Pros & Cons Of Hydro Energy (Hydroelectric & Hydropower)

Below, we list the potential pros and cons of hydro energy (also referred to as hydroelectricity, or hydropower).

This guide forms part of a series of guides we have put together outlining the benefits and disadvantages of different energy sources and energy generation methods

 

Summary – Pros & Cons Of Hydro Energy 

Firstly, What Is Hydro Energy?

We explain what hydro energy is in a separate guide.

We also outline the different types of hydro energy setups in another guide.

 

Some of the main pros and cons of hydro energy might be …

 

Potential Pros

Is Currently The Leading Energy Source Across Multiple Metrics

There’s Different Types Of Hydro Energy Setups

Different Sized Hydro Energy Set Ups Are Available

Hydropower Plants May Have A Good Lifespan Compared To Other Energy Sources

May Be A Renewable Energy Source In Some Instances

May Not Generate Greenhouse Gas Emissions, Or Air Pollutants Whilst In Operation

No Waste By-Products Whilst In Operation

May Provide A More Reliable (Consistent) Power Output Than Some Other Energy Sources

May Be Capable Of Providing Base Load Power

Can Be Flexible & Adjustable When In Use

No Refuelling Required, & Water Is Generally Free

May Be One Of The More Affordable/Cheaper Energy Sources (In Terms Of Supply Side Cost)

Some Studies Might Suggest That Hydropower Is One Of The Energy Sources That Is Key To A Future With Greater Renewable Energy Use 

Storage Hydro Specifically Might Be Able To Operate Independently Of Water Flow For A Period Of Time

Pumped Storage Hydro Specifically Might Be Complementary To Solar & Wind Power In Several Main Ways

Pumped Hydro Energy Storage Specifically Might Be Able To Start Up Quickly

Pumped Storage Hydro Specifically Might Be Capable Of ‘Storing’ Renewable Energy, & It Might Be A Lower Cost Storage Option Than Batteries

Pumped Storage Hydro Might Be Able To Use Renewable Energy For Pumping In The Future

Pumped Storage Hydro Might Have Potential For Growth In The Future

Hydroelectric Dams Specifically Might Offer Multiple Uses

Run Of River Hydro Specifically Doesn’t Use Up Land Space

 

Potential Cons

New Pumped Storage Hydro Sites Need To Meet Certain Criteria For Use

There Might Be A Limit On The Number Of Large Hydro Energy Plants That Can Be Built Globally

Some Hydro Plants Might Negatively Impact The Environment

Some Hydro Projects May Have A Negative Social Impact

Large Scale Hydroelectric Plants Can Be Costly To Construct

Natural Events, & Weather/Climate Can Impact Hydro Energy

Some Hydropower Plants Use Fossil Fuels

May Have Low Power Density

May Have A Lower Capacity Factor Than Several Other Energy Sources

May Be Less Reliable & Less Scalable Than Nuclear Specifically

 

General Summary

Hydropower is an energy that is reasonably well established worldwide

In fact, it is the leading renewable energy source worldwide across several metrics, with hydropower making up about half of all renewable energy installed capacity globally

This is one of the advantages it has over other key renewable energy sources like wind and solar

Additionally, it’s other potential advantages over wind and solar might be that it delivers more consistent power output (it isn’t variable), it might be more suitable for base load, some types of hydro energy like pumped storage hydro might have more controllable factors to their operation (compared to being subject to the sun and wind patterns), it has the ability to ‘store’ energy, along with a few other potential advantages

In the future though, hydropower might make a good complementary energy source to both solar and wind energy, that can be used in the same energy mix

One of the potential challenges for hydropower in the future might be expansion of new projects, and increasing installed capacity

 

*Note

The pros and cons in this guide are broad generalisations.

Each energy project in each geographic location will have it’s own factors and variables to consider, so, each one will require a separate assessment of it’s individual pros and cons.

The development of technology, as well as other factors might change pros and cons in the future too.

