Water Energy Facts

Published in Green Energy, Water Energy on 1st February 2014

Wave Energy

Water energy (hydroenergy) is one of the potential energy sources that can be part of the solution in reducing the dependence on fossil fuels in the generation of electricity.

It is a renewable source of energy together with solar and wind energy. There are different methods in which water energy can be harnessed for generating electricity.

In this article, I have summarised the ways to harness it, advantages and disadvantages that come with this source of energy.

 

Ways to Harness Water Energy

Water energy comes in 3 main forms[8]; tidal energy, wave energy and water energy itself. The methods and technology to harness them are listed below.

Building of Dams

Harnessing of water energy can be done by building a structure called a dam across a river. Examples include the Hoover dam in the United States and the Three Gorges dam in China. 

Water turbines of Manapouri Hydroelectric Plant

Hoover Dam

 

 

 

 

 

The dam will block up the river causing a build up of water to form a reservoir. This stored water contains a lot of stored energy (potential energy) which upon release through the dam, will flow at a high speed and turn turbines which will generate electricity simultaneously.

Building of Tidal Barrages

This form of water energy arises from the millions of gallons of water that ebbs and flow with every tidal cycle.

To harness this energy, a similar dam-like structure called a tidal barrage is built in a variety of locations which include estuaries, bays and rivers.

Some examples include La Rance in France and Sihwa Lake tidal power station in South Korea; the oldest and largest tidal barrage in the world respectively. 

Via Floating Buoys

Wave power arises from the movement of wind over water and its energy can be harnessed by floating buoys like those manufactured by the US-based Ocean Power Technologies Inc.

The type of buoys manufactured by them is called the “Power Buoy©“. This range of buoys consists of a moving part that moves in line with the wave motion generating a linear motion.

This linear motion is subsequently converted to a rotary motion which in turn will drive generators that can generate electricity for its own function and support offshore operations.

Why Water Energy? What are the Advantages?

Renewable Energy Source

Just based on its availability and sheer volume, water energy is considered to be a renewable energy source.

Water Energy is Free

You do not need to pay to utilise water energy.

Generates Zero Pollutants

There is no burning involved with no emission of fumes when water energy is utilised for generating electricity.

Lesser Variability

As compared to wind and solar power, the tidal power is more predictable. This means that the source of electricity generated will be consistent especially with tidal maps available to predict the cycles.

Plethora of Uses for Water Energy

Usage of water as a source of energy has been done since ancient times via water wheels to grind grain, cutting of timber in sawmills and in the 1800s for generating electricity. The generation of electricity using water energy can also be done using a dam. One of the earliest dams is the Hoover dam in the United States.

The reservoirs behind the dams can function as recreational areas for swimming, water sports like kayaking. It can also be used for irrigating farmlands or acts as a water supply for cities or towns.

Economical Values  

Countries which do not have fossil fuels but have access to ocean waters or rivers can have a source of energy that is renewable and not affected by prices. They can build dams or barrages for generation of electricity.

One example is the 800-metre Pancasila-Palmerah tidal bridge that is being built at the Larantuka Strait of Indonesia.[4] Building of this tidal barrage will boost local infrastructure; connecting Adonara Island to the eastern tip of Flores opening up economic activity for that region.

It will also be integrated with a container hub as part of President Joko Widodo’s Sea Toll Programme to transform Indonesia into a global maritime hub.

Flood control mechanism

The dams and tidal barrages can function as a flood control by regulating the amount of water inside the reservoirs. In events of extreme rainfall, the dams like the Three Gorges in China can hold water in its reservoir to prevent flooding and adjust the volume of water flowing into the middle and lower reaches of the Yangtze. This helps limit flooding of such cities as Wuhan and Nanjing.[1]

Tidal barrages like the Marina Barrage of Singapore help to alleviate flooding in low lying areas. The tidal gates at the barrage will open to release excess storm water from runoffs into the sea when the tide is low.

Disadvantages of Water Energy

Despite the advantages, there are also disadvantages to utilising and harnessing water energy which I have listed below.

Unpredictable

There is a dependence on rain and snow to maintain the volume and to ensure a constant supply of water inside the reservoir. The amount of precipitation and snowfall are factors that cannot be controlled.

High Costs

The building of a dam is a large-scale project that is very expensive and will require a long period of time to build. The Three Gorges dam of China took around 17 years to build and at a cost of around USD37 billion[6]. Another example is the Belo Monte Dam of Brazil that required 8 years to build at a cost of USD18.5 billion[13][14].

