US20150345838A1

US20150345838A1 - Geothermal heat pump system

Info

Publication number: US20150345838A1
Application number: US14/720,077
Authority: US
Inventors: Merdad Kalantari
Original assignee: Individual
Current assignee: Individual
Priority date: 2014-05-30
Filing date: 2015-05-22
Publication date: 2015-12-03

Abstract

A novel geothermal heat pump system, a novel building structure incorporating the geothermal heat pump system and a novel method of installing a geothermal heat pump system ground loop is disclosed which includes one or more geothermal pads for carrying water through the system. The geothermal pads exchange heat with the floor of the structure or may be incorporated into the floor during construction. The geothermal pads are coupled to a geothermal heat pump, which is coupled to a heat exchanger. The system includes a water pump and may include an inline water heater.

Description

CROSS-REFERENCE TO RELATED APPLICATION

This application claims the benefit of co-pending provisional application Ser. No. 62/005,694, filed on May 30, 2014, entitled GEOTHERMAL HEAT PUMP SYSTEM.

FIELD

The present invention relates generally to geothermal heating and cooling and, in particular, to a geothermal heat pump system, to a building structure incorporating the same and to a method of a geothermal heat pump system ground loop.

BACKGROUND

Geothermal heat pump systems utilize the natural difference between the temperature of the earth below the ground surface and the temperature of the air above the ground surface to create a thermal driving force for the operation of a heat exchange unit, which in turn is operated to control the internal climate of a building structure or the like. Geothermal heat pump systems are generally considered to be an environmentally-friendly alternative or supplement to conventional heating and cooling systems, such as furnaces and air conditioners, due to the fact that geothermal heat pump systems rely partially on a natural energy source.
Conventional geothermal heat pump systems comprise a heat exchange unit that is in fluid communication with a loop of tubing buried in the ground, commonly referred to as a ground loop. A heat-exchange fluid, such as a water/ethylene glycol mixture, is circulated through the ground loop, during which heat is exchanged between the earth proximate the ground loop and the heat exchange fluid. When the heat exchange fluid returns to the heat exchange unit after having circulated through the ground loop, the temperature difference between the heat exchange fluid being fed to the ground loop and the heat exchange fluid returning from the ground loop is used by the heat exchange unit to generate either heated or cooled air, using a refrigerant. This heated or cooled air is then pumped into the interior of a building structure to control its internal climate.
A variety of ground loop configurations can be used with geothermal heat pump systems. For “closed-loop” configurations, in which the ground loop provides a closed circuit for the circulating heat exchange fluid, two known configurations are commonly employed, namely horizontal closed-loop and vertical closed-loop configurations. In the horizontal closed-loop configuration, the ground loop is typically laid horizontally in a shallow trench dug into the ground adjacent the building structure to be serviced by the geothermal heat pump system. In the vertical closed-loop configuration, the ground loop is typically placed in a 100 foot to 400 foot deep well formed in ground adjacent the building structure to be serviced by the geothermal heat pump system.
Various geothermal heat pump systems have been considered. For example, U.S. Pat. No. 5,533,356 to DeMasters discloses an in-ground conduit system for a ground source heat pump. The in-ground conduit system comprises a conduit loop buried in the earth to one side of a building. At least one wing member is mounted on the conduit loop to contact the ground and resist upward movement of the conduit loop.
U.S. Pat. No. 5,339,890 to Rawlings discloses a ground source heat pump system comprising a subterranean piping installation constructed of a plurality of modular heat exchange units. The subterranean piping installation is buried to one side of a building structure.
As will be appreciated, it can be costly to install a geothermal heat pump system for servicing a building structure once the building structure has been constructed, owing to the effort required to excavate the yard surrounding building structure to install the ground loop. In cases where sufficient land or yard space is not available to accommodate the ground loop, other non-conventional provisions need to be made to install the ground loop, which can require complex and costly excavation adding to the cost of the geothermal heat pump system. As a result, there exists a need for a geothermal heat pump system that has a low installation cost and that is compatible with building structures associated with limited yard space.
It is therefore an object of the present invention to provide a novel geothermal heat pump system, a novel building structure incorporating the geothermal heat pump system and a novel method of installing a geothermal heat pump system ground loop.

