HEAT PUMP WATER HEATER WITH COMPRESSOR MODULATION TO EXTEND LOW AMBIENT OPERATION

Description

CROSS-REFERENCE TO RELATED APPLICATIONS

This application claims priority to U.S. 63/571,169, filed on Mar. 28, 2024, entitled “HEAT PUMP WATER HEATER WITH COMPRESSOR MODULATION TO EXTEND LOW AMBIENT OPERATION,” the disclosure of which is hereby incorporated herein by reference in its entirety.

BACKGROUND OF THE DISCLOSURE

Heat pump water heaters have been developed to provide hot water. Heat pump water heaters may utilize a vapor refrigeration compression cycle in a closed-loop heat exchange circuit to absorb heat from a source (e.g., air) and transfer the heat to water for storage in a hot water tank.

SUMMARY OF THE DISCLOSURE

An aspect of the present disclosure is a heat pump water heater system that is configured to increase compressor speed during cold ambient conditions to compensate for reduced mass flow rates that would occur if the compressor were to be operated at the same speed during warm and cold ambient conditions. A heat pump water heater system according to an aspect of the present disclosure may include a compressor having a compressor motor, a compressor inlet, and a compressor outlet. The system includes an evaporator having an evaporator inlet and an evaporator outlet, wherein the evaporator outlet is fluidly connected to the compressor inlet. An evaporator fan causes air to flow through the evaporator when the evaporator fan is actuated. The system further includes a heat exchanger having an inlet that is fluidly connected to the compressor outlet. The heat exchanger also includes an outlet that is fluidly connected to the evaporator inlet, whereby water flowing through the heat exchanger is heated by refrigerant flowing through the heat exchanger. The heated water from the heat exchanger may flow to a hot water tank system. The system further includes a pressure sensor that is configured to detect a pressure of refrigerant upstream of the compressor inlet. The system further includes a controller that is configured to increase a speed of the compressor motor if a pressure detected by the pressure sensor reaches a threshold pressure that is greater than a minimum allowable operating pressure whereby a mass flow rate of the compressor is increased to permit operation of the heat pump water heater system at a lower ambient temperature without reaching the minimum allowable operating pressure. The system may be configured to provide a defrost cycle if the pressure drops below the threshold pressure despite an increase in compressor speed. The defrost cycle may be initiated at an operating pressure between the threshold pressure and the minimum allowable operating pressure.

Another aspect of the present disclosure is a heat pump water heater system including a compressor having a compressor motor that is electrically powered, a compressor inlet, and a compressor outlet. The compressor defines a minimum allowable operating pressure at the compressor inlet. The system includes an evaporator having an evaporator inlet and an evaporator outlet, wherein the evaporator outlet is fluidly connected to the compressor inlet. The system further includes an evaporator fan that is configured to cause air to flow through the evaporator when the evaporator fan is actuated. A heat exchanger has an inlet that is fluidly connected to the compressor outlet, and an outlet that is fluidly connected to the evaporator inlet, whereby water flowing through the heat exchanger is heated by refrigerant flowing through the heat exchanger. The system further includes a pressure sensor that is configured to detect a pressure of refrigerant upstream of the compressor inlet to provide a measured inlet refrigerant pressure. A defrost valve system is configured to cause heated refrigerant from the compressor outlet to flow through the evaporator during a defrost cycle. The system includes a controller that is configured to: 1) increase a speed of the compressor motor if a measured inlet pressure drops to a threshold pressure that is greater than the minimum allowable operating pressure of the compressor whereby a mass flow rate of the compressor is increased to permit operation of the heat pump water heater system at a lower ambient temperature, and: 2) actuate the defrost valve system if a measured inlet pressure reaches a defrost pressure that is below the threshold pressure despite the increased speed of the compressor motor.

