Solar Augmented Refrigeration Cycle

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.

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.illustrates schematicshowing 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, condenser, expansion valveand evaporator. Also illustrated are pipes,,and. In pipe, the output refrigerant from evaporatoris a gas. Compressorcompresses the vapor in pipeto a saturated vapor refrigerant in pipethat is condensed to a liquid in condenserin pipethen the liquid is expanded into a vapor when passed through expansion valvein pipe. The vapor is then superheated in evaporator.

Condenseris a heat exchanger that cools the refrigerant by heating the environment around condenser. Evaporatoris a heat exchanger that heats the refrigerant by cooling the environment around evaporator. Compressorrequires 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, after passing through evaporator, the pressure of the vapor refrigerant is low. In pipe, after passing through compressor, the pressure of the vapor refrigerant is high. Increasing the pressure of the vapor refrigerant in compressoralso increases the temperature of the vapor refrigerant.

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

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

Referring to, a prior art heat pump is shown as schematic. The main components are compressor, heat exchanger, expansion valve, heat exchangerand reversing valve. In, the reversing valve is set in a cooling mode, where heat exchangeracts as a condenser and heat exchangeracts as an evaporator. In, the reversing valve is set in a heating mode, where heat exchangeracts as an evaporator and heat exchangeracts as a condenser. The operation of the refrigeration cycle is the same as described above in, 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, 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:

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:

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

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

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, solar package unitis illustrated. Solar package unitgenerally includes outside unitand solar box. In the illustrated embodiment solar boxis mounted on the side of outside unit. In other embodiments (not illustrated), solar boxcan be mounted in any desired location on outside unit. In yet other embodiments (not illustrated), solar boxcan be located remotely from outside unit, allowing the location of outside unitand solar boxto be individually optimized. Solar boxis preferably located to maximize solar exposure.

Referring to, solar condenseris illustrated. Solar condensergenerally includes outside unitand solar box. Solar condenseris generally used with a air handling unit (not illustrated) that is generally located remotely from solar condenseras part of a split system. In the illustrated embodiment solar boxis mounted on the side of outside unit. In other embodiments (not illustrated), solar boxcan be mounted in any desired location on outside unit. In yet other embodiments (not illustrated), solar boxcan be located remotely from outside unit, allowing the location of outside unitand solar boxto be individually optimized. Solar boxis preferably located to maximize solar exposure.

Referring to, solar boxis illustrated. Solar boxcontains solar heat exchanger assemblydescribed below. Solar boxincludes panelthat is configured to allow the passage of solar energy into solar box.

Referring to, solar heat exchanger assemblyis illustrated. Solar heat exchanger assemblyoperates to transfer solar energy into the refrigerant by heating pipes that hold the refrigerant with ambient light, including solar energy. Solar heat exchanger assemblygenerally includes casing, chambers, pipingand fins. As shown in, chambersare connected to each other with fasteners, such as rivets, along joints. Chambersare formed to a dimension to concentrate light energy to the spot within each chamberwhere pipesare positioned. Chambersmay optionally be lined with a solar film to increase the reflected light. As shown in, pipes are positioned within chambersin the location that chambersdirect light energy to. As shown in, finsdefine grovethat is configured to fit piping. As shown in, finsare positioned over pipingand serve to increase the surface area of pipingthat receives solar energy. Solar heat exchanger assemblyis positioned within solar boxand is oriented so that solar energy passing through panelis received by chambers.

Referring to, a schematic diagram of solar heat pumpis illustrated as a split system. Solar heat pumpgenerally includes outside unit, inside unitand solar box. Outside unitgenerally includes heat exchanger, compressor, variable frequency drive (VFD), sensors,,and, controller, expansion valvesandand reversing valve. Inside unitgenerally includes heat exchanger. Outside unitmay be positioned within temperature control area. Alternatively, ductwork or the like could flow air from temperature control areaacross heat exchanger. Outside unitmay be positioned within heat sink area(such as outdoors). Alternatively, ductwork or the like could flow air from heat sink areaacross heat exchanger. Another option would be to use piping to flow fluid from heat sink area, such as fluid pumped through pipes buried in the earth, across heat exchanger.

It should be noted that solar heat pumpis disclosed as a heating/cooling unit for a building. In alternative embodiments (not illustrated), solar heat pumpcould be used in other heat transfer applications such as refrigeration. In such embodiments, the medium passing through heat exchangercan change, but the basic plumbing can be similar. Reversing valveis optional and can be omitted. For example, solar heat pumpmay be classified as an air conditioner without reversing valve. In addition, if reversing valveis omitted, then sensorcan also be omitted.

Controllerreceives inputs from sensorsandand controls operation of VFD. Sensorsandare temperature sensor or pressure sensors or combination temperature/pressure sensors. Sensorsandare optionally included as OEM sensors that are replaced by sensorsandor moved to act as sensorsand.

Outside unitand reversing valveare configured to heat or cool temperature control area. Reversing valvehas two modes, heating and cooling. In the cooling mode, reversing valveis configured with heat exchangeroperating as an evaporator and heat exchangeroperating as a condenser. In the heating mode, reversing valveis configured with heat exchangeroperating as a condenser and heat exchangeroperating as an evaporator. In cooling mode, controlleruses sensorto control VFD. In heating mode, controlleruses sensorto control VFD.

While note illustrated, expansion valvesandare configured with one-way check valves and one-way bypasses so that expansion valvesandare only used in one mode. In a cooling mode, expansion valveis used and expansion valveis bypassed. In a heating mode, expansion valveis used and expansion valveis bypassed.

Solar boxis plumbed between whichever heat exchangeroris 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 boxis 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.

Compressorincreases the pressure of the refrigerant. While increasing the pressure, compressoralso 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,,andcan 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. Sensorandindicate the position of such temperature or pressure sensors in a conventional, prior art system, between the compressor and the condenser heat exchanger. Solar boxadds 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 boxcontrolled 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 VFDto obtain the desired pressure at expansion valve. Sensorsandare installed for this purpose.

Referring to, a schematic diagram of solar heat pumpis illustrated. Solar heat pumpis similar to solar heat pumpbut solar boxis installed in a different position in the refrigeration cycle. Specifically, solar boxis 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. Due to repositioning solar box, only a single sensoris required and a single expansion valveis used. Note that expansion valvecan 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 pumpby reducing the amount of energy required to compress the refrigerant to the desired pressure.shows a phase diagram of solar heat pumpplumbed as shown in.

Adding solar heat between the condenser and expansion valve increases the efficiency of solar heat pumpby reducing the amount of energy required to compress the refrigerant to the desired pressure.shows a phase diagram of solar heat pumpplumbed as shown in.

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.