Abstract:
Highly efficient ventilation fans for exhausting air out from underneath roofs, and/or for being portable in use and application. The fan can include optimized airflow blades having a twisted configuration that can move at a rotational speed operation of up to approximately 500 rpm. The approximately 15 inch diameter twisted blades can be premolded on a hub that together form a single molded unit of plastic. They can also be fabricated using metal. The unit can be mounted in an exhaust outlet having a conical diffuser on or adjacent to a roof. Alternatively, the fan can be portable for use most anywhere there is a need for ventilation and moving of air. The blades can rotate by a solar powered motor, where the blades and motor can generate up to approximately 1040 cfm while using no more than approximately 16 Watts.

Description:
FIELD OF INVENTION 
   This invention relates to solar powered fans, and in particular to efficient attic exhaust fans and portable fans having optimized twisted nonmetal blades that are solar powered, and to methods of operating the novel fans. 
   BACKGROUND AND PRIOR ART 
   Ventilation fans for venting hot air from attic areas underneath roofs have been increasing in popularity over the years. Hot air is known to accumulate under roof tops especially in attic areas. This buildup of hot air can lead to poor cooling conditions within the building and increased utility costs to run air conditioning systems and cooling systems, and the like. Thus, it is desirable to improve and maximize air removal rates from under roofs and from attic spaces, and the like. 
   Existing attic ventilation fans have been used but have substantial power requirements from existing building electrical supplies. For example, the GRAINGER® catalog sells an automatic power attic gable ventilator model number 4YN78 having metal type blades that rotate at 1050 RPM (revolutions per minute) generating 1320 cfm (cubic feet per minute) and requires 200 Watts of power. Another GRAINGER® attic fan model 4YN77 generates a higher level of cfm (1620 cfm) but requires 225 Watts of power. 
   Most existing attic ventilation fans use standard stamped generally flat metal fan blades that have only fair air moving performance. Flat type blades are not designed to maximize moving of air. 
   Various attic type ventilation fans have been proposed over the years. See for example, U.S. Pat. Nos.: Des. 261,803 to Bohanon, Jr.; 4,501,194 to Brown; 5,078,047 to Wimberly; 6,306,030 to Wilson; and 6,695,692 to York. However, none of the cited references, individually or in combination overcome all the problems with the prior art described above. 
   The inventors and assignee of the subject invention have been at the forefront of inventing high efficiency ceiling fans by using novel twisted blade configurations. See for example, U.S. Pat. Nos: 6,884,034 and 6,659,721 and 6,039,541 to Parker et al. However, these fans are designed for maximizing air flow from ceiling fans that have much larger diameters (approximately 42 inches to 64 inches, etc.) and that operate at different speeds (less than approximately 200 RPM) than a small diameter ventilation fans that are needed to exhaust air from underneath roofs and from attic spaces. 
   Additionally, the inventors and assignee have worked on air conditioner condenser fans blades (see for example, U.S. Pat. Nos. D510,998 to Parker et al. and 7.014,423 to Parker et al. However, the air conditioner condenser fans are not optimized for the ventilation and removal of air from underneath roofs and from attic spaces. 
   Aircraft, marine and automobile engine propeller type blades have been altered over the years to shapes other than flat rectangular. See for example, U.S. Pat. Nos. 1,903,823 to Lougheed; 1,942,688 to Davis; 2,283,956 to Smith; 2,345,047 to Houghton; 2,450,440 to Mills; 4,197,057 to Hayashi; 4,325,675 to Gallot et al.; 4,411,598 to Okada; 4,416,434 to Thibert; 4,730,985 to Rothman et al. 4,794,633 to Hickey; 4,844,698 to Gornstein; 5,114,313 to Vorus; and 5,253,979 to Fradenburgh et al.; Australian Patent 19,987 to Eather. However, these patents are generally used for high speed water, aircraft, and automobile applications where the propellers are run at high revolutions per minute (rpm) generally in excess of 500 rpm. None of these propellers are designed for optimizing airflow to remove undesirable air from attics and from underneath roofs. 
   Portable fans such as handheld battery fans have been used over the years. Similar to the problems presented above, small portable fans do not have blades aerodynamically optimized for airflow. 
   In addition, portable fans have batteries that have limited lifespans since the batteries either need to be constantly recharged from a 120 volt power supply or the batteries need to be constantly replaced. 
