Give it some gas

摘要

You might think that we already burn hydrocarbons in enough places on Earth. The planet's roads are nose to tail with engines designed to turn fossil fuels into usable energy, polluting our cities with noxious gases and loading the atmosphere with global-warming carbon. The same polluting hydrocarbon fuels feed many of our power stations and heat most of our homes. Well, now there's a plan to burn hydrocarbons literally anywhere and everywhere. But before you throw up your hands in horror, listen to the reason why and see if you don't agree that it could, in fact, be rather a neat idea. The problem is that batteries are lousy power sources. For today's mobile electronic devices, the limiting factor is the battery: there's just not enough juice for a given size and weight. Lithium-ion batteries have an energy density of 1.2 megajoules per kilogram, and alkaline batteries are only half as good. But your average liquefied hydrocarbon, such as propane or butane, contains an astounding 45 megajoules per kilogram.