Load management
Encyclopedia
Load management 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 circuit breakers (ripple control), 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 plant
s. In addition, peaking power plants also often require hours to bring on-line, presenting challenges should a plant go off-line unexpectedly. Load management can also help reduce harmful emission, since peaking plants or backup generators are often dirtier and less efficient than base load power plant
s. New load-management technologies are constantly under development — both by private industry and public entities.
in Huntsville, Alabama
, developed a sensor monitoring system which used digital transmission for security, fire, and medical alarm systems as well as meter reading capabilities for all utilities. This technology was a spin-off of his patented automatic telephone line identification system, now known as caller ID
. In, 1974, Mr. Paraskevakos was awarded a U.S. Patent for this technology.
At the request of the Alabama Power Company
, Mr. Paraskevakos developed a load management system along with automatic meter reading technology. In doing so, he utilized the ability of the system to monitor the speed of the watt power meter disc and, consequently, power consumption. This information, along with the time of day, gave the power company the ability to instruct individual meters to manage water heater and air conditioning consumption in order to prevent peaks in usage during the high consumption portions of the day. For this approach, Mr. Paraskevakos was awarded multiple patents.
that cannot be effectively stored in bulk, it must be generated, distributed, and consumed immediately. When the load on a system approaches the maximum generating capacity, network operators must either find additional supplies of energy or find ways to curtail the load, hence load management. If they are unsuccessful, the system will become unstable and blackouts
can occur.
Long-term load management planning may begin by building sophisticated models to describe the physical properties of the distribution network (i.e. topology, capacity, and other characteristics of the lines), as well as the load behavior. The analysis may include scenarios that account for weather forecasts, the predicted impact of proposed load-shed commands, estimated time-to-repair for off-line equipment, and other factors.
The utilization of load management can help a power plant achieve a higher plant load factor, a measure of average capacity utilization. Plant load factor is a measure of the output of a power plant compared to the maximum output it could produce. Plant load factor is often defined as the ratio of average load to capacity or the ratio of average load to peak load in a period of time. A higher load factor is advantageous because a power plant may be less efficient at low load factors, a high load factor means fixed costs are spread over more kWh of output (resulting in a lower price per unit of electricity), and a higher load factor means greater total output. If the power load factor is affected by non-availability of fuel, maintenance shut-down, unplanned break down, or reduced demand (as consumption pattern fluctuate throughout the day), the generation has to be adjusted, since grid energy storage
is often prohibitively expensive.
Smaller utilities that buy power instead of generating their own find that they can also benefit by installing a load control system. The penalties they must pay to the energy provider for peak usage can be significantly reduced. Many report that a load control system can pay for itself in a single season.
Demand response
places the "on-off switch" in the hands of the consumer using devices such as a smart grid controlled load control switch
. While many residential consumers pay a flat rate for electricity year-round, the utility's costs actually vary constantly, depending on demand, the distribution network, and composition of the company's electricity generation portfolio. In a free market, the wholesale price of energy varies widely throughout the day. Demand response programs such as those enabled by smart grids attempt to incentivize the consumer to limit usage based upon cost concerns. As costs rise during the day (as the system reaches peak capacity and more expensive peaking power plants are used), a free market economy
should allow the price to rise. A corresponding drop in demand for the commodity should meet a fall in price. While this works for predictable shortages, many crises develop within seconds due to unforeseen equipment failures. They must be resolved in the same time-frame in order to avoid a power blackout. Many utilities who are interested in demand response have also expressed an interest in load control capability so that they might be able to operate the "on-off switch" before price updates could be published to the consumers.
The application of load control technology continues to grow today with the sale of both radio frequency
and powerline communication based systems. Certain types of smart meter
systems can also serve as load control systems.
The largest residential load control system in the world is found in Florida and is managed by Florida Power and Light. It utilizes 800,000 Load Control Transponders (LCTs) and controls 1,000 MW of electrical power (2,000 MW in an emergency). FPL has been able to avoid the construction of numerous new power plants due to their load management programs.
