Abstract:
A method of optimizing a heat pump energy supply, comprising: sensing the ambient temperature; and responsive to the sensed ambient temperature, selecting one of a first energy source and a second energy source to provide energy for processing a working fluid of the heat pump, the second energy source different than the first energy source.

Description:
TECHNICAL FIELD 
       [0001]    The present disclosure relates generally to the field of air conditioning and in particular to a system and method for optimizing the energy usage of a heat pump utilizing a combination of waste heat, electric powered heat and combustible material powered heat. 
       BACKGROUND 
       [0002]    Heat pumps operate by extracting heat from outdoor ambient air, and transferring that heat to a climate controlled area, such as a home or business. In a cooling mode, heat pumps operate by extracting heat from the air of the climate controlled area into the ambient air. In a heating mode, heat pumps operate by extracting heat from the outside ambient air and passing the heat into the climate controlled area. Heat pumps are generally more economical to operate than conventional furnaces that burn fossil fuels. However, the coefficient of performance (COP) of the heat pump is a function of the ambient air temperature. During a heating cycle, as the ambient temperature decreases the COP of the heat pump will decrease, since more work is necessary to extract the heat from the ambient air. During the heating cycle, at a certain point the COP becomes too small to be considered economically efficient in comparison to a furnace or other fossil fuel heating source. 
         [0003]    One typical solution is to provide a backup heater to the heat pump, such that when the ambient temperature becomes too low, the heat pump will cease operation and a heater, such as a gas or electric radiator, will provide heat to the climate controlled environment. Unfortunately, this adds cost and complexity since two separate systems are needed, a heat pump and a heater. Additionally, the additional heater does not necessarily provide the most energy efficient form of heating. Moreover, typically such double systems are not able to switch between the heat pump and additional heater within an appropriate time frame to allow for an economical control of the desired target temperature of the climate controlled area. Furthermore, such a system provides no method for optimizing the energy consumption of the heat pump during a cooling cycle. 
         [0004]    Additionally, many industrial processes produce waste heat of low temperature, typically less than 150° C., which is typically too low to be used to accomplish useful work. Certain thermodynamic cycles, such as absorption refrigeration, can provide environmental cooling and heating from low grade heat sources. Similarly, solar thermal energy received in a solar collector such as a concentrating type or an evacuated tube type is typically of the order of waste heat, and has been employed in absorption chillers to provide environmental cooling. Unfortunately, the absorption refrigeration cycles typically used suffer from inefficiency, and are typically unable to achieve a COP greater than about 0.7, where the term COP is defined as Δ/ΔW, where ΔQ is defined as the heating/cooling load change and ΔW is defined as the work consumed by the cooling system. Other types of heat pumps achieve a greater COP, however the energy output of the waste/solar heat source is not always sufficient to power such a heat pump. 
         [0005]    What is desired is a method and system for optimizing the energy supply of a heat pump, so that the cost of operation of the heat pump will be continuously maintained at a minimum for a wide range of ambient air temperatures. 
       SUMMARY OF INVENTION 
       [0006]    In view of the discussion provided above and other considerations, the present disclosure provides methods and apparatus to overcome some or all of the disadvantages of prior and present methods of energy supply optimization of heat pumps. Other new and useful advantages of the present methods and apparatus will also be described herein and can be appreciated by those skilled in the art. 
         [0007]    In an exemplary embodiment, a heat pump apparatus is provided, the heat pump apparatus comprising: a control circuitry; a first energy source input port arranged to receive energy from a first energy source; a second energy source input port arranged to receive energy from a second energy source, the second energy source different than the first energy source, each of the first and second energy source input ports arranged to provide energy for processing a working fluid contained within the heat pump apparatus, responsive to the control circuitry; and an ambient temperature sensor in communication with the control circuitry, the ambient temperature sensor arranged to sense the temperature of the ambient air, wherein the control circuitry is arranged to alternately select one of the first energy source input port and the second energy source input port to provide energy for processing the working fluid, the selection responsive to the sensed ambient air temperature. 
