Harnessing Our Oceans: Can the Tides Power Our Cities?

If you’ve ever stood still on the wet sand of a beach that is being gently caressed with sea water, then you know the power of tides. The waves may be gentle, but they pull the sand out from under your feet with astonishing efficiency. Now imagine being able to harness that energy. Some people…

If you’ve ever stood still on the wet sand of a beach that is being gently caressed with sea water, then you know the power of tides. The waves may be gentle, but they pull the sand out from under your feet with astonishing efficiency. Now imagine being able to harness that energy.

Some people are doing more than imagining. An increasing number of companies are developing methods of converting tidal power into electricity and other forms of energy. Globally, the tidal energy market is estimated to add up to one terawatt. That is roughly the equivalent of the sustained power of 114 megawatts over the course of a year. You can also think of it in terms of usage. The United States consumed 3.8 terawatts of power last year. The entire world consumed about 18 terawatts. As you can see, this is no small number. Though setting the goal at 100 percent of worldwide usage of all usable tidal power is ridiculous, even a small portion of this can be play a huge role in providing clean, renewable energy to the world.

tidal energyTidal Energy: Can We Power Our Cities?

The Two Types of Tidal Energy

Tidal energy comes in two main forms: range and stream. Tidal range energy has been around the longest. It utilizes the differences in height between high and low tides to capture energy. Often, turbines in an artificial barrier generate electricity as the tide flows through them. Tidal stream energy is a newer concept. The idea is to capture the energy generated by water currents much as a wind turbine captures the energy generated by wind currents. Turbines are still utilized, but they are generally more complex.

Tidal Energy Locations around the World

Both types of tidal energy rely heavily on location. Areas with larger differences in tidal height are the most effective generators of range energy, whereas areas with strong currents will be more effective in capturing stream energy. The 50 sites identified as the best places to install range tidal energy systems are all contained in only five regions: the Bay of Fundy in Canada, Bristol Channel and Cardiff Bay in the United Kingdom, Normandy in France, the Magellan Straight in Argentina and Chile, Alaska in the United States and Kamchatka in Russia.

France has been using tidal range power since 1966 when they constructed a 240 MW plant in La Rance. These 24 turbines have been generating energy ever since. In 2011, the South Koreans constructed the Sihwa Lake tidal power station, which then became the largest tidal range plant.

Though tidal stream technologies are still a relatively new concept, headway is being made. Europe can be thought of as a forerunner in this burgeoning industry, with the United Kingdom taking the lead. Much of the country’s zest is due to their unique advantage in the field. The United Kingdom has sites that are ideal for tidal turbine arrays. Pentland Firth, in Scotland, may be the best location of all. This narrow strip of water between Scotland and the Orkney Islands has quick-moving water that could generate significant energy. Experts estimate that tidal turbines in this region alone could produce eight percent of the U.K.’s energy needs.

In 2014, clean energy company MeyGen began building tidal arrays in the area. It is a long-term project, but the company plans to submerge up to 269 tidal turbines on the seabed. They aim to generate enough energy to power 175,000 homes. Once up and running, the turbines can be manned by a team of only 100. The project will be the biggest stream tidal energy project in the world, setting the stage for further development in the area.


One of the main benefits of this type of energy is predictability. The tides can be predicted years in advance. They will not change. This is a huge bonus for any city moving into alternative forms of energy. Cities cannot be fully run on the whims of wind and sunlight. Given the immense opportunities of tide-based energy, why has the industry been so slow to start?

Outlook for Tidal Energy: Now and Tomorrow

Progress for this technology has been slow. One of the reasons for this is its large upfront costs. The infrastructure involved in setting up these plants is astronomical and requires large capital investment. These upfront costs are especially concerning to investors considering current profit margins. The tidal game is long and slow. The plants last forever – La Rance is still up and running from the 60s – which makes them highly profitable in the long run. It takes some time, however, to break even given the high initial investment. Many companies are unwilling or unable to take such a long-term view of their profit margins.

In Europe, these market-based, profit concerns are outweighed by government programs and public investment. Tidal energy certainly wouldn’t be the first energy source to receive a leg-up from the public sector. Even fossil fuels have been supported by governments throughout the years. Perhaps more immediately relevant, however, is that technology is quickly changing the tidal energy industry, making it much more profitable.

Different technologies aimed at increasing efficiency, collecting energy from currents running every which way, and even developing hybrid systems aimed at using stream and range plants to support one another are making the industry more profitable. According to one report, using hybrid systems can improve energy efficiency by 20 percent.

In the United States, the Department of Energy’s Water Power Program is investing in marine and hydrokinetic technologies. More than 50 percent of the nation’s population lives within 50 miles of an ocean coastline, so a cost-effective industry could provide a substantial amount of electrical power for the nation.

Though tidal energy may not be the poster child of alternative energy today, there are many signs that it could be tomorrow. Investors would do well to keep an eye on new technologies and opportunities as they arise.

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