Recent Developments in Alternative Ocean Energy Systems
Authors: Jones Anthony T. 
Published: October 2008

Triggered by changes in international treaties related to contoling emissions derived from burning of fossil fuels, the development of alternative ocean energy systems has re-awaken. The first commercial-scale wave power station is delivering power to a national grid. The costs of wave power have decline dramatically over the past ten years due to research and re-design of existing systems. The focus for tidal power has shifted from estuary barrage systems toward capturing the tidalgenerated coastal currents. Several promising projects in tidal power are in the demonstation phase. Offshore wind farms are under construction and plans are in place for delivery of additional systems. As governments change policies directed toward inclusion of alternative energy systems from renewable sources, the nearshore ocean processes have tremendous potential.

Introduction

In 1992, the United Nations Framework Convention on Climate Change committed countries to take measures to reduce emissions of carbon dioxide and other greenhouse gases to their 1990 levels. Although the United States has not ratified this approach, other countries are actively engaged in developing renewable energy sources including offshore resources in their exclusive economic zone. For example, the United Kingdom has announced it's goal of achieving 10% electricity from renewables by 2010.

In the past ten years, several developments have demonstrated the potential of the ocean as a source of renewable energy. This paper highlights some of the recent developments in wave power, tidal power and offshore wind farms.

Wave Power

Development of systems to capture the motion of the surface waves has reached a milestone with the commissioning of the first commercial-scale power facility in Scotland. LIMPET is the world's first commercial wave power station. Located on the Isle of Islay in Scotland, LIMPET is delivering power to the United Kingdom national grid.

This was after their earlier attempt, OSPREY (Ocean Swell Powered Renewable Energy) was damaged in a storm shortly after beginning operation in August, 1995. Japan Marine Science and Technology Center (JAMSTEC) has invested heavily in an experimental wave platform. Dubbed the Mighty Whale, the floating 50-m long, 1,000 tonne wave-energy converter produces 110 kW. It is anchored in 40 m water depth, 130 km west of Tokyo in Gokashu Bay. JAMSTEC recently completed a two-year study of the power conversion effiency and unit energy costs. JAMSTEC has demonstrated that the wave energy cost, about $0.28/kWhr, would provide competively priced energy for remote communities, environmentally sensitive areas and offshore facilities.

The cost of wave energy has declined dramatically in the past decade due in part to new technology breakthroughs and new efficient designs. Tom Thorpe, consultant to the European Thematic Network on Wave Energy stated that the glboal contribution of wave power is over 2 Twhr/yr, if development programs of companies engaged in this activity go forward. This represents over $200 billion in palnned investment (Knott 2000).

Two technologies are dominating this group: tapering channels and heaving buoys.