Topic 7 And 8 Ib Sl Physics - Exam In Two Weeks

8.1.1: State that thermal energy may be completely converted to work in a single process, but that continuous conversion of this energy into work requires a cyclical process and the transfer of some energy from the system

• The continuous conversion of thermal energy into work requires thermal energy to be transferred to the surrounding
  For a continuous, cyclical conversion of thermal energy to occur, energy has to be lost to the surroundings, which consequently means the system requires a constant input of energy
  2nd Law of Thermodynamics
  It is impossible to take heat from a hot object and use it all to do work without losing some to the surroundings

8.1.2: Explain what is meant by degraded energy

• Understand that, in any process that involves energy transformations, the energy that is transferred to the surroundings (thermal energy) is no longer available to perform useful work
  Degradation of energy is the process of energy transforming into disordered, spread out energy
  energy, while always being conserved, becomes less useful, it cannot be used to perform mechanical work- this is called energy degradation

8.1.3: Construct and analyze energy flow diagrams (Sankey diagrams) and identify where the energy is degraded

• Sankey diagrams illustrate the flow of a system, can be used to display the flow of energy (how useful energy is produced
  energy input from the left
  wasted or unwanted energy forms (vertically down)
  useful energy output to the right
  width represents the amount of energy

What is efficiency?

• useful mechanical work done/ input energy

8.1.4: Outline the principle mechanisms involved in the production of electrical power

• Understand that electrical energy may be produced by rotating coils in a magnetic fields
  Electricity is produced using electrical generators by rotating a coil in a magnetic field so that magnetic field lines are cut by the moving coil
  According to Faraday’s law and emf (voltage) will be created in the coil which can then be delivered to consumers
  Generators convert mechanical energy into electrical energy

What can electrical power be generated from?

• heat source; steam generation; turbines; generator; transmission lines

8.2.1: Identify different world energy sources (8)

• oil, natural gas, coal, nuclear, hydroelectric, photovoltaic cells, biofuel, geothermal

8.2.2: Outline and distinguish between renewable and non-renewable energy sources

• Non-renewable sources are finite sources, which are being depleted, and will run out. They include fossil fuels (oil, natural gas and coal), and nuclear fuels (uranium). The energy stored in these sources is, in general, a form of potential energy, which can be released by human action.
  Renewable sources include solar energy, other forms indirectly dependent on solar energy (wind and wave energy) and tidal energy

8.2.3: Define the energy density of a fuel

• Energy density is the energy that can be obtained from a unit mass of the fuel.

What is energy density measured in?

• Energy density is measured in J kg-1

8.2.4: Discuss how choice of fuel is influenced by its energy density (3)

• Transport costs
  Storage
  Application

What is the percent of total energy produced for oil?

• 40%

What is the percent of total energy produced for natural gas?

• 23%

Q

What is the percent of total energy produced for coal?

• 23%

What is the percent of total energy produced for nuclear?

• 7%

What is the percent of total energy produced for hydroelectric?

• 7%

What are the advantages of fossil fuels? (4)

• Relatively cheap (while they last)
  • High power output (high energy density)
  • Variety of engines and devices use them directly and easily
  • Extensive distribution network is in place

What are the disadvantages of fossil fuels? (5)

• Will run out

• Pollute the environment

• Contribute to greenhouse effect by releasing greenhouse gases into atmosphere

• High cost of distribution due to high mass and volume of materials and high cost of storing (needs extensive storage facilities)

• Pose serious environmental problems due to leakages at various points along the production

What are the advantages of nuclear energy? (3)

• High power output

• Large reserves of nuclear fuels

• Nuclear power stations do not produce greenhouse gases

What are the disadvantages of nuclear energy? (4)

• Radioactive waste products difficult to dispose of

• Major public health hazard should ‘something go wrong’

• Problems associated with uranium mining

• Possibility of producing materials for nuclear weapons

8.3.1: Outline the historical and geographical reasons for the widespread use of fossil fuels.

• Recognize that industrialization led to a higher rate of energy usage, leading to industry being developed near to large deposits of fossil fuels

Discuss the energy density of fossil fuels with respect to the demands of power stations.

• A fossil-fuel power plant is a power plant that burns fossil fuels such as coal, natural gas or petroleum (oil) to produce electricity.

