The disclosure relates to a field device of a process automation system, having at least one first intrinsically safe power supply unit, which provides locally stored electrical energy in an integrated storage element for supplying power to an electronics unit for process control. To supply power to intrinsically safe field devices from locally stored electrical energy in line with demand, it is proposed that in addition, at least one additional intrinsically safe power supply unit is integrated therein, which is fed by a power generation unit providing locally renewable electrical energy.