What Is Hydropower Renewable Energy?
What is Hydropower?
Hydropower, also known as hydroelectric power, refers to the generation of electrical energy using moving water. It is one of the oldest and largest sources of renewable energy in the world. Hydropower harnesses the kinetic energy of flowing or falling water to produce electricity (Energy.gov, 2023).
The concept behind hydropower is simple – as water flows, it has kinetic energy that can be transformed into mechanical energy to run a generator and produce electricity. A hydropower plant uses a dam on a river to store water in a reservoir. When the water is released from the reservoir, it flows through a turbine, causing it to turn. The turbine spins a generator to produce electricity (EIA, 2023).
Overall, hydropower utilizes the natural gravitational force of flowing or falling water to convert its kinetic energy into electricity without consuming water in the process. It is considered a renewable source of energy as it relies on the water cycle to replenish the water in the reservoir.
History of Hydropower
The earliest evidence of using water to create power dates back to ancient Greece and Rome, where water wheels were used for milling flour and grinding grain [1]. The Romans were one of the first civilizations to use water wheels extensively, developing different types of water wheels for various applications [2].
In the late 19th century, hydropower began to take the form of generating electricity. In 1880, the Wolverine Chair Factory in Michigan became the first industrial site to generate electricity from water [3]. This was followed soon after by the first hydroelectric power plant in Appleton, Wisconsin in 1882, which powered a paper mill and a home.
The early 20th century saw massive growth in hydropower, especially in the western United States. Major projects like the Niagara Falls plant in 1895 and Hoover Dam in 1936 established large-scale hydroelectric power. By 1940, hydropower provided 40% of the electricity in the United States. The largest growth occurred between 1930-1970, seeing over 45,000 megawatts of new hydropower capacity.
How Hydropower Works
Hydropower utilizes the power of moving water to generate electricity. It relies on the water cycle, where water evaporates, forms clouds, precipitates, and flows back down to Earth’s surface (Department of Energy, n.d.). The process starts with a dam constructed to store water from a river or reservoir. The dam creates a height difference and acts as a battery, storing potential energy via the elevated water (EIA, 2023).
When electricity is needed, valves in the dam open to release water from the reservoir through tunnels in the dam. The moving water spins turbines connected to generators to produce electricity. The generators convert the mechanical energy from the moving water into electrical energy that can be distributed via power lines. The height difference created by the dam allows the water to build up substantial pressure and kinetic energy to spin the turbines. Dams essentially act as batteries, charging with potential energy when water accumulates in the reservoir, then discharging electricity on demand when water is released to spin the turbines (Department of Energy, n.d.).
Types of Hydropower Plants
There are three main types of hydropower plants:
- Impoundment: This type uses a dam to store river water in a reservoir. Water released from the reservoir flows through a turbine, spinning it to generate electricity. The water may be released either to meet changing electricity needs or to maintain a constant reservoir level.
- Diversion: With this type, a diversion structure channels part of a river through a canal or penstock, which delivers it to turbines. It does not require the use of a dam or impoundment.
- Pumped Storage: Pumped storage facilities pump water from a lower reservoir to a higher reservoir for storage, using electricity when demand is low. During periods of high electrical demand, the water is released back down to the lower reservoir through a turbine to generate electricity.
Two other common types are:
- Run-of-River: This channels a portion of a river’s water through a canal to spin turbines. It requires little or no impoundment or damming of the river.
- Micro Hydropower: Using small drops in elevation or flow within a river, micro hydropower systems generate under 100 kilowatts of electricity, often for a single home or small community.
Different sites lend themselves to different types of hydropower projects based on factors like terrain, water flow, and electricity demand cycles. Each type has its own advantages and disadvantages.
Sources: https://www.energy.gov/eere/water/types-hydropower-plants, https://www.hydropower.org/iha/discover-types-of-hydropower
Advantages of Hydropower
Hydropower offers several key advantages that make it an important renewable energy source:
Renewable – Hydropower is considered a renewable energy source because it relies on the water cycle. As long as there is flowing water, hydropower can produce electricity without depleting resources.1
Reliable – Hydropower can reliably generate electricity as needed since output can be adjusted quickly to meet demand. Reservoirs provide storage to generate power when renewable sources like wind and solar are unavailable.2
Flexible – Hydropower plants can start up quickly and adjust output to compensate for variables like changes in electricity demand and supply from other sources.