   The need for efficient powered portable fans has been growing much more in recent years. Natural disasters such as hurricanes and earthquakes have caused extensive power outages that can last from several hours to weeks or more in the United States. Conventional battery powered fans, cannot be used effectively during these disaster conditions. The prior art listed above does not fix the problems with portable fan use. 
   Thus, the need exists for better performing fans over the prior art. 
   SUMMARY OF THE INVENTION 
   The first objective of the subject invention is to provide efficient roof/attic exhaust fans, blades, devices, apparatus and methods of operating the fans, that have optimized twisted nonmetal blades for maximizing removal of air from spaces underneath roofs. 
   The second objective of the subject invention is to provide efficient roof/attic exhaust fans, blades, devices, apparatus and methods of operating the fans, that can be solar powered. 
   The third objective of the subject invention is to provide efficient roof/attic exhaust fans, blades, devices, apparatus and methods of operating the fans, that can generate air flow up to at least approximately 30% above existing ventilation fans. 
   The fourth objective of the subject invention is to provide efficient roof/attic exhaust fans, blades, devices, apparatus and methods of operating the fans, that moves more air than existing ventilation fans and requires less power than existing ventilation fans. The invention reduces electrical power consumption and is more energy efficient over traditional flat planar ceiling fan blades. 
   The fifth objective of the subject invention is to provide efficient roof/attic exhaust fans, blades, devices, apparatus and methods of operating the fans, having fan blade aerodynamics optimized to maximize airflow in an approximately 15 inch diameter fan operating at up to approximately 500 (revolutions per minute) RPM. 
   The sixth objective of the subject invention is to provide efficient roof/attic exhaust fans, blades, devices, apparatus and methods of operating the fans, where the blades and hub are a single molded piece of plastic. 
   The seventh objective of the subject invention is to provide portable fans that can be used anywhere, and blades, devices, apparatus and methods of operating the fans, having optimized twisted nonmetal blades for maximizing air ventilation. 
   The eighth objective of the subject invention is to provide portable fans that can be used anywhere, and blades, devices, apparatus and methods of operating the fans, that can be solar powered. 
   The ninth objective of the subject invention is to provide portable fans that can be used anywhere, and blades, devices, apparatus and methods of operating the fans, that can generate air flow up to at least approximately 30% above existing portable fans. 
   The tenth objective of the subject invention is to provide portable fans that can be used anywhere, and blades, devices, apparatus and methods of operating the fans, that move more air than existing ventilation fans and requires less power than existing ventilation fans. The invention reduces electrical power consumption and is more energy efficient over traditional flat planar ceiling fan blades. 
   The eleventh objective of the subject invention is to provide portable fans that can be used anywhere, and blades, devices, apparatus and methods of operating the fans, having fan blade aerodynamics optimized to maximize airflow in an approximately 15 inch diameter fan operating at up to approximately 500 (revolutions per minute) RPM. 
   The twelfth objective of the subject invention is to provide portable fans, blades, devices, apparatus and methods of operating, the fans, that can be used anywhere such as during and after natural disasters such as hurricanes, earthquakes, and the like, as well as in environments having limited power supplies such as in construction sites, at picnics and other outings, on camping, hiking and fishing trips and at the beach. 
   A preferred embodiment can include a plurality of efficient optimized small diameter fan blades with a hub. Diameter sizes of the fans can include but not be limited to less than and up to approximately 15″, and greater. The blades can be made from plastic, and the like, and be pre-molded together with the hub. The blade dimensions and twist angles can be optimized to move air when running at approximately 500 rpm (revolutions per minute). 
   The solar powered fans can be used in attics and under roofs to ventilate and/or exhaust heated air therefrom. 
   Another embodiment has the solar powered fan being portable so that it can be used most anywhere there is a need for moving and circulating air. The fan can be moveable by a wheeled stand, and the solar powered panels can be movable by a hand truck, and the like. 
   Further objects and advantages of this invention will be apparent from the following detailed descriptions of the presently preferred embodiments which are illustrated schematically in the accompanying drawings. 

