Showing posts with label November 2008. Show all posts
Showing posts with label November 2008. Show all posts
Fossile Fuel Problem
By Sara Martins, 11ºZi Escola Secundária de Loulé
To develop its daily activity, mankind uses several sources of energy, with more than 90% of our energy needs being provided by fossil fuels (coal, oil and natural gas), while the remaining 10% are mainly satisfied by nuclear energy and hydroelectric power.
Sources of energy such as wind, the sun, the tides, the waves, geothermal and biomass still have a small expression in world’s energy consumption, though their use is continuously increasing. Our current lifestyle has been made possible thanks to fossil fuels.
The natural gas that heats our homes, the gasoline that makes our vehicles move and the coal that provides much of the electrical power that comes into our houses are, as we know, fossil fuels. Natural reserves of coal, oil and natural gas exist all around the world, but these reserves are not inexhaustible. In fact, the natural processes that allow the formation of fossil fuels take millions of years and we are spending them at a much higher rate than they form. Therefore we can consider fossil fuels as sources of non-renewable energy.
The oil crisis in the 70s has caused a 500% raise in the price over a short period of time. It was thought at the time (based on more political than scientific reasoning) that fossil fuels had nearly ended. That made people rush towards the use of renewable energies and made governments increase their research for methods to save fuel. As people realized that there was still much oil they returned to same consumption they had previously.
This way of thinking has reached our days and there are still some people saying that the in the past we have not spent half of the world's oil reserves. Though this is in a certain way true, it is much harder to extract oil from the bottom of the ocean than from earths solid surface and not all the existing oil can be extracted in an economically viable way.
In 1956, Marion King Hubbert, a geologist for Shell developed a mathematical expression able to predict the amount of oil that could be extracted from a well over time is that the quantity of oil that will be produced. It was the basis for construction of a graphs (Hubbert curves) that have been able to follow, with astonishing accuracy, the peaks of exploitation in all geographical areas.
Hubbert assumed that after fossil fuel reserves (oil reserves, coal reserves, and natural gas reserves) are discovered, production at first increases approximately exponentially, as more extraction commences and more efficient facilities are installed. At some point, a peak output is reached, and production begins declining until it approximates an exponential decline.
The Hubbert curve for coal
The Hubbert curve satisfies these constraints. Furthermore, it is symmetrical, with the peak of production reached when half of the fossil fuel that will ultimately be produced has been. It also has a single peak.
Looking at the curves quickly see that the maximum production will be reached within a couple of years. The model of King Hubbert also provides that the maximum coincides with the reduction by half of the reserves of oil initials.
Before 2010, the supply of oil will begin to decline, which means drastic increases in their price, if its demand does not decrease. The ending of the other fossil fuels will also be difficult to solve, with the natural gas expected last little more than oil and coal reserves estimated to last 200 to 300 years.
According to the most optimistic reserve estimates the years left for production of fossil fuels are:
• Oil: 1,277,702/77/365= 45 years
• Gas: 1,239,000/47/365= 72 years
• Coal: 4,786,000/52/365= 252 years
Bibliography
• Nuclear Energy and the Fossil Fuels,M.K. Hubbert, Presented before the Spring Meeting of the Southern District, American Petroleum Institute, Plaza Hotel, San Antonio, Texas, March 7-8-9, 1956
• Hubbert’s Petroleum Production Model: An Evaluation and Implications for World Oil Production Forecasts, Alfred J. Cavallo, Natural Resources Research,Vol. 13,No. 4, December 2004
• Maugeri, L. (2004). Oil: Never Cry Wolf--Why the Petroleum Age Is Far from over. Science 304, 1114-1115
• Global oil & gas depletion: an overview, R.W. Bentley, Energy Policy, 30, 189–205, 2002
• Wikipedia-Fossil fuels (http://en.wikipedia.org/wiki/Fossil_fuel)
• BP Statistics(http://www.bp.com/productlanding.do?categoryId=6848&contentId=7033471)
Sources of energy such as wind, the sun, the tides, the waves, geothermal and biomass still have a small expression in world’s energy consumption, though their use is continuously increasing. Our current lifestyle has been made possible thanks to fossil fuels.
