Hydropower: A Comprehensive Review, by Brett Bergen

From Brettipedia, the free humanocyclopedia

Source: http://www.eia.doe.gov/oiaf/ieo/highlights.html



Hydropower refers to the power captured from the water as it moves from potential to kinetic energy, the process of which is driven by gravity (Department of Energy, 2008; Hiserodt, 2007). Hydropower is just one of a variety of renewable energy resources available today, and power generated from large-scale hydropower is the most far-reaching out of any renewable resource in the world today. Yet, even though hydropower is a renewable energy, it appears to have considerable constraints in its potential to expand its reach further, and it come with a multiplicity of costs and benefits in light of economic, environmental, and social considerations. Due to its considerable reach, its rapid expansion within developing nations, and the significance of the costs and benefits that surround it, hydropower is an important topic of study as it relates to the energy needs of modern societies.

My purpose is to conduct a comprehensive investigation into hydropower, beginning with a review of what led to the development of the modern hydropower industry, and then an assessment of its future role in the world’s energy market. This will set the stage for an analysis of the cost-benefit trade-offs between hydropower’s economic, environmental, and social aspects. It may also bode well to develop recommendations from this analysis for the benefit of stakeholders considering hydropower projects. Finally, new technologies will be evaluated that show promise in mitigating some costs of traditional hydropower, while maintaining many of its benefits.



  1. What Is the Origin of Hydropower?
  2. The Processes behind Hydropower Today
  3. World Energy Consumption
  4. Hydropower Costs & Benefits: Overview
  5. Economic Costs & Benefits
  6. Environmental Costs & Benefits
  7. Social Costs & Benefits
  8. New Hydropower Technology
  9. Conclusion

Literature Review

What Is the Origin of Hydropower?

The story of hydropower begins with the waterwheel, which the Oxford English Dictionary describes plainly as “a large wheel driven by flowing water” (AskOxford.com). There is uncertainty as to the date of the first water wheel, but T. S. Reynolds cites British scholar Joseph Needham as finding evidence in ancient Indian texts of waterwheels from 350 B.C.E. (Reynolds, p.14, 1983). However, there is question as to the soundness of this evidence, due to possible interpretation errors from reading the ancient scriptures. Instead, scholars turn to next piece of historical evidence, which comes from ancient manuscripts by Philo the Greek, a technician who lived under the Byzantine Empire around the 3rd century B.C.E. (Reynolds, p.14, 1983). It is believed that the Greeks used waterwheels to grind wheat into flour at this time (Department of Energy, 2008).

Waterwheels eventually found their way into the Middle East by the 10th century C.E., as well as late medieval and Renaissance Europe (Smil, p.79, 2006). Even by the time of the Western Industrialization, power from waterwheels was relied upon as much as the steam engine (Smil, p.80, 2006). During the time of the Western Industrialization pre-1800s, there existed only wooden waterwheels that suffered from low efficiencies and maintenance problems (Smil, p.82, 2006). After the 1800s, however, the metal waterwheels by Benoit Fourneyron, and then Samuel B. Howd – which was later improved upon by James B. Francis, led to the development of the water turbine. Water turbines were originally directly connected to industrial plants, but later used to generate electricity (Smil, p.82, 2006). Today, the world’s hydroelectric plants are primarily powered by water turbines that capture the energy in water flowing through a dam (Department of Energy, 2008).

The Processes behind Hydropower Today

The U.S. Geological Survey explains that the source of hydropower is mechanical energy. Today, most hydropower comes from a dam that is constructed to create a reservoir of water, and water turbines are built within the dam below the water’s surface. The turbines are driven by the force of the water flowing through them, which, from the subsequent spinning of electromagnets. The rotation of the electromagnets generates a current in stationary wire coils, which runs through a transformer (so to increase the voltage) to be distributed over power lines to consumers (U.S. Geological Survey, 2006). (See Figure 3 below)

The water that fuels the power of hydroelectric plants is subject to the natural process of the water cycle. Put simply by the U.S. Department of Energy, “the sun draws moisture up from the oceans and rivers, and the moisture then condenses into clouds in the atmosphere. The moisture falls as rain or snow, replenishing the oceans and rivers. Gravity drives the water, moving it from high ground to low ground” (Department of Energy, 2008). (See Figure 4)
The ability of the hydroelectric plant to generate power is determined by the mechanical energy of the water, the flow of the river, and the efficiency of the dam, which can be simplified by the following equation: Power = (Height of Dam) x (River Flow) x (Efficiency). River flows vary and dam heights vary widely, but dam efficiencies tend to range from 60% to 90%, depending on how well hydroelectric facilities are maintained.

