IB DP Physics: SL复习笔记8.1.4 Energy Resources

Energy Resources

  • Energy resources are large stores of energy that can be transferred from one form into electrical energy that can be used by society
  • Generating energy reliably requires the use of a range of different energy resources

Renewable Energy Resources

  • A renewable energy resource is defined as

An energy source that is replenished at a faster rate than the rate at which it is being used

  • As a result of this, renewable energy resources cannot run out
  • Renewable resources include:
    • Solar energy
    • Wind
    • Bio-fuel
    • Hydroelectricity
    • Geothermal
    • Tidal
    • Bio-fuels

Non-Renewable Energy Resources

  • Non-renewable energy resources are those that cannot replenish faster than they are used
  • Non-renewable resources include:
    • Petrol (gasoline)
    • Diesel
    • Coal
    • Natural gas
    • Nuclear fission

Energy Resources Table

1.2.1-Energy-Resource-Table-11.2.1-Energy-Resource-Table-2

Uses of Energy Resources

  • The three main uses of energy resources include:
    • Transport
    • Electricity generation
    • Heating

1.2.1-Uses-of-Energy-Resources

Types of energy resources

Transport

  • The majority of vehicles in the world are powered by petroleum products such as petrol, diesel and kerosene
    • These resources all originate from crude oil, which is a fossil fuel
  • A growing number of vehicles are now being powered by electricity
    • The advantage of this is that while the vehicle is being driven, it produces zero carbon emissions
    • The disadvantage is that when the vehicle is being charged, it is connected to the National Grid, which currently uses a combination of renewable and non-renewable energy sources
  • Vehicles can also be powered by biofuel
    • The advantage of biofuel is that it is a renewable resource
    • However, the claim that biofuels are carbon-neutral is largely controversial

Electricity Generation

  • Electricity plays a bigger role in people's lives than ever before
  • With almost 8 billion people in the world, this means the demand for electricity is extremely high
  • To keep up with this demand, a combination of all the energy resources available is needed
  • On the downside, the majority (84%) of the world's energy is still produced by non-renewable, carbon-emitting sources
    • This has an enormous negative impact on the environment
    • Currently, scientists are working hard to develop more and more efficient ways to produce electricity using more carbon-neutral energy resources

1.2.1-World-Energy-Consumption-2019

Pie chart of global energy consumption

Heating

  • Most homes in cold countries are fitted with central heating systems
  • These utilize natural gas in order to heat up water which can be pumped around radiators throughout the home
    • Unfortunately, gas is a non-renewable energy resource
  • In geologically active countries, such as Iceland, they are fortunate to be able to heat their homes using geothermal energy

Photovoltaic Cells & Solar Heating Panels

Solar Heating Panels

  • Solar heating panels are used to heat tap water (for washing and showers) using the thermal energy of the Sun
  • Solar heating panels can contain a water or glycol-water mixture which is pumped around to heat cold water from the main water supply
  • The pumped fluid becomes hot within the solar panel and transfers this heat within a hot water storage cylinder
  • A solar panel heating system is usually combined with a boiler to produce hot water at all times

8-1-4-solar-panel-heating-system_sl-physics-rn

A solar heating panel system in a home

Photovoltaic Cells

  • Photovoltaic (PV) cells are able to convert light from the Sun directly into electricity
  • PV cells contain a single crystal of semiconductor that has been doped to have one side be a p-type semiconductor and the opposite side is an n-type semiconductor
  • p-type and n-type relate their names to the majority of charge carriers within them
    • negative electrons for the n-type semiconductor
    • positive 'holes' which is the absence of electrons in the p-type semiconductor
  • Photovoltaic cells generate electricity as follows:
    • Light from the sun incident on the PV cell creates a photoelectric effect on the electrode at the surface
    • The reflect-proof film prevents the light from being reflected back into the air
    • Typically, the charge carriers in the semiconductor are in equilibrium, but when radiation is incident upon the PV cell, it enables electrons to move from the n-type layer to the p-type layer
    • The movement of the electrons generates an electrical current

8-1-4-pv-cell_sl-physics-rn

A simple diagram of a PV cell

  • A solar panel system is made up of many PV cells in series and parallel within the panel to increase electrical generation
  • Typical efficiencies of commercially available PV cell-based solar panels are around 20%

Advantages and disadvantages

  • Advantages of using solar power include:
    • Unlimited supply of energy
    • Clean to produce the electricity
    • Freely available everywhere
    • Cheap maintenance
    • No fuel is required for energy
  • Disadvantages of using solar power include:
    • Impacted by poor weather
    • Limited efficiency
    • Only available during the day
    • Requires large investment upfront
    • Needs large areas

Worked Example

A small community has solar panels which have an efficiency of 23%. They have arranged 103 m2 of solar panels to catch the sunlight incident upon them which has an intensity value of: 1.36 x 103 W m-2. Estimate the approximate power these solar panels will produce in 1 hour.

Step 1: List known values

    • Solar panel area: 103 m2
    • The average intensity of the Sun: 1.36 × 103 W m-2
    • Solar panel efficiency: 23%

Step 2: Identify relationship needed

    • The final answer required is power in Watts
    • Therefore the quantities must be multiplied together

Power = Area × Average Intensity × Efficiency

Step 3: Perform the multiplication

Power = 103 × 1.36 × 103 × 0.23 = 3.2 × 104 W

Step 4: State the final answer

    • The approximate power the solar panels will produce in 1 hour is: 3.2 × 104 W

Exam Tip

An in-depth understanding of how Photovoltaic cells works is not necessary for IB DP Physics, however a basic understanding of the process can be useful for tackling relevant questions.

 

 

 

 

 

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