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Hydroelectric energy is the type of renewable energy most familiar to a man. How good is it? Should we use it more or should we use it less? Here's an article where we take a long hard look at hydroelectric dams and compare them to solar.
Key takeaways
Hydroelectric energy harnesses the power of moving water to generate electricity. This technology has been around for over a century, with the first hydroelectric power plant built at Niagara Falls in 1879. Today, it remains one of America's largest renewable energy sources. Hydropower plants create electricity by using flowing water from rivers to turn turbines, offering a reliable alternative to fossil fuel generation without requiring fuel inputs like coal or natural gas.
The fundamental principle behind hydroelectric generation is remarkably straightforward. Water stored in a reservoir behind a dam creates potential energy. When released, this water flow through turbines, converting kinetic energy into mechanical energy. The turbines spin generators that produce electricity – the same electricity that powers our homes, businesses, and farms. Unlike fossil fuel plants, hydropower plants don't burn fuel to generate electricity, making them a clean energy source with minimal air pollution impact.
Not all hydroelectric systems are massive dams. The industry recognizes several distinct categories:
Hydroelectric power accounts for over 6% of total U.S. electricity generation and over 30% of renewable electricity generation. The output has remained relatively stable over the years at around 270-290 billion kilowatt-hours annually.
The reduction in percentage comes not from declining hydropower but from the rapid growth of solar and wind energy. Washington, Oregon, and California lead the nation in hydroelectric generation, with Washington deriving over 66% of its electricity from hydropower.
Despite limited growth in recent years, the U.S. Department of Energy estimates that we could increase hydroelectric capacity by 50% through modernizing existing facilities and developing new small-scale and pumped storage projects. Building more pumped storage facilities would help address one of the main challenges of increasing wind and solar generation by providing large-scale energy storage solutions for the grid. This makes hydropower an important complement to other renewable energy sources.
What is good about hydroelectric energy that made it so popular around the world? Let's look at the pros.
Unlike fossil fuels, water is continuously replenished through the natural water cycle. As long as we have rainfall and snowmelt, hydroelectric facilities can generate power indefinitely. Hydropower stands as one of our most reliable renewable energy sources, with an advantage that few other clean energy options can match. A well-maintained hydroelectric turbine can operate for 50+ years with minimal component replacement – far longer than most other generation technologies.
50+ years
– average lifespan of a hydroelectric turbine
Hydroelectric systems boast impressive efficiency rates of 90% or higher when converting water's energy into electricity. Compare this to fossil fuel plants (roughly 35-60%) or even solar panels (typically 15-22%), and you'll understand why engineers appreciate hydropower's efficiency. This makes hydropower plants among the most efficient electricity generators in our power system.
90% and more
– average efficiency of hydroelectric turbines
This efficiency translates directly to your bottom line. For every unit of water energy captured, you're getting more usable electricity than with virtually any other generation method. The environment benefits too, as this efficiency means we can create more power with less overall impact compared to many other energy sources.
Once constructed, hydroelectric facilities cost remarkably little to operate. They require minimal staff, consume no fuel, and components last decades with proper maintenance. There are facilities that operate at less than 1 cent per kWh in maintenance and operation costs – significantly lower than any other generation method.
Most major hydroelectric dams have already paid back their construction costs many times over. The Hoover Dam, built in 1936, continues to generate power at a fraction of the cost of newer facilities. While initial construction costs for large hydropower projects can be substantial, their extreme longevity makes them cost-effective over time – a major advantage when comparing the pros and cons of different energy sources.
Unlike intermittent renewables, hydropower provides consistent baseload generation that grid operators can count on. Many facilities can increase or decrease output within minutes to match changing demand, something particularly valuable for grid stability.
Dispatchers often rely on hydroelectric facilities to balance loads when solar production dropped in the evening or when unexpected demand spikes occurred. This reliability advantage makes hydroelectric power an important backbone of the electricity grid that can support greater integration of wind and solar resources, which vary with weather conditions.
Beyond electricity, hydroelectric dams offer crucial flood control, irrigation, and water supply functions. Many of America's largest dams, including Hoover Dam and Grand Coulee Dam, were built partially for these purposes.
Farmers in particular benefit from the irrigation capabilities of these systems. The controlled release of water from reservoirs has transformed formerly arid regions into productive agricultural land.
Reservoirs created by hydroelectric projects provide significant recreational value. Fishing, boating, swimming, and camping opportunities abound at these man-made lakes. Lake Mead (Hoover Dam) and Lake Roosevelt (Grand Coulee Dam) attract millions of visitors annually, generating substantial tourism revenue for surrounding communities. For property owners near these facilities, this can mean increased property values and business opportunities.
Not everything is great about hydroelectric energy. Let's now look at the disadvatages of dams and turbines.
The construction of large dams fundamentally alters river ecosystems. Reservoirs flood valleys, forests, and wildlife habitats. The natural flow pattern of rivers changes dramatically, affecting species that evolved alongside these waterways. This environmental impact represents one of the most significant cons of hydroelectric energy when comparing it with other renewable sources like solar and wind, which typically have less dramatic effects on natural habitats.