 

Potential Pros Of Hydro Energy

Is Currently The Leading Energy Source Across Multiple Metrics

Those metrics currently include:

 

– Worldwide, It Is The Leading Renewable Energy Source Of Electricity Supply & Consumption

Having a production and consumption share of about 50% compared to other renewable energy sources 

 

– Worldwide, It Is The Leading Energy Storage Source Worldwide

Pumped hydro accounts for 97 percent of energy storage worldwide (sciencealert.com)

 

– In Some Specific Countries, It Is The Leading Renewable Energy Source

China might be one example of a country where this is the case

 

From chinapower.csis.org:

Hydroelectric power has become China’s main source of renewable energy production [, and] China became the world leader in hydropower in 2014 

[Part of the reason behind this might have been that,] from 2000 to 2015, China increased its hydroelectric energy-generation capacity by … 408 percent

 

There’s Different Types Of Hydro Energy Setups

There’s three main types of hydro energy plants.

Each one might offer different benefits and have different capabilities.

They are:

– Hydroelectric dams (also called ‘Impoundment’)

Which release water from a dam through a generator

 

– Run of river (also called ‘Diversion’)

Which funnel water from a river

 

– Pumped storage hydro

Which have higher and lower water reservoirs where the water is pumped up and released down between the reservoirs

 

*There’s also setups that might combine some of the above options.

*There is also small scale hydro power setups that use devices like water wheels for example to generate energy on small streams and rivers near farms and in more remote areas. 

 

Different Sized Hydro Energy Set Ups Are Available

When we say ‘size’, we are referring to the energy generation capacity of the hydro energy set up.

There’s large hydro energy power plants (for utility use) on one end of the spectrum, and micro sized hydro energy setups on the other end.

Utility sized power plants can obviously generate electricity on much larger scales.

For example, chinapower.csis.org mentions that in China: ‘The … Three Gorges Dam … is the largest hydroelectric dam in the world … [and has] a generation capacity of 22,500 MW.’

Micro sized setups might be in the 10 to 30 megawatts range, and can be installed in small rivers or streams.

These micro setups might provide energy to a small group of people, or a property.

A few benefits of these micro setups might be that:

– They can be used remotely (where there is a suitable body of water)

– They might have minimal to no negative environmental effects, and may not impact aquatic life or fish migration

 

Hydropower Plants May Have A Good Lifespan Compared To Other Energy Sources

Various reports online indicate that hydroelectric and hydropower facilities might have an operating lifetime of anywhere from 40 years, all the way up to 100 years or more.

Some hydro facilities may exceed 100 years in lifespan with upgrades and updates, according to some reports.

Comparatively, other energy sources may have equipment or power generating facilities that aren’t anywhere near as long lasting:

The industry standard lifespan for a wind turbine might be 20 to 30 years

Some nuclear reactors might have a lifespan of around 40 years, and potentially up to 80 years

Coal plants might have a lifespan of anywhere from 30 to 46 years on average

 

One benefit of a longer operating lifetime might be saving on new construction costs.

 

May Be A Renewable Energy Source In Some Instances

Some hydro energy systems only rely on running water, or falling water (from a higher level to a lower one), to push/spin a turbine.

They don’t rely on other energy sources (like fossil fuels) to pump or push water.

Where this is the case, these hydro energy plants might be considered renewable

Renewable hydro energy sources essentially relies on Earth’s natural and continuous water cycle, which infinitely cycles between the different stages of the cycle i.e. it naturally recharges.

 

However, this may not be a legitimate benefit at this point in time.

irena.org indicated that (paraphrased) in 2016, electricity generation from hydro power was completely from mixed plant hydro, and 0 electricity came from renewable hydropower.

 

May Not Generate Greenhouse Gas Emissions, Or Air Pollutants Whilst In Operation

When other energy sources like fossil fuels aren’t used at hydro plants for activities like pumping water, hydro energy might emit little to no greenhouse gas emissions or air pollutants whilst in operation.

