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Is hydropower renewable and why? Yes – but it’s complicated. I learned this the hard way back when I worked at a salmon habitat conservation nonprofit.
We discovered the hydropower dam upstream led to lower fish populations migrating back to spawn. I realized those renewable energy electrons came at an environmental cost.
It taught me that renewability depends on more than fuel supply. I began researching hydropower more deeply to understand this tension between clean energy production and ecosystem impacts.
I soon realized the story holds far more nuance. The good news is solutions exist to expand hydropower responsibly while safeguarding river health.
Throughout this article, I’ll share key impact considerations, mitigation strategies, and innovations pushing hydro’s renewable future.
Is Hydropower Renewable And Why
Most sources point to three core features that characterize renewable energy:
- Derived from natural processes that are constantly replenished
- Not finite in availability or depleted over time through use
- Cause minimal harm to the environment
Hydropower offers some advantages on the first two points – the water cycle endlessly circulates between the air, land, and sea thanks to solar energy.
And flowing rivers provide an immense resource capable of meeting a significant portion of electricity demand indefinitely.
Table 1: Contribution of Hydropower as a % of Total Electricity Generation (Data Source: US Energy Information Administration)
| Country | % of Total Generation |
|---|---|
| Brazil | 61% |
| Canada | 59% |
| Switzerland | 54% |
| Austria | 58% |
| USA | 6.5% |
However, hydropower comes under scrutiny regarding environmental impacts and overall sustainability. Damming rivers fundamentally alters local ecosystems, potentially harming animals, habitats, water quality, and more.
These trade-offs call into question whether hydropower should enjoy the “renewable energy” label to the same degree as wind or solar.
When accounting for these complexities, assessing hydropower’s renewability becomes less straightforward. Some key considerations in this debate include:
- Resource lifespan – while water resources renew through the natural water cycle, individual hydropower facilities face buildup of sedimentation behind dams over decades, requiring dredging and occasional decommissioning.
- Methane emissions – organic plant matter decaying underwater in reservoirs produces methane, a potent greenhouse gas. The scale of these emissions varies across facilities.
- Downstream river impacts – fish migration pathways, access to habitat, sediment flows, and natural flood cycles can be disrupted by major hydropower dams.
We’ll dig deeper into both the pros and cons later on. First, let’s unravel what sets hydropower technology apart from other renewable energy sources.
The Mechanics Behind Hydroelectric Power
Hydropower leverages basic principles of physics and engineering. The key operating components include:
- Turbines – spinning turbines are powered by moving water which triggers an internal copper wire coil rotation inside electric generators. This motion between magnetic fields produces an electric current.
- Generators – convert the mechanical rotation energy into electrical energy. Modern hydro generators achieve efficiencies between 90-95%.
- Dams and reservoirs – provide height and storage volume to manage water pressure and flows. Gravity causes water to fall towards lower elevations, enabling capture of kinetic energy.
Not all facilities look alike however. Beyond massive concrete dams like Hoover and Three Gorges, there are a variety of hydropower plant types and components tailored to different landscapes and water conditions.
Common arrangements include:
- Reservoir – Created by damming rivers to store water and control flow. Often paired with multi-megawatt electricity output.
- Diversion – Channels portion of river flows into above-ground pipes and turbine systems.
- Pumped storage – Stores energy by pumping water uphill into a reservoir then releasing it to generate power on demand. Enables renewable load balancing.
- Run-of-river – Minimal dams and reservoirs resulting in lower environmental impact. Common with small hydropower projects under 25 MW.
No heat is generated in converting water movement to electricity, giving hydropower generation an efficiency edge over even the best combined-cycle natural gas power plants.
Another standout benefit lies in utility-scale energy storage thanks to pumped hydropower technology and reservoir capacities.
This flexible storage provides a unique advantage for renewable energy integration and resilient grid management. When wind or solar output ramps up and down, hydropower can ramp up and down accordingly in a complementary manner.
The Benefits of Hydropower as a Renewable
Of all renewable energy sources currently available, hydropower offers some of the most attractive qualities:
Reliable Source of Baseload Electricity
The consistent, seasonal nature of river flows allows hydropower to operate as a reliable baseload energy supply not dependent on short-term weather fluctuations.
In contrast, solar and wind generation must be balanced alongside other energy sources due to intermittency issues. Hydropower carved out a 16.6% share of renewable electricity generation worldwide as of 2020.
With abundant resources still untapped in regions like Southeast Asia, Central Africa, and Latin America, hydroelectricity output is projected to grow substantially in the coming decades.
