|SCIENCE TRIBUNE||Thursday, February 20, 2003, Chandigarh, India|
One big advantage of the futuristic hydrogen-burning car is that it produces little pollution. There are no carbon dioxide emissions. In fact, the only by-product from the chemical reaction is water.
UNDERSTANDING THE UNIVERSE
Hydrogen as future
fuel for cars
One big advantage of the futuristic hydrogen-burning car is that it produces little pollution. There are no carbon dioxide emissions. In fact, the only by-product from the chemical reaction is water. There are some oxides of nitrogen that are produced from the nitrogen in the air, as well as minimal hydrocarbon emissions that emanate from the traces of lubricants present in the combustion chambers of the engine. The second way to fuel a car with hydrogen involves using hydrogen in a fuel cell to produce the electricity for an electric powered car. A fuel cell produces electricity from a chemical reaction like a battery, but will continue to produce as long as its reactants — hydrogen and carbon — are delivered to it.
During the last couple of years, General Motors, Daimler- Chrysler, Mercedes-Benz, Ford, Honda, Mazda, Nissan, Renault, Toyota, and Volkswagen have considerably invested in research related to hydrogen fuel-cell technology. Ford Motor Company and Daimlerchyrsler have plans to produce small numbers of these cars by the year 2004. A hydrogen-powered car made by General Motors was on display at the Sydney Olympics. General Motors claims that it is the first hydrogen fuelled electric car to prove itself on the road. The HydroGen 1 accelerates from zero to 60 mph in 16 seconds and has a top speed of about 84 mph and a range of 240 miles on a tank of fuel. General Motors predicts that by the end of the decade, 10% of new cars will run on combinations of fuel cell technology and hydrogen. They predict that by 2025, that figure could rise to 25% of the world market.
Germany’s BMW presented what they referred to as the world’s first production-based hydrogen car in May, 2000, the BMW 750hl. The company claims that they will be the first vehicle makers in the world to offer series production of hydrogen cars. They plan to open hydrogen fuel stations throughout Europe by the year 2010. By that time they expect to sell several thousand hydrogen-powered cars priced competitively with similar conventional cars. The BMW hl uses a 12-cylinder engine delivering 204 horsepower. It can accelerate from zero to 60 mph in 9.6 seconds with a top speed of 135 mph. Fitted with something called the 140-Ltre Cryo" fuel tank, the range of the car is just over 200 miles. In the Cryo tank, hydrogen is stored cryogenically, as a liquid, at a temperature of 250 degrees below zero Celsius. The double-walled tank is located behind the rear seat-backs. Two safety valves are in place to control the ventilation in the event of excessive pressure buildup.
Mercedes-Benz has also jumped into the fray. The company wants to have vehicles powered by fuel cells in the market in five years time. At present, a number of technical hurdles remain. Prototype cars are being tested, but along with technical challenges come problems with infrastructure. There are no hydrogen filling stations anywhere in the world and the fuel of the future cannot be carried through pipelines as is the case with petroleum products. Hydrogen will require an entire new fuel distribution infrastructure.
Let us compare some of the properties of hydrogen to that of petrol. In terms of energy content, it only takes about 9.5 kg of hydrogen to produce as much energy as 25 kg of petrol. But because of the low density of hydrogen, storing 9.5 kg of hydrogen requires a 55-kg tank, whereas storing 25 kg of petrol only requires a 17-kg tank. Hydrogen fuel typically takes up about four times as much space as petrol to deliver the same energy content. Producing enough hydrogen fuel for the fuel cell market is another challenge faced by this emerging technology. Several environmentally, acceptable sources of power for generating the electricity required to electrolyse water into hydrogen and oxygen are still to expensive for commercial applications.
There are technical obstacles to be overcome before hydrogen cars will be seen on the roads. In addition to the problem of slow warm-up, hydrogen fuel cell cars have a short range. Honda’s V-3 has a range of 110 miles, a defect which can only be partially offset by designing a larger hydrogen tank into the car. But a bigger tank will add weight and take up more space. V-3, is one of the most advanced hydrogen fuel cell cars in the world, but it cannot run on the open road before being warmed up for at least five minutes.
People mistakenly believe that hydrogen gas will explode if it comes in contact with any flame. Hydrogen is very flammable, but in order to burn, it must come in contact with oxygen, and in order to explode it must be mixed with oxygen before being ignited.
There are serious doubts about storing hydrogen to use in a car. The present method is simply to compress it until it turns into a liquid and store it in a tank. This is very difficult, because the container must be very strong and heavy and you have to keep the hydrogen very cold — about 260 degrees below zero degree Celsius. Research is continuing to find easier ways to solve this problem.
