Power Back up

One of the reasons we grumble about the mileage our vehicles deliver is due to the kind of engines they’re fitted with — the internal combustion or IC engine. It’s notoriously inefficient and ever since they invented it scientists and engineers have worked to increase its efficiency. Yet even now the average IC engine only converts roughly 20-25 per cent of its energy input into useful power, with most of the rest expended through heat loss. Meaning, up to 75 per cent of the potential energy that’s paid for while filling up at a petrol station is wasted because a good deal of it goes right out of the exhaust. Now if there was a way to convert that waste heat into, say, electricity, even gas guzzlers could be in business. Actually there is a way. It’s a phenomenon called thermoelectricity where a temperature difference can produce electricity. If a thermoelectric device could be attached to a car’s exhaust pipe in such a way that one side of the material in contact with the pipe is hot while the side exposed to the air is cold, the temperature difference would be enough to generate electricity. This power could then be returned to the engine to create additional torque or charge batteries. The problem is, even the best presently available thermoelectric materials have the disadvantage of a low 5 per cent efficiency and concomitant high cost per unit of output. But this could change dramatically if scientists at Northwestern University in Illinois, USA, are on the right track. The researchers claim to have developed a thermoelectric material which could be used to produce a new generation of devices that can be up to 14 per cent efficient, with a longer term efficiency goal of over 20 per cent. In driving terms this could decrease fuel consumption by almost 10 per cent. More importantly, when materials like this can become available on a commercially viable basis, the use of waste heat promises to be a high-volume application field. That’s because such significant power saving is not just applicable to the automotive industry but to a variety of sources where heat is either not fully utilised as in solar energy conversion, or it’s unnecessarily dissipated as waste such as in the case of power plants, nuclear reactors and industrial chimneys.