Abstract:
The invention includes an apparatus, system, and method for the drying of particulate agricultural matter, especially particulate crops, such grains. The present invention provides a crop particulate (i.e., grain) drying system utilizing solar energy to heat a heat transfer fluid or solution within concomitant forced-air and radiant heat systems which pass heated air through a crop particulate material contained within a conventional crop silo or bin. Electricity demand may be met through utilization of solar photovoltaic panels backed up by connection to an external power source (i.e. power utility).

Description:
RELATED APPLICATION DATA 
     Not Applicable. 
     TECHNICAL FIELD  
     The present invention relates generally to grain drying systems and methods of grain drying structure utilizing solar energy. 
     BACKGROUND OF THE INVENTION 
     The present invention relates generally to grain drying structures and more particularly to grain drying structures and systems utilizing solar energy. 
     It is desirable to be able to dry grain efficiently and relatively quickly, rather than rely upon drying in the fields which often achieves varied and unpredictable results, and carries with it the risks of adverse weather conditions that may cause rot or keep the farmer from harvesting the grain as desired. 
     Typically, grain may be dried in silos using typical ventilation and drying arrangements with propane used to heat the drying air flow that is circulated through the grain, often accompanied by agitation. However, propane is very expensive and often serves as an economic deterrent to silo drying. Accordingly, there remains a need for solar grain drying systems that make efficient use of solar energy while being capable of continuous operation of the system as solar output varies within a treatment cycle. 
     Further, there is a need for grain drying equipment utilizing all the advantages of other energy sources while being adapted to be used in combination with solar heat as the source of energy. 
     It is also desirable to provide a silo system for use in grain drying that better maintains the temperature of the drying air so as to make the drying process more uniform and less susceptible to changes in ground temperature or other weather conditions. 
     The present invention represents an improvement over prior art apparatus and methods, such as those described in U.S. Pat. Nos. 3,919,784; 3,979,838; 4,045,880; 4,109,395; 4,169,459; 4,198,956; 4,253,244; 4,285,143; 4,368,583; 4,391,046; 4,524,528; 5,557,859; 5,028,299; 6,209,223; 6,167,638; 7,240,029; 7,461,466; 7,434,332; and 7,263,934, and in U.S. Published Patent Applications Serial Nos. 20040060250, 20040154184, 20060111035, 20060123655, 20060130357, 20070234587, and 20090094853, all of which are hereby incorporated herein by reference. The present invention may be used in accordance with such prior art systems and methods. 
     The present invention addresses remaining needs in the art including the efficient use of energy in solar grain drying, and provides benefits in the form of more uniform temperature in the drying air flow. 
     SUMMARY OF THE INVENTION 
     In general terms, the present invention includes a system and method for the drying of particulate agricultural matter, especially particulate crops, such as grains. 
     Silo Grain Drying System with Alternative Heat Transfer Fluid Sources 
     The present invention includes a system for drying a particulate agricultural product in a silo, the system comprising: (a) a silo having an interior space, the silo comprising an air conduit adapted to provide drying air to the interior space; (b) an air blower adapted to provide forced air into the air conduit; (c) at least one heat exchanger in heat transfer contact with the air conduit, the heat exchanger adapted to accept a heat transfer fluid; (d) a heat transfer fluid storage tank adapted to accept and store a heat transfer fluid, and to supply the heat transfer fluid to the heat exchanger; (e) an evacuated tube solar panel adapted to heat a heat transfer fluid and to supply the heat transfer fluid alternatively to the heat exchanger and to the heat transfer fluid storage tank; (f) a photovoltaic solar panel adapted to generate electricity and to supply electricity to the heat transfer fluid storage tank; (g) a heating unit adapted to heat the heat transfer fluid in the heat fluid storage tank, the heating unit adapted to use electricity generated by the photovoltaic solar panel; and (h) an optional controller unit adapted to determine whether the heat transfer fluid supplied to the heat exchanger by the evacuated tube solar panel is at a temperature insufficient to maintain the forced air at a pre-determined temperature, and in such event to signal the heat transfer fluid storage tank to supply the heat transfer fluid to the heat exchanger. 