   
     BRIEF DESCRIPTION OF THE FIGURES 
       FIG. 1A  is a perspective view of the novel three twisted blades with hub that can be used with an attic fan. 
       FIG. 1B  is a bottom view of the blades with hub of  FIG. 1A . 
       FIG. 1C  is a side view of the blades and hub of  FIG. 1B  along arrow  1 CX. 
       FIG. 2A  is an upper top perspective view of a single twisted blade of  FIGS. 1A-1C . 
       FIG. 2B  is a top view of the single twisted blade of  FIG. 2A . 
       FIG. 2C  is a root end view of the single twisted blade of  FIG. 2B  along arrow  2 C. 
       FIG. 2D  is a top end view of the single twisted blade of  FIG. 2B  along arrow  2 D. 
       FIG. 2E  is a lower bottom perspective view of the twisted blade of  FIG. 2A . 
       FIG. 2F  is a bottom view of the twisted blade of  FIG. 2E . 
       FIG. 3  is a side perspective view of the twisted blade of  FIG. 2B  along arrow  3 X with labeled cross-sections A, B, C, D, E. 
       FIG. 4  is an end view of  FIG. 3  showing the different cross-sections A, B, C, D, and E. 
       FIG. 5A  shows the cross-section A of  FIGS. 3-4 . 
       FIG. 5B  shows the cross-section B of  FIGS. 3-4 . 
       FIG. 5C  shows the cross-section C of  FIGS. 3-4 . 
       FIG. 5D  shows the cross-section D of  FIGS. 3-4 . 
       FIG. 5E  shows the cross-section E of  FIGS. 3-4 . 
       FIG. 6  is a perspective exterior view of a roof alcove exhaust incorporating the fan and blades of the preceding figures with a solar power source. 
       FIG. 7  is a view of the separate components of  FIG. 6 . 
       FIG. 8  is another perspective exterior view of a roof top exhaust incorporating the fan and blades of the preceding figures with a solar power source. 
       FIG. 9  is a view of the separate components of  FIG. 8 . 
       FIG. 10  is a perspective front view of a portable fan incorporating the fan and blades of the preceding figures with a solar power source. 
       FIG. 11  is a rear view of the portable fan of  FIG. 10 . 
   

   DESCRIPTION OF THE PREFERRED EMBODIMENT 
   Before explaining the disclosed embodiments of the present invention in detail it is to be understood that the invention is not limited in its application to the details of the particular arrangement shown since the invention is capable of other embodiments. Also, the terminology used herein is for the purpose of description and not of limitation. 
   The labeled components will now be described. 
   
       
         1  hub and blade assembly 
         10  First blade 
         20  Second blade 
         30  Third blade 
         40  Hub 
         50  Motor 
         55  Power line 
         12  Root end of blade 
         18  Tip end of blade 
         14 LE leading edge of blade 
         16 TE trailing edge of blade 
         15  upper surface of blade 
         17  lower surface of blade 
         100  Solar power source 
         110 ,  120  PV (photovoltaic panels) 
         130  Solar panel frame 
         140  Optional stand 
         150  Optional Additional panels, frame and stand 
         200  Rood Alcove Exhaust 
         210  Roof 
         215  Opening in roof 
         220  Gable wall 
         225  Opening in gable wall 
         230  Hood 
         235  Louvers 
         240  housing 
         300  Roof Top Exhaust 
         330  Domed hood cover 
         335  Lower Opening about overhanging edges of Dome Cover 
         340  Housing under roof 
         350  Cylindrical Housing outside of roof 
         400  Portable Fan 
         410  Cylinder cover 
         420  pole 
         430  triangular base 
         440  wheels 
         450  Stand handle 
         460  fan speed control 
         470  Solar panels 
         475  cable/power line 
         480  handtruck 
         490  battery power source 
         495  cable/powerline 
     
