Patent Publication Number: US-2002013689-A1

Title: Electric power generation process and apparatus

Description:
CROSS-REFERENCES TO RELATED APPLICATIONS  
     [0001] This invention claims the benefit of U.S. Provisional Application No. 60/205,289 filed May 19, 2000, the contents of which are hereby incorporated by reference. 
    
    
     
       BACKGROUND OF THE INVENTION  
       [0002] 1. Field of the Invention  
       [0003] This invention relates generally to processes and apparatuses employed to generate electric power, and particularly to solar, wind, or other ecologically friendly distributed electric power generation processes and apparatuses.  
       [0004] 2. Description of the Related Art  
       [0005] Residential electricity service is broken down into three categories: generation, transmission, and distribution. Power plants produce electricity (generation), which is transmitted to customers via wires owned by utilities (transmission and distribution). Thus, a customer&#39;s electric bill may show an amount reflecting a generation charge (for example, the generation price per KWh paid by the customer multiplied by the number of KWh consumed) and an amount reflecting a transmission and distribution charge (for example, the transmission and distribution price per KWh paid by the customer multiplied by the number of KWh consumed)  
       [0006] In a conventional regulated market, utility distribution companies (UDCs) bill customers a bundled rate for electricity service defined as the sum of generation, transmission, and distribution charges associated with their usage. In deregulated markets, customers can choose to purchase the generation portion of their bills (i.e., what resources are used to produce the power) from UDCs or electricity service providers (ESPs). In either case, UDCs charge customers regulated rates for transmission and distribution, as they own the wires needed for delivery of electricity.  
       [0007] A number of states, including California, offer customers the opportunity to generate power on the premises of their homes and businesses. Solar (photovoltaic) systems are commonly installed for such purposes. When electric output exceeds on-site demand the electric meter operates to decrement the total power consumption indicated on the meter. The reduction in the indicated consumption corresponds to the surplus generated. The meter increments when the on-site demand exceeds the electric output of the solar or other generation system. Thus, net metering enables a customer to only pay for the difference between their total annual power consumption and the annual power output from the on-site generation system.  
       [0008] Net-metered customers effectively reduce their bills by replacing UDC or ESP electricity with self-generated power. However, as in California, UDCs are often not required to purchase surplus power. Therefore, a customer receives no benefit if the customer generates an annual net surplus power (i.e. generates more power in a year than the customer consumes). Consequently, the value of each KWh of electricity generated has the same value per KWh as the combination of the price per KWh paid for generation and price per KWh paid for transmission and distribution until the customer generates, on an annual basis sufficient power to provide for the customers annual power consumption. Thereafter, the power generated has no cash value for the customer.  
       [0009]FIG. 1 contains a table that provides an example of the impact of net-metering on a hypothetical customer that installs a roof top solar (photovoltaic) power generation system. While the example demonstrates electricity bill savings of 42%, the payback period, the period of time over which the solar system generates enough savings to recover the installation costs, for a residential solar system is still well over ten years. It should be noted that these savings are for demonstration only, and the actual amount will only be determined in the field, based on system sizing and orientation, regional solar resource, and electricity prices.  
       [0010] Therefore, there is a need, particularly when electric demand exceeds electric generating capacity in some parts of the United States, for a process and apparatus whereby the payback period for a solar, wind, or other power generation system can be reduced. A reduced payback period is expected to provide motivation for the installation of electric power generation capacity.  
       SUMMARY OF THE INVENTION  
       [0011] The invention provides an electric power generation system. The system includes an electric power generator. A second electric meter is connected to the power generator and the electric power consumer. The second meter measures the electric power provided by the power generation system. A first electric meter is connected to a distribution power line. The power line supplies electric power from an electric grid and receives surplus power from the electric power generator. Thus, the first meter measures the net electric power provided to the electric power consumer through the electric power line.  
       [0012] The invention also provides an electric power generation system where a first meter is connected to an electric power line. The power line supplies electric power from the electric grid. The first meter measures the electric power utilized by the electric power consumer. A second electric meter is connected between the power generation system and either the electric grid, a utility side of the first meter, or a connection point between the first meter and the power line. The second meter measures the electric power provided by the power generation system.  
       [0013] The invention provides a method of purchasing electric power from an electric power customer who also generates electricity by setting a price per unit amount of electric power for electric power generated by the electric power customer at a price per unit amount of electric power that exceeds a generation price per unit amount of electric power paid by the electric power customer for electric power consumed. The generated electric power is purchased from the electric power customer at the set price per unit amount of electric power  
       [0014] The invention provides a method of billing for electric power consumed and paying for electric power produced. The method includes charging an electric power consumer a generation charge for the total electric power consumed, the charge determined by multiplying a first rate by the amount of electric power consumed or estimated to have been consumed. In addition, the electric power consumer is paid or credited a generation fee, the fee determined by multiplying a second rate by the amount of electric power generated or estimated to have been generated, the second rate being higher than the first rate.  
       [0015] Some ecologically-friendly ESP&#39;s market electricity blends-electricity service based on power generated by a mixture of renewable (or other accepted ecologically friendly) resources. In practice this means that the ecologically friendly ESP schedules the delivery of electricity to the power grid for customers with a promise that the electricity delivered is generated by specific resources. For example, a blend could be 95% small hydroelectric and 5% solar. By blending more expensive resources (e.g., solar) with less costly resources (e.g., small hydroelectric), an ecologically friendly ESP helps advance renewable energy development and keep the costs of its blends at reasonable levels. 
     
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
     [0016] The accompanying drawings incorporated in and forming part of the specification illustrate several aspects of the present invention, and together with the description explain the principles of the invention. In the drawings:  
     [0017]FIG. 1 illustrates the prior art process of net metering  
     [0018]FIG. 2 illustrates the process of the present invention.  
     [0019]FIG. 3 illustrates a first embodiment of the apparatus of the present invention.  
     [0020]FIG. 4 illustrates a second embodiment of the apparatus of the present invention.  
     [0021]FIG. 5 illustrates a third embodiment of the apparatus of the present invention.  
     [0022]FIG. 6 illustrates a fourth embodiment of the apparatus of the present invention.  
     [0023]FIG. 7 illustrates a flow chart for a first process for performing the present invention.  
     [0024]FIG. 8 illustrates a flow chart for a second process for performing the present invention. 
    
    
     [0025] Reference will now be made in detail to the present preferred embodiment of the invention, examples of which are illustrated in the accompanying drawings.  
     DETAILED DESCRIPTION OF INVENTION  
     [0026] The present invention offers a process and apparatus that improves the economics of solar, wind, and other electric generation systems.  
     [0027] With this invention, an ESP or UDC effectively treats a solar, wind, or other electric generation system as a small power plant and enters into a power purchase agreement (PPA) with the owner of the system. Each PPA specifies a price per kWh and the term of the contract. This arrangement may add a second meter to measure the generation system&#39;s output. In lieu of adding a second meter, it&#39;s possible to estimate system output (based on system size, orientation, and regional solar resource).  
     [0028]FIG. 2 illustrates an example where the ESP or UDC delivers electricity to the customer and charges the customer based on total consumption. The customer also sells solar power, in this example, to the ESP or UDC from which the customer purchases electricity. In this example, the ESP sells 6,000 kWh of its electricity blend and simultaneously purchases 2,500 kWh of solar output at prices above the cost of the blend.  
     [0029] As with net metering, UDCs charge for the transmission and distribution associated with the net delivered power (total power consumed less power generated) as measured in kWh.  
     [0030] Because the scenario illustrated in FIG. 2 provides a smaller net electric cost, a greater annual savings, and/or a revenue stream to the customer, the economics of the rooftop solar system are improved. The numbers provided in FIG. 2 are for demonstration only. Actual costs and savings will vary based on numerous factors and may have larger or smaller impacts than shown.  
     [0031] Consequently, this invention can reduce the payback period for solar, wind, and other power generation systems and thus increase the likelihood that a customer would purchase a solar, wind or other power generation system. Therefore, the economics of such systems are improved, and the market broadened.  
