Chapter 13 Energy & Power Conversion Devices

Objectives Devices used to convert one form of energy or power into other forms of energy or power. New conversion devices. Efficiency of various energy and power conversion devices.

Types of Conversions 4 basic types of conversion: 1. Power conversion (power to power). 2. Energy conversion (energy to power). 3. Frequency conversion (energy to energy). 4. Energy inversion (power to energy). Power converters are used to change one form of power to another. The electric motor converts one form of power – electricity, into another form of power – mechanical power. A good example of energy converter is a photovoltaic cell. It converts visible light energy into electricity. Frequency converters change frequency of energy. For example solar collectors change visible light energy to infrared (heat ) energy. An energy inverter like a space heater changes electric power to infrared (heat) energy.

Power Conversions The 3 forms of power are electrical, fluid, and mechanical power. Power conversion involves changing one of these forms of power into another. Electrical to mechanical: More than 70% of all electricity generated nationwide is used to operate electric motors. Other applications are relays and solenoids. Mechanical to electrical: A generator is the principal means of producing electricity from rotary mechanical power. Mechanical to fluid: A pump (gear and centrifugal pumps) is used to convert mechanical power to fluid power.

Energy Conversions Visible light energy to electrical power: Photovoltaic cells convert sunlight directly into electricity. Infrared energy to mechanical power: A thermostat can detect temperature and convert changes in temperature into mechanical movement. This movement is often used to open or close electrical switch contacts to turn a furnace or air conditioner on or off (fig , page 309). Chemical Energy to Mechanical Power: The internal combustion engine consumes gasoline, a form of chemical energy, and converts it to heat and then fluid power in the form of expanding gases, and finally to mechanical power through the piston, connecting rod, and crankshaft assembly. (fig 13-17, page 312).

Frequency Conversion The electromagnetic spectrum is made up of radiant energies of various frequencies including infrared rays, visible light rays, UV rays, X rays, radio waves, and gamma rays. Radiant energy to chemical energy: The process is known as photosynthesis. Visible light to infrared energy: Solar collectors capture energy from the heat. UV (Ultraviolet) radiation to visible light: The process of converting one form of light into another is known as fluorescence and the device fluorescent light bulb.

Energy Inverters Energy inversion involves converting a form of power back into a form of energy. A light bulb is a good example as it changes electricity into visible light. Another common inversion is that of electricity to heat. In some homes resistance heating is the primary heating system. The X ray tube converts electricity into X radiation. An airport baggage scanner works in a way similar to the X-ray machine.

Entropy and Efficiency of Converters Entropy is a measure of energy lost upon conversion. Total system efficiency will decrease every time an energy or power form undergoes conversion. % efficiency = (output x 100) / input The output and input units must be the same. 1 hp = 746 watts = 550 ft-lbs./sec 1 hp x = 1 Btu/min

Summary Power converters are used to change one form of power to another. The electric motor converts one form of power – electricity, into another form of power – mechanical power. A good example of energy converter is a photovoltaic cell. It converts visible light energy into electricity. Frequency converters change frequency of energy. For example solar collectors change visible light energy to infrared (heat ) energy. An energy inverter like a space heater changes electric power to infrared (heat) energy. The 3 forms of power are electrical, fluid, and mechanical power. Power conversion involves changing one of these forms of power into another. Visible light energy to electrical power: Photovoltaic cells convert sunlight directly into electricity. Energy inversion involves converting a form of power back into a form of energy. A light bulb is a good example as it changes electricity into visible light. Entropy is a measure of energy lost upon conversion. Total system efficiency will decrease every time an energy or power form undergoes conversion. % efficiency = (output x 100) / input The output and input units must be the same. 1 hp = 746 watts = 550 ft-lbs./sec and 1 hp x = 1 Btu/min.

Home Work 1. What are the four basic types of conversions? 2. What are the 3 forms of power? What is power conversion? 3. What is energy inversion? Give an example.