  
     FIG. 1A  is a perspective view  1  of the novel three twisted blades  10 ,  20 ,  30  with hub  40  that can be used with an attic fan.  FIG. 1B  is a bottom view of the blades  10 - 30  with hub  40  of  FIG. 1A .  FIG. 1C  is a side view of the blades  10 - 30  and hub  40  of  FIG. 1B  along arrow  1 CX. 
     FIG. 2A  is an upper top perspective view of a single twisted blade  10  of  FIGS. 1A-1C .  FIG. 2B  is a top view of the single twisted blade  10  of  FIG. 2A .  FIG. 2C  is a root end view of the single twisted blade  10  of  FIG. 2B  along arrow  2 C.  FIG. 2D  is a tip end view of the single twisted blade  10  of  FIG. 2B  along arrow  2 D.  FIG. 2E  is a lower bottom perspective view of the twisted blade  10  of  FIG. 2A .  FIG. 2F  is a bottom view of the twisted blade  10  of  FIG. 2E . 
   Referring to  FIGS. 1-2F , the novel fan can have three twisted blades  10 ,  20 ,  30  each having a positive twist between their root ends adjacent to the hub  40  and their tip ends. The overall diameter of the fan  1  can be approximately 15 inches across the blade tip ends. The blades  10 ,  20 ,  30  and hub  40  can be formed into a single molded unit, such as being formed from injection molded plastic, and the like. 
   Referring to  FIGS. 2B-2D , the single twisted blade  10  can have a length of approximately 5.23 inches between the root end  12  and the tip end  18 . The twisted blade  10  can be attached to the hub  40  of  FIGS. 1A-1C  with the leading edge  14 LE of the root end  12  having an raised angle of approximately 47.03 degrees above horizontal plane HP with the trailing edge  16 TE of the root end  12  being below the horizontal plane HP. The tip end  18  of the blade  10  can have a twist from the root end so that the leading edge  14 LE is approximately 27.54 degrees above the horizontal plane HP with the trailing edge  16 TE below the horizontal plane HP. 
     FIG. 3  is a side perspective view of the blade of  FIG. 2B  along arrow  3 X with labeled cross-sections A, B, C, D, E in between the root end  12  and tip end  18 .  FIG. 4  is an end view of  FIG. 3  showing the different cross-sections A, B, C, D, and E, in curved views superimposed over one another showing the varying degrees of twist between the root end and tip end of the blade  10 . 
     FIG. 5A  shows the cross-section A of  FIGS. 3-4  having a leading edge  14 LE slightly curved down being approximately 41.06 degrees above the horizontal plane HP. Cross-section A has a convex shaped upper surface  15  and a lower surface  17  with a concave bend configuration, and trailing edge  16 TE below the horizontal plane HP. The leading edge  14 LE having a more blunt rounded edge than the trailing edge  16 TE. Cross-section A can have a width of approximately 3.78 inches between the trailing edge  16 TE and leading edge  14 LE. The thickness of the cross-section A can expand from the trailing edge  16 TE to being approximately 0.09 inches half way to a midpoint of the cross-section which has a thickness of approximately 0.14 inches, and the thickness halfway between the midpoint and the leading edge  14 LE being approximately 0.18 inches. 
     FIG. 5B  shows the cross-section B of  FIGS. 3-4  having a leading edge  14 LE slightly curved down being approximately 35.93 degrees above the horizontal plane HP. Cross-section B has a convex shaped upper surface  15  and a lower surface  17  with a concave bend configuration, and trailing edge  16 TE below the horizontal plane HP. The leading edge  14 LE having a more blunt rounded edge than the trailing edge  16 TE. Cross-section B can have a width of approximately 3.81 inches between the trailing edge  16 TE and leading edge  14 LE. The thickness of the cross-section B can expand from the trailing edge  16 TE to being approximately 0.09 inches half way to a midpoint of the cross-section which has a thickness of approximately 0.14 inches, and the thickness halfway between the midpoint and the leading edge  14 LE being approximately 0.18 inches. 
     FIG. 5C  shows the cross-section C of  FIGS. 3-4  having a leading edge  14 LE slightly curved down being approximately 32.69 degrees above the horizontal plane HP. Cross-section C has a convex shaped upper surface  15  and a lower surface  17  with a concave bend configuration, and trailing edge  16 TE below the horizontal plane HP. The leading edge  14 LE having a more blunt rounded edge than the trailing edge  16 TE. Cross-section C can have a width of approximately 3.91 inches between the trailing edge  16 TE and leading edge  14 LE. The thickness of the cross-section C can expand from the trailing edge  16 TE to being approximately 0.08 inches half way to a midpoint of the cross-section which has a thickness of approximately 0.13 inches, and the thickness halfway between the midpoint and the leading edge  14 LE being approximately 0.18 inches. 