, New Zealand, the United Kingdom
, Germany
, and South Africa
. Ripple control involves superimposing a higher-frequency signal (usually between 100 and 1600 Hz) onto the standard 50–60 Hz of the main power signal. When receiver devices attached to non-essential residential or industrial loads receive this signal, they shut down the load until the signal is disabled or another frequency signal is received.
Early implementations of ripple control occurred during World War II
in various parts of the world using a system that communicates over the electrical distribution system. Ripple control systems are generally paired with a two- (or more) tiered pricing system, whereby electricity is more expensive during peak times (evenings) and cheaper during low-usage times (early morning).
Affected residential devices will vary by region, but may include residential electric hot-water heaters, air conditioners, pool pumps, or crop-irrigation pumps. In a distribution network outfitted with load control, these devices are outfitted with communicating controllers that can run a program that limits the duty cycle of the equipment under control. Consumers are usually rewarded for participating in the load control program by paying a reduced rate for energy. Proper load management by the utility allows them to practice load shedding to avoid rolling blackout
s and reduce costs.
, United Kingdom
and France
, the power grids routinely use privately held, emergency diesel generators in load management schemes
In the UK, night storage heaters are used to increase the load by about 5 GW to accommodate the nuclear programme. There is also a programme that allows industrial loads to be disconnected using circuit breakers triggered automatically by frequency sensitive relays fitted on site. This operates in conjunction with Standing Reserve, a programme using diesel generators.
These can also be remotely switched using BBC Radio 4 Longwave Radio teleswitch
.
in Germany are loaded with a lower tariff electricity, mainly during night and afternoon hours. The switch and the two-tariff electricity meter as well are remote controlled by using of ripple control through the main powerline or by the European radio teleswitching system based on longwave radio signals.
Peaking power plant
Peaking power plants, also known as peaker plants, and occasionally just "peakers," are power plants that generally run only when there is a high demand, known as peak demand, for electricity.-Peak hours:...
s. In addition, peaking power plants also often require hours to bring on-line, presenting challenges should a plant go off-line unexpectedly. Load management can also help reduce harmful emission, since peaking plants or backup generators are often dirtier and less efficient than base load power plant
Base load power plant
Baseload is the minimum amount of power that a utility or distribution company must make available to its customers, or the amount of power required to meet minimum demands based on reasonable expectations of customer requirements...
s. New load-management technologies are constantly under development — both by private industry and public entities.
Brief history
In 1972, Theodore George “Ted” Paraskevakos, while working for BoeingBoeing
The Boeing Company is an American multinational aerospace and defense corporation, founded in 1916 by William E. Boeing in Seattle, Washington. Boeing has expanded over the years, merging with McDonnell Douglas in 1997. Boeing Corporate headquarters has been in Chicago, Illinois since 2001...
in Huntsville, Alabama
Huntsville, Alabama
Huntsville is a city located primarily in Madison County in the central part of the far northern region of the U.S. state of Alabama. Huntsville is the county seat of Madison County. The city extends west into neighboring Limestone County. Huntsville's population was 180,105 as of the 2010 Census....
, developed a sensor monitoring system which used digital transmission for security, fire, and medical alarm systems as well as meter reading capabilities for all utilities. This technology was a spin-off of his patented automatic telephone line identification system, now known as caller ID
Caller ID
Caller ID , also called calling line identification or calling number identification or Calling Line Identification Presentation , is a telephone service, available in analog and digital phone systems and most Voice over Internet Protocol applications, that transmits a caller's number to...
. In, 1974, Mr. Paraskevakos was awarded a U.S. Patent for this technology.
At the request of the Alabama Power Company
Alabama Power Company
Alabama Power Company, headquartered in Birmingham, Alabama, is a company in the southern United States that provides electricity service to 1.3 million homes, businesses, and industries in the southern two-thirds of Alabama. It is one of four U.S...
