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New technology for electrical metering monitoring and control instrumentation
Energy Comers. Mgmt Vol. 24, No. 3, pp. 177-]80, 1984 Printed in Great Britain.All rights reserved
0196-8904/84 $3.00+0.00 Copyright ~, 1984PergamonPress Ltd
NEW TECHNOLOGY FOR ELECTRICAL METERING MONITORING AND CONTROL INSTRUMENTATION']" B. L. CAPEHART Department of Industrial and Systems Engineering, University of Florida, Gainesville, FL 32611, U.S.A. (Received 7 July 1983)
Abetract--Presently, individual instruments are available at reasonable costs for metering, monitoring and controlling the use of electrical energy. Many of these instruments have been developed in the last few years and make varying degrees of use of sophisticated electronic components and microprocessor chips. Performance data collected on the use of these instruments have shown that there are substantial energy and cost savings possible from widespread application of these devices. The purpose of this paper is to enumerate briefly some data on the costs and benefits of instruments which allow time of day and demand metering, monitoring of energy use and cost, direct load control and indirect load control. Finally, an integrated instrument is proposed which combines these varied functions into one low cost device to provide cost effective electrical energy conservation. Electric energy monitors Electric energy meters Customer load control Microprocessor load controllers Innovative electric rates
INTRODUCTION For many years, electric utility service was taken for granted, with few people knowing or caring about electric rate structures or energy management. In the mid 1970's, the economics of electrical energy changed drastically with previously declining electric bills reversing and showing rapid increases. In response to increasing costs and shortages of petroleum fuels, utilities all across the nation are developing and implementing new electric rate structures designed to promote energy conservation and to charge all classes of customers equitably. As a result, a multitude of intelligent devices has come on the market to aid customers in metering, monitoring and controlling their use of electricity. Significant amounts of cost and benefit data have been collected to assess the energy and dollar savings possible by implementing these individual instruments. The results are dependent on specific utility characteristics such as climatic factors and load shapes, but general trends show substantial benefits can accrue from the use of sophisticated metering products. The costs and benefits for such devices to meter, monitor and control electric use directly and indirectly are discussed in the next section.
Direct load control
which performs the complete set of desired tasks of metering, monitoring, and controlling the use of energy. The heart of this integrated function instrument is a microprocessor which allows flexible design functions for metering k w h and kW values with time variable rates, displaying costs of electric energy under complex rates, controlling appliances and devices directly and indirectly, signaling information to both customers and the utility and generally controlling electric energy use to minimize billing costs. The technology to accomplish a wide variety of metering control/display functions is presently available at relatively low cost. The current constraints to development and implementation of such a metering device are not technological, but are economic and behavioral. The cost of such a control/display device is not great based on capabilities that exist in present consumer devices such as home computers or video recorders. A cost of $500 should adequately cover the electronic components of the metering control/display box. The installation cost would be quite variable, depending on whether it was installed in a new or an existing building.
Following the discussion of the costs and benefits of individual instruments is a proposal for the design of a low cost, integrated function metering device
TIME OF DAY AND DEMAND METERING
Until recent years, there was little need to meter electric energy consumption with any device other than a single register kWh meter. Large commercial 1"This paper is based on work funded by the United States and industrial customers have, for some time, had Department of Energy and the Florida Public Service their demand levels in kW recorded for billing purCommission and performed through the Public Utilities poses, but these k w h and kW functions were the Research Center at the University of Florida. The views and opinions of the author do not necessarily state or extent of metering tasks for many years. Since 1970, reflect those of sponsoring organizations, there has been a growing concern with the cost of 177
178
CAPEHART: NEW TECHNOLOGY FOR ELECTRICAL METERING Table 1. Purchase costs of electricmeters Purchase Type cost (5) Type kWh (single register) 30-100 kwh (three register) kWh and demand 70-140 kWh (two register) kWh (two register)
100--210
+ demand kWh (multi-register)
Purchase cost (5) 155-250 240-350 200-500
+ multi-demand
electric energy and the manner in which it is billed, In particular, time of use rates have become widespread in the residential sector and are moving into the commercial and industrial sectors. Demand rates are just moving into the residential sector, usually for large k w h users, Electric meter designs have evolved from single kWh meters with demand to multi-register meters using sophisticated electronics for measuring varied combinations of peak and off-peak kWh and kW values. In general, having meters with a greater number of registers means that more complex rate structures can be implemented. In addition, the inclusion of a clock and calendar allow varied time periods to be included for time or day dependent rate struttures, The costs of electric meters vary widely, depending on the degree of sophistication of the device. This price range starts at around $30 for a single register kWh meter and goes to around $350 for a multiregister, microprocessor-based meter. The following table provides meter cost data as a function of the capability of the various meters [1]. Actual benefit data from utilities having time of use and/or demand rates is very limited and the data that does exist is usually questionable to some degree, Most utilities do not have baseline data to compare to time of use and demand metering benefits. Some results collected during a recent study conducted by the author are given as follows in Table 2 [2].
