Patent Application
20100194202
This invention relates to an integrated solar electric power generation system.
Compared with most other energy sources, solar energy is cleaner and more available. The supply of solar energy from its source, the Sun, is the most abundant. Solar light energy can be converted to electricity to power households, buildings, factories, appliances, and other places or devices where electrical power is needed. Although solar powered applications in space have been in existence for decades, terrestrial residential or industrial use of solar electric power generation systems to power a household or a building is still relatively limited. High cost of solar electric power systems and complexity in the installation and connection of such systems to existing electrical systems and application electrical power loads present challenges to potential customers of solar electric power systems.
Existing solar electric power systems for residential or industrial use carry a high entry cost. For example, the cost of a 2 kilowatt (KW) photovoltaic (PV) system is estimated at $13,000 to $20,000 by the California Energy Commission. A 2 KW system with 16% efficient PV modules requires a relatively large 160 square feet of open space for installation. In addition, such systems typically require the installation of one or more solar panels on top of a roof of a building structure, in an open space such as the front yard or the backyard of a building, or on the balcony, or the roof, of an apartment building. Qualified electricians are needed to modify the electrical service panel of a house or building so that the generated power can be used to supply household power consumption and/or to sell excess power back to the electric utility company.
The relatively high entry cost is a major barrier for many potential consumers of solar electric power systems. However, with rapidly increasing solar panel manufacturing capacity, the cost of solar electric power system is quickly decreasing. The efficiency of solar PV modules to convert light energy into electrical power is also improving. Solar power systems may provide primary or supplementary power to residential, building, or an enterprise level power grid. Some solar systems are being installed at power plants to supply electric power to the public utility power grid.
However, installing solar panels at residential homes, at business locations, or at power plants presents installation challenges. Modular solar panels that provide AC power and can be easily connected with one another may be desirable. The requirement to have qualified electricians to modify the electrical service panels also increases the cost for prospective customers of solar electric power systems.
In this and other contexts, a key factor that limits the adoption of solar electric power systems is the cost of solar system components with associated complexity in system connection, installation and supply of electrical power to the electrical system of a household, a utility grid, or a building. For a typical residential home or an office building, it is common to have limited open space for solar electric power system installation. To ensure wide adoption, a solar electric power system may need to be easily connected and installed. The system may also need to be easily connected to the electrical system of a household or building to supply electrical power, ideally without any modification to the existing electrical service panels.
The present invention provides apparatuses, methods, and systems directed to an integrated solar electric power generation system. Some embodiments of the present invention allow an integrated photovoltaic solar panel comprising one or more solar modules each capable of converting solar energy to DC electric power. The integrated solar panel further comprises one or more micro inverters which receive the DC power and convert it to AC power. The integrated solar panel provides connections that can be easily connected to other integrated solar panels. The output of the integrated solar panel may be connected to a wall outlet to supply electrical power. Other embodiments of the present invention can be used to connect multiple solar panels through an AC bus to which an AC load center is connected and provides power to application electrical power loads and/or a utility grid. Yet other embodiments of the present invention comprise one or more integrated solar panels that are connected through one or more local AC buses. The local AC buses are then connected through a main bus to an AC load center that provides power to application electrical power loads and/or a utility grid.
In one embodiment of the present invention, the apparatuses and methods are directed to an integrated solar power generation system which comprises one or more solar modules and one or more micro inverters. The solar modules comprise one or more solar cells that convert solar light energy to DC electrical power. The micro inverters monitor the converted electrical power and convert the DC power to AC power. In some embodiments, an integrated solar panel may comprise one or more sub-panels each comprising one or more solar modules and one or more micro inverters that produce AC power. The solar modules may be connected in parallel or in series to the micro inverter. One or more sub-panels may be easily connected through electrical wires.
In other embodiments of the present invention, the apparatuses, methods, and systems involve integrated solar electric power systems that may be connected to an indoor or outdoor wall outlet to supply the generated electrical power without modifying the electrical service panel. In some other embodiments of the present invention, one or more solar panels may be connected by an AC bus which is connected to an AC load center to provide power to application electrical power loads and/or a utility grid. In other embodiments, one or more solar panels may be connected by one or more local buses and the local buses are connected to a main AC bus which is connected to an AC load center to provide power to application electrical power loads and/or a utility grid.
The following detailed description together with the accompanying drawings will provide a better understanding of the nature and advantages of various embodiments of the present invention.
The following example embodiments and their aspects are described and illustrated in conjunction with apparatuses, methods, and systems which are meant to be illustrative examples, not limiting in scope.
As
Depending on the method of deployment, in some embodiments, a stand, a mounting bracket, or other mechanisms for securing the system may be needed. In other embodiments, the integrated solar panel may be mounted on a system that tracks the movement of the Sun to maximize sunlight exposure and increase the amount of power that can be generated.
In some embodiment, the integrated solar electric power generation system may be used as a household backup generator. Just like any household backup generator, once plugged into an existing electric socket, the entire house will have electricity provided by the system in parallel with the utility supply. In other embodiments, excess power may be sent back through the same circuitry that electrical power is sent to the house. Through the Sine Wave Generator included in the micro inverter of the integrated solar electric power system, as described below, the micro power input requirements of household appliances and power loads. The inverter design needs to comply with applicable regulatory codes. For example, there is the UL Standard 1703 on Inverters, Converters, and Controllers for Independent Power System. To be able to sell excess power generated back to the utility company, the output of the micro inverter needs to be conditioned so that it is also compatible with the electrical grid requirement. For example, in the U.S., the output of the inverter must conform to the IEEE Standard 929-2000, Recommended Practice for Utility Interface of Photovoltaic (PV) system.
Micro inverter 600 comprises four primary functional units: the DC power input isolation and on-off control unit 604, the Maximum Power Point Tracking unit 608, the DC-to-AC power transformation unit 610, and the Sine Wave Generator unit 612.
In one embodiment, the DC input Power Isolation and on-off control unit 604 comprises one or more inputs which come from the solar modules. Each string is isolated from others by the series diodes 604. This function also contains built-in electronic FET (Field Effect Transistor) switches 606 that are either closed to allow the passage of power or opened to deny the passage of power, depending on the status of the solar modules. In some embodiments, the input voltage from each string of solar modules ranges from 12-volt to 24.5-volt. The switch 606 is in the closed position when the voltage from the associated solar string is within this range. To protect the system from over-voltage or under-voltage, the switch 606 is in the opened position when the input voltage from its associated solar module string is outside the 12-volt to 24.5-volt range.
The Maximum Power Point Tracker (MPPT) unit 608 performs the summation of peak voltage and peak current from all strings into a single peak DC power output with the voltage fixed at 24 volt. The DC power output is sent to the transformer 610. When the voltage from any string of solar module goes below 12 volts or above 24.5 volts, MPPT 608 sends a signal to the associated switch 606 to disconnect that string. MPPT 608 also stops sending the DC power output to the transformer during utility blackout and upon receiving a cut-off command 620 from the Sine Wave Generator 612.
Transformer 610 is connected to the MPPT 608 output by one or more electrical wires. The MPPT 608 output is regulated at 24 volt DC. Transformer 610 performs the function of transforming received DC power to AC power. Transformer 610 comprises three output electrical wires—a ground electrical wire 614, a positive (“+”) electrical wire 616 and a negative (“−”) electrical wire 618. In some embodiments, transformer 610 may comprise a filter to smooth out the AC voltage. In other embodiments, a common household three prong extension cord may be used to connect the electrical wires 614, 616, and 618 to a wall outlet. One of the inlets of the three prong extension cord may be connected to the ground electrical wire 614 and the other two inlets may be connected to the positive (“+”) electrical wire 616 and the negative (“−”) electrical wire 618. The three prong plug of the extension cord may be plugged into the wall outlet to supply the AC electrical power generated by the integrated solar electric power generation system.
Sine Wave Generator 612 sends switching signals to the power switches of the primary winding of the transformer 610 to create AC power output. In some embodiments, a microprocessor or controller inside the Sine Wave Generator 612 stores the sine wave algorithm that enables the output of the inverter to track the grid voltage and to minimize output ripples on the power line. To meet the IEEE 929-2000 requirement for grid-tie inverters, the AC output voltage is sensed and rectified back to the Sine Wave Generator 612 in order to track, copy, and regulate the AC power output from the transformer 610. When utility blackout condition is sensed, the Sine Wave Generator sends a command 620 to the MPPT 608 to stop sending DC power output to the transformer 610.
The present invention has been explained with reference to specific embodiments. For example, while embodiments of the present invention have been described with reference to specific material, hardware and/or software components, those skilled in the art will appreciate that different combinations of material, hardware and/or software components may also be used. Other embodiments will be evident to those of ordinary skill in the art. It is therefore not intended that the present invention be limited, except as indicated by the appended claims.