         [0008]    In one embodiment, the control circuitry is arranged to determine the required energy output from each of the first energy source and the second energy source to provide energy for processing the single working fluid, responsive to the sensed ambient temperature, and wherein the control circuitry is arranged to determine the cost of operation of the heat pump apparatus by each of the first energy source and the second energy source responsive to the determined required energy output, the selection performed responsive to the determined cost of operation. In another embodiment, the first energy source comprises a source of electricity and the second energy source comprises a combustible material powered water heater. In one further embodiment, the heat pump apparatus further comprises: a compressor in electrical communication with the first energy source input port, the compressor arranged to compress the working fluid; and a heat exchanger in thermal communication with the second energy source input port, the heat exchanger arranged to transfer heat from the combustible material powered water heater to the working fluid. 
         [0009]    In one embodiment, the heat pump apparatus further comprises a third energy source input port arranged to receive energy from a third energy source, different that the first and second energy sources, the third energy source input port arranged to provide energy for processing the working fluid, wherein the control circuitry is further arranged to determine the energy output of the third energy source, the selection performed only in the event that the determined energy output of the third energy source is less than the energy requirements of the heat pump apparatus. In one further embodiment, the third energy source comprises one of a waste heat source and a solar water heater. 
         [0010]    In one yet further embodiment, the heat pump apparatus further comprises a heat exchanger in thermal communication with: the second energy source input port; and the third energy source input port. In another further embodiment, the arrangement of the third energy source input to provide energy for processing the working fluid is responsive to the control circuitry, wherein in the event that the determined energy output of the third energy source is less than the energy requirements of the heat pump apparatus, the control circuitry is further arranged to control the third energy source input port to provide energy for processing the working fluid. 
         [0011]    In one independent embodiment, a method of optimizing a heat pump energy supply is provided, the method comprising: sensing the ambient temperature; responsive to the sensed ambient temperature, selecting one of a first energy source and a second energy source to provide energy for processing a working fluid of the heat pump, the second energy source different than the first energy source. 
         [0012]    In one embodiment, the method further comprises: determining the required energy output from each of the first energy source and the second energy source to provide energy for processing the working fluid, responsive to the sensed ambient temperature; and determining the cost of operation of the heat pump by each of the first energy source and the second energy source responsive to the determined required energy output, the selecting performed responsive to the determined cost of operation. In another embodiment, the first energy source comprises a source of electricity and the second energy source comprises a combustible material powered water heater. In one further embodiment, the selecting the first energy source comprises providing electric power from the source of electricity to a compressor, wherein the selecting the second energy source comprises providing heat from the combustible material powered water heater to a heat exchanger. 
         [0013]    In one embodiment, the method further comprises determining the energy output of a third energy source, the third energy source different that the first and second energy sources, the selecting performed only in the event that the determined energy output of the third energy source is less that the energy requirements of the heat pump. In one further embodiment, the third energy source comprises one of a waste heat source and a solar water heater. 
         [0014]    In one yet further embodiment, the method further comprises providing heat from the output of the second and third energy sources to a heat exchanger. In another embodiment, the method further comprises in the event that the determined energy output of the third energy source is less than the energy requirements of the heat pump, providing energy output from the third energy source for processing the working fluid. 
         [0015]    In another independent embodiment, a non-transitory computer readable medium having instructions stored thereon is provided, which, when executed by one or more processors, causes the one or more processors to perform operations, the operations comprising: sensing the ambient temperature; and responsive to the sensed ambient temperature, selecting one of a first energy source and a second energy source to provide energy for processing a working fluid of the heat pump, the second energy source different than the first energy source. 
         [0016]    In one embodiment, the operations further comprise: determining the required energy output from each of the first energy source and the second energy source to provide energy for processing the working fluid, responsive to the sensed ambient temperature; and determining the cost of operation of the heat pump by each of the first energy source and the second energy source responsive to the determined required energy output, the selecting performed responsive to the determined cost of operation. In another embodiment, the first energy source comprises a source of electricity and the second energy source comprises a combustible material powered water heater. In one further embodiment, the selecting the first energy source comprises providing electric power from the source of electricity to a compressor, and wherein the selecting the second energy source comprises providing heat from the combustible material powered water heater to a heat exchanger. 
         [0017]    In one embodiment, the operations further comprise determining the energy output of a third energy source, the third energy source different that the first and second energy sources, the selecting performed only in the event that the determined energy output of the third energy source is less that the energy requirements of the heat pump. In one further embodiment, the third energy source comprises one of a waste heat source and a solar water heater. 
         [0018]    In one yet further embodiment, the operations further comprise providing heat from the output of the second and third energy sources to a heat exchanger. In another further embodiment, the operations further comprise, in the event that the determined energy output of the third energy source is less than the energy requirements of the heat pump, providing energy output from the third energy source for processing the working fluid. 