The natural gas that heats our homes, the gasoline that makes our vehicles move and the coal that provides much of the electrical power that comes into our houses are, as we know, fossil fuels. Natural reserves of coal, oil and natural gas exist all around the world, but these reserves are not inexhaustible. In fact, the natural processes that allow the formation of fossil fuels take millions of years and we are spending them at a much higher rate than they form. Therefore we can consider fossil fuels as sources of non-renewable energy.
The world’s natural deposits of coal ("BP Statistics", 2004) (click the image too see a larger version)
The world’s natural deposits of crude ("BP Statistics", 2004) (click the image too see a larger version)
The world’s natural deposits of natural gas ("BP Statistics", 2004) (click the image too see a larger version)
The world’s natural deposits of crude ("BP Statistics", 2004) (click the image too see a larger version)
The world’s natural deposits of natural gas ("BP Statistics", 2004) (click the image too see a larger version)
The oil crisis in the 70s has caused a 500% raise in the price over a short period of time. It was thought at the time (based on more political than scientific reasoning) that fossil fuels had nearly ended. That made people rush towards the use of renewable energies and made governments increase their research for methods to save fuel. As people realized that there was still much oil they returned to same consumption they had previously.
This way of thinking has reached our days and there are still some people saying that the in the past we have not spent half of the world's oil reserves. Though this is in a certain way true, it is much harder to extract oil from the bottom of the ocean than from earths solid surface and not all the existing oil can be extracted in an economically viable way.
In 1956, Marion King Hubbert, a geologist for Shell developed a mathematical expression able to predict the amount of oil that could be extracted from a well over time is that the quantity of oil that will be produced. It was the basis for construction of a graphs (Hubbert curves) that have been able to follow, with astonishing accuracy, the peaks of exploitation in all geographical areas.
Hubbert assumed that after fossil fuel reserves (oil reserves, coal reserves, and natural gas reserves) are discovered, production at first increases approximately exponentially, as more extraction commences and more efficient facilities are installed. At some point, a peak output is reached, and production begins declining until it approximates an exponential decline.
The Hubbert curve for coal
The Hubbert curve satisfies these constraints. Furthermore, it is symmetrical, with the peak of production reached when half of the fossil fuel that will ultimately be produced has been. It also has a single peak.
Looking at the curves quickly see that the maximum production will be reached within a couple of years. The model of King Hubbert also provides that the maximum coincides with the reduction by half of the reserves of oil initials.
Before 2010, the supply of oil will begin to decline, which means drastic increases in their price, if its demand does not decrease. The ending of the other fossil fuels will also be difficult to solve, with the natural gas expected last little more than oil and coal reserves estimated to last 200 to 300 years.
According to the most optimistic reserve estimates the years left for production of fossil fuels are:
• Oil: 1,277,702/77/365= 45 years
• Gas: 1,239,000/47/365= 72 years
• Coal: 4,786,000/52/365= 252 years
Bibliography
• Nuclear Energy and the Fossil Fuels,M.K. Hubbert, Presented before the Spring Meeting of the Southern District, American Petroleum Institute, Plaza Hotel, San Antonio, Texas, March 7-8-9, 1956
• Hubbert’s Petroleum Production Model: An Evaluation and Implications for World Oil Production Forecasts, Alfred J. Cavallo, Natural Resources Research,Vol. 13,No. 4, December 2004
• Maugeri, L. (2004). Oil: Never Cry Wolf--Why the Petroleum Age Is Far from over. Science 304, 1114-1115
• Global oil & gas depletion: an overview, R.W. Bentley, Energy Policy, 30, 189–205, 2002
• Wikipedia-Fossil fuels (http://en.wikipedia.org/wiki/Fossil_fuel)
• BP Statistics(http://www.bp.com/productlanding.do?categoryId=6848&contentId=7033471)
Alternative Energy
By João Araújo, 11º Zi
Escola Secundária de Loulé
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.
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.
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)
Energy and global warming
By Alexandre Costa, Teacher
Escola Secundária de Loulé
Escola Secundária de Loulé
Greenhouse effect receives its name after the similar effect that occurs in greenhouses because the glass is opaque to infrared radiation, which produces a rise in temperature. This temperature increase happens because all of the other radiation can cross the glass both ways, but infrared cannot. Inside the greenhouse most of the energy emitted by the bodies and the soil is infrared, and since glass is opaque to this radiation a big part of it will be absorbed and reemitted to the inside of the greenhouse. Since infrared emission is the major emission coming from the inside, but visible emission is the major emission from the outside, the energy that comes in is bigger than the energy that gets out. This produces an energy increase inside the greenhouse.
