1.- ENERGY AND WORK
Energy is a property of matter linked to the idea of transformation and movement. Energy is constantly being transformed into other types of energy, as stated in the law of conservation of energy, which says that energy is neither created nor destroyed, but rather transformed into other types of energy. Nevertheless, part of the energy is degraded or lost or in other words, becomes non-usable energy, which cannot be converted into work as a product of its transformation.
Physics defines energy as the capacity of a body to perform work. It must displace objects, even on a small scale, to be considered as such. In Technology, energy interests us as a natural resource that we use and transform.
In theory, one type of energy can be transformed into any other type of energy. However, for technological reasons, this is only possible in some cases. For example, it is possible to obtain electrical energy from nuclear energy. Nevertheless, is not possible for this process to be reversed.
Energy can be classified into six types:
2.- RENEWABLE ENERGY
Renewable energy sources are those that come from sources that cannot be exhausted, at least for a reasonably long period of time. This permanent existence may be attributed to Either the ability to regenerate or the amount of energy the source contains.
SOLAR ENERGY
All forms of energy found on Earth come directly or indirectly from the Sun. Two different types of solar panels are used in order to harness solar radiation:
- Photovoltaic solar panels are made up of materials capable of producing electricity when the Sun’s rays hit them. Their properties change in the presence of light, and as result of a chemical reaction, these materials produce direct current electricity.
- Thermal solar collectors are used to heat water, which can either be used directly or indirectly, upon making turbines rotate and thereby generate electricity.
Solar collectors can be handcrafted at a relatively low cost, whereas manufacturing photovoltaic panels requires more sophisticated technology.
WIND ENERGY
Wind energy comes from the wind. Humans have been using it for hundreds of years to propel sailboats. It was also used to move the blades of windmills, which ground olives or grains to obtain oil and flour, respectively.
Modern day technology has presented us with the opportunity to once again harness wind energy, however this time, to produce electricity.
Wind farms are located in areas in which the average annual amount of wind is stable. As such, wind turbines are located on platforms a few hundred meters off the coast, in order to take advantage of the constant sea breeze.
Wind speed influences the start-up and shut-down of wind turbines. On average, wind at about 3 m/s is needed for start-up and they must be shut-down at approximately 20 m/s.
Although the system is able to resist much higher speeds, this maximum working velocity is set for safety reasons and in order to prolong the useful life of the various parts.
Wind turbines operate as follows:
1 The blades turn, propelled by the wind and transfer their movement to the shaft.
2 The movement of the shaft passes to the multiplier, where an adequate turning speed for the generator is reached.
3 Then, the generator transforms this mechanical energy into electrical energy.
4 The energy produced moves through conductor cables to a transformer and from there, flows to the distribution network.
How do wind turbine work?
HYDRAULIC ENERGY
Water has a certain weight. As a fluid it is able to move and adapt to the volume that contains it. A river is an example of this behaviour of water.
River springs are usually found high up. They flow down the landscape as a result of gravity and travel through the earth until they finally reach the sea. At various points along the river, the water is dammed, so that an enormous mass is accumulated. This mass is then released from the top of the dam. At the highest point of elevation, the standing water has acquired potential energy. As it is released through the dam, it loses that potential energy, which transforms into movement energy or in other words, kinetic energy. This potential energy can be turned into electrical energy in hydraulic power stations, by means of the turbine-alternator connection.
TIDAL ENERGY
The force of gravity that the Moon and the Sun exert on the Earth causes sea levels to increase and decrease in constant cyclical movement. This movement can be transformed into electricity. However, in order to use tidal movements to produce energy, there must be a significant difference in sea level between high tide and low tide. Currently, in order for tidal movements to prove profitable making it worth building a tidal energy power station, there must be at least a five meters height difference between the high tide and low tide, thereby meaning tidal energy facilities can only be installed in very specific areas of the coast.
There are other ways to extract energy from the sea, for example, from sea currents, which are harnessed by means of submarine generators very similar to tidal stations. Various systems that harness wave movement are also being researched. This is known as wave energy.
Question
What do you think is the greatest disadvantage of the power station described above?
GEOTHERMAL ENERGY
The Earth is made up of several layers. The outer layer or crust is between five and seventy five kilometres deep. It is formed by tectonic plates that drift over the mantle. The second layer is the mantle, which reaches almost 3 000 kilometres in depth and represents almost 90 % of the Earth’s volume. Temperatures in the mantle range between just over 500 °C, where it is in contact with the crust, and up to almost 3 000 °C in its transition zone to the core.
Finally, we have the core, which is mainly composed of iron and nickel. Thermal processes take place inside the core. Given the irregularities of materials in the mantle, magma tends to rise like a chimney towards the surface of the Earth. These are called hot spots, which can form archipelagos like Hawaii.
Volcanoes are one of the consequences of materials being conducted from the inside the Earth towards the surface.
