ENERGY AND POWER CONVERSION DEVICES Chapter 13

Objectives  List types of E & P conversions that can occur  Identify devices used to convert forms of E&P into other forms of E&P  Describe operation of devices for conversions  Explain new conversion devices not yet routinely used  Calculate the efficiency of various E&P conversion devices

FOUR types of Conversions  Power Conversion (Power to Power)  Energy Conversion (Energy to Power)  Frequency Conversions (Energy to Energy)  Energy Inversion (Power to Energy)

Power Converters  Change one form of power to another (power to power) Most common conversion devices  Electrical  Fluid  Mechanical  Electric Motor:  Converts one form of power (electrical)  Into another form of power (mechanical)

Power Conversion: Electrical to mechanical  Solenoid (very common) is a coil of wire with movable steel core in the middle  When coil is charged creates a magnetic field (electromagnet)  The core moves in a linear fashion  ie. door latches, door bells, relays

Power Converter: Solenoid Electrical to Mechanical  Why use a solenoid relay….  Allows power to be cut from many locations Can be operated with very little power  Avoids running large wires to all locations  Small wires are less expensive and easier to work with  ie. Your car’s starter works with a solenoid  ie. Used to open and closes valves allows central control

Power Conversion: Electric Motors  70% of all electricity generated is used to operate electrical motors.  All work on same principle  Magnets provide north and south polarity (magnetic field)  When wire placed between poles a current is “induced” (made to flow) in the wire  Current flowing in wire generates another magnetic field around wire  Magnetic fields pull and push each other to create motion  Quickly changing polarity of electromagnet sustains motion

Power Conversion: DC Electric Motor  Fixed magnets Armature  A series of wires wrapped around a metal core that is Free to rotate  Brush contactors  Supply electricity to the armature  Commutator (slip ring)  circular conductive strip attached to armature  Reverses flow of electricity every half turn

Power Conversion: AC Induction Motor  Uses Electromagnets – which can produce stronger magnetic fields resulting in more powerful motors  Stator- electromagnets attached to the housing (replaces the fixed magnets)  Rotor- spinning coil of the motor that is connected to the motor shaft

Power conversion: AC Induction Motor  Start windings: special set of stator windings  Single phase induction motors - have only one set of stator windings  Require start winding  Three phase induction motor (polyphase motors)- stator windings are arranged 120- deg out of phase with each other  No start winding required  Industrial use – very powerful

Power Conversion: Mechanical to Electrical  Generators- wire (armature) is moved through a magnetic field inducing voltage (sound familiar?)  Wire moves through the magnetic lines of flux producing voltage  Increased wire movement OR increased magnetic field = stronger induced voltage  In a real generator electromagnets are used to produce strong magnetic fields AND the armature spins at high RPMS this produces very strong voltage

Power Conversion: Mechanical to Fluid  Pump is used to convert mechanical power into fluid power (by pressurizing fluid)  Mechanical motion pressurizes fluid which is used to perform work  Reciprocating pumps or rotary vane pumps are examples

Power Conversion: Fluid to Mechanical  Use of cylinders (actuators) to convert pressurized fluid into linear mechanical movement.  Vane motor is just like rotary vane pump but pressurized fluid flows in the opposite direction and drives rotor.

Power Conversion: Fluid to Electrical  Converting electricity directly into fluid motion OR fluid motion directly back into electricity.  Magnetohydrodaynamic (MHD) Generator  Experimented with in the 1960s but left behind in favor of nuclear development  Similar to a generator (mechanical to electrical) but using conducting gas plasma instead of metal conductor like a wire

Magnetohydrodynamic (MHD) Generator:  Advanced system to develop electricity directly from heat source (fossil fuels) but still in the research stages  More efficient than conventional generating plant  Fuels are burned at very high temperatures  Gases from high temperature combustion are made electronically conductive by seeding with conductive chemicals  Very hot ionized gas takes the place of copper windings traveling at high speed through a magnetic field to produce DC electricity  Waste heat can be used to boil water and turn traditional turbine generators (1.5 times more efficient than conventional power plant)

Magnetohydrodaynamic (MHD) Generator:

Power Conversion: Electrical to Fluid  Electromagnetic induction pump without any moving parts can propel a liquid as long as the liquid can be polarized  ie. Moving mercury around using a magnet or submarine propulsion ????

