Hydropower has been used for hundreds of years at small scales to power windmills on farms but has massive potential to provide commercial electricity for entire cities and parts of the country. Hydroelectric dams can either harness the power of fast-flowing rivers or release a large amount of water that collides with turbines to generate electricity. Hydropower has been limited by the very specific geographic locations that make hydropower viable and has limited hydroelectric dams to areas that either have the space for a reservoir to form behind the dam or a change in elevation that water can flow downhill. Systems that harness the natural changing of the tides, as well as wave power, have the potential to make hydropower a more adaptable energy source for regions that lack the space for reservoirs and do not have mountainous areas.
The tides of the world’s oceans are affected by the gravitational pull of the moon and sun. The tidal range can change in parts of the U.S. by a maximum of up to 40 feet. Tidal energy systems can generate electricity, but generally requires a tidal change of at least 10 feet to generate an economical amount of energy. A tidal barrage can capture the change in the tide by pushing water through a turbine at the bottom of the barrage as the tide moves into and out of a shoreline. The mouths of rivers are the best locations for tidal barrages, as the downstream flow of the river and the natural movement of the tides will push more water through barrage turbines. The largest tidal barrage facility in South Korea can produce 254 megawatts (MW) of electricity and the range of tidal systems from standalone turbines to large barrages mean that these systems can be easily adapted to different marine environments.
Wave power differs from tidal power in that wave power systems can be anchored in deeper water or float on the ocean and capture the kinetic energy of waves. Waves have long been a potential source of energy, as waves produce 32,000 terawatt-hours (TWh) of energy per year. The largest barrier to harnessing wave energy is the ocean itself. Due to storms, the natural corrosion of saltwater, and rogue waves mean that wave power generators can be damaged or sunk by rough water. Systems like the surge wave energy converter have attempted to solve this problem with windows that allow waves to pass through the device while still capturing the waves kinetic energy. By anchoring the energy converter to the bottom of the sea, it also allows for boat traffic to bypass navigating these devices in commercial waters.
With continued investments into tidal and wave energy systems, costs will be driven down. Currently, 35-50 percent of wave energy costs are spent on making the devices able to withstand the thrashing of the waves themselves. The visual drawback of having wave energy systems on shorelines that would otherwise be huge draws for tourism has also been an economic hurdle. However, the massive amount of energy contained in the world’s oceans have the ability to broaden the viability of hydropower to other states.
Written by Roy Mathews, Former Public Policy Associate
The Alliance for Innovation and Infrastructure (Aii) is an independent, national research and educational organization. An innovative think tank, Aii explores the intersection of economics, law, and public policy in the areas of climate, damage prevention, energy, infrastructure, innovation, technology, and transportation.