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11 Important Pros and Cons of Hydroelectric Energy

Hydropower energy is one of the oldest forms of mechanical power in human history, having been used for over 2,000 years to enhance lives across the globe. Today, hydroelectric power plants continue to provide energy to the human experience but just how do they compare to other sources of energy used today? Let’s take a look at some important pros and cons of hydroelectric energy.

Ancient Hydropower

Before we dive in, let’s go back in time to the original hydropower source: the waterwheel.

Waterwheels, a series of paddles placed upon a wheel and connected to a shaft, use the natural flow of a river or stream to harness the energy produced by the moving water.

Roman Waterwheel
Roman Waterwheel. Source, Britannica

Waterwheels were first used in the last century BCE, most notably by ancient Romans and Greeks. They harnessed the natural power of water to grind grain and invented the first sawmill which ran on hydropower and could even cut through solid marble.

The Han Dynasty also utilized early forms of hydropower as far back as 202 BCE. Their waterwheel and piston systems powered trip hammers that ground grain and rock ore.

Hydroelectric Power: How’s It Work?

Detroit Oregon Hydropower Dam

Today, our hydropower systems are much more efficient and sophisticated. Modern hydroelectric power plants convert the raw energy of moving water into electricity utilizing several recent inventions like the 1849 Francis Turbine.

A typical hydroelectric power plant requires a dam to be placed in a large river where the elevation drops and encourages gravity to funnel water through it. The dam creates a reservoir behind it and as the water is pushed through the opening in the dam, it rotates the turbine and generates mechanical energy.

The rotating turbine shaft is connected to a generator where the mechanical energy is then converted to generate electricity, as illustrated in the image below.

See Related: 20 Energy Conservation Techniques to Know

What Do Hydropower Plants Look Like?

Hydropower power plants can be stand-alone dam systems like the Hoover Dam (once the largest hydroelectric producer in the world) or combined into lock and dam systems.

Lock and dam systems are located on rivers or canals. They combine a dam’s ability to generate electricity while allowing cargo and passenger ships to pass through the locks which operate as a water elevator.

Mississippi Lock and Dam 11
Mississippi Lock and Dam #11. Source, U.S. Army Corps of Engineers

Growing up in Dubuque, Iowa, I’ve seen lock and dam systems my entire life. Located on the Mississippi River, one of the longest rivers in the world, Dubuque is home to Lock and Dam #11 out of 29 lock and dam systems. However, only 12 of these systems currently generate hydroelectric power.

Most dams in the United States were not made for hydroelectric power. Let’s take a look at some pros and cons of hydroelectric energy to identify why.

6 Pros of Hydroelectric Power Plants

1. Free and Renewable Energy Source

The flow of rivers and streams is a great renewable energy source.

As water flows downstream, some of it evaporates, turning into water vapor, and rises into the atmosphere. High above the earth, solar energy from our sun engages with the water vapor to create rain, snow, or any other form of precipitation, spilling the water back into water sources. This is called the water cycle.

Hydroelectric power requires water to generate electricity. How lucky for us that 71% of the world’s surface is covered in water, a renewable resource!

2. Minimal Greenhouse Gas Emissions

Though hydroelectric power plants can’t claim a zero-emissions impact, the emissions that are produced are severely less than sources such as coal or nuclear energy.

Coal-burning energy produces mostly air pollutants and other greenhouse gas emissions. The life-cycle emissions of generating electricity by the use of coal currently sit between 1.4 and 3.6 pounds of carbon dioxide per kilowatt-hour.

On the other hand, nuclear energy is completely free of air pollutants but instead produces radioactive waste which must be contained and stored safely as it decomposes over thousands of years.

The renewable energy of hydroelectricity produces no radioactive waste and very low amounts of air pollutants.

While some massive hydroelectric power plants have a life-cycle emissions statistic of 0.56 pounds of carbon dioxide per kilowatt-hour, some smaller-scale hydroelectric power plants only contribute 0.01 to 0.03 pounds of carbon dioxide per kilowatt-hour.

These estimates are mostly considered in the use of materials needed to build the dam or the labor to construct them initially.

While not emission-free, power plants that rely on hydroelectric energy emit minor amounts of pollution compared to most other sources.

