WO2008059528A2

WO2008059528A2 - A prepaid smart card operated electronic energy meter with online load optimizer for solar power application

Info

Publication number: WO2008059528A2
Application number: PCT/IN2007/000508
Authority: WO
Inventors: Joydeb Roy Chowdhury
Original assignee: Council Of Scientific & Industrial Research
Priority date: 2006-11-16
Filing date: 2007-10-26
Publication date: 2008-05-22
Also published as: ZA200903660B; WO2008059528A3

Abstract

The prepaid smart card operated electronic energy meter with online load optimizer for solar power application, comprises in combination a step down transformer, a power measuring & recording module with embedded processor capable of computing and sending signals to respective output interface modules, a smart card reader capable of physically linking the said embedded processor and a rechargeable smart card, a display interface module, a load controller relay and alarm indicator. This prepaid smart card operated electronic energy meter enables prepayment of electricity through prepaid memory card including online intelligent load monitoring and cut off feature through resident software, which will be most suitable for inefficient solar photovoltaic power plant. Due to interactive software the system can log as well compute the energy and subsequent money for the consumer to pay and display the same through LCD display screen. This makes it more communicative with the user and thus user can access the exact amount of consumption in terms of the currency, which in turn helps to optimize the power consumption.

Description

"A PREPAID SMART CARD OPERATED ELECTRONIC ENERGY METER WITH ONLINE LOAD OPTIMIZER FOR SOLAR POWER APPLICATION"

The present invention relates to a prepaid smart card operated electronic energy meter with online load optimizer for solar power application. The system is particularly useful for solar power application where energy generated from solar radiation is not efficient compared to conventional thermal power.

The prepaid smart card operated electronic energy meter of the present invention can also be used in any electrical power application. But the system is particularly useful for solar power application where energy generated is not efficient compared to conventional thermal power.

Conventional electromechanical meters have dominated the monitoring of electrical power and energy. With the present system many state electricity boards in India are experiencing a financial crunch in which revenues from sale of power is insufficient to cover the cost of providing electricity to consumers. Further, consumers have to face incorrect billing due to human error and wait in long queues to pay their bills, causing a lot of inconvenience to the customer & the utility. The bill collection system is critical in case of solar power where the power is not efficient compared to the conventional power system.

The prior art covering literature, patents and industrial survey reveals that for energy measurement the conventional electromechanical meters, electronic meters used which are not intelligent enough to solve various problems related to the solar power plant like:

(1) Load optimization.

(2) Uncertainty in availability of power. (3) Revenue payment.

In case of electromechanical and electronic energy meters the power consumption and subsequent bill payment is done through manual reading of the meter. This process is laborious cost intensive and error prone. The entire revenue collection system is cost intensive and almost an appreciable percentage of total power generation cost is spent in revenue collection -which is not economical and indirectly affects the consumers.

The system is more complicated in rural areas or hilly areas where the transportation is much more critical and cost intensive both for meter reading and bill payment to the electricity office. Thus the post paid metering system where the payment is done after power consumption is seems to be much cost intensive and inefficient method. The two ways communication one for meter reading by the power generating and distributing authority and other is payment bill by consumer at the electricity office. These two cost intensive and laborious job is directly eliminated through pre payment of bill through smart card at the time of card procurement and no intervention of electricity authority is needed for meter reading.