A plant’s hydroelectric energy from can be calculated by multiplying its output in units power, by units of time: Power x Time = Energy. To figure out how many consumers’ energy needs can be served, one may simple divide the energy output from the plant by the average energy consumption of the hydroelectric plant’s customer: (Plant Energy Output) / (Energy Consumption per Consumer) (Wisconsin Valley Improvement Company, 2006).


Figure 3
Source: http://www.eia.doe.gov/oiaf/ieo/highlights.html
Figure 4
figure 4
Source: http://www.eren.doe.gov/RE/hydropower.html



World Energy Consumption

The BP Statistical Review of World Energy (June, 2006) details the breakdown of energy fuel consumption as a percentage of the world’s energy for 2005 data. The report reveals that approximately 88% of the world’s energy consumption is from fossil fuels, with 36% from oil, 28% from goal, and 24% from natural gas. Approximately 12% of the world’s energy consumption is renewable (www.bp.com) (See Figure 5). If nuclear energy is taken out of the equation, large and small scale hydro consist of 58% and 5% of the world’s renewable energy resources, respectively (www.bp.com) (See Figure 6).
According to the projections of the U.S. Energy Information Administration’s 2007 International Energy Outlook, the world energy’s consumption will increase by 57% between 2004 and 2030. Breaking this down, the energy demand from the thirty-one countries in the Organization for Economic Cooperation and Development (OECD) is set to increase by 24%, and the energy demand by non-OECD countries is set to increase by 95% (See Figure 1). While a majority of this projected increase in energy consumption will rely upon fossil fuels, energy from renewables connected to energy grids are expected to increase by only 1.9% per year, and remain a considerably smaller percentage of the world’s total energy consumption (from 7% in 2004, to 8.0% in 2030) (See Figure 2 below). Mid- to Large-scale hydroelectric plants are expected to make up the highest proportion of renewable energy growth, and will be located outside of OECD countries, particularly in Asia and Latin America. Renewable energy growth in OECD countries, with the exception of Canada and Turkey, is projected to come primarily from non-hydroelectric renewable resources.

Hydropower from large dams is estimated to contribute to 19% of world’s total electricity supply (as opposed to total energy supply). Approximately one-third of the world depends on hydropower for over half of their electricity, and 24 of those countries rely on hydropower to supply nearly 90% of their total electricity supply (www.dams.org). The percentage of electricity from hydroelectricity is expects to fall to 16% by 2030, however, as coal and natural gas consumption grows at a much faster rate than hydropower and renewables (U.S. Government, 2007).

The reason why such little growth is projected for hydropower as a proportion of the earth’s energy resources is due to the exhaustion of such of the developed world’s hydroelectric resources. There are over 45,000 large dams, and 10s of 1000s of smaller dams built across the world. The few remaining untapped hydroelectric resources are primarily located in the tundra of Alaska, Canada, Russia, and in some of Latin American and Africa (Withgott & Brennan, p.446, 2007). Consider the United States in comparison, which has exhausted 98% of potential large hydropower plants in the country, while its remaining 2% go untouched due to the fact that they fall within wildlife protected areas. Other developed nations, such as Sweden and Norway, do not have much more they can or need to develop (Withgott & Brennan, p.615, 2007). For some regions, there is even a growing movement for the dismantling of hydropower plants due to their expiration, or the unwillingness of locals to bear the social and environmental cost for any longer. In the United States alone, 500 total dams have been removed, of which 200 of them were retired in the past decade (Withgott & Brennan, p.449, 2007).


Figure 2
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Figure 5
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Figure 6
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Hydropower Costs & Benefits: Overview

With such extensive development of hydropower in non-OECD countries, and a history of many positive and negative consequences in OECD and developing countries, the costs and benefits of keeping and developing hydropower plants must evaluated from an economic, societal, and environmental standpoint. Extensive research has focused on the costs and benefits of large hydropower operations, and both proponents and opponents of hydropower make credible and significant arguments.

The primary issue in constructing new hydropower facilities is in the creation of a large dam for mid- to large-scale hydropower projects. Considering the vast majority of existing and planned hydropower projects are large dams, and small dams are insignificant in number and relative consequences, the following cost-benefit analysis of hydropower will center on the construction of large scale hydropower plants. The analysis is the result of several major, recent studies.

