Hydroelectricity and Wind Power
Information on Hydroelectricity and Wind Power.
Hydroelectricity
How the Power is generated:
Hydroelectricity uses the potential energy found in the dams and the turns it into kinetic energy as it flows through the pipes into the power station. As the water flows through the pipes it enters the turbine. The greater the size of the dam the greater the pressure in the pipes which makes the turbine spin faster. Once it enters the turbine, the turbine spins rapidly. The kinetic energy of the water is now mechanical energy because it’s spinning the turbines around. The turbine is connected to a generator by a shaft. As the shaft spins the magnets inside the generator spin around the coils of the conductor. This turns the mechanical energy into electrical energy. This electrical energy is the transported via transmission lines to peoples houses and other industrial areas.
Advantages
There are many advantages of using hydroelectricity, one of them is the fact that there is no burning of fossil fuels which also reduces greenhouse missions and in the long run helps the environment and because you don’t need any fuel a hydroelectric dam is a lot more cost effective. Hydroelectric power stations tend to have a longer life expectancy then other energy sources with some lasting for up to one hundred years. Dams are used in many different ways and the added cost to make a dam with a hydroelectric turbine is rather low which is why hydroelectricity is quite popular in some countries. Another great factor of hydroelectricity is that you only pay for the construction of the dam, the aren’t any other costs. Hydroelectricity is also a lot safer due to the fact that coal mining, uranium mining and other fossil fuel mining are dangerous to the workers health and in some extreme cases death can be caused. If you compare hydroelectric dams to wind turbines hydroelectricity is a lot more predictable.
Disadvantages
For every advantage there is usually a disadvantage. These include the disruption of aquatic animal’s habitat and the destruction of the delicate ecosystem. Ss even though it’s not contributing to global warming hydroelectricity is destroying out native fish and plants. Because the water gushes down it affects the river downstream by causing erosion, destroying creek beds and because there is less water at the bottom of the dam the water temperature rises quicker which changes the environment for the inhabitants of the area. The production of a dam can take up to 50 years for the scientists to test what impact it will have on the environment and other geographical studies which makes it a lot less appealing.
Environmental Impact
Hydroelectricity is often considered clean energy because once built (during the construction stage there is a small production of greenhouse gasses) it doesn’t give of any emissions. Another impact is known as Supersaturation, this occurs when air gets trapped under the gushing water which causes turbulence. This causes increased level of nitrogen in water. The nitrogen can then enter the fish’s body tissue and cause serious injury or death to the fish. Because of the higher water levels on one side of the dam the whole ecosystem changes there’s more water and less scrub for small animals to live in.
The question that scientists are trying to answer is that are hydroelectric dams worth it because they are doing a considerable amount of damage to the ecosystem but they are a good source of power.
Geographical locations:
Due to the fact that hydroelectric power stations can only be built where rivers flow they are not always the most ideal source of electricity. Even once a suitable river is found scientists have to research on what the environmental impact will be, they have to make sure that the transmission lines are able to get to the dam and overall the cost to build the dam and hydroelectric plant itself.
Countries that use hydroelectric power:
Most countries will have some hydroelectric plants. The graph below shows the countries that use the most hydro electrical power and how much of it is generated, the capacity of the generators and how much that specific country relies on Hydroelectric power.
Table from http://en.wikipedia.org/wiki/Hydroelectricity#Comparison_with_other_methods_of_power_generation
Formulas
The main formula relating to hydroelectricity is P=hrgk where P is Power in kilowatts, h is height in meters, r is flow rate in cubic meters per second, g is acceleration due to gravity being 9.8 m/s2, and k is the efficiency of the plant.
Wind Power
How the power is generated:
Wind power is generated in a very simple process. The kinetic energy of the wind turns the wind turbine which then turns the generator. That process changes the kinetic energy into electrical energy and then it’s transported to peoples homes and other industrial areas.
Advantages
Wind power also has its advantages. The good thing about wind power is that you only have to pay to put the turbine up and then after that it takes care of itself. There’s no fuel used which doesn’t generate any greenhouse emissions. Even though the turbines are large they can be put on private properties and can power the resident’s homes. The current growth in the wind power sector is creating jobs all over the world which is very helpful due to the fact that where in an economic crisis. Overall wind power is a good renewable energy source because if you think about it where never going to run out of wind.