Reference may be made to United States Patent No. US5146067 entitled "Prepayment metering system using encoded purchase cards from multiple locations" published on 8^th September, 1992. In this a prepayment system for dispensing utilities using magnetic-stripe cards is disclosed wherein an accounting computer in a central office is used in conjunction with point-of-sale machines for encrypting a value message which is written onto the magnetic- stripe of a magnetic-stripe card. The value message contains information relating to the amount of utilities purchased by the customer, the utility rates, the site identification number, and a unique password formed by the site number, a hidden number, and the transaction number. The magnetic-stripe card is carried by mail or in person to the consumer's home or office and inserted into a magnetic-stripe card reader attached to microprocessor-based utility control device. This utility control device is capable of reading and decoding the magnetic-stripe card and storing the value information into memory for use in monitoring the utility usage of the customer and disconnecting or connecting the utility based on the amount of utilities purchased. Reference may also be made to European patent No. EP319825 entitled "Prepaid commodity system", published on 14^th June, 1989, wherein the invention concerns a card activated prepayment and metering system for the sale of a utility service. Therein is described a card-activated prepayment metering system where distributors are sold bulk service credits which they then resell in smaller quantities to individual customers. Customers are issued magnetic striped cards upon which information may be stored and from which information may be retrieved. Distributors issue credits on the cards which are later read by a customer's home terminal. Periodically, credit information is dumped from the distributor's terminal to a central computer. Similarly, audit information is periodically read and dumped from a customer's terminal to the central computer. The computer controls each customer's terminal through information broadcast over an FM transmitter, which is received by a receiver in each customer's terminal.

Reference may also be drawn to United States Patent No. US6529883 entitled "Prepayment energy metering system with two-way smart card communications", published on 4^th March, 2003, wherein a pre-payment energy metering system uses two-way smart card communications. Secure power line carrier communications are provided at the consumer locations communication between a customer terminal and the utility meter. Two-way secure communication of data is provided through the use of a smart card or memory card which conveys data from the utility service provider to the customer's terminal and also conveys information from the customer's terminal back to the utility. The pre-payment power system allows consumers to pay for electricity prior to consumption through the use of the smart card which is loaded with funds at a fully automatic point-of-sale (POS) terminal or at the utility service providers staffed customer service center. Back office software interfaces between the POS terminals and customer service centers, and utility service providers customer information systems.

Among the above mentioned patents, in first two patents, United States Patent No. US5146067 and European patent No. EP319825, the main drawback is the use of magnetic-stripe card. Smart card has more memory compared to magnetic-stripe card. Smart card is able to store approximately 80 times more information than magnetic stripe card. The initial cost of smart card is relatively higher than that of magnetic stripe card due to the difference of initial costs between the two technologies. But when the differences in expected life span and capabilities are considered, the running cost of smart card decreases significantly. Second and most important drawback in the above mentioned patents is that, there is no provision of online load optimization. Since online load optimization will not be possible, these will not be suitable for use in a solar power system. This is particularly so in the case of a system like solar power system, which works under some uncertainty and constrain of availability of sunlight, thus intelligent online load optimization is required to ensure the power availability. In the third patent, United States Patent No. US6529883, though first drawback is eliminated by using smart card but second drawback of no provision of online load optimization is still present.

The present system of conventional meter is not user interactive so that user cannot get information about the online energy consumption during a particular period of time. As the system is post paid based - monthly payment of electricity is done only after consumption of power and after getting the bill. Thus the power generating and distributing authority does not have any control over it. The main control goes to the consumer who is also not aware of the online power consumption.

Reference may be drawn to US patent publication no.: 20040008023, titled: Real-time charging electronic watt-hour meter, wherein disclosed is a real-time charging electronic watt-hour meter, which includes an electric power sensor for sensing the quantity of electric power used, a card reader into/from which a prepayment card is inserted/ejected, and a rate charging processor for calculating the power rate using the quantity of power used and a predetermined charging program and for deducting the power rate from the amount of the prepayment card, thereby charging the power rate in real time. US patent publication no.: 20040008023, primarily deals with the real-time smart card recharging methods depending on the power consumed by the consumer assuming the demand will not create a constraint for the power source. Only the charging rate will vary according to the consumption of power.

The major disadvantages of this type of payment system are:

(1) Transparency to the consumer is poor.

(2) Wastages of electricity as well as paper for bill and

(3) Real time Load optimization is not possible particularly where the power availability is uncertain and the distribution of power is less efficient like in solar power system, compared to the conventional system.

