Abstract
For at least a century, innovators have looked on wind, waves, tides, warm ocean waters, marine organisms and the salt in the sea as potential sources of energy. More recently, even use of heat from marine vulcanism has been suggested. Although there have been any number of creative technologies invented to exploit these resources and numerous trials, these sources have only provided a miniscule amount of energy. Much of the reason for this has been the relatively low cost of competing forms of energy, especially fossil fuels. Concerns about carbon dioxide and global warming and the security and long term availability of fossil fuel supplies has led to greatly renewed interest in all forms of renewable energy. The current administration has emphasized its interest in renewable energy both as a replacement for fossil fuels and as a job creation engine, and is providing vastly increased funding for all forms of renewables, so the time may have come for ocean renewable energy as well. This paper presents a basic review of the technology of each of the major sources including wave conversion, fixed and floating wind turbines, free flowing current turbines, ocean thermal energy, salinity gradient and marine biofuels, and discusses the magnitudes of each of the resources, and the particular technical issues each technology is facing. A history of some notable historic efforts is presented and specific current efforts are discussed. However, many of the key issues of ocean renewable energy do not involve the technology of the conversion devices, but how ocean renewable energy sources relate to the overall system of energy, the environment, public policy and the practical and business issues of introducing such radical new systems into the existing energy and marine industries.