power systems Flashcards
why do we need power systems?
store energy and provide a conversion system to provide power to various systems
what power system is the most commonly used for earth-orbiting systems?
solar array photo-voltaic
describe how a photo-voltaic system works
use semi conductors to convert solar EM radiation to electrical energy
describe how the solar dynamics system works
use solar thermal energy to convert to kinetic energy which can subsequently be converted to electrical energy
describe how the chemical dynamic system works
use chemical potential energy released in an exothermic or combustion reaction to power a turbine
how do nuclear power sources work
use energy available from a nuclear fission chain reaction in a nuclear reactor - this can then be converted to electrical energy
what does ‘RTG’ stand for?
radioisotope thermal generator
how does an RTG power system work?
use thermal energy released from thermal decay of radioactive material - thermal energy converted to electrical energy using thermoelectric effects
describe how flywheel storage power systems work
use kinetic energy stored in a flywheel - subsequently converted to electrical energy
describe how fuel cell power systems work
use chemical potential energy which is converted to electrical energy in an electrochemical cell
describe the structure of a solar array
assembly of thousands of individual solar cells, each consisting of a semiconductor p-n junction that produces an electron flow when illuminated by photons with sufficient energy
what is a p-n junction?
boundary interface between two types of semiconductors, p and n
what is a p type semiconductor?
electron deficient
what is an n type semiconductor?
electron excess
describe the differences between a p-n junction with no illumination compared to with illumination
- no illumination: junction in equilibrium
- with illumination: electrical potential difference, electrons in the valence band of the junction able to move into the conduction band which enables current flow