From the hitherto known prior art, it is seen that there is a definite need for a beneficial prepaid system compared to conventional post paid. The prepaid system is to be provided for solar application and the system is to be much more effective compared to conventional post paid. Further, the prepaid system is to take care of the uncertainty of availability of power and can be optimized through automatic intelligent load controller built in the energy meter. The main responsibility of revenue payment will be with the power consumer instead of power generating and distributing authority. The customer will have to procure a prepaid memory card and insert the card with proper value in a smart card socket of the meter. The intelligence of the electronics module will check the validity of the card and power will automatically come if the valid card is properly inserted.

The main object of the present invention is to provide a prepaid smart card operated electronic energy meter with online load optimizer for solar power application, which obviates the drawbacks of the hitherto known prior art as detailed above.

Another object of the present invention is to provide an effective revenue collection system for solar-based power system, where uncertainty of power availability is present. Yet another object of the present invention is to provide power regulation through a transparent communication between the consumer and the power-metering device through online display module where the current consumption is displayed in terms of KWH and Rs.

Yet another object of the present invention is to provide the power through prepaid smart card for better access of power as per own requirement of the consumer.

In the present invention, the prepaid smart card operated electronic energy meter with online load optimizer for solar power application which has been provided will be capable of enabling prepayment of electricity through prepaid memory card and online intelligent load monitoring and cut off feature through resident software, which will be most suitable for inefficient solar photovoltaic power plant. Suitable hardware and subsequent software has been designed for domestic and industrial meter. Due to interactive software the system can log as well compute the energy and subsequent money for the consumer to pay and display the same through LCD display screen. This makes it more communicative with the user and thus user can access the exact amount of consumption in terms of the currency, which in turn helps to optimize the power consumption.

The novelty of this invention is that the consumer can purchase power according to the requirement on prepayment basis. When a smart card is inserted in the existing socket the embedded hardware with inbuilt software reads the information in terms of Rupees and KWH through the smart card reader and stores in it's memory. The system also measures and records online power consumption with the help of resident software. As the power consumption is increases the balance Rupees decreases, which is recorded. Once the meter reads the information from the smart card, the card memory is empty and it is ready to be refilled, though all information are stored in the protected zone of the smart card memory. The novel features of this invention have been enabled by the non- obvious inventive steps such as, the invented device is capable to measure online power consumption from the pulse input, compute through embedded software and convert the consumed KWH to Rupees after multiplying by the constant power tariff, which is also programmable and preset-able and subsequently display online power consumption in terms of consumed KWH and balance Rupees through embedded hardware circuit and embedded software.

The prepaid smart card operated electronic energy meter with online load optimizer for solar power application of the present invention is illustrated in figures-1 to 5 of the drawings accompanying this specification, wherein:

Figure-1 represents a simplified diagram illustrating a prepayment energy metering system.

Figure-2 represents front view (2a) and side view (2b) of the prepaid energy meter of the present invention.

Figure-3 represents a simplified functional block diagram of prepayment energy meter in accordance with the preferred embodiment of the present invention.

Figure-4 represents the circuit diagram of an embodiment of the embedded hardware used in prepaid smart card operated electronic energy meter of the present invention with online load optimizer for solar power application.

Figure-5 represents the flow chart of the software program used in the embedded hardware.

Figure-1 of the drawings depicts a simplified diagram illustrating a prepayment energy metering system, wherein customer residence (8) receives electricity from solar power station (1) through a step up transformer (2), overhead lines (3), step down transformer (4), cable interface (5), junction box (6), via cable (7) at prepaid energy meter (9). The pre-paid energy meter (9) is coupled by power lines (10) within the consumer residence with distribution box (11) which distributes power to the loads (12).

The front and side views of the prepaid energy meter is depicted in figure-2 (a) and (b), respectively. There is a smart card socket (14) through which smart card is inserted into the meter (13). The smart card is physically linked with the embedded processor through the smart card socket (14). There is a LCD display screen (15) which displays online power consumption in terms of consumed KWH and balance Rupees. When the balance Rupees amount reaches 25%, the alarm LED (16) starts blinking in order to alert the customer from power cut off by the meter (13).