, Mr. Paraskevakos developed a load management system along with automatic meter reading technology. In doing so, he utilized the ability of the system to monitor the speed of the watt power meter disc and, consequently, power consumption. This information, along with the time of day, gave the power company the ability to instruct individual meters to manage water heater and air conditioning consumption in order to prevent peaks in usage during the high consumption portions of the day. For this approach, Mr. Paraskevakos was awarded multiple patents.
Advantages and Operating Principles
Since electrical energy is a form of energyEnergy
In physics, energy is an indirectly observed quantity. It is often understood as the ability a physical system has to do work on other physical systems...
that cannot be effectively stored in bulk, it must be generated, distributed, and consumed immediately. When the load on a system approaches the maximum generating capacity, network operators must either find additional supplies of energy or find ways to curtail the load, hence load management. If they are unsuccessful, the system will become unstable and blackouts
Power outage
A power outage is a short- or long-term loss of the electric power to an area.There are many causes of power failures in an electricity network...
can occur.
Long-term load management planning may begin by building sophisticated models to describe the physical properties of the distribution network (i.e. topology, capacity, and other characteristics of the lines), as well as the load behavior. The analysis may include scenarios that account for weather forecasts, the predicted impact of proposed load-shed commands, estimated time-to-repair for off-line equipment, and other factors.
The utilization of load management can help a power plant achieve a higher plant load factor, a measure of average capacity utilization. Plant load factor is a measure of the output of a power plant compared to the maximum output it could produce. Plant load factor is often defined as the ratio of average load to capacity or the ratio of average load to peak load in a period of time. A higher load factor is advantageous because a power plant may be less efficient at low load factors, a high load factor means fixed costs are spread over more kWh of output (resulting in a lower price per unit of electricity), and a higher load factor means greater total output. If the power load factor is affected by non-availability of fuel, maintenance shut-down, unplanned break down, or reduced demand (as consumption pattern fluctuate throughout the day), the generation has to be adjusted, since grid energy storage
Grid energy storage
Grid energy storage refers to the methods used to store electricity on a large scale within an electrical power grid. Electrical energy is stored during times when production exceeds consumption and the stores are used at times when consumption exceeds production...
is often prohibitively expensive.
Smaller utilities that buy power instead of generating their own find that they can also benefit by installing a load control system. The penalties they must pay to the energy provider for peak usage can be significantly reduced. Many report that a load control system can pay for itself in a single season.
Comparisons to Demand Response
When the decision is made to curtail load, it is done so on the basis of system reliability. The utility in a sense "owns the switch" and sheds loads only when the stability or reliability of the electrical distribution system is threatened. The utility (being in the business of generating, transporting, and delivering electricity) will not disrupt their business process without due cause. Load management, when done properly, is non-invasive, and imposes no hardship on the consumer.Demand response
Demand response
In electricity grids, demand response is similar to dynamic demand mechanisms to manage customer consumption of electricity in response to supply conditions, for example, having electricity customers reduce their consumption at critical times or in response to market prices...
places the "on-off switch" in the hands of the consumer using devices such as a smart grid controlled load control switch
Load control switch
A Load control switch is a remotely controlled relay that is placed on home appliances which consume large amounts of electricity, such as air conditioner units and electric water heaters....
. While many residential consumers pay a flat rate for electricity year-round, the utility's costs actually vary constantly, depending on demand, the distribution network, and composition of the company's electricity generation portfolio. In a free market, the wholesale price of energy varies widely throughout the day. Demand response programs such as those enabled by smart grids attempt to incentivize the consumer to limit usage based upon cost concerns. As costs rise during the day (as the system reaches peak capacity and more expensive peaking power plants are used), a free market economy
Market economy
A market economy is an economy in which the prices of goods and services are determined in a free price system. This is often contrasted with a state-directed or planned economy. Market economies can range from hypothetically pure laissez-faire variants to an assortment of real-world mixed...
should allow the price to rise. A corresponding drop in demand for the commodity should meet a fall in price. While this works for predictable shortages, many crises develop within seconds due to unforeseen equipment failures. They must be resolved in the same time-frame in order to avoid a power blackout. Many utilities who are interested in demand response have also expressed an interest in load control capability so that they might be able to operate the "on-off switch" before price updates could be published to the consumers.
