Energy question of the week: How much electricity could be generated from ocean currents?
Electricity has been generated from tidal power for decades. Large installations could supply entire towns and cities. However, tides are not the only forces moving water in our seas. Ocean currents also move huge amounts of water all around the globe. Is it worth exploiting this power source?
Ocean current power stations are far more than just technologically feasible: since they do not need dams, they also have substantially less impact on the environment compared with tidal power stations. "Turbines are immersed directly in these currents, in much the same way as wind turbines," explains Jochen Weilepp from Voith Siemens Hydro Power Generation and Albrecht Ruprecht, a flow mechanics expert from the University of Stuttgart. However there is a disadvantage to ocean current power stations - their energy yield is significantly lower than that of tidal power plants.
Initial experience with 'underwater windmills' has now been gained at several locations around the globe. In 2003, a turbine was installed on the seabed off Hammerfest in Norway and several small rotors have been running in the East River of New York since 2006. Since 2003, off the coast of Cornwall, a 'Seaflow' rotor has been generating up to 300 kilowatts. In 2008, this was followed by the much larger 'SeaGen' system, now delivering up to 1,200 kilowatts of power.
However, engineers are still trying to protect these systems from the effects of saltwater, connect them to the national grid on shore, and overcome the difficulties of regular maintenance. "Ocean current power stations have now reached the status achieved by wind power back in the 1980s," state Weilepp and Ruprecht. As the equipment becomes more rugged, they expect to see more widespread use of this technology, and it should soon be possible for it to generate electricity cheaply enough to be competitive. They estimate its worldwide potential to be at least 1,200 terawatt hours per annum. That is about seven percent of the worldwide demand for electricity.
Potential in Europe - 12,500 megawatts
Ocean current power stations may become part of a mature technology for electricity generation. In Europe alone, an EU study has already identified more than 100 areas of sea where up to 12,500 megawatts of electricity could be generated.
Tidal power could make a small contribution. Even the Mediterranean, in which the tidal range is an almost imperceptible 50 centimetres, offers scope for generating power from tidal currents: one example is the Strait of Messina between the Italian mainland and Sicily. However, based on recent studies on the sourcing of energy in Europe, the total generating capacity of all tidal current power plants will account for substantially less than one percent of the demand for electricity. So plants of this kind will only be of any real significance in a handful of coastal regions.
The DLR Energy question of the week in 'The future of energy' Year of Science
The Federal Ministry of Education and Research (BMBF) has given the Year of Science 2010 the motto 'The future of energy'. For this reason the science journalist Jan Oliver Löfken will this year answer a question on the subject of energy in his blog each week. Do you have a question about how our energy supply might look in the future? Or do you want to know, for example, how a wave power plant works and how it can efficiently generate electricity? Then send us your question by per email. Science journalist Jan Oliver Löfken will investigate the answers and publish them each week in this blog.