Motivation

Important

The WAPPAC Competition invites the wave energy community to collectively explore and advance passive control design. By addressing this open and practically relevant challenge, participants will contribute to advancing the field and refining the overall community understanding of the trade-offs between energy capture, operation constraints handling, and the practical implementation of passive control strategies in real-world wave energy systems.

For decades, wave energy research has primarily focused on maximizing power absorption, often through reactive control strategies [4, 5]. These controllers not only extract energy from wave-induced motion (active power) but also inject energy back into the system through the power take-off (PTO), supplying reactive power to enhance energy capture.

When the PTO is limited to absorbing power only — i.e., operating under a passivity constraint — the control strategy is considered passive. While reactive control can theoretically achieve higher energy absorption, it typically does so by amplifying device motion and applying larger control forces [5, 7]. In practice, such demands may increase mechanical wear and maintenance requirements. Moreover, the need for bidirectional power flow often entails more complex hardware architectures [3] (e.g., energy storage systems or grid connections, bidirectional actuators), thereby increasing cost and potentially reducing overall reliability. Collectively, these factors can negatively affect the levelized cost of energy (LCoE) [6].

Conversely, passive control is theoretically suboptimal in terms of absorbed power but offers tangible practical advantages: it removes the need for energy storage for providing reactive power, simplifies PTO design, and generally yields milder motions and smaller control forces [2, 3]. These properties of passive control contribute to lower operational stress and cost, which may ultimately improve the LCoE despite lower theoretical power absorption.

However, all that glitters is not gold: while passive control may appear conceptually simpler, the nonlinear passivity constraint poses a significant challenge for both control design and real-time implementation [1]. Enforcing passivity typically increases the computational burden, complicating the development of efficient controllers suitable for practical deployment. Achieving high performance within these bounds, while maintaining reasonable computational cost for real-time implementation, remains an open challenge that needs innovative solutions from the community.