What is the function of an accumulator in a hydraulic PTO system of a WEC?

In a hydraulic Power Take-Off (PTO) system of a Wave Energy Converter (WEC), the accumulator primarily functions as an energy storage device and a pressure stabilizer. Hydraulic PTO systems use hydraulic pumps and motors to convert the mechanical energy of wave motion into a high-pressure hydraulic fluid flow. This fluid is then used to drive a hydraulic motor, which in turn drives a generator to produce electricity. However, wave energy is inherently intermittent, resulting in fluctuating pressure and flow rates in the hydraulic circuit. The accumulator, which is essentially a pressure vessel containing compressed gas (typically nitrogen) and hydraulic fluid separated by a bladder or piston, stores hydraulic energy during periods of high wave activity (when the pump output exceeds the motor demand). It then releases this stored energy during periods of low wave activity (when the pump output is less than the motor demand). This process smooths out the pressure and flow variations, providing a more stable and continuous power supply to the hydraulic motor and the generator, ultimately leading to a more consistent electrical output. It also protects the hydraulic components from pressure spikes and reduces wear and tear, extending the system's lifespan.