Dams create physical barriers that block migratory fish like salmon, steelhead, and American shad from reaching spawning grounds. Despite the installation of fish ladders and other passage technologies, many species still struggle to navigate these obstacles. For example, the Columbia River Basin has seen dramatic declines in salmon populations since the construction of major dams, necessitating expensive mitigation programs and affecting both commercial and recreational fishing.
Contrary to popular belief, hydroelectric reservoirs aren't always carbon-neutral. When vegetation decomposes underwater in reservoirs, it can release methane – a potent greenhouse gas with 25 times the warming potential of CO2. This is particularly problematic in warmer climates and shallow reservoirs.
Recent studies indicate that some hydroelectric facilities may produce more greenhouse gases per unit of electricity than initially calculated, though still significantly less than fossil fuel alternatives.
Building a new dam requires enormous capital investment. Even smaller systems demand significant upfront costs, creating financial barriers for many potential projects. A medium-sized impoundment facility can easily cost hundreds of millions or billions of dollars.
Factoid: Experts estimate the cost of a hydroelectric plant to be around $3,000,000 to $6,000,000 per MW for plants larger than 10 MW
While these costs amortize over decades of operation, they present substantial financing challenges, particularly for smaller entities and developing communities. The construction cost of large hydropower plants often exceeds that of equivalent fossil fuel facilities by a significant margin, though their fuel-free operation eventually compensates for this difference. When weighing the pros and cons of hydroelectric energy, this high upfront cost remains an important consideration.
Many major dam projects have required relocating entire communities. The construction of Tennessee Valley Authority dams displaced thousands of families in the mid-20th century. While modern projects typically include comprehensive relocation plans, the social and cultural disruption remains significant.
Reservoirs gradually fill with sediment carried by incoming rivers, reducing storage capacity and power generation potential. This process, called siltation, can dramatically shorten a dam's useful lifespan without expensive dredging operations.
Some older facilities now face significant challenges with accumulated sediment. The Sanmenxia Dam in China lost over 66% of its storage capacity within a decade due to unexpectedly high siltation rates.
Climate change has increased drought frequency in many regions, directly impacting hydroelectric generation. During California's 2012-2016 drought, hydroelectric output fell by nearly 60%, forcing greater reliance on natural gas generation. The potential for reduced water flow during drought periods is among the most serious cons of hydroelectric energy in an era of climate change.
How does hydroelectric energy fare against solar? Is it better or worse? Let's compare the two.
Hydroelectric systems and plants are generally out of question for homeowners. These are projects that are developed by the government or large businesses. On the other hand, home solar systems are common and a proven way to bring down your energy bills.
Hydroelectric and solar energy represent fundamentally different approaches to renewable generation. Hydropower provides consistent, dispatchable electricity with capacity factors typically between 40-60% (meaning they produce at 40-60% of their maximum theoretical output over time). Large hydroelectric facilities can generate hundreds or thousands of megawatts continuously.
Solar, by contrast, produces only during daylight hours with capacity factors around 25% in optimal locations. Wind power typically achieves capacity factors of 35-45% in good locations but varies with weather patterns. However, both solar and wind can be deployed virtually anywhere with suitable conditions, while hydropower requires specific geographic and hydrological conditions.
A 1-acre hydroelectric reservoir in a good location can generate approximately 10 times the energy of 1 acre of solar panels. However, finding suitable new hydro locations is increasingly difficult, while solar potential remains largely untapped.
The economics of these technologies differ dramatically:
Hydroelectric:
Solar:
Solar installations offer tremendous flexibility in siting and scaling. They can integrate with existing structures (rooftops, parking canopies) or use marginally productive land. Installation typically takes days or weeks rather than years.
Hydroelectric facilities demand specific geographical features and typically flood substantial land areas. A large dam might require 5-10 years from planning to operation and face rigorous environmental review and permitting processes.
For farmers and rural landowners, this distinction is crucial. I've helped several agricultural clients implement solar arrays that continued to allow agricultural use underneath or around panels. Hydroelectric development typically removes land entirely from production.
Both technologies offer substantial environmental benefits compared to fossil fuels, but their impacts differ significantly:
Hydroelectric concerns:
From an environmental perspective, large-scale hydroelectric development faces more significant regulatory challenges today than utility-scale solar, reflecting the more profound ecological changes dams typically create. While hydropower is a clean energy source that provides renewable electricity without burning fossil fuels, its impact on river environments represents one of the notable cons of hydroelectric energy that must be carefully weighed against its benefits to the broader environment and climate.
Let's sum up what we've learned in a table. Here's how hydroelectric and solar energy differ from one another.
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Andrei has been a news editor and freelance writer for a number of medias before joining the A1 SolarStore. Climate change and its impact on people's lives have always been among his interests and it partially explains his degree in Philosophy and Ethics.
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