Lower Greenhouse Gas Emissions Compared to Fossil Fuels
Per unit of electricity generated, even when factoring in reservoir-based methane emissions, hydropower compares very favorably to fossil fuels in lifecycle assessments for carbon emissions.
One literature review across numerous case studies found an average lifecycle carbon footprint of hydroelectricity ranging from 1% to 34% of natural gas per kWh, and 1% to 25% of coal’s emission levels.
And unlike solar, wind, nuclear, and fossil fuel power plants, zero particulate matter pollution enters the air during hydroelectric generation. This helps maintain cleaner air quality for communities located close to facilities.
Essential Grid Balancing Services
Beyond electricity production, hydropower delivers crucial grid reliability and balancing services enabling higher renewable energy penetration in many regions across the globe.
Pumped storage hydropower (PSH) provides large-scale energy storage by shifting excess renewable generation to meet peak demand later on.
This capacity is fast-ramping and more cost effective compared to alternatives like lithium-ion batteries at the present time.
As of March 2022, just 46 PSH plants were operating in the U.S., providing 22 GW of storage capacity. But over 50 GW of additional potential exists according to one NGO estimate.
Encouraging development of untapped PSH resources and modernizing existing hydropower assets will bolster resilience against blackouts as older coal generation goes offline.
The Drawbacks and Sustainability Challenges Facing Hydropower
Despite noteworthy advantages around flexible energy storage and low emissions, hydropower does face substantive critiques regarding renewability and environmental impacts stemming from:
Methane Production in Reservoirs
The World Commission on Dams flagged methane emissions from reservoir surfaces as a major sustainability issue back in 2000.
Organic matter like trees, vegetation, and carbon-rich soils becoming submerged undergoes anaerobic decomposition. This process converts a portion of the organic carbon into methane gas which bubbles up through the reservoir.
Researchers have worked on quantifying reservoir methane emission rates through field studies, remote sensing, and modeling tools.
Estimates vary widely – from ranges as low as 1% to as high as 30% the lifecycle carbon intensity relative to natural gas power plants.
Tropical reservoirs located in heavily forested regions tend to sit at the higher end. But a recent study synthesizing over 200 reservoir emission estimates globally found an overall average of 0.25% compared to a coal plant per unit energy generated.
Clearly not all reservoirs share an equal propensity for eutrophication and methane production. When developed carefully by clearing vegetation in advance, minimizing water level fluctuations, and considering geography, hydropower methane impacts can be avoided or mitigated.
Downstream Impacts on River Ecosystems
Hydropower dams pose an assortment of interrelated risks for downstream habitats and biodiversity stemming from various factors:
Sediment Transport Interruption
- Suspended sediment critical for maintaining deltas and wetlands becomes trapped behind dams rather than nourishing floodplain ecosystems.
Altered Flow Regimes
- Natural seasonal flood pulses are disrupted by flow regulation for electricity production. Rapid fluctuations in discharge levels stress local species.
Fragmented Connectivity
- Dams obstruct migration routes for fish to access essential spawning habitat. Altered thermal stratification in reservoirs also changes oxygen levels, water chemistry parameters, and habitat availability.
Table 2 summarizes common environmental considerations with hydropower based on facility design:
| System Type | Key Considerations | Potential Mitigations |
|---|---|---|
| Storage dams | Sedimentation loss, methane emissions, flow disruption | Selective withdrawal systems, fish ladders |
| Run-of-river | More modest reservoirs, occasional flow fluctuations | Minimum flow standards, sediment bypass |
| Diversion | Fish entrainment risk, low flow zones created | Fine-mesh screens, auxiliary water channels |
Well-planned mitigation measures like fish ladders, sediment bypass tunnels, and minimum environmental flows can minimize risks if properly implemented.
But finding the right balance between energy production and ecosystem conservation presents complex trade-offs not faced by other renewable generation sources to the same degree.
Improving Hydropower’s Renewable Credentials
Evaluating hydropower’s renewability requires considering an array of factors – resource availability, emissions, and environmental compatibility. How does it compare when stacked against benchmarks like solar, wind, geothermal and ocean power?
Comparing Lifecycle Impacts to Other Renewables
Each technology carries a unique signature of regional limitations, grid services provided, policies needed, and potential community impacts balancing out the carbon and ecosystem benefits.
Recent lifecycle analyses help benchmark emissions and sustainability metrics against alternatives. One extensive European study found hydropower had the lowest overall impacts based on 14 midpoint impact categories. Solar PV ranked second lowest, followed by wind and geothermal.
