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Energy and its transformation - Coggle Diagram
Energy and its transformation
1.Energy sources
The energy we consume has many different users
Household uses:
the operating of electrical appliances, heating systems, hot water systems, heat for cooking and for means of transport.
Industrial uses:
the operating of factories and companies, construction, agriculture and so on.
Energy sources are natural resources from which we obtain different forms of energy that can be transformed for a specific use.
We classify energy sources in several ways:
By availability in nature and capacity for regeneration
Renewable:
Abundant and inexhaustible
Non-renewable
May or may not be abundant
Depleted when we use them up
Cannot be renewed in a short period of time
By origin
Primary
Obtained directly from nature
Examples: crude oil, natural gas, coal, nuclear energy and renewable energies
Secondary:
Resulting from transformation of primary sources
Examples: electricity, some petroleum derivates
By use in each country
Conventional
Most commonly used in industrialised countries
Example: energy that comes from fossil fuels
Non-conventional
Alternative energy sources
In early stages of their technological development
Solar and wind power belong to this group
By environmental impact
Clean or non-polluting
Low environmental impact
Don't generate by-products that pollute the einvronment
Pollutants
Sources that have negative effects on the environment, for example, they might generate by-products that severely pollute the environment
Here is the classification of the energy studied in the unit:
2. Electricity
Electricity is the most widely used form of energy in industrialised societies for two reasons:
It can be easily transformed
into other forms of energy, such as light and heat.
It can be transported long distances
inexpensively and with very little energy being lost
2.1. Electric power plants
Electric power plants are facilities where primary or secondary energy is transformed into electricity. Once electricity is generated, it must be transported to towens, cities or industrial parks
How an electric power plant works
Electrical power plants use an external source of energy to produce electricity. To do this they rely on a
turbine-alternator system
.
The
turbine
converts mechanical energy into the rotating movement of a shaft.
An
alternator
has a fixed part. called a stator, and a moving part, called a rotor, connected to the turbine shaft.
As the rotor shaft moves, alternating electrical current is produced on each of the stator's coils
2.2. Transport and distribution of electrical energy
Electric power plants are usually located far away from the points where the energy is used - for safety reasons, space requirements or physical and geographic considerations.
Electricity
cannot be stored
; therefore, it must be transported to consumption centres. This transport involves several proceses:
Increasing the voltage to 220.000 V or 400.000 V to prevent significant energy loss, due to the Joule effect.
Transporting it by high voltage cables attached to towers
Decreasing the voltage at the electricity substations to 3~30 kV
Distribution to homes, offices, industries and public facilities. During this stage, the voltage is reduced to 230-400 V.
3. Conventional electric power plants
This type of power plant produces most of the electricity that we use.
3.1. Nuclear power plants
This type of plant includes a nuclear fission reactor that produces the pressurised steam needed. Uranium is the main fuel used.
Their main advantage is the high return on their energy production.
Nuclear power plant
3.2. Fossil fuel thermal power plants
At this type of power plant, water is heated in a boiler by the heat benerated from the combustion of a fossil fuel, usually natural gas or coal. The steam that's generated moves the turbine connected to the generator.
Combined cycle power plant
Electricity is generated as a result of two combined cycles, a cycle that uses air and gas, and a conventional thermal cycle. During the first cycle, a gas turbine is used that includes a compressor.
Air is mixed with the gas and is burnt, which generates electricity in the turbine-alternator system. The combustion gases are transported to a boiler, where they transfer their energy to the water during the second cycle.
This type of power plant performs better than those with only one cycle
3.3. Hydroelectric power plants
This type of power plant uses the potential energy provided by the height of the stored water in a dam, converting it into
kinetic energy
. This energy moves the blades of a turbine. Depending on the destination of the water, hydraulic power plants are diveided into two types:
gravity
or
pump
Gravity-driven hydraulic power plants
Water used follows the course of a river and
will not be reused
Pump-driven hydraulic power plants
Water descends into a resevoir located at a lower height, then pumped to a higher resevoir to reuse it.
Non-conventional electric power plants
The environmental problems caused by conventional power plants have led to the creation and development of not conventional or alternative energy power plant
The main
disadvantage
of these power plants are that they generate much less energy, since they use diffuse energy sources
Their
advantages
are that they contaminate much less than conventional power plants, they use renewable sources and they reduce the energy dependence of petroleum and natural gas.
4.1. Wind power plants and wind farms
These power plants use the kinetic energy of the wind to move the blades of a rotor at the top of a tower: this is reffered to as the
wind turbine
Wind farms
are a clean form of generating electricity. However, they can only be installed in places with appropriate wind conditions
4.2. Solar power plants
These plants use the energy from the sun. There are two main types of installations:
photo-thermal
and
photovoltaic power plants
.
Photo-thermal power plant
In this type of power plant, the heat generated by solar radiation produces steam that is used to move the rotor in the generator.
To do this, they use special mirrors, called
heliostats
that reflect sunlight and concentrate it at one point, where it reaches a high temperature.