The temperature of a planet is a balance between the absorbed energy and the emitted energy.
Earth only absorbs 70% of the energy that arrives from the Sun. This means that Earth’s albedo is 0.3 (30% of the energy is reflected back to space).
In the most simple approach to the radiation balance between Earth and its surroundings Earth’s atmosphere is considered completely transparent, and this would imply that the 70% of the solar energy would arrive to the ground and all energy emitted by Earth would be transmitted to outer space.
If scientists considered only the radiation balance between Earth and its surroundings their calculations of Earth’s mean temperature would be 33 K (33 ºC) lower than the real observed temperature of about 288K (ca. 15 ºC). This implies that Earth's energy balance is much more complex (Figure 1).
But Earth’s atmosphere is not transparent, because there is some absorption by gases in the atmosphere. The most abundant gases (oxygen and nitrogen) are in fact transparent to infrared radiation. But some minor gases like water vapour, carbon dioxide, ozone and methane are very opaque to infrared radiation and this is what induces greenhouse effect (Figure 2). One may think that the atmosphere has so little amount of matter that it seems impossible that it can induce so big changes in climate with such small amounts of greenhouse gases.
But Earth’s atmosphere is, in fact, inducing major changes in global temperature. Though water vapour presents big greenhouse effect, its contribution remains mostly constant. Carbon dioxide, on the other hand, has had a consistent concentration rise over the years and this has produced a clear global warming over the last decades (Figure 3).
Though it represents only 0,04% of the gaseous composition of the atmosphere, CO2 emissions have been continuously growing and this is responsible for global warming.
Considering its albedo of 76%, the expected temperature, from a simple energy balance without greenhouse effect would be 232 K. Nonetheless, because its atmosphere has about 96% of CO2, its real surface temperature is about 700 K. Greenhouse effect makes the temperature of the dark side of the planet to be the same as the temperature of the bright side.
Since most CO2, emitted is produced in fossile fuel combustions to produce energy, this is also a major concern on the quest for new energy sources.
Bibliography
• Cabrera,M.E, Hoyos,C., Ledesma,J.L., Nieto,J.M., Revuelta,J.L., Romero,T., Salamanca,C., Torres,M.D., Velasco,J.M. (1996) Ciencias de la Tierra y del Medio Ambiente, Madrid: Editorial Editex.
• MacCracken, M.C., Luther, F.M, (eds), 1985. Projecting the climatic effects of increasing carbon dioxide. DOE/ER-0237, United States Department of Energy, Washington D.C., pp. 381.
• Mitchell, J.F.B. 1989. The "greenhouse" effect and climate change. Reviews of Geophysics 27:115.
• Sturman, A.P. and N.J. Tapper. (1996) The Weather and Climate of Australia and New Zealand, Melbourne: Oxford University Press.
The temperature of a planet is a balance between the absorbed energy and the emitted energy.
Earth only absorbs 70% of the energy that arrives from the Sun. This means that Earth’s albedo is 0.3 (30% of the energy is reflected back to space).
In the most simple approach to the radiation balance between Earth and its surroundings Earth’s atmosphere is considered completely transparent, and this would imply that the 70% of the solar energy would arrive to the ground and all energy emitted by Earth would be transmitted to outer space.
If scientists considered only the radiation balance between Earth and its surroundings their calculations of Earth’s mean temperature would be 33 K (33 ºC) lower than the real observed temperature of about 288K (ca. 15 ºC). This implies that Earth's energy balance is much more complex (Figure 1).
Figure 1. Earth’s energy balance. Adapted from MacCracken & Luther, 1985, de Mitchell, 1989, Sturman and Tapper,1996 e Cabrera et al.,1996. The percentages are relative to the radiation that reaches Earth from the Sun per square meter.
