Sunday, November 23, 2008

How Fuel Cells Work

The core of the Ballard® fuel cell consists of a membrane electrode assembly, which is placed between two flow-field plates.

The MEA consists of two electrodes, the anode and the cathode, which are each coated on one side with a thin catalyst layer and separated by a proton exchange membrane (PEM). The flow-field plates direct hydrogen to the anode and oxygen (from air) to the cathode.

When hydrogen reaches the catalyst layer, it separates into protons (hydrogen ions) and electrons.

The free electrons, produced at the anode, are conducted in the form of a usable electric current through the external circuit. At the cathode, oxygen from the air, electrons from the external circuit and protons combine to form water and heat.

Parts of a Ballard® fuel cell

Diagram of Fuel Cells

Expanded Single Fuel Cell
A single fuel cell consists of the membrane electrode assembly and two flow-field plates.

Hydrogen flows through channels in flow field plates to the anode where the platinum catalyst promotes its separation into protons and electrons. Hydrogen can be supplied to a fuel cell directly or may be obtained from natural gas, methanol or petroleum using a fuel processor, which converts the hydrocarbons into hydrogen and carbon dioxide through a catalytic chemical reaction.

Membrane Electrode Assembly
Each membrane electrode assembly consists of two electrodes (the anode and the cathode) with a very thin layer of catalyst, bonded to either side of a proton exchange membrane.

Air flows through the channels in flow field plates to the cathode. The hydrogen protons that migrate through the proton exchange membrane combine with oxygen in air and electrons returning from the external circuit to form pure water and heat. The air stream also removes the water created as a by-product of the electrochemical process.

Flow Field Plates
Gases (hydrogen and air) are supplied to the electrodes of the membrane electrode assembly through channels formed in flow field plates.

Fuel Cell Stack
To obtain the desired amount of electrical power, individual fuel cells are combined to form a fuel cell stack. Increasing the number of cells in a stack increases the voltage, while increasing the surface area of the cells increases the current.

Learn more

What is a Fuel Cell?

A fuel cell is an electrochemical energy conversion device that converts hydrogen and oxygen into electricity and heat. It is very much like a battery that can be recharged while you are drawing power from it. Instead of recharging using electricity, however, a fuel cell uses hydrogen and oxygen.

Photo courtesy Ballard Power Systems
A fuel-cell stack that could power an automobile
The fuel cell will compete with many other types of energy conversion devices, including the gas turbine in your city's power plant, the gasoline engine in your car and the battery in your laptop. Combustion engines like the turbine and the gasoline engine burn fuels and use the pressure created by the expansion of the gases to do mechanical work. Batteries store electrical energy by converting it into chemical energy, which can be converted back into electrical energy when needed.

A fuel cell provides a DC (direct current) voltage that can be used to power motors, lights or any number of electrical appliances. There are several different types of fuel cells, each using a different chemistry. Fuel cells are usually classified by the type of electrolyte they use. Some types of fuel cells show promise for use in power generation plants. Others may be useful for small portable applications or for powering cars.

The proton exchange membrane fuel cell (PEMFC) is one of the most promising technologies. This is the type of fuel cell that will end up powering cars, buses and maybe even your house.

Monday, July 14, 2008

Cell Phones and Cancer: No Clear Connection . . .

Of the 100 million American cellular phone subscribers, some use their wireless phone only in a crisis—to call a friend or 911. They put their rap sessions on hold until arriving home, where phoning a friend costs no cents per minute.

For other wireless phone owners, it could be the fear of brain cancer, not an unwieldy wireless bill, that keeps them from using their cell phones for leisure chats.

Convinced that a nine-year cell phone habit led to his brain cancer, neurologist Chris Newman, M.D., has filed an $800 million lawsuit in Baltimore against his cell phone's maker and several other telecommunications companies. His suit comes five years after the dismissal, for lack of evidence, of a lawsuit filed in Florida by David Reynard, who alleged that a cell phone was responsible for his wife's fatal brain cancer.