         [0019]    Additional features and advantages of the invention will become apparent from the following drawings and description. 
     
    
     
       BRIEF DESCRIPTION OF DRAWINGS 
         [0020]    For a better understanding of the invention and to show how the same may be carried into effect, reference will now be made, purely by way of example, to the accompanying drawings in which like numerals designate corresponding elements or sections throughout. 
           [0021]    With specific reference now to the drawings in detail, it is stressed that the particulars shown are by way of example and for purposes of illustrative discussion of the preferred embodiments of the present invention only, and are presented in the cause of providing what is believed to be the most useful and readily understood description of the principles and conceptual aspects of the invention. In this regard, no attempt is made to show structural details of the invention in more detail than is necessary for a fundamental understanding of the invention, the description taken with the drawings making apparent to those skilled in the art how the several forms of the invention may be embodied in practice. In the accompanying drawings: 
           [0022]      FIG. 1A  illustrates a high level schematic diagram of a heat pump apparatus, according to certain embodiments; 
           [0023]      FIG. 1B  illustrates a high level schematic diagram of a heat pump apparatus, comprising a compressor and a heat exchanger, according to certain embodiments; 
           [0024]      FIG. 1C  illustrates a high level schematic diagram of a control circuitry of the heat pump apparatuses of  FIGS. 1A-1B ; 
           [0025]      FIG. 2  illustrates a high level flow chart of a method of operation of the heat pump apparatus of  FIG. 1B  in a heating cycle, according to certain embodiments; and 
           [0026]      FIG. 3  illustrates a high level flow chart of a method of operation of the heat pump apparatus of  FIG. 1B  in a cooling cycle, according to certain embodiments. 
       
    
    
     DESCRIPTION OF EMBODIMENTS 
       [0027]    Before explaining at least one embodiment in detail, it is to be understood that the invention is not limited in its application to the details of construction and the arrangement of the components set forth in the following description or illustrated in the drawings. The invention is applicable to other embodiments or of being practiced or carried out in various ways. Also, it is to be understood that the phraseology and terminology employed herein is for the purpose of description and should not be regarded as limiting. In particular, the term connected as used herein is not meant to be limited to a direct connection, and allows for intermediary devices or components without limitation. 
         [0028]      FIG. 1A  illustrates a high level schematic diagram of a heat pump apparatus  10 , according to certain embodiments. Heat pump apparatus  10  comprises: an external unit  20 ; an internal unit  30 ; a combustible material driven heat energy source  40 ; and an electric energy source  50 . External unit  20  comprises: a combustible material driven energy source input port  60 ; an electric energy source input port  70 ; a control circuitry  80 ; a heat driven heat pump sub-system  90 ; an electric driven heat pump sub-system  100 ; and an ambient temperature sensor  110 . 
         [0029]    External unit  20  is positioned outside a climate controlled area  120  and internal unit  30  is positioned within climate controlled area  120 . External unit  20  is in fluidic communication with internal unit  30  such that working fluid of heat pump apparatus  10 , such as refrigerant, is transferred bi-directionally between external unit  20  and internal unit  30 . In one embodiment, power is supplied from external unit  20  to internal unit  30  and internal unit  30  is further in communication with control circuitry  80  of external unit  20 . Heat pump apparatus  10  is illustrated and described as comprising an internal unit  30  and an external unit  20 , however this is not meant to be limiting in any way and a heat pump apparatus comprising only an internal unit is contemplated without exceeding the scope. 
         [0030]    In one embodiment, combustible material driven energy source  40  comprises a water heater, optionally heated by burning any of natural gas, liquid petroleum gas, diesel combustible material and heating oil, without limitation. The output of combustible material driven energy source  40  is coupled to heat driven heat pump sub-system  90 , via combustible material driven energy source input port  60  of external unit  20 , and is arranged to provide heat thereto. Electric energy source  50  is coupled to electric driven heat pump sub-system  100 , via electric energy source input port  70 , and is arranged to provide electricity thereto. In one embodiment, electric energy source  50  comprises an electric mains power supply. Ambient temperature sensor  110  is arranged to sense the temperature of the ambient air surrounding external unit  20 . Heat driven heat pump sub-system  90  and electric driven heat pump sub-system  100  are illustrated as separate units, however this is not meant to be limiting in any way and heat pump apparatus  10  is particularly contemplated with heat driven heat pump sub-system  90  and electric driven heat pump sub-system  100  being integrated within a single system, each arranged to process a common working fluid to provide heating/cooling. 