The internal energy of the Earth also produces thermal waters, as a result of underground water being heated directly by conduction of the Earth’s heat.
This energy is mainly concentrated in areas with high volcanic activity. The heat from the Earth is harnessed through thermal power stations. There are two types of thermal power stations that use geothermal energy: hot water deposits and hot dry rock.
- Hot water deposits usually have two wells: one in which water heated by the thermal source is extracted and another to inject cold water to be heated and returned, by differential pressure, to the first well.
- In hot dry rock deposits, a pipe that passes through shallow hot stones and rocks is installed. Water circulates through this pipe and is heated when it passes through the heat source.
In both cases, the steam obtained circulates to an exchanger. Here, the heat is extracted from the fluid to be either used as local central heating or to move a steam turbine that can turn the shaft of an alternator, thus generating electricity.
BIOMASS
Biomass is matter obtained from living organisms.
Natural biomass is found in nature, without human intervention.
Residual biomass is produced by human activities, such as agricultural and livestock waste, garden cuttings and waste from lumber industries, etc.
Manufactured biomass is created by energy-producing agricultural and forest crops from which fuel is produced.
In order to obtain energy from biomass, it must be treated in one of the following ways:
Combustion: the biomass is burnt and the heat generated by combustion is used to heat water, produce steam and move turbines that generate electricity. This is the oldest treatment method, which uses the biomass directly in its solid state.
Pyrolysis: the biomass is subjected to high temperatures in a furnace without oxygen, which produces coal with a low calorific value.
Gasification: this process is very similar to pyrolysis, however aims to obtain the gas released from the partial oxidation of the biomass.The gas obtained does not have a high calorific value either.
Alcoholic fermentation: this process transforms sugars, starches and plant cellulose into ethanol or methanol. In both cases, the product obtained is called bioalcohol. This alcohol can be used as fuel.
Methane fermentation: is a complex process carried out in several stages in the absence of oxygen, using livestock waste (manure) and plant waste (shavings and sawdust). The end product is called biogas and is so-named in order to distinguish it from the substance obtained in petroleum fields, although this is also methane.
3.- NON-RENEWABLE ENERGY
COAL
Coal is a rock made mostly of carbon. It also contains sulphur, oxygen, hydrogen and nitrogen in varying amounts. It is formed through plant waste being buried under a layer of oxygen poor mud. The pressure, lack of oxygen and temperature that the waste was subjected to over long periods of time determines the rock formation. There are several types of coal, each with different qualities.
Given its sedimentary origins, with the exception of peat turf, which is found at ground level, coal can only be extracted mechanically from mines, where galleries are excavated as the rock is extracted.
Although most of the coal extracted is intended for direct combustion, the most significant uses of coal are as follows:
- Generating electrical energy in thermal power stations by burning it or in combined power stations, where the coal is initially processed through gasification.
- In the iron and steel industry, it is used to manufacture steel by using coking coal to maintain the temperatures required in the blast furnace.
- In the construction industry, it is used to manufacture bricks and cement made in blast furnaces, which require fuel with a high calorific value.
OIL
Oil is currently the most commonly used source of energy. Its origins are similar to those of coal, although oil is produced by the decomposition of algae and animal remains (mainly zooplankton).
This process of decomposition turns organic matter into a kind of hydrocarbon soup, which contains other chemical elements that must be filtered out.
Oil is found underground, in pockets formed by impermeable rock that prevent it from dispersing. It is common for a bubble of natural gas (mainly methane) to form above it, which helps those looking for deposits to find them. However, the search for oil today consists of finding deposits of impregnated rock, rather than detecting a pocket of liquid oil, since the largest deposits have been exhausted.
Newly extracted oil, known as crude oil, cannot be used directly. It must firstly be distilled in order to obtain by-products.
This process is carried out in refineries, where the oil is placed in a column, called a distillation column or distillation tower, while is heated at the base. The inside of the tower is divided into a series of interconnected trays. The heated oil begins to boil and evaporates, the gases rise through the tower and the trays collect the different substances that condense as the temperature decreases. The highest temperatures are found on the lower level, between 400 and 500 °C. From there, the fraction of heavier asphalts is extracted. The most volatile gases and other products are found in the upper trays at temperatures close to room temperature.
NATURAL GAS
Natural gas is a type of fuel closely linked to oil. In fact, it is created in the same way.
Throughout the 20th century, natural gas extraction formed part of the first stage of oil extraction. It was the first product that surfaced in a deposit.
Natural gas consists of a mixture of gases, predominately composed of methane gas, the simplest form of hydrocarbon and what is created in all organic material decomposition processes.
Of all fossil fuels, natural gas is the least polluting and emits the lowest levels of carbon dioxide into the atmosphere when burnt. This is due to its specific chemical composition, since methane contains one carbon atom and four hydrogen atoms in each molecule.
