What Is Meant By Hydro Power System?
Hydro power, also known as hydroelectric power, refers to the conversion of energy from flowing water into electricity. It is one of the oldest methods of renewable power generation, with the first commercial hydroelectric power plant opening in 1882 in Appleton, Wisconsin (1). Since then, hydroelectric dams and power plants have become an important source of electricity across the world.
Hydroelectric power plants capture the energy of flowing water to generate electricity. The kinetic energy of the moving water turns a turbine, which spins a generator to produce electricity. Typically, a dam is constructed to control water flow and create a reservoir, allowing hydroelectric power to be generated on demand when electricity is needed (2).
As of 2022, hydropower accounted for over 15% of total electricity generation globally, avoiding over 1 billion metric tons of carbon emissions (3). It offers a renewable and sustainable energy source that does not directly produce air pollution or greenhouse gases. Hydroelectric power plays a major role in the renewable energy landscape today.
Sources:
(1) https://www.energy.gov/eere/water/hydropower-basics
(2) https://www.britannica.com/science/hydroelectric-power
(3) https://www.iea.org/reports/hydropower-special-market-report
How Hydro Power Works
Hydro power plants capture the energy of flowing water to generate electricity. There are several types of hydro power systems that utilize dams, rivers, and water reservoirs.1
In dam-based hydro power systems, dams are built to create reservoirs that control the water flow. The water in the reservoir has potential energy due to its height. When released, the moving water flows through turbines, causing them to spin. The turbine spins a generator to produce electricity.2
Run-of-river hydro power systems do not require dams for electricity generation. They divert a portion of a river’s water flow into a channel and through turbines. They have a minimal impact on the river.1
Pumped storage hydro power plants pump water uphill into a reservoir when electricity demand is low. During peak demand times, the water is released to flow downhill through turbines to generate electricity.2
Components of a Hydro Power Plant
The major components of a hydroelectric power plant are the dam, reservoir, penstock, turbine, and generator. Here is an overview of their functions (The Constructor, 2017; HowStuffWorks):
The dam is built across a river to create a reservoir. The dam stores water and controls its flow.
The reservoir is the body of water created by the dam. It stores potential energy in the form of water held at an elevation.
The penstock is a sloped pipeline that delivers water from the reservoir to the turbine. It controls water flow and creates pressure on the turbines.
The turbine converts the kinetic energy of moving water into mechanical energy. There are different types of turbines optimized for different water flow conditions.
The generator is connected to the turbine shaft and rotates to convert mechanical energy into electrical energy. The electricity is then transmitted via power lines.
Types of Hydropower Turbines
There are two main types of hydropower turbines used in hydroelectric power plants:
Impulse Turbines
Impulse turbines are suitable for high head hydropower sites. The water is fed through nozzles which convert the pressure into high velocity jets. These jets strike and spin the turbine runner, which is connected to the generator shaft. The water completely leaves the runner. Common impulse turbine designs are Pelton and Turgo.
Reaction Turbines
Reaction turbines are suitable for low and medium head hydropower sites. The water flows through the turbine runner and creates a reactive force to spin the turbine. Common reaction turbine designs include Kaplan, Francis and Propeller turbines.
The main difference between impulse and reaction turbines is that impulse turbines convert only the kinetic energy of water into electricity, while reaction turbines convert both kinetic and pressure energy. Impulse turbines are suitable for high heads, while reaction turbines are used for relatively lower heads.
Capacity and Generation
Globally, hydroelectric power has an installed capacity of 1,308 GW as of 2022, generating over 4,300 TWh of electricity (IEA). This represents approximately 16% of the world’s total electricity production, making it the largest renewable energy source for electricity generation. While the rate of hydropower installations has slowed down in recent years, it still remains a major source of renewable power across the globe.
China has by far the largest installed hydroelectric capacity at 356 GW, representing over 25% of the global total. This is followed by Brazil (109 GW), Canada (83 GW), the United States (80 GW), and Russia (50 GW) as the countries with the most installed hydro capacity (Statista). In terms of generation, China also leads with over 1,300 TWh produced annually from hydroelectric sources. Other top producers are Brazil, Canada, the United States, and Russia, reflecting their large capacities.
While most major hydropower resources in developed countries have already been utilized, developing countries still have significant potential for new projects. Countries like India, Turkey, Vietnam, and Ethiopia have plans for major hydroelectric dam and plant construction. However, environmental and social concerns have also slowed hydropower growth in recent decades.
