[audio:http://wamcradio.org/EarthWise/wp-content/uploads/2014/04/EW-04-29-14-Lunar-Power.mp3|titles=EW 04-29-14 Lunar Power]
Almost all our energy ultimately derives from the Sun. There is of course solar power, but even hydroelectric, wind, and wave power are actually driven by the Sun’s energy. Fossil fuels originate from prehistoric plant matter created by photosynthesis. The only major non-solar sources are nuclear power and geothermal energy, which itself results from nuclear reactions in the Earth’s interior.
An up-and-coming exception is tidal power, which mostly arises from the Earth’s interaction with the moon. Energy from tides can be exploited in two ways: tidal streams that make use of strong tidal currents to drive turbines, and tidal barriers which make use of rising and falling tides to power turbines.
Tidal energy systems are attractive in locations where incoming waters funnel into narrow channels or where underwater valleys force currents to constrict. Thus places like Swansea Bay in South Wales and North America’s Bay of Fundy are prime locations.
The first U.S. grid-connected tidal facility is in the Bay of Fundy and came online in 2012. A new plant in Washington’s Puget Sound has just been approved for construction. The world’s largest proposed tidal plant, the 320-megawatt tidal lagoon project in Swansea Bay, has just been green-lighted by the UK’s Planning Inspectorate.
Tidal stream systems are like wind turbines, except that seawater is 832 times denser than air. As a result, slow ocean currents are as effective as gale-force winds in generating energy. As people look to exploit the world’s choice locations for tidal power, we may find ourselves entering the age of lunar power.
**********
.
Web Links
Tidal energy proposal accepted by U.K.’s Planning Inspectorate
Photo, taken August 22, 2007, courtesy of Peasap via Flickr.
.
Earth Wise is a production of WAMC Northeast Public Radio. Support for Earth Wise comes from the Cary Institute of Ecosystem Studies in Millbrook, NY.