• • The defrost pressure may be greater than the minimum allowable operating pressure of the compressor.
  • The defrost pressure may be equal to the minimum allowable operating pressure of the compressor.
  • The controller may comprise a Variable-Frequency Drive (VFD) that is configured to provide: 1) a first operating mode in which the controller drives the compressor motor at a first frequency; and: 2) a second operating mode in which the controller drives the compressor motor at a second frequency that is greater than the first frequency. The controller may be configured to switch from the first operating mode to the second operating mode if the measured inlet pressure drops below the threshold pressure while in the first operating mode.
  • The controller may be configured to actuate the defrost valve system if the measured inlet pressure is at or below the defrost pressure while the controller is in the second operating mode.
  • The controller may be configured to default to the first operating mode whereby the controller only switches to the second operating mode if predefined operating conditions are detected.
  • The predefined operating conditions may comprise at least one operating parameter selected from the group consisting of: 1) a measured inlet pressure at or below the threshold pressure; 2) an ambient temperature at or below predefined temperature; and: 3) a heat demand from a hot water tank system that cannot be met when the VFD is driving the compressor motor at the first frequency.
  • The controller may be configured to continuously and/or repeatedly increase a frequency of electrical power to the compressor motor to maintain the measured inlet pressure at or above the threshold pressure.
  • The controller may be configured to limit increases in frequency of the electrical power to the compressor motor to a predefined maximum frequency.
  • The controller may be configured to optimize Co-efficient-of-Performance (COP) of the heat pump water heater system, wherein the COP is the heat output of the system divided by input power to the system, and wherein the controller is configured to optimize COP by controlling a speed of the compressor and/or a speed of the evaporator fan to minimize input power and maximize heat output based on a plurality of operating parameters.
  • The operating parameters may comprise ambient temperature and temperature of water entering and exiting the heat exchanger, and the controller may be configured to control: 1) the speed of the compressor, and/or: 2) the speed of the evaporator fan, based at least in part, on ambient temperature, whereby the speeds of the compressor and/or the evaporator fan are inversely related to ambient temperature. The controller may also be configured to determine heat output utilizing a difference between the temperatures of water entering and exiting the heat exchanger, and determine COP by dividing heat output by input power to the system.

Another aspect of the present disclosure is heat pump water heater system including a compressor having a compressor motor that is electrically powered. The compressor defines a minimum allowable operating pressure at the compressor inlet. The system further includes an evaporator, a heat exchanger, and a controller that is configured to: 1) increase electrical power to the compressor motor to maintain a pressure of refrigerant at an inlet of the compressor above the minimum allowable pressure, and: 2) implement a defrost cycle causing heated refrigerant to flow through the evaporator if increasing electrical power to the compressor motor is insufficient to maintain mass flow through the compressor according to predefined criteria.

• • The controller may be configured to implement a defrost cycle if a pressure of refrigerant at an inlet of the compressor falls below a predefined pressure despite increases in electrical power to the compressor motor.
  • The controller may be configured to increase electrical power to the compressor motor if a pressure of refrigerant at an inlet of the compressor is below a threshold pressure.
  • The threshold pressure may be greater than the minimum allowable pressure of the compressor.
  • The controller may comprise a Variable-Frequency Drive (VFD) that is configured to provide: 1) a first operating mode in which the controller drives the compressor motor at a first frequency; and: 2) a second operating mode in which the controller drives the compressor motor at a second frequency that is greater than the first frequency, and wherein the controller may be configured to switch from the first operating mode to the second operating mode if the measured inlet pressure drops below the threshold pressure while in the first operating mode.
  • The system may include a defrost valve system that is configured to cause heated refrigerant from the compressor outlet to flow through the evaporator during a defrost cycle. The controller may be configured to actuate the defrost valve system if the measured inlet pressure is at or below the defrost pressure while the controller is in the second operating mode.
  • The controller may be configured to default to the first operating mode whereby the controller only switches to the second operating mode if predefined operating conditions are detected.
  • The predefined operating conditions may comprise at least one operating parameter selected from the group consisting of: 1) a measured inlet pressure at or below the threshold pressure; 2) an ambient temperature at or below a predefined temperature; and: 3) a heat demand from a hot water tank system that cannot be met when the VFD is driving the compressor motor at the first frequency.