Energy Converters  Changes form of Energy into a form of Power

Energy Conversion: Energy into Power  Visible light to electrical Power:  Photovoltaic cells: convert sunlight directly into electrical power  Photocells: (electric eyes) photons strike sensors that create small electric current that triggers a transistor to open or close a circuit.

Energy Conversion: Infrared Energy to Mechanical Power  Thermostat detects temperature and converts changes into mechanical power  Opens or closes electrical power electrical switch contacts to turn AC on or off.  Bimetallic coil-made from strips of two metals with different Coefficients of expansion (the rate at which a metal expands or contracts with changes in temperature) Coil tightens when cold, and expands when warm

Thermostats With Bimetallic Coil Infrared to Mechanical Power

Energy Conversion: Sound Waves to Electrical Power  Sound 3-miles/second through steel  Electricity travels at 186,000 miles/second  Faster to convert sound into electrical impulses for transmission over distances  Microphone does this and speakers convert electrical impulses back into sound.  Same basic concept as electrical motors / generators

Energy Conversion: Chemical Energy to Mechanical Power  Internal Combustion Engine is one example  Chemical energy (gasoline)  Converted to heat during combustion  Converted to fluid power (expanding gasses)  Converted to mechanical power (gasses push on mechanical components and move them)

Frequency Converters  Change one frequency (wavelength) of radiant energy into another frequency of radiant energy

Frequency Conversion  One frequency of radiant energy is converted into another frequency of radiant energy.  Frequency: the number of cycles in a given time interval (one second)  Hertz: a complete wavelength from start to finish

Frequency Conversion: Radiant Energy to Chemical Energy  Occurs naturally all the time in….  Photosynthesis- carbohydrates are compounded from carbon dioxide and water in the presence of sunlight and chlorophyll  Primary method of bioconversion of solar energy into all others

Frequency Conversion: Chemical Energy to Radiant Energy  Through process called …..  Combustion: the rapid chemical reaction in which heat and light are produced  Requires oxidation: a union between fuel and oxygen

Frequency Conversion: Visible Light to Infrared Light  Happens when visible light strikes something  Solar collectors are designed to maximize the conversion and capture the energy from the heat

Frequency Conversion: Ultra-Violet Radiation to Visible Light  Florescent bulbs  Electrodes are heated by electrical current and emit free electrons  Electrons strike atoms of mercury vapor  Mercury vapor emits radiant energy in the form of UV Radiation.  UV radiation strikes phosphor coating on bulbs and conversion to visible light occurs.

Energy Inverters  Changes a form of Power back into a form of Energy

Energy Inverters: Electrical Power to Visible Light  Two methods of producing artificial light  Heating something until it “glows.” standard incandescent bulbs heat tungsten until it glows white hot, producing light.  Pass electricity through a gas of vapor causing tiny charged particles within the atoms to glow like Halogen bulbs

Energy Inverters: Electrical Power to Infrared Energy  Electrical power to heat energy is common  Electrons flow through a wire exciting molecules within the wire.  Increased agitation causes molecules to move  Movement generates excessive energy, given off in the form of heat  ie: space heater, toasters, burners

Energy Inverters: Electrical Power to X-Radiation  X-ray tube converts electrical power into x- radiation (higher frequency than visible or UV light)  Negatively charged electrons strike a tungsten filament (like a light bulb)  Tungsten then emits x-rays  X-rays pass through lighter atoms but they are absorbed by more dense materials.

Energy Inverters: Electrical Power to Sound Waves  Speakers!!!!!  Work based on Principle of Magnetism: like forces repel one another and opposing magnetic forces attract one another  Contains electromagnet attached to cone that receives signal creating electrical field. Magnet in the base repels or attracts depending on the signal causing cone to move