But drilling down into specific impact categories tells a more nuanced story:
- All renewables represent a major improvement over fossil fuels for carbon emissions and air quality. However coal and natural gas set a low bar.
- Solar and wind show virtually no threat to water consumption or quality concerns aside from facility maintenance.
- Meanwhile hydropower faces substantially higher potential consequences across habitat quality, ecotoxicity, eutrophication, and fish health endpoints.
Adoption of formal sustainability protocols like the Hydropower Sustainability Tools Network (HSTN) developed through multi-stakeholder engagement signal promising steps to evaluate and mitigate adverse effects.
Implementing Mitigation Measures and Best Practices
Transparent assessments of socio-environmental impacts and experience sharing around constructive solutions allows the hydropower sector to incrementally improve safeguards and accountability.
But policy levers also hold responsibility for steering best practices. Renewable portfolio standards could reward facilities achieving certification under sustainability frameworks.
And market rules enabling aggregated distributed and pumped hydropower resources would unlock flexible storage capacities to balance rising solar and wind generation shares.
Getting these policies and incentives right can nurture progress through sharing best practices rather than resisting change.
The Current and Future Role of Hydropower on the Grid
Hydropower carved out a critical role energizing modern civilization over the past century. With abundant untapped resource potential still remaining, it is primed to continue serving as a workhorse of renewable electricity, energy storage and climate resilience.
Compatibility and Synergies with Intermittent Renewables
As solar and wind generation expand rapidly, hydropower’s flexibility and storage capabilities enable mitigating intermittency issues through a complementary relationship:
- Wind and solar output fluctuates over sub-daily cycles following weather patterns. Hydropower can ramp up and down through turbine adjustments and reservoir storage.
- Extended multi-day wind and solar lulls also occur over seasonal cloudy & low wind periods. Hydropower reliability shines by bridging through these crunches.
- Pumped storage hydropower provides immense batteries enabling daily and weekly storage shifting supply to meet peak demand.
These synergies translate to real world cases already. Hydro capacity across the Western U.S. frequently ramps to absorb temporary oversupplies from regional wind farms.
Quebec’s substantial hydro assets enable balancing cheap renewable imports from neighboring Ontario and New York. And in Europe pumped storage plants continue serving crucial storage needs as solar and wind expand.
Providing Large-Scale Energy Storage
Only pumped hydropower storage (PHS) currently offers gigawatt-scale storage able to meet weekly or seasonal shifting needs at a affordable costs compared to alternatives.
As a reference point, the Bath County Pumped Storage Station in Virginia boasts a massive 24 GWh storage capacity. For context, this tops the largest lithium-ion battery storage facilities today by a factor of over 250x on an energy capacity basis.
While battery costs continue falling, pumped hydropower maintains strong cost efficiency advantages for large capacity storage requirements.
Growing PHS alongside battery buildout affords synergies across a diverse portfolio of storage assets – each with respective niche capabilities spanning short-duration services to week or month-long backup needs.
Enabling Greater Grid Resilience and Responsiveness
The services discussed above translate directly to keeping our grids running smoothly as coal plants retire and get replaced by renewables in turn.
By absorbing temporary loses of wind or solar inputs, hydropower mitigates risk of shortfalls triggering cascading failures.
And on the other side of the coin, pumped storage enables capturing excess renewable generation that would otherwise get curtailed.
This empowers optimal asset utilization. Growing electrification across the transportation, buildings, and industrial sector will only elevate demands for a robust, resilient electricity system.
FAQs
What Is Renewable Hydropower?
Renewable hydropower refers to generating electricity by harnessing the natural water cycle—the power of river flows, tides, or waves—without consuming resources in the process.
Hydropower comes from water, which is constantly renewed through Earth’s water cycle driven by solar energy. Rivers and watersheds offer a steady long-term energy resource compatible with renewable attributes, although not without trade-offs.
Is Hydropower The World’s Largest Source Of Renewable Energy?
As of 2021, hydropower accounts for over 1600 gigawatts (59%) of installed renewable electricity capacity worldwide according to the International Hydropower Association.
This amounts to 16.6% of total electricity generation globally. While most industrialized regions have tapped into much of their hydro potential already, areas such as Africa, Asia, and Latin America offer abundant untapped technical capacity still to develop.
Why Is Water A Good Renewable Energy Source?
Unlike fossil fuels extracted from finite underground reservoirs, or fissile materials like uranium, the water cycle endlessly circulates clean water powered by solar radiation.