Another aspect of the present disclosure is a method of controlling a heat pump water heater having a compressor that supplies heated refrigerant to a heat exchanger to heat water, and an evaporator that is exposed to ambient air. The method includes empirically determining a relationship between operating variables including: 1) compressor speeds and 2) evaporator fan speeds that optimize a Co-efficient-of-Performance (COP) based on input parameters, wherein the COP comprises heat output of the heat pump system divided by input power to the heat pump system, and wherein the input parameter comprises: 1) temperature of water at an inlet and/or an outlet of the heat exchanger; 2) ambient air temperature; and 3) temperature and/or pressure of refrigerant at an inlet and/or at an outlet of the compressor. The method further includes controlling compressor speed and/or fan speed utilizing the relationship to maximize COP.

These and other features, advantages, and objects of the present disclosure will be further understood and appreciated by those skilled in the art by reference to the following specification, claims, and appended drawings.

BRIEF DESCRIPTION OF THE DRAWING

In the drawing:

The FIGURE is a schematic view of a heat pump water heater system according to an aspect of the present disclosure.

The components in the FIGURE are not necessarily to scale, emphasis instead being placed upon illustrating the principles described herein.

DETAILED DESCRIPTION

For purposes of description herein the terms “upper,” “lower,” “right,” “left,” “rear,” “front,” “vertical,” “horizontal,” and derivatives thereof shall relate to the disclosure as oriented in the FIGURE. However, it is to be understood that the invention may assume various alternative orientations and step sequences, except where expressly specified to the contrary. It is also to be understood that the specific devices and processes illustrated in the attached drawings, and described in the following specification, are simply exemplary embodiments of the inventive concepts defined in the appended claims. Hence, specific dimensions and other physical characteristics relating to the embodiments disclosed herein are not to be considered as limiting, unless the claims expressly state otherwise. The terms “including,” “comprises,” “comprising,” or any other variation thereof, are intended to cover a non-exclusive inclusion, such that a process, method, article, or apparatus that comprises a list of elements does not include only those elements but may include other elements not expressly listed or inherent to such process, method, article, or apparatus. An element preceded by “comprises a . . . ” does not, without more constraints, preclude the existence of additional identical elements in the process, method, article, or apparatus that comprises the element.

With reference to the FIGURE, a heat pump water heater system 1 according to an aspect of the present disclosure includes a compressor 2 that is configured to compress a refrigerant. Compressor 2 may be substantially similar to known compressors, and may include a pump that is driven by an electrically-powered motor. The refrigerant may comprise, for example, CO₂ or other suitable medium. Compressor 2 includes an inlet 3 and an outlet 4, whereby the compressor 2 causes compressed refrigerant to flow through a line 5 to a gas cooler heat exchanger 7 to heat water flowing through a water circuit 8 to provide hot water to a hot water tank system 10. The hot water tank system 10 may comprise, for example, a hot water system for a building or the like. A controller 25 is configured to control the valves and other components of heat pump water heater system 1, including a speed of compressor 2. Heat pump water heater system 1 may include a power supply 30 that is operably connected to controller 25, compressor 2, and other components of the system.

