What Are The 3 Main Sizes Of Hydropower Facilities?

Hydropower facilities generate electricity by harnessing the energy from flowing water. They typically utilize dams, reservoirs, turbines, and generators to produce renewable power. Hydropower facilities are traditionally categorized into three main sizes: small, medium, and large. Although definitions vary across sources, small facilities generally have an electricity generation capacity under 10 megawatts (MW), medium facilities range from 10 to 100 MW, and large facilities exceed 100 MW. Categorizing hydropower plants by size is important because it helps determine their economic viability, environmental impact, cost effectiveness, and best applications. The size influences factors like construction costs, transmission needs, technological components, and regulatory requirements. This content will provide an overview of the key attributes, advantages, and disadvantages associated with each size category of hydropower facilities.

Small Hydropower

Small hydropower facilities typically have a maximum capacity up to 10 megawatts (MW). According to the World Small Hydropower Development Report 2013, small hydropower is defined as having a capacity of up to 10 MW, however some countries set the limit as high as 30 MW. The generator units in small hydropower facilities generally have a capacity of 500 kW or less.

Small hydropower systems are often developed on small rivers or as small dams connected to a grid. They provide power for isolated communities or rural areas that are not connected to an electricity transmission grid. Small hydropower systems can also be integrated into existing dams, canals, pipelines, and other infrastructure to produce additional electricity. They are a popular source of renewable energy due to their low cost and minimal environmental impact compared to large hydropower projects.

According to the World Small Hydropower Development Report 2013, China, Japan, and the United States have among the largest small hydropower capacities globally. Small hydropower makes up nearly 20% of total installed hydropower capacity in China.

Medium Hydropower

Medium hydropower facilities are defined as having a generating capacity between 10-100 megawatts, according to the Department of Energy.

The typical capacity range for medium hydropower facilities is 30-100 MW. They utilize dams, reservoirs, penstocks and powerhouses to generate electricity, similar to large hydro facilities. However, medium hydropower has lower environmental impacts compared to large hydro.

Medium hydropower is commonly found throughout the world, often located along medium-sized rivers or as small dams connected to larger reservoirs. These facilities provide renewable power that can serve isolated communities or feed into the grid. Medium hydropower is a major source of renewable energy in many regions.

Large Hydropower

Large hydropower facilities typically have a capacity of more than 100 megawatts, with some facilities having capacities in the thousands of megawatts range (1, 2). According to the International Hydropower Association, large hydropower is defined as having a capacity of more than 10 megawatts (3).

These facilities generally utilize dams and reservoirs to store water and control its flow. The water held behind the dam flows through turbines embedded within the dam structure to generate electricity. Large hydropower stations provide the majority of hydroelectric power generated globally (1).

Large hydropower facilities are often built on major rivers and located in regions with high precipitation and natural changes in elevation. Some of the largest hydropower facilities in the world are located in China, Brazil, Canada, and the United States (4). These massive projects provide electricity to major population centers and industries.

While large facilities generate the most total electricity, they also have greater environmental impacts due to their scale. Careful planning is required to mitigate ecosystem disruption caused by flooding land and altering natural water flows (5).

Sources:

(1) https://www.energy.gov/eere/water/types-hydropower-plants

(2) https://en.wikipedia.org/wiki/Hydroelectricity

(3) https://www.hydropower.org/blog/large-medium-small-hydropower-what%E2%80%99s-the-difference

(4) https://www.iea.org/reports/key-world-energy-statistics-2021/hydropower

(5) https://sswm.info/ar/water-nutrient-cycle/water-use/hardwares/water-energy/hydropower-%28large-scale%29

Environmental Considerations

Small hydropower facilities typically have a lower environmental impact than medium or large facilities. Small facilities with a capacity under 10 megawatts often utilize existing dams or infrastructure, minimizing new environmental disruption (1). However, they can still impact local wildlife and ecosystems through barriers to fish migration, changes in water flow, and reduced oxygen levels (2). Strategic placement, fish ladders, and minimum flow standards can help mitigate damage.

Medium hydropower facilities have a larger footprint, requiring dams and greater infrastructure buildout. Flooding land for reservoirs displaces communities and destroys forests, wildlife habitats, and agricultural land (3). Maintaining minimum flows, implementing fish passages, and restoring surrounding habitats can lessen environmental harm.

Large hydropower projects convert enormous areas into reservoirs, submerging critical ecosystems and habitats. They disrupt river connectivity on a landscape scale, while dams obstruct sediment and nutrient flows. However, large projects allow economies of scale for impact mitigation through comprehensive environmental management plans, fish hatcheries, and wildlife reserves (2).