     In another embodiment, the present invention includes a system for drying a particulate agricultural product in a silo, the system comprising (a) a silo having an interior space, the silo comprising an air conduit adapted to provide drying air to the interior space; (b) an air blower adapted to provide forced drying air through the air conduit; (c) at least one heat exchanger in heat transfer contact with the air conduit, the heat exchanger adapted to accept a heat transfer fluid; (d) a heat transfer fluid storage tank adapted to accept and store a heat transfer fluid, and to supply the heat transfer fluid to the at least one heat exchanger and to receive the heat transfer fluid from the at least one heat exchanger; (e) an evacuated tube solar panel adapted to heat a heat transfer fluid and to supply the heat transfer fluid to the heat transfer fluid storage tank and to receive the heat transfer fluid from the heat transfer fluid storage tank; (f) a photovoltaic solar panel adapted to generate electricity and to supply electricity to the heat transfer fluid storage tank; (g) a heating unit adapted to heat the heat transfer fluid in the heat fluid storage tank, the heating unit adapted to use electricity generated by the photovoltaic solar panel; (h) a silo air sensor adapted to determine whether the drying air is at a pre-determined temperature; and (i) a controller unit adapted to receive a signal from the silo air sensor and to control the flow of the heat transfer fluid from the heat transfer fluid storage tank in response to the signal. 
     The system may additionally comprise a valve controlling the flow of heat transfer fluid to said evacuated tube solar panel from said heat transfer fluid storage tank and an evacuated tube solar panel sensor adapted to determine whether the evacuated tube solar panel is at a temperature sufficient to maintain the heat transfer fluid at a pre-determined temperature and, in such condition, to signal the controller unit to initiate the flow of the heat transfer fluid from the heat transfer fluid storage tank to the evacuated tube solar panel. 
     The system may additionally comprise a valve controlling the flow of heat transfer fluid to the at least one heat exchanger from the heat transfer fluid storage tank and wherein the silo air sensor is adapted to determine whether the heat transfer fluid supplied to the heat exchanger by the heat transfer fluid storage tank is at a temperature insufficient to maintain the forced drying air at a pre-determined temperature and, in such event, to signal the heat transfer fluid storage tank to supply heat transfer fluid to the at least one heat exchanger. 
     The silo air sensor may also be adapted to determine whether the forced drying air is at a pre-determined temperature, and in the even it is not, to signal the heat transfer fluid storage tank to supply heat transfer fluid to the at least one heat exchanger 
     As an optional feature, the system may additionally include a heat transfer fluid storage tank sensor adapted to determine whether the heat transfer fluid in the heat transfer fluid storage tank is at a temperature insufficient to maintain drying air in the plenum within the silo at a pre-determined temperature and, in such event, to signal the controller unit to turn on electricity from the photovoltaic solar panel to the heating unit to heat the heat transfer fluid; or, optionally in the alternative, if such condition is not present, to allow the photovoltaic solar panel to provide energy to the local electricity grid. 
     In a further optional embodiment, the system may additionally be connected to a local electricity grid, and the photovoltaic solar panel may be adapted to supply electricity alternatively to the heating unit and to the local electricity grid, and wherein the heat transfer fluid storage tank sensor is adapted to determine whether the heat transfer fluid in the heat transfer fluid storage tank is at a temperature sufficient to maintain the drying air in the plenum within the silo at a pre-determined temperature and, in such event, to signal the controller unit to cause the photovoltaic solar panel to supply electricity to the local electricity grid. 
     The system may also include an air recirculation conduit adapted to accept air from the interior space of the silo from a relatively higher output position, and to provide a flow of drying air into the interior space of the silo from a relatively lower input position through the air blower disposed in the air conduit and adapted to provide forced drying air through the air conduit. 
     In those variations of the invention additionally featuring radiant heating in the silo floor, the silo may additionally comprise: (i) at least one lateral wall and a roof; and (ii) a floor portion, the floor portion comprising: (1) a base of an insulative material; (2) an aggregate floor laid above the base and in heat transfer contact with a plenum within the silo, and (3) a radiant heating conduit adapted to accept heat transfer fluid from the heat transfer fluid storage tank. It is preferred that this embodiment additionally include a valve controlling the flow of heat transfer fluid to the radiant heating conduit from the heat transfer fluid storage tank, and a radiant heating conduit sensor adapted to determine whether the heat transfer fluid supplied to the radiant heating conduits by the heat transfer fluid storage tank is at a temperature insufficient to maintain drying air in the plenum within the silo at a pre-determined temperature and, in such event, to signal the controller unit to open the valve to allow the heat transfer fluid to flow through the radiant heating conduit. 