of the energy consumed during a billing period. The more sophisticated monitors measure, compute and display costs and consumption during on-peak times, off-peak times, and shoulder times, as well as displaying projected costs and consumptions for the next hour, next day and next billing period. The demand in kW can also be monitored and some monitors contain control logic to shed several loads to keep the maximum kW value within a set range. There are several problem areas with digital cost and energy monitors that seem to limit their abilities to be helpful to many customers. One problem is how the customer cost is included in the cost display. Since this is a fixed cost, independent of consumption, it should always be added into the total bill, but doing so in the early part of the billing cycle distorts the cost the customer sees and compares with the energy consumed. Another problem is the fuel adjustment value which is typically unknown at the time of consumption and is constantly changing on a monthly basis. How to communicate the appropriate value of the fuel adjustment in order to add it to the total cost is a difficult and expensive problem. Finally, problems of how to incorporate rate changes are very real and require some means to update periodically the cost data for the display. Still other problems exist [3]. Very few experiments have been conducted to determine the impact on customer behavior from having cost data and consumption data displayed at all times in an easily read format. The largest test
COST AND CONSUMPTION MONITORING
Table 3. Cost of digital display devices Purchase cost
Solid state, digital display devices for showing electric energy cost and consumption are new technologies of the past several years. The capabilities of available devices range from a single cost display to a selectable display of around 20 quantities of costs and consumption. These energy monitors can be connected to single appliances or devices, or can be connected to a whole house or building. The simplest monitor is a digital display of the accumulated cost Table 2. Benefit data for electric meters Type
Demand metering Time of use metering
Benefits (a) 0.5 kW diversified demand reduction for gas/electric home (b) 1.5 kW diversified demand reduction for all electric home 300 kWh reduction on a monthly use of 2500 kWh
Type of display
(5) 100-150 450 400-500
Rateof Consumption Only AccumulatedCost Only Multi-function device (rate, accumulated cost, prediction cost, time of use cost, demand, etc.)
