Patent Application
20120025750
The present invention relates generally to a photovoltaic solar power system and in particular to a portable photovoltaic solar power systems that can be plugged into a standard house outlet for feeding back into the electric grid and powering the electrical loads connected to the outlet circuit.
There is very little an individual can do to provide their own power. Wind-power incorporates huge windmills that cannot be placed in the great majority of homes and businesses. Other systems such as geothermal and wave technology are still not feasible for residential use. What is left is solar. The sun shines every day and provides huge amounts of power. However, except for installing a full solar array or just using low wattage units to provide energy for low-power electronic devices, there are hardly any products on the market that can make a serious dent in the average usage of electric power.
Current solar energy systems are expensive, must be installed by professionals and current solar panels are cumbersome and have limited efficiency. Though there are solar panels made in many different ways, there is none in the market that can be connected to any home electrical outlet and deliver sufficient current (500-1000 watts) that would serve to run the electric meter backwards. This would result in “banking” electricity for home and/or commercial use.
The present invention provides a portable solar power system, comprising a plurality of photovoltaic solar panels; storage batteries for storing energy generated by the photovoltaic solar panels; a charger operably connected to the photovoltaic solar panels for charging the storage batteries; a plurality of inverters operably connected to respective the photovoltaic solar panels for generating an AC output for connection to an outlet for feeding into an electric grid; and a switching circuit for automatically disconnecting the photovoltaic solar panels from the inverters and connecting the photovoltaic solar panels to the charger when power in the electric grid is down.
A solar power system 2 embodying the present invention is disclosed in
The housing 4 is preferably a truncated pyramid with a square base, a flat top and four sides. The pyramidal shape is advantageous in reducing shadow on the panels 6. The top portion 16 of the housing 4 provides an attachment base for a weatherproof box 18 for power outlets and switch, as will be described below. The panels 6 are preferably attached to the respective bottom portions 20 of the sides 14.
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The solar power system 2 can be connected to the grid through an outlet in the house or building and automatically disconnects itself when the grid is down. The system 2 can also operate as an off-grid, stand-alone power generator in remote areas where grid power is unavailable.
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The panels 6 available from Andalay Solar are each capable of producing up to 175 watts of DC power. The output voltage and current of the panels varies depending on the intensity of the incident solar radiation and the electrical load. The voltage typically ranges over a range of 25 to 39 volts. There is a point of maximum output power where the panels 6 should be operated in order to maximize their efficiency in converting solar energy to electrical energy. The inverters 54 are designed to operate the panels 6 at this maximum power point. The inverters 54 are commercially available, such as from Enphase Energy, 201 1st Street, Petaluma, Calif. 94952, www.enphaseenergy.com, Model No. M90-72-240-S11/2.
An AC to DC power supply 62 provides power to the relays 56 through the switch 50. The switch 50 has a grid tie position and an off tie position. When the switch 50 is in the grid tie position, power from the supply 62 will energize the relays 56 to connect the output of the panels 6 to the respective inverters 54, which in turn provide power to the connector 48, which is used to feed the generated power to the house loads through a standard wall outlet and to send any excess power to the electric grid through the house electric meter.
When the switch 50 is in the grid tie position, and if the power from the grid is ever lost, the inverters 54 will sense that condition and automatically shut-down their output to prevent “unintentional islanding,” a condition that happens when a utility grid is down, for maintenance as an example, and the distributed generation continues to feed the grid, which could have devastating consequences, as the power lines may still be energized without the knowledge of the utility, and consequently, the maintenance workers. When the outputs of the inverters 54 shut down, the input to the power supply 62 disappears, its output goes off and the relays 56 are no longer powered, thus causing them to reconnect the solar panel outputs to the charger 66 to charge the batteries 68. The energy from the solar panels 6 is thus always being captured either by the AC grid or the batteries 68. During the time that the electric grid is down, loads may be powered from the outlets 49 and 51.