     FIG. 5D  shows the cross-section D of  FIGS. 3-4  having a leading edge  14 LE slightly curved down being approximately 30.26 degrees above the horizontal plane HP. Cross-section D has a convex shaped upper surface  15  and a lower surface  17  with a concave bend configuration, and trailing edge  16 TE below the horizontal plane HP. The leading edge  14 LE having a more blunt rounded edge than the trailing edge  16 TE. Cross-section D can have a width of approximately 4.0 inches between the trailing edge  16 TE and leading edge  14 LE. The thickness of the cross-section D can expand from the trailing edge  16 TE to being approximately 0.09 inches half way to a midpoint of the cross-section which has a thickness of approximately 0.14 inches, and the thickness halfway between the midpoint and the leading edge  14 LE being approximately 0.18 inches. 
     FIG. 5E  shows the cross-section E of  FIGS. 3-4  having a leading edge  14 LE slightly curved down being approximately 28.56 degrees above the horizontal plane HP. Cross-section E has a convex shaped upper surface  15  and a lower surface  17  with a concave bend configuration, and trailing edge  16 TE below the horizontal plane HP. The leading edge  14 LE having a more blunt rounded edge than the trailing edge  16 TE. Cross-section E can have a width of approximately 4.09 inches between the trailing edge  16 TE and leading edge  14 LE. The thickness of the cross-section E can expand from the trailing edge  16 TE to being approximately 0.09 inches half way to a midpoint of the cross-section which has a thickness of approximately 0.14 inches, and the thickness halfway between the midpoint and the leading edge  14 LE being approximately 0.19 inches. 
   Roof Alcove Exhaust 
     FIG. 6  is a perspective exterior view of a roof alcove exhaust embodiment  200  incorporating the fan  1  and blades  10 ,  20 ,  30  of the preceding figures with a solar power source  100 .  FIG. 7  is a view of the separate components of  FIG. 6 . 
   Referring to  FIGS. 6-7 , the novel fan  1  can be mounted with blades  10 - 30  facing to exhaust sideways in a housing  240  inside of an opening  225  in a gable side wall  220  below a roof  210 . The outer hood  230  with covers  235  can cover the opening  225  in the gable side wall  220 . The fan motor  50  can draw power through cable/power line  55  from a rooftop mounted solar power source  100 , which can include two PV (photovoltaic) panels  110 ,  120  in a frame  130  that can be directly attached (by screws, and the like) into the roof  210 . An optional stand  140  can be used to elevate the solar panels  110 ,  120  and frame  130  above the roof  210 . Additional power can be provided by another solar power source  150 . 
   Roof Top Exhaust 
     FIG. 8  is another perspective exterior view of a roof top exhaust  300  incorporating the fan  1  and blades  10 ,  20 ,  30  of the preceding figures with a solar power source  100 .  FIG. 9  is a view of the separate components of  FIG. 8 . 
   Referring to  FIGS. 8-9 , the novel fan  1  can be mounted with blades  10 - 30  facing to upward in a housing  340  underneath an opening  215  in roof  210 . The domed hood cover  330  can overhand a cylindrical housing  350  outside roof  210  having side edges which overhang the housing  350  with an exhaust opening  335  thereunder. Similar to  FIGS. 6-7 , the fan motor  50  can draw power through cable/power line  55  from a rooftop mounted solar power source  100 , which can include two PV (photovoltaic) panels  110 ,  120  in a frame  130  that can be directly attached (by screws, and the like) into the roof  210 . An optional stand  140  can be used to elevate the solar panels  110 ,  120  and frame  130  above the roof  210 . Additional power can be provided by another solar source  150 . 
   Testing of the solar powered fan will now be described. A single 10 W panel with an open circuit voltage of approximately 14 to approximately 15 vdc (volts direct current) was connected to the fan  1  previously described having twisted blades  10 ,  20 ,  30 . 
   A conventional fan was compared to the novel fan  1  of the invention with the results shown in Table 1. The conventional fan tested was a KING OF FNS® Solar Gable Ventilation Fan (22-607-690) using a Brushless DC motor: BOM-ZYW 92/22A-03). The conventional fan used a 15 inch metal blade operating at 7.3 vdc (Volts DC current)@835 mA (milliamps). 
   The novel improved fan and diffuser used novel twisted blades and a diffuser housing (described more fully below) and used the same DC motor as that of the conventional fan and operated at 7.6 vdc@915 mA. 
   The conventional fan got about 6.0 Watts of useful power (VmA) out of the standard solar powered panel while the novel fan  1  had approximately 7.0 Watts which would show a better match of load to IV curve for PV panel. The IV curve is the relationship of the current versus voltage characteristics of a photovoltaic cell, module, or array. 
   The test results simulated those likely seen with two PV (photovoltaic) panels under partly sunny conditions (approximately 11.2 Volts, approximately 1.4 amps). 
   Tests of the two attic fans were conducted and the results are shown in Table 1. One test was with standard metal blades and a cylindrical housing and the second test used the novel twisted blades  10 ,  20 ,  30  and a conical diffuser housing for pressure recovery. 
   The inventors tested both models as if they were being run by two PV panels wired parallel: 11.2 Volts DC with approximately 1.4 amp current (approximately 15.7 Watts). A calibrated flow plenum was used for the testing. 
   
