Salt and a Battery
Putting energy to work requires solution of a pair of problems: finding a source and storing the energy until we are ready to use it. Biological systems have developed elaborately multi-layered solutions. Mostly our source is the Sun. The invention of photosynthesis was the big breakthrough, taking energy from the Sun and storing it in carbohydrates (which, for future reference, pack about 17 MJ of energy per kilogram of weight). Other systems facilitate short term storage (ATP) and long term (fat). Some of that energy of photosynthesis was tucked away in the decaying organic matter that became the fossil fuels that tens of millions of years later are our primary source of energy. Those fossil fuels, in various refined forms, are admirably suited to be both sources of energy for us and compact, highly portable, high-energy storage media ready for use in our combustion engines. We have gotten better at extracting energy more directly from the Sun, especially in the form of elec...