Ocean and Geothermal Energy Systems

This paper presents techno-economic summaries of ocean wave, tidal and current, ocean thermal, and geothermal energy, including grid interface characteristics. These forms of energy represent a significant opportunity to complement diversified energy conversion portfolios. Ocean wave energy conversion relies on the capture of kinetic and potential energy in moving and elevated water in an ocean wave. Tidal and current technology converts the kinetic energy in moving water, much like a wind turbine. Ocean thermal converts the energy available in the temperature gradient of warm surface water and cold deep water. Last, geothermal conversion utilizes the hot rock and water deep within the Earth. The total global average wave resource is estimated at approximately 2000 GW, with approximately 300 GW in the United States. The total global tidal resource is estimated at approximately 1000 GW, with 50 GW in the United States. The marine current resource estimate for the Florida Current in the southeast United States is estimated at 5 GW. Ocean thermal has a global capacity estimate of 5000 GW. Last, the global conventional hydrothermal geothermal capacity estimate is approximately 200 GW, but with much more possible through enhanced geothermal systems. For cost, it was found that the long-term projected wave energy conversion cost is $0.10-0.15/kWh. The long-term projected tidal cost is found to be $0.025-0.25/kWh. Ocean thermal long-term cost is projected at $0.10-0.18/kWh. And last, geothermal, being more closely aligned with traditional thermal generation, is estimated at $0.03/kWh to $0.15/kWh.