Conventional wisdom is that if you want to generate enough power for a city, you need a big power station. Cities do not generally rely on banks of internal combustion engines to keep the lights on. The reason? You can throw a lot of technology at a single power source to maximise the economies of scale in a way that is not viable for lots of small engines.
So it may come as a surprise that a modern diesel engine is more efficient than a traditional coal-fired power station. The British government’s figures say 38 per cent of the energy put into a coal-fired power station comes out as useful work, whereas a good modern diesel engine is about 40 per cent efficient (at least when running steadily at its optimum speed). The latest Mercedes-Benz 2.2-litre diesel hits 42 per cent. Even the website of the Energy Saving Trust advocates the domestic use of Stirling engines and diesels to generate energy rather than relying on conventional utilities.
That throws new light on the whole electric vehicle debate. Burning coal (as some British power stations still do), turning it into electricity, sending it through the grid and then recharging a battery seems a rather complex solution when burning diesel fuel directly in the car will give almost the same efficiency.
via Why your car’s diesel engine is more efficient than a power station | Autocar.