Pumped-storage hydropower facilities are a type of hydroelectric storage system where water is pumped from a water source up to a storage reservoir at a higher elevation and is released from the upper reservoir to power hydro turbines located below the upper reservoir. The electricity for pumping may be supplied by hydro turbines or by other types of power plants including fossil fuel or nuclear power plants. They usually pump water to storage when electricity demand and generation costs, and/or when wholesale electricity prices are relatively low and release the stored water to generate electricity during peak electricity demand periods when wholesale electricity prices are relatively high. Pumped-storage hydroelectric systems generally use more electricity to pump water to the upper water storage reservoirs than they produce with the stored water. Therefore, pumped-storage facilities have net negative electricity generation balances. The U.S. Energy Information Administration publishes electricity generation from pumped storage hydroelectric power plants as negative generation.
Hydropower is one of the oldest sources of energy for producing mechanical and electrical energy and up until 2019, it was the largest source of total annual U.S. renewable electricity generation. Thousands of years ago, people used hydropower to turn paddle wheels on rivers to grind grain. Before steam power and electricity were available in the United States, grain and lumber mills were powered directly with hydropower. The first industrial use of hydropower to generate electricity in the United States was in 1880 to power 16 brush-arc lamps at the Wolverine Chair Factory in Grand Rapids, Michigan. The first U.S. hydroelectric power plant to sell electricity opened on the Fox River near Appleton, Wisconsin, on September 30, 1882.
There are about 1,450 conventional and 40 pumped-storage hydropower plants operating in the United States. The oldest operating U.S. hydropower facility is the Whiting plant in Whiting, Wisconsin, which started operation in 1891 and has a total generation capacity of about 4 megawatts (MW). Most U.S. hydroelectricity is produced at large dams on major rivers, and most of these hydroelectric dams were built before the mid-1970s by federal government agencies. The largest U.S. hydropower facility, and the largest U.S. electric power plant in electric generation capacity, is the Grand Coulee hydro dam on the Columbia River in Washington with 6,765 MW total generation capacity.
Interior showing the reactor hall in Forsmark nuclear power plant, Sweden. Forsmark has three boiling water reactors and is situated on the Swedish east coast. Credit: Matthew Pacey. Acessed via Flickr. CC BY-NC-ND 2.0.
Most scientists and policymakers agree that the energy sector, especially electricity generation, needs to be largely decarbonized by the turn of this century, but they differ on the means by which decarbonization should be accomplished. A variety of low-carbon emission energy technologies currently compete, ranging from fuel-free renewable technologies such as hydroelectric power and wind, solar, and tidal power to fuel-dependent technologies such as biofueled thermal power, nuclear energy, and fossil fuel-based thermal power coupled to efficient carbon capture and sequestration or reuse.
Ultimately, this competition will be settled on the basis of technological readiness and capability, cost competitiveness, and specific technological constraints. For example, hydropower requires building new dams and storage reservoirs, which leads to environmental impacts; biofuels compete with food production for arable land; carbon capture and storage requires safe carbon dioxide storage sites; and nuclear power has raised questions about the safety of both the nuclear power plants and the long-term storage of nuclear waste, as well as the possible role played by nuclear power in nuclear weapon proliferation.
What do these reports reveal? In Sweden, nuclear power is the third cheapest low-carbon energy technology, preceded by wind onshore and large-scale hydroelectric power. One important parameter used to calculate cost in these reports is the cost of capital, or the amount of return on a project necessary for investors to agree the project is worthwhile. There are two standard figures for the cost of capital used in the report: 10 percent and 6 percent. A higher cost of capital, in this case 10 percent, is usually indicative of a higher-risk project, such as a nuclear power plant. The electricity production cost for nuclear power is 57.95 öre/kilowatt hour (kWh), preceded by wind onshore at 54.73 öre/kWh and hydropower at 49.36 öre/kWh. The 2014 electricity production cost excluding policy instruments is shown in Figure 3.