In Newman's case, his lawyer has said, "it's really not a question at all" whether the cancer is cell phone-related. The evidence, she says: Newman's own doctors made the connection between his long-time cell phone use and his tumor, which is positioned in "the exact anatomical location where the radiation from the cell phone emitted into his skull."

Newman has been front and center in a renewed public focus over the last few months on whether the fear of brain cancer from wireless phones is well-founded or folly. For his part, epidemiologist Sam Milham, M.D., recently expressed a breakaway scientific viewpoint when he told the television audience of CNN's Larry King Live show that there is "plenty of reason for concern" about cell phones causing brain cancer.

Hold the phone. Is there really cause for concern? Do steps need to be taken, as Milham told Larry King, to avoid a brain cancer epidemic among the millions of cell phone users in this country and around the world?

No, current scientific evidence does not show any negative health effects from the low levels of electromagnetic energy emitted by mobile phones, says the Food and Drug Administration. But some recent studies suggest a possible link between mobile phones and cancer and warrant follow-up, the agency says, to determine with more certainty whether cell phones are safe.

"We don't see a risk looking at currently available data," says David Feigal, M.D., director of the FDA's Center for Devices and Radiological Health. "But we need more definite answers about the biological effects of cell phone radiation, and about the more complicated question of whether mobile phones might cause even a small increase in the risk of developing cancer."

Tuesday, July 8, 2008

Your Baby's Senses

Find out about your baby's five senses at birth and beyond.

Your newborn navigates the world using his five senses. Baby's sensory explorations are constant, whether he's mesmerized by Daddy's face (or his brightly patterned tie) or soothed by the sound of his favorite lullaby or the smell of Mommy's skin. Keep things interesting by exposing baby to lots of new sensations — tickle him with a feather or play your favorite CD. The possibilities are endless when there's a whole world to discover.

1. Touch

Your baby thrives on being held and cuddled. And your touch has an amazing power to communicate love, as well as soothe him and even boost his immunity. Research shows that babies who are stroked lovingly don't get sick as much and cry less often. And preemies who are massaged grow and develop faster than babies who aren't. It's natural for your newborn to prefer soft touches, like a gentle caress or the feel of soft cotton. You'll notice that baby bristles at a rough touch or a scratchy, coarse fabric.

2. Taste

Baby's palate starts to develop in the womb. Different flavors from Mom's diet are transmitted to baby through the amniotic fluid, and then through breast milk once he's born. Recent studies show that the foods baby was exposed to during pregnancy or nursing are the ones he tends to like. So if you love carrots, don't be surprised if your little one shares your opinion. But no matter what you ate during pregnancy, baby is born with a sweet tooth. He'll love that first bite of sweet pureed banana or applesauce.

3. Hearing

Baby's hearing is well developed at birth, but he prefers high-pitched voices, like Mom's, because he hears them best. That's why the baby talk most people use is also music to his ears. Over the first year your child's hearing will sharpen and he'll learn to track sounds. For the first three months, he'll only turn toward a sound that's in front of him, but by 6 to 12 months he'll look toward a noise coming from behind him or from across the room.

4. Smell

Baby's little nose is in full working order at birth. He knows your scent well from the time he spent in the womb, and studies show that newborns can tell the difference between their mother's breast pads and those of another nursing mom by scent. Babies are born preferring sweet smells like the fragrance of vanilla; lemon is also a favorite. And your newborn naturally dislikes foul odors, like the smell of rotten eggs. He also hates bitter or sour tastes — probably an instinct to help him avoid dangerous foods.

5. Sight

At first, a baby's eyes don't work together, and studies suggest that he sees two of everything. He focuses best on objects 8 to 12 inches in front of him (images closer or farther away are blurry). That's about the distance to your face when you're feeding him, so it's no wonder that he loves looking at you.

Newborns prefer the human face in general. They're especially drawn to the outline of the face or the hairline, which is easy to see because of the contrast. Newborns can distinguish light from dark but can't quite see color until about 4 months. Try getting baby's attention with high-contrast patterns (like a checkerboard or stripes) and black-and-white or boldly colored toys. At 4 months he'll begin to use his eyes to coordinate his hand movements, making reaching and grabbing easier.