     
       
             
             
           
             
             
             
             
           
             
             
             
             
           
         
             
                 
               TABLE 1 
             
           
           
             
                 
                 
             
             
                 
               Fan Type 
             
           
        
         
             
                 
               ConventionalAttic 
               Grainger 
               Novel Efficient 
             
             
                 
               Fan (KF-Fan) 
               Fan 
               Fan 
             
             
                 
                 
             
           
        
         
             
               Total CFM 
               802 
               1320 
               1043 
             
             
               Total Watts 
               22.0 
               200 
               22.0 
             
             
               Total CFM/Watts 
               36.4 
               6.6 
               47.4 
             
             
                 
             
           
        
       
     
   
   Table 1 further compared the GRAINGER® fan (another fan) as well. Unlike the conventional fan and the novel fan, the GRAINGER® fan used a standard AC shaded pole motor instead of being solar powered. 
   The standard conventional fan (KofF0) and housing was found to move approximately 802 cfm (cubic feet per minute) at approximately 0.0 external static pressure. The improved fan  1  with the conical diffuser housing moved approximately 1043 cfm at zero static pressure. The novel fan also operated at a lower RPM (revolutions per minute) and was observed to be more quiet than the conventional fan. 
   The test results represented an approximately 30% increase in flow at the same power. Given that shaft power is increasing between the square and the cube of the air mass flow, this presents about an approximately 90% increase in the work being accomplished. 
   The GRAINGER® catalogue shows that comparable AC attic vent fans provide about 1320 cfm@200 Watts of AC power. The GRAINGER® attic vent fan retails for about $50, but that doesn&#39;t include the cost for an electrician to wire them up. Assuming that the AC attic fans might be operating 10 hours per day, the solar fans would be saving about $6 a month compared to a conventional AC powered one. 
   The prototype diffuser used with the novel fan had the following dimensions: Narrow point in diffuser throat: 15.5 inches; Fan diameter: approximately 15 inches; Tip clearance: approximately 0.25 inches; Overall height of diffuser: approximately 13.75 inches (can shorten to about 12.75 inches with lip to inlet bell); Exhaust diameter: approximately 17.25 inches; and Inlet diameter: approximately 16.0 inches. The region in the diffuser where the fan sweeps (about 4 inches in height as indicated by the hub) should be the narrowest section (approximately 15.5 inches). Above that the diffuser smoothly increases in diameter to 17.25 inches. The diffusers has an optimal angle of divergence of 7-10 degrees. 
   In summary, the novel fan  1  can generate airflow of at least approximately 900 cfm (cubic feet per minute) from the rotating blades while running the fan with the twisted blades and the motor at an efficiency of at least approximately 60 CFM per watt. The blades can be rotated up to approximately 500 RPM while generating an airflow of at least approximately 1000 cfm and up to at least approximately 1040 cfm or more. 
   Portable Fan 
     FIG. 10  is a perspective front view of a portable fan  400  incorporating the fan  1  and blades  10 ,  20 ,  30  of the preceding figures with a solar power source  470 .  FIG. 11  is a rear view of the portable fan  400  of  FIG. 10 . The portable fan embodiment  400  combines a high efficiency fan  1  in a cylindrical housing  410  with a portable stand that can consist of a telescopingly height adjustable pole  420  with triangular shaped base  430  having wheels  440 . The triangularly shaped base  430  can have a rear generally straight edge  432  with wheels  440  mounted at each end, angled sides  434 ,  436  meeting at a rounded apex  438 . The shape of the base  430  allows the fan  400  to be easily tilted back in the direction of arrow B so that a user can move the fan  400  with only two wheels  440  by gripping the handle  450  that is attached to the upper pole  420  of the portable fan  400 . 
