RCAM'S MARINE PUMPED HYDROELECTRIC ENERGY STORAGE (MPH) PROJECT OFFERS A PROMISING SOLUTION TO OVERCOME SOME OF THE LIMITATIONS OF TRADITIONAL PUMPED STORAGE HYDROPOWER (PSH). BY LEVERAGING THE OCEAN NEAR POPULOUS REGIONS, MPH COULD POTENTIALLY DOUBLE AND ACCELERATE PSH DEVELOPMENT IN THE US. THE PROJECT AIMS TO ADVANCE THE TECHNOLOGY READINESS LEVEL AND ATTRACT FUNDING FOR GRID-CONNECTED DEMONSTRATIONS, SCALING-UP, AND DEPLOYMENTS, WHICH COULD GREATLY BENEFIT GRID RELIABILITY, RESILIENCY, AND RENEWABLE ENERGY INTEGRATION. THE OVERALL PROJECT GOAL IS TO ADVANCE MARINE PUMPED HYDRO (MPH) TO TRL 6 AND PREPARE FOR A FULLY OPERATIONAL GRID-CONNECTED PILOT DEMONSTRATION OF THE FIRST FULL-SCALE SYSTEM. THIS PROJECT WILL DE-RISK THE DESIGN AND 3D CONCRETE PRINTING (3DCP) MANUFACTURING AND PUMP-AS-TURBINE (PAT) UNIT INTEGRATION AND ACHIEVE TRL 6 VIA SUBSEA TESTING OF A HIGH-FIDELITY MPH PROTOTYPE FEATURING A PLATFORM/UNIT OF ONE OR MORE STORAGE SPHERES WITH A TOTAL INTERNAL VOLUME OF 20 M3. THE PROTOTYPE NOMINALLY CONSISTS OF TWO COUPLED SPHERES OF UP TO 6 M DIAMETER. THE PROJECT OBJECTIVES FOR EACH BUDGET PERIOD ARE: BUDGET PERIOD 1 1. COMPLETE DESIGN AND SPECIFICATIONS OF MPH PROTOTYPE FOR = 500 M DEEP SUBSEA TESTING. 2. DEVELOP A FEASIBLE APPROACH TO CONSTRUCT THE MPH PROTOTYPE USING 3DCP. 3. DEMONSTRATE MECHANICAL PERFORMANCE AND MARINE DURABILITY OF 3DCP MATERIALS. 4. PREPARE A FEASIBLE COSTED SUBSEA TESTING PLAN AND SECURE PERMISSIONS FOR TRL 6 SUBSEA TESTING OF MPH PROTOTYPE IN BP2. 5. DEVELOP MEASUREMENT AND VERIFICATION (M & V) PLAN FOR SUBSEA TESTING IN BP2. BUDGET PERIOD 2 6. FABRICATE MPH PROTOTYPE STRUCTURE USING 3D CONCRETE PRINTING SYSTEM. 7. PERFORM QA/QC TO VERIFY PROTOTYPE STRUCTURE MEETS DESIGN SPECIFICATIONS. 8. COMPLETE SUBSEA TESTING AT = 500 M WATER DEPTH FOR AT LEAST 5 DAYS PER TESTING PLAN. 9. ACQUIRE, ANALYZE, AND VERIFY PROTOTYPE PERFORMANCE DATA PER M & V PLAN. 10. PLAN AND INITIATE PERMITTING OF TRL 7 MPH PILOT DEMONSTRATION. THE EXPECTED PROJECT OUTCOMES ARE: VALIDATED DESIGN OF MPH SYSTEM INCLUDING PAT INTEGRATION, AND FEASIBLE 3DCP PROCESS, MATERIALS, AND QA/QC METHODS FOR FABRICATION OF MPH SYSTEMS IN A PORT ENVIRONMENT. VERIFIED PERFORMANCE DATA OF = 100 KW PAT UNIT IN = 500 M DEPTH FOR AT LEAST 5 DAYS (TRL 6). DESIGN, DEVELOPMENT PLAN, AND PERMITTING DOCUMENTS FOR A TRL 7 GRID-CONNECTED PILOT. COMMUNITY AND LABOR ENGAGEMENT, AND DISSEMINATION OF PROJECT FINDINGS.