SUMMARY

The present invention provides a novel geothermal heat pump system, a novel building structure incorporating the geothermal heat pump system and a novel method of installing a geothermal heat pump system ground loop. The system includes one or more geothermal pads for carrying water through the system. The geothermal pads exchange heat with the floor of the structure or may be incorporated into the floor during construction. The geothermal pads are coupled to a geothermal heat pump, which is coupled to a heat exchanger. The system includes a water pump and may include an inline water heater.
Other advantages of this invention will become apparent from the following description taken in connection with the accompanying drawings, wherein is set forth by way of illustration and example, an embodiment of the present invention.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a schematic flow diagram of the geothermal heat pump system of the present invention;

FIG. 2 is a sectional of the geothermal pad of FIG. 1 along line 2-2;

FIG. 3 is a sectional of the geothermal pad of FIG. 1 along line 3-3;

FIG. 4 is a vertical sectional of one chamber of the geothermal pad showing alternative circulation vanes;

FIG. 5 is a horizontal sectional of one chamber of the geothermal pad showing alternative circulation vanes;

FIG. 6 is a schematic control diagram of the geothermal heat pump system of the present invention;

FIG. 7 is a plan view of an installation of a plurality of geothermal pads under a storage and display rack;

FIG. 8 is an elevational view of the plurality of geothermal pads under the storage and display rack of FIG. 7; and

FIG. 9 is a partial sectional view of a plurality of geothermal pads installed below the foundation of a structure.

