Marine energy, also referred to as marine renewable energy or marine and hydrokinetic energy, is energy harvested from the movement of water in the oceans or large rivers, and ocean gradients. This includes tides, currents, waves, river flows, temperature gradients and salinity gradients. Offshore wind is excluded, as the source of power is not ocean water. Most marine energy devices use rotating or moving parts to harness energy. The energy may then be used at sea, exported to land via electric power cables, or used to generate stable fuels or products such as ammonia or hydrogen that can be transported for use.
According to research from the National Renewable Energy Laboratory, there is an estimated 2,300 terawatt-hours per year of marine energy available in the U.S., which is enough energy to power 220 million homes and provide up to 57 percent of all U.S. electricity generation. The majority of this is from potential wave and tidal energy in Alaska, though each coastal state has access to marine energy resources. Ocean thermal energy conversion in the Gulf of Mexico and around tropical U.S. island territories also provides significant contribution to the total energy potential.
Numerous potential benefits exist from marine energy development. Projects can stimulate local economies and create high-paying jobs in installation and maintenance. Once installed and operational, marine energy provides a secure energy source to reduce vulnerabilities from natural disasters and oil dependence (including eliminating possible oil spills and poor air quality from burning petroleum), as well as the potential for mitigation of climate change with reduced fossil fuel consumption. Marine energy can also provide power for unique areas and applications where other renewables such as solar are not feasible, such as in the Arctic or far offshore. Furthermore, marine energy is more consistently available and predictable than many other renewable energy resources, taking advantage of cyclical and perpetual natural phenomena such as waves and tides. Additional benefits to ecosystem functions with the creation of habitat and marine reserves are also possible.