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In a simple resistive circuit, a reduction in the voltage across the resistance will result in a reduction in the power dissipated by the circuit.
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In a simple resistive circuit, a reduction in the voltage across the resistance will result in a reduction in the power dissipated by the circuit.
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Electric utilities have discovered that this basic principle can save utility companies, and their customers, a significant amount of money. Utilities are able to shave the peak of their power demand curves by reducing the voltage across their distribution system. When a utility reaches a point where power demand is expected to exceed supply, utilities only have two options. Either purchase power from another utility, usually at substantial prices, or reduce demand. Often utilities use load management systems to turn off customers' air conditioners, water heaters, and pool pumps to reduce demand. Voltage reduction has become another option for utilities to reduce demand—typically unbeknownst to the customer. However, only the resistive portion of the load responds to the reduction in voltage to reduce aggregate demand. Loads such as incandescent lights and heater coils will use less power as the voltage is lowered. On the other hand, induction motor loads are unaffected by the reduction in voltage, because the current simply rises to account for no change or even a slight increase in power consumption. Current rise is detrimental to motors, since they run hotter. Also, to accomplish the same work the motors have to run longer, for example, if a refrigerator is running at 35% duty cycle at nominal voltage, at lower voltage its duty cycle may increase to 40%. Running hotter and running longer shortens the service longevity of motors.
Even some resistive loads provide only short-term benefits. A phenomenon known as load diversity plays a role in voltage reduction and can counteract its effects on occasion. The concept of load diversity can most easily be explained with an example. In your neighborhood, it is unlikely that all of the homes' water heaters are on at the same time. Particularly during non-hot water usage hours (morning and evening showers), when your hot water heater is on, your neighbor's may be off. Due to the distributed and noncoincident nature of these loads, the aggregate peak can remain relatively constant. However, if the voltage is reduced to all of the resistive elements in the water heaters, the elements will not be able to heat the water as quickly. While an immediate reduction in the power demand will be recognized upon initiating voltage reduction, over time water heaters will need to be on longer to achieve the thermostat-set water temperature. Thus, more water heaters will be on at the same time. This will cause the aggregate peak to increase substantially. Therefore, with respect to thermostat-controlled resistive loads, the benefits of voltage reduction can be short lived, and may occasionally end up increasing the aggregate load demand.
Conversely increasing the voltage may increase power demand from the resistive loads. Again, the thermostat-controlled resistive loads will react differently, but it is clear that it will cost a customer more to turn on that incandescent reading lamp with higher voltage than it would at a lower voltage. Of course this is assuming that the customer is satisfied with dimmer light, otherwise the customer can replace the light bulbs with ones of higher wattage to provide sufficient lighting. In today's modern world many light fixtures, including the ones with LED type bulbs, are dimmable. Therefore at lower voltage the dimmer will be turned up and at higher voltage it will be turned down, resulting in the same lumens being generated by the light fixture, hence no energy savings will take place. A good comparison of methodology of lowering the voltage to save energy is to draw a parallel with lowering the water pressure to save water. The washing machine will have to fill to the same level, it will just take longer; the toilet tank will fill to the same level, etc. Irrelevant of the pressure the customer will have to use all the necessary water to get the desirable results. There will be short-term savings because the lawn will not get sufficiently watered, but the customer will eventually notice this and will adjust the valves, watering duration or the number of sprinkler heads to compensate for the lower pressure.
An incandescent light bulb, incandescent lamp or incandescent light globe is an electric light with a wire filament heated until it glows. The filament is enclosed in a glass bulb with a vacuum or inert gas to protect the filament from oxidation. Current is supplied to the filament by terminals or wires embedded in the glass. A bulb socket provides mechanical support and electrical connections.
A halogen lamp is an incandescent lamp consisting of a tungsten filament sealed in a compact transparent envelope that is filled with a mixture of an inert gas and a small amount of a halogen, such as iodine or bromine. The combination of the halogen gas and the tungsten filament produces a halogen-cycle chemical reaction, which redeposits evaporated tungsten on the filament, increasing its life and maintaining the clarity of the envelope. This allows the filament to operate at a higher temperature than a standard incandescent lamp of similar power and operating life; this also produces light with higher luminous efficacy and color temperature. The small size of halogen lamps permits their use in compact optical systems for projectors and illumination. The small glass envelope may be enclosed in a much larger outer glass bulb, which has a lower temperature, protects the inner bulb from contamination, and makes the bulb mechanically more similar to a conventional lamp.
A fluorescent lamp, or fluorescent tube, is a low-pressure mercury-vapor gas-discharge lamp that uses fluorescence to produce visible light. An electric current in the gas excites mercury vapor, which produces short-wave ultraviolet light that then causes a phosphor coating on the inside of the lamp to glow. A fluorescent lamp converts electrical energy into useful light much more efficiently than an incandescent lamp. The typical luminous efficacy of fluorescent lighting systems is 50–100 lumens per watt, several times the efficacy of incandescent bulbs with comparable light output. For comparison, the luminous efficacy of an incandescent bulb may only be 16 lumens per watt.
Electric power distribution is the final stage in the delivery of electric power; it carries electricity from the transmission system to individual consumers. Distribution substations connect to the transmission system and lower the transmission voltage to medium voltage ranging between 2 kV and 35 kV with the use of transformers. Primary distribution lines carry this medium voltage power to distribution transformers located near the customer's premises. Distribution transformers again lower the voltage to the utilization voltage used by lighting, industrial equipment and household appliances. Often several customers are supplied from one transformer through secondary distribution lines. Commercial and residential customers are connected to the secondary distribution lines through service drops. Customers demanding a much larger amount of power may be connected directly to the primary distribution level or the subtransmission level.
