SOLAR AUGMENTED REFRIGERATION CYCLE

Description

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a continuation of PCT/US2024/010037 filed Jan. 2, 2024 which claims the benefit of U.S. Provisional Patent Application Ser. No. 63/478,316, filed Jan. 3, 2023, which is hereby incorporated by reference.

BACKGROUND

This disclosure relates to the field of solar heat augmented refrigeration cycles.

The refrigeration cycle is used in devices such as air conditioners and heat pumps that transfer thermal energy from one area to another area using a refrigerant. Generally, the refrigeration cycle is used to transfer heat from lower temperature areas to higher temperature areas, since heat will spontaneously transfer from higher temperature areas to lower temperature areas. For example, a heat pump can be used to heat or cool the inside of the building by transferring heat energy from outside the building to inside the building, or from inside the building to outside the building. Air conditioners are similar but only provide cooling in an area.

Heat pumps, air conditioners and refrigeration/freezer systems can utilize a circulating refrigerant that transitions between a saturated liquid state and a saturated vapor state. FIG. 1 illustrates schematic 40 showing a refrigeration cycle that consist of four main components connected by pipes (illustrated by lines with arrows showing the direction of flow). The main components are compressor 50, condenser 60, expansion valve 70 and evaporator 80. Also illustrated are pipes 1, 2, 3 and 4. In pipe 1, the output refrigerant from evaporator 80 is a gas. Compressor 50 compresses the vapor in pipe 1 to a saturated vapor refrigerant in pipe 2 that is condensed to a liquid in condenser 60 in pipe 3 then the liquid is expanded into a vapor when passed through expansion valve 70 in pipe 4. The vapor is then superheated in evaporator 80.

Condenser 60 is a heat exchanger that cools the refrigerant by heating the environment around condenser 60. Evaporator 80 is a heat exchanger that heats the refrigerant by cooling the environment around evaporator 80. Compressor 50 requires energy to compress the saturated vapor to a liquid. Generally, this is electrical energy that operates an electric motor that drives the compressor, although other forms of energy could be used to operate a compressor.

In pipe 1, after passing through evaporator 80, the pressure of the vapor refrigerant is low. In pipe 2, after passing through compressor 50, the pressure of the vapor refrigerant is high. Increasing the pressure of the vapor refrigerant in compressor 50 also increases the temperature of the vapor refrigerant.

In pipe 3, after passing through condenser 60, the refrigerant is a high-pressure, high-temperature liquid. The phase change from vapor to liquid releases heat. Condenser 60 is positioned either away from the temperature control area if cooling is desired or in the temperature control area if heating is desired.

In pipe 4, after passing through expansion valve 70, the refrigerant is a low-pressure, low temperature vapor/liquid mix. Passing through evaporator 80, the refrigerant changes phase to vapor. Changing the phase of the refrigerant requires heat, which is provided by the environment surrounding evaporator 80 (which cools that area). Evaporator 80 is positioned either in the temperature control area if cooling is desired or away from the temperature control area if heating is desired.

Referring to FIGS. 2 and 3, a prior art heat pump is shown as schematic 41. The main components are compressor 50, heat exchanger 61, expansion valve 70, heat exchanger 81 and reversing valve 90. In FIG. 2, the reversing valve is set in a cooling mode, where heat exchanger 61 acts as a condenser and heat exchanger 81 acts as an evaporator. In FIG. 3, the reversing valve is set in a heating mode, where heat exchanger 61 acts as an evaporator and heat exchanger 81 acts as a condenser. The operation of the refrigeration cycle is the same as described above in FIG. 1, with the addition of the reversing valve that switches the function of the heat exchangers.

Example refrigerants include, but are not limited to, Hydrocarbons, Chlorofluorocarbons, Hydrochlorofluorocarbons, Hydrofluorocarbons, Ammonia, and Water.

Referring to FIG. 4, a standard pressure vs. enthalpy curve for an HVAC system utilizing R-410A refrigerant is illustrated. The amount of cooling done by the system is shown on the line from B to D. Cooling capacity is normally measured in BTU's. To get the total BTU's (both sensible and latent BTU's), you would measure the enthalpy entering the evaporator coil and then measure the enthalpy leaving the evaporator coil. The formula to calculate BTU's based on enthalpy is:

BTU = Delta ⁢ H ⁢ ( enthalpy ) * CFM ⁢ ( airflow ) * 
 4.5 ( elevation ⁢ constant ⁢ at ⁢ sea ⁢ level ) ( 1 )

The energy put into the system by the compressor is shown on the line from D to E. To get the total watts consumed by the system is:

Watts = ( Compressor ⁢ Amps + Supply ⁢ Fan ⁢ Amps + 
 Condenser ⁢ Fan ⁢ Amps ) ⁢ Voltage ( 2 )

Total system energy efficiency ratio (EER) is one method to determine the efficiency of a system EER is:

E ⁢ E ⁢ R = BTU Watts ( 3 )

There is a need for heat pumps with increased total system energy efficiency ratio (EER).

