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Deepwater Windmills Of A Different Stripe


Windmills moored so far offshore that they aren't visible from land would do more than silence most "not in my backyard" critics. Gigantic deepwater turbines could also crank out much more juice than current models. But current sea-sited windmills can't go past depths of about 45 feet. In deeper water, it gets too costly to drive into the seabed the hollow "monopiles" that support today's windmills.

Using tricks borrowed from the oil biz, Massachusetts Institute of Technology professor Paul D. Sclavounos proposes joining the wind turbine to a floating base secured to the sea floor by tense metal cables. This saves on building materials. Plus, the platform and windmill can be assembled in dry dock, then towed to a mooring site, eliminating the need for specialized crane ships and costly labor used to hoist offshore windmills into place today. Sclavounos' design promises to be economically viable in waters as deep as 600 feet. At 20 miles from shore, the floating turbines would not be seen from land, and steady winds would justify the use of supersize 5-megawatt models as tall as the Washington Monument.

Today's digital cameras capture the world as millions of points of light (megapixels) and use millions of light sensors to record the amount and color of each one. Then a chip crunches the data into an image you can e-mail to friends. All that processing takes lots of power, which is why cameras eat up batteries.

Rice University electrical engineering professors Richard G. Baraniuk and Kevin F. Kelly are building a different kind of camera that relies on just one pixel. They use an array of millions of microscopic mirrors that flip randomly on and off. This digital micromirror, already found in some rear-projection TVs, sends a random combination of pixel values to a single photo sensor. For the same size image, the method produces fewer measurements than pixels and there is a smaller amount of data, so the information can be transmitted more easily. The approach is "useful for a network of cheap sensors," says Baraniuk. The work is being funded by the U.S. Defense Advanced Research Projects Agency and Texas Instruments.

This method also opens the door to cameras that can "see" in the terahertz region, part of the electromagnetic spectrum between microwaves and infrared, a place that megapixel sensors usually can't go. A terahertz camera "would be a boon for homeland security, because it can see through clothes and luggage," says Baraniuk.

September's spinach scare was linkedto farms in three California counties. But since there was no way to know where the spinach in any given bag originated, supermarkets had to trash every one. ARmark Authentication Technologies, a unit of Adhesives Research in Glen Rock, Pa., hopes to solve the problem by using digestible markers tinier than specks of dust. Each microtag, mere microns wide, can hold a pattern or up to 16 lines of text. Readable with a handheld device, the tags can be put in water and sprayed on. A head of spinach might hold up to 1,000 of the dots.

As the number of batteries recalled by PC makers heads into the millions, a team of South Korean scientists has unveiled a way to prevent them from blowing up. Scientists at the state-funded Korea Electronics & Telecommunications Research Institute (ETRI) created a programmable sensor that helps prevent overheating in lithium-ion batteries, the culprits in a number of recent battery explosions. Once the battery voltage hits a preset limit, the team's device starts to discharge electric current, reducing the chance of heat-induced swelling.

Although the ETRI team has done tests only on mobile phone batteries, the device should also work for PCs, MP3 players, and other gadgets, says Kim Hyun Tak, the team's principal researcher. Hybrid cars could benefit as well. Such vehicles currently run on nickel-metal hydride batteries, but manufacturers are likely to switch to lighter, smaller lithium-ion cells. Kim says it could take up to three years to bring the device to market.


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