The rest of fossil fuels, such as oil, are made up of several long chain molecules. Therefore, when natural gas is burnt, the proportion of CO2 emitted into the atmosphere is lower than when the same amounts of other fuels are burnt.
Natural gas is transported and distributed through large pipes called pipelines, which can cross several countries.
It is also transported via the sea, where the gas is confined in spherical deposits called methane tankers. Inside the deposits, the gas is found in its liquid state at a high pressure and controlled temperature. At the destination port, the deposits are connected to distribution pipes to distribute the gas through the consumption areas.
SHALE GAS
Shale gas or unconventional gas is found in geological areas with low permeability, which contain a large amount of slate and schist, which is why special techniques are required to obtain it.
Due to the oil shortage, we have resorted to obtaining hydrocarbons, both liquid and gas, by applying the extraction technique known as hydraulic fracturing or fracking.
It is currently estimated that over 50 % of natural gas deposits are obtained by fracking.
This process consists of drilling a well and injecting water with sand and chemical additives into it at a high pressure. The rock breaks and then the impregnated areas can be accessed and the gas and crude oil found inside the porous rock can be extracted.
The procedure is highly controversial from an environmental standpoint, especially since it contaminates nearby aquifers, gives off greenhouse gasses and could potentially cause earthquakes and pose health risks to those living in areas close to the deposits.
4.- NUCLEAR ENERGY
The advantages of nuclear fusion are inherent to the process itself:
c) There is no risk of radioactivity, nor is radioactive waste generated.
The disadvantage is that fusion has still not been completely controlled, maintained over a long period of time and at a reasonable cost.
For more information visits the following Websites:
4.- NUCLEAR ENERGY
NUCLEAR FISSION
Nuclear fission is a reaction that takes place when a free neutron collides with the nucleus of a fissile element, such as uranium or plutonium.
As a result of the collision, it fissions or brakes. Two new atoms of other components are formed, and three neutrons and a large amount of energy are released. The new neutrons collide with other nearby uranium or plutonium atoms. This is called a chain reaction.
Uranium and plutonium are metallic elements found in the actinides group.
Uranium is found in small amounts in nature. There are only a few countries with deposits of this mineral. It is used as fuel in nuclear fission power plants.
Plutonium is even harder to find in its natural form. It appears after fission reactions take place in nuclear power plants, when some of the neutrons released transform the uranium nuclei into plutonium.
Nuclear energy produces approximately 20 % of the electrical energy consumed in Spain. This percentage is even greater in other countries in the European Union.
However, nuclear energy presents two major disadvantages. Firstly, uranium is a very limited resource on the planet and tends to be exhausted quickly. Secondly, nuclear waste is deadly. It has an active life of thousands of years and must be stored safely in order to avoid catastrophes similar to those that occurred in the nuclear power stations in Chernobyl (Ukraine) and Fukushima (Japan).
As a result of the collision, it fissions or brakes. Two new atoms of other components are formed, and three neutrons and a large amount of energy are released. The new neutrons collide with other nearby uranium or plutonium atoms. This is called a chain reaction.
Uranium and plutonium are metallic elements found in the actinides group.
Uranium is found in small amounts in nature. There are only a few countries with deposits of this mineral. It is used as fuel in nuclear fission power plants.
Plutonium is even harder to find in its natural form. It appears after fission reactions take place in nuclear power plants, when some of the neutrons released transform the uranium nuclei into plutonium.
Nuclear energy produces approximately 20 % of the electrical energy consumed in Spain. This percentage is even greater in other countries in the European Union.
However, nuclear energy presents two major disadvantages. Firstly, uranium is a very limited resource on the planet and tends to be exhausted quickly. Secondly, nuclear waste is deadly. It has an active life of thousands of years and must be stored safely in order to avoid catastrophes similar to those that occurred in the nuclear power stations in Chernobyl (Ukraine) and Fukushima (Japan).
Nuclear fusion mainly consists of two atoms joining together to form one. As is the case inside stars, hydrogen is the element used as the base material for fusion. This fusion releases an enormous amount of energy.
In order to fuse two atoms together, the matter must be confined in a small space and the temperature must be extremely high, at around tens of millions of degrees, so that the material is in a plasma state.
In order to fuse two atoms together, the matter must be confined in a small space and the temperature must be extremely high, at around tens of millions of degrees, so that the material is in a plasma state.
The advantages of nuclear fusion are inherent to the process itself:
a) The most abundant element on Earth, hydrogen, is used as the base material.
b) The fusion power station is stopped the moment the plasma has cooled down. Therefore, the confinement of the matter is no longer closed. There are much more safety measures in these power plants than in current fission power stations.
c) There is no risk of radioactivity, nor is radioactive waste generated.
The disadvantage is that fusion has still not been completely controlled, maintained over a long period of time and at a reasonable cost.
For more information visits the following Websites:
