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How Ocean Power Works


Concerns about Ocean Power
manhattan bridge over east river
ŠiStockphoto.com/zinchik
Verdant Power is testing its underwater turbines in New York City's East River, which potentially could produce up to 1,000 megawatts.

Despite its enormous potential, ocean power has contributed very little to global electricity production. Like all renewable energy providers, ocean power companies must overcome several hurdles to rival the market share of fossil-fuel suppliers. One of the biggest hurdles is reliability. Marine environments can wreak havoc on mechanical systems, making them difficult to maintain. Verdant Power installed six tidal turbines in New York City's East River in 2006, only to find that strong tidal flows damaged all but two of the systems.

Issues like these make it difficult for ocean power to compete with fossil fuels on cost. Some estimates put the cost of wave energy between 9 and 16 cents per kilowatt-hour. For tidal energy, which benefits from advancements made in wind technologies, the cost is somewhat lower -- about 6 to 9 cents per kilowatt-hour [source: Ocean Renewable Energy Coalition]. But neither is nearly as cost-effective as coal, which costs just 3 cents per kilowatt-hour, or natural gas, which costs 4.7 cents per kilowatt-hour [source: Wald].

Then there are environmental issues. Placing large man-made structures in the oceans will clearly have some effect on marine life. Tidal barrages present perhaps the biggest challenges. The turbines in these structures can kill fish and impede their migration to spawning areas. Barrages also interfere with the normal flushing of silt and other dissolved pollutants. This affects water quality, which in turn affects bird and fish life. The table below summarizes some of the major concerns associated with ocean power.

Source of Ocean Power

Concerns

Waves

Variable intensity, limited survivability of equipment, navigation and sea-space concerns, release of lubricants

Tides

Slack intervals, high capital costs, limited to a handful of sites worldwide, major environmental impacts

Tidal Currents

Limited survivability of equipment, high operational costs, less widespread than waves

Ocean Currents

Limited number of sites, potential impact on ocean circulation patterns

Ocean Thermal Energy

High capital costs, limited to sites in tropical oceans, sites far from land must transmit electricity long distances


Of course, all of these issues must be weighed against the benefits of ocean power. The biggest is its ability to produce carbon-free energy. That alone may make ocean power one of the most important energy sources in the coming decades.


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