But Earth’s atmosphere is not transparent, because there is some absorption by gases in the atmosphere. The most abundant gases (oxygen and nitrogen) are in fact transparent to infrared radiation. But some minor gases like water vapour, carbon dioxide, ozone and methane are very opaque to infrared radiation and this is what induces greenhouse effect (Figure 2). One may think that the atmosphere has so little amount of matter that it seems impossible that it can induce so big changes in climate with such small amounts of greenhouse gases.
Figure 2. Absorption spectra of the atmosphere and of its two major greenhouse gases (water vapour and carbon dioxide). Adapted from Cabrera et al., 1996.
But Earth’s atmosphere is, in fact, inducing major changes in global temperature. Though water vapour presents big greenhouse effect, its contribution remains mostly constant. Carbon dioxide, on the other hand, has had a consistent concentration rise over the years and this has produced a clear global warming over the last decades (Figure 3).
Figure 3. Global warming over time (Credit: Climatic Research Unit (http://www.cru.uea.ac.uk/)).
Though it represents only 0,04% of the gaseous composition of the atmosphere, CO2 emissions have been continuously growing and this is responsible for global warming.
Some people are very sceptical about global warming. We recommend them to study Venus (Figure 4).
Considering its albedo of 76%, the expected temperature, from a simple energy balance without greenhouse effect would be 232 K. Nonetheless, because its atmosphere has about 96% of CO2, its real surface temperature is about 700 K. Greenhouse effect makes the temperature of the dark side of the planet to be the same as the temperature of the bright side.
Since most CO2, emitted is produced in fossile fuel combustions to produce energy, this is also a major concern on the quest for new energy sources.
Bibliography
• Cabrera,M.E, Hoyos,C., Ledesma,J.L., Nieto,J.M., Revuelta,J.L., Romero,T., Salamanca,C., Torres,M.D., Velasco,J.M. (1996) Ciencias de la Tierra y del Medio Ambiente, Madrid: Editorial Editex.
• MacCracken, M.C., Luther, F.M, (eds), 1985. Projecting the climatic effects of increasing carbon dioxide. DOE/ER-0237, United States Department of Energy, Washington D.C., pp. 381.
• Mitchell, J.F.B. 1989. The "greenhouse" effect and climate change. Reviews of Geophysics 27:115.
• Sturman, A.P. and N.J. Tapper. (1996) The Weather and Climate of Australia and New Zealand, Melbourne: Oxford University Press.
Fossil Fuel Industry Environmental Impact
by Regina Guerreiro, 12º D
Escola Secundária de Loulé
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.
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.
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 in our way of living
By Nuno Oliveira, 12ºD
Escola Secundária de Loulé
Escola Secundária de Loulé
Energy is an important factor on our daily life. In everything that we do, there are always energy exchanges between systems. The simple fact the we breath or even think, is responsible for a large amount of processing in these exchanges.
Rational use of energy in houses and schools is a major concern in our time. Since most electric power is still produced in thermoelectric power plants using fossil fuels, waist of electric energy will be a way of accelerating fossil fuel consumption and also an extra contribution to global warming, since the fossil fuels that are burned to produce electric energy produce carbon dioxide, is the major atmospheric component that we can consider responsible for global warming. Nuclear Power Plants are still not a solution because, besides the security problems, fission depends on uranium and uranium is not renewable.
In our houses, schools and cars, energy is always present.
We can think of several ways to optimize energy consumptions in our daily life.
For instance in house construction there are several things that have to be thought that can reduce energy consumption.
The house should be prepared in order to achieve the higher thermal insulation that is possible. This can be done by using double walls, and double glass windows. In the first case the low thermal conductivity of air or a polystyrene layer between the two wall layers can help to prevent easy energy transfer in or out of the house. In double glass windows this is guaranteed by the air layer between the two glasses.
A solar collector for water heating
We can also use local energy resources like sunlight to increase energy use efficency.
In our houses, schools and cars, energy is always present.
Rational use of energy in houses and schools is a major concern in our time. Since most electric power is still produced in thermoelectric power plants using fossil fuels, waist of electric energy will be a way of accelerating fossil fuel consumption and also an extra contribution to global warming, since the fossil fuels that are burned to produce electric energy produce carbon dioxide, is the major atmospheric component that we can consider responsible for global warming. Nuclear Power Plants are still not a solution because, besides the security problems, fission depends on uranium and uranium is not renewable.
A nuclear power plant close to Berlin.