When the switch 50 is in the off grid position, the relays 56 are de-energized to connect the output of the panels 6 to the battery charger 66, which is used to charge the batteries 68. Output from the batteries 68 is fed to an inverter 70 to provide an AC output through outlet 49. The output from the batteries 68 is also fed to the outlet 51 to provide a DC output. The DC power outlet 51 is similar to those found in automobiles for convenient connection of devices designed for use in that environment.
The battery charger 66 measures the amount of power going into the batteries 68 as well as the amount of power coming out of the batteries, thus allowing for the implementation of an indicator (not shown) showing the exact state of their charge. The charger 66 converts the high voltage from the solar panels 6 into the level required by the battery. The charger 66 constantly monitors the battery's state of charge and terminates charging when the battery becomes fully charged. The charger 66 monitors the current being extracted from the battery by the inverter 70 and the DC power outlet 51 Through this monitoring process, the charger 66 always knows the state of charge of the battery.
The inverter 70 differs from the inverters 54 in that it is not designed to be connected to the electric grid but to operate devices completely independent from it. The inverter 70 is commercially available, such as from Samlex America, 110-17 Fawcett Road, Coquitlam, BC, V3K 6V2 Canada, www.samlexamerica.com, Model No. PST-60s−12A.
It should be understood that the switch 50, the relays 56 and the power supply 65 constitute a switching circuit that provides the function of automatically switching the output of the panels 6 between the inverters 54 and the charger 66 depending on whether the electric grid is on or off. When the system 2 is connected to the electric grid through the outlet 48, and the switch 50 is in the grid tie position, the output of the panels 6 will be automatically disconnected from the inverters 54 and connected to the charger 66 when the electric grid goes down, thereby cutting off the power output to the grid. When power to the grid is restored, the output of the panels 6 is automatically switched to the inverters 54.
The switching circuit also provides the means for manually selectively switching the output of the panels 6 between the inverters 54 and the charger 66 through the mode switch 50. When the switch 50 is in the off grid position, the output of the panels 6 is always connected to the charger 66, regardless of whether there is power or not in the electric grid. Accordingly, when it is desired to operate the system 2 in the off grid mode, the switch 50 is opened to break the power to the relays 56, which causes the relays 56 to connect the panels 6 to the charger 66. When it is desired to operate the solar power system 2 in the grid tie mode, the switch 50 is closed to connect the power from the power supply 62 to the relays 56.
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The system 2 is designed to generate electricity from solar radiation and deliver it either to the AC power grid or use it to charge internal batteries that can then deliver power when solar radiation is not available, or when the electric grid is not available, such as in a remote area or when the grid is down for some reason.
Another embodiment of a solar power system 76 is disclosed in
The solar power system disclosed herein makes it possible for anyone to set up their own solar array capable of generating a daily minimum of about 4 kilowatt-hours of power for feeding back into the electric grid, thereby both running their electric meter backwards and “banking” electricity to be drawn on later or accomplishing a real time reduction of power usage from the grid. In addition, this onsite mini-power generation package would reduce the user's carbon footprint, lower the instances of blackouts and brownouts by adding generating capacity to the grid at peak usage periods. The device would further serve as an instant power source on locations throughout the world both for recreation and emergency use. The system 2 could be in storage and be immediately available for emergency.
The solar power system of the present invention could become a worldwide network of power generation as the use of plug-in electric vehicles become more popular and widespread. Tied to the electric grid, the system 2 could provide power at varied locations such as at fast food restaurants, hotels, rest stops and many other places along the highways. The solar power gathering function would add generating capacity to the grid.
The system 2 has several advantageous over an engine-generator. The system 2 advantageously generates clean, regulated power output. It has very long, efficient, run times at low power usage. It is completely quiet. It can be used indoors when fully charged and rolled outside to be charged.
While this invention has been described as having preferred design, it is understood that it is capable of further modification, uses and/or adaptations following in general the principle of the invention and including such departures from the present disclosure as come within known or customary practice in the art to which the invention pertains, and as may be applied to the essential features set forth, and fall within the scope of the invention or the limits of the appended claims.