The application of load control technology continues to grow today with the sale of both radio frequency
Radio frequency
Radio frequency is a rate of oscillation in the range of about 3 kHz to 300 GHz, which corresponds to the frequency of radio waves, and the alternating currents which carry radio signals...
and powerline communication based systems. Certain types of smart meter
Smart meter
A smart meter is usually an electrical meter that records consumption of electric energy in intervals of an hour or less and communicates that information at least daily back to the utility for monitoring and billing purposes. Smart meters enable two-way communication between the meter and the...
systems can also serve as load control systems.
The largest residential load control system in the world is found in Florida and is managed by Florida Power and Light. It utilizes 800,000 Load Control Transponders (LCTs) and controls 1,000 MW of electrical power (2,000 MW in an emergency). FPL has been able to avoid the construction of numerous new power plants due to their load management programs.
Ripple Control
Ripple control is the most common form of load control, and is used in many countries around the world, including AustraliaAustralia
Australia , officially the Commonwealth of Australia, is a country in the Southern Hemisphere comprising the mainland of the Australian continent, the island of Tasmania, and numerous smaller islands in the Indian and Pacific Oceans. It is the world's sixth-largest country by total area...
, New Zealand, the United Kingdom
United Kingdom
The United Kingdom of Great Britain and Northern IrelandIn the United Kingdom and Dependencies, other languages have been officially recognised as legitimate autochthonous languages under the European Charter for Regional or Minority Languages...
, Germany
Germany
Germany , officially the Federal Republic of Germany , is a federal parliamentary republic in Europe. The country consists of 16 states while the capital and largest city is Berlin. Germany covers an area of 357,021 km2 and has a largely temperate seasonal climate...
, and South Africa
South Africa
The Republic of South Africa is a country in southern Africa. Located at the southern tip of Africa, it is divided into nine provinces, with of coastline on the Atlantic and Indian oceans...
. Ripple control involves superimposing a higher-frequency signal (usually between 100 and 1600 Hz) onto the standard 50–60 Hz of the main power signal. When receiver devices attached to non-essential residential or industrial loads receive this signal, they shut down the load until the signal is disabled or another frequency signal is received.
Early implementations of ripple control occurred during World War II
World War II
World War II, or the Second World War , was a global conflict lasting from 1939 to 1945, involving most of the world's nations—including all of the great powers—eventually forming two opposing military alliances: the Allies and the Axis...
in various parts of the world using a system that communicates over the electrical distribution system. Ripple control systems are generally paired with a two- (or more) tiered pricing system, whereby electricity is more expensive during peak times (evenings) and cheaper during low-usage times (early morning).
Affected residential devices will vary by region, but may include residential electric hot-water heaters, air conditioners, pool pumps, or crop-irrigation pumps. In a distribution network outfitted with load control, these devices are outfitted with communicating controllers that can run a program that limits the duty cycle of the equipment under control. Consumers are usually rewarded for participating in the load control program by paying a reduced rate for energy. Proper load management by the utility allows them to practice load shedding to avoid rolling blackout
Rolling blackout
A rolling blackout, also referred to as load shedding, is an intentionally-engineered electrical power outage where electricity delivery is stopped for non-overlapping periods of time over geographical regions. Rolling blackouts are a last-resort measure used by an electric utility company in order...
s and reduce costs.
Examples of schemes
In many countries, including United StatesUnited States
The United States of America is a federal constitutional republic comprising fifty states and a federal district...