Economic Costs & Benefits

The basic costs to consider in hydropower plant development are the costs to construct the dam, the costs to operate and maintain the facilities, and adverse impact to the economy (localized or beyond), including fishery and agriculture. Dam construction can be enormously capital intensive, such as Three Gorges Dam being constructed on the Yangtze River in China, which is estimated to cost between $26 billion (Chinese estimate) to $50 billion (“Western” estimate) (Etzweiler et al., 2007). Further, unexpected costs must be considered. China, for instance, just recently had an additional, unexpected waste management cost of $5 billion (20% of the estimated cost of the project!). Costs such as these must be considered, because they may make or break the economic value of the project (Withgott & Brennan, p.447, 2007).

The economic benefits of a successfully managed hydropower project are plentiful. Besides the heavy capital needed to build a hydroelectric plant in the beginning, the facility runs almost independent of human or energy inputs, and thus enjoys a very low operating and production cost per kWh. Further, a hydroelectric facility has a lifespan of 50-100 years - which is beyond any fossil-fuel fired plant. This allows the project to a) be depreciated across a longer time period to boost accounting returns (in the case of a privately run hydropower plant), and b) the plant has a longer life to produce revenue (Etzweiler et al., 2007).
From an economic and strategic aspect, by harnessing natural hydropower, a country increases the degree of energy independence and diversifies away from the risk of increasing fossil fuel prices. Moreover, the storage ability of the dam allows energy production to be controlled on an at-need basis, and may also allow a country to manage water reserves for irrigation purposes or in a time of water scarcity (Etzweiler et al., 2007). Lastly, the increase in water levels behind the dam system may allow an expansion of shipping lanes, encouraging trade and the development of wealth (Withgott & Brennan, p.447, 2007).

Environmental Costs & Benefits

Damming flows of water may lead to slow, or even stagnant water bodies, which decreases an ecosystem’s ability to wash away waste (especially human waste). A dammed water flow may also prevent fertile silt from reaching downstream, and impact wildlife and agriculture downstream. Further, fish that swim upstream to spawn may be prevented from doing so, unless proper technology is in place for them to pass without the turbines turning them into sushi (a water “staircase” can be implemented around the sides of the dam). However, negative environmental impact is not limited to downstream; the vegetation engulfed by the dam’s water reservoir decomposes and subsequently emits CO2 and methane (CH4) into the atmosphere, especially in warmer climates (Etzweiler et al., 2007).

The consequences of dammed water may be exacerbated in cases where a dam seasonally releases water from the reservoir behind it so to compensate for dry summers. Why? When the waters subside, land that was previously underwater is now exposed to locals, who may wish to plant crops by the water; however, if a river is contaminated, these areas surrounding the river may become disease-infested and threaten the health of local populations. Another threat to local populations is in an instance of a natural disaster, such as an earthquake or landslide, that causes a large dam to crack and wash away human lives and infrastructure (Etzweiler et al., 2007).

Still, there are some advantages to the environment in using hydroelectricity. Unlike nuclear energy, hydroelectricity does not produce toxic remains. Further, hydropower is fueled by water, which is a renewable resource (Etzweiler et al., 2007).

Social Costs & Benefits

While the social costs and benefits of hydropower significantly vary depending on the project’s circumstances, all should be outlined and considered. In many circumstances, entire communities are forced to relocate due to flooding from a dam; it is estimated that between 40 - 80 million people have been displaced by damming (www.dams.org). For instance, the Three Gorges Dam project in China has led to the washing away of 22 cities and many smaller settlements, forcing a mass exodus of up to two million people (Withgott & Brennan, p.449, 2007). Due to displacement, or instead, a decrease in land resources due to flooding, unemployment or even social conflict might be the result (www.dams.org).

Flooding may also lead to the loss of an area’s aesthetic appeal and part of its fauna diversity. In the case where communities are submerged, the consequence may also be a loss of cultural heritage (Etzweiler et al., 2007). The construction of the Three Gorges Dam, for instance, will lead to the loss of some towns and villages that have over 10,000 years of valuable, national history (Withgott & Brennan, p.447, 2007).

Even with such a negative social cost to damming for hydropower, in many instances, the social benefits may outweigh the costs. For instance, a dam for hydropower can also be used to contain spontaneous flooding that might otherwise have killed countless people, which had been an especially important consideration in the building of the Three Gorges Dam in China. It could also be used for reserves in case of drought, or controlled irrigation of crops so to help safeguard a community’s or country’s food supply like Egypt’s Aswan dam (Etzweiler et al., 2007). Finally, new recreational opportunities abound in the reservoir system created by the dam; although this comes at the cost of recreational activities downstream) (Withgott & Brennan, p.447, 2007).

