Did you know that hydroelectricity is the world’s biggest source of renewable energy? According to recent figures from the International Renewable Energy Agency (IRENA), it represents 40% of total capacity, ahead of solar (28%) and wind (27%). This type of energy is generated by hydroelectric power stations, which are essentially large dams that use the water flow to spin a turbine. They can also serve secondary functions such as flow monitoring and flood control. To help you learn more about hydropower, we’ve visualized the five largest hydroelectric dams in the world, ranked by their maximum output.
Overview of the Data
The following table lists key information about the five dams shown in this graphic, as of 2021. Installed capacity is the maximum amount of power that a plant can generate under full load. At the top of the list is China’s Three Gorges Dam, which opened in 2003. It has an installed capacity of 22.5 gigawatts (GW), which is close to double the second-place Itaipu Dam. In terms of annual output, the Itaipu Dam actually produces about the same amount of electricity. This is because the Parana River has a low seasonal variance, meaning the flow rate changes very little throughout the year. On the other hand, the Yangtze River has a significant drop in flow for several months of the year. For a point of comparison, here is the installed capacity of the world’s three largest solar power plants, also as of 2021:
Bhadla Solar Park, India: 2.2 GW Hainan Solar Park, China: 2.2 GW Pavagada Solar Park, India: 2.1 GW
Compared to our largest dams, solar plants have a much lower installed capacity. However, in terms of cost (cents per kilowatt-hour), the two are actually quite even.
Closer Look: Three Gorges Dam
The Three Gorges Dam is an engineering marvel, costing over $32 billion to construct. To wrap your head around its massive scale, consider the following facts:
The Three Gorges Reservoir (which feeds the dam) contains 39 trillion kg of water (42 billion tons) In terms of area, the reservoir spans 400 square miles (1,045 square km) The mass of this reservoir is large enough to slow the Earth’s rotation by 0.06 microseconds
Of course, any man-made structure this large is bound to have a profound impact on the environment. In a 2010 study, it was found that the dam has triggered over 3,000 earthquakes and landslides since 2003.
The Consequences of Hydroelectric Dams
While hydropower can be cost-effective, there are some legitimate concerns about its long-term sustainability. For starters, hydroelectric dams require large upstream reservoirs to ensure a consistent supply of water. Flooding new areas of land can disrupt wildlife, degrade water quality, and even cause natural disasters like earthquakes. Dams can also disrupt the natural flow of rivers. Other studies have found that millions of people living downstream from large dams suffer from food insecurity and flooding. Perhaps the greatest risk to hydropower is climate change itself. For example, due to the rising frequency of droughts, hydroelectric dams in places like California are becoming significantly less economical. on
#1: High Reliability
Nuclear power plants run 24/7 and are the most reliable source of sustainable energy. Nuclear electricity generation remains steady around the clock throughout the day, week, and year. Meanwhile, daily solar generation peaks in the afternoon when electricity demand is usually lower, and wind generation depends on wind speeds.As the use of variable solar and wind power increases globally, nuclear offers a stable and reliable backbone for a clean electricity grid.
#2: Clean Electricity
Nuclear reactors use fission to generate electricity without any greenhouse gas (GHG) emissions.Consequently, nuclear power is the cleanest energy source on a lifecycle basis, measured in CO2-equivalent emissions per gigawatt-hour (GWh) of electricity produced by a power plant over its lifetime. The lifecycle emissions from a typical nuclear power plant are 273 times lower than coal and 163 times lower than natural gas. Furthermore, nuclear is relatively less resource-intensive, allowing for lower supply chain emissions than wind and solar plants.
#3: Stable Affordability
Although nuclear plants can be expensive to build, they are cost-competitive in the long run. Most nuclear plants have an initial lifetime of around 40 years, after which they can continue operating with approved lifetime extensions. Nuclear plants with lifetime extensions are the cheapest sources of electricity in the United States, and 88 of the country’s 92 reactors have received approvals for 20-year extensions. Additionally, according to the World Nuclear Association, nuclear plants are relatively less susceptible to fuel price volatility than natural gas plants, allowing for stable costs of electricity generation.
#4: Energy Efficiency
Nuclear’s high energy return on investment (EROI) exemplifies its exceptional efficiency. EROI measures how many units of energy are returned for every unit invested in building and running a power plant, over its lifetime. According to a 2018 study by Weissbach et al., nuclear’s EROI is 75 units, making it the most efficient energy source by some distance, with hydropower ranking second at 35 units.
#5: Sustainable Innovation
New, advanced reactor designs are bypassing many of the difficulties faced by traditional nuclear plants, making nuclear power more accessible.
Small Modular Reactors (SMRs) are much smaller than conventional reactors and are modular—meaning that their components can be transported and assembled in different locations. Microreactors are smaller than SMRs and are designed to provide electricity in remote and small market areas. They can also serve as backup power sources during emergencies.
These reactor designs offer several advantages, including lower initial capital costs, portability, and increased scalability.
A Nuclear-Powered Future
Nuclear power is making a remarkable comeback as countries work to achieve climate goals and ultimately, a state of energy utopia. Besides the 423 reactors in operation worldwide, another 56 reactors are under construction, and at least 69 more are planned for construction. Some nations, like Japan, have also reversed their attitudes toward nuclear power, embracing it as a clean and reliable energy source for the future. CanAlaska is a leading exploration company in the Athabasca Basin, the Earth’s richest uranium depository. Click here to learn more now. In part 3 of the Road to Energy Utopia series, we explore the unique properties of uranium, the fuel that powers nuclear reactors.