         [0031]    Heat driven heat pump sub-system  90  and electric driven heat pump sub-system  100  are arranged to provide heating/cooling via internal unit  30  to adjust the temperature in climate controlled area  120 . A working liquid, such as a refrigerant, is provided within external unit  20 . In one further embodiment, heat driven heat pump sub-system  90  and electric driven heat pump sub-system  100  are each arranged to provide compression and expansion of the working fluid in order to provide heating/cooling, as known to those skilled in the art. In another further embodiment, heat driven heat pump sub-system  90  and electric driven air conditioning sub-system  100  are each arranged to provide an absorption cycle utilizing a water-ammonia mixture in order to provide heating/cooling, as known to those skilled in the art. In another embodiment, heat driven heat pump sub-system  90  and electric driven air conditioning sub-system  100  are arranged to provide heating/cooling as described in U.S. Patent Application Publication S/N 2012/0023982 to Berson et al., of publication date Feb. 2, 2012, the entire contents of which are incorporated herein by reference. As described therein, heat driven heat pump sub-system  90  and electric driven air conditioning sub-system  100  comprise an integrated single unit. 
         [0032]    Control circuitry  80  is in communication with heat driven heat pump sub-system  90 , electric driven heat pump sub system  100  and ambient temperature sensor  110 . In one embodiment, control circuitry  80  is further in communication with combustible material driven energy source input port  60  and electric energy source input port  70 . In another, optionally alternate, embodiment, control circuitry  80  is in communication with combustible material driven energy source  40  and electric energy source  50 . 
         [0033]    In operation, as will be described further below, control circuitry  80  is arranged to receive from ambient temperature sensor  110  the sensed temperature of the ambient air. Responsive to the received temperature, control circuitry  80  is arranged to determine the energy requirements of each of heat driven heat pump sub-system  90  and electric driven heat pump sub-system  100  to adjust the temperature of the air within climate controlled area  120  to a desired target temperature. Control circuitry  80  is further arranged to determine the monetary cost of the above determined energy requirements. Control circuitry  80  is further arranged to select and operate a particular one of heat driven heat pump sub-system  90  and electric driven heat pump sub system  100 , the selection performed responsive to the determination of the energy requirements exhibiting the least monetary cost. Advantageously, a single heat pump  10 , optionally with a single working fluid, and with a single internal unit  30 , is alternately operated by two different energy sources, responsive to the monetary cost thereof. 
         [0034]      FIG. 1B  illustrates a high level schematic diagram of a heat pump apparatus  200 , according to certain embodiments. Heat pump apparatus  200  comprises: an external unit  220 ; an internal unit  30 ; a combustible material driven energy source  40 ; an electric energy source  50 ; and a solar/waste heat source  230 . External unit  220  comprises: a combined combustible material driven energy source and solar/waste heat source input port  170 ; an electric energy source input port  70 ; a control circuitry  80 ; a heat driven heat pump sub-system  250 , comprising a heat exchanger  260 ; an electric driven heat pump sub-system  270 , comprising a compressor  280 ; and an ambient temperature sensor  110 . Solar/waste heat source  230  in one embodiment comprises one or more solar panels. In another embodiment, solar/waste heat source  230  comprises a waste heat source. 
         [0035]    External unit  220  is positioned outside climate controlled area  120  and internal unit  30  is positioned within climate controlled area  120 , as described above in relation to heat pump apparatus  10  of  FIG. 1A . External unit  220  is in fluidic communication with internal unit  30  such that working fluid of heat pump apparatus  200 , such as refrigerant, is transferred bi-directionally between external unit  220  and internal unit  30 . In one embodiment, power is supplied from external unit  220  to internal unit  30  and internal unit  30  is further in communication with control circuitry  80  of external unit  220 . Heat pump apparatus  200  is illustrated and described as comprising an internal unit  30  and an external unit  220 , however this is not meant to be limiting in any way and a heat pump apparatus comprising only an internal unit is contemplated without exceeding the scope. 
         [0036]    The output of combustible material driven heat energy source  40  is coupled to heat driven heat pump sub-system  250 , via combustible material driven energy source input port  60  of external unit  220 , and is arranged to provide heat thereto. Electric energy source  50  is coupled to electric driven heat pump sub-system  270 , via electric energy source input port  70 , and is arranged to provide electricity thereto. 
