Patent Publication Number: US-2012025750-A1

Title: Portable Solar Power System

Description:
FIELD OF THE INVENTION 
     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. 
     BACKGROUND OF THE INVENTION 
     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. 
     SUMMARY OF THE INVENTION 
     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. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is a perspective view of an embodiment of a solar power system embodying the present invention. 
         FIG. 2  is a perspective view of a removable hinge used in the embodiment of  FIG. 1 . 
         FIG. 3  is a perspective view of the embodiment of  FIG. 1 , showing one panel in the upright position for stowage. 
         FIG. 4  is a perspective view of a bracket used to hold the panel in  FIG. 3  in the upright position in cooperation with a removable member. 
         FIG. 5  is a perspective view of a bracket used to removably attach a member to support the panel of  FIG. 3  in the upright position. 
         FIG. 6  is perspective view of a weatherproof electrical box containing a number of power outlets and a mode switch. 
         FIG. 7  is a schematic wiring diagram of the system of  FIG. 1 . 
         FIG. 8  is a perspective view of another embodiment of the system of  FIG. 1 . 
     
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
     A solar power system  2  embodying the present invention is disclosed in  FIG. 1 . The system  2  includes a housing  4  and photovoltaic solar panels  6  hingedly and removably attached to the housing  2 . A plurality of wheels  8  are disposed on the underside of the housing  2  to provide mobility and portability. Each panel  6  is also provided with a wheel  10  to provide support to the outer end  12  of the panel  6  when it is deployed in the horizontal position to directly expose the photovoltaic surfaces to the solar radiation. The wheels  8  and  10  allow the entire system  2  to be moved around with ease. Although the panels  6  are disclosed as rectangular, the shapes and sizes of the panels can vary depending on the need and the existing technology. The panels  6  are readily available from several sources, such as Andalay Solar, Inc., www.andalaysolar.com, Model No. ST175-1, which are 175 W each. 
     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 . 
     Referring to  FIG. 2 , hinges  22  are used to attach the near ends  24  of the panels  6  to the respective sides  14  of the housing  4 . A removable pin  26 , secured by a removable cotter pin  28 , advantageously allows the removable of the panel  6  for maintenance or replacement. 
     Referring to  FIG. 3 , the panels  6  may be raised in the upright position for stowage or relocation. A tubular member  30  has one end removably attached to an upper portion of an opposite side  14  and another end removably attached to the outer end  12  of the panel  6  to support the panel  6  in the upright position. The member  30  functions as a brace, supporting the panels  6  in the upright position during stowage or when moving to a different location. The member  30  is preferably plastic or lightweight metal. It should be understood that in the stowage position, each panel  6  is supported in the upright position by its respective tubular member  30 . 
     Referring to  FIG. 4 , a bracket  32  is attached to the outer end  12  of each panel  6 . The bracket  32  includes a projecting member  34  that is received within the end portion  35  of the tubular member  30  through a slot  36 . A removable pin  38  threaded through aligned holes in the wall of the tubular member  30  and the projecting member  34  secures the panel  6  to the tubular member  30 . The opposite end portion  37  of the tubular member  30  is removably attached to the opposite side  14  with a bracket  40  including a projecting member  42  receivable within the tubular member  30 . A removable pin  44  threaded through aligned holes in the wall of the tubular member  30  and the projecting member  42  secures the opposite end portion  37  of the tubular member  30  to the housing  4 . Placing the end portion  37  of the tubular member  30  a further distance from the panel  6  by locating the end portion  37  at the opposite side of the housing  4  advantageously provides a more rigid stowage configuration. Each panel  6  is provided with the bracket  32  and each side  14  with the bracket  40 . 
     Referring to  FIG. 6 , the box  18  includes a cover  46  to provide access to power outlets  48 ,  47 ,  49  and  51  and a mode switch  50 . The cover  46  protects the components from the weather. The outlet  48  is for connection to a house outlet for feeding the generated power to the house loads connected to the house outlet circuit and any excess to the electric grid through the house meter, thereby running the meter backwards for crediting to the customer&#39;s account with the utility company. A suitable cord would be used to connect the outlet  48  to an AC outlet in the house or building. Another outlet  47  is used for connecting another system  2  in daisy chain manner to increase the output of the system  2 , if desired. Still another outlet  51  provides a DC output. Another outlet  49  is used for providing AC power when there the grid is down. A plug  52  removably connects each panel  6  to the electrical components inside the housing  4 . 
     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. 
     Referring to  FIG. 7 , each solar panel  6  is connected to a respective inverter  54  via a respective relay  56 . Each inverter  54  converts the DC output of each panel  6  to 240 VAC. A transformer  58  lowers the voltage to 120 VAC for residential usage. The inverters  54  automatically sense the presence of the grid tie power signal and synchronize themselves to it. Power is then converted from the DC form obtained from the solar panels into the properly synchronized AC form for connection to the grid. The outlet  48  is used to connect the output of the transformer  58  to a residential power outlet, such as a wall outlet (not shown) to power the house loads connected to the outlet circuit. Any generated excess power is advantageously fed back into the electric grid through the house meter for crediting to the customer&#39;s account with the utility company. 
     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&#39;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 −12 A. 
     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 . 
     Referring back to  FIG. 3 , the various electrical components disposed within the housing  4  are visible after one side  14  has been temporarily removed. Some of the components shown are the inverters  54  and  66 , the transformer  58  and the batteries  68 . 
     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  FIG. 8 . The system  76  is the same as the system  2 , except that the outer surfaces of the sides  14  of the housing  4  are covered with photovoltaic solar panels  78 . The panels are operably connected together to increase the power output of the system  2 . 
     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&#39;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.