• The main systems are the steam cycle and the gas turbine cycle

Discuss the advantages associated with the transportation and storage of oil (3)

• Measures are in place for potential dangers

• Oil depots are usually situated close to oil refineries or in locations where marine tankers containing products can discharge their cargo

• Greater flexibility in maritime transport

Discuss the disadvantages associated with the transportation and storage of oil (3)

• Possibility of oil spills and discharging of polluting products such as the residue from tank and bilge cleaning

• Oil is corrosive to the pipes (pipes deteriorate if not changed in time)

• Construction of major pipelines crossing several countries requires intense negotiation

Discuss the advantages associated with the transportation and storage of natural gas (8)

• • Transport by gas pipelines are less costly
  • The compressed gas circulates at high speeds in a gas pipeline, with the aid of compression plants positioned at regular intervals along the network
  • Underground facilities allow for reuse with suitable modification, of the extraction and distribution infrastructure remaining from the productive life of the gas field which reduces the start-up costs
  • Depleted reservoirs are also attractive because their geological and physical characteristics have already been studied by geologists and petroleum engineers and are usually well known
  o Cheapest and easiest to develop, operate, and maintain
  o Relatively close to gas markets and to transportation infrastructure
  • Salt caverns allow very little of the injected natural gas to escape from storage unless specifically extracted. The walls of a salt cavern are strong and impervious to gas over the lifespan of the storage facility
  • Deliverability from salt caverns is, however, much higher than for either aquifers or depleted reservoirs
  • useful in emergency situations or during short periods of unexpected demand surges
  • the ability to perform several withdrawal and injection cycles each year reduces the effective cost.

Discuss the disadvantages associated with the transportation and storage of natural gas (6)

• In some cases, the construction of gas pipelines is technically impossible or too expensive

• Salt caverns cannot hold the large volumes of gas necessary to meet base load storage requirements

• construction is more costly than depleted field conversions when measured on the basis of dollars per thousand cubic feet of working gas

• The geological and physical characteristics of aquifer formation are not known ahead of time and a significant investment has to go into investigating these and evaluating the aquifer’s suitability for natural gas storage

• all of the associated infrastructure must be developed from scratch, increasing the development costs compared to depleted reservoirs

• Aquifers are generally the least desirable and most expensive type

Discuss the advantages associated with the transportation and storage of coal (7)

• The long life of the permanent assets, relatively trouble-free operation with minimum maintenance, the large-volume shipments that are possible, the high mechanical efficiencies that are obtained with low rolling resistances, and the dedicated nature of the origin and destination of the runs

• Trucks have a plus over trains because trucks can negotiate more severe grades and curves, roads can be resurfaced or constructed more readily and with far lower capital investments that can railways

• Transport of coal on barges is highly cost-efficient

• Conveyors can traverse difficult terrain with greater ease than trucks or rail systems, and they can also be extended easily and have the advantage of continuous transport

• Conveyors have enormous capacities

• The total costs of moving slurry during the life of the line do not increase in proportion to inflation

• Pipelines require less right-of-way, much less labor and about half of the steel and other supplies required for other transport methods

Discuss the disadvantages associated with the transportation and storage of coal (4)

• Roadbed and track requirements and large fixed investment in railcars make rail transport capital-intensive

• Waterways are usually circuitous, resulting in slow delivery times

• Slurry pipelines involve potential environmental problems. Water requirements are substantial

• Water pollution at the mouth of the pipeline

State the overall efficiency of coal power stations

• 35-42%

State the overall efficiency of oil power stations

• 38-45%

State the overall efficiency of natural gas power stations

• 45-52%

Describe the environmental problems associated with the recovery of fossil fuels and their use in power stations (4)

• Destructs the habitations of wildlife and marine animals

• “oil spill”

• damage the environment since while burning the fossil fuels, the “pollutants” like “sulfur dioxide, nitrogen oxides, carbon dioxide and carbon monoxide” dissipate into air which helps the greenhouse effect to accelerate and cause “global warming”

• pollutants attribute to acid rain

Describe the environmental problems associated with oil recovery (2)

• Hydraulic downhole’s surface pumps are dangerous for wild animals who sometime become trapped in the surface pump which leads to injuries and death

• Production tube tearing can occur leading to an inefficient process in oil recovery by wasting lots of energy

Describe the environmental problems associated with natural gas recovery (2)

• Recovery of natural gas from salt water is extremely difficult

• Costly

Describe the environmental problems associated with coal recovery (3)

• Leads to destruction of the habitation for the wildlife animals

• Efficiency is really low due to high production of coal ash

• Coal that is mixed with oil or water is inefficient to recover