During operation, refrigerant that has been pressurized by compressor 2 flows through lines 12 to an evaporator 14. Refrigerant exiting evaporator 14 is returned to the inlet 3 of compressor 2 by lines 13. During operation, evaporator fans 15 may be actuated to increase air flow through the evaporator 14 whereby the refrigerant flowing through the evaporator 14 changes phase from a liquid to a gas. Evaporator 14 may be located in an ambient space 16. The ambient space 16 may be outside of a building whereby the ambient space 16 experiences low temperatures (e.g., below freezing) if heat pump water heater system 1 is installed in a climate that experiences cold temperatures. In general, an amount of heat that can be absorbed by the evaporator 14 is the product of the mass flow rate of the refrigerant multiplied by the change of heat content (enthalpy) that occurs in evaporator 14 as the refrigerant changes phase from liquid to gas. As the ambient temperature in ambient space 16 drops, the evaporator 14 may be required to operate at lower temperatures in order to keep balance between the energy being released from the air and the energy absorbed into the refrigerant. For pure fluids such as CO₂, pressure and temperature are dependent as the fluid changes phase from liquid to gas, such that the operating pressure (e.g. pressure of refrigerant at compressor inlet 3) also drops. For a given speed (e.g., rpm) of the compressor 2, drops in the mass flow rate of the compressor 2 may also be accompanied by drops in temperature and pressure, decreasing the heat pump's overall capacity to transfer heat and heat water supplied to hot water tank system 10.

As discussed in more detail below, the speed (mass flow rate) of compressor 2 may be increased at lower ambient temperatures to compensate for reduced mass flow rates that would occur at a constant compressor speed to thereby permit heat pump water heater system 1 to operate at lower ambient temperatures, or to permit the system 1 to utilize a smaller compressor 2.

Heat pump water heater system 1 may optionally include a recuperator 20 whereby, during normal operation (i.e., not during a defrost cycle), refrigerant flows through recuperator 20 to transfer heat to refrigerant flowing through lines 13 before the refrigerant in lines 13 returns to the compressor inlet 3, and the refrigerant exiting recuperator 20 flows through an expansion valve 11 whereby a temperature of the refrigerant is reduced before the refrigerant flows through the evaporator 14.

During a defrost cycle, defrost valves 18 and 19 may be actuated by controller 25 to cause compressed refrigerant from compressor 2 to bypass gas cooler heat exchanger 7 and recuperator 20 such that refrigerant entering evaporator 14 has a higher temperature (e.g., above freezing) to thereby temporarily heat the coils of evaporator 14 to defrost evaporator 14. The defrost cycle may be substantially similar to known defrost cycles. In general, the defrost cycle may be short enough to minimize energy loss, but long enough to defrost evaporator 14. As discussed in more detail below, controller 25 may cause a defrost cycle if a pressure of refrigerant at or upstream of compressor inlet 3 drops below a minimum pressure despite increases in compressor speed.

Heat pump water heater system 1 may include a pressure sensor 22 and a temperature sensor 23 that are configured to measure the pressure and temperature, respectively, of refrigerant flowing through line 24 upstream of inlet 3 of compressor 2. Controller 25 is operably connected to the valves and sensors of the system whereby the controller 25 may control compressor 2 based on various inputs, including sensor data. The controller 25 may be configured to control a speed of operation of compressor 2, whereby a mass flow rate of compressor 2 can be adjusted. Controller 25 may optionally comprise a Variable-Frequency Drive (VFD) that controls an rpm of compressor 2.

During the operation of heat pump water heater system 1, controller 25 may monitor pressure readings from pressure sensor 22. If the ambient air temperature drops, the operating pressure measurements from sensor 22 will also tend to decrease. The decrease in pressure measured by pressure sensor 22 generally corresponds to a decrease in the mass flow rate. Compressor 2 may have a minimum allowable operating pressure requirement, and controller 25 may be configured to turn off compressor 2 (e.g., stop the supply of electrical power to the compressor) to prevent operation of compressor 2 at or below the minimum operating pressure. Controller 25 may also be configured to increase a speed (mass flow rate) of compressor 2 if an operating pressure sensed by pressure sensor 22 drops sufficiently to reach a threshold pressure that is above the minimum allowable operating pressure for compressor 2. An increase in the operating speed of compressor 2 results in an increase in the mass flow rate and operating pressure such that the pressure measured by pressure sensor 22 does not reach the minimum allowable operating pressure.