     It is preferred that the controller unit is adapted to determine whether the heat transfer fluid supplied to the heat exchanger by the heat transfer fluid storage tank is at a temperature insufficient to maintain the forced air at a pre-determined temperature and, in such event, to signal the photovoltaic solar panel adapted to supply electricity to the heat transfer fluid storage tank heat transfer fluid storage tank to supply the heat transfer fluid to the heat exchanger. 
     Although described herein as a system wherein the heat transfer fluid storage tank is placed between the evacuated tube solar panel and the heat exchanger, other embodiments may include the use of a separate heat transfer fluid storage tank and evacuated tube solar panel, with individual conduits and valves adapted to provide alternative flow as needed to the heat exchanger(s), depending upon conditions. 
     The system may also be connected to a local electricity grid, such that the photovoltaic solar panel is adapted to supply electricity alternatively to supply electricity to the heat transfer fluid storage tank and to the local electricity grid. 
     As used herein, controller unit may be provided with a microprocessor to accept and analyze feedback signals, and to initiate control signals as described herein, in order to carry out the many required or optional functions described herein. Such a microprocessor may be provided with programmed logic instructions to perform the feedback analysis functions and control functions described herein. As may be appreciated by those of ordinary skill, the feedback and control features of the present invention may be carried out by any of a wide variety of means, including the use of varying assay points within the system, the use of equivalent system parameters, ranges and thresholds, etc. 
     A Method of Drying Using Alternative Heat Transfer Fluid Sources 
     The present invention also includes a method for drying a particulate agricultural product in a silo, the method comprising: (a) placing a particulate agricultural product in a silo having an interior space, the silo comprising an air conduit adapted to circulate drying air within the interior space; (b) operating an air blower adapted to provide forced air into the air conduit, the air blower having a heat exchanger in heat transfer contact with the air conduit, the heat exchanger adapted to accept a heat transfer fluid; (c) providing a heat transfer fluid to the heat exchanger, the heat exchanger being provided with the heat transfer fluid from a heat transfer fluid storage tank adapted to accept and store a heat transfer fluid, the heat transfer fluid storage tank dispensing heat transfer fluid to the heat exchanger alternatively by: (i) the heat transfer fluid storage tank comprising a heating unit, the heating unit heating the heat transfer fluid using electricity generated by a photovoltaic solar panel, and dispensing the heat transfer fluid to the heat exchanger; or (ii) the heat transfer fluid storage tank accepting heat transfer fluid from an evacuated tube solar panel adapted to heat the heat transfer fluid, and dispensing the heat transfer fluid to the heat exchanger; and (d) operating the blower and continuing to circulate drying air at sufficient temperature within the interior space and for sufficient time so as to reduce the moisture content of the particulate agricultural product. 
     The method may optionally additionally comprise determining whether the heat transfer fluid supplied to the heat exchanger by the evacuated tube solar panel is at a temperature insufficient to maintain the forced air at a pre-determined temperature, and in such event to signal the heat transfer fluid storage tank to supply the heat transfer fluid to the heat exchanger. 
     Also optional is the additional step of determining whether the electricity is required to maintain the heat transfer fluid at a predetermined temperature and, in the event it is not, alternatively supplying electricity to a local electricity grid. 
     Silo Design for Grain Drying System with Recirculation System and Radiant Floor 
     Another preferred system of the present invention is a system for drying a particulate agricultural product in a silo, the system comprising: (a) a silo having an interior space, the silo comprising: (i) at least one lateral wall and a roof; (ii) a floor portion, the floor portion comprising: (1) a base of an insulative material; (2) an aggregate floor laid above the base, and (3) a radiant heating conduit; (b) an air recirculation conduit adapted to accept air from the interior space of the silo from a relatively higher output position, and to provide a flow of air into the interior space of the silo from a relatively lower input position; (c) an air blower in the air recirculation conduit adapted to provide forced air through the air recirculation conduit; and (d) at least one heat exchanger in the air recirculation conduit and in heat transfer contact with the forced air, the heat exchanger adapted to accept a heat transfer fluid. 