Table 4. Benefits of digital display devices Predicted savingsin cost Source of Information
(5)
U.S. Department of Energy [4] Brookhaven National Laboratory [5]
l0 5-10
Table 5. Costs and benefits of direct load control Water heater diversified demand reduction 0.35-1.2 kW at the time of system peak Air conditioner diversified demand reduction 0.2 l-1.4 kW at time of system peak Cost of radio controlled switches (1979 dollars) 95-5170
CAPEHART: NEW TECHNOLOGY FOR ELECTRICAL METERING Table 6. Costs and benefitsof indirect load control (a) Cost of resideatialenergymanagementsysmns Type Purchase cost (S) Demand limiter/controller 200-2000 TOU controller 300-1725 Multi-functionmicroprocessor(flexible options includingdemand, TOU control) 2000-75,000 (b) Benefitsfor demand pricing? Uncontrolled Controlled consumption
179
Water heaters and air conditioners are the two devices most commonly controlled, with some electric resistance space heaters comprising a distant third group. The costs and benefits o f direct load control have been well documented by many researchers [?]. A summary of cost and benefit data collected by the author is presented in the following table. INDIRECT LOAD CONTROL
consumption
Season Summer
demand(kW) demand(kW) Savings(%) 12.1 8.9 33.7 Spring/Fall 9.2 6.9 24.8 Winter 19.2 9.3 51.3 Average 13.5 8.1 36.3 ?For a 16,000kwh per year customer, (c) Benefitsfor time of use pricing**,§ Uncontrolled Controlled consumption consumption Season cost ($) cost ($) Savings (%) Summer 85.70 73.04 14.8 Spring/Fall 36.26 26.59 26.7 Winter 55.27 42.80 22.6 Average 59.08 47.48 21.4 {:For a 16,000kWh per year customer. §With gg,'2¢pricing, program is currently being conducted by the U.S. Department of Energy which was s u p p o s e d t o have completed results by late 1981. This program is behind schedule and results are not expected until at least late 1982. The benefits of digital display monitors are only estimated at this time, pending the outcome of the extensive U.S. Department of Energy test program [4, 5]. DIRECT LOAD CONTROL Direct load control by a utility is the ability to reduce its system demand on command, usually accomplished by a signal to a customer to shut off certain appliances and devices. A typical direct load control system consists of a radio transmitter controlled by the utility and a set of radio activated switches on customer loads that can be shed without harm or significant loss of service for short times. Direct load control offers relatively precise control over the timing and amount of demand reduction achieved in response to the real time status of a utility's load. The heart of any direct load control system is the communications technology used by the utility to transmit load shedding commands. Four communication systems provide the basis for the vast majority of devices presently in use: radio signals, telephone lines, high frequency power line carrier systems and low frequency power line carrier or ripple systems, Radio control systems using FM transmitters are the prevalent technology in use. Many large residential direct load control systems are in operation across the country, including one with around 200,000 controlled water heaters [6].
Contrasted to direct load control where the utility issues load reduction commands, indirect load control involves the customer controlling load reduction through the use of devices located at the point of service which are not under the control of the utility. Such devices include clock-activated switches, appliance interlocks and demand limiting circuit breakers as well as sophisticated computer-based energy management systems which perform total scheduling and control tasks. Indirect load control is only of value to the customer when rate structures are in effect that include time of day or demand pricing. Under a time of day rate, the goal of the customer is tO minimize the cost of electricity consumed by shifting the greatest possible amount of energy use to the off-peak hours when the rate is low. Typical residential loads that can be deferred to off-peak hours include water heating, clothes washing and drying, dish washing, some space heating and air conditioning and some food refrigeration. With demand pricing, the goal of the customer is to minimize the demand charge for energy consumed by avoiding excessive short term peaks in consumption and to spread the energy consumption as uniformly as possible over the entire day. F o r residential customers, this means limiting the coincident operation of large power consumers such as space heaters, air conditioners, water heaters, clothes dryers and cooking ranges. While clock activated switches and interlocks can provide useful control services in some instances, in general, a more sophisticated control system will be required to handle all of the desired control and scheduling tasks. A computer based energy management system provides the degree of control and flexibility needed to respond to both time of use and demand rates. The use of low cost microcomputers has made it economically feasible to put such computer based energy management systems in individual residences. The cost and benefit data for indirect load control have been collected by the author and computer simulation modeling has been used to predict the cost savings possible under residential time of use and demand rates [8]. This cost and benefit data is given in the following table. AN INTEGRATED INSTRUMENT Cost effective instruments and devices are available for each of the functions of metering, monitoring,
180
CAPEHART: NEW TECHNOLOGY FOR ELECTRICAL METERING
direct load control and indirect load control discussed so far in this paper. However, the technology of microelectronics has not been fully exploited, by any means, in terms of providing a single, low cost device that accomplishes all of these functions. Given the range of sophisticated consumer products that are readily available which do use microelectronic cornponents, one wonders why so little has been done in the energy use and control area. Small, cheap microprocessors form the heart of many recently marketed consumer devices such as personal computers, video recorders, video games and educational devices, Costs of these consumer products have been dropping rapidly, showing the effects of customer interest and the economy of scale from mass production.
services besides electric could also be provided, including gas, water, steam, etc. The basic cost of the integrated energy computer described here should be less than $500 based on a comparison with other consumer devices such as video recorders or personal computers. Installation cost could be greater than the purchase cost depending on whether it was installed during construction of a home or building, or whether it was added to an existing structure. In any event, the technology for such a device is clearly available and requires only the marketing effort to develop customer interest, just as was done for video games and video tape recorders.
