Overview of Wave and Current Energy: Resource, Technology, and Business Issues
Authors: Bedard Roger 
Published: October 2008

Offshore wave and current energy conversion are technologies whose time has come. Following extensive technology development over the past decade, primarily in Europe, North American electricity stakeholders are now becoming interested in applications of this technology. EPRI has recently conducted techno- economic feasibility studies of wave and tidal in-stream energy at selected locations in North America. This paper summarizes the energy resource, the energy conversion technology status, and the business case at those locations. Grid interconnection and environmental and regulatory issues are also described. The primary barrier to the use of these technologies in the U.S. is regulatory in nature. We recommend and encourage the development of an effective regulatory system that fosters the application of the best electricity generation technology for the good of society.

Two of the forms of ocean energy are currents and waves. There are three forms of current energy; tidal, ocean and river. Submerged water turbine devices are being developed to extract the hydrokinetic energy from tidal, ocean and river currents. Wave energy conversion devices are being developed to extract the hydro potential and kinetic energy in the waveâ??s orbiting water particle movement.

Resource

The U.S. wave and current energy resource potential which could be credibly harnessed is about 10% of national energy demand. The U.S. wave energy potential has been studied by EPRI and found to be about 2,100 TWh/yr (the blue shaded squares in Figure 1 below). With an extraction of 15%, and typical power train efficiencies and plant availability, electricity produced is about 260 TWh/yr, which is about equivalent to the total energy generation of conventional hydro power (about 6.5% of total supply). The energy potential of tidal, ocean and river currents has not been studied by EPRI, however, a review of the literature leads us to conclude that there is a credible potential to add about another 130 TWh/yr to our supply.

Figure 1. Tidal Current and Wave Resource (available in full paper)

The advantages of ocean energy are many. First and foremost is the high power density (kw/m2 for currents and kW/m of wave crest length for wave). This high power density results in small energy conversion machines needed to capture the energy, and small machines weigh less and cost less than large machines of the same type and made from the same materials. Other benefits include:providing a new, environmentally friendly and easily assimilated grid-connected option for meeting load growth and legislated Renewable Portfolio Standard requirements,easing transmission constraints with minimal if any aesthetic concerns,reducing dependence on imported energy supplies and increasing national security,reducing the risk of future fossil fuel price volatility,reducing emissions of greenhouse gases as compared to fossil fuel-based generation, andstimulating local job creation and economic development.

A relatively minor investment today could stimulate a worldwide industry generating billions of dollars of economic output and employing thousands of people while using an abundant and clean natural resource in the not too distant future.