The Wave of the Future

Tidal estuaries are great fishing for some and a source of clean, limitless energy for others.

By Sage Lazzaro

Tidal energy, energy collected from the ebb and flow of the tides, has the potential to become a major source of energy in the near future. Recent developments with the technology have shown that tidal energy has more than just the ad­vantages it shares with other forms of re­newable energy: it solves the problems other technologies don’t.

Harnessing Tidal Energy

In 2012, America’s first commercial tidal-power system began sending power to the grid. After years on the backburner, tidal power has emerged with new technology, making it possible for tidal energy to power homes and businesses. Companies developing tidal power for commercial purposes are now using tidal stream, the newest method for harness­ing tidal energy. Tidal stream devices, called tidal tur­bines, work like wind turbines and extract the kinetic energy from the movement of tidal currents as they ebb and flow. Currents turn the turbines’ blades around a rotor that spins a generator to create energy. The energy is then sent through an underwater cable to an onshore sub­station where an electricity transmission company distributes power to the grid.

Last August, Ocean Renewable Power Company (ORPC) installed a tidal-pow­ered turbine in the Gulf of Maine’s Bay of Fundy. In September, the turbine — known as TidGen® — became the coun­try’s first commercial tidal-power system to send power to the grid.

Been Around for a Long Time

Tidal power has been seen as a largely untapped resource throughout the last century. President Franklin Delano Roosevelt saw the potential in the Bay of Fundy’s record-breaking high tides and championed the construction of the Quoddy Dam in 1935. Although never completed, the dam was set to be a tidal barrage dam, which would use tidal range technology, an early form of tidal power.

Tidal barrage dams collect energy from water by taking advantage of the differ­ence between the high and low tides.Instead of damming water on one side like a conventional dam, a tidal barrage allows water to flow in during high tide and later be released during low tide, spinning turbines to capture the energy as the water flows in and out.

This first attempt at a large-scale tidal power plant failed, but other tidal bar­rages were constructed in France, Russia, and Cuba during the 1960’s. Because of their high capital costs and negative im­pacts on surrounding ecosystems, few of these tidal barrages exist, but those that were constructed were successful in har­vesting energy from the tides.

A Revolution

Tidal power has re-emerged with new technology that is making it possible to harness tidal energy. Companies de­veloping tidal power for commercial purposes are now using tidal stream technology. This method completely bypasses the need for dams, and instead, uses turbines alone. Tidal stream devices, called tidal turbines, work similarly to wind turbines and extract the kinetic energy from the movement of tidal currents as they ebb and flow. The currents turn the turbines’ blades around a rotor that spins the gen­erator to create energy. The energy is then sent through an underwater cable to an on-shore substation where an elec­tricity transmission company distributes the power to the grid.

Tidal stream energy is a form of hydro-kinetic marine technology, a broader cat­egory of hydropower that harvests the kinetic energy in water, using more than just the tides. Strong currents in some rivers, straights, inlets, and narrow chan­nels are ideal, for they force the water to run through narrow spaces, magnifying the tidal currents and consequently, the available energy. It isn’t a coincidence that the offshore location with the world’s highest tides was the site for FDR’s dam, as well as the location for the first commercial tidal-power system. 100 billion tons of water flow in and out of the Bay of Fundy with the force of 8,000 locomotives each day.

ORPC installed a cross flow vertical axis tidal turbine in the Bay of Fundy last August and has been sending power to the grid since September. Currently, the turbine has a peak output of 180kW of energy and is maintaining a rated capac­ity of 150kW. This means that 150kW is the amount of output the generator can sustain 100 percent of the time. Over the next few years, the company plans to install additional turbines to in­crease the energy output to 5 MW, which is enough electricity to power 2,000 homes and businesses.

Tidal Power’s Potential

Tidal power has many advantages over other types of energy generation, making it ripe for further development and implementation. It is clean, renew­able energy that burns no fossil fuels and doesn’t produce emissions of any kind. Most importantly, it solves the problems surrounding other sources of renewable: energy: predictability and consistency.

ORPC’s CEO and President, Christopher R. Sauer, believes tidal power has the po­tential to become a major power source “There aren’t many areas in the world where there couldn’t be appli­cations for this technology,” Sauer said. “We’ve known when the tides are coming and going for hundreds of years."

Tidal energy is already more effective than solar power and more constant than wind power. Solar panels only harvest the sun’s energy if the sun is shining, and wind turbines only rotate if the wind is blowing. Tides are predictable and tur­bines can be placed where the flow of water is constant.

Other sources of energy, both renew­able and nonrenewable, are unsightly and are very expensive to maintain. Tidal turbines are underwater and completely out of sight. They have few operating costs once installed and have fewer negative environmental impacts than dams. Barrage dams have several adverse effects as they impede fish migration, block navigation, and can change downstream tides.

One of the biggest concerns with tidal power technology is the potential risks for sea life. Last March, ORPC published their first annual environmental report, indicating “no observed adverse inter­action with the marine environment” at the site of their turbine in the Bay of Fundy. The turbines turn slowly and do not funnel water into them, so there is no risk of sea animals being sucked into the turbine. Sea animals have been shown to simply avoid the turbines like they would a rock.

One disadvantage of tidal turbines would be the potential difficulties with upkeep. It is possible that the harsh, salty, under­water conditions and rough currents will damage turbines easily and frequently. However, ORPC has experienced very few difficul­ties with its turbine since it was installed almost a year ago. Loose bolts and a few electronic issues have been the only problems thus far. The company is proud that it has experienced no problems with the technology itself. This success is undoubtedly due to ORPC’s unique turbine design, constructed specifically to withstand the harsh, underwater conditions.