in Keystone, CO, where Technology Review caught up with her.
Technology Review: Why did you leave the One Laptop per Child project? Mary Lou Jepsen: My job was done. It was my job to figure out how to develop the laptop and convince the manufacturers to work with us. I decided that, paradoxically, the best way to help OLPC was to spin out a for-profit company and help lower the cost of the components that go into the OLPC. It's economy of scale. If you make more of something, then you can make it cheaper. TR: What technology lessons did you learn from OLPC? MLJ: [That] it's a lot faster and easier to use the large manufacturing faculties of the world as your lab, rather than a small little lab where you make handcrafted things, but you have to create the relationships and the structure to do that. One of the technology lessons was to work inside the cost envelope of the developing world to lower costs overall. What's even more important and useful is dramatically lowering power consumption. Everyone wants batteries that can last 10 times longer. TR: Why haven't we seen much innovation in display technology over the years? MLJ: A lot of people get really seduced by demos of the next display technology. I myself fell under that spell for about 20 years. I worked on heads-up displays, virtual-reality technology, and holographic displays--all sorts of really cool technology. It's an emotional response to the display, and people want to have them. The truth is that over the last 50 years, only one display technology has gotten into mass production, and that's LCD. There are two others, in smaller productions--plasma and DLP [digital light processing]--but they're not in high volume. TR: Your goal at Pixel Qi is to innovate within the LCD manufacturing process. How does this give us better displays? MLJ: What became obvious to me after spending time at Intel [Jepsen was CTO of Intel's now defunct display division between 2003 and 2004] was that the silicon people did things differently from the display people. Engineers who work with silicon send their design to a fab and have a chip back in months. But engineers making displays can't just ship a new design off to a fab. So I thought, why don't we just use the manufacturing infrastructure to get the high yields like the silicon people do? That's what I did at OLPC. I went on to design a mass-producible product in six months, skipping the 20 years, millions of dollars, and missed window of opportunity that usually occurs in the display industry. We've got deals in place with 40 percent of the LCD manufacturing industry. They said no to us initially. But we proved ourselves and our designs, and now they're willing to make a bigger effort with us and our customers. TR: How are Pixel Qi displays different from typical displays? MLJ: We've got new screens based on the same ideas as the OLPC screens. Importantly, there are no manufacturing changes, and no material changes [compared with traditional LCD displays]; we're using the same manufacturing process and following the same design rules. But what you can do that's interesting when you change the design is produce sunlight-readable screens and super-color saturation. You can get really great reflective screens that rival e-paper at really amazing price points and with fantastic ultra-low-power capabilities. These displays have 1 percent of the power consumption of a regular screen by using a reflector behind the LCD grid to reflect ambient light and allowing the backlight to be turned down in bright environments. Plus, you can implement a power-management system used in OLPC [that refreshes the screen only when it changes] that saves you even more. We've done this by reinventing the display based on understanding the details of factories and how they work. All of these things work, and we are shipping them next year. TR: Which products will they be in? MLJ: We can't announce our customers or products yet, but you'll see these displays in low-power laptops. TR: How do you see display technology developing over the next two years? MLJ: I see an improvement in the readability of screens. The number-one reason why people print a page is resolution, and the number-two reason is that they don't want to stare into a flashlight. Ultimately, in a year or two, we'd like to have a lawyer's monitor or an editor's monitor--some readable screen that's just for reading. When I started meeting kids in the developing world and seeing that their schools were outside, we saw the opportunity to make screens more readable in sunlight. It's ironic that the poorest kids in the world are getting the best screen technology through OLPC, but soon the rich people in the rest of the world are going to have access to it too. TR: And beyond that? MLJ: We have a road map that goes out pretty far. I mean, we can make improvements in all sorts of screens. Take the iPhone [touch] display. It's actually two screens. One's a touch screen and one's a display screen. Why don't we use the layers in the screen itself to do touch? It solves problems of alignment and lowers cost. We are following trends and watching how they evolve, and the great thing is that we can design a screen and have something that's reliable that we can ship in about a year. We can actually do it in that kind of time frame. Copyright Technology Review 2008. Related Links:Geography, Urbanity & DemocracyBy Geoff Manaugh - [Image: The population density of the United States, ca. 2000, via Wikipedia]. Related Links:
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