Per kWh generated in the US, hydro energy is one of the energy sources that has one of the lowest emission footprints.

 

No Waste By-Products Whilst In Operation

Unlike a coal power plant that has traditionally produced waste by-products like fly ash, hydro energy plants don’t produce a waste by-product during operation.

 

May Provide A More Reliable (& Consistent) Power Output Than Some Other Energy Sources

Hydropower is not a variable/intermittent energy source like solar energy or wind energy that relies on the sun or wind to capture energy and deliver power.

Instead, hydropower might deliver power more consistently (without large fluctuations)

This might make hydro energy more reliable as an energy source overall.

 

May Be Capable Of Providing Base Load Power

Typically, fossil fuels and nuclear plants can provide base load power.

But, several reports indicate that geothermal and hydro energy are currently the only two ‘renewable’ energy sources capable of delivering base load power.

 

[Storage hydro …] Can run consistently and provide baseload power … (hydropower.org)

 

[Pumped storage hydro …] Can provide both peak demand energy supply, and low demand energy supply (hydropower.org)

 

Can Be Flexible & Adjustable When In Use

Hydro power plants might be flexible and adjustable in several ways during their use.

For example, water flow can be adjusted, and this can change the output of electricity.

This might be helpful in periods of off peak demand, and low demand – water flow can be decreased, and this helps conserve water for periods when electricity demand or consumption is higher.

Pumped hydro storage specifically can be adapted to electricity demands at any one time, by pumping more or less water.

 

[Storage hydro …] can be shut down and turned on again for temporary power to meet peak load demands (hydropower.org)

 

No Refuelling Required, & Water Is Generally Free

Coal power plants and nuclear power plants generally have to be refuelled periodically.

Coal and uranium obviously both cost money as resources as well.

Hydro power plants on the other hand don’t require refuelling, and, the water they use is essentially free in comparison to fuel for other energy sources.

 

May Be One Of The More Affordable Energy Sources In Terms Of Supply Side Cost

When looking at the supply side cost of hydropower:

– One set of data suggests conventional hydropower has average capital costs

– Another set of data indicates that hydro energy has the cheapest LCOE (levelised cost of electricity) amongst all energy sources – even cheaper than solar and wind

 

Historically, hydropower has been the cheapest way to source renewable electricity (cnet.com)

 

Some Studies Might Suggest That Hydropower Is One Of The Energy Sources That Is Key To A Future With Greater Renewable Energy Use 

Some recent studies may suggest hydro energy could be one of the keys for a 100% renewable energy future.

Various studies that investigate what a 100% renewable energy future might look like for various countries and worldwide, identify pumped storage hydro energy as one of the three main renewable energy sources, along with solar and wind energy, that could form part of an energy mix to make this happen

 

Storage Hydro Specifically Might Be Able To Operate Independently Of Water Flow For A Period Of Time

[Storage hydro …] Can operate independently of an inflow of water for weeks and months (hydropower.org)

 

Pumped Storage Hydro Specifically Might Be Complementary To Solar & Wind Power In Several Main Ways

Solar and wind energy are both variables sources of energy.

Along with backup energy sources, solar and wind may both require battery energy storage.

Pumped storage hydro might not only be able to provide base load, but may be suitable for energy storage too.

 

[Pumped storage hydro has the advantage of providing energy storage and baseload power as a complement to solar and wind energy] (sciencealert.com)

 

Pumped Hydro Energy Storage Specifically Might Be Able To Start Up Quickly

Pumped-hydro energy storage can go from zero to full power extremely quickly – it takes only a few minutes (sciencealert.com)

 

This might make hydro energy valuable in a power grid with variable energy sources (like solar or wind energy) that need a backup energy source that has the ability to ramp up quickly to meet energy demand.