         [0037]    Solar/waste heat source  230  is coupled to heat driven heat pump sub-system  250 , via combustible material driven energy source input port  60 , and is arranged to provide heat thereto. Solar/waste heat source is in thermal communication with heat driven heat pump sub-system  250 , and in particular to heat exchanger  260  thereof. In another embodiment, combustible material driven energy source  40  and solar/waste heat source  230  are both arranged to provide hot water to heat exchanger  260  of heat driven heat pump sub-system  250 . Heat pump apparatus  200  is illustrated where combustible material driven energy source  40  and solar/waste heat source  230  are arranged in a serial formation, however this is not meant to be limiting in any way. In another embodiment, combustible material driven energy source  40  and solar/waste heat source  230  can be thermally coupled to heat driven heat pump sub-system  250  in a parallel configuration, without exceeding the scope. In one embodiment, heat exchanger  260  is arranged to transfer heat from the received hot water to the working fluid of heat pump apparatus  200 , such as a refrigerant. Compressor  280  of electric driven heat pump sub-system  270  is arranged to provide a vapor compression cycle for the operation liquid of heat pump apparatus  200 . 
         [0038]    Heat driven heat pump sub-system  250  and electric driven heat pump sub-system  270  are illustrated as separate units, however this is not meant to be limiting in any way and heat pump apparatus  200  is particularly contemplated with heat driven heat pump sub-system  250  and electric driven heat pump sub-system  270  being integrated within a single system, each arranged to process a common working fluid to provide heating/cooling. 
         [0039]    Control circuitry  80  is in communication with heat driven heat pump sub-system  250 , electric driven heat pump sub-system  270  and ambient temperature sensor  110 . In one embodiment, control circuitry  80  is further in communication with combustible material driven energy source input port  60  and electric energy source input port  70 . In another, optionally alternate, embodiment, control circuitry  80  is in communication with combustible material driven energy source  40  and electric energy source  50 . 
         [0040]    In operation, control circuitry  80  is arranged to determine the energy output of solar/waste heat source  230 . In one embodiment, the energy output is determined by sensing the temperature output of solar/waste heat source  230 . In the event that control circuitry  80  determines that the energy output of solar/waste heat source  230  is less than the energy needed for heat pump apparatus  200  to adjust the temperature of climate controlled area  120  to the desired temperature, control circuitry  80  is arranged to select one of heat driven heat pump sub-system  250  and electric driven heat pump sub-system  270 , as described above in relation to heat pump apparatus  10  of  FIG. 1A . In one embodiment, as will be described below, in the event that control circuitry  80  selects heat driven heat pump sub-system  250 , both combustible material driven energy source  40  and solar/waste heat source  230  provide power thereto. In the event that control circuitry  80  selects electric driven heat pump sub-system  270 , control circuitry  80  is further arranged, in parallel, to control heat driven heat pump sub-system  250  to provide heating/cooling with power being provided by solar/waste heat source  230 . Thus, both heat driven heat pump sub-system  250  and electric driven heat pump sub-system  270  provide heating to climate controlled area  120 . 
         [0041]      FIG. 1C  illustrates a high level block diagram of control circuitry  80  of heat pump apparatus  10  of  FIG. 1A  and heat pump apparatus  200  of  FIG. 1B . Control circuitry  80  comprises: a solar/waste heat energy output determination functionality  290 ; an energy consumption determination functionality  300 , arranged to determine the energy consumption of each of combustible material driven energy source  40  and electric energy source  50 , as will be described below; a monetary cost determination functionality  310 , arranged to determine the monetary cost of operating heat driven heat pump sub-systems  90  and  250 , and electric driven heat pump sub-systems  100  and  270 , as will be described below; a selection functionality  320 , arranged to select one or more of heat driven heat pump sub-systems  90  and  250 , and electric driven heat pump sub-systems  100  and  270  to operate the respective one of heat pumps  10  and  200 , as will be described below. Solar/waste heat energy output determination functionality  290 , energy consumption determination functionality  300 , monetary cost determination functionality  310  and selection functionality  320  can each be implemented by any of: a dedicated functionality; computer readable instructions for a general purpose computing device or processor, the readable instructions stored on a memory  330  and arranged to be run by a processor  340 ; dedicated hardware; and a dedicated control circuitry, without limitation. 
