This work presents an experimental and theoretical study of a pitching point-absorber wave energy converter (WEC) equipped with a nonlinear stiffness mechanism (NSM) based on a pre-compressed spring. The mechanism is designed to reduce the equivalent restoring stiffness and enhance the device response without external control. A 1:13 scale prototype of the Lafkenewen WEC, deployed off Lebu (Chile), was tested in regular waves within a wave tank for two configurations: with and without the NSM. The rotational response amplitude operator (RAO) was obtained from experiments and compared against a linear hydrodynamic model formulated via Newtonian mechanics and frequency domain radiation/excitation coefficients. Dry friction at the hinge was represented as an equivalent viscous damping term identified iteratively. Unlike narrow-resonance WECs, both configurations exhibited a broadband response without a sharp resonance peak in the $0.7$–$1.2$ Hz range, due to significant radiation damping and hinge friction. The NSM produced a moderate amplification of the rotational RAO (up to ∼32%) while preserving the broadband character. Theoretical predictions agreed with the measurements when dry friction was included. These results demonstrate that passive stiffness reduction via an NSM enhances wave–structure energy transfer even in systems dominated by effective damping and provides a consistent basis for future nonlinear time domain modeling and control-oriented studies.

A renewable source of energy with great potential is wave energy, and Chile offers favorable conditions for its exploitation. To convert wave energy into a usable form of energy, wave energy converters are used. In this context, the University of Bío-Bío has designed and constructed a wave energy converter called Lafkenewen. Numerous wave energy converters have been developed over time; however, their efficiency remains low due to operation away from resonance. To address this issue, a spring mechanism with regions of negative stiffness has been proposed, which can enhance power output and broaden frequency bandwidth. This work presents a mathematical model of a scaled version of the Lafkenewen converter, developed using ANSYS software, under regular wave conditions. The results indicate that the integration of the negative stiffness mechanism leads to a 280% increase in the generated power.