With the market success of highly complex, microprocessor-based products in so many areas, extension to the energy metering, monitoring and control area seems to be a relatively obvious one. An integrated device to perform kWh and kW metering
Costs and benefits of energy metering, monitoring and control devices vary greatly, depending on
as a function of time of use, the wide range of cost and consumption monitoring displays, and both direct and indirect load control is clearly feasible and should be no more complex than a home video recorder or a personal computer. Besides the cornmon components of a microprocessor, RAM and ROM memory, input keys and a small display, the integrated device would need input sensors to measure the rate of energy use and would need output switches or relays to control certain energy using devices. The design and implementation of such an integrated device has been proposed elsewhere by the author [9]. A combined device can take advantage of including enough electronic capability to perform all of the metering tasks envisioned at this time, as well as computing and displaying almost any form of customer feedback on energy cost and consumption related to those rate structure. Innovative rate structures, such as flexible time-of-use, demand rates, fuse rates, (or demand limiting rates), inverted block rates, etc, could all be handled with a flexible device which could be easily reprogrammed, or programmed to accept additional functions. Inclusion of sufficient RAM memory and the ability to remove and replace ROM cartridges is all that is required from a hardware consideration. The use of a ROM cartridge L i k e that for a video game provides a means to alter rate structures and rate levels without much effort. When a utility had a rate change, a customer could easily unplug the old ROM cartridge and exchange it for a new one. Obviously, the utility could also send someone to do the replacement, but recent experience with telephone stores shows that many customers are capable of making, and are willing to make, simple equipment changes as long as they are given reasonable instructions. A flexible, low cost energy computer could also be used for other customer services such as fire alarms, intrusion alarms, medical services, etc. Other energy
CONCLUSION
specific devices and specific utilities with their own operating characteristics. However, within these widely varying boundaries, there are well documented savings available for many utilities and many customers. There is no doubt that complex electronic devices have a substantial future in the electric utility enterprise. This paper has identified a number of instances where such devices have documented benefits for utilities and their customers. An obvious next step, in the author's opinion, is to combine the various individual energy meters, monitors and controllers into a single, integrated device which can be produced in volume at low cost. The availability of such an integrated device, or energy computer, should provide a highly cost-effective investment for many utilities and many customers. REFERENCES 1. B. L. Capehart and M. O. Storin, Metering Technology for Innovative Electric Rates, Final Report to the FIorida Public Service Commission on the U.S. Department of Energy, prepared by the Public Utilities Research Center, Univ. of Florida, (1981). 2. Personal communication with Mr G. F. Maese, System Planning Department, Arizona Public Service Company (1982). 3. B. L. Capehart, S. V. Berg and R. L. Sullivan, Proc. 1982 lASTED Syrup on Modeling, Policy and Economics of Energy and Power Systems, Cambridge, Massachuserfs (1982). 4. U. S. Department of Energy Press Release, A Demonstration Program for Energy Cost Indicators 0980). Prepared by the Conservation and Solar Energy office of Buildings and Community Systems, U.S. Department of Energy. 5. Personal communication with Mr Bill Graves, Department of Energy ECI Project Manager, Brookhaven National Laboratory (1982). 6. Survey of Utility Load Management and Energy Conservation Projects, EUS, Inc, ORNL/SUB-77/3509/4 (1978). 7. B. L. Capehart, Energy Systems Policy 6, 151. 8. B. L. Capehart and E. J. Muth, Comput. Industr Engng 6, No. 4 (1982). 9. B. L. Capehart and M. O. Storin, Innovative Electric Rates: Issues in Cost-Benefit Analysis (edited by S. V. Berg), Chap. 15. Lexington Press, Lexington, MA (1982).