     The system may preferably include an additional interior air conduit adapted to circulate drying air within the interior space, such as in the form of a perforated stirring bar. 
     It is also preferred that there be a first heat exchanger disposed upstream of the blower and a second heat exchanger disposed downstream of the blower. 
     The system optionally includes a thermal collector such as an evacuated tube solar panel adapted to heat a heat transfer fluid and to supply the heat transfer fluid to the at least one heat exchanger. It is also preferred that the thermal collector, such as an evacuated tube solar panel, be adapted to heat a heat transfer fluid and to supply the heat transfer fluid to the radiant heating conduits. 
     The heat transfer fluid storage tank may be adapted to accept and store a heat transfer fluid, and to supply the heat transfer fluid to the heat exchanger, and an evacuated tube solar panel may be provided to heat a heat transfer fluid and to supply the heat transfer fluid alternatively to the heat exchanger and to the heat transfer fluid storage tank, as well as optionally to the radiant heating conduits. 
     It is also preferred that the system additionally includes a photovoltaic solar panel adapted to generate electricity and to supply electricity to the heat transfer fluid storage tank, a heating unit adapted to heat the heat transfer fluid in the heat fluid storage tank, the heating unit adapted to use electricity generated by the photovoltaic solar panel; and a controller unit adapted to determine whether the heat transfer fluid supplied to the heat exchanger by the evacuated tube solar panel is at a temperature insufficient to maintain the forced air at a pre-determined temperature, and in such event to signal the heat transfer fluid storage tank to supply the heat transfer fluid to the heat exchanger. The controller unit preferably is adapted to determine whether the heat transfer fluid supplied to the heat exchanger by the heat transfer fluid storage tank is at a temperature insufficient to maintain the forced air at a pre-determined temperature, and in such event to signal the photovoltaic solar panel adapted to supply electricity to the heat transfer fluid storage tank to supply the heat transfer fluid to the heat exchanger. 
     The photovoltaic solar panel may be adapted to supply electricity alternatively to supply electricity to the heat transfer fluid storage tank and to the local electricity grid. 
     In a preferred embodiment, the present invention provides a crop particulate (grain) drying system utilizing solar energy to heat a heat transfer fluid or solution within concomitant forced-air and radiant heat systems which pass heated air through a crop particulate (grain) material contained within a conventional crop silo (bin) adjacent to a service structure housing these systems. Solar thermal energy is harnessed by an evacuated (glass) tube solar thermal panel and transferred to a fluid solution contained within a mechanical piping system. This thermal energy is exchanged to the forced-air and radiant heat systems via the thermal storage and transmission tank. Forced-air is heated via fan coils and delivered to an under floor air plenum within the crop silo (bin) situated upon a concrete foundation heated by a radiant heat loop. This heated air is passed through a perforated floor and through the crop particulate material. Air is re-circulated via return air duct, continuously or intermittently (based upon temperature and humidity demands). Vents within the crop silo (bin) allow ambient air to be introduced to the system. Systems are used in combination to increase efficiencies and lessen or eliminate demand for external sources of energy. The crop storage itself is utilized as a contributing element within the network of systems, increasing efficiency and reducing energy losses. Excess heat and, or electricity may be used to meet other on-site demands for these resources. 
     Electricity demand is met through utilization of solar photovoltaic panels backed up by connection to an external power source (i.e. power utility). Battery backup and, or an engine-driven generator may be used to supplant connection to the electrical grid. Other renewable energy sources such as wind energy or biomass could be utilized to meet on-site demand, especially in remote geographies without easy access to energy utilities. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is a side elevation view of a system for drying grain using solar energy in accordance with one embodiment of the present invention. 
         FIG. 2  is a general schematic of a system for drying grain using solar energy in accordance with one embodiment of the present invention. 
         FIG. 3  is a schematic of a heat transfer fluid and passive solar portion of a system for drying grain using solar energy in accordance with one embodiment of the present invention. 
         FIG. 4  is a schematic of an air conduit and heat exchanger portion of a system, with optional radiant silo heating, for a system for drying grain using solar energy in accordance with one embodiment of the present invention. 
