Is Hydroelectric Renewable Or Nonrenewable?

Hydroelectric power is the process of harnessing the energy generated from moving water to produce electricity. It works by directing water from a high elevation through turbines connected to generators that convert the kinetic energy into electrical energy. Hydroelectric power plants make use of the gravitational force of falling or flowing water to produce electricity that can be used immediately or sent into the electrical grid for consumers.

This article will examine whether hydroelectric power is considered a renewable or nonrenewable source of energy. It will provide an overview of how hydroelectric generation works, discuss the factors that categorize it as renewable or not, and analyze the potential limitations and environmental impacts.

Table of Contents

Hydroelectric Power Generation

Hydroelectric power plants generate electricity from flowing water. At a hydroelectric dam, water builds up pressure in the reservoir behind the dam. When water is released from the reservoir, it flows through large pipes called penstocks and pushes against turbine blades to spin a generator that converts the mechanical energy of the spinning turbine into electrical energy. The electricity is then transferred through transformers to increase the voltage and transport the electricity long distances over transmission lines to homes, businesses and industries.

According to the U.S. Energy Information Administration, turbines inside hydroelectric power plants can have outputs ranging from a few kilowatts up to hundreds of megawatts (1 megawatt = 1,000 kilowatts). Water constantly flows through the turbine, spinning a shaft connected to a generator that converts the mechanical energy into electrical energy through electromagnetism.

The major components in a hydroelectric power plant include:

Dam – stores river water in a reservoir
Intake – controls water flow into penstocks/turbines
Penstock – large pipes that deliver water to the turbines

Turbine – converts kinetic energy of falling water into mechanical energy
Generator – converts mechanical energy into electrical energy
Transformer – steps up low voltage electricity for transmission

Overall, hydroelectric facilities utilize basic principles of physics to harness the energy in flowing water for generating carbon-free renewable electricity (U.S. Energy Information Administration).

Renewable vs Nonrenewable

Renewable energy comes from natural sources that are constantly replenished. Some examples of renewable energy sources include solar, wind, geothermal, hydropower, and biomass. Renewable energy is considered clean energy because it produces little to no global warming emissions (source).

Nonrenewable energy comes from sources that will eventually dwindle and become too expensive or environmentally damaging to retrieve. The most common nonrenewable energy sources are fossil fuels like coal, oil and natural gas. These resources take millions of years to form naturally and cannot be replenished on a human time frame (source).

The key difference between renewable and nonrenewable energy is that renewable sources are naturally replenished, while nonrenewable sources cannot be replaced once depleted. Renewable energy is considered sustainable and better for the environment long-term. However, nonrenewable sources currently make up most of the world’s energy consumption.

Is Hydroelectric Renewable?

Hydroelectric power should be considered a renewable energy source because it relies on the water cycle, which is continuously replenished by the sun. The fuel source for hydroelectric generation is flowing water, which is not depleted or used up in the process. The water cycle is driven by the sun’s heat, which causes water to evaporate from oceans and lakes and form clouds. This water vapor then condenses and falls back to Earth as precipitation, replenishing water flows in rivers and streams (Benefits of Hydropower). This continuous solar-powered cycle means that hydroelectric power generation essentially relies on an endless supply of flowing water.

Hydroelectricity uses the energy of running water to produce electricity, without reducing the quantity of water. In this way, hydropower is considered a renewable energy source because it does not deplete its fuel source like fossil fuels do. The kinetic energy of flowing water turns the blades of a turbine, which spins a generator to produce electricity. The water continues flowing downstream after passing through the turbines. This process can be repeated indefinitely as long as there is adequate water flow, making hydroelectric generation renewable (Hydroelectric Power: Advantages of Production and Usage).

Potential Limitations

Although hydroelectric power has many benefits, there are some potential limitations to consider. One is that viable hydroelectric sites are geographically limited based on water sources. Building a hydroelectric dam and reservoir requires specific topographical conditions, like a narrow valley with enough water flow and elevation drop to produce power. Many ideal hydro sites have already been utilized in developed countries. While some suitable sites remain, they may be remote or difficult to access. Existing dams may have potential for upgrades, but geographic limitations constrain hydro’s total expansion. Countries without major rivers or elevation changes have fewer opportunities for hydro projects.

The best hydroelectric sites offer natural advantages from high precipitation, consistent water flow, and mountainous terrain. Areas without these attributes have fewer cost-effective options to capture the energy in moving water. While pumped storage can add capacity, this requires surplus power to pump water uphill. Ultimately, geography and water resources restrict where hydroelectric dams can be situated. This contrasts with solar and wind power that have wider geographic flexibility. With finite ideal sites, hydroelectricity has natural limits for growth despite its renewable nature.

Environmental Impacts

While hydroelectric power is considered a renewable energy source, hydroelectric dams can have significant environmental impacts. Some key considerations include:

Habitat disruption – Building dams floods land upstream, which can destroy forests, wetlands, and wildlife habitats. This flooding converts river habitat and land into an artificial lake habitat.
Changes to water quality – Dams change the flow of rivers and can degrade water quality by slowing water flow, trapping sediments, and altering water temperature.
Impact on fish migration – Dams can block fish passage and prevent access to spawning grounds upstream. Some dams install fish ladders to help mitigate this.