 

Pumped Storage Hydro Specifically Might Be Capable Of ‘Storing’ Renewable Energy, & It Might Be A Lower Cost Storage Option Than Batteries

Pumped storage hydropower may have the ability to store renewable energy.

It might do this by utilising surplus renewable energy (that otherwise would have been lost, or sent to battery storage) to pump water from it’s lower reservoir to the higher one.

The upper (higher) reservoir of water acts as an indirect storage of that surplus energy, as this water can be released in the future when renewable energy sources aren’t capturing and converting enough energy.

 

In terms of the cost of storing renewable energy via pumped storage hydro, it might be a cheaper option than using batteries for energy storage.

 

[Pumped storage hydro] … is the lowest cost large-scale energy-storage technology available (sciencealert.com)

 

Pumped Storage Hydro Might Be Able To Use Renewable Energy For Pumping In The Future

Separate to storing surplus renewable energy, pumped storage hydro might be able to use renewable energy directly in the future.

Currently, some pumped storage hydro plants use fossil fuels to pump water uphill.

Some plants might be able to substitute a % of fossil fuels for renewable energy at some point.

This may have the added benefit of making pumped storage hydro more sustainable and eco friendly.

Although, its worth mentioning that there would still be an environmental and resource footprint to make and dispose of solar panels.

 

… pumped hydropower could run with renewable energy like solar and wind power in the future – making it cleaner and more sustainable (energyinformative.org)

 

Pumped Storage Hydro Might Have Potential For Growth In The Future

Some studies have identified sites that might be suitable to set up pumped storage hydro energy projects on in the future (pending on-site feasibility checks)

 

From sciencealert.com:

… thousands of new [suitable] pumped hydro energy storage sites have been located worldwide [by new studies], and only a small % (around 1%) of these sites need to pass final approval factors in order to provide enough stored energy to power the world.

They can operate at maximum power for between 5 and 25 hours

 

Hydroelectric Dams Specifically Might Offer Multiple Uses

In addition to the power plants being used for electricity generation, hydroelectric dams might have other uses/functions, such as providing flood control, and potentially serving as irrigation systems.

So, they may have increased utility other than just power generation.

 

Run Of River Hydro Specifically Doesn’t Use Up Land Space

Run of river hydro plants don’t use land like some pumped storage hydro sites might, and like some other energy sources do.

It’s similar to offshore wind in this regard – it can make use of space in bodies of water.

 

Potential Cons Of Hydro Energy

New Pumped Storage Hydro Sites Need To Meet Certain Criteria For Use

Not all land is suitable for new pumped storage hydro projects

New sites for pumped storage hydro might generally first be identified by an algorithm (which analyses the land for space, suitable terrain, and the right variations in elevation)

After identification though, the site needs to meet certain requirements, and consider certain factors.

 

Some of the requirements that they might need to meet might be:

– Passing further on-site research

– Passing final approval tests 

 

sciencealert.com also mentions that the factors that might need to be considered for new sites might be:

… the ownership of the land, any specific engineering or environmental challenges they might present, availability of upper and lower reservoir locations, potential route for a connecting tunnel, whether the land is located in a national park or urban area, and potential capacity to store energy (which is usually in the 2-150 GWh of energy range) …

 

There Might Be A Limit On The Number Of Large Hydro Energy Plants That Can Be Built Globally

Aside from the challenge of finding suitable sites for new hydro projects in general, there might be issues specifically in building new large hydro energy power plants 

Two key reasons for this might be:

– There’s only a limited number of suitable reservoirs for projects of this scale

– Only some locations might be profitable to set up these projects in

 

Some places like the Grand Inga Dam in Africa for example have significant potential, but may face feasibility challenges like being overpriced, having funding issues or planning issues, and dealing with corruption.