         FIG. 5  is a detailed elevation view of a silo and air conduit, with optional radiant silo heating, for a system for drying grain using solar energy in accordance with one embodiment of the present invention. 
         FIG. 6  is a detailed plan view of a silo floor with optional radiant heating, for a system for drying grain using solar energy in accordance with one embodiment of the present invention. 
     
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     In accordance with the foregoing summary, the following provides a detailed description of the preferred embodiment, which is presently considered to be the best mode thereof. 
       FIGS. 1-6  may be understood through reference to the following numerals indicating the associated components and features throughout, and wherein such numerals refer to the same components and features throughout the Figures.
           0 . service structure     1 . solar photovoltaic panels     2 . DC power lines (+/−)     3 . solar PV disconnect     4 . AC/DC power inverter     5 . AC power utility disconnect     6 . AC power lines     7 . AC smart meter     8 . electrical service panel     9 . grounding     10 . AC electrical feed to solar thermal system     11 . AC electrical feed to forced-air and radiant heating systems     12 . solar thermal temperature and pump controller     13 . sensor wire to solar thermal panel temperature sensor     14 . solar thermal panel temperature sensor     15 . sensor wire to thermal storage and transfer tank temperature sensor     16 . thermal storage and transfer tank temperature sensor     17 . AC electrical feed to solar thermal heat transfer fluid circulating pump     18 . solar thermal heat transfer fluid circulating pump     19 . AC electrical feed to supplementary heating element     20 . supplementary heating element     21 . evacuated (glass) tube solar thermal panel     22 . heat transfer fluid return line     23 . expansion tank     24 . in-line check valve     25 . isolation valve     26 . thermal storage and transfer tank (system filled with a heat transfer fluid)     27 . pressure relief valve     28 . drain-down and fill valve     29 . heat transfer fluid supply line to solar thermal panel     30 . heat exchangers     31 . fan and pump controller for air and radiant heating systems     32 . sensor wire to crop silo (bin) humidistat-thermostat     33 . humidistat-thermostat     34 . AC electrical feed to fan coil heat transfer fluid circulating pump     35 . fan coil heat transfer fluid circulating pump     36 . AC electrical feed to radiant heat transfer fluid circulating pump     37 . radiant heat transfer fluid circulating pump     38 . AC electrical feed to fan (air handling unit)     39 . fan (air handling unit)     40 . heat transfer fluid supply line to fan coils     41 . thermometer     42 . flow meter     43 . fan coils     44 . heat transfer fluid return line from fan coils     45 . heat transfer fluid supply line to radiant heat loop     46 . radiant heat loop     47 . heat transfer fluid return line from radiant heat loop     48 . supply air (insulated) duct     49 . manual air volume damper     50 . supply air outlet     51 . air plenum     52 .( a ) return air inlet     52 .( b ) alternate location     53 . return air (insulated) duct     54 . air filter     55 . rigid insulation     56 . concrete slab     57 . perforated floor     58 . crop silo (bin)     59 . fill hatch and air vent     60 . crop particulate material (grain, legumes, etc.)       

       FIG. 1  is a side perspective view of a system for drying grain using solar energy in accordance with one embodiment of the present invention.  FIG. 1  shows an elevation view of a system in accordance with one embodiment of the present invention that may be comprise the major elements in a crop particulate (grain) drying system utilizing an evacuated (glass) tube solar thermal heating system  21  in conjunction with a solar photovoltaic electrical system comprising solar photovoltaic panels. An optional service structure  0  housing mechanical equipment supplies radiant heating fluid (such as in an housed tank, not shown, see thermal storage and transfer tank  26  described in  FIG. 3 , for receiving heated heat transfer fluid from evacuated (glass) tube solar thermal panel  21 ) and heated air to a crop silo (or bin)  58 . 
