Multi-Stroke Variable Displacement Oscillating Pump for Hydrokinetic Energy

Resolute Marine Energy (RME) is developing Oscillating Wave Surge Converter (OWSC) with a seawater hydraulic Power Take Off (PTO) system for wave energy harvesting to generate electricity and desalinate seawater. OWSCs are designed to operate near shore, where the surge component of wave motion dominates. OWSCs have advantages over other wave energy converters. RME's SurgeWECTM is a proprietary OWSC and PTO system used within RME’s Wave2O™ product to desalinate seawater by means of reverse osmosis (RO). RME SurgeWECTM comprises a bottom-mounted hinged flap driving a pair of fixed displacement pumps which will deliver a pressurized flow of filtered seawater to the RO desalination plant and a hydraulic motor-generator set supplying electrical power for RO plant auxiliary devices. There are two primary challenges with using fixed displacement pumps for the hydraulic PTO. First, varying wave state results in a variable flow rate being delivered by the pumps to the PTO system. Second, torque applied to the flap to optimize the power capture varies significantly with wave state. In the proposed work, RME, in collaboration with the University of Minnesota (UMN), proposes a novel, seawater compatible, oscillating pump with variable displacement. The Phase I project focused on proof-of-concept and de-risking the technology through mathematical modeling and optimization of the pump for operation in varying representative seastates. Initial design work focused on the piston seals and cam-follower interface for high-cycle life, and system modeling to demonstrate the influence of the variable pump on plant productivity. The goal of this proposed Phase II project is to design, build, test and validate a reduced-scale version of the VDLP device. Testing and evaluation will at first be conducted on discrete components and assemblies of the pump prior to development of a functional reduced-scale prototype which will be integrated within a laboratory-scale desalination system and powered using a PTO test stand to simulate ocean waves in a series of hardware-in-the-loop (HIL) dry-laboratory tests. In Phase III we will increase scale and fidelity of the pump development work leading to deployment of a pilot-scale version of this technology in open-ocean trials at a permitted site in Oregon and later for acceptance by a water utility in Cape Verde.