When you think of the East River in New York City, renewable energy probably isn't the first thing that comes to mind. Yet the river, once a cesspool and dumping ground for an occasional body, has found itself at the forefront of the green-energy movement. In September 2012, Trey Taylor, owner of Verdant Power, sank a special three-bladed electric turbine into the waterway that runs along Manhattan's east side. Taylor designed the turbine, which looks like a modern fan attached to a torpedo-shaped body, to generate electricity from the push and pull of the river's rushing currents [source: McGeehan].
By 2017, 30 of those turbines could dot the river, with each unit generating 35 kilowatts of electricity. If successful, the project could provide enough power to fuel hundreds of homes. Made of plastic and layered fiberglass, the East River tidal turbines are one of several technological innovations rocking the hydroelectric world [source: McGeehan].
From one end of the planet to the other, scientists and engineers are working on a variety of concepts — some real, others imagined — that will help make this very ancient power source an even more important modern one. These days, 6 percent of U.S. electricity comes from hydropower (that's 70 percent of the renewable electricity generated in the U.S.) [source: U.S. DOE]. The supply is limitless, although not every area is a good place to build a hydroelectric project.
If you're a freshwater fish like a trout, the last thing you want to see is a dam. Dams prevent the upstream movement of juvenile fish to the waters where they'll spawn and live out the rest of their days. Environmentalists have long bemoaned the havoc dams can wreak. Enter fish ladders.
One of the most technologically advanced fish ladders is in Montana at the Thompson Falls hydroelectric plant on the Clark Fork River. It's the first full-length fish ladder in the continental U.S. designed specifically for bull trout, a threatened species. The $8 million, 72-foot (22-meter) high ladder has 48 steps that the fish may climb [sources: Holyoak, PPL Montana].
Fish swimming upstream are attracted to the small opening at the base of the ladder by discharged water. They begin their ascent up the steel and concrete fish ladder, battling rushing water each step of the way. Each of the 48 steps, or pools, is about 5 feet (1.5 meters) wide and 6 to 10 feet (1.8 to 3 meters) long and has openings at the top and bottom. The fish eventually reach a 17-foot (5-meter) gathering pool and then a holding tank. Once inside the tank, scientists examine and tag the fish, which are then released above the dam [sources: Holyoak, PPL Montana].
Fish ladders don't always work as well as they're designed to though. A separate University of Massachusetts Amherst study found that only a small percentage of fish populations are safely passing through the dams researchers observed [source: Adams].
Nature knows a thing or two. All you have to do is look. When a hydropower engineer and a medical scientist put their noggins together at the end of the 20th century, they came up with a new way to boost the power of existing hydroelectric stations by nearly 10 percent [source: Piesold and Caro]. All they did was apply the spiral-shaped design of human blood vessels to create a similarly shaped penstock pipe.
The helicoid penstock is similar to a rifle barrel, which has spiral grooves etched inside. Rushing water flows through the helicoid penstock, and like a bullet through a rifled barrel, begins to spin. The pipes focus the flow of the water directly on the electric turbine, improving the turbine's performance [source: Piesold and Caro].
It looks good on paper, but inventor Rick Dickson says his idea can work when put to the test. Dickson is talking about a hydroelectric generator that takes advantage of the immense pressure differentials in the deep water of lakes or oceans. He calls it a hydrosphere and believes it can generate up to 500 megawatts of continuous renewable energy [source: Scoop].
Although he has yet to build a prototype or secure a patent, Dickson's hydrosphere is a type of enclosed, cylindrical hydroelectric dam that works off the varying pressure of ocean or lake water [source: Scoop].
The hydrosphere led Dickson to another invention, the Air-Water-Gravity generator, which he believes is the hydropower plant of the future. The AWG is a large, hollow cylinder filled with air and anchored to the seafloor at varying depths. An electrical generator sits inside the cylinder. To generate power, a valve lets water into the device under great pressure. The flowing water enters a vacuum chamber and forces a piston to climb a stator, the stationary part of the generator on which a rotor spins. As the piston moves up the stator, it generates electricity [source: Free Press Release].
When the piston reaches a metal stop at the top of the stator, it releases a valve connected to a hollow snorkel pipe at the base of the cylinder. The pipe opens, allowing air to decompress. That forces the rotor down the stator, once again generating electricity. Water is also pushed out of the cylinder at great force and out the snorkel pipe to the surface of the ocean. The water shoots out of the top of the pipe like a geyser. The release valve then closes, the water intake reopens, and the cycle repeats itself. Depending on its size and the depth on which it is placed in the ocean, the AWG can produce up to a half a gigawatt of continuous power [sources: Free Press Release, Beyond Fossil Fuels]. The device hadn't been prototyped or patented at the time of publication.
