Science & Technology in Action

12th Edition

Generating renewable energy


Jnr Science Cert
The term ‘sustainability’ relates to the need to ensure that we do not deprive future generations of essential energy resources by using them up or by damaging the environment in an irreversible manner. The obvious way of ensuring sustainability is the use of renewable resources.
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Lesson excerpt

What is energy? 
We use the word energy in many different ways and are not too troubled about defining it. However, in physics, it has a specific and precise definition. To a scientist energy is the ability to do work. ‘Work’ is defined as being done when a force acts on an object, accelerating it over a distance. 

Power is then defined as the rate of doing work. For example, a car that travels a kilometre more quickly than another is more powerful i.e. it has used the same energy in a shorter interval of time. 

There are many forms of energy including potential, kinetic, elastic, electric, magnetic, chemical, thermal and nuclear. The law of conservation of energy tells us that energy can neither be created nor destroyed, but it can be transformed from one type to another. The challenge is to develop ways of transforming energy that already exists into forms that are more useful. 

In this lesson we discuss some of the technologies used by the ESB to transform energy into the valuable product called electricity

Generating electricity - the fundamentals 
An electrical generator is usually a rotating device that continuously moves an assembly of conductors through the magnetic field. Obeying Faraday’s law of electromagnetic induction, this movement creates the electromotive force (EMF) necessary to drive an electric current. The generator is rotated by some form of engine, often a turbine. Of course, this turbine must be driven by some other source of energy. It is these sources of energy that form the topic of much debate and concern. 

Burning fossil fuels 
Fossil fuels, such coal, oil or natural gas, are hydrocarbons and are easily burned. These fuels are commonly used as sources of heat in thermal power stations in which heat energy is converted into electricity. The heat either converts water into steam or ignites fuel (similar to a combustion engine) which then drives a turbine (mechanical energy). 

When fossil fuels are burned they produce carbon dioxide (CO2) and nitrous oxide (N2O), These are greenhouse gases that contribute to the modern problem of global warming. In addition, fossil fuels take tens of millions of years to form naturally and are now classified be non-renewable. Accordingly, the focus is now on renewable energy sources i.e. sources that are replenished naturally over a reasonable period of time. These include water, wind, the sea, the sun, heat from the earth itself and organic matter (biomass). 

True or False?

  1. Energy cannot be created but can be destroyed. false
  2. Heat cannot be used to generate electricity. false
  3. All types of electricity generation are not equally efficient. true
  4. There is not enough sunlight in Ireland to use solar energy. false
  5. Most electricity is generated from renewable sources. false
  6. The sea could be an important source of energy in the future. true
  7. ESB does not manage any wind farms. false
  8. Wind will not be a significant source of energy in the future. false
  9. In a hydro station, the kinetic energy of moving water is converted to electrical energy. true
  10. The SI unit of energy is the erg. false
  11. A kilowatt-hour is a unit of power. false
  12. One kilowatt-hour is equal to 3,600,000 joules. true

Glossary of terms

a compound composed only of carbon and hydrogen
photovoltaic cell
a device that
electric current
a flow of electric charge. This can be a flow of electrons (in metals) or ions (in the case of gases and ionic solutions).
global warming
a gradual warming of the Earth's atmosphere, caused by the accumulation of gases from the burning of fossil fuels
a material that conducts electricity; generally applied to good conductors such as metals
A material with electrical resistance between those of conductors and insulators.
magnetic field
a region of space around a magnet in which it can exerts a force on magnetic material
a renewable fuel derived from plant or animal sources 
a wheel with fins or vanes arranged so that it can be rotated by a flow of gas or liquid
changing the speed or direction of a body
carbon dioxide
CO2 – A gas found in the atmosphere that is used in photosynthesis and produced by respiration
fossil fuel
coal, oil or natural gas that result from the fossilisation of ancient plants or animals
Ethanol derived from biological sources
fuel made from plant oils that can be used in a conventional diesel engine
in simple terms it is a push or a pull; a single force acting on a body causes it to accelerate: F=ma
organic matter
matter formed from the remains of dead plants and/or animals
once used it is not replaced takes a long time to replace
nitrous oxide
one of the oxides of nitrogen; dinitrogen monoxide, N2O; sweetish, colourless, non-flammable gas, formerly used as an anaesthetic; also known as "laughing gas"
symbol Ω; the SI unit of resistance; if the resistance between two points is one ohm then a potential difference of one volt across the resistance produces a current of one ampere
the capacity to do work
radioactive decay
the change (or series of changes) brought about when radioactive isotopes emit alpha or beta particles (and occasionally neutrons); in the process they may eventually form non-radioactive isotopes
kinetic energy
the energy a body has because of its motion; it is proportional to the velocity squared: K.E. =1/2(m.v2)
photovoltaic effect
the generation of a voltage by exposure to light; the operating principle of solar cells
electromagnetic induction
the inducing of an emf in a conductor when it cuts, or is cut by, lines of magnetic force. The induced emf E is equal to the rate of change of flux, E = d(phi)/dt
the phenomena associated with moving electric charges
the product of a force and the distance over which the force acts; it is measured in joules (1 joule = 1 newton metre)
the rate at which energy is transformed
the unit of electromagnetic energy; single quantum of radiant energy.
The unit of measure that indicates how much electricity flows through a conductor
renewable energy
The use of energy sources that can be regenerated; e.g. timber or other biofuel
typically, material of biological origin that can be used directly or indirectly as a fuel
electromotive force
(emf) electric potential or voltage; measured in volts; it is the energy per unit electric charge (1 V = 1 J/C)
Faraday’s law
the emf is proportional to the rate of change of magnetic flux
full load hours
the number of hours during which the wind is consistently suitable for a turbine
High Temperature Geothermal Energy
geothermal water that is hotter than 160°C
the production of electricity by a flow of water
the production of electricity by a flow of water
law of conservation
(of energy) energy cannot be created but only changed from one form to another
mechanical energy
the energy a body has because of its position (i.e. potential energy) or its motion (i.e. kinetic energy)
potential energy
the energy a body has because of its position
solar cell
a device that produces electricity when light shines on it
thermal power station
a power station that uses a heat source to generate electricity
tidal power
the use of the movement of the tides (typically twice daily) to generate electricity
wave power
the use of the waves to generate electricity
SI units
the international system of units (Systeme International); essentially the metric system