Several different types of power stations operate on river water. These include run-of-the-river power stations, small scale plants, and Coal-fired power stations. Each type has its own specific impact on the environment.
Sources of hydroelectric energy
Using water to generate electricity is a simple and effective method of harnessing renewable energy. It is also a clean, reliable energy source that has low emission levels compared to other forms of energy.
Hydroelectric power is generated by transforming kinetic energy in moving water into electrical energy. A shaft spins turbine blades, which then turn a generator to produce electricity.
There are two basic types of hydroelectric power stations: dammed and run-of-river facilities. Dammed facilities use a dam to impound a river, and the water is collected at a higher elevation. The difference between the elevations is called head. The higher the head, the more electricity can be produced.
Compared to other energy sources, hydropower is one of the cleanest sources of energy. This is due to the fact that it produces no combustible fuel. It also reduces the production of particulate matter, and combats the greenhouse effect.
However, the construction of a hydroelectric power station can have a negative impact on the environment and local communities. Some dams are very large, and their failure can be catastrophic to downstream communities.
For many years, dams have been relatively safe. However, they have displaced communities and local cultures, and have also caused significant damage to aquatic ecosystems.
To ensure the long-term viability of hydroelectricity, it is crucial to integrate these facilities into the natural landscape. This includes integrating them into existing river systems and watercourses.
To determine the best sources of hydroelectric energy, it is important to consider the amount of water flowing into the reservoir. The amount of energy available to the moving water is dependent on the size of the flow, the elevation, and the volume of water.
Run-of-the-river power plants
Unlike traditional hydroelectric power plants that use reservoirs, run-of-the-river hydroelectricity plants use the river to generate power. They are typically installed on rivers with high year-round flow rates.
Run-of-the-river plants can produce less than 100 kilowatts up to 50 MW. Small plants are stand-alone systems, while larger plants can generate hundreds to thousands of MW.
The amount of power generated by a run-of-the-river hydroelectric power plant depends on the flow of water and the head of the river. Water is diverted from the river, sent through a turbine, and returned to the river downstream. When the flow of water is below the design flow value, the power generated by the plant will decrease. This can result in a reduction of fuel for the river system.
A dedicated steady-state model is a good tool for energy production analysis in run-of-the-river power plants under different hydrological conditions. The model is able to take into account other dependencies, such as generator and inverter efficiency. It has a modular structure, allowing for easy implementation of SHP control techniques.
The model is developed for both low-head and variable-speed run-of-the-river SHPs. It was verified on a real SHP.
This system is designed to supply energy to customers based on their current demands. It can serve local loads and improve the stability of the local grid. It can also be used in combination with a PV system to minimise energy fluctuation.
Hydropower schemes can be modeled by taking into account the changes in river flow and water head. It is also important to analyse turbine discharge. This is important because turbine discharge affects the efficiency of run-of-the-river hydroelectricity plant.
Run-of-the-river power plants are generally installed on high elevations above fast-flowing rivers. However, they may also be installed on small scale dams.
Coal-fired power stations
Unlike renewable sources of energy, coal-fired river power stations are reliant on water. A large amount of water is used to cool the steam produced in the turbine. This water is lost through evaporation. In addition, coal power plants leak toxic metals into our water supply. This has caused significant problems for vulnerable communities, such as coal miners and farmers.
Some of the best ways to use coal for energy is to convert it into a gaseous state or to transport it to distant locations. This is easier than producing electricity from hydropower. It also produces less pollutants than renewable sources.
Coal-fired power stations are typically built on inexpensive land along the edges of rivers. Often, these plants are built next to coal mines.
To produce steam, coal is typically pulverized and then burned in a coal-fired boiler. The boiler uses steam generated by the coal to turn turbines, which spin generators to produce electricity. The steam is cooled to water and then returned to the boiler.
This process is simpler than producing electricity from a nuclear power plant. A coal-fired plant is also cheaper to run than a hydropower plant, which requires a dam and requires a reliable source of water.
Coal-fired power plants are also less prone to seasonal fluctuations than wind power. Using coal also helps reduce air pollution. However, it is important to note that coal is not environmentally friendly and may lead to climate change.
The United States Environmental Protection Agency has issued several air and mercury regulations. Additionally, the Department of Justice filed several civil complaints against coal-fired power plants in the Southeast.
A 2012 NAACP report found that residents living within three miles of a coal-fired power plant had an average per capita income of $18,400. It also found that people of color were three times more likely to live near a coal power plant than white residents.
Despite a shaky economic backdrop, small hydroelectric power plants are proving themselves worthy of a closer look. A quick perusal of the Tennessee Valley Authority (TVA) website should reveal a number of small hydropower projects in the works. And while a few of them are slated to retire in the near future, four small units have been performing well for nearly four decades.
A flurry of contracts are in the pipeline courtesy of companies like FirstEnergy, a subsidiary of FirstEnergy, and a consortium of utilities. Some companies have taken the small scale hydro power plant concept to the next level with a multi-unit, multi-year contract with TVA to build four units on the Clinch River. These units could produce an estimated 11 million watts of net electrical power. The company is also planning a pilot project to construct a second fleet of units for demonstration purposes.
Despite the hype, there is one notable omission in this small field of dreams. Smaller scale projects have the potential to be a lot more complex to plan and implement than they actually are. For example, a study from the MIT Energy Research Laboratory showed that the cost to design and construct a single unit on the Clinch could be over $1 billion. While this is more than many of the stateside competitors, it also means that a significant portion of the potential electricity could be locked up in the ground. So while it is nice to know the cost of power has been reduced, the fact remains that small scale projects can be a nightmare to plan and implement. One snag to avoid is the regulatory quagmire of permitting.
Impact on the environment
Developing hydropower projects can affect the ecosystem of a river. This can include changing the flow, water temperature, water quality, and habitats. Reservoirs are also created, which can affect the biological and physical characteristics of the river.
Reservoirs can also impact fish migration. Fish populations can be decreased, which has negative consequences for the marine ecosystem. They can also negatively affect the habitats downstream of the reservoir.
In addition, reservoir water can have higher nutrient and sediment load than normal river water. This can lead to eutrophication of the river. Methane can also be formed in some reservoirs. This can also cause pollution.
Flow regulation is one way of mitigating negative impacts of hydropower projects. Minimum flow releases are necessary to maintain hydrological continuity of the river. However, inadequate water releases can reduce the flow and therefore harm plants and animals.
In addition, dams that create reservoirs can alter the flow regime, altering water chemistry, silt loads, and habitat connectivity. Various mitigation measures must be considered early in project planning.
Baseline ecological data is needed to determine the impacts of hydropower projects. This requires cooperation between researchers and river management. Before-after studies can be conducted to understand the impact of hydropower on river habitat.
The impact of run-of-river (ROR) hydropower on the environment is a relatively understudied area. The focus of research has been on two key modifications that result from hydropower.
A limited number of direct studies have reviewed the literature on the impacts of water abstraction and in-channel barriers. However, this has not been sufficient to determine the ecological impact of ROR hydropower.
Studies on schemes with significant depleted reaches should also explore ecological differences and identify the impacts of hydropower’s altered flow regime. Numerical modelling of hydraulic impacts can also complement field data collection and make impact studies more comprehensive.