Figure-3 of the drawings shows a simplified functional block diagram of prepayment energy meter in accordance with the preferred embodiment of the present invention. The input to the prepaid energy meter is single-phase AC supply which is stepped down by a step down transformer (17). This stepped down supply goes to the power measuring & recording unit with embedded hardware (19), within which energy is monitored and subsequent output pulse is generated. This pulse is monitored and processed by the embedded processor in the power measuring & recording unit (19). A smart card (21) is physically linked with the processor in the embedded hardware in the power measuring & recording unit (19) through a smart card reader (22). Depending on the power consumption the embedded processor generates two signals. One signal is used to display online power consumption in terms of consumed KWH and balance Rupees through LCD display module (15) and the alarm LED (16) starts to blink when balance Rupees amount reaches 25%. The second signal goes to a load controller relay (23) so that when load (24) exceeds the predefined level, power is automatically cut off.

Figure-4 shows the circuit diagram of an embodiment of the embedded hardware used in prepaid smart card operated electronic energy meter of the present invention with online load optimizer for solar power application. The circuit of the embedded hardware (19) shown in figure-4 consists of LCD display module (15), alarm LED (16), smart card reader (22), a load controller relay (23), micro- controller(25), opto-coupler(26), buzzer(27) and power monitoring chip(28).

In figure-5 of the drawings is given the flow chart of the embedded software program of the embedded hardware in the power measuring & recording unit (19). The flow chart shown in figure.5 gives the details of the software programming. The software checks whether the smart card has been inserted or not. When the smart card is inserted smart card reader(22) reads the information stored in the smart card(21) and sends information to the micro-controller(25). The micro-controller(25) checks the validity of the smart card(21) through software and accordingly sends instruction to the load controller relay(23) to connect the load (24) with supply. The micro-controller(25) computes consumed power, available power and remaining balance in terms of rupees with the help of the software and displays on LCD display(15) and simultaneously the micro- controller(25) also optimizes the load with the help of inbuilt resident software. Ultimately the micro-controller(25) gives alarm through LED(16) and buzzer(27), if the consumed power is more than 75% of the purchased power. If now the smart card(21) is refilled and inserted into the meter then the power supply will continue. Otherwise, when consumed power becomes equal to the purchased power the power supply is tripped.

Accordingly the present invention provides a prepaid smart card operated electronic energy meter with online load optimizer for solar power application, which comprises in combination a step down transformer, a power measuring & recording module with embedded software driven hardware capable of computing and sending signals to respective output interface modules such as a load controller relay and a display interface module coupled alarm indicator; the said embedded hardware having embedded software driven micro-controller connected to a smart card reader capable of physically linking a rechargeable smart card; characterized in that the embedded software driven hardware in the power measuring & recording unit consists in combination a micro-controller, an opto-coupler, a power monitoring chip, a load controller relay, a LCD display module, an alarm indicator such as a coupled LED and buzzer and a smart card reader.

In another embodiment of the present invention, the prepaid smart card operated electronic energy meter with online load optimizer for solar power application, consists in combination a step down transformer (17), a power measuring & recording module with embedded software driven hardware (19), a LCD display module (15), an alarm LED (16), a smart card reader (22) and a load controller relay (23); characterized in that the output of the said step down transformer (17) being connected to the said power measuring & recording module with embedded hardware (19) capable of monitoring and generating respective signals to the load controller relay (23), LCD display module (15) and the alarm LED (16); the said embedded hardware (19) having embedded software driven micro-controller (25) connected to the said smart card reader (22) capable of physically linking a rechargeable smart card (21).

In yet another embodiment of the present invention, the power measuring & recording module with embedded software driven hardware (19) receives signals from input interface units consisting of power conditioning and modulation unit and opto-coupler(26) and computes and sends signal to respective output interface modules such as load controller relay (23), LCD display(15), LED(16) and buzzer(27).