A fuel cell car, in fact, is an electric vehicle with a battery that can be refuelled instead of recharged with its reactants i.e. hydrogen and oxygen. Fuel cells must become dramatically less expensive than they were in early 1999 at the dawn of their commercial mass-production. There is little doubt that this will occur if they are engineered for and put into mass-production. Compared to car engines. With their thousand parts made chiefly of heat-treated metal alloys and subject to the stresses of motion and explosion, fuel cells should ultimately prove cheap, rugged, and easy to make. If fuel cells are manufactured in very large volumes, using such innovative designs, they could become extremely affordable.
Since hydrogen is a non-petroleum
fuel, using it reduces the world’s dependence on the depleting
reserves of hydrocarbons. Moreover, petro products’ sky-rocketing
cost, dwindling supply and their increasing contribution to global
warming calls for developing environment friendly alternative energy
sources not only for driving vehicles but also for many other
industrial and domestic applications. Though commercial viability of
such bold strides will take some more years to fructify, the present
technological efforts have made the man of the street to understand
that there is an alternative to expensive and polluting fuel oil.
India too could have exploited its scientific and technological talent
by funding such type of challenging research to develop this viable
alternative to the fossil fuel whose very import costs the country
nearly Rs 80,000 crore annually in foreign exchange.
Engineering researchers like Dr Mark Jones and Dr Tom Martin at Virginia Tech, USA are creating the ultimate consumer fabric of the future. They are developing a new line of clothing that may make it possible to wear your computer hardware on your sleeve.
The projects aim is to develop a new line of "e-textiles". That is, clothing interwoven with electronic components that can serve as personal, wearable computers or as large sensing and communications devices.
The fabrics will be incorporated into
typical military equipment, such as tents or camouflage nets, but will
come with the added bonus of electronic wires and sensors that can
listen for the faint sounds of distant vehicles being deployed by the
UNDERSTANDING THE UNIVERSE
Why did Mir space station, put up by the Russians many years ago, fall back to the earth?
Mir did not fall down by itself. It was de-orbited. That means that by firing rockets its orbital velocity was changed. A lower centrifugal force led to the descent of the space station. As the density of the atmosphere increased so did the frictional force. The descent became faster, frictional forces tore the station apart and much of it disintegrated and burnt up like a meteor in the heat that was generated. Larger pieces that survived fell into the ocean. To a large extent it was a controlled descent, nowhere as well controlled and gentle as that of the space shuttle, but controlled nevertheless because it was necessary to avoid populated areas of the earth from a shower of debris from the skies.
Your question perhaps concerns the need to bring down this space station that had been going around the earth for so many years. A space station needs continuous maintenance. Not being at very high altitude, less than three hundred kilometers perhaps, it was still subject to frictional deceleration by the small amount of air still present at that altitude. There were the perturbations caused by the pressure of the solar wind on its body and the solar panels. It also needed to change its orientation to meet the requirements of various scientific and other functions. Then there were requirements for the sustenance of the astronauts and various supply ships going and coming. It was a small habitation most of whose requirements had to be met through transportation from the earth. The control systems and computers had become dated and needed repairs and maintenance.
It was felt by the Russians that they could not afford to go on maintaining this station and simultaneously meet their commitments for the International Space Station being set up in collaboration with the Americans, the Europeans and the Japanese. That is why the Mir station had to be laid to rest. It could not be left there because it would have come down in any case if left unattended. To allow that would have been dangerous and irresponsible.
Why does it make so much noise when I put a little bit of water in hot oil?
Hot oil is very much hotter than the
boiling point of water. When you put drops of water in hot oil, they sink in a
little (water being heavier than oil) and then convert into steam that escapes
with an explosive force. That is the reason for the noise. Of course nothing
like this happens if you pour a little oil in boiling water — for the obvious
reason that oil stays near the top and cannot be vaporised suddenly because
boiling water is not hot enough.
New way to recharge
Think of them as electricity filling stations: Two new pads from MobileWise and SplashPower remove the last tether from portable electronics: the power supply. The MobileWise version incorporates hundreds of exposed contacts; set your laptop, cellphone or PDA on it and electricity is delivered through two conductors. The SplashPad is even more seamless — it generates a magnetic field that Splashenabled devices can pick up from a centimeter away and transform into the appropriate voltage. Both technologies will show up in products late in 2003. Popular Science
Brain cells from stem cells
Stem cells from a person’s own bone marrow can be used to generate brain cells and other nervous system cells that, when put back into the body, may be a way to treat diseases like brain cancer or Alzheimer’s, researchers say.
"Neural stem cells have a lot of characteristics that make them an attractive means of treating neurological disorders — but they come from precarious sources," said Dr. John Yu, co-director of the brain tumour programme at Cedars-Sinai Medical Center in Los Angeles and the study’s senior author.
He was referring to the political and ethical issues surrounding the use of embryonic and fetal stem cells in medical research.
Using renewable stem cells culled
from bone marrow solves that dilemma — as well as potential problems
with tissue rejection and uncontrolled growth of stem cells cultivated
in a lab dish, Dr Yu said. — Reuters