Disadvantages:
There are numerous disadvantages involving wind power. The main problem is that it’s very inconsistent, wind doesn’t stay at the same speed the whole time which affects the amount of power produces. The table below shows how much power produced by the turbine is greatly affected by the speed of the wind.
| Wind Speed v(ms-1) | Power Output P(kW) |
| 4 | 17 |
| 6 | 342 |
| 7 | 614 |
| 8 | 975 |
| 10 | 2019 |
| 12.5 | 4058 |
Many people are against wind power because they ruin the beauty of the environment, the turbines are very loud. They are considered to make the same amount of noise that a family car traveling at 100km/h and because of this many people refuse to put them on their property. Overall these noisy, ugly things be traveling very fast in order to be able to produce enough electricity to power around 100 homes. Are they worth it?
Environmental impact:
Wind power is amazing because it doesn’t pollute the air, it doesn’t use water and it costs nothing to run, but nothing perfect wind power does effect the environment in some small ways. As stated earlier wind turbines do make some noise which does affect the local residents and animal life. The main impact that wind turbine has on the environment is the damage that it does to the bird. Some birds fly to the turbine to perch but much to their surprise they are hit by the giant rotating blades which instantly kill them. Overall wind energy is a lot more environmentally friendly then the likes of fossil fuels.
Geographical location:
Because of the size of the structure and the fact that wind blows faster in some places the best places to place wind turbines are in costal areas and even in the water, round hills, open plains and gaps in mountains. All of these places are ideal because the wind is strong and reliable. The only problem is that some of these places are remote and it’s sometimes difficult to get the power lines through.
Formulas:
Kinetic energy from the air moving around is known as wind. This formula shows how to work out kinetic energy.
Kinetic energy (joules) = 0.5 x M x V^2
M = mass (kg)
V = velocity (meters per second)
This next formula shows the power in the area swept by the wind turbine rotor. This formula shows the amount of power that in a free flowing stream of wind. This isn’t the output power because no wind turbines are 100% efficient.
P = 0.5 x rho x A x V^3
Where:
P = power
rho = air density (1.225 kg/m^3 at sea level)
A = the area that the rotors cover (m^2)
V = velocity (meters per second)
This last formula shows the amount of power that the wind turbine generates and actually uses.
P = 0.5 x rho x A x Cp x v^3 x Ng x Nb
Where:
P = power
rho = air density (1.225 kg/m^3 at sea level)
A = the area that the rotors cover (m^2)
Cp = coefficient of performance
V = velocity (meters per second)
Ng = generator efficiency
Nb = gearbox bearing efficiency
Bibliography:
Wikipedia, 17 of April 2009, Hydroelectricity, available at,
http://en.wikipedia.org/wiki/Hydroelectricity#Comparison_with_other_methods_of_power_generation accessed on 14/4/09.
Table also found on above site.
Hydro Tasmania, January 2009, Hydro-Electricity, available at http://www.hydro.com.au/handson/students/hydrelec.htm accessed on 14/4/2009.
N. Champion and R. Dedewalage, 2009, Nelsons Physics VCE units 1&2, Nelson Cengage Learning, Australia, pg 165, 166
“Hydroelectricity”, 1981, In World Book Encyclopedia “H” Edition, pg 415
Wind
Australian Academy of Science, May 2008, Wind Power Gathers Speed, available at http://www.science.org.au/nova/037/037key.htm, accessed on 14/4/09.
Paced University, 2000, Electricity from Wind, available at http://www.powerscorecard.org/tech_detail.cfm?resource_id=11 accessed on 16/4/2009.
???, Nov 02, 2008, Energy Sources: Wind Power available at http://home.clara.net/darvill/altenerg/wind.htm accessed on 16/4/09.
Eggleston, 5 February 1998, How Can I Calculate the Amount of Power Available at aGiven Wind Speed? (online), available at http://www.awea.org/faq/windpower.html accessed on 16/4/2009.
N. Champion and R. Dedewalage, 2009, Nelsons Physics VCE units 1&2, Nelson Cengage Learning, Australia, pg 171, 172.
Table found on above resource on pg 175
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