In our houses, schools and cars, energy is always present.
We can think of several ways to optimize energy consumptions in our daily life.
For instance in house construction there are several things that have to be thought that can reduce energy consumption.
The house should be prepared in order to achieve the higher thermal insulation that is possible. This can be done by using double walls, and double glass windows. In the first case the low thermal conductivity of air or a polystyrene layer between the two wall layers can help to prevent easy energy transfer in or out of the house. In double glass windows this is guaranteed by the air layer between the two glasses.
A solar collector for water heating
We can also use local energy resources like sunlight to increase energy use efficency.
In our houses, schools and cars, energy is always present.
ENERGY IN CHEMICAL REACTIONS
By Vítor Almeida, 11º Zi
Escola Secundária de Loulé
Photosynthesis
Credit: www.caribbeanedu.com/kewl/science/science05.asp
Escola Secundária de Loulé
Energy is involved in all chemical reactions. The energy held in the covalent bonds between atoms in a molecule is called chemical potential energy. Chemical potential energy is a form of potential energy related to the structural arrangement of atoms or molecules. This arrangement may be the result of chemical bonds within a molecule, interaction between molecules or crystal lattices in metallic or ionic structures. Chemical energy of a chemical substance can be transformed to other forms of energy by a chemical reaction. For example, when a fuel is burned its chemical energy is converted to heat, that can then be transformed into work that makes our car or another transportation work.
The same thing happens with biological metabolism. The chemical energy stored in our body may be transformed in order to provide us energy that we can use to move ourselves around.
The same thing happens with biological metabolism. The chemical energy stored in our body may be transformed in order to provide us energy that we can use to move ourselves around.
Green plants transform solar energy to chemical energy through the process known as photosynthesis.
Photosynthesis
Credit: www.caribbeanedu.com/kewl/science/science05.asp
Electrical energy can be converted to chemical energy through electrochemical reactions or vice-versa. Transformation of chemical energy into electricity is in fact one of our present major concerns. Most of our energy production is done in power plants where fossil fuels are burned in order to heat up water that makes turbines work in order to produce electrical power.
Where does the energy released in the chemical reaction come from? Every bond has a certain amount of energy. To break the bond requires energy - in chemical language breaking is said to be endothermic. If a bond is formed, energy is release – bond formation is called exothermic.
In a chemical reaction bonds are at first broken and afterwards atoms are again bonded together to create new molecules. Sometimes the energy released when new bonds are formed is bigger than the energy spent to break the initial bonds. The reaction is said exothermic. If the opposite occurs the reaction is said endothermic.
Combustions of carbon compounds like the one’s that occur in fossil fuels with oxygen are usually exothermic. When the reaction is exothermic the energy released in the form of heat can then be converted in order to produce electricity. There is a price to pay on this type of energy production: release of carbon dioxide to the atmosphere.
In fact carbon compounds combustion's always produce CO2. For example for methane the combustion reaction is
Where does the energy released in the chemical reaction come from? Every bond has a certain amount of energy. To break the bond requires energy - in chemical language breaking is said to be endothermic. If a bond is formed, energy is release – bond formation is called exothermic.
In a chemical reaction bonds are at first broken and afterwards atoms are again bonded together to create new molecules. Sometimes the energy released when new bonds are formed is bigger than the energy spent to break the initial bonds. The reaction is said exothermic. If the opposite occurs the reaction is said endothermic.
Combustions of carbon compounds like the one’s that occur in fossil fuels with oxygen are usually exothermic. When the reaction is exothermic the energy released in the form of heat can then be converted in order to produce electricity. There is a price to pay on this type of energy production: release of carbon dioxide to the atmosphere.
In fact carbon compounds combustion's always produce CO2. For example for methane the combustion reaction is
Emission of carbon dioxide is major concern because it contributes to global warming. This is why we are now trying to develop new ways of producing energy that do not require the combustion of fossil fuels.
Eolic Energy
By Luís Martins, 11ºZi
Escola Secundária de Loulé
Eolic Energy
Windpark at Sines (Portugal).
Offshore eolic park.
Escola Secundária de Loulé
Windmills are an excellent alternative for the production of electricity from wind energy. Windmills produce energy because the wind causes the rotation of a turbine that generates electric current.