         [0042]      FIG. 2  illustrates a high level flow chart of a method of operation of heat pump apparatus  200  of  FIG. 1B  in a heating cycle, according to certain embodiments. In stage  1000 , control circuitry  80  is arranged to receive a temperature reading of the temperature within climate controlled area  120  and the desired temperature, from internal unit  30 . In stage  1010 , control circuitry  80  is arranged to determine the required heating load to bring the temperature of climate controlled area  120  to the desired temperature. The term ‘determine’ is not meant to be limited to an exact determination and is particularly meant to include an approximation. In stage  1020 , solar/waste heat energy output determination functionality  290  of control circuitry  80  is arranged to determine the energy output of solar/waste heat source  230 . Optionally, the energy output is determined by sensing the output temperature of the heat of solar/waste heat source  230 , optionally by sensing the temperature of the heat supply fluid of the combined combustible material driven energy source  40  and solar/waste heat source input port  170  and flow. 
         [0043]    In stage  1030 , selection functionality  320  is arranged to compare the determined energy output of solar/waste heat source  230  of stage  1020  with the determined required heating load of stage  1010 . In the event that the determined energy output of solar/waste heat source  230  is less than required heating load, in stage  1040  energy consumption determination functionality  300  is arranged to receive the sensed ambient temperature from ambient temperature sensor  110 . 
         [0044]    In stage  1050 , energy consumption determination functionality  300  is arranged to determine the required energy consumption of each of heat driven heat pump sub-system  250  and electric driven heat pump sub-system  270  to provide the determined heating load of stage  1010 , the required energy consumption determined responsive to the sensed ambient temperature of stage  1040 . In particular, energy consumption determination functionality  300  is arranged to determine how much energy would need to be produced from each of combustible material driven energy source  40  and electric energy source  50  to power heat pump apparatus  200 , optionally after subtracting the provided energy from solar/waste heat source  230 , as will be described below. In one embodiment, the required energy consumption is determined responsive to a pre-measured function of the operation of each of heat driven heat pump sub-system  250  and electric driven heat pump sub-system  270  for one or more measured ambient temperatures. In another embodiment, the required energy consumption is determined responsive to a lookup table comprising measured energy requirements of each of heat driven heat pump sub-system  250  and electric driven heat pump sub-system  270  for a plurality of ambient temperature ranges. In another embodiment, the required energy consumption is determined responsive to known thermodynamic properties of heat driven heat pump sub-system  250  and electric driven heat pump sub-system  270 . Optionally, the required energy consumption is determined only for the portion of the heating load which cannot sufficiently be supplied by solar/waste heat source  230 . 
         [0045]    In stage  1060 , monetary cost determination functionality  310  of control circuitry  80  is arranged to determine the monetary cost of operation for each of heat driven heat pump sub-system  250  and electric driven heat pump sub-system  270 . In particular, the determined required energy consumption of stage  1050  is multiplied by the monetary cost per unit of the combustible material of combustible material driven energy source  40  and of electricity. Optionally, the monetary cost per unit is periodically updated. 
         [0046]    In stage  1070 , selection functionality  320  is arranged to determine which of heat driven heat pump sub-system  250  and electric driven heat pump sub-system  270  is cheaper to operate. In stage  1080 , selection functionality  320  is arranged to select the one of heat driven heat pump sub-system  250  and electric driven heat pump sub-system  270  which is cheaper to operate, and control the selected sub-system to provide the desired heating cycle. Thus, the most economically efficient energy source is utilized to provide energy to process the working fluid of heat pump apparatus  200 . Optionally, heat driven heat pump sub-system  250  is continuously operated by the energy output of solar/waste heat source  230  and is supplemented by either: electric driven heat pump sub-system  270 ; or the addition of the heat energy output of combustible material driven energy source  40  to heat driven heat pump sub-system  250 . 
         [0047]    In the event that in stage  1030  selection functionality  320  determines that the energy output of solar/waste heat source  230  is sufficient for the required heating load, in stage  1090  heat driven heat pump sub-system  250  is operated by the energy output of solar/waste heat source  230 , thereby operating heat pump apparatus  200 . 
