Water Energy Facts
Water energy or Hydroenergy is one of the potential energy sources that can form part of the solution in reducing the dependence on fossil fuels in the generation of electricity.
It is also considered a renewable source of energy due to its sheer volume and availability. There are various methods in which water energy can be harnessed for generating electricity.
In this section I have summarised the ways to harness it, advantages, the uses and the disadvantages that come with this source of energy.
Ways to Harness Water Energy
Water energy comes in 3 main forms1; 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.
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; the oldest tidal barrage in the world and the Bay of Fundy in Canada.
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 and so no emission of fumes takes place when water energy is utilised for generating electricity.
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.
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.
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 can hold back water to prevent flooding from happening downstream.
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… Some Facts
Despite the advantages, there are also disadvantages to utilising and harnessing water energy which I have listed below.
The building of a dam is a large-scale project that is very expensive and will require a long period of time to build. Using the 3 Gorges Dam of China as an example, building of the dam took around a decade to build and at an approximate cost of around 25 billion pounds3.
Destruction of Habitat
There are not many readily available locations that can allow the building of a dam. Therefore the building process, it might cause thousands of people to lose their homes, wildlife habitats and even archaeological sites.
This is one of the problems2 that are faced by the 3 Gorges Dam in China with some causes of habitat destruction in the form of landslides due to erosion of the reservoir and the downstream riverbanks.
There was also a huge displacement of inhabitants that used to populate the region is now part of the reservoir or the dam. Efforts to resettle the displaced population were also plagued with problems that were not be covered in this website but to sum it off it was difficult with an estimated amount of 1.2 to 1.9 million people displaced.
Disrupt Natural Habitats and Wildlife Living Patterns
Building a dam can change the river’s water levels, flow patterns and temperature. This can result in disruptions to the lives of wild animals like for e.g. spawning habits of salmon which was disrupted by dams.
One solution will be to construct fish ladders at the side of the dam to help spawning fishes like salmon to travel upstream to their spawning grounds.
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.
The stagnated water behind the reservoirs can accumulate sediment resulting in eutrophication4 of the water. This nutrient-enriched water will support algal bloom during the warm summer months which can cause issues in smell and taste, clog up water supply intake pipes and restrict water for recreational usage.
When the algae die, they will sink and the decaying process will take place at the bottom later of the reservoir where they will use up the already limited dissolved oxygen. Acidification of the water will also take place as carbon dioxide is released as a by-product of the decaying process. This acidic and oxygen-poor water is a perfect medium for dissolving heavy metals like manganese and iron from the river bed.
When this water is released from the reservoir, besides the potential harmful high concentration of dissolved heavy metals, the dissolved-oxygen deplete water also can “suffocate” aquatic organisms. This water will also not be fit for human consumption.
1. R Owen Energy from Oceans and Moving Water 32pp. The Rosen Publishing Group Inc. 2013.
2. http://www.internationalrivers.org/campaigns/three-gorges-dam (last accessed 03/04/2015)
3. http://www.bbc.com/news/world-asia-china-20103483 (last accessed 03/04/2015)
4. http://www.internationalrivers.org/dams-and-water-quality (last accessed 03/04/3015)
(Last Updated 3rd April 2015)