Showing posts with label Solar Thermal Power May Make Sun-Powered Grid a Reality. Show all posts
Showing posts with label Solar Thermal Power May Make Sun-Powered Grid a Reality. Show all posts

Thursday, February 26, 2009

Surviving Crashes: How Airlines Prepare for the Worst

We tend to think of airplane crashes as fatal events. So when survivors emerge from the carcass of a crumpled jumbo jet, as they did outside Amsterdam's Schiphol Airport on Wednesday or on the Hudson River in mid-January, the spectacle is often described as "miraculous." But survival in an airplane crash is no miracle. It is the result of more prosaic interventions, from sturdier seats to more carefully placed emergency lights.



Just a day before the Turkish Airways Boeing 737-800 crash landed in light fog killing at least nine of the 134 passengers on board, a Congressional Committee in Washington heard testimony from industry experts on the ways in which various regulatory steps and changes to aircraft have greatly improved the survivability of airplane crashes. In testimony to members of the Transportation and Infrastructure Committee, Candace Kolander, the Air Safety Coordinator for the Association of Flight Attendants, a flight attendant union that has long pushed for improvements to on-board safety, listed three main successes that are proving to save lives. (Read "How to Survive a Plane Crash.")

Sturdier Seats
In 1987, Congress' Airport and Airway Safety Act called for regulators to improve what is called the "crash worthiness standard" of seats — in effect, the likelihood that they will crumple and crush passengers at impact. It took 17 years to accomplish the task, as the Federal Aviation Administration tussled with aircraft manufacturers and airlines who balked at the price. The FAA produced evidence that sturdier seats could have prevented 45 fatalities between 1984 and 1998. A deal was reached. In 2005, the FAA mandated that all U.S. aircraft built after October 2009 meet the "16g rule" — seats must be built to withstand crash forces equivalent to 16 times the force of gravity (older seats were 9g compliant). Ironically, the long negotiation period and concerns among the airlines that the FAA would make requirements retroactive means that almost all major airlines in operation today already have 16g compatible seats. (See pictures of the plane in the Hudson River.)

Fire Retardant
On February 1, 1991, USAir Flight 1493 crashed into another aircraft while landing at Los Angeles International Airport. After surviving the impact, 20 passengers and two crew died as a result of smoke inhalation as they waited to leave at the overwing exit. During the 1980s, the FAA instituted various measures that demanded aircrafts upgrade the flammability standards of materials on board — The USAir aircraft was built before the effective date of these requirements, and had not yet been modernized. All aircraft in the U.S. are now compliant. The requirements were strengthened in 1991, when the FAA required all large transport planes to carry smoke detectors in lavatories, an automatic fire extinguisher in trash receptacles, and more fire extinguishers throughout the cabin. (See pictures from the Buffalo plane crash.)

Emergency Exits
Getting to an emergency exit as quickly and as safely as possible is a key factor in surviving an airplane crash. Passengers tend to take the glowing pellets that line the cabin floors for granted, but until 1984, emergency lighting systems were typically from overhead lights: not much help in smoke, or in the frenzied panic in which passengers tend to keep their heads down. In 1990, the FAA took another step by requiring passengers sitting in emergency exit seats to be willing and able to perform safety functions.

These three fixes have saved lives. In her testimony to the Congressional subcommittee, Kolander argued that airlines and aircraft manufacturers have traditionally had a safety culture more attuned to preventing airplane crashes. But just as important, she argued, airlines should also prepare to mitigate the dangers when the worse happens. A step such as improving the sturdiness of seats, she concluded, "is an essential element of preparation for the crash that can result when accident prevention fails."

Read "How to Escape Down an Airplane Slide."

Tuesday, October 28, 2008

Solar Thermal Power May Make Sun-Powered Grid a Reality

It's solar's new dawn. For five decades solar technologies have delivered more promises than power. Now, new Breakthrough Award–winning innovations are exiting the lab and plugging into the grid—turning sunlight into serious energy.

By Alex Hutchinson


Solar Stirling Engine: Each Stirling Energy SunCatcher dish can produce 60,000 kilowatt-hours of electricity a year—enough to power a dozen U.S. homes. (Photograph by Jamey Stillings)

Planted in the New Mexico desert near Albuquerque, the six solar dish engines of the Solar Thermal Test Facility at Sandia National Laboratories look a bit like giant, highly reflective satellite dishes. Each one is a mosaic of 82 mirrors that fit together to form a 38-ft-wide parabola. The mirrors’ precise curvature focuses light onto a 7-in. area. At its most intense spot, the heat is equivalent to a blistering 13,000 suns, producing a flux 13 times greater than the space shuttle experiences during re-entry. “That’ll melt almost anything known to man,” says Sandia engineer Chuck Andraka. “It’s incredibly hot.”

