Marine energy efforts are increasingly focused on remote locations where traditional grid-tied systems are not practical. Seals and bearings in marine energy generators are a common source of failures, accounting for up to a 25\% failure rate per year. Polycrystalline diamond (PCD) bearings are composed of one of the most durable substances known to humankind and have been successfully tested in laboratory conditions for marine use. PCD bearings can be used to construct flooded marine energy generators that do not have seals while providing virtually indestructible bearings to reduce maintenance while increasing reliability for marine energy systems. PNNL built a bearing test stand to mimic conditions found in the cross-flow turbines being built by researchers at the Applied Physics Laboratory at University of Washington. We exposed steel and PCD bearings in the bearing test stand to Arctic water temperatures (-2.4°C), fostering ice formation around bearing surfaces while monitoring bearing health for \~1,000 hours. While the steel bearings failed at the 990 hour mark, the PCD bearing show virtually no signs of wear beyond characteristic self-polishing of bearing surfaces. The PCD bearings did not change weight appreciably and while ice formation impacted bearings function while present, the coefficient of friction (CoF) of the bearings was approximately .05 without ice, making these bearings 95\% efficient. PCD bearings present an opportunity for rugged marine power generation in flooded marine energy generators.