     [0032]FIG. 3 illustrates a first embodiment of the apparatus that may be used to implement the present invention under a current net-metered arrangement. A customer  10  uses the electric power generated by a solar, wind, or other electric power generator  20 . Customer  10  may be a residential customer or a corporate customer. Electric power provided by an ESP or UDC is provided to customer  10  through an electric meter  30  that is connected to the electric grid with power line  32 . In this embodiment, the generator  20  is connected to customer  10  on the customer side of meter  30 . Consequently, when the power generated by generator  20  exceeds the demand by customer  10  the meter  30  operates to decrement the total power consumption indicated on the meter. The reduction in the indicated consumption corresponds to the surplus power generated. The meter increments when the on-site demand exceeds the electric output of the solar or other generation system.  
     [0033] In this embodiment, it is preferred that customer  10  purchase the electricity from the same ESP or UDC to which the solar, wind, or other electric power is sold. Since there is only a single meter, the ESP or UDC and the customer would estimate the amount of power generated in a given period of time. This estimate could be used in a yearly, monthly, quarterly, or other periodicity calculation to estimate the total power generated and the total power consumed for that period. The customer  10  could then receive a payment or credit for the power generated as illustrated in FIG. 2. This estimation process may require regulatory changes or acceptance by customers.  
     [0034]FIG. 4 illustrates a second embodiment of an apparatus that may be used to implement the present invention. Customer  10  uses the electric power generated by a solar, wind, or other electric power generator  20 . Customer  10  may be a residential customer or a corporate customer. Electric power provided by a ESP or UDC is provided to customer  10  through an electric meter  30  that is connected to the electric grid with power line  32 . In this embodiment, the system  20  is connected through a second meter  40  to customer  10  on the customer side of meter  30 . Consequently, when the power generated by generator  20  exceeds the demand by customer  10  the meter  30  operates to decrement the total power consumption indicated on the meter. The reduction in the indicated consumption corresponds to the surplus power generated. The meter increments when the on-site demand exceeds the electric output of the solar or other generator.  
     [0035] In this embodiment it is also preferred that customer  10  purchase the electricity from the same ESP or UDC to which the solar, wind, or other electric power is sold. Since there is a second meter  40  located between the generator  20  and the customer  10 , the ESP or UDC and the customer do not need to estimate the amount of power generated in a given period of time. The reading of the second meter  40  would be used to periodically determine the power generated by generator  20 . The reading of the first meter  30  would determine the power consumed from the electric grid and would be utilized to determine the transmission and distribution costs for that period. A combination of the readings from both meter  30  and second meter  40  would be used, in this embodiment, to determine the total power consumed. The consumer  10  could then be billed for the total power consumed and receive a payment or credit for the power generated as illustrated in FIG. 2.  
     [0036]FIG. 5 illustrates a third embodiment of an apparatus that may be employed to implement the present invention. A customer  10  uses either electric power generated by a solar, wind, or other electric power generator  20  or from the electric grid through power line  32 . Customer  10  may be a residential customer or a corporate customer. Electric power provided by the ESP or UDC from whom customer  10  purchases their power is provided to customer  10  through an electric meter  30  that is connected to the electric grid with power line  32 . In this embodiment, the system  20  is connected through a second meter  40  either directly to the electric grid, between the grid and meter  30 , or on the utility side of meter  30 .  
     [0037] In this embodiment it is preferred that customer  10  purchase the electricity from a ESP or UDC different from the ESP or UDC to which the solar, wind, or other electric power is sold. This embodiment may, however, be utilized when customer  10  both purchases power form and sells power to the same ESP or UDC. Since the second meter  40  measures the power generated by generator  20 , the ESP or UDC and the customer do not need to estimate the amount of power generated in a given period of time. The reading of the second meter  40  would be used to periodically determine the power generated. The reading of the first meter  30  would determine the power consumed from the electric grid and would be utilized to determine the total cost for the electric power used by consumer  10 . The second meter  40  would be used in this embodiment to determine the total power generated. Customer  10  could then receive a payment from the ESP or UDC to which the power generated power was sold. This embodiment may be utilized when the ESP or UDC that was willing to purchase the solar, wind, or other electric power did not sell electric power in the state in which the customer  10  was located. This embodiment, however, may reduce the benefit to customer  10  since customer  10  now pays the transmission and distribution charge for the total power consumed instead of the net power consumed. The increase in the transmission and distribution charge, however, could be offset by the ESP or UDC paying a higher rate for the power purchased from customer  10 .  