In general, the threshold pressure may be selected (set) to avoid reaching the minimum allowable pressure without causing unnecessary increases in compressor speed. For example, the threshold pressure may be about 5 psi greater than the minimum allowable pressure, about 10 psi greater than the minimum allowable pressure, about 20 psi greater than the minimum allowable pressure, or other suitable pressure difference as required for a particular heat pump water heater system 1. In some examples, the threshold pressure may by a target percentage greater than the minimum allowable pressure. For example, the pressure threshold may be about 105%, about 110%, about 115%, or about 120% of the minimum pressure. The pressure difference between the threshold pressure and the minimum allowable operating pressure is preferably great enough to reliably prevent the system from reaching the minimum allowable pressure without causing unnecessary or excessive increases in compressor speed that could result in decreased efficiency. It will be understood that the threshold pressures discussed above are merely examples, and the present disclosure is not limited to any specific pressure threshold. Also, the magnitude of the pressure difference may be set, at least in part, to provide for optimum (e.g. most efficient) operation in a specific geographic area and climate.

Thus, the heat pump water heater system 1 may have a cold temperature (low ambient temperature) operating mode that includes increasing the compressor speed to increase the mass flow rate of refrigerant through compressor 2. Increasing the speed of compressor 2 allows the system 1 to continue operating at a lower ambient temperature by increasing the mass flow rate to prevent the operating pressure measured by pressure sensor 22 from reaching the minimum allowable pressure. Also, compared to a heat pump system that does not include a cold operating mode, system 1 may include a smaller compressor 2, yet still continue to operate at the same ambient temperature as a heat pump system having a larger compressor that does not include increased compressor speed.

It will be understood that the operating pressure measured by sensor 22 is related to the mass flow rate of the refrigerant through compressor 2. Thus, the present disclosure is not limited to measuring mass flow rates based on measuring operating pressure. In general, system 1 may utilize virtually any suitable mass flow measurement technique to control compressor speed to compensate for reduced mass flow rates that would otherwise occur if the compressor were to be operated at the same speed at both warm and cold ambient conditions. For example, the actual mass flow rate could be measured alone or in combination with one or more additional operating parameters (e.g. ambient temperature), and a suitable minimum mass flow rate could be utilized to trigger increased compressor speed. The energy balance between the air side of the evaporator and the refrigerant side of the evaporator could also be measured, and a suitable energy value could be utilized to trigger increased compressor speed. In general, the operating parameter that is utilized to trigger increased compressor speed may also be used to trigger reductions in compressor speed whereby the compressor speed returns to the “normal” (warm ambient) mode. For example, if pressure measured by sensor 22 is reduced to a first threshold, controller 25 may increase a speed of compressor 2, and controller 25 may reduce a speed of compressor 2 if the pressure measured by sensor 22 is above a second threshold. However, it will be understood that the measured operating parameter/criteria that is utilized to trigger increased compressor speed does not have to be the same operating parameter/criteria that is used to reduce compressor speed. For example, compressor speed may be increased if the mass flow rate drops to a threshold level, whereas compressor speed may be reduced if the ambient temperature increases to a minimum threshold temperature.

Controller 25 may be in communication with and/or comprise a Variable-Frequency Drive (VFD) to control the compressor 2. For example, during normal operating conditions, the VFD may drive a motor of compressor 2 at a frequency of 60 Hz, and during low-ambient temperature conditions (e.g., when the pressure measured by sensor 22 reaches the threshold pressure), the VFD can drive the motor of compressor 2 at a frequency higher than 60 Hz (e.g., 70 Hz). The increases in drive speed of compressor 2 may comprise a single step increase (e.g., 60 Hz to 70 Hz), or it may comprise a series of steps (e.g., from 60 Hz to 65 Hz, 65 Hz to 70 Hz, etc.). In an example, the VFD may increase the frequency 5 Hz (or 10 Hz) each time the pressure measured by sensor 22 reaches a first (lower) threshold, and the frequency may be reduced 5 Hz (or 10 Hz) each time the measured pressure reaches a second (higher) threshold. Alternatively, the increase may comprise a ramp function whereby, for example, the VFD gradually increases the drive frequency from 60 Hz to 70 Hz utilizing a predefined ramp function.

