I am reading The Windup Girl by Paolo Bacigalupi. In it Joules are used as currency, and they can easily be traded between such energy storage devices, which ca

I am reading The Windup Girl by Paolo Bacigalupi. In it Joules are used as currency, and they can easily be traded between such energy storage devices, which can themselves be used to power machinery. The nutritional value of food can also be so-measured.