0196-8904/84 $3.00+0.00 Copyright ~, 1984PergamonPress Ltd
NEW TECHNOLOGY FOR ELECTRICAL METERING MONITORING AND CONTROL INSTRUMENTATION']" B. L. CAPEHART Department of Industrial and Systems Engineering, University of Florida, Gainesville, FL 32611, U.S.A. (Received 7 July 1983)
Abetract--Presently, individual instruments are available at reasonable costs for metering, monitoring and controlling the use of electrical energy. Many of these instruments have been developed in the last few years and make varying degrees of use of sophisticated electronic components and microprocessor chips. Performance data collected on the use of these instruments have shown that there are substantial energy and cost savings possible from widespread application of these devices. The purpose of this paper is to enumerate briefly some data on the costs and benefits of instruments which allow time of day and demand metering, monitoring of energy use and cost, direct load control and indirect load control. Finally, an integrated instrument is proposed which combines these varied functions into one low cost device to provide cost effective electrical energy conservation. Electric energy monitors Electric energy meters Customer load control Microprocessor load controllers Innovative electric rates
INTRODUCTION For many years, electric utility service was taken for granted, with few people knowing or caring about electric rate structures or energy management. In the mid 1970's, the economics of electrical energy changed drastically with previously declining electric bills reversing and showing rapid increases. In response to increasing costs and shortages of petroleum fuels, utilities all across the nation are developing and implementing new electric rate structures designed to promote energy conservation and to charge all classes of customers equitably. As a result, a multitude of intelligent devices has come on the market to aid customers in metering, monitoring and controlling their use of electricity. Significant amounts of cost and benefit data have been collected to assess the energy and dollar savings possible by implementing these individual instruments. The results are dependent on specific utility characteristics such as climatic factors and load shapes, but general trends show substantial benefits can accrue from the use of sophisticated metering products. The costs and benefits for such devices to meter, monitor and control electric use directly and indirectly are discussed in the next section.
Direct load control
which performs the complete set of desired tasks of metering, monitoring, and controlling the use of energy. The heart of this integrated function instrument is a microprocessor which allows flexible design functions for metering k w h and kW values with time variable rates, displaying costs of electric energy under complex rates, controlling appliances and devices directly and indirectly, signaling information to both customers and the utility and generally controlling electric energy use to minimize billing costs. The technology to accomplish a wide variety of metering control/display functions is presently available at relatively low cost. The current constraints to development and implementation of such a metering device are not technological, but are economic and behavioral. The cost of such a control/display device is not great based on capabilities that exist in present consumer devices such as home computers or video recorders. A cost of $500 should adequately cover the electronic components of the metering control/display box. The installation cost would be quite variable, depending on whether it was installed in a new or an existing building.
Following the discussion of the costs and benefits of individual instruments is a proposal for the design of a low cost, integrated function metering device
TIME OF DAY AND DEMAND METERING
Until recent years, there was little need to meter electric energy consumption with any device other than a single register kWh meter. Large commercial 1"This paper is based on work funded by the United States and industrial customers have, for some time, had Department of Energy and the Florida Public Service their demand levels in kW recorded for billing purCommission and performed through the Public Utilities poses, but these k w h and kW functions were the Research Center at the University of Florida. The views and opinions of the author do not necessarily state or extent of metering tasks for many years. Since 1970, reflect those of sponsoring organizations, there has been a growing concern with the cost of 177
178
CAPEHART: NEW TECHNOLOGY FOR ELECTRICAL METERING Table 1. Purchase costs of electricmeters Purchase Type cost (5) Type kWh (single register) 30-100 kwh (three register) kWh and demand 70-140 kWh (two register) kWh (two register)
100--210
+ demand kWh (multi-register)
Purchase cost (5) 155-250 240-350 200-500
+ multi-demand
electric energy and the manner in which it is billed, In particular, time of use rates have become widespread in the residential sector and are moving into the commercial and industrial sectors. Demand rates are just moving into the residential sector, usually for large k w h users, Electric meter designs have evolved from single kWh meters with demand to multi-register meters using sophisticated electronics for measuring varied combinations of peak and off-peak kWh and kW values. In general, having meters with a greater number of registers means that more complex rate structures can be implemented. In addition, the inclusion of a clock and calendar allow varied time periods to be included for time or day dependent rate struttures, The costs of electric meters vary widely, depending on the degree of sophistication of the device. This price range starts at around $30 for a single register kWh meter and goes to around $350 for a multiregister, microprocessor-based meter. The following table provides meter cost data as a function of the capability of the various meters [1]. Actual benefit data from utilities having time of use and/or demand rates is very limited and the data that does exist is usually questionable to some degree, Most utilities do not have baseline data to compare to time of use and demand metering benefits. Some results collected during a recent study conducted by the author are given as follows in Table 2 [2].