Rainfall and snowmelt feed watersheds and rivers at a rate replenished through evaporation and precipitation. Water’s unique thermal properties enable harnessing kinetic energy for mechanical power extremely efficiently at ~90% conversion rates, thanks to fundamental laws underpinning hydropower systems.
What Are 5 Disadvantages Of Hydropower?
While offering advantages like flexibility, storage capacity and low operating costs, hydropower does carry notable drawbacks regarding sustainability:
- Fragmentation of river habitats and fish migration routes from dams
- Methane emissions from reservoirs due to vegetation decomposition
- Sediment retention altering downstream river function
- Local wildlife and vegetation losses from flooding
- Occasional seismic activity induced by large impoundment reservoirs
What Is The Most Renewable Power Source?
Based on scalability, resource abundance and replenishment factors, solar PV and on-shore wind likely represent the most renewable major electricity sources harnessed currently.
However, no silver bullet options exist without balances among cost, reliability and environmental attributes. Ultimately investing across a diverse portfolio of complementing renewable technologies, including responsible hydropower, supports resilient decarbonization.
Who Invented Hydropower?
Hydropower technology traces back over 2000 years to ancient Roman times with concepts like the water wheel for mechanical tasks like milling grain.
Transforming kinetic energy into usable electricity came centuries later, pioneered by figures such as Michael Faraday studying electromagnetism by 1832.
Industry visionaries like Lucien Smith, Lester Pelton and Thomas Edison refined turbine designs enabling the first hydroelectric plants in the 1880s.
Why Is It Called Hydropower?
The term hydropower directly stems from Ancient Greek roots – “hydro” meaning water, and “power” referring to energy or force.
So linguistically, hydropower translates simply to “water-powered energy”, an apt literal description of using falling or flowing water bodies to generate electricity through turbine systems.
What Is The Oldest Form Of Hydropower?
The water wheel constitutes the oldest application of hydropower, dating back over 2000 years to Roman times based on archaeological evidence, with uses spanning agricultural needs like milling grain.
Water wheels later evolved transforming kinetic energy for activities like sawmilling, textile weaving, and blacksmithing tools up through the 19th century before electricity generation methods emerged.
What Is An Example Of Hydropower?
Any application leveraging the power of flowing water qualifies as hydropower in a general sense. This ranges from old-fashioned water wheels to modern electricity generation dams harnessing kinetic energy via turbine systems.
Prominent examples include the massive Three Gorges Dam across the Yangtze River in China, currently the world’s largest hydroelectric power station with 22,500 MW of installed capacity.
Is A Sun A Renewable Resource?
While our Sun and solar energy reaching Earth may be effectively limitless from a human timescale perspective, solar radiation arises from thermonuclear fusion processes within the Sun that will deplete available hydrogen fuel over billions of years.
So while solar energy is renewable in a functional timeframe relative to humans, from a physics standpoint solar resource availability does face very long-term constraints, albeit on timescales far exceeding human civilization scales.
This contrasts renewable examples like hydropower fueled indefinitely by Earth’s solar-powered water cycle.
Which Country Has The Most Hydropower Plants?
China stands as the global leader in total installed hydropower capacity, thanks in part to massive projects like the Three Gorges Dam powering its rapid development through recent decades.
As of early 2022, China operates over half of the ~2300 GW of hydroelectricity capacity installed worldwide. Still experts estimate only roughly 25% of China’s total technical hydropower potential has been tapped into so far across its extensive river networks and mountainous topography.
Conclusion and Verdict: Is Hydropower Truly Renewable?
Hydropower demonstrates unique advantages complementing emerging solar and wind technologies thanks to reliability, storage capacity, and climate resilience attributes.
Global hydroelectricity output is positioned for continued expansion playing an integral role in decarbonization.
However, qualms around long-term resource sustainability and consequences imposed to river ecosystems tarnish some of hydropower’s renewable credentials compared to alternatives like solar and wind.
Only by acknowledging then constructively addressing downsides can the hydropower industry evolve responsibly – implementing increasingly standardized sustainability protocols and enabling policy environments that reward best practices. Tracing the nuanced qualitative impacts beyond strictly quantitative carbon accounting tells a fuller story.
On balance – yes, existing and emerging hydropower resources honestly deserve a partial seat at the renewable energy table when holistically weighing pros and cons.
But earning and maintaining this distinction as the 21st century unfolds requires proactive commitment to assessment, transparency, and continual improvement.