In still another embodiment of the present invention, the embedded hardware (19) consists in combination a software driven micro-controller(25), an opto- coupler(26), a power monitoring chip(28), a load controller relay(23), a LCD display module(15), an alarm indicator such as a coupled LED(16) and buzzer(27) and a smart card reader(22); wherein AC power supply is fed through the said opto-coupler(26) to the said software driven micro-controller(25) connected to the said smart card reader(22), the output of the micro- controller(25) being connected respectively to the said load controller relay(23), the said power monitoring chip(28), the said LCD display module(15) and to the said alarm indicator having a coupled LED(16) and buzzer(27). In yet another embodiment of the present invention, the input to the prepaid energy meter is single-phase AC supply of voltage in the range of 220 volts to 240 volts, which is stepped down by step down transformer to a level in the range of 5volts to 9 volts, suitable for the energy meter.

In still yet another embodiment of the present invention, the smart card reader

(22) physically links a rechargeable smart card (21) with the embedded software driven micro-controller (25) in the power measuring & recording unit (19).

In a further embodiment of the present invention, the embedded software driven hardware is capable of computing and converting the consumed KWH to Rupees after multiplying by the preset-able constant power tariff and subsequently displaying online power consumption in terms of consumed KWH and balance Rupees through the LCD display module (15).

In a yet further embodiment of the present invention, the LCD display module (15) displays the balance amount of money in Rupees (Rs.) and consumed power in kilowatt-hour (KWH).

In a still further embodiment of the present invention, the load controller relay

(23) fitted at the output stage, cuts off power automatically when the load (24) exceeds a pre-set power drawl limit.

In another embodiment of the present invention, the alarm LED (16) starts to blink when 75% of the total currency is consumed.

The present invention provides a novel way to measure electrical energy with the help of an embedded system based user interactive hardware module with inbuilt resident software in order to make the system more intelligent and user friendly. The embedded hardware consists of smart card reader(22), micro-controller(25), opto-coupler(26), buzzer(27), LED(16), load controller relay(23), LCD display(15), power monitoring chip(28). The flow chart shown in figure-5 of the drawings gives the details of the software programming. The software checks whether the smart card has been inserted or not. When the smart card is inserted smart card reader(22) reads the information stored in the smart card(21) and sends those information to the micro-controller(25). The micro-controller(25) checks the validity of the smart card(21) through software and accordingly sends instruction to the load controller relay(23) to connect the load with supply. The micro-controller(25) computes consumed power, available power and remaining balance in terms of rupees with the help of the software and display on LCD display(15) and simultaneously the micro-controller(25) also optimize the load with the help of inbuilt resident software. Ultimately the micro-controller(25) gives alarm through LED(16) and buzzer(27) if the consumed power is more than 75% of the purchased power. If now the smart card(21) is refilled and inserted into the meter then the power supply will continue. Otherwise, when consumed power becomes equal to the purchased power the power supply is tripped.

The essential constructional features of the prepaid smart card operated electronic energy meter with online load optimizer for solar power application are:

a) The prepaid smart card operated electronic energy meter with online load optimizer for solar power application comprises a step down transformer (17), a power measuring & recording module with embedded hardware (19), a smart- card reader (22), a LCD display module (15), a load controller relay (23), an alarm LED (16).

b) In the prepaid smart card operated electronic energy meter with online load optimizer for solar power application system, the step down transformer (17) steps down the single-phase 230 V supply voltage to 5 V, which is suitable for the energy meter operation. c) In the prepaid smart card operated electronic energy meter with online load optimizer for solar power application system, the secondary voltage of the transformer when goes to power measuring & recording module with embedded hardware (19), a pulse is generated by the hardware circuitry, which is fed to the software driven embedded hardware where it is measured and recorded.

d) In the prepaid smart card operated electronic energy meter with online load optimizer for solar power application system, the smart card reader (22) interfaces the smart card with the power measuring & recording module with embedded hardware (19).