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a schematic of a prior art refrigeration cycle.

FIG. 2 is a schematic of a prior art heat pump using the refrigeration cycle in a cooling mode.

FIG. 3 is a schematic of the FIG. 2 prior art heat pump in a heating mode.

FIG. 4 is a prior art standard pressure vs. enthalpy curve for an HVAC system utilizing R-410A refrigerant.

FIG. 5 is a front elevational view of a solar packaged unit.

FIG. 6 is a back elevational view of the FIG. 3 solar packaged unit.

FIG. 7 is a left side elevational view of the FIG. 3 solar packaged unit.

FIG. 8 is a perspective view of a solar condenser portion of a split system.

FIG. 9 is a perspective view of a solar box, a component of the FIG. 5 solar packaged unit and FIG. 8 solar compressor.

FIG. 10 is a perspective view of a solar heat exchanger assembly, a component of the FIG. 9 solar box.

FIG. 11 is a perspective view of a solar reflective assembly, a component of the FIG. 10 solar heat exchanger assembly.

FIG. 12 is a perspective view of a solar chamber, a component of the FIG. 10 solar heat exchanger assembly.

FIG. 13 is a perspective view of a heat transfer fin, a component of the FIG. 10 solar heat exchanger assembly.

FIG. 14 is a schematic diagram of a Solar HVAC System with the solar box plumbed between the condenser heat exchanger and the expansion valve.

FIG. 15 is a schematic diagram of a Solar HVAC System with the solar box plumbed between the compressor and the reversing valve.

FIG. 16 is a pressure vs. enthalpy curve for an HVAC system utilizing R-410A refrigerant in the FIG. 15 Solar HVAC System with the solar box plumbed in vapor refrigerant.

FIG. 17 is a pressure vs. enthalpy curve for an HVAC system utilizing R-410A refrigerant in the FIG. 14 Solar HVAC System with the solar box plumbed in liquid refrigerant.

DETAILED DESCRIPTION OF THE DRAWINGS

For the purpose of promoting an understanding of the principles of the claimed invention, reference will now be made to the embodiments illustrated in the drawings and specific language will be used to describe the same. It will nevertheless be understood that no limitation of the scope of the claimed invention is thereby intended. Any alterations and further modifications in the described embodiments, and any further applications of the principles of the claimed invention as described herein are contemplated as would normally occur to one skilled in the art to which the claimed invention relates. Embodiments of the claimed invention are shown in detail, although it will be apparent to those skilled in the relevant art that some features that are not relevant to the present claimed invention may not be shown for the sake of clarity.

With respect to the specification and claims, it should be noted that the singular forms “a”, “an”, “the”, and the like include plural referents unless expressly discussed otherwise. As an illustration, references to “a device” or “the device” include one or more of such devices and equivalents thereof. It also should be noted that directional terms, such as “left”, “right”, “up”, “down”, “top”, “bottom”, and the like, are used herein solely for the convenience of the reader in order to aid in the reader's understanding of the illustrated embodiments, and it is not the intent that the use of these directional terms in any manner limit the described, illustrated, and/or claimed features to a specific direction and/or orientation.

“Heat Pump” as used here, refers to a device used to heat or cool a building using a refrigeration cycle.

“Air conditioner” as used herein, refers to a device used to cool a building using a refrigeration cycle.

“Packaged unit,” as used herein, refers to a heat pump or air conditioner where the condenser and evaporator are part of a unitary assembly.

“Split system,” as used herein, refers to a heat pump or air conditioner where the condenser and air handling unit including the evaporator are part of separate assemblies.

“Condensing unit,” as used herein, refers to a portion of a split system that includes the compressor.

“Air handling unit,” as used herein, refers to a portion of a split system that does not include the compressor.

“Refrigeration cycle device,” as used herein, refers to equipment that transfers thermal energy from one area to another area using a refrigerant. Examples include, but are not limited to, heat pumps and air conditioners.

Referring to FIGS. 5-7, solar package unit 100 is illustrated. Solar package unit 100 generally includes outside unit 110 and solar box 150. In the illustrated embodiment solar box 150 is mounted on the side of outside unit 110. In other embodiments (not illustrated), solar box 150 can be mounted in any desired location on outside unit 110. In yet other embodiments (not illustrated), solar box 150 can be located remotely from outside unit 110, allowing the location of outside unit 110 and solar box 150 to be individually optimized. Solar box 150 is preferably located to maximize solar exposure.

