Where to Take a Tour of the World’s Power Plants

When Congress authorized the construction of a massive dam on the Colorado River in 1928, America had never before seen such a massive undertaking of resources and labor. The Nevada town of Boulder City was developed for the sole purpose of housing the thousands of workers who were to build what would become the Hoover Dam. When complete, the nearly 730-foot-tall structure had used 5.9 million barrels of cement over the 27 years of construction.

The dam was built to divert the Colorado and control flooding by burrowing four massive, 30-foot-diameter tunnels into the walls of Black Canyon, two in Nevada and two in Arizona. Today, nearly 80 years after it began operating, the dam generates about 4 billion kilowatt-hours of hydroelectric power each year, enough to power the lives of 1.3 million people.

This National Historic Landmark has offered guided tours since 1937, drawing one million visitors each year. For $30, individuals can take an elevator 530 feet down through the rock wall of the Black Canyon for a tour through one of the dam’s four tunnels. The metal behemoths are capable of moving 90,000 gallons of water each second from Lake Mead to the dam’s hydroelectric generators.

Back above ground, the power plant balcony offers a panoramic view of the 650-foot-long Nevada wing of the plant, as well as eight of the dam’s 17 generators. An exhibit gallery houses memorabilia from the dam’s 82-year history along with a walk-through model of a generator and a detailed diorama of the entire dam.

There’s just one slight difference between the Hoover Dam and this power plant in New Zealand: the latter is located below ground in the middle of New Zealand’s Fiordland National Park. Housed in a 364-foot-long, 128-foot-high cavern excavated from a solid granite mountain, the station sits nearly 700 feet below the surface of Lake Manapouri.

Manapouri’s initial capacity was to be 700,000 kilowatts. But due to a design problem, the station’s operators risked flooding the powerhouse if they ran the station at so great an output. This went on for 30 years, until the construction of a new tunnel in 2002 pushed the station’s maximum generating capacity to 850,000 kilowatts. Today, Manapouri generates enough electricity each year to power 591,000 homes.

Looking out at the lake, no one would know there was a massive generator churning away in the depths of the water. The only visible hints include a nearby control center building, a switchyard and a pair of transmission lines looping across the lake to link up with the country’s power grid. To reach the cavern for a four-hour-long tour, visitors are ferried 22 miles across the lake to its eastern end. There, they have two options to reach the heart of the plant: They can board a car that zooms down a 1.2-mile spiraling tunnel, or take a two-and-a-half minute elevator ride that descends a distance equivalent to a 70-story building.

Hellisheidi Power Station sits on a site where many would fear to place a big power-generating structure—next to an active volcanic ridge. There, the tectonic plates straddling the Mid-Atlantic ridge, one of the Earth’s major fault lines, are moving apart at a rate of about an inch each year. The risk of a volcanic eruption in the region, known as Hengill, is relatively low—the last eruption was 2,000 years ago—but volcanic activity underground makes Hellisheidi’s home a literal hot spot. As heat from the Earth’s core is pushed toward to the surface, 30 wells reaching 6,500 to 9,800 feet deep drive it into the plant’s turbines to generate electricity.

Hellisheidi is one of five major geothermal power plants in Iceland. Altogether they produce nearly one-third of the country’s energy as well as contribute to geothermal heating efforts that provide hot water and warmth for 87 percent of the country’s housing. At the Hellisheidi plant’s visitors' center, open daily, visitors can learn more about how Iceland uses geothermal energy.

Annapolis, North America’s only tidal power station, harness the power of the world’s most dramatic tide, in the Bay of Fundy on the Atlantic coast. The station generates electricity from water in much the same way that dams like Hoover and Manapouri do. But there’s one big difference: constructing this power plant didn’t require creating a large reservoir or carving out a mountain.

The Nova Scotia tidal station, which opened in 1984, employs rows of turbines that resemble upside-down windmills. Submerged in ocean water, the turbines are spun round and round by the flow of natural currents. The rolling movement keeps the turbines rotating fast enough to power a generator, producing usable electricity. The station generates about 80 to 100 thousand kilowatt hours of electricity every day, an output that depends on the strength of the bay’s tides.

The station’s free visitors' center is open between June and September, offering visitors an overview of the plant’s history and a thorough explanation of how tidal power generation works.

The location of Cruachan Power Station has a more mystical past than most power plants. According to Scottish lore, an old hag named Cailleach Bheur roamed the 3,694-foot Ben Cruachan mountain, guarding a natural spring that welled up at its peak. Every day, she covered the spring with a slab of stone at sundown, removing it at the crack of dawn the following day. One fateful evening, the story goes, Cailleach Bheur fell asleep and forgot to cover the spring, which overflowed and created the present-day freshwater lake of Loch Awe.

The station, opened in 1965, lies just over a half a mile deep inside the mountain and has a capacity of 440 thousand kilowatts. The roughly 1,000-foot-long dam pumps water from Loch Awe into an overheard reservoir, which powers the turbines that produce its electricity. Tunnels snaking through the interior of the mountain collect rainwater, which generates 10 percent of the station’s electricity. The entire station can power up in an impressive two minutes, going from standby mode to peak production based on human demand on the power grid.

The station’s visitors' center is open from February to December, and features interactive displays that explain its operation. Guided tours can take visitors into the heart of the mountain, where tropical plants surround the walkways that lead to Cruachan’s four massive generators.

The largest biomass power plant in the world, Alholmens Kraft, runs on something decidedly old fashioned—wood. But this plant has an electrical power capacity of 265 thousand kilowatts, an amount that could fuel the streetlamps of a road wrapping around the entire planet.

Opened in 2001, Alholmens Kraft’s main fuel comes from forest residues, mostly waste products such as bark and wood chips from the local logging, paper and sawmill industries. The plant burns about 300,000 bales of this material each year. Additional power comes from peat--decayed vegetation, usually mosses--that’s collected from nearby bogs. The plant can also burn coal, but it’s only used as a reserve fuel.

Alholmens Kraft is a cogeneration plant, which means it simultaneously creates electricity and heat. So much heat in fact, that the plant provides enough warmth for all residents of Jakobstad, the city where it’s located. Its biomass-fired boiler operates at a scorching 1,013 degrees Fahrenheit, burning through 28,000 cubic feet of biofuel per hour.

The plant’s visiting address can be found here.