Alternative Energy

By João Araújo, 11º Zi
Escola Secundária de Loulé

Everyday new organic fuels that have not a fossil origin are developed for commercial proposes. Among these, the most promising for a close future are ethyl alcohol (ethanol), bioalcohol (which is a mixture of ethanol and methanol) and biogas (methane).

These organic fuels, as well as hydrogen, are the most promising fuels of the future.

The research in fuel chemistry has a straightforward goal of taking advantage of the use of these raw materials.

Ethanol (CH₃CH₂OH) is produced by biological fermentation of starches from cereals, particularly maize or from the sugar derived from sugar cane. This bioalcohol can then be purified to be almost entirely ethanol. Ethanol and methanol have oxygen in their molecular composition which reduces the energy released in the combustion of each molecule. However, they have a great tendency to burn without formation of secondary products which gives them better fuel characteristics concerning environmental protection. Since its combustion is total there is not a big energetic deficit when compared to hydrocarbons of similar molecular weight. The ethanol is denser that the methane will also carry greater weight in the same volume.

Cereals can be used do produce bioalcohol (Image credit: Wikipedia)

Methane (CH₄) is also obtained from biological materials, but through anaerobic digestion, that is, by processes that occur in the absence of oxygen. Because it produces less energy than the ethanol per unit of volume, methane is less suitable as a fuel for vehicles of heavy transportation. However, it can be used in all applications where natural gas is used. For instance in many farms, suinicultures or herding, the biogas produced from the solid waste is used to feed electrically to the farm.

Another alternative fuel is biodiesel that can be produced from vegetable oils, such as peanut oil or soybean oil.
Hydrogen is the most abundant element in the universe. This makes scientists believe it will be the fuel of the future because it could hold the key to ongoing energy demands. Relatively new technologies (such as fuel cells) can be used to efficiently harness the chemical energy stored in diatomic hydrogen (H₂). However, there is no accessible natural reserve of uncombined hydrogen, since what little there is resides in Earth's outer atmosphere (exosphere). Hydrogen for use as fuel must first be produced using another energy source; hydrogen would thus actually be a means to transport energy, rather than an energy source, just as common rechargeable batteries are. One existing method of hydrogen production is steam methane reformation; however, the most common source of methane is natural gas, which is in short supply. Another method of hydrogen production is through electrolysis of water which uses electricity generated from any source like renewable energy sources (solar, eolic, etc). If molecular hydrogen could be obtained from the water in an economically viable way it would be a virtually inexhaustible source because its combustion regenerates it back to water.

If we can obtain it from water, hydrogen would be an inexhaustible fuel (Image credit: seujhorg)

Fossil Fuel Industry Environmental Impact

by Regina Guerreiro, 12º D
Escola Secundária de Loulé

The combustion of fossil fuels has a daily presence in our lifestyle. Though many people use fossil fuel combustion in their kitchens or for heating, most of the atmospheric pollution generated by fossil fuel combustion is produced in industrial uses, like refineries or thermoelectric production facilities. In the big cities the combustion of gasoline and diesel by cars and other transportation means represents only 40% of the total combustion of fossil fuels.

The combustion gases released are essentially water vapor (H2O), carbon dioxide (CO2) and nitrogen (N2). Of these gases only CO2 emission is hazardous because it is responsible for global warming. Because combustions are seldom complete there are other species like carbon monoxide (CO), nitrogen oxide (NOx), sulfur dioxide (SO2) and lead are often produced. Carbon monoxide is toxic and the nitrogen and sulfur oxides are responsible for acid rains.

Acid rains have made the destruction of many forests in central Europe (Image source: Wikipedia)

The use of fossil fuel combustion is therefore environmentally hazardous and since it is the major source of energy for electricity production and for transportation, one should make a very rational use of electricity and of transportation that implies fossil fuel consumption. Industrial units that use combustion of fossil fuels and automobiles should also use catalytic converters that reduce the emissions of toxic and hazardous components.
Though the emissions of carbon monoxide and nitrogen and sulfur oxides can be reduced by the use of catalysts, carbon dioxide is always emitted. Therefore fossil fuel combustion always leads to global warming.

Global warming is mostly a consequence of CO2 emissions in fossil fuel combustions (Image source: Wikipedia)

Beside the problems associated to the production, use and transportation of crude and its derivatives is related to the atmospheric pollution made by its combustion or transformation or else to accidents. The accidents with tankers aren’t as rare as one should expect. Huge amounts of oil are often released, generating huge pollution marks on the water, that are known as black tides.

Most of the accidents that generated black tides were consequence of accidents with oil tankers. Many of them were the consequence of the aging of the tankers or of inadequate crew training. Black tides are a major concern because they kill fauna and flora in a way that takes several years to be surpassed. The following table presents some examples of major black tides in recent past.

ENERGY PRODUCTION IN PORTUGAL

by Nicolai Manalachi and Ruben Veríssimo, 11º Zi
Escola Secundária de Loulé

Carbon dioxide emissions are one of our major concerns in actuality since it is the major responsible for global warming.

Human effort is now applied in developing alternatives that do not emit CO2 into the atmosphere, since climatic changes - namely temperature rise - are now being perceived at a global scale.

CO2 Emissions in 2000 (Credit: New Scientist)

This problem is so severe that Kyoto’s protocol, signed in 1997 by nearly all countries around the World – one exception was the - has deliberated the need of a drastic drop on CO2 emissions. The evolutions developed until now by modification of traditional combustion motors (Diesel or gasoline) are insufficient to guarantee the success of the protocol.

Hydroelectric energy. (a) A dam at Chança stream at Guadiana river. (b) Turbines.

On the follow up of what was agreed in Kyoto, Portugal assumed the European compromise to guarantee that in 2010, at least 39% of the national consumption of electricity will be provided by renewable sources. Thermoelectric production using coal and/or fuel-oil is still the major electricity source, but this would represent a huge advance.

This ambitious goal implied that renewable energies are no longer viewed as a simple curiosity, only with marginal contributions within the energy sector.

The reasons that support Portugal ’s decision are the fact that alternative energy sources are the only endogenous sources this country possesses and they have a decentralized distribution that may contribute to general development of the country.

Brinches photovoltaic power plant (Source: http://engenhariacivil.wordpress.com )

Portugal has defined its strategy based on the following vectors:
•Huge increase in eolic energy production which means passing from the 290 MW in 2002 to 3.750 MW in 2010;
•Increase up to 150 MW of photovoltaic power in 2010;
•Build new hydroelectric power plants up to a total of 800 MW, increasing hydroelectric contribution to around 4.950 MW;
•Investment in 550 MW from other renewable energy sources (biomass, biogas, urban solid waste, waves and the Sun).

In 2004, Portugal already possessed a significant amount of hydroelectric power installed (aprox. 4.150 MW), that associated to the contribution of other forms of renewable energy are now responsible for about 35% of the national consumption.
Many investments have been made and our now presenting results. Recently at Brinches (Serpa) the worlds 2nd biggest photovoltaic power plant has started its production using 52.000 photovoltaic panels that guarantee a production of 11 MW. An even bigger photovoltaic power plant is now being ended at Amareleja (Moura) that will be the biggest in the world with a 62 MW production. The total amount of installed photovoltaic power at the end of 2007 will be 97 MW.

Eolic energy production has also received a major increase.

Still more investment is needed. Nonetheless, one may consider that though the established goal for 2010 was very ambitious it seems Portugal might be on the way to fulfill it.