Abstract:
A dual-powered airflow generator comprising: a primary fan motor powered from a primary power source and an auxiliary fan motor powered from a secondary power source. In one embodiment, the primary fan motor has a first drive shaft wherein operation of the primary fan motor causes a desired airflow at a design power of the primary power source. In a preferred embodiment, the auxiliary fan motor is powered from a secondary power source and has a second drive shaft mechanically coupled to the primary fan motor, wherein the auxiliary fan motor is configured to assist the primary fan motor in causing the desired airflow while the primary fan motor operates from the primary power source at a reduced power. In a preferred embodiment, the auxiliary fan motor is powered by a solar power generating device or other alternative energy source.

Description:
TECHNICAL FIELD OF THE INVENTION 
     The present invention is directed, in general, to an airflow generator and, more specifically, to a dual powered airflow generator for use with a heat pump, air handler, etc. 
     BACKGROUND OF THE INVENTION 
     Secondary sources of electrical power to supplement commercial line voltage have been of interest for several decades. Among the most successful of secondary sources has been solar power. Solar power has been used successfully in many applications. Of course, the success of such applications depend upon: (1) the availability of solar radiation when needed, (2) the ability to store power generated by solar radiation until the power is needed and solar radiation is unavailable, and (3) the ability to integrate solar-generated power with conventional power without degrading overall system performance. 
     In the field of air conditioning, solar power has been used to operate: (a) a boiler/condenser heat engine, (b) a reciprocating piston heat engine, (c) a motor to operate a compressor and a second motor to operate a condenser fan, and (d) to power a heat pump. However, these applications generally rely on solar energy to power the designed function without simultaneous reliance on another primary power source, such as commercial line AC or DC electricity. When solar energy is not available, the systems generally revert to operating solely on the available primary power source. 
     Accordingly, what is needed in the art is an airflow generator for an air conditioning/heat pump system that allows simultaneous integration of a secondary power source along with a primary power source without the need for complex electronics to integrate the two sources of power. 
     SUMMARY OF THE INVENTION 
     To address the above-discussed deficiencies of the prior art, the present invention provides a dual-powered airflow generator comprising: a primary fan motor powered from a primary power source and an auxiliary fan motor powered from a secondary power source. In one embodiment, the primary fan motor has a first drive shaft wherein operation of the primary fan motor causes a desired airflow at a design power of the primary power source. In a preferred embodiment, the auxiliary fan motor is powered from a secondary power source and has a second drive shaft mechanically coupled to the primary fan motor, wherein the auxiliary fan motor is configured to assist the primary fan motor in causing the desired airflow while the primary fan motor operates from the primary power source at a reduced power. In a preferred embodiment, the auxiliary fan motor is powered by a solar power generating device or other alternative energy source. 
     The foregoing has outlined preferred and alternative features of the present invention so that those skilled in the art may better understand the detailed description of the invention that follows. Additional features of the invention will be described hereinafter that form the subject of the claims of the invention. Those skilled in the art should appreciate that they can readily use the disclosed conception and specific embodiment as a basis for designing or modifying other structures for carrying out the same purposes of the present invention. Those skilled in the art should also realize that such equivalent constructions do not depart from the spirit and scope of the invention. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       For a more complete understanding of the present invention, reference is now made to the following descriptions taken in conjunction with the accompanying drawings, in which: 
         FIG. 1  illustrates one embodiment of a dual-powered airflow generator constructed according to the principles of the present invention; 
         FIG. 2  illustrates an alternative embodiment of a dual-powered airflow generator constructed according to the principles of the present invention; 
         FIG. 3  illustrates a graph of power in watts drawn by an AC fan motor prototype while operating simultaneously with a simulated DC photovoltaic power system powering the auxiliary fan motor; 
         FIG. 4A  illustrates a block diagram of a generalized heat pump system employing first and second dual-powered airflow generators in the heating mode; and 
         FIG. 4B  illustrates the heat pump system of  FIG. 4A  in the cooling mode. 