Eolic Energy
The yield of a windmill clearly depends on the diameter of their shovels and, up to a certain value, of the wind speed at the place where it is installed. For this reason, the installation of a central wind lacks a prior study about the conditions of the location where the windmill’s installation site.
Windpark at Sines (Portugal).
The cost of installation was in the beginning the biggest obstacle to the installation of such plants. However, scientific research has helped the income earned by such plants to improve over time as the relation benefit/cost increases.
Huge shovels with more than 100m are starting to be common. Offshore windmills are installed to guarantee wind that is strong enough to keep these huge generators working.
Huge shovels with more than 100m are starting to be common. Offshore windmills are installed to guarantee wind that is strong enough to keep these huge generators working.
Offshore eolic park.
In the present the European installed wind power increases on a daily basis. Wind, as well as solar and other renewable-energy technologies that were once considered more appropriate for single homes or small communities. Today they are begining to be considered as a real alternative to coal and gas fired plants and to nuclear reactors. In other words, energy is going green.
Solar Energy
By Vasco Batista, 11ºZi
Escola Secundária de Loulé
Solar Power Plant in Serpa, Portugal
Image credit: The Sietch Blog
Escola Secundária de Loulé
A solar cell or photovoltaic cell is a device that converts light energy into electrical energy. Sometimes the term solar cell is reserved for devices intended specifically to capture energy from sunlight, while the term photovoltaic cell is used when the light source is unspecified.
Fundamentally, the device needs to fulfil only two functions: photogeneration of charge carriers (electrons and holes) in a light-absorbing material, and separation of the charge carriers to a conductive contact that will transmit the electricity (simply put, carrying electrons off through a metal contact into a wire or other circuit). This conversion is called the photovoltaic effect.
Fundamentally, the device needs to fulfil only two functions: photogeneration of charge carriers (electrons and holes) in a light-absorbing material, and separation of the charge carriers to a conductive contact that will transmit the electricity (simply put, carrying electrons off through a metal contact into a wire or other circuit). This conversion is called the photovoltaic effect.
Solar Power Plant in Serpa, Portugal
Image credit: The Sietch Blog
Since they use radiation from the Sun that is a renewable source photovoltaic cells are a good alternative for the production of electrical energy, particularly for areas with a high incidence of solar radiation.
However, the high cost of installation and low yield (which implies a huge surface to produce significant energy) are the biggest obstacle to the widespread use of this type of energy.
Due to the huge daily insulation period Portugal has made large investments in solar power, making it one of the biggest producers in a worldwide scale.
Nuclear fission energy
By Ricardo Caroço, 12ºC
Escola Secundária de Loulé
Enrico Fermi (1901-1954).
Scheme of a nuclear fission chain reaction of uranium-235.
(Credit: Serway&Jewett,Physics for Scientists and Engineers-with Modern Physics, 6th Ed., Thomson-Brooks/Cole, USA)
Scheme of a nuclear fission reactor.(Adapted from Serway&Jewett,Physics for Scientists and Engineers-with Modern Physics, 6th Ed., Thomson-Brooks/Cole, USA)
A nuclear reactor with tipical blue of the Cerenkov radiation. Credit: Wikipedia
Escola Secundária de Loulé
Nuclear fission energy has been the energy that has generated more controversy, often by being linked to the common citizen to military devices and many other times by ignorance of all the potential that has this kind of energy.
Nuclear fission power not only follows the release of electromagnetic energy-related links between electrons, protons and atoms, but occurs with the mass conversion of matter into energy. As we will see below, this makes it the largest release of energy that can be obtained from the field.
In 1942, Enrico Fermi has set in motion the first nuclear reactor. Since then nuclear power has been look of the most diverse forms. Earlier seemed it is a clean energy and without risks.
However, time has shown us the opposite with nuclear disasters as Windscale (1957), Three Mile Island (1979) and Chernobyl (1986), and serious problems such as waste and nuclear weapons.
Nuclear fission power not only follows the release of electromagnetic energy-related links between electrons, protons and atoms, but occurs with the mass conversion of matter into energy. As we will see below, this makes it the largest release of energy that can be obtained from the field.
In 1942, Enrico Fermi has set in motion the first nuclear reactor. Since then nuclear power has been look of the most diverse forms. Earlier seemed it is a clean energy and without risks.
