Topic 8: Energy, Power, and Climate Change
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| 3832504775 | Degraded Energy | 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. This unavailable energy is known as degraded energy | 0 | |
| 3832504776 | Efficiency | Approximate overall energy efficiencies for different types of power station are: Coal: 35% Gas: 45% Oil: 38% Each of these could theoretically be increased by an additional 7 percentage points at maximum | 1 | |
| 3832504777 | Energy Density | Energy density is defined as the energy liberated per unit mass of fuel consumed. It is measure in J kg^-1 | 2 | |
| 3832504778 | Non-Renewable Energy Sources | Those energy sources that can be used up and eventually run out | 3 | |
| 3832504779 | Renewable Energy SOurces | Those energy sources that cannot be used up | 4 | |
| 3832504780 | Sankey Diagrams | Sankey diagrams are pictorial representations of energy conversions. An arrow(left to right) represents the energy changes taking place. The width of the arrow represents the power of energy involved at a given stage. Degraded energy is shown with an arrow up or down | 5 | |
| 3832504781 | Thermal Energy Conversion | 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 | 6 | |
| 3832504782 | Albedo | Some of the radiation received by a planet is reflected back into space. The albedo of a surface is the ratio of the power that is scattered (reflected) from the surface compared to total incident power received. It is a ratio and has no units: albedo = total scattered power/ total incident power | 7 | |
| 3832504783 | Black-Body Radiation | At a given temperature, different surfaces will radiate different amounts of EM radiation. The maximum theoretical amount that can be emitted from any surface is known as black-body radiation (a 'perfect' emitter is also a 'perfect' absorber and a black surface is the best absorber). The characteristics of black-body radiation are mathematically described by the Stefan-Boltzmann law and Wein's law | 8 | |
| 3832504784 | Emissivity | The emissivity, ε, is the ratio of power radiated per unit area by a given surface to the power radiated per unit area by a black body at the same temperature. It has no units P=εσAT^4 P is the total power radiated by a surface in W ε is the emissivity of the surface (no units) σ is the Stefan-Boltzmann constant (5.67 × 10−8 W m-2 K-4) A is the surface area in m-2 T is the absolute temperature of the black body in K. | 9 | |
| 3832504785 | Energy Balance Climate Model | If the incoming radiation intensity to a planet's surface and its outgoing radiation intensity are not equal, then the planet's temperature will vary as given by: ΔT=[(I(in)-I(out))Δt]/C(s) | 10 | |
| 3832504786 | Greenhouse Effect | The atmosphere is transparent to many frequencies of electromagnetic radiation. Much of the power received from the Sun is in the visible and ultraviolet regions. This causes the surface of the Earth to warm up and radiate in the infrared. Some of this infrared radiation is absorbed by gases in the atmosphere, causing the atmosphere to warm up, and re-radiated in all directions. The net effect is that the atmosphere and the surface of thhttps://quizlet.com/create-set#add-rowe Earth are warmed | 11 | |
| 3832504787 | Greenhouse Gas | The gases in the atmosphere that absorb infrared radiation are called greenhouse gases. The principle greenhouse gases are methane, water vapour, carbon dioxide, and nitrous oxide. Ozone and chlorofluorocarbons (CFC's) also contribute to the greenhouse effect | 12 | |
| 3832504788 | Stefan-Boltzmann Law | The equation for the total power radiated in black-body radiation: P=σAT^4 P is the total power radiated by the black body in W σ is the Stefan-Boltzmann constant (5.67 × 10−8 W m-2 K-4) A is the surface area in m^-2 T is the absolute temperature of the black body in K | 13 | |
| 3832504789 | Surface Heat Capacity | The energy required to raise the temperature of unit area of a planet's surface by one degree C(s)=Q/AΔT Cs is the surface heat capacity in J m^-2 K^-1 Q is the energy absorbed by the surface in J A is the surface area in m^-2 T is the absolute temperature of the surface in K | 14 | |
| 3832504790 | Coefficient of Volume Expansion | The fractional change in volume per degree change in temperature. Its units are K^-1 | 15 | |
| 3832504791 | Enhanced Greenhouse Effect | An enhanced Greenhouse Effect is an increase in the greenhouse effect caused by human activities. One possible effect of an enhanced greenhouse effect is a rise in mean sea level. International efforts to reduce the enhanced greenhouse effect include the Intergorervnmental Panel on Climate Change(IPCC), the Kyoto protocol (an amendment to the UN Framework Convention on Climate Change), and the Asia-Pacific Partnership on Clean Development and Climate(APPCDC) | 16 | |