e) In the prepaid smart card operated electronic energy meter with online load optimizer for solar power application system, embedded hardware and associated in built software of the power measuring & recording module with embedded hardware (19) compute and convert the consumed KWH to Rupees after multiplying by the constant power tariff which is also programmable and preset-able and subsequently display online. Power consumption in terms of consumed KWH and balance Rupees through the LCD display module (15)

f) In the prepaid smart card operated electronic energy meter with online load optimizer for solar power application system, the load controller relay (23) at the output stage cuts off power when the consumer exceeds a preset power drawl limit.

g) In the prepaid smart card operated electronic energy meter with online load optimizer for solar power application system, the alarm LED (16) blinks when 75% of the total currency has been consumed to alert the consumer.

h) In the prepaid smart card operated electronic energy meter with online load optimizer for solar power application system, the procurement of smart card is done as per user's choice through a card-refilling unit. The feature, which is present in the prepaid smart card operated electronic energy meter of the present invention is online load optimizer for solar power application, but not present in the hitherto known prior art devices. In the present invention the online load optimizer is the load controller relay (23) at the output stage which is capable of cutting off power when the consumer exceeds a preset power drawl limit.

The power drawl limit is set by the power generating and distributing authority keeping in mind the seasonal variation of solar power generation. For instance in rainy season solar power generation will be less and in summer solar power generation will be more. So, power drawl limit in rainy season will be less than that of in the summer. In this way by setting proper limit power can supplied to each customer even when the generation is less.

The novelty of this invention is that the consumer can purchase power according to the requirement on prepayment basis. When a smart card is inserted in the existing socket the embedded hardware with inbuilt software reads the information in terms of Rupees and KWH through the smart card reader and stores in it's memory. The system also measures and records online power consumption with the help or resident software. As the power consumption is increased the balance Rupees is decreased which is recorded. Once the meter reads the information from the smart card, it's memory is empty and it is ready to be refilled, though all information are stored in the protected zone of the smart card's memory. The non-obvious inventive steps are as follows:

(i) The system is capable to measure online power consumption from the pulse input, compute through in built software and convert the consumed KWH to Rupees after multiplying by the constant power tariff, which is also programmable and preset-able and subsequently display online power consumption in terms of consumed KWH and balance Rupees through a suitable hardware circuit and resident software. (ii) When the consumed power exceeds the upper cut off limit, the system gives one alarm so that, the consumer can remove some load. If the consumer removes some load the supply of power continues, otherwise the supply is cut off.

The displayable parameters related to online power consumption is much more meaning full compared to the present electromechanical type energy meter. The distribution of solar power can be optimized automatically as per power distributors' requirement through setting an upper cut-off limit inserted in the smart card at the time of purchase.

The system is capable to measure online power consumption from the pulse input, compute through in-built software and convert the consumed KWH to Rupees after multiplying by the constant power tariff, which is also programmable and preset-able and subsequently display online power consumption in terms of consumed KWH and balance Rupees. These features consist the non-obvious inventive steps which enable realization of Novelty.

The following example is given by way of illustration of the working of the invention in actual practice and therefore should not be construed to limit the scope of the present invention.

Example-1

The smart card was initially refilled with an amount of Rs.100 through a PC based refilling unit and inserted into the socket in the meter. The meter checked the validity of the card and on finding the card to be valid it immediately connected to the power to the consumer.

The power tariff was: Rs.2.50 per KW.

Therefore, the available power was: 100/2.5 = 40 KW. LCD display screen showed: Balance: Rs. 100.00 and Consumed Power: 0 KW.

Then as per consumption of the power the value of the card decreased and the consumed power increased. As the balance amount reached Rs.25.00 the alarm LED started to blink and finally the power line was cut off, as the card was not refilled and inserted to the meter.

In operation the intelligent meter continuously monitors the load connected at the output stage. If the load increases the presentable upper limit the power will automatically cutoff.

The present invention provides a novel way to measure electrical energy with the help of an embedded system based user interactive hardware module with inbuilt resident software in order to make the system more intelligent and user friendly.

The main advantages of the present invention are: 1. The solar power can be sold to the consumer through a prepaid smart card.

