The advantages and disadvantages of nuclear power and fossil fuels and which is the better source of energy for the near future? Is it a long-term solution? Is there a better solution currently under development?

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The advantages and disadvantages of nuclear power and fossil fuels and which is the better source of energy for the near future? Is it a long-term solution? Is there a better solution currently under development?

This report aims to discuss the advantages and disadvantages of the two main methods of electricity production, and to decide on which method seems to be the best for large scale electricity production in the future, based on each method's economical and environmental implications.

The most widely used fuel in power plants is coal.1 Research into alternative fuel sources stems from concerns about the global environment The problem about choosing whether or not to completely 'go nuclear' or carry on using fossil fuels stems from many environmental and economic factors. The ideal power source will produce the largest amount of energy achievable at an affordable cost, with as little environmental pollution as possible. In this report, I will discuss the advantages and disadvantages of fossil fuels and nuclear power, and which comes the closest to fitting this 'ideal' power source model. From this I will speculate on the best way forward for large-scale energy production. When I have drawn conclusions concerning these two methods of energy production, I will then discuss the energy production ideas that are currently being researched and developed by physicists, and whether or not these ideas are better than current ideas and potentially the energy resource that fits the 'ideal' model perfectly.

Background information

Most power plants around the world are steam-electric plants. This means that the energy created is produced by great deals of steam turning the blades of a giant turbine, which spins the shaft of a huge generator. Inside the generator, coils of wire and magnetic fields interact, and electricity is created.1

All steam-electric power plants produce electricity in just this way. What changes is whether using coal, natural gas, oil or nuclear energy to heat the water to produce the steam.

In a fossil-fuelled plant, you burn coal, natural gas or oil to heat water in a boiler, turning it into steam to turn the turbine. Of these three, coal is the most widely used.

In a nuclear plant, you don't burn anything at all. Instead, you split atoms of uranium, which creates the heat that turns the water into steam. Splitting atoms is called fission.

There are other kinds of power plant used around the world but they are generally considered inappropriate for large-scale power production. Despite them being 'environmentally friendly,' their cost often out-weights their energy return. A short table summarising the reasons why this is the case is displayed below.2

Whatever the fuel, the method used to generate electricity is almost identical all over the world.

How an electricity generator works

Both nuclear and fossil fuel power plants use generators driven by turbines to produce their electricity.

The generator is based on the principle of "electromagnetic induction" discovered in 1831 by Michael Faraday, a British scientist. Faraday discovered that if an electric conductor, like a copper wire, is moved through a magnetic field, electric current will flow (be induced) in the conductor. So the mechanical energy of the moving wire is converted into the electric energy of the current that flows in the wire. 4

Faraday's law states5:

E = N x ??/?t volts

Where E is energy, N is the number of turns, ? is magnetic flux and t is time. This means that is the number of turns in the coil is increased, so is the energy produced. The generators used in power stations involve huge coils with many turns moving in strong magnetic fields. These coils are rotated in the magnetic field by massive turbines. These turbines are driven by steam. The difference in fossil fuel plants and nuclear plants is simply how the steam is produced.

Both kinds of plant also use transformers to increase the voltage of the electricity produced before it is fed onto the national grid (the national electricity distribution system) and to reduce the voltage before the electricity reaches the consumer. This is to reduce the cost of electricity for both consumer and producer.

Consider the following:

• Electricity is generated at the generating plant at 240 Volts and then

delivered to the households over conductors.

• There are 10 households and each needs, for example, 1000 Watts.

• The electric company must therefore supply 10x1000 = 10,000 Watts.

• Current - Power / Voltage (I = P/V)

• So Current = 10,000/240 = 41.7 amps

• But, electrical power is dissipated as heat according to P = I2R (this is how

electrical stoves work)

• Lets assume R (resistance) =1: We now have:

Heat dissipation = (41.7)*(41.7)(1) - 1739 watts.

• Heat dissipation is energy lost by the system. This loss is unavoidable!

• To deliver the 10,000 watts that the consumer needs requires that we

generate 1739 watts and hence have an overall efficiency of

(10,000/11,739) x 100-85%. Which is a 15% loss the consumer would pay for! (This is far worse in the US which generates electricity at 120 volts, and has an efficiency of around 59%)

You can solve this loss problem using a transformer to change the voltage.6

Current = Power/Voltage; If we increase V by a factor of 10, then I lowers by a factor of 10 (at constant power) and the power dissipated as heat lowers by a factor of 102. Hence at 1200 Volts we have only 69.4 watts of energy loss and a 99% energy efficient delivery system, which is much cheaper for both producer and buyer.

How a transformer works

(A transformer)

A transformer uses alternating current in one coil to induce alternating current in another. The induced voltage is given by: Vout = Vin x N2/N1 where N1= Number of coils in the Primary and N2= Number of coils in the secondary. When N2 is less than N1, we reduce Vout. This is why there are transformers on power lines to step the voltage down to 240 Volts by the time it reaches your house. 7

How does each power plant work?

Fossil fuels

(See Diagram 1 on separate sheet) 11

This is an example of how a fossil fuel power station works, using coal as the fuel. Most fossil fuel plants work in this way, regardless of the fuel being coal, gas or oil.

. Coal Supply

Coal from the mine is delivered to the coal hopper, where it is crushed to five centimetres (2 inches) in size. The coal is processed and delivered by a conveyor belt to the generating plant.

2. Boiler

. The coal / air mixture ignites instantly in the boiler.

2. Millions of litres of purified water are pumped through tubes inside the

boiler.

3. Intense heat from the burning coal turns the purified water in the boiler.

3. Stack

Burning coal produces carbon dioxide (CO2), sulphur dioxide (SO2) and nitrogen oxides (NOx).

These gases are vented from the boiler.

Bottom ash, which is made of coarse fragments that fall to the bottom of the boiler, is removed. Fly ash, which is very light, exits the boiler along with the hot gases. An electrostatic precipitator (a huge air filter) removes 99.4 per cent of fly ash before the flue gases are dispersed into the atmosphere.

4. Turbine

. Water in the boiler tubes picks up heat from the boiler and turns into

steam.

2. The high-pressure steam from the boiler passes into the turbine (a

massive drum with thousands of propeller blades).

3. Once the steam hits the turbine blades, it causes the turbine to spin

rapidly.

4. The spinning turbine causes a shaft to turn inside the generator, creating

an electric current.

5. Condensers and the cooling water system

. Cooling water is drawn into the plant and circulated through condensers,

which cools steam discharged from the turbine.

2. Steam from the turbine also passes through the condensers in separate

pipes from cooling water.

3. The cold water is warmed by the steam, which condenses back into pure
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water and circulates back to the boiler to begin the process of generating

electricity again.

4. Cooling water, now warm from the heat exchange in the condensers, is

released from the plant.

6. Substation, transformer, transmission lines

. Once the electricity is generated, transformers increase the voltage so it

can be carried across the transmission lines.

2. Once electricity is delivered to substations in cities and towns, the voltage

flowing into the distribution lines is reduced, and then reduced again to

distribute electricity to customers.

Nuclear Power station
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