However, time has shown us the opposite with nuclear disasters as Windscale (1957), Three Mile Island (1979) and Chernobyl (1986), and serious problems such as waste and nuclear weapons.
Enrico Fermi (1901-1954).
Nuclear power may in theory be achieved by two methods: nuclear fission and fusion. The first is the energy that is obtained from the fission of heavy nuclei with formation of smaller nuclei and the second corresponds to the energy released when two nuclei come together to form a new nucleus of a greater number of mass.
Most nuclear power plants that are currently used for the production of electricity from nuclear fission are using the uranium-235 isotope as fuel through a chain reaction induced by neutron collision. However, the uranium-238 isotope is the most abundant in nature and represents 99.3% of the total uranium. This isotope rarely undergoes fission and mostly captures neutrons producing plutonium and neptunium without significant release of energy. Therefore, the uranium used in the core has to be artificially enriched in uranium-235 increasing its percentage from the 0.7% that occur in nature up to 3% used in the mixtures of nuclear power plants.
Most nuclear power plants that are currently used for the production of electricity from nuclear fission are using the uranium-235 isotope as fuel through a chain reaction induced by neutron collision. However, the uranium-238 isotope is the most abundant in nature and represents 99.3% of the total uranium. This isotope rarely undergoes fission and mostly captures neutrons producing plutonium and neptunium without significant release of energy. Therefore, the uranium used in the core has to be artificially enriched in uranium-235 increasing its percentage from the 0.7% that occur in nature up to 3% used in the mixtures of nuclear power plants.
Scheme of a nuclear fission chain reaction of uranium-235.
(Credit: Serway&Jewett,Physics for Scientists and Engineers-with Modern Physics, 6th Ed., Thomson-Brooks/Cole, USA)
This percentage and conditions of temperature and pressure control achieved by the nuclear reaction is self-sustaining, or to the fact that at least one of the neutrons released in the fission of being caught by another uranium-235 isotope and not by an uranium-238 isotope.
The following image schematically represents the operation of nuclear power plants that are currently used to produce electricity commercially.
The following image schematically represents the operation of nuclear power plants that are currently used to produce electricity commercially.
Scheme of a nuclear fission reactor.(Adapted from Serway&Jewett,Physics for Scientists and Engineers-with Modern Physics, 6th Ed., Thomson-Brooks/Cole, USA)
At the core of the reactor the nuclear fissions of uranium-235 rise the temperature of the water in the primary circuit which is a closed circuit. This water is at high pressure in order not to boil and serves as a moderator of the speed of the neutrons that are released in order to prevent their fusion with the uranium-238 isotopes.
A nuclear reactor with tipical blue of the Cerenkov radiation. Credit: Wikipedia
The hot water of the reactor is then pumped through a heat exchanger which transfers heat through the walls of the pipe to the water in the secondary circuit. This water reaches boiling point and the vapour moves the paddle of a turbine connected to a generator of electrical power. The steam then passes a condenser that cools it back to liquid state. Water is then pumped back to the secondary circuit where the cycle restarts. The electricity produced by the turbine and generator per mass of uranium-235 is enormous compared to the energy produced by the same mass of fossil fuel.
Though the safety of the nuclear power plants increases with the new generations of reactors, nuclear waste will always be a problem because some of the radioactive waste will endure for thousands of years. On the other hand uranium, as fossil fuels, is a non-renewable source. Therefore it cannot solve the energy problem of the generations to come.
Though the safety of the nuclear power plants increases with the new generations of reactors, nuclear waste will always be a problem because some of the radioactive waste will endure for thousands of years. On the other hand uranium, as fossil fuels, is a non-renewable source. Therefore it cannot solve the energy problem of the generations to come.
Nuclear Fusion Energy
By David Arez, 12ºD
Escola Secundária de Loulé
Tokamak. A reactor of magnetic confinement. (Image credit: General Atomics)
The second is by inertial confinement, bombarding small amounts of nuclear fuel with nuclei that will induce the reaction and using laser beams coming from many directions in order to maintain the plasma confined in a region away from the walls of the reactor.