Glen Canyon Hydroelectric Facility

3. Efficient and Flexible

Hydroelectric power plants are built directly in the path of their resource. This efficiency minimizes the need to locate and transport the source of energy. Whereas, coal-powered plants have to mine for coal and then haul it to electrical plants before it even begins processing.

Hydroelectric power is also extremely flexible. With excess water continuously stored in the reservoir behind a dam (and continuously replenished through the water cycle), hydroelectric energy can be generated quickly and on short notice.

This plays into efficiency as well during peak-use hours or extreme weather events when the population may be using more electricity than normal.

Some dam systems even have the ability to re-use the water already pushed through turbines by recalling it through a pumped storage system. Pumped storage systems essentially reverse the flow of water through the turbines during low-demand hours to then use again when demand is high.

Other renewable energy sources, like solar and wind energy, are dependent on the consistency of their resources and can only store a specific amount of the energy generated into batteries for backup use. Any fluctuations in solar or wind energy can have a great impact on their energy output.

Hydroelectric energy is always available on-demand. This makes it a great energy source to use in conjunction with other forms of renewable energy.

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4. Consistently Reliable

The Mississippi River has been flowing for around 70 million years and most likely it will continue to do so long after we’re gone. It’s hard to find a more consistently reliable source of energy than a major river.

While the water resource for hydroelectric energy is reliable, so is the technology used in hydroelectric dams. The turbine systems are from the mid-1800s, though humans have been improving upon hydropower plants for millennia.

See Related: Important Pros and Cons of Wind Energy

A New Definition of Reliability

Today, energy reliability is taking on a life of its own. With intense weather events, supply-chain challenges, and different lifestyles continuing to unfold, many homeowners are searching for renewable energy options when it comes to reliable electricity.

Odds are, if you have a flowing source of water on land that you own, you can install a microhydropower system. These systems produce electricity in generally the same way that a dam does but on a significantly smaller scale.

Micro Hydro Turbine
Microhydroelectric System. Source, Janesville Home & Solar

Microhydropower systems can be set up within moving water on your property and utilize a turbine-to-generator system. They are so small that they can be placed in the river or stream without affecting its flow with a dam and no reservoir is needed. The environmental impact is extremely low with microhydropower.

These systems are also affordable. While the cost is determined by the site and requirements of your home, the initial cost is typically between $2,000 to $6,000 U.S. dollars.

Microhydropower systems require little maintenance, zero operation fees (if you’re maintaining the system yourself), and last 20-30 years.

If you’re seriously interested in one of these systems, do your research and make sure to adhere to your local governmental guidelines. Most likely a permit is required to install this system.

See Related: How to Make a Mobile Home More Energy Efficient

5. Economically Beneficial

While there’s a lot of political talk regarding the economic impacts brought on by redistributing the ways that energy is produced, there are some straight facts I can give you.

Across the world, about two-thirds of the economically feasible potential area for hydropower to be implemented is still available. Globally, hydropower accounts for 17% of electricity production.

Hydroelectric plants are also affordable and cost-effective over their lifespan. While requiring a large investment upfront, these plants require minimal funds for maintenance and upkeep and are more affordable to the consumer as well.

Several states on the west coast of the U.S. rely mostly on hydroelectric plants for energy and their citizens pay less in energy bills than the rest of the U.S. as a result.

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It’s Not Always About the Money

Dam and other hydropower systems can not only produce electricity but can serve communities in many other ways as well.

From agricultural irrigation support to flood control to preventing erosion, these systems will become more important as humanity faces the increasing challenges of climate change.

6. Generate Electricity… For Fun?!

Hydroelectric plants and other dam systems can also create recreational opportunities. These include activities like fishing, swimming, and boating in the large reservoirs behind the dams.

The Grand Coulee Dam in Washington State is the largest generator of hydroelectric power in the United States. It also hosts plentiful outdoor recreation opportunities for its community and travelers and even has its own laser light show!

See Related: Important Pros and Cons of LED Lightings

5 Cons of Hydroelectric Power Plants

1. Location, Location, Location

The most limiting factor in creating a hydropower plant is the need for an on-site water resource. This severely impacts the viability of hydroelectric power for some regions of the world.

