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Renewable Energy

Renewable Energy. #1 Electricity Definitions. Everything made of Atoms. Electrons flow when the electrical balance is upset. Current- movement of electrons between atoms. Current. Flow of electrons can be measured in units called AMPERES “Amps” 6.28 x 10 18 electrons per second = 1 Amp

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Renewable Energy

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  1. Renewable Energy #1 Electricity Definitions

  2. Everything made of Atoms

  3. Electrons flow when the electrical balance is upset Current- movement of electrons between atoms.

  4. Current • Flow of electrons can be measured in units called AMPERES “Amps” • 6.28 x 1018 electrons per second = 1 Amp • What is always produced when current flows? • HEAT

  5. Conductors • Materials that allow easy electron shifting. • Examples include: gold, platinum, aluminum, copper, silver. • What’s most common in homes?

  6. Resistance • Even best conductors have some resistance. • Examples are lights, motors, heaters • Measured in ohms • Like water flowing through a pipe

  7. Longer, smaller diameter wires have more resistance than bigger diameter ones. • Heat and or light builds up. • Incandescent bulbs work this way

  8. Insulators • Items from which the electrons are not easily “freed” • Examples: glass, rubber, wood, porcelain, plastic • Opposite of a conductor

  9. Measurement of a potential difference between two points along a conductor. (It is the pressure that makes current flow). Voltage

  10. Voltage supplied by generator or battery

  11. Power • Measurement of work an electric current can perform in a given time. • Measurement of the rate at which it can be converted into some other form of energy such as light, heat, or mechanical force. • Measured in watts or kW (1000 watts)

  12. Higher watts requires more electricity • More watts don’t mean higher output though. • Appliances rated in watts. • Home usage measured in kW and power plants in mW megawatts output

  13. Horsepower In motors, 1 Hp = 746 watts Watts = voltage x amperage

  14. Energy • The work done over a period of time. Example of usage: • Blow dryer used 2 hours each week and rated at 1500 watts. 1500 x 2 = 3000 watts. 3000 / 1000 (conversion to kW) = 3 kW used

  15. Energy Use Calculations • Need this information • 1 the rated power of the appliance, usually given in watts; 2 the length of operating time, 3 the cost of electricity.

  16. Example • A tool has a power rating of 1500 watts and is used for 6 hours at an electricity cost of .08 per kwh. How much does it cost to run the tool? • 1500 / 1000 = 1.5 (conversion to kW) • 1.5 x 6 hrs = 9 kwh • 9 x .08 = .72 to run the equipment

  17. You try this example • A refrigerator is rated at 1200 watts. It runs about 20% of the time during the day. Cost is 7 cents per kWh. What is the annual cost to run the appliance? • Answer: • 1200/1000 = 1.2 kWh • 24 hrs x 20% = 4.8 hours • 1.2 x 4.8 = 5.76 kilowatt hours • 576 x 365 = 2100 kWh • 2100 x .07 = $147.00

  18. Reading hand-style gauges 1- record the number on the far right dial that was just passed (7) then the same with the next to the left (3) 2- If the hand is directly on a number- If the hand on the right has passed zero, write down the number the hand on the left is pointing to, in this case, the 7. If the hand on the right is not past zero, then write down the next lowest number on the dial you're reading. THIS METER IS 8737 KWH

  19. More on electricity • Appendix A The New Solar Electric Home textbook • http://lansing.apogee.net

  20. END This material is based upon work supported by the National Science Foundation under award DUE-0434405

  21. Renewable Energy #2 AC, DC, Safety

  22. Alternating Current (AC) • More economical to produce. • Typical in households and business • George Westinghouse first distributed it commercially in 1886. • Voltage can be easily stepped up or down depending on needs. Results in high versatility.

  23. Oscillation of voltage and current evident in sine waves of 60 cycles per second in N. America and 50 cycles per second in Europe

  24. Five characteristics of AC • Amplitude • Frequency • RMS • Cycles • Peak to peak

  25. Amplitude • The first characteristic of AC power is its "amplitude". Amplitude is the maximum value of current or voltage. It is represented by either of the two peaks of the sine wave. This voltage level is also referred to as the peak voltage, and can be either positive or negative. Positive and negative refer only to the direction of current flow. A negative number does not mean that the voltage or current flow are less than zero, only that the current flows in the opposite direction.