Diagram of a photo-thermal power plant
Photovoltaic power plant
In these power plants, solar radiation is transformed directly into electricity by panels of
photovoltaic cells
.
Diagram of a photovolataic panel
These power plants consist of large areas of photovoltaic panels.
There are also isolated power plants that are very small in size, which are used to supply electricity to homes in rural areas
4.3. Geothermal power plants
These plants use the heat found at deep levels in the earth. This heat may reach the surface in form of steam, gases or hot water.
Geothermal energy
may be used
directly
- for hot water and heating industrial use and so on - and
indirectly
- the heat generates steam, which produces electricity.
Geothermal power plant in Iceland
4.4. Biomass thermal power plants
Biomass consists of all organic compounds that are produced through natural processes. They may come from the following sources:
Forestry and agricultural waste
Spescific crops such as sunflowers and sugar beat
Waste from agri-food industries
Biomass is subjected to different physical and chemical processes in order to produces fuel such as charcoal, alcohol or biogas.
This type of fuel is burnt at biomass power plants. The steam that is generated moves this turbine:
Diagram of a biomass power plant
These power plants produce energy from waste that has no other potential uses.
Biomass thermal power plant
4.5. Ocean power plants
These power plants use the energy from the seas and the oceans. The concept is to use three types of energy from the sea
The mechanical energy from the tides
The mechanical energy from the waves
The energy from the ocean's thermal gradiant
These power plants are still in the experimental phase and their level of production is still very low.
5. Environmental impact
The building and operating of an electrical power plant results in an ecological change in that region. This is due both to the construction of the necessary infrastructure and the waste that this activity generates
5.1. Environmental impact assesment
As part of a technical project, it's mandatory to carry out an
environmental impact assesment
to find out what changes it would provoke in the environment
An environmental study must also assess both the economic and social consequences of the project in the area, to decide whether or not to go ahead with the plan.
The main characteristics of each type of power plant and the impact they have on the environment are shown below:
5.2. Environmental impascts
Energy cosumption is preceeded by a long process, consisting of sevral stages, each of which has an environmental cost.
Extraction of natural resources
The exploitation of fossil fuels and nuclear power means the depletion of resources, which makes it necessary to find new ones.
Fuel extraction processes are sometimes harmful to the environment. In particular, timber extraction has led to the disappearance of large areas of forest, a process that is continuing even today.
Fuel transport
Oil is transported by means of oil pipelines and oil tankers
Oil pipelines can suffer accidents caused by nature or human error, which result in uncontrolled spills
Oil tankers can have accidents at sea, with the risk of oil spills. Some spills have caused oil slicks that have taken years to clean up and dissipate and have affected the lives of many plant and animal species
Sinking of the Amoco Cádiz oil tanker (1978)
Electricity generation
Large hydroelectric power plants require water resevoirs covering large areas, which profoundly change the natural cycle of rivers, flood large land areas and destroy ecosystems, in addition to increasing the risk of accidents
Conventional thermal power plants can cause numerous problemas and environmental hazards
They produce air pollution - suspended particles, CO2, heavy metal moleculses and so on
They emit large ammounts of CO2, which increases the greenhouse effect.
They emit sulphur dioxide and nitrogen oxide that cause acid rain, which is very harmful to the environment
The water used in the cooling system is returned to the environment while it's still warm, which affects both animal and plant life.
Nuclear thermal power plants are accompained by the risk of nuclear accidents and the problem of nuclear waste, somo of which remain dangerous fo thousands of years
Large dams profoundly change the natural cycle of rivers.
Final energy use
The fuels we use in vehicles and heating systems emit gases and particles similar to those generated by conventional thermal power plants.
When we turn on an electric appliance, we're consuming energy that has already caused several environmental problems during its extraction, generation and transportation
5.3 Waste treatment
To reduce the waste generated by thermal power plants, as well as their effects, several measures can be taken:
Install special filters on the pipes at the power plant to capture some of the gas pollutants
Use coal with a low sulphur content, to reduce acid rain.
Mantain and increase the size of large forested areas, since they absorb carbon dioxide
Waste from nuclear power plants is stored in drums with thick sides tht do not let the nuclear radiation escape. These are then stored in ocean trenches and undergound
The use of ocean trenches has its own problems, because there's the risk of the drums corroding and the radioactive material leaking out of them.
5.4 Some solutions
Here is a summary of different possible solutions to alleviate some of the environmental problems described
Efficiency
energy efficiency policies increase efficiency of everyday appliacnes and devices
noticeably reduce the energy we consume
Examples: low fuel consumption cars, electric cars, better home insulation
Energy diversification
use of renewable energy sources is fundamental
objective is to produce a large part of our electricity through alternative power plants.
Energy savings
essential to reduce the consumption of all forms of energy - without seriously affeting quality of life
adoption of more environmentally friendly habits
Examples: using public transport or bicycles, changing consumption habits.