Destruction of Habitat

There are not many readily available locations that can allow the building of a dam. The process of building the dam might result in thousands or millions of people to lose their homes, destruction of wildlife habitats, livelihood and archaeological sites[2]. Construction of the Three Gorges Dam reservoir has inundated two cities, 11 counties and 116 towns in Hubei province and the neighboring Chongqing municipality.[5] It also involved the relocation of 1.2 million inhabitants[3] with the submerging of 1600 factories.[5]

Another example is the Belo Monte dam in Brazil. The diversion of the waters of Xingu River, a major Amazon tributary, to fill up the reservoir has flooded thousands of acres of rainforest destroying wildlife habitat; decimated the local fishing industry; loss of land and livelihoods for the riverside dwellers (ribeirinhos) and the indigenous people like the Kayapó.[13][15]

Alter and Reduce Biodiversity

Damming of river systems can alter the ecological function of river systems in terms of nutrients cycling. Dam reservoirs have been shown to trap reservoir sediments like that reduce the downstream transfer of nutrients to floodplains, lakes, wetlands, and coastal marine environments.

This results in the sequester of nutrients like phosphorus (P) found in the trapped reservoir sediments.[9] Studies have shown that by 2030, up to 17% of global river phosphorus load could be retained in dam reservoirs due to construction of over 3,700 new dams. This reduction of downstream riverine P concentrations would result in higher and further elevated nitrogen to P ratios that can promote unusual algal blooms in downstream waters.[12]

The presence of dams has also resulted in the homogenisation of riverine flows.[16] Studies have shown that such events can result in the establishment of non-native species that are not adapted for survival in the region previously.[17]

The loss of such distinct elements in riverine systems is a setback in conservation efforts as maintenance of these inherent regional differences can contribute landscape-scale ecosystem resilience in the face of global change.[18][19]

References

    1. ^Cheng., D. (2020). https://www.heritage.org/asia/commentary/what-the-potential-crisis-the-yangtze-means-china-and-the-world (last accessed 15/03/2021)
    2. ^China Daily. (2002). http://www.china.org.cn/english/2002/Oct/45265.htm (last accessed 15/03/2021)
    3. ^China Embassy. http://www.china-embassy.org/eng/zt/sxgc/t36512.htm (last accessed 15/03/2021)
    4. ^Masli., N. (2018). https://www.lifegate.com/larantuka-straits-tidal-power-indonesia. (last accessed 15/03/2021)
    5. ^Reuters. (2007). Three Gorges dam causes downstream erosion: study. https://www.reuters.com/article/environment-china-environment-dam-dc-idUST31738620070521 (last accessed 15/03/2021)
    6. ^Reuters. (2009). China says Three Gorges Dam cost $37 billion. https://www.reuters.com/article/idUSPEK84588 (last accessed 15 /03/2021)
    7. ^Travel China Guide (2020). https://www.travelchinaguide.com/river/three-gorges-dam-cost.htm (last accessed 15/03/2021)
    8. ^Owen., R. (2013). Energy from Oceans and Moving Water 32pp. The Rosen Publishing Group Inc. 2013
    9. ^Maavara., T., Parsons., C.T., Ridenour., C. et al. (2015). Global phosphorus retention by river damming. Proceedings of the National Academy of Sciences. 112(51):15603-15608. www.pnas.org/cgi/doi/10.1073/pnas.1511797112.
    10. ^Vörösmarty., C.J., McIntyre., P.B., Gessner., M.O. et al. (2010). Global threats to human water security and river biodiversity. Nature. 467:555–561.
    11. ^Reid., A.J., Carlson., A.K., Creed., I.F. et.al. (2019). Emerging threats and persistent conservation challenges for freshwater biodiversity. Biological Reviews. 94(3):849-873. https://doi.org/10.1111/brv.12480
    12. ^Zhou., J.J., Zhang., M., and Lu., P.Y. (2013). The effect of dams on phosphorus in the middle and lower Yangtze river. Water Resources Research. 49:3659:3669. doi :10.1002/wrcr.20283
    13. ^BBC (2017). https://www.bbc.com/news/world-latin-america-38391377 (last accessed 15/03/2021)
    14. ^Norton Energia (2020). https://ri.norteenergiasa.com.br/a-companhia/historico/ (last accessed 15/03/2021)
    15. ^Amazon Watch (2011). https://amazonwatch.org/assets/files/2011-august-belo-monte-dam-fact-sheet.pdf (last accessed 15/03/2021)
    16. ^LeRoy Poff., N., Olden., J.D., Merritt., D.M. and Pepin., D.M. (2007). Homogenization of regional river dynamics by dams and global biodiversity implications. Proceedings of the National Academy of Sciences of the United States of America. 104(14):5732-5737. https://doi.org/10.1073/pnas.0609812104
    17. ^Olden., J.D., LeRoy Poff., N., Bestgen., K.R. (2006). Life‐history strategies predict fish invasions and extirpations in the Colorado river basin. Ecological Monographs. 76(1):25-40. https://doi.org/10.1890/05-0330
    18. ^Western., D. (2001). Human-modified ecosystems and future evolution. Proceedings of the National Academy of Sciences of the United States of America. 98(10):5458-5465. https://doi.org/10.1073/pnas.101093598
    19. ^Myers., M. and Knoll., A.H. (2001). The biotic crisis and the future of evolution. Proceedings of the National Academy of Sciences of the United States of America. 98(10):5389-5392. https://doi.org/10.1073/pnas.091092498