Referring to FIG. 8, solar condenser 120 is illustrated. Solar condenser 120 generally includes outside unit 130 and solar box 150. Solar condenser 120 is generally used with a air handling unit (not illustrated) that is generally located remotely from solar condenser 120 as part of a split system. In the illustrated embodiment solar box 150 is mounted on the side of outside unit 130. In other embodiments (not illustrated), solar box 150 can be mounted in any desired location on outside unit 130. In yet other embodiments (not illustrated), solar box 150 can be located remotely from outside unit 130, allowing the location of outside unit 130 and solar box 150 to be individually optimized. Solar box 150 is preferably located to maximize solar exposure.

Referring to FIG. 9, solar box 150 is illustrated. Solar box 150 contains solar heat exchanger assembly 151 described below. Solar box 150 includes panel 155 that is configured to allow the passage of solar energy into solar box 150.

Referring to FIGS. 10-13, solar heat exchanger assembly 151 is illustrated. Solar heat exchanger assembly 151 operates to transfer solar energy into the refrigerant by heating pipes that hold the refrigerant with ambient light, including solar energy. Solar heat exchanger assembly 151 generally includes casing 152, chambers 160, piping 172 and fins 180. As shown in FIG. 11, chambers 160 are connected to each other with fasteners, such as rivets, along joints 162. Chambers 160 are formed to a dimension to concentrate light energy to the spot within each chamber 160 where pipes 172 are positioned. Chambers 160 may optionally be lined with a solar film to increase the reflected light. As shown in FIG. 12, pipes are positioned within chambers 160 in the location that chambers 160 direct light energy to. As shown in FIG. 13, fins 180 define grove 182 that is configured to fit piping 172. As shown in FIG. 10, fins 180 are positioned over piping 172 and serve to increase the surface area of piping 172 that receives solar energy. Solar heat exchanger assembly 151 is positioned within solar box 150 and is oriented so that solar energy passing through panel 155 is received by chambers 160.

Referring to FIG. 14, a schematic diagram of solar heat pump 100 is illustrated as a split system. Solar heat pump 100 generally includes outside unit 110, inside unit 130 and solar box 150. Outside unit 110 generally includes heat exchanger 112, compressor 120, variable frequency drive (VFD) 122, sensors 124, 126, 152 and 154, controller 127, expansion valves 128 and 129 and reversing valve 160. Inside unit 130 generally includes heat exchanger 132. Outside unit 110 may be positioned within temperature control area 98. Alternatively, ductwork or the like could flow air from temperature control area 98 across heat exchanger 132. Outside unit 110 may be positioned within heat sink area 99 (such as outdoors). Alternatively, ductwork or the like could flow air from heat sink area 99 across heat exchanger 112. Another option would be to use piping to flow fluid from heat sink area 99, such as fluid pumped through pipes buried in the earth, across heat exchanger 112.

It should be noted that solar heat pump 100 is disclosed as a heating/cooling unit for a building. In alternative embodiments (not illustrated), solar heat pump 110 could be used in other heat transfer applications such as refrigeration. In such embodiments, the medium passing through heat exchanger 132 can change, but the basic plumbing can be similar. Reversing valve 160 is optional and can be omitted. For example, solar heat pump 100 may be classified as an air conditioner without reversing valve 160. In addition, if reversing valve 160 is omitted, then sensor 154 can also be omitted.

Controller 127 receives inputs from sensors 152 and 154 and controls operation of VFD 122. Sensors 152 and 154 are temperature sensor or pressure sensors or combination temperature/pressure sensors. Sensors 124 and 126 are optionally included as OEM sensors that are replaced by sensors 152 and 154 or moved to act as sensors 152 and 154.

Outside unit 110 and reversing valve 160 are configured to heat or cool temperature control area 98. Reversing valve 160 has two modes, heating and cooling. In the cooling mode, reversing valve 160 is configured with heat exchanger 132 operating as an evaporator and heat exchanger 112 operating as a condenser. In the heating mode, reversing valve 160 is configured with heat exchanger 132 operating as a condenser and heat exchanger 112 operating as an evaporator. In cooling mode, controller 127 uses sensor 152 to control VFD 122. In heating mode, controller 127 uses sensor 154 to control VFD 122.

While note illustrated, expansion valves 128 and 129 are configured with one-way check valves and one-way bypasses so that expansion valves 128 and 129 are only used in one mode. In a cooling mode, expansion valve 128 is used and expansion valve 129 is bypassed. In a heating mode, expansion valve 129 is used and expansion valve 128 is bypassed.

Solar box 150 is plumbed between whichever heat exchanger 132 or 112 is operating as the condenser and the expansion valve. In this position, the refrigerant is in a liquid state. Applicants have determined that solar energy transfer in solar box 150 is improved if the refrigerant is in a liquid state, likely because there is more density and hence more mass in a liquid compared to a vapor.

