Fuel Cells 1
At the moment, only about 12% of the humans on the planet are wealthy enough to own a motor vehicle. But these cars, trucks and buses have an environmental and health cost over and above their dollar price. For example, the 26 million vehicles in the United Kingdom generate one third of all the UK's carbon dioxide (which leads to global warming) and one third of all the UK's air pollution (which kills around 10,000 people each year).
Suppose we move to a situation where one quarter of all the people in the world owns a vehicle - the pollution would be so much worse. And that's where the fuel cell might come in.
In today's political climate it's Bad To Burn - bad to have a vehicle billowing smoke out of the exhaust pipe, bad to have forest fires, bad to burn log fires in cities, and bad to burn off garden leaves. Even so, the human race still burns around 8 billion tonnes of hydrocarbon fuels each year.
Today's car engines are like boilers, but fuel cells are like batteries. A fuel cell converts chemical energy directly into electrical energy. But while batteries can go flat and run out of energy, fuel cells will keep on delivering electricity as long as you feed them with fuel.
A fuel cell is inherently a high efficiency device - up to 40% efficient - which is much more efficient than a car engine. Internal combustion engines burn liquid fuel and turn it into a much greater volume of hot expanding gas, and then try to extract as much energy as possible out of the expanding hot gas with all sorts of complicated moving parts. A car engine is lucky to reach 30% efficiency - and this is after over a century of refinement.
Fuel cells could change how cars and trucks get their power. Fuel cells are based on hydrogen. You may have heard people talk about the "Hydrogen Economy". You might also know that hydrogen has a bit of a Public Relations problem thanks to that product of the Cold War, the Hydrogen Bomb.
Hydrogen is the most abundant element in the Universe - making up about 75% of all the mass in the Universe. But it's only the 9th most abundant element on Earth, and makes up just under 1% of the mass of our planet.
Hydrogen is an odourless, colourless and tasteless gas and is also the simplest and lightest chemical element.
It seems that Paracelsus, the 16th Century German-Swiss alchemist and doctor, may have handled hydrogen. He discovered that when he dissolved a metal in acid, it produced a gas that would burn. But in 1766, the English chemist Henry Cavendish went one step further with this gas, which was then called "inflammable air", or "phlogiston". He actually measured the amount of gas that he got from a certain amount of acid and metal, and even measured its density. In 1776, J. Waltire noticed that when he burnt hydrogen, he also made some droplets of water. It was the French chemist Antoine-Laurent Lavoisier who came up with the name "hydrogen", from the Greek, meaning "water generator". Liquid hydrogen is used as a rocket fuel, and when it burns with oxygen it produces temperatures around 2,600°C. Hydrogen was once used to fill balloons, but is now mostly used to make ammonia and methanol, to remove sulphur from petrol, and to make food products such as margarine.
Fuel cells run on hydrogen, and fuel cells go back a long way.
Sir Humphry Davy probably invented the fuel cell in 1802. His cell turned fuel directly into electricity with a carbon anode and nitric acid as the cathode.
But it's usually Sir William Robert Grove who gets the credit for his fuel cell made in 1839. Grove's cell had two platinum strips dipping into acidified water. The top part of one platinum strip was exposed to hydrogen while the other was exposed to oxygen - and it produced electricity. But it wasn't commercially viable because it generated too little electricity, and his cells had a short life.
A lot of people tinkered with fuel cells for the next 130 years, but unfortunately they were much expensive, and it was only with the money-no-object Apollo Space Program of the 1960s that they were first used. The cost per kilowatt was about $1 million.
In fact it was a problem with a fuel cell that led to the Moon landing segment of the Apollo 13 mission being cancelled. The oxygen tank that fed the fuel cell exploded. The crew abandoned the Moon landing, and with great skill and ingenuity was able to modify their mission. They looped around the Moon and returned safely to Earth by using the life-support system in the Lunar Module.
So how could these incredibly expensive fuel cells possibly find a use in your future car? That's what I'll talk about next time…
Published 07 December 2006
© 2024 Karl S. Kruszelnicki Pty Ltd
