The dangers of fiat money are many and well documented, but the premier historical alternative - the gold standard - has the disadvantage of using an arbitrary, inconvenient commodity of limited personal utility - gold. Gold of course has various specialized industrial uses, but it has very little immediate value to human existence - unlike such other examples as potable water, food, or heat, which are universally valuable under all circumstances.
It would be advantageous if money were backed instead by a commodity having real and immediate value - and in fact in many primitive societies, money as a distinct and standard medium of exchange evolved out of barter in the local variety of food grain. Our modern knowledge of physics, and the technology available to us out of that knowledge, gives us the opportunity to select a less arbitrary standard medium of exchange - energy. After all, energy is the currency in which the universe does its accounting. It is a natural choice for many reasons, and it restores the utility advantage of barter exchange, without compromising the universality of paper money. Last but not least, it would encourage green practices and widespread adoption of technologies like solar and geothermal power for personal use, as energy inefficiency would literally become 'throwing money away' - a fact that today's system somewhat disguises.