Goodbye World

Goodbye World!!

(The End)

Hydropower on Rivers

The name given for the electricity generated by hydropower is hydroelectricity.

The electricity is produced using the potential energy of dammed water. The water forces a turbine to rotate. The turbine is linked to an electric generator, where the electricity is generated.

Depending on how much potential energy the water has, the generated power is higher or minor, and the potential energy is proportional to the height/head.

There is a simple formula that let us calculate an approximate value of the generated power by a dam in a river:

‘P=h.r.g.k’.

‘P’ is the power (Kilowatts); ‘h’ is the height (meters); ‘r’ is the flow rate of the water (cubic meters per second); ‘g’ is the gravity acceleration (9.8m/s²); ‘k’ is the coefficient of efficiency which varies between 0 and 1. Usually that coefficient is higher when the turbines are bigger and modern.

As I already said in other post, exploring this energy has 2 main types of costs: money and the change of nearby habitats.

Sources:
http://en.wikipedia.org/wiki/Hydroelectricity
http://www.youtube.com/watch?v=htT_8sFJx1w

Renewable Energies

In the last years, many countries have used each time more renewable energies, not just because fossil energies are limited, but because people are thinking on the climate changes. Every day are made investments in wind energy, hydro energy, solar energy and biomass with the purpose of minimize the environmental impacts and increase the global energy without the use of fossil fuels, but that´s not enough.
Global population should decrease their energetic consume and try always improve, using technologies that help the humanity become less dependent on fossil fuels.
Environmental debates should be discussed between the politicians in order to teach how to save energy and alert people for the dangers that our Planet´s health is dealing.

Biogas

Biogas is a type of biofuel.

The fermentation or the anaerobic digestion of biodegradable materials produces this gas. It’s formed primarily by Methane and Carbon Dioxide.

There is another type of biogas named wood gas. It’s created by the process of gasification of wood. It’s composed mainly by Nitrogen, Hydrogen and Carbon Monoxide, and it has traces of Methane.

Hydrogen, Carbon Dioxide and Methane can be oxidized or combusted when exposed to Oxygen.
Depending on how it’s produced it may cause more or less pollution.

Biogas is usually used for heating purposes, such as cooking. It can also be used to power car engines.

What I think: There are probably other better choices to power car engines, but it’s better to use biogas than depending on fossil fuels like petroleum.



Sources:
http://en.wikipedia.org/wiki/Biogas

Biomass

Biomass is related to biological material that died recently and can be used to produce energy (electricity, biofuel, etc.). Fossil fuels aren’t considered biomass, because they are “born” from organic material that has been transformed by geological processes.

The most common biomass resource is the wood.

This source of energy has a lot of negative impacts to the environment (Atmospheric pollution / Dangerous to the Ozone layer).

The plants store some Carbon because of the photosynthesis process (the Carbon stored in dry wood is around 50% of the wood weight). When the plant dies or is burned, the Carbon is released with Oxygen to the Atmosphere as CO2.

It might be a renewable energy, but I think we’d better use the wind power or other renewable energy source that is friend of the environment.







Combustion of wood, an example of the use of biomass energies.





Sources:
http://en.wikipedia.org/wiki/Biomass
RODRIGUES, Maria, DIAS, Fernando, Física na Nossa Vida, Porto Editora, 2007

Tidal Power

This form of energy derives directly from the relative moves of Earth, Moon and Sun.

Tidal power is classified as a renewable energy source because it’s generated by the gravity interactions between Earth, Moon and Sun.

The Earth-Moon system is losing mechanical energy because of the tides. Because of this loss of energy, in the last 620 million years the rotation period of Earth has increased from 22 to 24 hours.

Tidal power can be converted into electricity using:

- Tidal stream generators;

- Barrages.

Tidal Stream Generators

This technology transforms the energy from the currents (kinetic energy) like the wind turbines do.

Now you’re probably thinking: ‘But the speed of water is around one-tenth of the wind speed!’ Yes, that’s true. But the water density is around 830 times the density of air, so a system of turbine of the same size may produce the same power.

Barrage Tidal Power

Barrages, placed into estuaries, use the difference of height (potential energy) between low and high tides.
This way to produce electricity involves more costs, can only be used in some sites and may cause some environmental issues. Those environmental issues are related to the reduction of the saltwater flow, what make changes to the estuary as a habitat.





Sources:
http://en.wikipedia.org/wiki/Tidal_power
http://www.youtube.com/watch?v=tSBACzRE3Gw

Main Advantages/Disadvantages of Renewable Energies

Solar power:

The Sun is an inexhaustible source of energy, at human life scale. It can produce two types of energy: heat and electricity. The only problem is that this source of energy can’t be explored in places where the solar radiation is low.



Wind power:
The wind is an inexhaustible and very economic-efficient source of energy. It is harmless to the environment, although it produces noise pollution. It can only produce an efficient amount of electricity if the wind has a velocity of 6 m/s.





Hydro power:
That energy is produced by dams and it is expensive to explore. It doesn’t pollute the environment, but it makes some changes to the environment that may be harmful to the living beings that habit there.




Tidal power:
That source of energy isn’t widely used yet. The energy of the tides is used to produce electricity. It’s harmless to the environment, but it’s very expensive, and it can only be explored in some places.




Wave power:
Pelamis devices use the energy of waves to produce electricity. As the tidal power, this source of energy isn’t widely used yet, it’s very expensive and it can only be explored in some places. The world's first commercial wave farm is based in Portugal.



Now you ask me what I think about this. My answer is:
Use them all where it's possible!

Sources:
http://en.wikipedia.org/wiki/Renewable_energy
http://en.wikipedia.org/wiki/Hydroelectricity
http://en.wikipedia.org/wiki/Solar_energy
http://en.wikipedia.org/wiki/Tidal_power
http://en.wikipedia.org/wiki/Wave_power
http://en.wikipedia.org/wiki/Wind_power
RODRIGUES, Maria, DIAS, Fernando, Física na Nossa Vida, Porto Editora, 2007