     
    
    
     DETAILED DESCRIPTION 
     Referring initially to  FIG. 1 , illustrated is one embodiment of a dual-powered airflow generator  100  constructed according to the principles of the present invention. The dual-powered airflow generator  100  comprises a primary fan motor  110 , an auxiliary fan motor  120 , a fan  130 , and a shaft coupler  140 . In a preferred embodiment, the primary fan motor  110  comprises a variable-speed AC motor having a first drive shaft  113  and a microcontroller  115 . The fan  130  is mechanically coupled to the first drive shaft  113  through second drive shaft  123  and shaft coupler  140 . A variety of different fan motors may be used with the dual-powered airflow generator  100 . For example, the most common fractional-horsepower motor type used in airflow generators, i.e., air conditioning systems, air handlers, etc., is the permanent-split capacitor (PSC) induction motor. However, this motor does not reduce its power consumption linearly with an auxiliary fan motor output, so it is not the best choice for this application intended to conserve primary electrical energy. The best motor type currently available is an electronically-commutated, brushless permanent magnet motor (ECM-BPM). Several manufacturers produce such a product, as: General Electric by Regal-Beloit (USA), EBM-Papst (Germany) and Delta Products (Taiwan). These ECM-BPM motors are AC-powered, variable speed electric motors wherein the microcontroller  115  will maintain a selected speed of the fan  130  by adjusting input AC power as needed. 
     In a preferred embodiment, the auxiliary fan motor  120  is a brushless permanent magnet DC motor having a second drive shaft  123  and powered by an auxiliary power system  150 . The second drive shaft  123  is mechanically coupled to the first drive shaft  113  with the shaft coupler  140 . In one embodiment, the shaft coupler  140  may be a rigid shaft coupler  140 . Alternatively, the shaft coupler  140  may be a flexible shaft coupler  140 . One who is of skill in the art is familiar with rigid mechanical shaft couplers and flexible mechanical shaft couplers. 
     In one embodiment, the auxiliary power system  150  is a solar-power generating system, e.g., a solar array in the form of a photovoltaic panel  152 , etc. When exposed to sunlight, the photovoltaic panel  152  comprising a plurality of photovoltaic cells  155  generates DC electric power that may be used to power the auxiliary fan motor  120 . One who is of skill in the art is familiar with photovoltaic cells and how they generate DC electrical power from sunlight. Of course, sunlight is not always of a constant level of intensity, e.g., a partly cloudy day may have periods of direct unimpeded sunlight falling upon the photovoltaic panel, thereby generating peak power. That peak power will turn the auxiliary fan motor  120  at the maximum rpm consistent with the capability of the auxiliary fan motor  120 . However, during a partly cloudy day, episodic appearance of cloud layers will likely appear in the sky, thereby temporarily obstructing part or all of the sunlight directed at the particular location of the photovoltaic panel  152 . During these partial or total obstructions of sunlight, the power output of the photovoltaic panel  152  will decrease in accordance with the available sunlight at the surface of the photovoltaic panel  152 . Therefore, the torque to turn the second drive shaft  123  will vary with the available sunlight. Furthermore, the intensity of the sunlight impinging upon the photovoltaic panel  152  will vary as the angle of the sun&#39;s rays falling upon a particular geographical location changes with the seasons. Therefore, the available solar power will vary considerably from day to day, or week to week. This is significant when the airflow generator  100  is part of a heat pump system and therefore operational throughout the year. While the present discussion has centered on a solar-powered auxiliary power system, other power systems, e.g., wind power, battery, rectified DC, etc., may also be used; independently or together with the solar-powered auxiliary power system. As the available solar power varies, the microcontroller  115  will sense the first drive shaft speed which is being spun at the same rate as the second drive shaft because of the mechanical coupling, and the microcontroller will apply or reduce power to the primary fan motor  110  so as to maintain a set rpm of the fan  130 . Thus, even when the photovoltaic panel  152  is partially obscured by clouds or other obstructions, a battery or other electrical energy storage device may provide secondary power to the auxiliary motor. 