Pros of Hydro Power
One of the biggest benefits of hydro power is that it is a renewable energy source. The water in rivers and reservoirs is continuously replenished by rainfall and snowmelt. As long as there is sufficient water flow, hydro power can be generated indefinitely without depleting resources. This makes it very different from fossil fuels which are finite and will eventually run out.
Hydro power systems are also extremely reliable and have a long lifespan. Once constructed, they can operate for many decades with proper maintenance. Many existing hydro power plants have been operating reliably for over 50 years. This steady performance results in low operating costs compared to other energy sources.
Cons of Hydro Power
While hydroelectric power has many benefits, it also has some drawbacks. Three major cons of hydro power are:
High upfront costs. Constructing a hydroelectric plant and dam requires a huge initial investment. The average cost to build a hydro plant in the U.S. is between $1,000 and $3,000 per kW of capacity, significantly higher than fossil fuel power plants (Advantages and Disadvantages of Hydroelectric Energy). The costs include construction materials, heavy equipment, diversion channels, dams, and reservoirs.
Impacts on rivers and wildlife. Damming rivers for hydro power can disrupt natural water flows, change water temperature and oxygen levels, block fish migration routes, and alter surrounding habitats (Earth.org, 2023). Building reservoirs floods vegetation and can force relocation of people living in the area.
Limited suitable sites. Generating hydroelectricity relies on elevated reservoirs of water with adequate flow, vertical drop, and rainfall to maintain water levels. Suitable hydro sites that meet these geographical requirements are limited. The best locations are often in remote areas, requiring long transmission lines to connect generated power to consumers.
Major Hydro Power Countries
The countries with the largest installed hydroelectric capacity in the world are China, Brazil, Canada, and the USA [1]. Here is an overview of their capacities and major projects:
China has the largest installed hydroelectric capacity in the world at over 350 GW as of 2020 [1]. Major hydroelectric projects in China include the Three Gorges Dam on the Yangtze River, which is the world’s largest power station with 22,500 MW of capacity.
Brazil has the second highest hydroelectric capacity at over 110 GW [1]. Major projects in Brazil include the Itaipu Dam on the Paraná River between Brazil and Paraguay, which is the world’s second largest hydroelectric plant, with 14,000 MW of capacity.
Canada has an installed capacity of over 80 GW [1]. Major Canadian hydroelectric facilities include the Robert-Bourassa generating station in Quebec, which has 5,616 MW of capacity.
The USA has an installed hydroelectric capacity of over 80 GW [1]. Major American hydroelectric dams include the Grand Coulee Dam on the Columbia River in Washington state, which is the largest hydropower producer in the USA with 6,809 MW of capacity.
Recent Trends and Innovations
The hydropower industry has seen several key innovations and trends emerge in recent years. One major trend is the increased use of pumped storage hydroelectricity. Pumped storage facilities pump water uphill into a reservoir during periods of low electricity demand and release the water downhill through turbines to generate electricity during high demand periods. Pumped storage improves grid reliability and allows integration of intermittent renewable energy sources like wind and solar (Startus Insights).
Another trend is a focus on small hydro projects under 10 MW capacity. Small hydro can provide clean energy without major environmental impacts associated with large dams. Small hydro utilizes natural streams or irrigation systems to generate modest amounts of localized power (International Hydropower Association).
There have also been advances in hydropower turbine designs. New fish-friendly turbines minimize harm to fish populations. Other innovative turbines enhance efficiency, cost-effectiveness, and flexibility to complement variable renewable energy. For example, very-low-head turbines can operate with heads under 3 meters (Startus Insights).
Future Outlook
The future growth prospects for hydro power look promising, with forecasts predicting steady increases in hydro capacity globally. According to the International Energy Agency (IEA), global hydropower capacity is set to increase by 17%, or 230 GW, between 2021 and 2030.
However, the future expansion of hydro power faces some challenges. Many of the best sites for large hydro dams have already been developed, so growth will come mainly from modernizing existing plants, adding pumped storage capacity, and building smaller hydro projects.
Sustainability is also a major consideration, as hydro projects can impact local ecosystems and communities. New projects will need to adhere to stricter environmental regulations and gain consent from stakeholders.
China currently leads the world in hydro capacity and has major new projects planned, including the 16 GW Baihetan dam which opened in 2021. Other countries investing heavily in new hydro power include India, Turkey, Ethiopia, and Brazil.
In the US, growth is expected to come mainly from efficiency improvements to existing dams, adding power at non-powered dams, and developing new pumped storage. The Department of Energy released a Hydropower Vision report in 2016 outlining pathways for growth.
Overall, hydro power will continue playing a vital role in renewable energy systems globally, leveraging its ability to provide stable, flexible power generation and grid reliability services.