     For the purpose of directly heating the heat transfer fluid, any thermal collectors appropriate to the desired application may be used. There are basically three types of thermal collectors: flat-plate, evacuated-tube, and concentrating. A flat-plate collector, the most common type, is an insulated, weatherproofed box containing a dark absorber plate under one or more transparent or translucent covers. Evacuated-tube collectors are made up of rows of parallel, transparent glass tubes. Each tube consists of a glass outer tube and an inner tube, or absorber, covered with a selective coating that absorbs solar energy well but inhibits radiative heat loss. The air is withdrawn (“evacuated”) from the space between the tubes to form a vacuum, which eliminates conductive and convective heat loss. Concentrating collector applications are usually parabolic troughs that use mirrored surfaces to concentrate the sun&#39;s energy on an absorber tube (called a receiver) containing a heat-transfer fluid. The evacuated (glass) tube solar panels are preferred and may be those described in WO 2008/122968 A1, U.S. Pat. Nos. 6,819,465; 6,473,220, in U.S. Published Patent Applications Serial Nos. 20100065044 (all of which are incorporated herein by reference), or otherwise commercially available from Kingspan Solar Inc. of Jessup, Md., Thermo Technologies of Columbia, Md., and Viessmann Werke of Allendorf, Germany. Other collectors include those described in U.S. Published Patent Applications Serial Nos. 20100065104, 20090025709, 20090223550 and 20080216823 (all of which are incorporated herein by reference). 
     In a preferred embodiment,  FIG. 1  also shows silo (or bin)  58  which may be placed upon concrete slab  56 , and is preferably provided with fill hatch and air vent  59  and humidistat/thermostat  33 . Also shown is return air (insulated) duct  53  that is serviced by a return inlet  52 ( a ) (see  FIG. 5 ) that may be in an alternate location  52 ( b ). 
     Figure is a schematic illustration of a solar photovoltaic electrical system in relation to on-site electrical loads  10  and an external power utility.  FIG. 2  shows the arrangement and cooperation of several components of the system of the present invention.  FIG. 2  shows solar energy incident upon solar photovoltaic panels  1  from which DC power lines (+/−)  2  conduct electricity to solar PV disconnect  3  which is grounded at grounding point  9   a . Solar PV disconnect  3  is further connected to AC/DC power inverter  4  which supplies AC smart meter  7  with AC current via AC power line  6   a , which in turn is connected to AC power utility disconnect  5  and electrical service panel  8  via AC power lines  6   b  and  6   c , respectively. AC power utility disconnect  5  and electrical service panel  8  also preferably have individual ground points  9   b  and  9   c , respectively. AC power utility disconnect  5  is also adapted to receive electric power, such as from the local power utility, as needed. Electrical service panel  8  in turn supplies electric power to AC electrical feed  10  to solar thermal system, and to AC electrical feed  11  to forced-air and radiant heating systems  11 , as needed. The AC electrical feed to solar thermal system  10  preferably is used to heat a storage tank of heat transfer fluid as a heat source back up in the event the thermal collector system fails to provide sufficient energy to the heat exchanger(s) associated with the air inlet as described herein. 
       FIG. 3  is a schematic illustration of an evacuated (glass) tube solar thermal heating system containing a fluid utilized to transfer heat via heat exchangers  30  to a heating fan coil (air) system and radiant heating system. 
       FIG. 3  shows evacuated (glass) tube solar thermal heating system  21  connected to heat transfer fluid return line  22  which proceeds through in-line check valve  24  and isolation valve  25   a  to thermal storage and transfer tank  26  (system filled with a heat transfer fluid). Optionally, an expansion tank  23  may be provided as shown.  FIG. 3  also shows heat exchangers  30  with heat transfer fluid supply line  40  to fan coils  43  (see  FIG. 4 ), heat transfer fluid return line  44  from fan coils  43 , heat transfer fluid supply line  45  to radiant heat loop  46 , and heat transfer fluid return line  47  from radiant heat loop  46 .  FIG. 3  also shows the pressure relief valve  27  and drain-down and fill valve  28  serving tank  26 . The thermal storage and transfer tank  26  typically will be provided with heat transfer fluid supply line  29  to return heat transfer fluid to solar thermal panel  21 . This fluid supply line  29  is governed by isolation valve  25   b , solar thermal heat transfer fluid circulating pump  18  and isolation valve  25   c . Solar thermal heat transfer fluid circulating pump  18  may be serviced by AC electrical feed  17  from solar thermal temperature and pump controller  12  so as to be adapted to pump return solar thermal heat transfer fluid to solar thermal panel  21 . 