| 3832504792 | Carbon Dioxide Capture and Storage | Carbon Dioxide is emitted by fossil fuel power stations. A traditional power station just releases is into the environment, potentially increasing the enhanced greenhouse effect. Carbon capture and storage is the general term for preventing its release into the environment | 17 | |
| 3832504793 | Combined Heating and Power Systems(CHP) | Combined haeting and power systems (CHP) improve the overall efficiency of electricity generation by utilizing the thermal energy generated to, for example, supply hot water for local domestic supply | 18 | |
| 3832504794 | Hybrid Vehicles | Traditional vehicles run on petrol of diesel. An electric vehicle runs on batteries. A hybrid vehicle uses electric motors with a petrol engine as back-up to provide additional power when necessary. Sophisticated computerized systems switch from the electric motor to the petrol engine and back as required | 19 | |
| 3832504795 | Hydroelectric Schemes | Including; lake storage, tidal water storage, and pump storage. Hydroelectric power stationsuse the gravitational potential energy of water to generate electrical energy. Lake storage allows water that jas fallen as rain to collect in a reservoir that is as high up as is feasible. This water is allowed to flow downhill. Tidal power stations trap water at high tides and release it during a low tide. Pump storage involves pumping water from a low reservoir to a high reservoir for later release downhill. Although less energy will be generated than went into pumping the water uphill, it still allows for a large-scale method of storing energy | 20 | |
| 3832504796 | Oscillating Water Column Ocean-wave Energy Converter | Usete electrical energys the kinetic energy of waves to genera | 21 | |
| 3832504797 | Photovoltaic Cell | A photovoltaic cell (solar cell) converts a portion of the radiated eergy that falls on its surface directly into a p.d. using a piece of semiconducting material; for example, a solar-powered calcuator | 22 | |
| 3832504798 | Power for a Wind Generator | The following equation calculates the total power (in W) available to a wind turbine as a result of the kinetic energy of wind. In practice, all this power cannot be harnessed power=1/2 Apv^3 A is the area 'swept out' by the blades of the turbine in m^2 ρ is the density of the air in kg m^-3 v is the velocity of the air in m s^-1 | 23 | |
| 3832504799 | Power per Unit Length | The following equation calculates the total power per unit length (in W m^-1) available as a result of the kinetic energy of waves. This assumes a rectangular profile for the waves and in practice all this power cannot be harnessed power per unit length= 1/2 A^2 pgv A is the amplitude of the waves in m ρ is the density of the water in kg m^-3 g is the gravitational field strength (10 N kg^-1) v is the velocity of the wave in m s^-1 | 24 | |
| 3832504800 | Solar Heating Panel | A solar heating panel is designed to capture as much thermal energy as possible. Typically this directly heats water that is flowing through the panels which can then be used domestically. For example, some houses have solar panels on their roofs to save on the use of electrical energy | 25 | |
| 3832504801 | Control Rods | Control rods are movable rods that readily absorb neutrons. They can be introduced or removed from the reaction chamber in order to control the chain reaction. | 26 | |
| 3832504802 | Controlled Nuclear Fission | Controlled nuclear fission takes place in power stations. Excess neutrons are absorbed to ensure that the nuclear reactions take place at a constant rate. | 27 | |
| 3832504803 | Fuel Enrichment | Enrichment is the process by which the isotopic composition of a nuclear fuel is increased to make nuclear fissions more likely. Typically, uranium fuel rods are enriched to ensure that the percentage content of uranium-235 in increased. | 28 | |
| 3832504804 | Heat Exchanger | The heat exchanger allows the nuclear reactions to occur in a place that is sealed off from the rest of the environment. The reactions increase the temperature in the core. This thermal energy is transferred to heat water, and the steam that is produced turns the turbines. | 29 | |
| 3832504805 | Moderator | The moderator in a nuclear reactor is there to slow down emitted neutrons. Collisions between the fast-moving neutrons and the nuclei of the moderator slow them down and allow further nuclear reactions to take place. | 30 | |
| 3832504806 | Uncontrolled Nuclear Fission | This takes place in nuclear weapons where chain reactions result in a large amount of energy all being released at once. | 31 |