Low Operating Costs – Once a hydropower system is built, operating costs are relatively low compared to other sources. Fuel costs are negligible since hydropower relies on flowing water.
Disadvantages of Hydropower
While hydropower is a renewable and clean energy source, it does come with some downsides. One major disadvantage of hydropower is the high upfront costs associated with constructing dams and reservoirs. Large hydropower projects can cost billions of dollars to build, requiring substantial long-term investments 1. This makes financing new hydropower projects challenging.
Additionally, hydropower dams and reservoirs can negatively impact fish migration and aquatic habitats. The presence of dams can obstruct the migration routes of fish like salmon that move upstream to spawn. Dam reservoirs also flood valleys and forests, altering natural habitats both upstream and downstream2. Protecting fish species and minimizing environmental impacts requires the construction of fish ladders and hatcheries, adding to the costs.
Hydropower Capacity
Global installed hydropower capacity reached 1,380 GW at the end of 2021, according to the International Hydropower Association’s 2022 Hydropower Status Report [1]. This represents a net increase of 26 GW from 2020. The top countries for installed capacity are China (384 GW), Brazil (109 GW), the United States (80 GW), Canada (81 GW) and Russia (49 GW). Together, these top five countries account for nearly 60% of global hydropower capacity.
In the United States, hydropower capacity was 80.25 GW in 2019, accounting for 6.7% of total installed electricity generation capacity, according to the U.S. Department of Energy [2]. U.S. hydropower capacity has increased by a net 431 MW since 2000.
Hydropower Generation
According to the International Energy Agency, global electricity generation from hydropower in 2022 was approximately 4,300 terawatt-hours (TWh), accounting for over 16% of total global electricity generation. Hydropower remains the largest source of renewable electricity worldwide.
Some key facts about hydropower generation globally and in major producing countries:
- China generated 1,360 TWh from hydropower in 2022, representing around 31% of global hydropower generation.
- Brazil produced 415 TWh from hydropower in 2022, making it the second largest producer worldwide.
- Canada generated around 380 TWh from hydropower in 2022.
- The United States generated about 300 TWh from hydropower in 2022.
- Russia produced around 180 TWh from hydropower in 2022.
Hydropower generation has continued to expand globally, but the growth rate has slowed compared to previous decades. Key factors impacting future growth include climate change, environmental regulations, and competition from other renewables like wind and solar.
Future of Hydropower
The future of hydropower looks promising, with growth projections estimating expanded capacity in the coming years. According to the U.S. Department of Energy, hydropower generation could grow from 101 gigawatts of capacity in 2015 to nearly 150 gigawatts by 2050.
New technologies are enabling further growth in hydropower capacity. Advanced turbines, modular and low-head hydropower systems, and generating units integrated into water pipes and tunnels offer ways to increase generation at existing dams and develop new hydropower resources.
There is also significant potential to develop micro hydropower projects. Small hydropower systems with a capacity under 10 megawatts can provide distributed electricity generation to local communities. According to the Department of Energy, micro hydropower could grow from 22 gigawatts of current capacity to nearly 30 gigawatts by 2050.
With technology improvements and initiatives to expand micro hydropower, the role of hydropower is expected to grow as part of America’s renewable energy portfolio. Hydropower provides clean, flexible baseload power that supports expanded wind and solar generation on the grid.
Hydropower’s Role in Renewables
Hydropower plays a major role in renewable energy production around the world. In 2019, hydropower accounted for around 71% of renewable electricity generation globally, making it the largest renewable electricity source (1).
Compared to other renewable sources like solar and wind power, hydropower has some key advantages. One is its flexibility – hydropower plants can adjust their output quickly to meet shifts in electricity demand. Solar and wind power are more variable as their output depends on weather conditions. Hydropower can complement these other renewables by providing power when the sun isn’t shining or wind isn’t blowing (2).
Additionally, hydropower offers energy storage capabilities through pumped storage plants. At times of low electricity demand, excess power can be used to pump water uphill into a reservoir. When electricity demand rises, the stored water can be released to generate hydropower. This makes hydropower a crucial tool in balancing electricity grids and integrating higher shares of variable renewables.