     Solar thermal temperature and pump controller  12  may also be connected by a sensor wire to solar thermal panel temperature sensor  14  to monitor the temperature of the fluid in the solar thermal panel  21 , in order to determine whether AC power is required to be supplied to the thermal storage and transfer tank  26  for supplementary heating from the AC electrical feed  10 . The solar thermal temperature and pump controller  12  is also signaled by sensor wire  15  which monitors the temperature of to thermal storage and transfer tank via thermal storage and transfer tank temperature sensor  16 . This sensor monitors the temperature of the hat transfer fluid to determine whether the heat transfer fluid requires supplementary heating if it is not being kept within the desired temperature range or at a given threshold by the fluid from the solar thermal panel  21 . If not, the solar thermal temperature and pump controller  12  may control the system by supplying supplementary heating. Thermal storage and transfer tank  26  may also be provided with supplementary heating element  20  which is adapted to be served by AC electrical feed  19  from solar thermal temperature and pump controller  12 . Solar thermal temperature and pump controller  12  receives an AC electrical feed  10  for the solar thermal system. 
     Typically and preferably, thermal storage and transfer tank temperature sensor  16  determines whether the fluid in the thermal storage and transfer tank is at sufficient temperature to provide sufficient heat to the heat exchangers to heat the drying air to the desired temperature (typically 140-200 F., preferably about 170 F.) and, if not, to cause fluid from the solar thermal panel to be brought into the thermal storage and transfer tank to increase the overall temperature of the fluid in the thermal storage and transfer tank. In addition, it is preferred that the sensors and controller also determine that there is sufficient differential between the temperature of the fluid in the thermal storage and transfer tank and the fluid in the solar thermal panel to prevent/defeat fluid transfer in the event the fluid in the solar thermal panel is not yet at sufficient temperature to increase the overall temperature of the fluid in the thermal storage and transfer tank. Thus, the solar thermal panel temperature sensor  14  and thermal storage and transfer tank temperature sensor  16  outputs are coordinated by the controller to assure that effective fluid transfer is made to increase the overall temperature of the fluid in the thermal storage and transfer tank, as the system requires. 
     Through this arrangement, heat transfer fluid may be supplied to the heat exchanger system as described in  FIG. 4 . The availability of the heat transfer fluid allows for the continuous effective operation of the grain drying system, whether during times of effectively high sunlight or during periods where the passive solar panels do not provide sufficient energy to the heat exchangers, in which case the heat transfer is actively heated by energy from the photovoltaic panels. 
     The humidistat-thermostat  33  monitors air plenum  51  of silo  58  and provides control feedback through sensor wire  32  to fan and pump controller  31  which governs the flow of air through conduit  53  by fan  39 , and the flow of heat transfer fluid into the heat exchanger system as described herein. The AC electrical feed  11  supplies AC power to forced-air and radiant heating system fan and pump controller  31 . The controller  31  is adapted to the heat transfer fluid supplied to the heat exchanger by the heat transfer fluid storage tank is at a temperature insufficient to maintain the forced air at a pre-determined temperature, and in such event to signal the photovoltaic solar panel adapted to supply electricity to the heat transfer fluid storage tank heat transfer fluid storage tank to supply the heat transfer fluid to the heat exchanger. 
     The system may be used in conjunction with a local electricity grid, with the photovoltaic solar panel being adapted to supply electricity alternatively to supply electricity to the heat transfer fluid storage tank and to the local electricity grid. 
       FIG. 4  is a schematic illustration of mechanical systems supplying heated air to a crop silo (bin)  58  via an air handling unit (i.e., fan  39 ) blowing air through heating fan coils  43  within a ducted system. Fan  39  receives control signals from fan and pump controller  31  for the air and radiant heating systems, and this control system in turn provides AC electrical feed  38 . 
       FIG. 4  shows air conduit  53 , which in this embodiment is an insulated return air duct from the upper portion of silo  58  as shown in  FIG. 1 . This conduit contains fan  39  and two heat exchangers  43 , as well as optional air filter  54 . The heat exchangers  43  receive heat transfer fluid from heat transfer fluid supply line  40  governed by isolation valves  25   d , as well as thermometer  41   a  and flow meter  42   a  that serve to provide feed back control upon the in-coming heat transfer fluid flow. Also shown in heat transfer fluid supply line  40  is drain-down and fill valve  28   a , and fan coil heat transfer fluid circulating pump  35  that receives control signals from fan and pump controller  31  governing the air and radiant heating systems, which in turn provides AC electrical feed  34  to fan coil heat transfer fluid circulating pump. Fan coil heat transfer fluid circulating pump  35  is also preferably provided with isolation valves  25   e.    
