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Column: The wondrous world of science

April 09, 2011

Extinguishing fires—with electricity

Electricity is normally associated with causing fires through short circuiting. However, George Whitesides and co-workers at Harvard University, US, are using electricity to extinguish fires. While the ability of electricity to extinguish flames has been known for a long time, the science behind it was not well understood. It is now thought that the electricity beams cause the soot particles in the flames to become charged, thereby destabilising the flames and resulting in the fire to be extinguished.

If beams of electricity are fired at flames, the flames quickly go out, as if water had been sprayed on them. A 600 watt amplifier connected to a wand is used to deliver the electrical beams. On the basis of the work carried out, backpacks are being developed for firemen who could be shooting electricity beams at the fires of the future.

Similarly, buildings can be fitted with electricity amplifiers on roofs, instead of water sprinklers, to put out fires. Such a system could save huge amounts of water wasted in extinguishing fires and avoid damage to buildings and contents caused by the massive amounts of water.

Jets fly—on biofuels

Biofuels are fuels that can be produced by micro-organisms or they may be derived from organic or food waste products. The can be in the form of solid biomass, liquid biofuels or biogases. Since the materials from which they are produced are usually derived through photosynthetic processes, they can be regarded as a solar energy source.

On Friday, March 18, 2011, there was an exciting development in the field of aviation. An F-22 Raptor fighter jet aircraft flew using a 1:1 blend of conventional jet fuel and biofuel derived from a plant of the mustard family, Camelina sativa, or simply known as ‘camelina’. The fighter aircraft flew at speeds 50 per cent greater than the speed of sound (Mach 1.5) and successfully concluded the test.

Passenger airlines such as KLM and Japan Airlines have already used blends of the biofuel derived from camelina in their aircraft, but this was the first time that this was successfully used in the sophisticated F-22 fighter jet aircraft. Camelina is widely grown in USA, usually as a rotation crop with wheat. Biofuel derived from camelina is competitive in price (about $ 70 per barrel) as compared to conventional fuels (above $100 per barrel).

Artificial leaves

Leaves, along with certain algae and many species of bacteria, are able to carry out photosynthesis. The process of photosynthesis involves the conversion of carbon dioxide present in the atmosphere into organic compounds such as sugars by using the energy from sunlight.

Oxygen is released as a by-product of the reaction. This maintains the level of oxygen in the atmosphere, removes carbon dioxide from it, thereby reducing global warming, and provides food so necessary for our survival. The annual rate of energy captured by the process of photosynthesis is about 100 terawatts—which is about six times the annual power consumption on our planet.

Scientists have been trying to develop ‘artificial leaves’ for many years—devices that could use sunlight to split water into its elements, hydrogen and oxygen. The hydrogen thus produced can then be stored in fuel cells and used for energy production.

Nocera, Professor of Chemistry at MIT, US, and co-workers have now developed a material which is thinner than a leaf and contains a couple of cheap catalysts that do the trick—nickel borate along with a cobalt compound on a silicon electronic system. When this leaf is placed on a gallon of water under sunlight, and connected to a fuel cell, it can supply enough electricity for a day for a small household in a developing country. The material is claimed to produce 10 times more energy than a natural leaf.

Biofuels from sunlight and greenhouse gases

Normally burning of petroleum and other fossil fuels leads to the production of green house gases such as carbon dioxide. This is a major cause of global warming. Can we do the reverse, i.e., use carbon dioxide to produce biofuels? Removal of carbon dioxide in this manner would be good for our environment. This can be achieved by growing of crops that produce biofuels.

Now, however, Prof Larry Wackett and co-workers at the University of Minnesota have found that this can be achieved using two bacteria. The first bacterium (Synechococcus) converts carbon dioxide to sugars using sunlight. These sugars are then converted by a second bacterium (Shewanella) to certain compounds that can be used as fuels. The product has been named as ‘renewable petroleum’.