 

Data from energyinformative.org may partially illustrate how these issues play out in reality:

As of 2014, there are currently about 30 major power plants that are expected to generate more than 2.000 MW under construction [and] Only one of these projects was started between 2012 and 2014

 

Some Hydro Plants Might Negatively Impact The Environment

For example, different types of hydro energy installed in different locations might result in:

– Damning of water (as opposed to natural movement of water)

– Changed water flows (at rivers and streams)

– Specifically impacting river or dam environments

– Changing/manipulating the water and the surrounding aquatic environment, which can result in degradation of habitats, or displace wildlife

– Turbine blades may be a hazard for some wildlife 

 

Large hydroelectric dams, and major water diversions in particular may affect aquatic life like fish directly, or indirectly by altering the water environment they live in, and the ecosystems they depend on.

 

Some Hydro Projects May Have A Negative Social Impact

Like for example disrupting, or even displacing some local communities that live by water sources that hydro projects are installed on.

 

Large Scale Hydroelectric Plants Can Be Costly To Construct

Some large hydroelectric power plants can cost in the billions of dollars.

 

From chinapower.csis.org:

[In China, the …] Three Gorges Dam [was] completed in 2012 at a cost of over $37 billion [. This is …] the largest hydroelectric dam in the world …

 

Natural Events, & Weather/Climate Can Impact Hydro Energy

Hydro energy relies on water to generate power.

It makes sense then that some natural events, as well as the weather/climate can impact hydro energy’s ability to generate power.

Droughts, rainfall, and generally being in a water scarce location might all impact hydro energy.

 

Some Hydropower Plants Use Fossil Fuels

Some hydropower plants don’t rely on naturally running water, or non pumped water.

Pumped storage hydro for example needs to pump water between reservoirs instead – usually up an elevation, or a hill.

Some of these plants use fossil fuels as the energy source for pumping. 

Where this is the case, the hydropower plant is no longer a true renewable energy source, as it relies on non renewable energy (in the form of fossil fuels) to function.

Some other flow on effects to the use of fossil fuels might be:

– Greenhouse gas emissions

– Release of air pollutants

 

May Have Low Power Density

Hydro power may have one of the lowest power densities amongst different energy sources, with natural gas and nuclear having the highest power densities

 

May Have A Lower Capacity Factor Than Several Other Energy Sources

One set of data shows that although hydro energy doesn’t have the lowest capacity factor amongst different energy sources, it’s capacity factor is much lower than both nuclear and geothermal energy.

 

May Be Less Reliable & Less Scalable Than Nuclear Specifically

… hydroelectricity is far less reliable and scalable than nuclear (forbes.com)

 

 

Sources

1. https://en.wikipedia.org/wiki/Hydroelectricity

2. http://energyinformative.org/hydroelectric-energy-pros-and-cons/

3. http://efficientgreenpower.com/hydroelectric-energy

4. https://www.renewableresourcescoalition.org/alternative-energy-sources/

5. https://water.usgs.gov/edu/hydroadvantages.html

6. https://chinapower.csis.org/energy-footprint/

7. https://www.bettermeetsreality.com/the-different-types-of-renewable-energy-sources-with-examples/

8. https://www.bettermeetsreality.com/installed-capacity-production-consumption-of-renewable-energy-worldwide-by-country-by-source/

9. https://www.sciencealert.com/scientists-spot-530-000-potential-pumped-hydro-sites-to-meet-all-our-renewable-energy-needs

10. https://www.cnet.com/news/if-renewable-energy-can-power-entire-countries-why-isnt-everyone-doing-it/

11. https://www.forbes.com/sites/jeffmcmahon/2018/10/01/3-reasons-nuclear-reactors-are-more-expensive-in-the-west-hint-its-not-regulation/#1237136f5d1a

12. https://www.forbes.com/sites/michaelshellenberger/2018/05/08/we-dont-need-solar-and-wind-to-save-the-climate-and-its-a-good-thing-too/#6c6732fae4de

13. https://arena.gov.au/renewable-energy/pumped-hydro-energy-storage/

14. https://www.hydropower.org/types-of-hydropower

15. https://www.irena.org/hydropower

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