DETAILED DESCRIPTION

As required, detailed embodiments of the present invention are disclosed herein; however, it is to be understood that the disclosed embodiments are merely exemplary of the invention, which may be embodied in various forms. Therefore, specific structural and functional details disclosed herein are not to be interpreted as limiting, but merely as a basis for the claims and as a representative basis for teaching one skilled in the art to variously employ the present invention in virtually any appropriately detailed structure. The drawings constitute a part of this specification and include exemplary embodiments of the present invention and illustrate various objects and features thereof
Certain terminology will be used in the following description for convenience in reference only and will not be limiting. For example, the words “upwardly,” “downwardly,” “rightwardly,” “leftwardly,” “upper,” and “lower” will refer to the installed position (as shown in the drawings) of the item to which the reference is made. The words “inwardly” and “outwardly” will refer to directions toward and away from, respectively, the geometric center of the embodiment being described and designated parts thereof. Said terminology will include the words specifically mentioned, derivatives thereof and words of a similar import.
Referring initially to FIG. 1, a geothermal heat pump system of the present invention is generally indicated by reference numeral 10. The geothermal heat pump system 10 is a closed loop system that includes a geothermal pad (GTPAD) 12 that is in contact with a concrete floor or other heat exchanging surface for example, a water pump 14 to circulate the water through the system 10, an inline heater 16, and a coaxial heat exchanger 18. The coaxial heat exchanger 18 is coupled to a heat pump 20 via a refrigerant loop 21. A blower 22 forces air through an air coil 23, which exchanges heat with the refrigerant loop 21, and circulates heated or cooled air within a building. The heat pump 20 includes a compressor 25. Solenoid valves 24 and 26 control the water level in the GTPAD 12, and are used to adjust the temperature of the water in the system as necessary. An expansion tank 28 may be included in the system 10 as desired to account for the expansion and contraction of the water as it is heated and cooled. The heat pump 20 illustration is simplified in FIG. 1 to avoid cluttering the illustration with components and configurations known in the art.
In a heat pump system 20, the compressor 25 pumps the refrigerant around the refrigerant circuit, and increases the pressure of the refrigerant vapor. This increase in temperature allows the refrigerant to condense in the condenser coil at a higher temperature. The refrigerant vapor always flows through the compressor in the same direction, entering at a low pressure and exiting at a higher pressure. The heat exchanger coils, the coaxial heat exchanger 18 and the air coil 23, are coils that absorb or reject heat between two different mediums of different temperatures. Because a heat pump system 20 can reverse its function, cooling or heating, each heat exchanger coil can be an evaporator or condenser coil. In heating mode, the coaxial heat exchanger 18 acts as the evaporator and absorbs heat from the GTPAD 12 and transfers the heat to the refrigerant, while the air coil 23 acts as the condenser and rejects heat from the refrigerant warming the indoor air. In cooling mode, the air coil 23 absorbs heat from the air transferring the heat to the refrigerant thereby cooling the air, while the water absorbs heat from the refrigerant in the coaxial heat exchanger 18 and transfers the heat to the ground via the GTPAD 12.
Referring to FIGS. 2 and 3, an enlarged cross-section of the GTPAD 12 is illustrated. As illustrated in FIG. 2, four channels 30 of the GTPAD 12 are generally rectangular having an outer shell 32, an open interior 34, and a lower contact surface 36. The outer shell 32 may be made of a flexible or rigid plastic material, or other appropriate material for conveying water and for contact with a floor or other heat-exchanging surface. The GTPAD 12 includes outer structural supports 38, which may be wood or other material, and preferably wooden 2×4s. A top deck 40, such as plywood, covers and protects the channels 30, and an insulation layer 41 is sandwiched between the deck 40 and outer shell 32. The insulation layer may be an R5 or greater value, for example. Deck 40 may be plywood or other flooring material, for example. If necessary, additional internal supports between one or more of the channels 30 may be incorporated into the GTPAD 12. Ports 42 and 44 penetrate the end walls 46 and 48 of each channel 30. Ports 42 and 44 may be threaded to allow easy connection between the channels.
Referring to FIG. 4, a vertical cross-section of an embodiment of a channel 30 is illustrated with vanes 50. The vanes 50 may be desirable to disrupt the laminar flow of the water through the channel 30. The vanes 50 extend from the top inside surface 52 and the lower inside surface 54 of the channel 30. At low velocities, fluid tends to flow without lateral mixing with adjacent layers of fluid sliding past one another with no mixing. The motion of the particles of fluid in laminar flow tend to move in straight lines parallel to the walls of the pipe or channel with no eddies or swirls in the fluid. The vanes 50 may cause turbulent flow, which results in lateral mixing. This mixing may be important to increase or maximize the heat exchange between the water flowing within the channel 30 and the floor or other contact surface.
