Technology

  • Electric industry operations can be broken into three sectors: generation of electricity, transmission and distribution, retail (sale). Operations in all three sectors are coordinated by a systems operator which schedules the generation and delivery of electricity starting 24 hours in advance of when it is needed, right up to minutes before the electricity is produced and consumed.
  • The companies that make up the electric industry in the US can be subdivided into five types.
    • Investor owned utilities.
    • Federal power administrations.
    • Mederal power administrations.
    • Electric cooperatives. These typically not-for-profit utilities are customer owned and were founded by people in more sparsely populated rural areas.
    • Electric marketers.
  • Charge, Current, Voltage, and Resistance
    • Coulomb, the standard unit for measuring the electric charge of a bunch of electrons
    • Electric current is determined by measuring the to total charge passing a point along the conductor within a period of one second. The unit for current is the ampere. And 1 Ampere = 1 coulomb per second.
    • The amount of potential energy per coulomb of charge difference is referred to as the electromotive force, and it has units of volts. 1 Volt = 1 Joule of energy per Coulomb of charge.
    • A battery’s voltage then, is the energy with which the battery drives each coulomb of charge out of its negative terminal, through the conductor and into the battery’s positive terminal. Voltage is one of the two factors that determine the rate that electrons flow through the circuit or the circuit’s current. The other determining factor is the total resistance of the circuit to electron flow. The greater this resistance, the more it slows the current.
    • One of the ways to increase the resistance of circuit, is to narrow the conducting wire along a part of the circuit. Recall that the current is the same throughout the circuit. So as the conducting wire is narrowed, the same flow of electrons has to move through the narrower wire. And as electrons repel one another, a greater amount of energy in electrons has to be spent counteracting the increase in neutral repulsion arising from compressing the electrons closer together.
      This expenditure of energy is given off as heat. Which if hot enough can cause the thinner conducting wire to glow and that’s produce light. This is, in fact, how an light bulb works. Current passing through the light bulb is forced through a thin film of a wire with a much higher resistance than the conducting wire either side of the filament, the electricity expense energy pushing through the filament heating it to the point that it emits light.
      Resistance is measured in ohms, and 1 Ohm = 1 Volt (V) / Ampere (A).
    • In summary then, the summed charge of an excess of electrons is measured in coulombs. The rate that electric charge moves through a conductor is the electric current, which is measured in amperes. The current is a function of the resistance of the conducting material measured in Ohms, as well as a function of the electromotive force driving the current, or the potential energy of each coulomb of excess charge measured in volts. !!! Note that since excess charge is a relative measure, so is voltage. For batteries, voltage reflects the energy inherent in the charge difference between the negative and positive terminals of the battery. Use of voltage in the electric industry, however, refers to the difference in energy per coulomb of excess charge in the electric grid, with respect to the Earth’s surface, or ground, which has no excess charge.
  • Electric Power, Electric Energy, and Ohm’s Law
    • Power, which is the rate that energy is being generated, transmitted, or consumed, is equal to voltage times current. Power has units of watts or Joules per second.
    • Enery = Power * Time
    • Ohm’s law states that voltage equals current times resistance.
  • In the battery powered circuit, electricity flows in one direction from the batteries negative terminal to its positive terminal via a conductor that enters and leaves the light bulb. Due to which unidirectional flow the current is referred to as a direct current or DC current. The DC current is driven by the voltage difference across the batteries two terminals and is impeded by the resistance of the light bulb. Note that according to Ohm’s law, the current will equal the batteries voltage divided by the light bulbs resistance. So, the correct battery voltage needs to be chosen in order to make the light bulb emit its maximum amount of light. If the voltage is too low it will produce a current that along with the voltage, will not be enough to properly power the light bulb causing it to burn dimly or not at all. And if the voltage is too high it will produce a current that along with the voltage will overpower and burn out the light bulb by overheating and melting the bulb filament.

