12 Enviro Science Revision - U4 Energy

Energy Revision - U4

Focus Areas

• Renewable and Non-Renewable Energy Sources

• Energy Efficiency and Thermodynamics

• Sustainable Energy Use

Understanding Energy

• Definition of Energy:
  Energy is the capacity to perform work - measured in Joules.

• Forms of Energy:

  • Mechanical, chemical, thermal, electrical, nuclear, gravitational.

  • Example: Chemical energy in fuel is converted to mechanical energy in engines.

Open Ended

Define energy and list three different forms of energy. Provide an example of how one of these forms of energy is used in everyday life.

Energy conversions result in energy becoming less useful, often degraded as heat.

Second Law

Energy cannot be created or destroyed, only transformed.

​First Law

Energy Transfers & Laws of Thermodynamics

Open Ended

Explain how the First Law of Thermodynamics applies to energy transfers in a coal-fired power plant.

Draw an energy transfer diagram for this process.

Renewable & Non-Renewable Energy Sources

• Non-renewable: Oil, coal, natural gas, coal seam gas, nuclear.

• Renewable: Solar, wind, hydroelectric, tidal, geothermal, biomass.

• Key concept - Non-renewable sources are finite, contributing to climate change. Renewable sources are more sustainable, with fewer emissions. Understand advantages/disadvantages of each.

Open Ended

Compare the environmental impacts of coal and solar power as energy sources. Which one is more sustainable, and why?

Efficiency = Useful energy/Total Energy Input​ × 100
=10/100×100
= 10%

Solution:

A light bulb uses 100 Joules of energy and outputs 10 Joules as light. What is its efficiency?

Question:

Energy Efficiency Calculations

Math Response

A steam turbine outputs 160MW from an input of 200MW. What is the efficiency as a %?

Type answer here

Correct Answer: 80

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Exam Style MC Questions

Multiple Choice

Which energy source is NOT a fossil fuel?

• Coal

• Oil

• Natural Gas

• Nuclear Power

Multiple Choice

Which law explains why energy is lost in transformations?

• First law of thermodynamics

• Second law of thermodynamics

• Conservation of energy principle

• Energy efficiency law

Peak Oil and Fossil Fuel Depletion

• Definition: Peak oil is when global oil production hits a maximum rate and then declines.

• Causes: Declining reserves, technological limitations, and environmental concerns.

• Consequences: More expensive extraction and a shift toward alternative energy sources.

Open Ended

Explain the concept of peak oil and describe two potential consequences for society if peak oil is reached.

​Sustainable Energy Mix

• Base Load vs Peak Load:

  • Base load: Minimum energy demand over 24 hours (continuous operation, low cost).

  • Peak load: High demand periods (quick start, responsive).

• Sustainable Energy:

  • Wind, solar, and geothermal can help meet base and peak load needs in Australia.

Open Ended

Discuss the differences between base load and peak load energy demands. Which types of renewable energy sources are best suited to meet these demands, and why?

Math Response

A gas-fired power plant has an input energy of 300 MJ and produces 90 MJ of useful electrical energy. Calculate the efficiency of the power plant as a %.

Type answer here

Correct Answer: 30

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Consequences of Fossil Fuel Use

Impact on the Carbon Cycle:

• Fossil fuel combustion increases atmospheric CO₂.

• This disrupts the natural carbon cycle by increasing the concentration of greenhouse gases, which trap more heat and contribute to global warming - Enhanced Greenhouse Effect.

• CO₂ is absorbed by oceans, contributing to ocean acidification.

• Leads to global warming and climate change.

Open Ended

Explain how the burning of fossil fuels contributes to the enhanced greenhouse effect and impacts the global carbon cycle.

• Involves physical restoration of a site after energy resource extraction (e.g., mining).

• Key actions include:

  • Removal of mining infrastructure and machinery.

  • Regrading the land to its original contour or safe form.

  • Filling in voids created during mining activities.

  • Example: At the Hazelwood power station, demolition of infrastructure and filling of open-cut coal mines.

​Mechanical

Rehabilitation of Mine Sites

• Focuses on reintroducing natural ecosystems to the site.

• Key actions include:

  • Replanting endemic plants and trees to restore the local ecosystem.

  • Stabilizing soil using vegetation or biological processes, like introducing bacteria to improve soil quality.

  • Enhancing biodiversity by encouraging the return of wildlife.

  • Example: Replanting native species at the edges of the Hazelwood mine to restore habitat.

​Biological

Rehabilitation of Mine Sites

Open Ended

Describe an example of mechanical and biological rehabilitation that may be necessary for the rehabilitation of a coal mining site.

• Work on time management - allocate time according to question marks.

• Use past papers & topic tests (AGORA)

• Review Key Concepts (refer to Chapter 14 & 15 booklets).

• Practice diagrams and calculations

Exam Preparation Reminders

More Practice...

Multiple Choice

Newly built homes are now classified as energy efficient. What can be done to an established house to increase efficiency?

• Increase the number of windows

• Improve ventilation

• Insulate only the roof

• Install blinds

Multiple Choice

Which of the following best describes the environmental advantage of biomass over coal as an energy source?

• Biomass produces no waste products when burned.

• Biomass produces no carbon dioxide when burned.

• Coal is a renewable energy source.

• As it grows, biomass absorbs greenhouse gases from the air.

Multiple Choice

The energy conversions for burning macadamia nuts to produce electricity would be:

• Chemical – heat – kinetic – mechanical – electrical

• Potential – kinetic – heat – electrical

• Potential – heat – mechanical – electrical

• Chemical – kinetic – heat – mechanical – electrical

Multiple Choice

A sustainable energy source is:

• Freely available to all.

• One that serves the needs of current generations as well as future generations.

• Good for the environment as well as serving the needs of future generations.

• Only renewable energy.

Multiple Choice

Which law explains the statement: "With each energy conversion, the amount of 'high grade' (usable) energy available is reduced"?

• First law of thermodynamics

• Second law of thermodynamics

• Third law of thermodynamics

• The theory of relativity

Multiple Choice

Considering energy transfers for both coal and natural gas, which energy source would lose less energy when used as a heating source in a home?

• Coal

• Natural gas

• Both

• Neither

Open Ended

A small research station is located on the coast of Antarctica and uses a diesel generator. What are two disadvantages of using the diesel generator to provide electricity for the research station?

Open Ended

Name three non-renewable energy sources and outline to what degree they currently contribute to Australia’s energy needs.

Open Ended

Explain what is meant by 30% efficient when referring to solar cells.

Open Ended

Outline two limitations of using solar power in Australia and suggest how these might be overcome.

Open Ended

Explain the implications of the first and second laws of thermodynamics in making energy choices.

Math Response

Calculate the overall efficiency of a car engine as a % if 80% of the energy from petrol is lost as heat, and the remaining 20% is converted into mechanical energy.

Type answer here

Correct Answer: 20

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Open Ended

What is peak oil, and what might happen if society continues to rely on oil until we reach peak oil?