Referring to FIG. 5, a horizontal cross-section of another embodiment of a channel 30 is illustrated with vanes 56. The vanes 56 may be desirable to disrupt the laminar flow of the water through the channel 30. The vanes 56 extend from side inside surface 58 and opposite side inside surface 60 of the channel 30. At low velocities, fluid tends to flow without lateral mixing with adjacent layers of fluid sliding past one another with no mixing. The motion of the particles of fluid in laminar flow tend to move in straight lines parallel to the walls of the pipe or channel with no eddies or swirls in the fluid. The vanes 56 may cause turbulent flow, which results in lateral mixing. This mixing may be important to increase or maximize the heat exchange between the water flowing within the channel 30 and the floor or other contact surface.
A combination of the vanes 50 and 56 may be used as desired or other structures may be used to cause turbulent flow and lateral mixing of the water.
Heat transfer between the GTPAD 12 and a concrete floor may be expressed by the equation:
q=(A×ΔT)/(L/K)
where q=heat loss in BTU/hr
A=area of floor in ft²
ΔT=difference between pad water temperature and ground temperature in ° F.
L=thickness of the concrete floor in ft
K=thermal conductivity of concrete
For example in the summer months, assume a ground temperature of 60° F.; a GTPAD with a contact area of 288 ft²and a concrete floor thickness of 3.5″; and a thermal conductivity of 0.7. If the pad water temperature is 80° F., the heat loss is calculated as follows:
q=(A×ΔT)/(L/K)
q=(288×(80−60))/((3.5″/12″)/0.7)
q=5760/0.417=13,812 BTU/hr
Thus the heat loss over a 24-hour period is 13,812×24, which equals 331,510 BTU.
For a pad water temperature of 90° F., the heat loss is 20,719 BTU/hr or 497,266 BTU for a 24-hour period. The energy consumption of a 2.5 ton heat pump unit running 25% of the time is 30,000 BTU/hr×6 hours=180,000 BTU for a 24-hour period.
For another example in the winter months, assume a ground temperature of 50° F.; a GTPAD with a contact area of 288 ft²and a thickness of 3.5″; and a thermal conductivity of 0.7. If the air temperature is 40° F., the heat loss is calculated as follows:
q=(A×ΔT)/(L/K)
q=(288×(50−40))/((3.5″/12″)/0.7)
q=2880/0.417=6,906 BTU/hr
Thus the heat loss over a 24 hour period is 165,744 BTU.
For an air temperature of 35° F., the heat loss is 10,360 BTU/hr or 248,640 BTU for a 24-hour period. The energy consumption of a 2.5 ton heat pump unit running 25% of the time is 30,000 BTU/hr×6 hours=180,000 BTU for a 24-hour period.
Referring to FIGS. 1 and 6, geothermal heat pump system 10 includes a control system generally indicated by reference numeral 70. Control system 70 includes a water temperature controller 72 and a heat pump controller 74. Initially, the geothermal heat pump system 10 is filled from a fresh water source 76, such as a municipal water supply, by opening a valve or solenoid 24. Water flows into the system 10 until the system is full. Once the geothermal heat pump system 10 is filled, as indicated by a water level sensor 78 input to the water temperature controller 72, the valve or solenoid 24 is closed. The system 10 operates in two modes, cooling mode and heating mode.
In the cooling mode, such as during the warm weather months, ideally the geothermal heat pump system 10 may lower the temperature of the incoming or return air by about 20 degrees or more. In the cooling mode, the heat pump controller 74 receives an input from a thermostat 80 set to a temperature and to cool. When the air temperature sensed by the thermostat 80 exceeds a set temperature, the thermostat 80 sends a signal to the heat pump controller 74. The heat pump controller 74 sends a signal to the compressor 25 to circulate refrigerant through the refrigerant loop 21, and water pump 14 to begin circulating water through the GTPAD 12 and the coaxial heat exchanger 18. The heat pump controller 74 sends a signal to the blower 22, which pulls air into the blower housing 82 through a return air duct 84. The air is circulated through the air coil 23, which cools the air. The air then exits the blower housing 82 through a supply air duct 86 to be delivered to the vents or registers in the house or building. In the cooling mode, the air coil 23 is the evaporator coil and the coaxial heat exchanger 18 is the condenser coil. The refrigerant circulating through the air coil 23 absorbs heat from the air as the air passes over the air coil 23. The water circulating through the coaxial heat exchanger 18 absorbs heat from the refrigerant and transfers the heat to the water in the GTPAD 12. The concrete floor absorbs the heat from the GTPAD 12 and transfers the heat to the ground.
An exit water temperature sensor 88 is coupled to the water temperature controller 72 and measures the temperature of the water exiting the GTPAD 12. The water temperature is sent to the heat pump controller 74 from the water temperature controller 72. Water temperature controller 72 tracks the temperature from both the exit water temperature sensor 88 and the return water temperature sensor 90. If the exit water temperature exceeds approximately 95° F. for a period of time, which affects the efficiency of the heat pump, such as a week or more, the water temperature controller 72 may energize the inlet solenoid 24 to receive fresh cool water from the municipal water supply 76, and energize the outlet solenoid 26 to release the warm water. The warm water may be sent to a drain or may be connected to a sprinkler system to water the yard, trees or plants outside. Because the system does not require an antifreeze chemical mixed with the water, the water may be released in any manner and will not be harmful to plants or animals. Once the temperature of the water entering the GTPAD 12 has been lowered to a desired temperature, the outlet solenoid 26 is closed and the inlet solenoid 24 is closed by the water temperature controller 72. Typically, the temperature of the water from a municipal water supply may be approximately 50° F.