         [0048]      FIG. 3  illustrates a high level flow chart of a method of operation of heat pump apparatus  200  of  FIG. 1B  in a cooling cycle, according to certain embodiments. In stage  2000 , control circuitry  80  is arranged to receive a temperature reading of the temperature within climate controlled area  120  and the desired temperature, from internal unit  30 . In stage  2010 , control circuitry  80  is arranged to determine the required cooling load to bring the temperature of climate controlled area  120  to the desired temperature. In stage  2020 , solar/waste heat energy output determination functionality  290  of control circuitry  80  is arranged to determine the energy output of solar/waste heat source  230 . Optionally, the energy output is determined by sensing the output temperature of the heat of solar/waste heat source  230 . 
         [0049]    In stage  2030 , selection functionality  320  is arranged to compare the determined energy output of solar/waste heat source  230  of stage  2020  with the determined required cooling load of stage  2010 . In the event that the determined energy output of solar/waste heat source  230  is less than required cooling load, in stage  2040 , energy consumption determination functionality  300  is arranged to determine the required energy consumption of each of heat driven heat pump sub-system  250  and electric driven heat pump sub-system  270  to provide the determined cooling load of stage  2010 . In particular, energy consumption determination functionality  300  is arranged to determine how much energy would need to be produced from each of combustible material driven energy source  40  and electric energy source  50  to power heat pump apparatus  200 . Optionally, the required energy consumption is determined only for the portion of the cooling load which cannot sufficiently be supplied by solar/waste heat source  230 . 
         [0050]    In stage  2050 , monetary cost determination functionality  310  of control circuitry  80  is arranged to determine the monetary cost of operation for each of heat driven heat pump sub-system  250  and electric driven heat pump sub-system  270 . In particular, the determined required energy consumption of stage  1050  is multiplied by the monetary cost per unit of the combustible material of combustible material driven energy source  40  and of electricity. Optionally, the monetary cost per unit is periodically updated. 
         [0051]    In stage  2060 , selection functionality  320  is arranged to determine which of heat driven heat pump sub-system  250  and electric driven heat pump sub-system  270  is cheaper to operate. In stage  2070 , selection functionality  320  is arranged to select the one of heat driven heat pump sub-system  250  and electric driven heat pump sub-system  270  which is cheaper to operate, and control the selected sub-system to provide the desired cooling cycle. Thus, the most economically efficient energy source is utilized to provide energy to process the working fluid of heat pump apparatus  200 . Optionally, heat driven heat pump sub-system  250  is continuously operated by the energy output of solar/waste heat source  230  and is supplemented by either: electric driven heat pump sub-system  270 ; or the addition of the heat energy output of combustible material driven energy source  40  to heat driven heat pump sub-system  250 . 
         [0052]    In the event that in stage  2030  selection functionality  320  determines that the energy output of solar/waste heat source  230  is sufficient for the required cooling load, in stage  2070  heat driven heat pump sub-system  250  is operated by the energy output of solar/waste heat source  230 , thereby operating heat pump apparatus  200 . 
         [0053]    The method of operation of heat pump apparatus  10  of  FIG. 1A  is in all respects similar to the method of operation of heat pump apparatus  200  of  FIG. 1B  described above, with the exception that solar/waste heat source  230  is not provided. Thus, in the interest of brevity, the method of operation thereof will not be further described. 
         [0054]    It is appreciated that certain features of the invention, which are, for clarity, described in the context of separate embodiments, may also be provided in combination in a single embodiment. Conversely, various features of the invention which are, for brevity, described in the context of a single embodiment, may also be provided separately or in any suitable sub-combination. 
         [0055]    Unless otherwise defined, all technical and scientific terms used herein have the same meanings as are commonly understood by one of ordinary skill in the art to which this invention belongs. Although methods similar or equivalent to those described herein can be used in the practice or testing of the present invention, suitable methods are described herein. 
         [0056]    All publications, patent applications, patents, and other references mentioned herein are incorporated by reference in their entirety. In case of conflict, the patent specification, including definitions, will prevail. In addition, the materials, methods, and examples are illustrative only and not intended to be limiting. 
         [0057]    The terms “include”, “comprise” and “have” and their conjugates as used herein mean “including but not necessarily limited to”. The term “connected” is not limited to a direct connection, and connection via intermediary devices is specifically included. 
         [0058]    It will be appreciated by persons skilled in the art that the present invention is not limited to what has been particularly shown and described hereinabove. Rather the scope of the present invention is defined by the appended claims and includes both combinations and sub-combinations of the various features described hereinabove as well as variations and modifications thereof, which would occur to persons skilled in the art upon reading the foregoing description.