of the energy consumed during a billing period. The more sophisticated monitors measure, compute and display costs and consumption during on-peak times, off-peak times, and shoulder times, as well as displaying projected costs and consumptions for the next hour, next day and next billing period. The demand in kW can also be monitored and some monitors contain control logic to shed several loads to keep the maximum kW value within a set range. There are several problem areas with digital cost and energy monitors that seem to limit their abilities to be helpful to many customers. One problem is how the customer cost is included in the cost display. Since this is a fixed cost, independent of consumption, it should always be added into the total bill, but doing so in the early part of the billing cycle distorts the cost the customer sees and compares with the energy consumed. Another problem is the fuel adjustment value which is typically unknown at the time of consumption and is constantly changing on a monthly basis. How to communicate the appropriate value of the fuel adjustment in order to add it to the total cost is a difficult and expensive problem. Finally, problems of how to incorporate rate changes are very real and require some means to update periodically the cost data for the display. Still other problems exist [3]. Very few experiments have been conducted to determine the impact on customer behavior from having cost data and consumption data displayed at all times in an easily read format. The largest test
COST AND CONSUMPTION MONITORING
Table 3. Cost of digital display devices Purchase cost
Solid state, digital display devices for showing electric energy cost and consumption are new technologies of the past several years. The capabilities of available devices range from a single cost display to a selectable display of around 20 quantities of costs and consumption. These energy monitors can be connected to single appliances or devices, or can be connected to a whole house or building. The simplest monitor is a digital display of the accumulated cost Table 2. Benefit data for electric meters Type
Demand metering Time of use metering
Benefits (a) 0.5 kW diversified demand reduction for gas/electric home (b) 1.5 kW diversified demand reduction for all electric home 300 kWh reduction on a monthly use of 2500 kWh
Type of display
(5) 100-150 450 400-500
Rateof Consumption Only AccumulatedCost Only Multi-function device (rate, accumulated cost, prediction cost, time of use cost, demand, etc.)
Table 4. Benefits of digital display devices Predicted savingsin cost Source of Information
(5)
U.S. Department of Energy [4] Brookhaven National Laboratory [5]
l0 5-10
Table 5. Costs and benefits of direct load control Water heater diversified demand reduction 0.35-1.2 kW at the time of system peak Air conditioner diversified demand reduction 0.2 l-1.4 kW at time of system peak Cost of radio controlled switches (1979 dollars) 95-5170
CAPEHART: NEW TECHNOLOGY FOR ELECTRICAL METERING Table 6. Costs and benefitsof indirect load control (a) Cost of resideatialenergymanagementsysmns Type Purchase cost (S) Demand limiter/controller 200-2000 TOU controller 300-1725 Multi-functionmicroprocessor(flexible options includingdemand, TOU control) 2000-75,000 (b) Benefitsfor demand pricing? Uncontrolled Controlled consumption
179
Water heaters and air conditioners are the two devices most commonly controlled, with some electric resistance space heaters comprising a distant third group. The costs and benefits o f direct load control have been well documented by many researchers [?]. A summary of cost and benefit data collected by the author is presented in the following table. INDIRECT LOAD CONTROL
consumption
Season Summer
demand(kW) demand(kW) Savings(%) 12.1 8.9 33.7 Spring/Fall 9.2 6.9 24.8 Winter 19.2 9.3 51.3 Average 13.5 8.1 36.3 ?For a 16,000kwh per year customer, (c) Benefitsfor time of use pricing**,§ Uncontrolled Controlled consumption consumption Season cost ($) cost ($) Savings (%) Summer 85.70 73.04 14.8 Spring/Fall 36.26 26.59 26.7 Winter 55.27 42.80 22.6 Average 59.08 47.48 21.4 {:For a 16,000kWh per year customer. §With gg,'2¢pricing, program is currently being conducted by the U.S. Department of Energy which was s u p p o s e d t o have completed results by late 1981. This program is behind schedule and results are not expected until at least late 1982. The benefits of digital display monitors are only estimated at this time, pending the outcome of the extensive U.S. Department of Energy test program [4, 5]. DIRECT LOAD CONTROL Direct load control by a utility is the ability to reduce its system demand on command, usually accomplished by a signal to a customer to shut off certain appliances and devices. A typical direct load