The heat is used to run a Stirling engine, an elegant 192-year-old technology that creates mechanical energy from an external heat source, as opposed to the internal fuel combustion that powers most auto­mobile engines. Hydrogen gas in a Stirling engine’s four 95 cc cylinders expands and contracts as it is heated and cooled, driving pistons to turn a small electric generator. The configuration of the dish and engine represent the fruit of more than a decade of steady improvements, developed in collaboration with Arizona-based Stirling Energy Systems.

On a crisp morning this past January, Andraka and his colleagues fired up Dish No. 3. The temperature was around freezing, and the sky was 8 percent brighter than average—the contrast between the cold air and the hot sun helps the engine run more efficiently. When power began to flow from the 25-kilowatt system, it did so with the highest conversion efficiency ever recorded in a commercial solar device: 31.25 percent of the energy shining onto the giant dish flowed into the grid.

To Bruce Osborn, president and CEO of Stirling Energy, this merely confirmed something that he already knew: The system, which his company calls the SunCatcher, was ready to exit the laboratory. “The rocket science is already done,” he says. The challenge remaining is to turn the prototypes into a low-cost, mass-producible design—“just a question of good, old-fashioned engineering,” according to Osborn. To that end, Stirling Energy signed the two largest solar energy contracts in history with two Southern California utilities, promising to build up to 70,000 SunCatchers and provide power for a million homes. Construction starts next year.

Big promises from solar power companies are nothing new. “It is stern work to thrust your hand into the sun and pull out a spark of immortal flame to warm the hearts of men,” an AT&T publicity film crowed after the invention of the silicon photovoltaic (PV) cell in 1954. “Yet in this modern age, men have at last harnessed the sun.”

Well, sort of. The Bell Solar Battery, as it was called, had some successes—powering the first communications satellite, in 1962, for instance—but hopes of cheap, plentiful energy have remained elusive.

PV cells and concentrating solar thermal (CST), the two basic methods for harnessing the sun’s power, have made great strides since those early days. But inflation in the cost of raw materials, such as silicon, combined with decades of cheap fossil fuels has kept overall solar energy consumption in the U.S. at 0.08 percent. And a series of new technologies that looked promising in the lab have proved impractical on the open market, leaving many observers to conclude that the age of solar energy will always remain just around the corner.

Meanwhile, though, almost under the radar, a few solar technologies have reached maturity. A type of silicon-free solar panel, half as expensive as silicon cells, has rapidly turned Arizona-based First Solar into the biggest solar-panel maker in the country. And along with Stirling Energy’s SunCatcher, new CST designs promise to provide a steady flow of solar electricity—even at night.


Solar Thermal

How It Works: Solar Stirling Engine(Illustration by Dogo)
Big power utilities love CST for two reasons, says Reese Tisdale, a senior analyst at Emerging Energy Research, based in Cambridge, Mass. “It’s large-scale and it’s [usually] steam-powered, so it’s not so different from the gas- and coal-fired plants they’re familiar with.” The idea is not new—in fact, nine CST plants with a combined capacity of 354 megawatts have been operating in the Mojave Desert since their construction between 1984 and 1991, powering the homes of 500,000 Californians and proving the design’s reliability. (An average coal plant produces about 670 Mw.) The plants use a “parabolic trough” design, with more than 900,000 mirrors, shaped like a skateboarder’s half-pipe in vast arrays over 1500 acres of desert. The mirrors adjust to track the sun across the sky, reflecting and concentrating its rays onto liquid-filled pipes. The hot liquid, in this case oil, then boils water, which produces steam to spin a turbine.

Progress on CST plants ground to a halt after natural gas prices plummeted in the 1990s. It wasn’t until last year that the next major plant in the United States opened: a 64-Mw parabolic trough system in Boulder City, Nev., called Nevada Solar One, built by the Spanish company Acciona. Now there are 13 other plants, totaling 5100 Mw, in advanced planning stages in ­Flor­ida, Arizona and California; most will use parabolic troughs. Stirling Energy pursued a different kind of system, one that offers more flexibility and better efficiency.

Bruce Osborn started his research career at Ford Motor Co., and the key advantage of his solar dish is one his former employers would understand. “Henry Ford used to say you can have your car in any color as long as it’s black,” Osborn says, “and that’s our approach, too.” The planned 900-Mw Stirling Solar Two plant near San Diego will eventually have as many as 36,000 identical dishes, and the 82 mirror panels that make up each dish come in only two shapes. That design choice causes a slight decrease in power output, in exchange for the advantages of low-cost mass production.

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