  26. Cycle • A cycle is one complete repetition of the sine wave pattern. It is produced by one complete revolution (360 degrees) of the AC generator. • Since the sine wave begins at zero, goes positive through the positive peak, then negative through zero and reaches the negative peak, and to zero, we say a full cycle has been completed.

  27. Frequency (Hertz) • The number of times the sine wave pattern cycle occurs in a second is called the frequency. Frequency was originally measured in cycles per second, or CPS. Today, the unit of measurement for frequency is called Hertz, in honor of the scientist George Hertz.

  28. Peak to Peak • There are two values of voltage that we must be familiar with. The first is "peak-to-peak" voltage. This is the voltage measured between the maximum positive and negative amplitudes on the sine wave. It is twice the amplitude. This value is the maximum voltage available, but is not all useable in practical applications.

  29. The second value of voltage is the actual useful voltage that is available and is called RMS. This stands for Root Mean Square and it is the standard way of measuring and reporting alternating current and voltage. It is not the peak; it is the average. • The RMS is found by multiplying the peak amplitude by the square root of 2 (approximately 0.707). This yields the actual, useable voltage. It is typically represented by a dotted line drawn across each peak near the 70 percent point.

  30. The Power Grid • Series of electricity distribution lines • Electricity produced at low voltages then stepped up to 69,000 – 765,000 volts and sent long distances. • Large voltages are split and redistributed at substations near big cities. • More reductions at residential transformers

  31. Transmission Voltages • 69 and 138 kV common • Also in operation are 44, 115, 169, and 230 kV • The largest systems may have 345, 500, 765 kV with experiments done using 1100 kV (1,100,000 volts!)

  32. Why are high voltages needed? • Loss of power due to long distances. • Can remedy problem with larger diameter wires or higher voltage (more push). Higher voltage is cheaper than larger diameter.

  33. Direct Current (DC) • Low amperage, high voltage • Straight alignment of electrons flowing in one direction • Thomas Edison’s first systems were DC

  34. DC Generator • A single loop of wire in a magnetic field can be used as a DC generator. When the loop is stationery, it is not cutting any magnetic lines of force and the current and voltage are zero. As the loop of wire is rotated through the magnetic field, it starts to break the magnetic lines of force and current and voltage are induced in the wire loop.

  35. DC continued • Voltage and current remain steady unlike AC which oscillates.

  36. Static Electricity • Build up of electrons in an object like a person. Eventually, they are discharged to a cathode (more positively charged object) • Can damage sensitive electrical equipment and ignite petroleum

  37. What’s a thermocouple? • Two dissimilar metals joined and heated at junction will cause small current to flow. • This current flow can be linked to valves on furnace allowing fuel to flow as long as flame is present but shut-off if fire goes out as safety device.

  38. A small amount of electricity can be generated from heat by connecting two dissimilar metals and heating the spot where they are joined. Metals such as copper and constantan, a copper/nickel alloy, or iron and nickel are typical pairs. junction

  39. Video Electric Motors

  40. Risk of Shock Depends on • internal and external moisture of skin • exposed sub-epidermal tissue • and skin thickness

  41. Safety • People can detect 1/100 Amp (1 milliamp) Tongue most sensitive. • At 15+ milliamps, muscles contract and you can’t let go of an electrified object. Pain is felt at this level. • Electrical burns occur both inside and outside the body at 50 milliamps. Flesh is cooked.

  42. 1/10 Amp (100 milliamps), heart stops (fibrillation). Do CPR

  43. Safety cont. • Resistance ranges from 10,000 ohms when dry to 1000 ohms when wet • Example: A dry person touches 120 V household power. 120 V / 10,000 ohms = 0.012 amps or 12 milliamps. Can still let go but electricity is definitely felt.

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