Erosion and sedimentation – Dams change sediment transport and can cause erosion downstream as well as build up sediments in the reservoir.
Greenhouse gas emissions – While dams don’t directly emit greenhouse gases, the decomposition of flooded organic material can produce methane and carbon dioxide.

According to the Union of Concerned Scientists, hydroelectric reservoirs cover up to 1% of the earth’s continental surface and can have significant local environmental impacts. However, compared to fossil fuels, hydroelectric’s lifecycle greenhouse gas emissions are typically much lower.

Efficiency and Reliability

Hydroelectric power is one of the most efficient ways to generate electricity, with efficiencies typically over 90% (1). This means that over 90% of the mechanical energy from falling water can be converted into electrical energy. In comparison, fossil fuel plants typically have efficiencies around 30-60%.

The high efficiency of hydroelectric stations results from the direct mechanical conversion of falling water into turbine rotation before electrical conversion. There are minimal thermal losses, unlike fossil fuel plants which lose a significant portion of energy to heat during combustion.

In addition to high efficiency, hydroelectric power is extremely reliable. According to a study by the U.S. Department of Energy, hydroelectric dams provided consistent electricity even during severe droughts when output from other sources declined (2). The ability to store water in reservoirs gives hydropower stations a buffer during reduced water flow periods.

The Electric Power Research Institute estimates that a 1% improvement in hydroelectric availability could save the U.S. utility industry over $100 million per year (3). This demonstrates the high degree of reliability already achieved with hydroelectric systems.

Overall, hydroelectric stands out for its exceptional efficiency and reliability as an electricity source.

(1) https://www.energy.gov/eere/water/articles/study-finds-hydropower-provides-reliable-electricity-even-during-historic

(2) https://www.epri.com/research/products/EM-3435

Usage and Capacity

Hydroelectric power accounts for over 16% of electricity generation globally. According to Statista, the total installed hydroelectric capacity worldwide was 1,308 gigawatts (GW) as of 2022. China has by far the largest share with 414.8 GW, followed by Brazil (109 GW), Canada (81 GW), and the United States (80 GW). Other major producers include India, Norway, Turkey, Japan, and Russia.^[1]

In terms of hydroelectricity generation, China again leads with 1,328 terawatt hours (TWh) produced in 2022. Brazil produced 428 TWh, Canada 392 TWh, and the United States 260 TWh. Hydroelectricity makes up roughly 71% of Brazil’s total electricity generation and 60% in Canada. For China and the United States, hydroelectricity comprises around 16% and 7% of total generation respectively.^[2]

Many countries have significant potential to further expand hydroelectric capacity. The top countries by technical potential are China, India, Brazil, Turkey, Japan, Russia, and the United States. However, growth has slowed in recent years due to droughts, environmental concerns, and the focus on developing other renewable sources like wind and solar.

^{[1] https://www.statista.com/statistics/474652/global-total-hydropower-capacity-in-major-countries/}

^{[2] https://www.statista.com/statistics/474799/global-hydropower-generation-by-major-country/}

Cost Factors

Hydroelectric power has relatively high upfront capital costs but low operating costs. Building a hydroelectric dam and power plant requires major civil engineering and construction work which can cost billions of dollars. For example, the Three Gorges Dam in China cost over $26 billion to build. In the U.S., capital costs for hydroelectric average around $2,500 per kW of installed capacity, higher than natural gas at $1,000/kW or wind at $1,300/kW.

However, once built the operating costs are very low, averaging around $30 per MWh in the U.S. This is much lower than fossil fuel plants that require continual fuel purchases. Coal power costs around $60/MWh while natural gas combined cycle plants average around $40/MWh in operating costs. This means hydroelectricity has a lower levelized cost over the project lifetime despite the high initial investment.

Overall, hydroelectricity remains very cost competitive with other electricity sources. The U.S. Energy Information Administration estimates the levelized cost of hydro at around $56 per MWh, cheaper than geothermal, biomass, or offshore wind. Only onshore wind and solar PV are less expensive renewable options per MWh of generation.

Conclusion

Hydropower provides approximately 16% of the world’s electricity supply, making it a crucial component of the global renewable energy mix. When looking at the full life cycle of a hydroelectric dam, from construction to power generation, there is a strong case for classifying hydroelectricity as a renewable energy source. The fuel source of flowing water is continuously renewed through the natural water cycle and hydroelectric turbines can generate carbon-free electricity for decades.

However, hydroelectric facilities also have drawbacks that must be considered. Large dams can obstruct fish migration, alter downstream river ecology, and displace communities. There are also limits on suitable sites for new hydroelectric dams. Upgrading existing facilities is often the most sustainable approach, maximizing efficiency and capacity through technological improvements.

Overall, hydroelectricity remains a major renewable energy source when implemented responsibly. With the pressing need to decarbonize electricity generation, hydroelectric power delivers immense value as a flexible, renewable baseload power supply. Continued innovation and careful environmental stewardship will allow hydroelectricity to play a growing role in a carbon-free energy future.