   A handtruck type stand  480  having an L-shape with wheels  485  on the lower end and hand rails  482  can support solar power panels (PV array)  470 , with a battery  490  on the lower ledge  488 . The battery power supply  490  can be connected by a power cable  475  to the photovoltaic (PV array)  470  where it becomes a PV powered charger that can be connected by another cable  495  to controls  460  to supply power to the fan  1  on the fan stand  420 . The fan  400  can be moved for portable cooling anywhere outdoors where the cable line  495  can be extended up to approximately 50 feet or more in length, from the PV powered charger. Similar to the preceding embodiments, the fan  1  and blades  10 ,  20 ,  30  can have optimized twist and airfoil as previously described to improve air moving performance. 
   The outdoor portable fan  400  can also use a high-efficiency brush-less DC motor  500  instead of the previously described motor  50  and can be hooked to a 30 Watt PV panel  470  charging two sealed lead acid 17.2 amp-hr gel cells in the battery  490 . As previously described, a power cord  495  can allow the fan  400  to be located up to approximately 50 feet or more from the solar powered panels (PV)  470 . Although the fan can be used outdoors, the cord  495  allows the fan  400  to be able to be used indoors with the PV panels located outdoors. 
   Fan speed of the DC motor  500  or the basic motor  50  can be modulated with a knob altered pulse width modulated (PWM) or resistance based control  460  to accordingly adjust speeds. 
   With the invention using the more efficient fan it is possible to move more air than conventional portable fans. It is possible to run the fan longer on a limited battery pack or to use smaller and less expensive PV panels with the invention. 
   The novel portable fan can be operated where no electric power is available, such as in remote locations or with disaster relief (post hurricane/post earthquake environments). The portable fan can have use in construction sites, at picnics and other outings, on camping, hiking and fishing trips at the beach, and can be used both during the day and at night. 
   At full speed, the fan  400  can draw approximately 1.4 amps at approximately 11 volts (approximately 15 Watts). At half speed, the fan  400  can draw approximately 5 Watts. With its 34 amp per hour backup, the fan can operate for approximately 11 hours with an approximate 50% discharge with no sun. The fan  400  can use the plastic molded blades previously described and as a result can be more efficient than metal blades. 
   With an average of approximately 6 hours of sun per day, the portable fan  400  can potentially provide a continuous eight hours of daily operation at full speed, and a continuous 24 hours of operation at half speed. 
   While the preferred embodiments describe the fan as having plastic blades and a plastic hub molded into a single unit, the invention can have separate blades attached to a separate hub. 
   While the blades are described as preferably being made from plastic, the blades can be made from metal such as but not limited to aluminum, galvanized metal, steel, and the like. 
   Although the preferred embodiments show the fan with three twisted blades, the invention can apply to fans having two blades, four blades or more. 
   While the invention has been described, disclosed, illustrated and shown in various terms of certain embodiments or modifications which it has presumed in practice, the scope of the invention is not intended to be, nor should it be deemed to be, limited thereby and such other modifications or embodiments as may be suggested by the teachings herein are particularly reserved especially as they fall within the breadth and scope of the claims here appended.