     [0038]FIG. 6 illustrates a third embodiment of an apparatus that may be employed in the present invention. Customer  10  uses either electric power generated by a solar, wind, or other electric power generator  20  or from the electric grid through power line  32 . Customer  10  may be a residential customer or a corporate customer. Electric power provided by an ESP or UDC together with power generated from the solar, wind, or other electric power generator  20  is provided to customer  10  through an electric meter  30  that is connected to the electric grid with power line  32 . In this embodiment, the generator  20  is connected either directly to the electric grid or between the grid and meter  30 .  
     [0039] In this embodiment it is preferred that customer  10  purchase the electricity from a ESP or UDC different from the ESP or UDC to which the solar, wind, or other electric power is sold. This embodiment may, however, be utilized when customer  10  both purchases power form and sells power to the same ESP or UDC. Since generator  20  does not have a meter, the ESP or UDC buying the power generated from generator  20  and the customer need to estimate the amount of power generated in a given period of time. The reading of the first meter  30  would determine the power consumed from the electric grid and would be utilized to determine the total cost for the electric power used by consumer  10 . The estimate would be used in this embodiment to determine the total power generated. Customer  10  could then receive a payment from the ESP or UDC to which the power generated was sold. This embodiment may be utilized when the ESP or UDC that was willing to purchase the solar, wind, or other electric power did not sell electric power in the state in which the consumer  10  was located. This embodiment, however, may reduce the benefit to customer  10  since customer  10  now pays the transmission and distribution charge for the total power consumed instead of the net power consumed. The increase in the transmission and distribution charge, however, could be offset by the ESP or UDC paying a higher rate for the power purchased from customer  10 . This embodiment, however, may be difficult to implement in the United States given the current ISO requirement for generators&#39; meter data.  
     [0040]FIGS. 7 and 8 illustrate block diagrams for processes that may be utilized in the above described embodiments. FIG. 7 provides a block diagram of a process where the ESP or UDC sets the rate for the electric power generated by the customer  10  with generator  20  at a rate that is higher than the generation rate paid by the customer  10  for the electric power consumed by the customer  10  in step S 1 . By setting the rates in this manner the expected payback period for the generator  20  is reduced. This rate difference is also shown in FIG. 2. The ESP or UDC would then purchase the electric power from the customer  10  at the set price in step S 2 . The ESP or UDC may sell electric power to customer  10  in step S 3 . While it may be desired, as discussed above, to buy and sell power to the same ESP or UDC it is not required.  
     [0041]FIG. 8 provides a second block diagram for a second process utilized in the present invention. This is the preferred process when the ESP or UDC that provided power to customer  10  also buys the power generated by customer  10  with generator  20 . In this diagram, an ESP or UDC charges customer  10  for their total electrical power consumption in step S 10 . The ESP or UDC also pays or credits customer  10  for the power generated with generator  20 . The rate paid by the ESP to customer  10  for the power generated by generator  20  exceeds the generation rate paid by the customer  10  to the ESP or UDC for the power consumed or used by customer  10 . Since the rate paid by the ESP or UDC is greater that the generation rate paid by the customer  10  the payback period for generator  20  is shorter than the payback period using net metering. In net metering customer  10  is effectively paid by the ESP or UDC the same generation rate that the customer  10  pays the UDC or ESP (see FIG. 1). The ESP or UDC may charge the customer  10  a transmission and distribution charge. This charge may be on either the electric power consumed by customer  10  or on the net power provided by the ESP or UDC (net power provided is the power consumed reduced by the power generated). In the event that the transmission and distribution charge is based on the net power provided then customer  10  would pay a reduced transmission and distribution charge compared to a transmission and distribution charge based on the total power consumed. The reduced charge is shown in FIG. 2.  
     [0042] In summary, numerous benefits have been described which results from the invention. The foregoing description of the several embodiments of the invention has been presented for the purposes of illustration and description. It is not intended to be exhaustive or to limit the invention to a precise form disclosed. Obvious modifications or variations are possible in light of the above teachings. The embodiments were chosen in order to best illustrate the principles of the invention and its practical application to thereby enable one of ordinary skill in the art to utilize the invention in various embodiments and with various modifications as suited to the particular use contemplated. It is intended that the scope of the invention be defined by the claims appended hereto.