Conventional Energy Sources: Coal, Oil, and Natural Gas
Item 1. Conventional Energy Sources
Need for Energy
Energy is conceived as the ability to produce work. All forms of energy come from, have a direct or indirect, source: the Sun. The Sun is the first and most important energy source. Humans have learned to avail themselves of other energy sources like wind (construction of windmills), or kinetic energy of water (building watermills, moving simple machines, etc.).
New energy sources (solar photovoltaic, geothermal, etc.).
Manifestations of Energy
Potential energy is the energy that a body possesses by virtue of its position or its status.
Kinetic energy is the energy that a body possesses by virtue of its movement.
These forms of energy can be harnessed or can be transformed into other forms of energy.
Energy Sources
Renewable sources: those which nature regenerates quickly and from which we get energy continuously.
Non-renewable sources: those found on Earth in limited quantities and are exhausted with their use.
Conventional sources: those that generate the most useful energy in a country.
Non-conventional sources: those that, due to lack of technological development or high costs of extraction and exploitation, do not generate a large amount of useful energy.
Coal
Coal is a solid black mass formed from plants that were buried and underwent a process of carbonization.
Types of Coal
- Peat: the most recent type of coal and can be boggy in places. 50% carbon. 4000Kcal/Kg. Used in the production of fertilizers.
- Lignite: coal formed in the Secondary and Tertiary eras. 70% carbon. 5000Kcal/Kg. Used to obtain dry products through distillation.
- Coal: the most used type of coal. It was formed in the primary era. Between 75% and 90% carbon. 7000Kcal/Kg. Used for the extraction of coking coal.
- Anthracite: the oldest type of coal and is probably metamorphosed. 95% carbon. 8000Kcal/Kg.
Extraction Process
Open-cast mines can extract the entire coal seam up to 100m deep. Disadvantage: serious environmental and landscape impact.
Underground operations are the main form of mineral extraction. They can reach depths of up to 1200m. Two methods:
- Method of proceedings in chambers and pillars.
- Method of longwall mining.
Coal Combustion
During coal combustion, several pollutants are released into the atmosphere. These substances are responsible for acid rain and the greenhouse effect.
Oil
Oil is a natural mineral oil of blackish-brown color formed by hydrocarbons (carbon and hydrogen), which originates from the remains of aquatic organisms.
Oilfields
Oilfields are usually located between layers of gaseous hydrocarbons. When drilling, gas pressure causes the oil to flow out.
Refining Process
Fractional distillation continuously heats the oil to 400°C and passes it through a gas fractionation tower. Various products are obtained:
- Residues: formed by solid bitumen, asphalt, and waxes. Used in road construction.
- Heavy oils: condensation at 360°C.
- Gas oil: condensation between 250 and 350°C. Calorific value of 11120Kcal/Kg.
- Kerosene: 280°C.
- Gasoline: a mixture of liquid hydrocarbons and some sulfur and nitrogen compounds. Condenses between 20 and 160°C.
- Gas: the product containing the gas that did not condense in the crude oil.
Natural Gas
Wet gas: gas found with oil fields.
Dry gas: gas found without oil.
Natural gas has a calorific value of 11500Kcal/m3.
Gas from Coal
Obtained from the dry distillation of coal. It is composed of hydrogen, methane, and carbon monoxide. Power needed: 4200Kcal/m3.
Liquefied Petroleum Gases
- Propane gas: has a calorific value of 24000Kcal/m3.
- Butane gas: has a calorific value of 28500Kcal/m3.
Coal Gas
Obtained by incomplete combustion of coal coke. 1500Kcal/m3.
Acetylene
Obtained by the reaction of water with calcium carbide. Used in welding torches.
Power Plants
These are complex installations where thermal energy is used to heat water and turn it into steam. This steam passes through a turbine, which, due to its motion, produces electricity.
Appropriate Thermal Fuel
The feeder handles the fuel proportionally to the burn rate. The furnace is an enclosure where fuel is burned. The smoke duct leads the fumes to the outside.
The Cycle of Steam
The boilers contain water that must be transformed into steam. The primary reheaters evaporate any remaining liquid particles leaving the boiler. The turbines take advantage of the high-pressure kinetic energy of steam. The pump sends extracted water towards economizers.
The Cooling Circuit
A pump provides water to the condenser. If there is abundant water, the water is cooled by central cooling towers.
Power Generation
The mechanical energy is transmitted to a turbo-alternator, which transforms it into three-phase alternating current. The network sends the power to a transformer, which increases the voltage. It is transported through the high-voltage network.
Nuclear Power
It is energy released as a result of nuclear reactions. In fission reactions, a heavy nucleus disintegrates into two lighter ones. In fusion reactions, two light nuclei fuse to form a heavier nucleus.
Use of Nuclear Energy
The raw material used is natural uranium, but enriched uranium oxide and uranium or plutonium are also commonly used. The facilities designed to carry out this procedure are called nuclear power plants.
Nuclear Power Plants
The reactor is the part of the facility where nuclear reactions occur. The fuel is usually uranium and plutonium. The reactor features control rods.
Types of reactors:
- Pressurized-water reactors: pressurized water circulates through a closed circuit and transfers heat to another circuit.
- Boiling-water reactors: the steam generated in the cooling circuit is used to directly power the turbine-alternator groups.
Safety in Nuclear Power Plants
Types of radiation:
- Alpha rays are formed by helium nuclei.
- Beta radiation is formed by electrons.
- X-rays are electromagnetic in nature.
- Gamma rays are more penetrating than X-rays.
- Neutrons are the most penetrating radiation.
Safety elements:
- The concentration of uranium-235 is limited to about 2.5%.
- The design of the plant ensures that radioactive material is protected by multiple barriers.
- Plants are equipped with security systems.
- Regular inspections are conducted.
- Radioactive waste is stored and monitored.
Environmental Impact
- Landscape impact.
- Thermal discharge.
- Emission of water vapor.
- Noise.
- Radioactive emissions.
Hydropower
It involves harnessing the energy of falling water from rivers. It is carried out in a hydropower plant.
Characteristics of a Hydroelectric Plant
Parts:
- Dam:
- Concrete dam:
- Gravity dams: the water pressure is counteracted by the volume of concrete.
- Simple arch dams: distributes the water pressure towards the abutments.
- Multiple-arch dams: it is divided into several openings that are closed by means of gates.
- Buttress dams: reduce the volume of concrete required.
- Concrete dam:
- Derivation channel: a conduit that channels water from the reservoir.
- Pressure chamber: the junction of the bypass channel and the pressure piping.
- Pressure piping: responsible for driving the water to the turbine chamber. Steel pipes are built with rectangular steel plates that are formed into a cylindrical shape. Asbestos-cement pipes are used for low power installations. Reinforced concrete pipes are used for large flows and height differences up to 40m.
- Chamber of turbines:
- Turbine: responsible for transforming the kinetic energy of water into kinetic energy of rotation.
- Alternator: transforms the kinetic energy into electricity.
- Pelton turbine: high-pressure turbine. It has a blade on which a jet of water falls.
- Francis turbine: medium-pressure turbine. The water is conducted to the runner by a distributor.
- Kaplan turbine: low-pressure turbine. The runner consists of a propeller with adjustable blades.
- Open chambers: are communicated with the outside and are only used for heads up to 15m.
- Closed chambers: are not communicated with the outside, and the water from the pipe is forced into them.
- Drainage channel: responsible for returning the used water to the riverbed.
- Transformers: increase the voltage from 11,000V or 20,000V to 200,000V.