A thermostat is a regulating device component which senses the temperature of a physical system and performs actions so that the system's temperature is maintained near a desired setpoint.
A dimmer is a device connected to a light fixture and used to lower the brightness of the light. By changing the voltage waveform applied to the lamp, it is possible to lower the intensity of the light output. Although variable-voltage devices are used for various purposes, the term dimmer is generally reserved for those intended to control light output from resistive incandescent, halogen, and compact fluorescent lamps (CFLs) and light-emitting diodes (LEDs). More specialized equipment is needed to dim fluorescent, mercury-vapor, solid-state, and other arc lighting.
Joule heating, also known as resistive, resistance, or Ohmic heating, is the process by which the passage of an electric current through a conductor produces heat.
A compact fluorescent lamp (CFL), also called compact fluorescent light, energy-saving light and compact fluorescent tube, is a fluorescent lamp designed to replace an incandescent light bulb; some types fit into light fixtures designed for incandescent bulbs. The lamps use a tube that is curved or folded to fit into the space of an incandescent bulb, and a compact electronic ballast in the base of the lamp.
Inrush current, input surge current, or switch-on surge is the maximal instantaneous input current drawn by an electrical device when first turned on. Alternating-current electric motors and transformers may draw several times their normal full-load current when first energized, for a few cycles of the input waveform. Power converters also often have inrush currents much higher than their steady-state currents, due to the charging current of the input capacitance. The selection of over-current-protection devices such as fuses and circuit breakers is made more complicated when high inrush currents must be tolerated. The over-current protection must react quickly to overload or short-circuit faults but must not interrupt the circuit when the inrush current flows.
An electrical ballast is a device placed in series with a load to limit the amount of current in an electrical circuit.
Demand response is a change in the power consumption of an electric utility customer to better match the demand for power with the supply. Until recently electric energy could not be easily stored, so utilities have traditionally matched demand and supply by throttling the production rate of their power plants, taking generating units on or off line, or importing power from other utilities. There are limits to what can be achieved on the supply side, because some generating units can take a long time to come up to full power, some units may be very expensive to operate, and demand can at times be greater than the capacity of all the available power plants put together. Demand response seeks to adjust the demand for power instead of adjusting the supply.
Electric heating is a process in which electrical energy is converted directly to heat energy at around 100% efficiency, using rather cheap devices. Common applications include space heating, cooking, water heating and industrial processes. An electric heater is an electrical device that converts an electric current into heat. The heating element inside every electric heater is an electrical resistor, and works on the principle of Joule heating: an electric current passing through a resistor will convert that electrical energy into heat energy. Most modern electric heating devices use nichrome wire as the active element; the heating element, depicted on the right, uses nichrome wire supported by ceramic insulators.
A circulator pump or circulating pump is a specific type of pump used to circulate gases, liquids, or slurries in a closed circuit. They are commonly found circulating water in a hydronic heating or cooling system. Because they only circulate liquid within a closed circuit, they only need to overcome the friction of a piping system.
A brownout is a drop in voltage in an electrical power supply system.
Load management, also known as demand-side management (DSM), is the process of balancing the supply of electricity on the network with the electrical load by adjusting or controlling the load rather than the power station output. This can be achieved by direct intervention of the utility in real time, by the use of frequency sensitive relays triggering the circuit breakers, by time clocks, or by using special tariffs to influence consumer behavior. Load management allows utilities to reduce demand for electricity during peak usage times, which can, in turn, reduce costs by eliminating the need for peaking power plants. In addition, some peaking power plants can take more than an hour to bring on-line which makes load management even more critical should a plant go off-line unexpectedly for example. Load management can also help reduce harmful emissions, since peaking plants or backup generators are often dirtier and less efficient than base load power plants. New load-management technologies are constantly under development — both by private industry and public entities.
Various governments have passed regulations to phase out manufacturing or importation of incandescent light bulbs for general lighting in favor of more energy-efficient alternatives. The regulations are generally based on efficiency, rather than use of incandescent technology. However, it is not unlawful to continue to buy or sell existing bulbs, which are unregulated.
An infinite switch, simmerstat, energy regulator or infinite controller is a type of switch that allows variable power output of a heating element of an electric stove. It is called "infinite" because its average output is infinitely variable rather than being limited to a few switched levels. It uses a bi-metallic strip conductive connection across terminals that disconnects with increased temperature. As current passes through the bimetal connection, it will heat and deform, breaking the connection and turning off the power. After a short time, the bimetal will cool and reconnect. Infinite switches vary the average power delivered to a device by switching frequently between on and off states. They may be used for situations that are not sensitive to such changes, such as the resistive heating elements in electric stoves and kilns.
Nonintrusive load monitoring (NILM), or nonintrusive appliance load monitoring (NIALM), is a process for analyzing changes in the voltage and current going into a house and deducing what appliances are used in the house as well as their individual energy consumption. Electric meters with NILM technology are used by utility companies to survey the specific uses of electric power in different homes. NILM is considered a low-cost alternative to attaching individual monitors on each appliance. It does, however, present privacy concerns.
Voltage optimisation is a term given to the systematic controlled reduction in the voltages received by an energy consumer to reduce energy use, power demand and reactive power demand. While some voltage 'optimisation' devices have a fixed voltage adjustment, others electronically regulate the voltage automatically.
Tankless water heaters — also called instantaneous, continuous flow, inline, flash, on-demand, or instant-on water heaters — are water heaters that instantly heat water as it flows through the device, and do not retain any water internally except for what is in the heat exchanger coil. Copper heat exchangers are preferred in these units because of their high thermal conductivity and ease of fabrication.