New Hydropower Technology

New, hydropower technologies in development may yield significant benefits over traditional hydropower technologies, namely, by mitigating the costs of traditional hydropower. Three new hydro technologies, run-of-river, free-standing turbines, and vortex turbines shine hope on the future of low-costs, high-benefit hydropower. However, run-of-river systems are not currently a significant hydropower resource, and both free-standing and vortex turbines are still in their infancy.
Run-of-river systems redirect part of a river’s water through pipelines or other means to generate electricity via a turbine in a land-based powerhouse. This approach avoids the adverse affects of damming in the pursuit of electricity generation, however, it sacrifices the reliability of hydropower generation due to the lack of storage control that dams possess. Run-of-river dams may also be useful in areas beyond the main electrical grid, or for those without the means to build and maintain a dam (Withgott & Brennan, p.614, 2007).

Freestanding turbines are similar to run-of-river systems in the sense that they do not require damming either. Rather, as the name implies, the concept employees freestanding turbines in the middle of a stream, and can currently achieve around a 35% efficiency. Pilot studies are currently being tested around South Korea and North America (End of a dammed nuisance, 2008)

VIVACE, which stands for Vortex Induced Vibrations Aquatic Clean Energy, is a new technology developed at the University of Michigan. It forces the creation of vortices in a body of water by installing man-made bodies in rivers, streams, or oceans (especially the latter), and then captures the parabolic energy swirls that result with an oscillator. The U.S. Department of Energy and the Office Naval Research and the University of Michigan are pursuing this technology further, to the multi-watt prototype level. A company has already been established to promote the new energy source, called Vortex Hydro Energy (Vortex Hydro Energy).


After a thorough evaluation of the history of hydropower and the economic, social, and environmental ramifications that it has brought to humanity, the World Commission for Dams (WCD) issued a highly regarded report in 2000 on integrated decision-making for old and new hydropower projects. The key factor that stood out about this report was that it helps people see past the narrow, economic decision-making only, and also consider the social and environmental factors. I, too, am a proponent of their advice based on my analysis of literature and facts. The following steps may be taken:

The WCD recommends the following advice in integrated decision-making. It recognizes the inherent rights and risks for each party affected by the construction of a new hydroelectric dam. The first step is to recognize and assess the risks of the project, which helps to identify stakeholders. A forum can then be established for an assessment of stakeholder needs, alterative options assessment and planning. If all goes well, both parties will come to terms over negotiations; however, if a consensus cannot be reach, a third part may come in for independent review and mediation. If this is still not successfully, judicial arbitration may be the next step, if not an alternative project option. Upon successful third-party mediation, however, negotiations can continue until an agreement is in place (www.dams.org).

The support of an economic, environmental and social analysis is supported by the five values set the by conference, including equity, sustainability, efficiency, participatory decision-making, and accountability. Indeed, this is wise advice. What is impressive is that the Conference’s extensive review is not only diagnostic, but is prescriptive in these values, and in the decision-making process that employs them (the “rights and risks” analysis).

Note that the WCD concludes that the social and environmental costs of large hydropower projects is too high, however, as do I, they recognize the economic, strategic, and other needs that may compel stakeholders to move forward with hydroelectricity. For these cases, the WCD recommends the consideration of such projects as they have: namely, from an economic, environmental, and social standpoint that considers several core values and strives to recognize and appropriately handle the rights and risks inherent to hydropower projects, which I endorse.

New developments in hydropower technology accrue less costs, while preserving many of the benefits of traditional hydropower. This is a step in the right direction for hydropower for those who wish to generate power with minimal impact, following the guidelines in the WCD 2000 report. Development of these new technologies, and possibly more in the pipeline, may put hydropower on track to restore its prominence in the long-run, and expand profitably into new domains with minimal disruption to humans and the environment. Indeed, the business incorporation of Vortex Hydro Energy is encouraging in this regard.



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Britannica.com. Water Cycle. Retrieved April 29, 2008, from http://updatecenter.britannica.com/art?assemblyId=53235&type=A
Department of Energy. Hydropower. Retrieved April 29, 2008, from http://www.eren.doe.gov/RE/hydropower.html
Ed Hiserodt (2007, November). The "Other" Renewables. The New American, 23(23), 25-27.  Retrieved April 30, 2008, from General Interest Module database. (Document ID: 1386982971).
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Reynolds, T. S. (1983). Stronger Than a Hundred Men: A History of the Vertical Water Wheel JHU Press.
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Vortex Hydro Energy. Vortex Hydro Energy. Retrieved April 29, 2008, from http://www.vortexhydroenergy.com/html/about.html
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