     Referring now to  FIG. 2 , illustrated is an alternative embodiment of a dual-powered airflow generator  200  constructed according to the principles of the present invention. The dual-powered airflow generator  200  comprises a primary fan motor  210 , an auxiliary fan motor  220 , a fan  230 , a shaft coupler  240 , and a heat exchanger  250 . An auxiliary power system  260  comprising a photovoltaic panel  262  of a plurality of photovoltaic cells  265  is coupled to the auxiliary fan motor  220 . In a preferred embodiment, the primary fan motor  210  comprises a variable-speed AC motor having a first drive shaft  213  and a microcontroller  215 . The fan  230  is mechanically coupled to the first drive shaft  213 . In a preferred embodiment, the primary fan motor  210  is a General Electric® Model #142 motor or similar, as above. The fan  230  directs a set airflow across, through or over the heat exchanger  250 . 
     The auxiliary fan motor  220  is a brushless permanent magnet DC motor having a second drive shaft  223  and powered by the auxiliary power system  260 . The second drive shaft  223  is mechanically coupled to the first drive shaft  213  with the shaft coupler  240 . In an alternative embodiment, the shaft coupler  240  may be an overrunning clutch  240 . The overrunning clutch  240  allows the second drive shaft  123  to idle when there is inadequate power from the auxiliary power system  260 . The AC fan motor  210  provides torque to turn the fan  230  at a set speed under the control of the microcontroller  215 . As increasing power is available from the auxiliary power system  260 , primary AC power applied to the primary fan motor  210  is decreased and the fan speed maintained. Of course, alternative sources of electricity, e.g., wind generators, etc., may be employed in place of or to supplement the auxiliary power system  260 . 
     Referring now to  FIG. 3  with continuing reference to  FIG. 2 , illustrated is a graph of power in watts drawn by an AC fan motor  210  prototype while operating simultaneously with a simulated DC photovoltaic power system powering the auxiliary fan motor  220 . As can be seen, with the DC auxiliary fan motor  220  operating between 140 minutes and 146 minutes elapsed time, the power required by the AC primary fan motor  210  to maintain a constant speed of the fan  230  drops from about 117 watts to about 5 watts when the auxiliary fan motor  220  is operating. 
     Referring now to  FIG. 4A , illustrated is a block diagram of a generalized heat pump system  400  employing first and second dual-powered airflow generators  411 ,  412  constructed according to the principles of the present invention. The heat pump system  400  comprises: first and second dual-powered airflow generators  411 ,  412 ; an outside coil  426 , an inside coil  427  and a four-way reversing valve  428 . One who is of skill in the art is familiar with the layout and operation of a heat pump system. 
     In the illustrated form of  FIG. 4A , the outside coil  426  is functioning as an evaporator and the inside coil  427  is functioning as a condenser. In contrast,  FIG. 4B  illustrates the heat pump of  FIG. 4A  in the cooling mode. The outside coil  426  is functioning as a condenser and the inside coil  427  is functioning as an evaporator. Four-way valve  428  enables the heat pump system  400  to change from heating to cooling an interior workspace. Regardless of the heating/cooling configuration of the heat pump system  400 , the first and second dual-powered airflow generators  411 ,  412  cause airflow across, over or through their respective heat exchangers  426 ,  427 . Both the first and second dual-powered airflow generators  411 ,  412  employ conventional AC line voltage to primarily power their respective fans and an auxiliary power to power their respective auxiliary motors. Of course, backup power systems such as batteries, etc., may also be included in the system to provide supplemental power when solar power is unavailable. 
     Thus, a DC auxiliary fan motor system for a condenser fan unit cooperating with a AC primary fan motor through a mechanical coupling of the respective motor drive shafts has been described. In a preferred embodiment, the DC auxiliary fan motor system is powered by a photovoltaic solar power generator. The power required by the AC primary fan motor to maintain a set fan speed in conjunction with the auxiliary fan motor is controlled by a microcontroller incorporated in the AC primary fan motor. 
     Although the present invention has been described in detail, those skilled in the art should understand that they can make various changes, substitutions and alterations herein without departing from the spirit and scope of the invention in its broadest form.