Oceans cover more than 70 percent of the earth, so there's an immense amount of energy available around the world from both waves and tides. Let's look at how humanity is harnessing that energy. Whether it's dramatically crashing waves or the steady advance of water shoreward as the tide rises, we can easily appreciate the immense amount of energy associated with moving water in the oceans. There are actually other energies to harness from the ocean, including the flow of waters with different temperatures and salinities and therefore different densities. But we're going to focus on wave and tidal energy because they are producing energy today and have the most readily apparent potential. Wave energy isn't harnessed as waves crashing on the shore but offshore. Where the motion of passing waves causes anything floating to move up and down. The energy from this mechanical motion can be converted to electricity and sent ashore via cables. Many different wave energy capture devices have been designed from snake-like attenuators as we see on the right to pumping connections as we see on the left. There are a number of teams researching how best to harness wave energy. Canada's National Research Council, Canadian Hydraulic Center, has mapped available wave power at a number of sites off the west coast of British Columbia. To the south, the pack wave open ocean wave testing facility is under construction a few miles offshore from Newport, Oregon in the United States. This site is open to highly energetic waves crossing the North Pacific, which are even more energetic during frequent winter storms. It's not intended as a commercial power generation facility, but to test wave energy capture technologies. Wave energy is always available. It is not intermittent, like wind and solar. Of course, there are no greenhouse gas emissions associated with it. Why isn't wave energy a dominant energy source today? Let's look at the challenges. Like offshore wind, wave energy generators operate in a hostile marine environment. Large storms damage almost anything mechanical offshore and day-to-day exposure to salt water is highly corrosive. It's difficult to efficiently harvest the energy from waves that are highly variable, both in their height and in their periodicity or frequency. We'd like wave energy installations to be close to shore so that we can monitor them and so that cables can be easily connected to shore. But that makes them vulnerable to highly variable waves associated with storms or even tsunamis on Pacific coastlines. To date, there have been a number of competing designs to make wave energy capture more efficient. But there are no clear front-runner technologies, making it difficult to choose the best design. Large energy companies have also chosen to pursue other technologies, primarily wind and solar, and so we haven't seen organizations investing a lot of money to make successful projects happen. The tides that we see at every shoreline are driven by the gravitational pull of the moon. They vary as the Earth rotates every day. Depending on where you are, you may see two high tides and two low tides every day or just the one, depending on the distribution of land and ocean circulation. The tide moves immense volumes of water towards and away from shore and thus encapsulates a huge supply of energy. Where that energy is sufficiently concentrated, we can capture it to produce electrical energy with turbines, much like a hydroelectric station onshore. At the Bay of Fundy on Canada's east coast, the tide rises and falls more than 10 meters every day, producing vast regular flows of water that engineers have been trying to harness for decades. Like most resources, tidal energy is distributed unevenly around the world. This map shows tidal range, the difference in sea surface height between high and low tides. Where tidal range is highest in the red to black colors, the amount of tidal energy available is greatest such as offshore Western Europe, Western Canada, Western Central America, and the northwestern coast of Australia and New Zealand. Low tidal ranges such as in the Gulf of Mexico, Caribbean Sea, Western Australia, and the Mediterranean offer little tidal energy potential. There are two primary tidal energy technologies being used today. Tidal range installations harvest the energy created by the difference in head or elevation between low and high tides. Here, we see the world's first tidal barrages installed on the Rance River in Northwestern France in 1966. Tides flow from the open ocean into a nine square mile tidal basin and back out again. The 750-meter-long barrage spans a narrow point on the inlet and forces the flow through a relatively narrow opening where turbines capture energy from the water, moving both in and out of the basin. It is still one of the largest tidal barrage installations in the world with a peak capacity of 240 megawatts. It produces an average of 57 megawatts, a 24 percent capacity factor on a very regular schedule. In a year, it produces about 540 gigawatt-hours of electricity sufficient to power a city of 200,000 people. Tidal current installations harvest energy from natural tidal current flows, much like a wind turbine harvests energy from the wind. They are ideal in places where large volumes of water move through relatively narrow points such as at the Bay of Fundy. A variety of turbine designs have been proposed and built. Because water is so dense compared to air, the blades are smaller and turn more slowly than wind turbine blades. Many are still in the testing stages and have to be designed to operate in very hostile marine settings subject to immense daily energy fluxes of tidal currents as well as storms. Like wave energy, tidal energy offers huge potential energy resources. There are essentially no associated greenhouse gas emissions, and although tidal energy is intermittent, it generates power on a very regular and predictable scale. Why hasn't tidal energy become a dominant renewable in the world today since its first installation 55 years ago? Let's look at the challenges. Like offshore wind and wave energy, tidal energy generators are vulnerable to storm damage and corrosion from saltwater. Tidal energy installations have very high capital costs. Particularly because every project is so unique that it is difficult to develop economies of scale. It's challenging to develop efficient tidal current turbines that don't interfere with one another and to design electrical interconnections and linkages to shore. Nearshore ecosystems are easily damaged by tidal installations that can create major changes to the flow of water in bays and estuaries. Similar to wave energy, large energy companies have chosen to pursue other technologies, primarily wind and solar. We haven't seen organizations investing a lot of money to make successful projects happen. The National Renewable Energy Laboratory in the United States shows that there is tremendous potential for marine energy, including wave and tidal, equal to more than half of the total energy generated by the country. The Canada Energy Regulator also highlighted the potential for tidal energy development in Canada, noting several producing and test site projects. There are new projects constantly under development in many countries with good wave and tidal energy resources, but few of them have been commercialized so far. There's also exciting potential for remote coastal communities not well-served by existing electrical grids. Some people compare the state of the wave and tidal energy industries to the wind industry 30 years ago, saying it's just a few years until it enjoys widespread success. Such predictions have been made before, so we'll have to see when the predictions come true. That's the last of the primary energy sources we have to examine. Next, we're going to talk about electricity and its role in the energy transition.