While placing a hydroelectric plant in a desert would obviously be inadvisable, some other locations full of water are equally unfunctional, such as wetlands. Wetlands, like those found in Florida, do not have a steady nor strong flow of water so the energy generated in these environments is extremely low.

A large, fast-moving body of water is pretty much required for today’s traditional hydroelectric plants.

2. High Initial Cost

The implementation of a hydroelectric plant typically includes the building of the dam, the turbine, generator, power house system, and the creation of a reservoir.

These can be extremely costly up-front and can be difficult to find investors due to the price tag.

Grand Coulee Dam
Grand Coulee Dam. Source, U.S. Bureau of Reclamation

In the case of the Grand Coulee Hydroelectric Facility mentioned previously, the initial dam system that was built in 1941 cost over $5 billion of today’s U.S. dollars. Then in 1975, an addition to the original facility was completed for just over $2 billion of today’s U.S. dollars.

It is important to note though, that after the initial cost, maintenance fees and operational costs are extremely low. Over its lifetime, a hydroelectric plant is typically more cost-effective than coal or nuclear-powered plants.

3. Negative Impact on Ecosystems and Habitats

The most concerning factor of hydroelectric power is the way it can negatively impact environments and the life within them.

These systems have been found to lower the oxygen levels in rivers and streams which directly impact the quality of life for fish that rely on oxygenated water to survive.

Reservoirs can become stagnant and retain excess sediment and nutrients that would typically flow downstream. These excess nutrients can become a breeding ground for algae which can, in turn, alter the original ecosystem.

The release of methane from decaying material can also be an environmental side effect of hydropower plants. As dead and rotting material gets trapped in unmoving reservoirs it begins to decompose out in the open and releases methane gas.

See Related: 4 Types of Water Pollution You Need to Know About

4. Human and Animal Displacement

When such a large project begins, the area it will take over needs to be cleared for construction first. This doesn’t mean just clearing some trees and brush, but can move entire communities from their homes and affect the behavioral adaptations that animals have made throughout their evolution.

In the case of species that migrate, like anadromous fish that live both in salt and fresh water, dams can prevent them from returning to spawning grounds and accessing rivers and streams they would normally return to.

The Ballard Locks Solution

The Ballard Locks in Seattle, one of the only lock and dam systems in the world that goes from freshwater to saltwater, utilizes a fish ladder to help salmon return from the ocean to their spawning grounds each year.

The fish ladder mimics a series of small waterfalls that the fish may encounter in natural streams. Salmon will persistently jump and swim their way up these waterfalls to reach the same stream bed they were born in.

Ballard Locks Fish Ladder
Ballard Locks Fish Ladder. Source, Encyclopedia of Puget Sound

While solutions to some problems have been found, like the Ballard Locks salmon ladder, environmentalists are still searching for solutions to problems dams create for other species.

See Related: 12 Animals That Have Become Extinct in the Last 100 Years

5. Vulnerable to Natural Disasters

While dams and reservoirs are made of solid enough materials to hold back a wall of water, they are vulnerable to natural disasters.

Droughts, like the ones experienced in the southern United States over recent years, are drastically impacting reservoir levels. The decrease in precipitation for these areas directly impacts hydropower plants’ abilities to produce energy.

Potentially disastrous geologic events are a serious factor in the stability of dams and reservoirs as well. Hydropower plants rely on gravity to move the water that generates electricity. This means that they are typically placed where there are altitudinal changes such as those found in mountain ranges. The risk of landslides or earthquakes increases in these areas.

If a natural disaster strikes and is able to damage a dam, severe consequences can result.

Your Next Power Source Could Be Renewable

Taking the benefits and detriments of hydroelectric power into consideration, the next generation of renewable hydroelectric energy is now up to you. It’s going micro!

The U.S. Department of Energy is encouraging the use of renewables and microhydropower systems. If you have a reliable source of flowing water on your property, consider going micro.

There are plenty of governmental and professional guides that will walk you through determining a potential site, your energy needs, and the costs of materials and installation while adhering to governmental requirements.

It’s also a great idea to combine a microhydropower system with another form of renewable energy. If you have solar panels or are looking to purchase some in the future, combining solar energy with hydropower could be an exceptionally reliable energy option.

So what are you waiting for? Your own reliable and renewable source of energy is waiting to be discovered!

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