Abstract
In Canada’s Haida Gwaii archipelago, roughly 120 km off the northern coast of British Columbia, the north electrical grid uses more than 7 million liters of diesel to provide power to about 2500 people each year (the south grid uses roughly 3 million liters for roughly 2000 people). For long-term resident Laird Bateham, the predictability of the tides pointed to an obvious alternative. He founded Yourbrook Energy Systems in 2010 to develop a turbine for harvesting power from the local tidal currents. He and his team developed a prototype and are beginning front-end engineering of a project intended to deliver 500 kW of clean and reliable power to the isolated coastal community. That would provide for 20% of the population’s average annual use. His colleague Clyde Greenough says, “We want to leave the world a better place by doing our part to slow climate change.”
The twice-daily rise and fall of the tides drives powerful, predictable currents when seawater flows toward and away from Earth’s coastlines. A turbine placed in the current’s path can harness that power. The moving water pushes the turbines’ blades, causing them to spin and drive a rotor that powers an electrical generator.
Tidal power has been harvested since the Middle Ages, when people retained incoming tidewater in storage ponds and used the outgoing flow to turn waterwheels for milling grain. In modern times, the world’s largest tidal power plants are located in France and South Korea, with 240 MW and 254 MW electricity generation capacity, respectively. There, dam-like structures called barrages span ocean inlets or bays to capture incoming tidal water and generate electricity as the basin fills and empties. The installations can control flows using sluice gates, but because barrages are large scale (making them expensive to construct), they can disrupt the local ecosystem by altering lagoon salinity and animal movements.