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
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.
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
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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