Alternatively, the controller may be configured to continuously vary the speed of compressor 2 if a threshold pressure is detected by sensor 22 whereby the operating pressure measured by sensor 22 is maintained at or around (e.g., slightly above) the threshold pressure by varying the speed at compressor 2.

As discussed above, controller 25 may be configured to reduce the operating speed of compressor 2 when an increased mass flow rate (compressor speed) is no longer required. For example, controller 25 may be configured to utilize predefined criteria to reduce the compressor speed to return it to the normal operating speed. The predefined criteria may comprise, for example, a pressure measured by sensor 22 that is sufficient to prevent the pressure from dropping to the minimum allowable pressure of compressor 2 if the compressor speed is returned to normal. Controller 25 may be configured to utilize empirical data and/or modeling data to predict or estimate a relationship between a drive speed of compressor 2 and a pressure measured by pressure sensor 22 at a given operating condition (e.g., ambient temperature), and the speed of compressor 2 may be returned to normal if the normal operating speed will not result in the pressure dropping below the minimum allowable (shut off) pressure. Thus, if the heat pump water heater system 1 is operating in a cold ambient mode wherein a speed of compressor 2 is increased, the controller 25 may monitor the operating pressure measured by pressure sensor 22 and the ambient temperature to determine if the speed of compressor 2 can be decreased to a normal operating speed without the pressure dropping below the threshold pressure or, alternatively, without the pressure dropping to or below the minimum allowable pressure.

Compressor 2 may also have a maximum allowable drive speed. Thus, if the ambient temperature is sufficiently low, the operating pressure sensed by pressure sensor 22 may drop to the minimum allowable pressure of compressor 2 even though compressor 2 is being driven at the compressor's maximum allowable speed. If this operating condition occurs, controller 25 may be configured to turn off compressor 2 (e.g., stop supplying electrical power to the compressor 2). Following shut down of compressor 2, the controller 25 may be configured to monitor the ambient temperature and initiate operation of compressor 2 if the ambient temperature is high enough to permit operation of compressor 2 either at a normal (default or baseline) operating speed or at an increased operating speed (cold ambient mode).

Controller 25 may be configured to actuate defrost valves 18 and 19 to cause either refrigerant from compressor 2 to flow through evaporator 14. In general, controller 25 may be configured to increase a speed of compressor 2 if an inlet pressure of compressor drops below a threshold value to thereby permit operation to continue at reduced ambient temperatures while maintaining an inlet pressure of compressor 2 above a minimum allowable inlet pressure of the compressor 2. However, increases in compressor speed may not be sufficient to maintain the inlet pressure above the minimal allowable inlet pressure for compressor pump 2. Accordingly, if an inlet pressure (e.g. a pressure measured by sensor 22) drops below the threshold pressure after a speed of compressor 2 has been increased, controller 25 may actuate a defrost cycle when the inlet pressure reaches the minimum allowable inlet pressure, or when the inlet pressure reaches a defrost inlet pressure that is between the minimum allowable inlet pressure and the threshold inlet pressure. In general, controller 25 may be configured to continue increasing a speed of compressor 2 until a maximum allowable compressor speed is reached, and controller 25 may then implement a defrost cycle if the inlet pressure reaches the defrost inlet pressure. In general, the defrost inlet pressure may be equal to the minimum allowable inlet pressure. Controller 25 may also be configured to implement a defrost cycle based on other operating parameters even if a maximum allowable compressor speed has not been reached. For example, under certain operating conditions, it may be more efficient to implement a defrost cycle rather than continue to increase compressor speed.