In many countries, including in the United States, both the public and policymakers cite high and unpredictable costs as a primary argument against including nuclear power in a decarbonized energy portfolio. Yet in Sweden, a country with an almost fully decarbonized electricity sector, nuclear power is extremely competitive considering real cost. Real cost is the cost of electricity excluding any economic incentives such as renewable energy credits or carbon taxes. Nuclear is the third cheapest low-carbon energy technology (described above). It is also the most production-efficient low-carbon energy technology. Nuclear power has almost three times the load factor of wind onshore, while only being 3.2 öre/kWh more expensive. When compared to hydroelectric power, nuclear has more than double the load factor and is 8.7 öre/kWh more expensive than large hydro plants and 2.1 öre/kWh less expensive than small hydro plants, working out to just 2.2 öre/kWh more expensive than the average hydroelectric power plant.
When including economic incentives designed to make renewables more competitive, small hydropower plants and large offshore wind farms become cheaper than nuclear power, but nuclear remains cheaper than small offshore wind farms and all forms of solar power (at both 6 percent and 10 percent cost of capital) despite these subsidies. These policies achieve their intended goal of making renewables more affordable, but given its efficiency, nuclear power remains a competitive low-carbon energy technology even with the subsidized effect of electricity certificates.
In 2016, the Swedish government adopted a new agreement on renewable energy policy, with the goal of reaching 100 percent renewable energy production by 2040, superseding the Nuclear Power Phase-out Act of 1980. This agreement explicitly states that this target date is not a deadline for banning nuclear power, nor does it mean closing nuclear power plants. The agreement prohibits reintroducing the Nuclear Power Phase-Out Act and allows for granting permits to replace currently operating reactors and building new ones. While the lede of the agreement seems to suggest that the government is all in on renewables, the text makes clear that Sweden is a long way from giving up the competitive advantage of nuclear power.
 This legislation, passed by the Swedish Riksdag in 1980, followed the US Three Mile Island accident of 1979 and a national referendum on nuclear power in Sweden (which endorsed the elimination of nuclear power); it specifically prohibited any new construction of nuclear power plants in Sweden, and targeted 2010 as the date by which Swedish nuclear power would terminate.
There are three different types of hydroelectric energy plants, the most common being an impoundment facility. In an impoundment facility, a dam is used to control the flow of water stored in a pool or reservoir. When more energy is needed, water is released from the dam. Once water is released, gravity takes over and the water flows downward through a turbine. As the blades of the turbine spin, they power a generator.
Another type of hydroelectric energy plant is a diversion facility. This type of plant is unique because it does not use a dam. Instead, it uses a series of canals to channel flowing river water toward the generator-powering turbines.
The third type of plant is called a pumped-storage facility. This plant collects the energy produced from solar, wind, and nuclear power and stores it for future use. The plant stores energy by pumping water uphill from a pool at a lower elevation to a reservoir located at a higher elevation. When there is high demand for electricity, water located in the higher pool is released. As this water flows back down to the lower reservoir, it turns a turbine to generate more electricity.
Hydroelectric energy is the most commonly-used renewable source of electricity. China is the largest producer of hydroelectricity. Other top producers of hydropower around the world include the United States, Brazil, Canada, India, and Russia. Approximately 71 percent of all of the renewable electricity generated on Earth is from hydropower.
The PPA often sits alongside or is combined with a BOT or concession agreement: in addition to obligations relating to the sale and purchase of the power generated, the project company is also required to design, construct, operate and maintain the power plant in accordance with agreed specifications.
Sale of capacity and energy - the PPA may require the project company both to make available to the purchaser an agreed level of capacity at the power plant and deliver the energy generated in accordance with its provisions.
an availability or capacity charge, which is payable by the offtaker in consideration of the power plant operator making generation capacity available to the offtaker, whether or not it actually offtakes electricity from the power plant. This component is typically designed to provide a revenue floor for the project and is the primary channel through which each project proponent would recover its fixed costs (including its capital investments, financing costs and a return on equity); and 2b1af7f3a8