control system consists of a radio transmitter controlled by the utility and a set of radio activated switches on customer loads that can be shed without harm or significant loss of service for short times. Direct load control offers relatively precise control over the timing and amount of demand reduction achieved in response to the real time status of a utility's load. The heart of any direct load control system is the communications technology used by the utility to transmit load shedding commands. Four communication systems provide the basis for the vast majority of devices presently in use: radio signals, telephone lines, high frequency power line carrier systems and low frequency power line carrier or ripple systems, Radio control systems using FM transmitters are the prevalent technology in use. Many large residential direct load control systems are in operation across the country, including one with around 200,000 controlled water heaters [6].
Contrasted to direct load control where the utility issues load reduction commands, indirect load control involves the customer controlling load reduction through the use of devices located at the point of service which are not under the control of the utility. Such devices include clock-activated switches, appliance interlocks and demand limiting circuit breakers as well as sophisticated computer-based energy management systems which perform total scheduling and control tasks. Indirect load control is only of value to the customer when rate structures are in effect that include time of day or demand pricing. Under a time of day rate, the goal of the customer is tO minimize the cost of electricity consumed by shifting the greatest possible amount of energy use to the off-peak hours when the rate is low. Typical residential loads that can be deferred to off-peak hours include water heating, clothes washing and drying, dish washing, some space heating and air conditioning and some food refrigeration. With demand pricing, the goal of the customer is to minimize the demand charge for energy consumed by avoiding excessive short term peaks in consumption and to spread the energy consumption as uniformly as possible over the entire day. F o r residential customers, this means limiting the coincident operation of large power consumers such as space heaters, air conditioners, water heaters, clothes dryers and cooking ranges. While clock activated switches and interlocks can provide useful control services in some instances, in general, a more sophisticated control system will be required to handle all of the desired control and scheduling tasks. A computer based energy management system provides the degree of control and flexibility needed to respond to both time of use and demand rates. The use of low cost microcomputers has made it economically feasible to put such computer based energy management systems in individual residences. The cost and benefit data for indirect load control have been collected by the author and computer simulation modeling has been used to predict the cost savings possible under residential time of use and demand rates [8]. This cost and benefit data is given in the following table. AN INTEGRATED INSTRUMENT Cost effective instruments and devices are available for each of the functions of metering, monitoring,
180
CAPEHART: NEW TECHNOLOGY FOR ELECTRICAL METERING
direct load control and indirect load control discussed so far in this paper. However, the technology of microelectronics has not been fully exploited, by any means, in terms of providing a single, low cost device that accomplishes all of these functions. Given the range of sophisticated consumer products that are readily available which do use microelectronic cornponents, one wonders why so little has been done in the energy use and control area. Small, cheap microprocessors form the heart of many recently marketed consumer devices such as personal computers, video recorders, video games and educational devices, Costs of these consumer products have been dropping rapidly, showing the effects of customer interest and the economy of scale from mass production.
services besides electric could also be provided, including gas, water, steam, etc. The basic cost of the integrated energy computer described here should be less than $500 based on a comparison with other consumer devices such as video recorders or personal computers. Installation cost could be greater than the purchase cost depending on whether it was installed during construction of a home or building, or whether it was added to an existing structure. In any event, the technology for such a device is clearly available and requires only the marketing effort to develop customer interest, just as was done for video games and video tape recorders.