The controller 25 may comprise virtually any suitable programmable controller, circuit, or combination thereof. For example, controller 25 may comprise a Programmable Logic Controller (PLC) that is configured to monitor multiple parameters such as inlet and outlet temperatures of compressor 2, refrigerant pressures, ambient temperature, and power consumption. The heat pump water heater system 1 may utilize return water temperature measured by sensor 27, and/or water supply temperature measured by temperature sensor 26 to control operation of system 1. The controller 25 may be configured to utilize various inputs (e.g., measured temperatures and pressures) to maximize the Coefficient of Performance (COP) over a wide range of inlet water temperatures and ambient conditions using a multi variable regression of input parameters measured by the sensors of the heat pump water heater system 1. The output of this control system (e.g., algorithm) may vary the speed of compressor 2, the speed of evaporator fans 15, or both, to minimize the input power and maximize the heat output for a given set of conditions. In general, the COP is the product of heat output divided by input power, and system 1 (e.g., controller 25) may be configured to always operate at or near peak COP. Heat output may be determined (e.g. by controller 25) utilizing a difference in temperatures measured by sensors 26 and 27, and the flow rate and heat capacity of water flowing through heat exchanger 7. Controller 25 may be configured to determine input power by measuring and summing power consumed by the system components and/or utilizing power output from power supply 30.

For example, if the ambient temperature is warmer, which can correspond to higher operating pressures, compressor 2 and/or evaporator fans 15 can be operated at lower speeds (frequencies). If the ambient temperature is cooler, the compressor 2 and/or evaporator fans 15 can be controlled to operate at higher speeds (frequencies). For example, a second VFD may be configured to control a frequency of a motor driving each or both of the evaporator fans 15, and the controller 25 may communicate instructions or signals to the second VFD to speed up or slow down this/these motors. Thus, the controller 25 of heat pump water heater system 1 can be configured to provide an active and continuous control over the components of the heat pump water heater system 1 to optimize COP.

It will be understood by one having ordinary skill in the art that construction of the described disclosure and other components is not limited to any specific material. Other exemplary embodiments of the disclosure disclosed herein may be formed from a wide variety of materials, unless described otherwise herein.

It is also important to note that the construction and arrangement of the elements of the disclosure as shown in the exemplary embodiments is illustrative only. Although only a few embodiments of the present innovations have been described in detail in this disclosure, those skilled in the art who review this disclosure will readily appreciate that many modifications are possible (e.g., variations in sizes, dimensions, structures, shapes and proportions of the various elements, values of parameters, mounting arrangements, use of materials, colors, orientations, etc.) without materially departing from the novel teachings and advantages of the subject matter recited. For example, elements shown as integrally formed may be constructed of multiple parts or elements shown as multiple parts may be integrally formed, the operation of the interfaces may be reversed or otherwise varied, the length or width of the structures and/or members or connector or other elements of the system may be varied, the nature or number of adjustment positions provided between the elements may be varied. It should be noted that the elements and/or assemblies of the system may be constructed from any of a wide variety of materials that provide sufficient strength or durability, in any of a wide variety of colors, textures, and combinations. Accordingly, all such modifications are intended to be included within the scope of the present innovations. Other substitutions, modifications, changes, and omissions may be made in the design, operating conditions, and arrangement of the desired and other exemplary embodiments without departing from the spirit of the present innovations.

It will be understood that any described processes or steps within described processes may be combined with other disclosed processes or steps to form structures within the scope of the present disclosure. The exemplary structures and processes disclosed herein are for illustrative purposes and are not to be construed as limiting.

It is to be understood that variations and modifications can be made on the aforementioned structure without departing from the concepts of the present invention, and further it is to be understood that such concepts are intended to be covered by the following claims unless these claims by their language expressly state otherwise.