Hydropower is the most common, and the cheapest renewable energy source in the United States. Hydropower is responsible for 6% of the total electricity produced in the US. Hydropower also makes up 67% of domestic renewable electricity, according to the Department of Energy (DOE). Although hydropower is non-polluting, changes in water temperature and flow can affect natural animals and plants near hydropower facilities.

Hydropower is one of the oldest renewable energies that has been used in the US. The first US hydroelectric power plant was built along the Fox Rover, in Appleton, Wisconsin in 1882, but Washington accounts for 31% of all hydroelectricity generated in the US, according to the Energy Information Administration (EIA). Only 2% of all dams in the US produce electricity though, farming and recreational uses are the primary uses, according to the National Hydropower Association.

Hydropower capitalizes on the water cycle. First, surface water is heated by solar energy and evaporates. Once evaporated, water vapor creates clouds and water will eventually fall as some sort of precipitation. Water then travels through rivers and streams back to begin the cycle again from an ocean or lake. Hydropower can be generated along many parts of the water cycle.

Currently there are six different systems that can harness hydropower. Electricity can be generated through run-of-the-river, storage, barrages, tidal fences, tidal turbines, and wave power systems.

Run-of-the-river

Run-of-the-river systems force water from rivers into a pipe, called a penstock, and then the water pushes past a turbine which spins, generating electricity. These systems are fairly basic and do not cause as much disturbance to the flow of the river compared to storage systems.

Storage

Storage systems involve a dam located on a river. Once a river is dammed, a reservoir will be created upstream from the dam. Once the reservoir is formed, on the upstream side of the dam, water will be allowed into the penstock, where it will rush past a turbine on its way through the dam and out the other side to continue downstream.

Tidal barrages

Tidal barrages are a fairly new concept in tide power. A barrage can be thought as a dam in an ocean, but only in one area. Once water rushes in, under the barrage, doors called sluice gates close and trap the tide on one side. When the sluice gates open back up, water rushes back to the other side of the barrage where underneath the barrage, turbines spin when the tide comes past the barrage either direction, according to the BBC.

Tidal fence

Tidal fence systems are a lot like barrages, but they do not have sluice gates. Tidal fences could be under a bridge that goes over water. A tidal fence is an underwater wall with openings. Since there are only a certain amount of openings, water will rush through them faster than in open water. In each opening is a turbine that will spin when water rushes through it, generating electricity.

Tidal turbines

Wind turbines spin as wind rushes through them in areas of high wind, while tidal turbines are underwater turbines that spin when tidal currents rush past them. Since water is 800 times denser than air, tidal turbines need to be much sturdier than wind turbines, according to the DOE. Tidal turbines are more expensive to build compared to wind turbines, but they generate more power.

Wave power

Along US coastlines, 7% of the domestic electricity demand could be met if wave power was captured. Wave power systems focus waves into smaller areas, which will make them more powerful. Waves can be channeled and spin turbines directly, or waves can be channeled into a catch basin for controlled electrical power use, according to the DOE.

Future

Hydropower is more accessible than wind or solar power across the world. Transmission of electricity is often a problem with wind power, but since populated areas are often located on or near waterways, hydropower can be consumed quickly.

Hydropower does affect ecosystems, but research is being done to help the problems that hydropower creates. Fish ladders are used on rivers in the western US, where salmon need to travel large distances to spawn each year. These ladders help the fish reach their destination.

Hydroelectricity is very cheap to produce and also very efficient. Hydropower plants can convert 90% of the available energy in water into electricity, according to the National Hydropower Association. Operating costs at hydropower plants have increased below inflation levels as well.

The cost of producing electricity from hydropower can be less than 1 cent per kWh, according to the Wisconsin Valley Improvement Company (WVIC). WVIC manages 21 storage reservoirs along the Wisconsin River. Efficient hydropower plants can produce electricity for half the cost of nuclear power.

Renewable energy is slowly replacing fossil fuel power plants. The more renewable energy projects that are active, translates to less fossil fuel power plants in production. Prices are becoming more competitive for renewable energy sources, compared to fossil fuel power plants, and renewable energy is only going to get cheaper. Between the five major renewable energy sources; hydropower, biomass, wind, solar, and geothermal, world power demands can be met and fossil fuel power can slowly be replaced by clean, efficient energy.

-Colvin