Archive for April, 2008

What is a fuel cell?

April 9, 2008

A fuel cell converts chemicals, hydrogen and oxygen into water, and in the process, it produces electricity.

Fuel Cell Stack
Photo courtesy Ballard Power Systems
A fuel-cell stack that could power an automobile. See more fuel cell images.

An example of a fuel cell which we are all familiar with is the battery. A battery has all of its chemicals stored inside, and it converts those chemicals into electricity.

With a fuel cell, chemicals constantly flow into the cell so it never goes dead — as long as there is a flow of chemicals into the cell, the electricity flows out of the cell. Most fuel cells in use today use hydrogen and oxygen as the chemicals.

A fuel cell works by catalysis, separating the electrons and protons, forcing the electrons to travel through a device which uses hydrogen and oxygen to create electricity. A single fuel cell consists of an electrolyte, sandwiched between a porous anode and a cathode.

hydrogen powered plane (article from bbc news)

April 5, 2008

Hydrogen-powered plane takes off

The small, propeller-driven craft, developed by aviation giant Boeing, made three short flights at an airfield south of Madrid, the company said.

It was powered by hydrogen fuel cells, which produce only heat and water as exhaust products.

The tests could pave the way for a new generation of greener aircraft, the company said.

Boeing’s chief technology officer John Tracy said the flights were “a historical technological success” and “full of promises for a greener future”.

Small future

Three test flights of the two-seater aircraft took place in February and March at an airfield at Ocana, south of Madrid. The plane was modified to include a hybrid battery and fuel cell system developed by UK firm Intelligent Energy.

The fuel cells, which create electricity by combining oxygen and hydrogen, were used to power an electric motor coupled to a propeller.

Zephyr
Other organisations have demonstrated solar-powered planes

During take-off the plane’s batteries were used to provide an additional boost, but whilst in the air, the plane relied entirely on the cells.

Boeing said the plane has a flying time of 45 minutes but tests were limited to around half that time.

Although the test had been successful, the firm said it did not believe fuel cells could be the primary power source for large passenger aircraft.

However, it could be used as a secondary source of energy for large planes, according to Nieves Lapena, the engineer responsible for the test flights, but this may take some time to develop.

“In my opinion, we are talking about a delay of about twenty years,” she said.

Green skies

Hydrogen-powered planes have been flown before, but never with a human pilot onboard.

In 2005, California-based AeroVironment successfully completed test flights of its Global Observer craft which was powered by liquid hydrogen.

The hydrogen-powered plane is capable of carrying two people

Other companies are also seeking to develop more environmentally-friendly planes, amid concerns over their contribution to climate change.

Earlier this year, the airline Virgin Atlantic conducted the first commercial flight powered partly by biofuel.

And last year, defence firm Qinetiq flew a solar-powered plane for 54 hours, smashing the official world record for the longest-duration unmanned flight.

Zephyr, as the craft was known, could be used for military applications, as well as for Earth-observation and communications.

Other unmanned prototypes have been shown off by the American space agency Nasa.

However, in 2010, Swiss balloonist Bertrand Piccard plans to launch Solar Impulse, a manned plane in which he will attempt to circumnavigate the globe.

To carry the precious payload, the craft will have a huge wingspan of 80m (262ft), wider than the wings of the Airbus A380.

As the plane is piloted by only one person at a time, it will have to make frequent stopovers. The current plan is for the journey to be broken into five legs each lasting between four or five days.

(From BBC news : http://news.bbc.co.uk/2/hi/7330311.stm )

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April 5, 2008

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