     The heat exchangers  43  release heat transfer fluid from heat transfer fluid heat transfer fluid return line  44  governed by isolation valves  25   f , as well as thermometer  41   b  and flow meter  42   b  that serve to provide feed back control over the out-going heat transfer fluid flow. Also shown in heat transfer fluid return line  44  is in line check valve  24   a  and downstream isolation valve  25   g.    
     In addition, a radiant heating system circulates heat transfer fluid through a radiant heat loop  46  underneath same crop silo (bin)  58  via heat transfer fluid supply return lines  45  and  47 . The radiant heat loop  46  receives heat transfer fluid from heat transfer fluid supply line  45  which is provided with thermometer  41   c  and flow meter  42   c  that serve to provide feed back control upon the in-coming heat transfer fluid flow. Also shown in heat transfer fluid supply line  45  is drain-down and fill valve  28   b , and fan coil heat transfer fluid circulating pump  37  that receives control signals from fan and pump controller  31  governing the air and radiant heating systems, which in turn provides AC electrical feed  36  to fan coil heat transfer fluid circulating pump. Radiant heat loop heat transfer fluid circulating pump  37  is also preferably provided with isolation valves  25   h.    
     Radiant heat loop  46  releases heat transfer fluid from heat transfer fluid heat transfer fluid return line  47  governed by check valve  24   b  and isolation valve  25   i , as well as thermometer  41   d  and flow meter  42   d  that serve to provide feed back control over the out-going heat transfer fluid flow. 
       FIG. 4  also shows the position of insulated supply air duct  48  and manual air volume damper  49 . 
       FIG. 5  is a cross-sectional view (not-to-scale) depicting the transmission of heated air to a crop silo (bin)  58  via both a forced-air system and a radiant heating system associated therewith. The heat is produced by a solar thermal heating system in conjunction with a solar photovoltaic electrical system and is transmitted to the crop particulate material  60  via an under floor air plenum  51  situated over a concrete slab  56  heated by a radiant heat loop  46  isolated from heat loss to the earth by rigid insulation  55 .  FIG. 5  shows a detailed view of the interior of silo  58 , showing insulated supply air duct  48  and manual air volume damper  49  connecting the air conduit  53  to the air plenum  51 . This view also shows an alternative location of return air inlet  52   b .  FIG. 5  also shows the perforated floor  57  through which the warmed air flow proceeds to contact the grain, such as a crop particulate material (grain, legumes, etc.) above this point.  FIG. 5  also shows the direction of the air flow through a drying zone to a wet zone and further into return air conduit  52   a , or exiting through fill hatch/air vent  59 . The temperature of the air in the plenum  51  is further maintained by action of the radiant heating system heating floor that may include rigid insulation  55  and concrete or aggregate slab  56 . 
       FIG. 5  is a schematic illustration of mechanical systems supplying heated air to a crop silo (bin)  58  via an air handling unit (fan)  39  blowing air through heating fan coils  43  within a ducted system. In addition, a radiant heating system circulates heat transfer fluid through a radiant heat loop  46  underneath same crop silo (bin)  58  via heat transfer fluid supply/return lines  45  and  47 . 
       FIG. 6  shows a detailed plan view of radiant heat loop underneath the concrete slab  56 . The exact sizing may be different for each system, depending upon volume and heat capacity of each system. Typically, the radiant tubing is oxygen-barrier ½ inch pex tubing.  FIG. 6  shows the loop in plan view. The tubing normally will be spaced at about 8 inches, again depending upon the typical ground temperature and the desired operating temperature of the air flow. In a preferred embodiment, the aggregate underlayment (base) for the concrete slab would be underneath a layer of rigid insulation. In this way, the concrete slab  56  is used as a thermal mass for heat storage and transmission in a configuration as shown. 
     It is apparent that while specific embodiments of the invention are disclosed, various modifications to the apparatus or parameters of the process may be made which will be within the spirit and scope of the invention. Therefore, the spirit and scope of the present invention should be determined by reference to the claims below.