WHAT WE CAN DO​
Hydro power​
​
Hydro power is another renewable energy source that has a large energy potential for commercial exploitation. The fundamental basis behind hydropower is the use of energy form falling or flowing water. Unlike ocean energy, which is also sometimes classified as hydro power, hydro power is a much more matured technology and is currently being used by the majority of countries with the necessary potential.
The technology of hydropower comes in three major forms. The first and most commonly used form is the use of dams to hold back large amounts of water (called the dam’s reservoir). This water is released in controlled amounts through water turbines which generates electricity. This is further illustrated below:
The basic workings of conventional hydroelectric dams (left), such as the Victoria Dam in Sri Lanka (right). Source (left): Wikimedia Commons/CC-BY-SA-3.0.
Source (right): Wikimedia Commons/CC-BY-SA-3.0.
Unlike the other two types of hydro power technology, the building of dams is often considered a negative impact to the environment as it requires submerging large swaths of land to create the reservoir, creating various issues depending on the dam’s location. In some cases, it also affects the natural flow of water and aquatic life. Thus the developments of these facilities are often decided with both the good and bad in mind. This type is sometimes further subdivided into large, small, and pico hydro, depending on its size and power production potential. Pico hydro is sometimes used by farms and houses with the necessary water resource.
​
The second type does not require the building of dams, and hence doesn’t pose much environmental risks. This type, known as ‘run-of-the-river’ or ‘run-of-river’ hydroelectric plants, utilizes the natural flow of water to generate electricity. The diagram below illustrates the basic principal behind these facilities:
In run-of-river plants, the natural flow of water is utilized to turn a water turbine which generates electricity (left). The Chief Joseph plant in the United States is an example of a large run-of-river facility (right). Source (left): Wikimedia Commons/CC-BY-SA-3.0. Source (right): Wikimedia Commons/CC-BY-SA-3.0.
The third type of hydro power technology is known as a ‘pumped-storage’ hydroelectric facility. This type basically utilizes two bodies of water (reservoirs) at different elevations. Water is released from the upper reservoir to the lower reservoir through large pipes (penstocks), where the high velocity water hits water turbines and exits into the lower reservoir. During excess power generation in the grid, these turbines are reversed (turning it into pumps) pumping water back into the upper reservoir.
A diagram of the Raccoon Mountain Pumped-Storage Plant in the United States.
Source: Wikimedia Commons/Public Domain
This cycle is repeated during high and low electricity demand, and is a popular form of commercial energy storage. Depending on the scale and location, some pump-storage facilities also pose environmental risks. And like hydroelectric dams, the development is carried out only after extensive studies.
Ocean power​
​
Ocean power, which is also sometimes classified as a form of hydro power, has been looked into for centuries, with early studies and usage dating all the way back into the year 1799. Despite its long history, deeper research and development has only recently been established. Hence, ocean power is a relatively new technology that can be put into action by utilizing any of the three methods explained below.
The most common form is the use of tidal energy, or the energy from tides. Tides enter and exit lagoons and other such areas frequently; increasing and decreasing the water levels often couple of times a day. One way of using this energy is by trapping this water during the highest tide (using barrages or low dams), and releasing it through water turbines during the lowest tide.
Another way to utilize tidal energy is by constructing tidal turbines at the entrance of this lagoon or other waterway, which in most cases resembles to common horizontal-axis wind turbines. The process is fairly simple, as it works almost similar to as how wind turbines work, except that the turbines are under water.
An artist’s impression of tidal stream generators (left), as compared to the Rance tidal barrage in France (right). Source (left): Wikimedia Commons/CC-BY-SA-3.0. Source (right): Wikimedia Commons/CC-BY-SA-3.0.
Another form of ocean power is the energy from waves. This form is currently in the early stages of development, and hence no commercial-scale facilities are currently under production. Dozens of different ways of exploiting this resource are currently being experimented with, including those that operate on the ocean surface and those that are partially or entirely submerged.​
The Pelamis Wave Energy Converter at the Agucadoura Wave Farm in Portugal uses ocean surface waves to generate electricity. The entire length bends with the wave, thus forcing high pressure oil through turbines to generate power. Source: Wikimedia Commons/Public Domain.
The third type of ocean power is derived by harnessing the power of temperature differences in the ocean. Utilization of thermal differences in the ocean, called ocean thermal energy conversion or OTEC, makes use of elements with a low boiling point such as ammonia, and pumps it down into the ocean where the temperature is higher. Upon reaching the bottom of the loop, the ammonia then converts to steam where it continues its journey back up as steam and turns a turbine. This cycle repeats hence generating continuous power.
This map shows the global ocean temperature differences between depths of 1000m. The higher the difference, the more favourable it is for an OTEC facility. Source: Wikimedia Commons/Public Domain.
These three forms of ocean power are suitable as a clean sustainable source of electricity for hard-to-reach islands where other sources of electricity are not suitable or places where establishing grid-connected supply of electricity is difficult, uneconomical, or impossible. Various further types of ocean energy, such as dynamic tidal power (DTP) or osmotic power which uses ocean salinity differences, are also currently under early development.
Various further types of ocean power sources are also currently being studied. Shown here is a prototype plant in Norway which utilizes ocean salinity differences (known as osmotic power) to generate electricity. Source: Wikimedia Commons/CC-BY-SA-3.0 .
​
​
References:
​
http://en.wikipedia.org/wiki/Wave_power#Modern_technology
http://www.howstuffworks.com/environmental/green-tech/energy-production/ocean-power.htm
http://www.energy.ca.gov/oceanenergy/index.html