Electromagnetism

  • The magnitude of the AC current is a function of the strength of the magnetic field in the generator and the number of coils in the wire being moved through this field, also located in the generator. Note that an electromagnetic generator does not produce energy.
  • What the generator does is to transform this work into electricity, which can then be transmitted to a multitude of other locations, and used to do work there. So powerplants that produce electricity using electromagnetic generators requires some form of energy input to do the turning work required by the generators.
  • Lenz’s law
  • all plants can be compared on the basis of the maximum amount of power they produce, how efficiently they produce that power, and how much power they actually do produce.
  • The maximum amount of power that a plant produces is known as the plant’s capacity and is typically given in units of megawatts.
    There are in fact three types of capacity for a power plant. One is the plant’s Nameplate capacity. This is the capacity determined by the manufacturer for the power plant’s electric generator and represents the maximum output that the generator can produce without exceeding its thermal design limits. The second and third types of capacity for a power plant are its Net Summer and Winter capacities.
  • These are determined by an actual performance test under operational conditions and indicate the maximum load the plant’s generators can support during the height of the summer and winter months. These particular capacities are affected by the temperature of the cooling water for thermal electric power plants, the temperature of the ambient air for plants with combustion turbines, and the seasonal characteristics for water flow and reservoir and storage for hydroelectric plants.
  • (see pic2) Heat rate is the amount of energy in the fuel consumed by the plant over a period of one hour, divided by the amount of electrical energy output by the plant in that hour. Note that this ratio is always greater than one and has units of MMBtu per megawatt hour.
    • Remember, heat rate is the amount of energy in the fuel consumed by the plant over a period of one hour, divided by the amount of electrical energy output by the plant in that hour.
  • (see pic3) the last measure of a power plant, which is how much power the plant actually produces. This measure is known as the plant’s capacity factor and is given by the actual amount of energy the plant produced over a period of time, as typically measured in megawatt hours, divided by the amount of energy the plant could in theory have produced if it was run continuously over this period of time at its Nameplate capacity, also in units of megawatt hours. So, like efficiency, capacity factor is a ratio that is less than one and is unitless. However, do not confuse capacity factor with efficiency. Rather than providing a measure of how well the plant converts input energy into electricity, capacity factor measures how continuously a plant typically runs.

Transmission & Distribution

  • (see pic4,5) Since the change in voltage is directly proportional to the amount of coiling, the voltage difference can be precisely controlled through the number of times each power line is wrapped around the transformer’s iron core.
  • (pic,6,7) Power Line Loss: Electricity is transmitted at very high voltages so as to minimize the loss of electric power and energy due to power line resistance. Power lines are good conductors and have low electrical resistivity, the property that characterizes the electrical resistance of the material over a length of the meter. Even conductors with low levels of resistivity however, can have a large overall resistance when electricity is transmitted through the conductor over distances of tens to hundreds of kilometers or miles. And a large overall resistance for a power line can result in significant loss of electric power if the voltage and current of the electricity are not chosen correctly. Consider for example a power plant that is generating a certain number of megawatts of electric power for transmission via a long power line. Some fraction of the power produced by the plant will be expended, overcoming the resistance of the power line such that the power at the end of the line will be less than the power that enters the line. We can calculate what this difference or loss in power will be by combining the equation for electric power with Ohm’s law. Electric power is the product of voltage times current (P = V x I). While Ohm’s Law states that voltage equals current times resistance (V = I x R). There are two important constraints on these equations for the transmission of electricity. The first is that the resistance of a power line is fixed. The second constraint is that the current throughout the power line is constant. In other words, electrons flowing through one end of the power line are moving at the same rate as electrons flowing through the other end. Multiplying the current times the resistance then gives the electric voltage needed to produce the current given the power lines resistance. And replacing voltage with current times the power lines resistance in the equation for power, gives the amount of power needed to move the electricity through the power line at that current. This third equation then which is derived from the first two indicates how much power loss will occur if electricity is transmitted through the line at a particular current. The equation shows that while power loss increases linearly with increasing resistance of the power line, the loss increases much more rapidly with increasing current rising as a function of the current squared. Therefore, to minimize power losses due to transmission, current is kept as low as is practicable. And if current is low then voltage must be high in order to carry a given amount of electric power. This then is why use of high voltages to transmit electricity reduces electric power and energy loss due to power line resistance.

Load

(see pic 8)

Electric system management

screenshots

Markets

External

. And the most significant of these differing variable costs by far is each plant’s fuel cost, which is given by the price of the fuel that each plant uses times the individual plant’s heat rate and so has units of dollars per megawatt hour.