, United Kingdom
United Kingdom
The United Kingdom of Great Britain and Northern IrelandIn the United Kingdom and Dependencies, other languages have been officially recognised as legitimate autochthonous languages under the European Charter for Regional or Minority Languages...
and France
France
The French Republic , The French Republic , The French Republic , (commonly known as France , is a unitary semi-presidential republic in Western Europe with several overseas territories and islands located on other continents and in the Indian, Pacific, and Atlantic oceans. Metropolitan France...
, the power grids routinely use privately held, emergency diesel generators in load management schemes
New Zealand
New Zealand has for many years had a system of load management based on rippled control, allowing the utility to switch off or on domestic and commercial water heaters.France
France has an EJP tariff, which allows it to disconnect certain loads and to encourage consumers to disconnect certain loads. This tariff is no longer available for new clients (as of July 2009). The Tempo tariff also includes different types of days with different prices, but has been discontinued for new clients as well (as of July 2009). Reduced prices during nighttime are available for customers for a higher monthly fee.United Kingdom
Rltec in the UK in 2009 reported that domestic refrigerators are being sold fitted with their dynamic load response systems. In 2011 it was announced that the Sainsbury supermarket chain will use dynamic demand technology on their heating and ventilation equipment.In the UK, night storage heaters are used to increase the load by about 5 GW to accommodate the nuclear programme. There is also a programme that allows industrial loads to be disconnected using circuit breakers triggered automatically by frequency sensitive relays fitted on site. This operates in conjunction with Standing Reserve, a programme using diesel generators.
These can also be remotely switched using BBC Radio 4 Longwave Radio teleswitch
Radio teleswitch
A Radio Teleswitch is a device used in the United Kingdom to allow electricity suppliers to switch large numbers of electricity meters between different tariffs, by broadcasting an embedded signal in broadcast radio signals...
.
Germany
Existing storage heaterStorage heater
A storage heater or heat bank is an electrical heater which stores thermal energy during the evening, or at night when base load electricity is available at lower cost, and releases the heat during the day as required.-Principle of operation:...
in Germany are loaded with a lower tariff electricity, mainly during night and afternoon hours. The switch and the two-tariff electricity meter as well are remote controlled by using of ripple control through the main powerline or by the European radio teleswitching system based on longwave radio signals.
See also
- Energy management systemEnergy management systemAn energy management system is a system of computer-aided tools used by operators of electric utility grids to monitor, control, and optimize the performance of the generation and/or transmission system...
- Calculating the cost of the UK Transmission network: cost per kWh of transmission
- Calculating the cost of back up: See spark spreadSpark spreadThe spark spread is the theoretical gross margin of a gas-fired power plant from selling a unit of electricity, having bought the fuel required to produce this unit of electricity...
- National Grid Reserve Service
- Energy use and conservation in the United KingdomEnergy use and conservation in the United KingdomEnergy use in the United Kingdom stood at 3,894.6 kilogrammes of oil equivalent per capita in 2005 compared to a world average of 1,778.0. In 2008, total energy consumed was 9.85 exajoules - around 2% of the estimated 474 EJ worldwide total...
- National Grid Reserve Service
- Control of the National Grid
- Relative cost of electricity generated by different sources
- Diesel-electric transmission
- Motor-generatorMotor-generatorA motor-generator is a device for converting electrical power to another form. Motor-generator sets are used to convert frequency, voltage, or phase of power. They may also be used to isolate electrical loads from the electrical power supply line...
- Three-phase electric powerThree-phase electric powerThree-phase electric power is a common method of alternating-current electric power generation, transmission, and distribution. It is a type of polyphase system and is the most common method used by grids worldwide to transfer power. It is also used to power large motors and other heavy loads...
- Load bankLoad bankA load bank is a device which develops an electrical load, applies the load to an electrical power source and converts or dissipates the resultant power output of the source....
- Wet stackingWet stackingWet stacking is a condition in diesel engines in which not all the fuel is burned and passes on into the exhaust side of the turbocharger and on into the exhaust system. The word "stacking" comes from the term "stack" for exhaust pipe or chimney stack...