With the market success of highly complex, microprocessor-based products in so many areas, extension to the energy metering, monitoring and control area seems to be a relatively obvious one. An integrated device to perform kWh and kW metering
Costs and benefits of energy metering, monitoring and control devices vary greatly, depending on
as a function of time of use, the wide range of cost and consumption monitoring displays, and both direct and indirect load control is clearly feasible and should be no more complex than a home video recorder or a personal computer. Besides the cornmon components of a microprocessor, RAM and ROM memory, input keys and a small display, the integrated device would need input sensors to measure the rate of energy use and would need output switches or relays to control certain energy using devices. The design and implementation of such an integrated device has been proposed elsewhere by the author [9]. A combined device can take advantage of including enough electronic capability to perform all of the metering tasks envisioned at this time, as well as computing and displaying almost any form of customer feedback on energy cost and consumption related to those rate structure. Innovative rate structures, such as flexible time-of-use, demand rates, fuse rates, (or demand limiting rates), inverted block rates, etc, could all be handled with a flexible device which could be easily reprogrammed, or programmed to accept additional functions. Inclusion of sufficient RAM memory and the ability to remove and replace ROM cartridges is all that is required from a hardware consideration. The use of a ROM cartridge L i k e that for a video game provides a means to alter rate structures and rate levels without much effort. When a utility had a rate change, a customer could easily unplug the old ROM cartridge and exchange it for a new one. Obviously, the utility could also send someone to do the replacement, but recent experience with telephone stores shows that many customers are capable of making, and are willing to make, simple equipment changes as long as they are given reasonable instructions. A flexible, low cost energy computer could also be used for other customer services such as fire alarms, intrusion alarms, medical services, etc. Other energy
CONCLUSION
specific devices and specific utilities with their own operating characteristics. However, within these widely varying boundaries, there are well documented savings available for many utilities and many customers. There is no doubt that complex electronic devices have a substantial future in the electric utility enterprise. This paper has identified a number of instances where such devices have documented benefits for utilities and their customers. An obvious next step, in the author's opinion, is to combine the various individual energy meters, monitors and controllers into a single, integrated device which can be produced in volume at low cost. The availability of such an integrated device, or energy computer, should provide a highly cost-effective investment for many utilities and many customers. REFERENCES 1. B. L. Capehart and M. O. Storin, Metering Technology for Innovative Electric Rates, Final Report to the FIorida Public Service Commission on the U.S. Department of Energy, prepared by the Public Utilities Research Center, Univ. of Florida, (1981). 2. Personal communication with Mr G. F. Maese, System Planning Department, Arizona Public Service Company (1982). 3. B. L. Capehart, S. V. Berg and R. L. Sullivan, Proc. 1982 lASTED Syrup on Modeling, Policy and Economics of Energy and Power Systems, Cambridge, Massachuserfs (1982). 4. U. S. Department of Energy Press Release, A Demonstration Program for Energy Cost Indicators 0980). Prepared by the Conservation and Solar Energy office of Buildings and Community Systems, U.S. Department of Energy. 5. Personal communication with Mr Bill Graves, Department of Energy ECI Project Manager, Brookhaven National Laboratory (1982). 6. Survey of Utility Load Management and Energy Conservation Projects, EUS, Inc, ORNL/SUB-77/3509/4 (1978). 7. B. L. Capehart, Energy Systems Policy 6, 151. 8. B. L. Capehart and E. J. Muth, Comput. Industr Engng 6, No. 4 (1982). 9. B. L. Capehart and M. O. Storin, Innovative Electric Rates: Issues in Cost-Benefit Analysis (edited by S. V. Berg), Chap. 15. Lexington Press, Lexington, MA (1982).