Compressor 120 increases the pressure of the refrigerant. While increasing the pressure, compressor 120 also increases the temperature of the refrigerant. In most common refrigerants, there is a direct relationship between pressure and temperature. Increasing pressure results in a predictable increase in temperature. Similarly, increasing temperature results in a predictable increase in pressure. There are charts of this relationship for common refrigerants that are used to control heat pumps. Sensors 124, 126, 152 and 154 can measure either temperature or pressure, and the controller can be programmed to operate using either temperature or pressure due to the known relationship between temperature and pressure.

Generally, compressors are controlled to a set refrigerant pressure, which is either determined directly with a pressure sensor or indirectly with a temperature sensor as described above. Sensor 124 and 126 indicate the position of such temperature or pressure sensors in a conventional, prior art system, between the compressor and the condenser heat exchanger. Solar box 150 adds heat to refrigerant thereby increasing the pressure of the refrigerant. However, the condenser is between the solar box and the original sensor location, and Applicants have determined that the addition of solar box 150 controlled with sensors placed between the compressor and the condenser generally results in operation at too high a pressure at the expansion valve, which can reduce efficiency, trip over pressure sensor and/or boil off oil in the system. However, controlling the compressor based on a sensor positioned between the solar box and the expansion valve largely addresses this issue by including the added heat in the determination of how fast to run VFD 122 to obtain the desired pressure at expansion valve 129. Sensors 152 and 154 are installed for this purpose.

Referring to FIG. 15, a schematic diagram of solar heat pump 101 is illustrated. Solar heat pump 101 is similar to solar heat pump 100 but solar box 150 is installed in a different position in the refrigeration cycle. Specifically, solar box 150 is installed after the compressor before the heat exchanger acting as the condenser. In this position the refrigerant is a vapor and the expected performance may be reduced, but in some retrofit applications there can be insufficient access to the required internal piping to plumb a system as shown in solar heat pump 100. Due to repositioning solar box 150, only a single sensor 154 is required and a single expansion valve 128 is used. Note that expansion valve 128 can be a dual direction expansion valve or can include two one-way expansion valves plumbed with one-way check valves and one-way bypasses, as known in the art.

Adding solar heat between the compressor and the condenser increases the efficiency of solar heat pump 100 by reducing the amount of energy required to compress the refrigerant to the desired pressure. FIG. 16 shows a phase diagram of solar heat pump 101 plumbed as shown in FIG. 15.

Adding solar heat between the condenser and expansion valve increases the efficiency of solar heat pump 100 by reducing the amount of energy required to compress the refrigerant to the desired pressure. FIG. 17 shows a phase diagram of solar heat pump 100 plumbed as shown in FIG. 14.

There are three common control schemes that can be used to control a VFD driven compressor in a heat pump. (1) Control based on suction pressure; (2) compare the compressor discharge pressure/temperature to the condenser discharge pressure/temperature; or (3) determine the difference between a room temperature and a room temperature setpoint and increase or decrease VFD speed to make the difference as small as possible. As described above, if using option (2), the sensor should be moved to the output of the solar panel to improve performance. If using options (1) or (3), no change to the control system is necessarily required, but additional safety temperature or pressure sensors must be included on the discharge of the solar panel to avoid overpressure situations.

The system disclosed herein has been tested in Indianapolis, Indiana and improved efficiency has been established. Tables 1 and 2 summarizes some of the results below. The information in the “Solar” row of Table 1 was gathered approximately every 30 seconds over a 45-day time period heating period and a 45-day cooling period. Outdoor temperature reading were collected for each data point. The total energy for each 45-day period is summarized in Table 1. The information in the first two rows represents the manufacture's published performance at a particular temperature. The outdoor temperature recorded for each data point was used to extrapolate the expected performance of a non-solar unit at the same temperature. The information in Table 1 is a summation of the expected performance over identical time periods. All data points without heating or cooling were discarded from the summary.

The information in the “Solar” row of Table 2 was collected over an approximate 150-day period with a different unit. The same process was used, in which data was collected every 30 seconds and corresponding expected performance data was tabulated based on measured outside temperature for each data point. Again, data points without heating or cooling were discarded.

As shown in Tables 1 and 2, increased efficiency was obtained adding a solar box for two different systems while operating both for heating and for cooling.

While the present disclosure has been illustrated and described in detail in the drawings and foregoing description, the same is to be considered as illustrative and not restrictive in character, it being understood that a preferred embodiment has been shown and described and that all changes, equivalents, and modifications that come within the spirit of the claimed invention defined by following claims are desired to be protected.

The language used in the claims and the written description and in the above definitions is to only have its plain and ordinary meaning, except for terms explicitly defined above. Such plain and ordinary meaning is defined here as inclusive of all consistent dictionary definitions from the most recently published (on the filing date of this document) general purpose Merriam-Webster dictionary.