2. The power line of the consumer can be activated by the smart card as and when required by the smart card.

3. The card can be sold from the power generating authority or any authorized agent of the power generator.

4. The card can be refilled anytime after one insertion to the smart card socket.

5. The online power consumption is visible through the LCD display screen, which helps the consumer to access the power consumption according to that the consumer can optimize the power consumption, which can directly save the power.

6. The pre settable upper power cutoff limit will trip the power automatically when the consumer exceeds the upper limit. This helps to distribute the power to all other consumers.

Claims

1. A smart card operated electronic energy meter with online load optimizer for solar power application, which comprises in combination a step down transformer, a power measuring & recording module with embedded software driven hardware capable of computing and sending signals to respective output interface modules such as a load controller relay and a display interface module coupled alarm indicator; the said embedded hardware having embedded software driven micro-controller connected to a smart card reader capable of physically linking a rechargeable smart card; characterized in that the embedded software driven hardware in the power measuring & recording unit consists in combination a micro-controller, an opto-coupler, a power monitoring chip, a load controller relay, a LCD display module, an alarm indicator such as a coupled LED and buzzer and a smart card reader.

2. A prepaid smart card operated electronic energy meter with online load optimizer for solar power application, according to claim 1 , consists in combination a step down transformer (17), a power measuring & recording module with embedded software driven hardware (19), a LCD display module (15), an alarm LED (16), a smart card reader (22) and a load controller relay (23); characterized in that the output of the said step down transformer (17) being connected to the said power measuring & recording module with embedded hardware (19) capable of monitoring and generating respective signals to the load controller relay (23), LCD display module (15) and the alarm LED (16); the said embedded hardware (19) having embedded software driven micro-controller (25) connected to the said smart card reader

(22) capable of physically linking a rechargeable smart card (21).

3. A prepaid smart card operated electronic energy meter according to claims 1- 2, wherein the power measuring & recording module with embedded software driven hardware (19) receives signals from input interface units consisting of power conditioning and modulation unit and opto-coupler(26) and computes and sends signal to respective output interface modules such as load controller relay (23), LCD display(15), LED(16) and buzzer(27).

4. A prepaid smart card operated electronic energy meter according to claims 1- 3, wherein the embedded hardware (19) consists in combination a software driven micro-controller(25), an opto-coupler(26), a power monitoring chip(28), a load controller relay(23), a LCD display module(15), an alarm indicator such as a coupled LED(16) and buzzer(27) and a smart card reader(22); wherein AC power supply is fed through the said opto-coupler(26) to the said software driven micro-controller(25) connected to the said smart card reader(22), the output of the micro-controller(25) being connected respectively to the said load controller relay(23), the said power monitoring chip(28), the said LCD display module(15) and to the said alarm indicator having a coupled LED(16) and buzzer(27).

5. A prepaid smart card operated electronic energy meter according to claims 1- 4, wherein the input to the prepaid energy meter is single-phase AC supply of voltage in the range of 220 volts to 240 volts, which is stepped down by step down transformer to a level in the range of 5volts to 9 volts, suitable for the energy meter.

6. A prepaid smart card operated electronic energy meter according to claims 1-

5, wherein the smart card reader (22) physically links a rechargeable smart card (21) with the embedded software driven micro-controller (25) in the power measuring & recording unit (1§).

7. A prepaid smart card operated electronic energy meter according to claims 1-

6, wherein the embedded software driven hardware is capable of computing and converting the consumed KWH to Rupees after multiplying by the preset- able constant power tariff and subsequently displaying online power consumption in terms of consumed KWH and balance Rupees through the LCD display module (15).

8. A prepaid smart card operated electronic energy meter according to claims 1-

7, wherein the load controller relay (23) fitted at the output stage, cuts off power automatically when the load (24) exceeds a pre-set power drawl limit.

9. A prepaid smart card operated electronic energy meter according to claims 1-

8, wherein the alarm LED (16) starts to blink when 75% of the total currency is consumed.