Inertial confinement using laser beam
The usual reaction is the deuterium-tritium fusion
The neutrons released in the reaction are received by the walls of the reactor and because they aren’t charged they can not be confined. These neutrons carry much of the energy released in nuclear reaction as kinetic energy.
Usually the material used to capture this energy is merged lithium. Lithium suffers neutron capture through the reaction
To confine a nucleus reaction occurs where trials have been conducted in which the kinetic energy of tritium and of the alpha particles is converted into energy inside the lithium merged which will then serve to heat the water connected to a turbine. Another advantage of using lithium is that the tritium is then easily separated once again be used as fuel, and therefore only catalytic amounts would be necessary under ideal conditions.
The advantages of nuclear fission consist of three fundamental aspects:
1. Abundant and cheap fuel (typically deuterium);
2. Impossibility of accidents due to leakage (when temperature gets lower the reaction stops);
3. It is clean and does not produce radioactive waste. The biggest drawback is the shortage of lithium and that therefore new ways of converting the kinetic energy of neutrons are required.
Presently huge efforts are being made to solve the engineering problems that need to be solved in order to make this source of energy a cost-effective and safe source that will hopefully be used in the second half of the twenty-first century.
Escola Secundária de Loulé
Nuclear energy can be obtained from the fission of heavy nuclei with formation of smaller nuclei or by nuclear fusion where the energy the released when two nuclei come together to form a new nucleus of a greater number of mass.
At this moment, major research is trying to build a nuclear reactor that could be used in future to produce nuclear fusion using the conversion of hydrogen into helium, usually from using deuterium as fuel.
The reactions of formation of helium by fusion only occur spontaneously at temperatures of about 108 K. This creates great difficulties regarding the confinement of the material in a reaction chamber, since its not possible to have any solid material at this temperature. In fact, at these temperatures atoms are totally ionized into free electrons and nuclei, forming a state of matter called plasma.
To confine the nuclear reaction site several tests have been conducted in special reactors, and there are two common techniques for confinement.
The first is by magnetic confinement applying magnetic fields to trap the particles in the plasma.
At this moment, major research is trying to build a nuclear reactor that could be used in future to produce nuclear fusion using the conversion of hydrogen into helium, usually from using deuterium as fuel.
The reactions of formation of helium by fusion only occur spontaneously at temperatures of about 108 K. This creates great difficulties regarding the confinement of the material in a reaction chamber, since its not possible to have any solid material at this temperature. In fact, at these temperatures atoms are totally ionized into free electrons and nuclei, forming a state of matter called plasma.
To confine the nuclear reaction site several tests have been conducted in special reactors, and there are two common techniques for confinement.
The first is by magnetic confinement applying magnetic fields to trap the particles in the plasma.
Tokamak. A reactor of magnetic confinement. (Image credit: General Atomics)
The second is by inertial confinement, bombarding small amounts of nuclear fuel with nuclei that will induce the reaction and using laser beams coming from many directions in order to maintain the plasma confined in a region away from the walls of the reactor.
Inertial confinement using laser beam
The usual reaction is the deuterium-tritium fusion
The neutrons released in the reaction are received by the walls of the reactor and because they aren’t charged they can not be confined. These neutrons carry much of the energy released in nuclear reaction as kinetic energy.
Usually the material used to capture this energy is merged lithium. Lithium suffers neutron capture through the reaction
The advantages of nuclear fission consist of three fundamental aspects:
1. Abundant and cheap fuel (typically deuterium);
2. Impossibility of accidents due to leakage (when temperature gets lower the reaction stops);
3. It is clean and does not produce radioactive waste. The biggest drawback is the shortage of lithium and that therefore new ways of converting the kinetic energy of neutrons are required.
Presently huge efforts are being made to solve the engineering problems that need to be solved in order to make this source of energy a cost-effective and safe source that will hopefully be used in the second half of the twenty-first century.
ENERGY PRODUCTION IN PORTUGAL
by Nicolai Manalachi and Ruben Veríssimo, 11º Zi
Escola Secundária de Loulé
CO2 Emissions in 2000 (Credit: New Scientist)
Hydroelectric energy. (a) A dam at Chança stream at Guadiana river. (b) Turbines.
Brinches photovoltaic power plant (Source: http://engenhariacivil.wordpress.com )
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.
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.
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.
•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.
Subscribe to:
Posts (Atom)