Monday, July 7, 2008

What Is an Optimal Diet?

Ques: With all the contradictory dietary information on the market, what do you feel is an "optimal" diet?

DR. SHIKE: The best diet for health maintenance, and for the prevention of avoidable diseases, should include a wide variety of foods from the four food groups. Such a diet should conform to the best knowledge we have based on good science and not on clever marketing. A healthy diet should both induce weight loss in the obese, and help all individuals prevent nutrition-related diseases such as heart disease, diabetes, cancer, and others.

In terms of actual food composition, an optimal daily diet would include an appropriate amount of calories. These caloric sources should include 20 percent fat, 20 percent protein, and 60 percent carbohydrates.

A healthy diet should routinely include at least nine servings daily of fruits and vegetables, and should contain both soluble and insoluble fiber.

Ques: That seems to be the diet many people try to follow.

DR. SHIKE: Yes, but only a few succeed in shedding excess weight. A critical and often overlooked part of designing a good diet is determining the daily calorie intake that each person requires. It is definitely not a "one size fits all" approach.

Ques: Would optimal calorie requirements be calculated by height and weight, or by some other measure?

DR. SHIKE: The number of calories required each day is determined principally by body size, by level of daily physical activity and body weight goals. Diets are developed by determining how many calories a person typically needs to have enough energy to complete routine tasks: living, working and playing.

People who have jobs requiring low or moderate physical activity, and who have an average-sized body, should consume somewhere in the neighborhood of 1,800 calories a day.

In terms of the 20-20-60 recommendation, someone striving for optimal daily calorie intake would consume 40 grams (360 calories) of fat, 90 grams (360 calories) of protein, and 270 grams (1,080 calories) of carbohydrates. That's an approximation, of course. But it would be enough to provide energy and maintain current weight in a person with low to moderate physical activity.

On the other hand, someone who performs strenuous physical activity on a daily basis would need more calories to maintain present weight.

Ques: What is the best way to accurately determine daily calorie requirements? Is this a do-it-yourself project?

DR. SHIKE: The first step is to consult a registered dietitian, who will evaluate your nutritional requirements based on height, weight and level of daily physical activity.

Typically, an interview will include a full nutritional and health history, height and weight and determination of Body Mass Index, or BMI. This is a number arrived at by using a formula that factors in height and weight. The number derived indicates whether the person is overweight or not. From this, calorie requirements are calculated, and a diet is designed with an appropriate mixture of fat, protein and carbohydrates.

Wednesday, July 2, 2008

Overview of Bluetooth

Bluetooth is a protocol specification for wireless connectivity in a home-like environment.
Bluetooth range is limited to few meters and requires low power management.
It is a big step towards an era of smart rooms and appliances which think and care about themselves and you.
Each Bluetooth device is equipped with a microchip transceiver that transmits and receives in a previously unused frequency band of 2.45 GHz that is available globally (with some variation of bandwidth in different countries).
In addition to data, up to three voice channels are available.
Each device has a unique 48-bit address from the IEEE 802 standard.
Connections can be point-to-point or multipoint.
The maximum range is 10 meters.
Data can be exchanged at a rate of 1 megabit per second (up to 2 Mbps in the second generation of the technology).
A frequency hop scheme allows devices to communicate even in areas with a great deal of electromagnetic interference.
Built-in encryption and verification is provided.

What is Bluetooth ?

Bluetooth is a computing and telecommunications industry specification that describes how mobile phones, computers, and personal digital assistants (PDAs) can easily interconnect with each other and with home and business phones and computers using a short-range wireless connection. Using this technology, users of cellular phones, pagers, and personal digital assistants such as the PalmPilot will be able to buy a three-in-one phone that can double as a portable phone at home or in the office, get quickly synchronized with information in a desktop or notebook computer, initiate the sending or receiving of a fax, initiate a print-out, and, in general, have all mobile and fixed computer devices be totally coordinated. The technology requires that a low-cost transceiver chip be included in each device. Products with Bluetooth technology are expected to appear in large numbers beginning in 2000.