The echo of waves slamming against a rocky shore or a sandy beach is a soothing sound. Did you know that it's also an energetic sound? Kinetic energy is the energy of movement, and rushing water is brimming with it. That's because wave motion is fueled by the wind and oceanic geology [source: Union of Concerned Scientists].
Engineers and scientists have come up with a variety of devices to harness the hydrokinetic energy generated by waves. In fact, scientists say if we could extract only 15 percent of the energy along the U.S. coast (specifically the West Coast), the United States could generate as much electricity as all the hydroelectric dams in the nation [source: Union of Concerned Scientists].
Speaking of hydrokinetic energy, have you ever gone swimming in the ocean? Did the outgoing tide drag you from shore? Tides pack a powerful punch, and we can use them to generate electricity.
In 2012, one of the first tidal power projects in the United States began delivering power to the electrical grid. The project, an underwater turbine off the coast of Maine, was built by Ocean Renewable Power Co. The turbine resembles an old-fashioned lawn mower, but in essence is a type of undersea windmill. The turbine's foils rotate when the tide rushes in and out of Cobscook Bay near Eastport. The tides in the area are some of the highest in Maine, reaching 20 feet (6 meters). The $21 million generator can power 25 to 30 homes [sources: Sharp, Woodard].
Damming a river to generate electricity is so 20th century. Dams not only alter the landscape, but they can also affect wildlife (remember those fish ladders we mentioned?). What if we could harness the power of the river without building dams and reservoirs? A California-based company called Bourne Energy believes it has found the answer [source: Bourne Energy].
The company's RiverStar system harvests kinetic energy all along a river rather than in one spot, as dams do. Here's how it works: Engineers place a number of "modules" across a river. Each module is made up of a turbine, a stabilizer, a mooring system and an energy conversion system. High-tension steel cables hold each unit in place and connect one to another in an array. Flowing water passes through the turbines, and as they spin, they collect the river's energy, which drives a generator. Bourne officials say RiverStar can generate 50 kilowatts in a river with a water speed of 4 knots. The company adds that RiverStar does not affect the migration patterns of fish or impede river traffic.
In 2007, Michael Bernitsas, a professor at the University of Michigan, found a way to harness the kinetic energy of a flowing river by looking at how fish move through water. He created a device he calls VIVACE, which is short for Vortex Induced Vibration for Aquatic Clean Energy [sources: Vortex Energy, Lafay].
As any trout fisherman can tell you, when a school of fish moves through water, the fish curve their bodies and create tiny swirling vortices. The fish push their bodies off the vortices to propel themselves forward. VIVACE works the same way. Engineers place a series of cylinders on the river or ocean bottom. The passing current flows over the cylinders creating vortices, which move the cylinders up and down. Inside each cylinder is a magnet that moves over a metal coil, generating an electrical DC current. VIVACE then takes the DC current and converts it into AC. Unlike other hydrokinetic technologies, Bernitsas' invention can harness energy from slow-moving rivers [sources: Vortex Energy, Lafay].
Sewer lines, freshwater lines, wastewater pipes and conduits -- almost every town has some sort of water pipe snaking through it. What if there were a way to harness the power of rushing water passing through municipal pipes? A new invention has done just that.
An Israeli company called Leviathan has created a water turbine that can be enclosed in a pipe. When water rushes pass the turbine, it generates electricity. The device, called the Benkatina Turbine, works off the water flowing through enclosed water pipes, sewer pipes, canals and pipes that remove wastewater from factories [source: Leviathan Energy].
Imagine turning your home into a mini hydropower plant. That's exactly what Fulton Innovation has in mind. The Michigan-based company has created Lilliputian hydroelectric technologies that can power electric radios, speakers, clocks and TVs, using the water coming out of a bathroom faucet.
At the heart of the Fulton's Splashpower technology is a device called a Miniature Hydroelectric Generator. Such generators produce electricity by using the water flow in a house or building. Every time you run the water with a Splashpower mini-generator, you can power sprinkler systems, emergency lighting, a water softener and even outdoor camp lighting The mini-hydroelectric devices can also be used to charge batteries [source: Splashpower].
Can evaporation provide electric power? Learn more about new experiments in renewable energy in this HowStuffWorks article.
Author's Note: 10 Innovations in Hydropower
Have you ever wondered why most people live near bodies of water? Water made it easy to get to one place to another. Sources of water were used for farming. In addition, hydropower was the energy of choice for centuries. The history of hydropower is, in essence, the history of humankind. The ancient Greeks used their muscle to grind flour by hand. They then invented one of the first water wheels that made the job so much easier. They and others applied that technology to textile-making, woodworking and other uses. Over the centuries, we have devised new and better ways to harness the power of rushing water, such as those in this article.
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