Studied by 7 people
how storage hydroelectric system works
Water flows from the upper reservoir, because of gravity, through turbine(s) that rotate generator(s) to produce electricity. The water then flows into the lower reservoir where it remains until electricity demand lowers. When this occurs, the turbines spin backward to pump the water back into the upper reservoir so it can once again be used to generate electricity when needed.
profit of storage hydroelectric systems
during periods of high electricity demand, power is generated by releasing the stored water through turbines, but during periods when the demand for electricity is low/ electricity is cheap the water is bumped back to the upper reservoir
why number of wind turbines irl higher than on calculations
the efficiency is less than 100%, as not all KE of air can be converted to KE of blades
air needs to retain KE to escape, energy lost to friction in turbine
energy changes in pumped storage hydroelectric system
PE of water to KE of moving water to KE of turbines connected to the generator to electrical energy
energy losses in the PSH system
friction losses in walls of pipe and generator bearings
thermal energy losses in electrical resistance of components
water requires KE to leave system so not all can be transferred
how thermal energy of burning gas becomes electrical energy
internal energy of steam particles transfers to KE of turbine to KE of generator producing electrical energy
degraded energy
no longer available for the performance of useful work
results from solar energy incident on Earth
wind energy
generator in nuclear power station converts
kinetic energy into electrical energy
control rods
control the amount of power being released, absorb neutrons, maintain a constant rate of fission
moderator
slows down velocity of neurons, makes fission more likely to occur
coolant
gets hit by neutrons and the KE of neutrons captured in the coolant used to make electricity
fuel rods
tubes of enriched uranium where fission takes place
critical mass
amount of fissile material that will allow fission to be sustained
greenhouse gasses
transmit ultraviolet radiation byt absorb infrared radiation
carbon fixation
process wherein photosynthetic organisms (such as plants) turn inorganic carbon into organic compounds
conduction
heat energy is transmitted through collisions between neighboring atoms or molecules
convection
the rising motion of warmer areas of a liquid or gas, and the sinking motion of cooler areas of liquid or gas, sometimes forming a complete cycle.
insolation
Incoming Solar Radiation.
radiation
energy that comes from a source and travels through space at the speed of light
fuel
source of energy in useful form
fossil fuels non renewable
rate of production of fossil fuels much smaller than rate of usage, so will run out
reasons of widespread use of fossil fuels
readily available, cheaper production of electrical energy, for possible to generate sufficient energy without them
why worlds energy consumption is provided by fossil fuels
wide availability, ease of transportation, large energy density
specific energy
energy that can be liberated per unit mass
energy density
energy that can be liberated per unit volume
why enhanced greenhouse effect can result in increased temperature on Earth’s surface
atmosphere absorbs more infrared energy and heats up, atmosphere radiates in all directions, Earth’s surface absorbs some of this extra infrared radiation hence temperature increases
processes and energy changes that occur through when thermal energy is produced in a nuclear power station (U-235)
U-235 fissions - neutrons are produced, neutrons have high energy and transfer KE energy to moderator, moderator energy transferred to coolant
role of heat exchanger of the reactor in generation of electrical energy
allows transfer of thermal energy between reactor and coolant
role of turbine of the reactor in generation of electrical energy
coolant transfers thermal energy to steam, steam allows turbine to drive generator
processes in power station where energy is degraded
heating the working fluid in the exchanger, the working fluid passing through the turbine, cooling the working fluid having passed through the turbine
greenhouse gas
frequency of vibration is close to that of the frequency of infrared radiation, absorbs the infrared radiated by the surface of Earth,the part of the radiation that is re-radiated back to Earth will cause the temperature of the surface to rise
disadvantages of using solar power
takes a lot of space, low efficiency, power fluctuates according to weather, no power at night
how energy losses in the energy transmission are minimized
transmit at high voltage, use step up transformer to reduce current (lower current - resistance losses reduced), large cable cross section, good conductor used for cable
advantage of PS system
pumped storage on demand
disadvantage of PS system
needs to be restored before reuse
absorption
the Earth radiates radiation in the infrared region of the spectrum, the greenhouse gases have energy level differences corresponding to infrared energies, \n and so the infrared photons are absorbed
why solar radiation not affected by absorption
most incoming radiation consists of photons of much shorter wavelength than those radiated by the Earth, so these cannot be absorbed
emissivity
ratio of power emitted by body to the power emitted if it was a black body
albedo
fraction of power incident on a surface that is reflected
how is electrical power generated?
fuel is heated to boil water, which produces pressurized steam. the pressurized steam drives the turbine, which starts spinning and drives the generator, which produces electrical power by electromagnetic induction
solar panels vs photovoltaic cells
solar panels heat up water (solar → thermal), but photovoltaic cells solar → direct current
photovoltaic cells
the light incident on photovoltaic cells emits electrons, creating a potential difference across the panel
Note
Flashcard