Energy and its Energy and its transformationstransformations

Tecnology 3Tecnology 3rdrd ESO ESO

Index• Definition• Types of energy• Electricity• Power stations• Energy efficiency

What is energy?• We define energy as the capacity of performing any activity.The Junits of energy are: J(joule), cal (4,15 J),

kw·h(1000J/s*3600s=3 600 000 J)• We define power as the capacity of performing work in a unit

of time: P=Energy produced or consumed / timeUnits for power: W (watt), kW, CV or hp (1 C.V. = 735,5 W)

Index

Types of energy Renewable?Origin

Renewable Non Renewable

SUN

Wind Fossil fuelsHydroelectric CoalPhotovoltaic, sun thermal Gas

Seas OilBiomass

EARTH SUW (RSU) NuclearGeothermal fuels

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ElectricityElectricity is an extremely

useful form of electricity because:

1. It is easy to produce and transform

2. It is easy to transportElectricity is produced in

power stations, which can be: Thermal, hydroelectric, wind farms, solar cells…

Production of electricityTo produce energy we use an

alternator formed by• A turbine which rotates

debt to other energy(wind, water vapour)

• A generator, formed by a rotor connected to the turbine and an stator. Bobines are holed along the stator and magnets conductors along the rotor. The movement of the rotor induces the production of a voltage, and thus electricuty, on the stator Index

Thermal stations• Thermal stations generate vapour at high pressure) to

push the turbine blades of the alternator. Normally fossil fuels (coal, gas-oil, gas) are burnt to generate vapour

• They are pollutant, non renewable, but very effective

Nuclear power stations• Nuclear power station are thermal stations

where the vapour is generated with the heat from nuclear reactions: Uranium, plutonium

• They are pollutant, non renewable, but very effective

Hydroelectric station• Sun evaporates water from seas. This

provoques rain and craetes rivers, whose water is stored with dams. The energy of this water is used to generate electricty

• This is renewable, non pollutant but also destroys valleys and depends on the climate.

Wind farms• Wind farms are groups of aerogenerators, placed over

mountain tops, which convert wind into electricity. The devices use a huge turbine(fan) of 60 m (diameter)

• This energy is renewable, non pollutant and quite reliable, for wind is countiuous over muntains. The pollution is visual. The generators can be dangerous for certain birds

Sun cells• Sun rays release the

electrons of certain metals when they hit them. This produces a flow of charges: Photovoltaic effect

• This energy is renewable and non pollutant, but the materials for procing sun cells are extremely pollutant and the effiency is low

• This energy is used to support conventional electricity supply or when it is impossible to connect to the electric grid (satellites)

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Distribution of energy

• Distribution of electricity• Distribution of fuels

Distribution of electricity

Electricity is produced in power station far away from citis or industries (consumption centres)

• We use a grid to transport electricity.• Two kinds of grid are used: Transport and distribution grid• To diminish the amuont of power wasted because of the resistance of the wire,

(Pw=R·I2), tension is extremely high, so I is very low (I=Pd/V). • High tension is only available in the transport grid. The distribution grid, which

brings electricity to houses and industries is transformed to lower values to help electrical accidents (fires, explosions)

Distribution of fossil fuels

• Coal is produced in mines and oil and gas are found underground (oil wells)

• Coal is distributed with ships, trains or lorries to the cosumption centres

• Gas and oil are distributes with ships or pipes

Energy effiency

• Energy production and consumption is harmful for the enviroment (it is pollutant, and spends a lot of resources).

• We define efficiency as Efficiency=Converted

energy/Consumed energy• The most efficient a device is,

the better for our enviroment and for ourselves

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