(1) https://www.sciencedirect.com/science/article/pii/036054429290116H

(2) https://www.eia.gov/energyexplained/hydropower/hydropower-and-the-environment.php

(3) https://www.ucsusa.org/resources/environmental-impacts-hydroelectric-power

Economic Factors

The capital and operating costs of hydropower plants vary significantly depending on the size and scale of the project. Here’s a look at some of the key economic considerations for each facility size:

Small Hydropower

Small hydropower plants, generally defined as 1-10 MW, have relatively low capital costs compared to larger facilities. Capital costs for small plants typically range from $1,000-$4,000 per kW installed. Operating costs are also low, estimated at $10-$30 per MWh.

The cost effectiveness of small hydro depends greatly on the site characteristics. Projects that utilize existing infrastructure like dams or water conveyance often have the lowest costs per kW installed.

Medium Hydropower

Medium hydropower, in the 10-100 MW range, requires greater upfront capital investment ranging from $2,000-$4,000 per kW. Operating costs increase to around $20-$40 per MWh.

Medium projects can achieve economies of scale over small hydro, making them an attractive option for many developers. The most cost effective medium facilities utilize existing infrastructure or have high hydraulic heads.

Large Hydropower

Large hydro plants over 100 MW have the highest capital costs, from $2,000-$8,000 per kW installed. Operating costs also rise, averaging around $30-$70 per MWh.

While large hydro requires substantial investment, the economies of scale often make this a cost competitive source of renewable electricity. Large storage reservoirs also allow capture of seasonal precipitation patterns.

Technological Differences

The types of turbines used at hydropower facilities vary by size and design.¹ Small hydropower facilities typically use reaction turbines like Francis, propeller, or Kaplan turbines that operate efficiently under low head and high flow conditions. Medium hydropower often uses Francis and Kaplan reaction turbines as well. Large hydropower facilities generally utilize impulse turbines like Pelton wheels that are designed for high head and low flow operation.

Automation and control systems also differ based on facility size.² Smaller plants may have more manual operation, while medium and large hydropower stations employ extensive computerized monitoring, control, and automation. Large dams and reservoirs require sophisticated operation and coordination to manage water flows and energy production efficiently. Overall, larger hydropower installations have more advanced turbines, governors, instrumentation, and electrical equipment.

Distribution and Transmission

The distribution and transmission requirements differ for each size of hydropower facility. Small hydropower systems typically generate power for isolated, rural areas. The electricity is distributed via local low-voltage distribution lines to homes and businesses nearby. There is little to no connection with wider electrical grids.

Medium hydropower facilities generally distribute power locally as well, but excess generation can sometimes be transmitted to the regional grid. This requires stepping up the voltage using transformers and transmitting over higher voltage lines that connect with the grid. Careful grid integration is required.

Large hydropower dams produce massive amounts of electricity that is almost always connected to the national grid or even across regions. The voltage needs to be stepped up to hundreds of thousands of volts for efficient long-distance transmission over high voltage lines. The scale requires complex transmission networks and integration with grid operators across large areas.

Global Trends

The global installed hydropower capacity reached approximately 1397 gigawatts in 2021, with over 50% coming from large facilities. According to Statista, the cumulative global hydropower capacity has been steadily increasing, growing from 1260 gigawatts in 2018 to the current 1397 gigawatts. China leads the world with over 352 gigawatts of installed capacity.

Looking forward, the International Energy Agency (IEA) forecasts continued growth in hydropower capacity globally, with almost all net additions coming from large facilities. The IEA projects over 230 gigawatts of new large hydropower capacity will be added between 2021-2030. Their analysis shows the average size of new hydropower projects is also increasing, pointing to a focus on large facilities to meet rising electricity demand.

Conclusion

In summary, there are distinct differences between small, medium, and large hydropower facilities based on their generating capacity and dam height. While small facilities generally produce up to 10 MW and have dams less than 10 meters tall, medium facilities generate between 10-100 MW with dams 10-20 meters tall. Large facilities are the biggest, producing over 100 MW with dam heights over 20 meters.

Categorizing hydropower by size is important for infrastructure development and investment. Small facilities have the least environmental impact but also more limited electricity generation. Large dams provide abundant power but require huge upfront investments and carry greater ecological risks. Medium facilities offer a balance, generating meaningful electricity output while mitigating negative impacts. Understanding these size classifications helps countries plan and build an optimal hydropower infrastructure to meet their needs.