In the heating mode, such as during the cold weather months, ideally the geothermal heat pump system 10 may raise the temperature of the incoming or return air by about 20 degrees or more. In the heating mode, the heat pump controller 74 receives an input from a thermostat 80 set to a temperature and to heat. When the air temperature sensed by the thermostat 80 drops below a set temperature, the thermostat 78 sends a signal to the heat pump controller 74. The heat pump controller 74 sends a signal to the compressor 25 to circulate refrigerant through the refrigerant loop 21, and to the water pump 14 to begin circulating water through the geothermal heat pump system 10. The refrigerant in the refrigerant loop 21 is circulated in the opposite direction as in the cooling mode. The heat pump controller sends a signal to the blower 22, which pulls air into the blower housing 82 through a return air duct 84. As the air passes through the air coil 23, it absorbs heat from the refrigerant in the air coil, heating the air. The air then exits the blower housing 82 through an output air duct 86 to be delivered to the vents or registers in the house or building.
An exit water temperature sensor 88 is coupled to the water temperature controller 72 and measures the temperature of the water exiting the GTPAD 12. The water temperature is sent to the heat pump controller 74 from the water temperature controller 72. Water temperature controller 72 tracks the temperature from both the exit water temperature sensor 88 and the return water temperature sensor 90. If the exit water temperature drops below a predetermined temperature such as 35° F., for example, the water temperature controller 72 may turn on the inline water heater 16 to heat the circulating water and keep it from freezing. Once the temperature of the water exiting the GTPAD 12 has been raised to a desired temperature, the inline water heater 16 is turned off by the water temperature controller 72.
A water level sensor 78 may be provided to monitor the water level in the GTPAD 12. If the water level drops below a predetermined level, then the water temperature controller 72 sends an open signal to the fresh water solenoid 24 to fill the GTPAD 12 to the desired level. The water temperature controller 72 may include a memory and processor to keep a history of low level indicators received from the water level sensor 78. If the water level drops below a predetermined level more than once in a 24-hour period, or in a week, a water leak indicator 92 may be activated by the water temperature controller 72 and no further filling of the GTPAD 12 may be commanded until the water temperature controller 72 is reset.
A water leak sensor 94 may be provided, which may be placed on the floor around the periphery of the GTPAD 12 to detect any water leaks. If the water temperature controller 72 receives a signal from a water leak sensor 94 then the water leak indicator 92 may be activated by the water controller and no further filling of the GTPAD 12 may be commanded until the water temperature controller 72 is reset.
Referring to FIGS. 7 and 8, an example of an installation of the geothermal heat pump system in a commercial application is generally indicated by reference numeral 100. As shown in FIG. 7, a GTPAD 102 is configured with 15 serially connected channels 104. Water enters at one end 106 of the GTPAD 102 through inlet 108. The water then flows the length of the GTPAD 102 through three channels 104, then returns at the other end 110 of the GTPAD 102 through a connecting port 112. The water flows back and forth through the channels 104 and exits through outlet 114. In this application, the GTPAD 102 is installed in contact with the concrete floor 116 under shelving 118. As illustrated in FIG. 8, the shelving 118 may include several tiers for storing and support products 120, such as in a warehouse or a large hardware store, for example. It should be understood that fewer or more channels 104 and/or GTPADs 102 may be used as desired and configured according to the available space in the building.
Water lines 115 coupled to the inlet 108 and outlet 114 of the GTPAD 102 may be mounted and secured to the end of the shelving 118 and coupled to a heat pump and air handling unit 117. Air (heated or cooled) from the heat pump and air handling unit 117 is circulated through the building. A plurality of GTPADs 102 coupled to heat pumps and air handling units 117 may be provided as desired.
For existing structures, the GTPAD 102 may be installed anywhere that the concrete is in contact with the ground, which is the heat sink. Referring to FIG. 9, an installation of GTPADs 122 under the floor 124 of a building 126 is illustrated. The GTPADs 122 may be installed over the gravel or dirt 123 and the concrete floor 124 is poured over the GTPADS 122. The geothermal heat pump system is not shown but may be configured as shown in the previous illustrations. Water flows into the GTPADs 122 through an inlet 128. The water flows back and forth through the channels 130, from one GTPAD 122 to the next, then out of the GTPADs 122 through an outlet 132 coupled to the geothermal heat pump system. Although illustrated with only one inlet 128 and one outlet 132, there may be multiple inlets and outlets coupled to separate GTPADs 122 in any desired configuration.
It is to be understood that while certain now preferred forms of this invention have been illustrated and described, it is not limited thereto except insofar as such limitations are included in the following claims.

Claims

Having thus described the invention, what is claimed as new and desired to be secured by this patent is as follows:

1. A geothermal heat pump apparatus comprising:

a geothermal pad;

a water pump to circulate water through said geothermal pad;

a heat pump;

a heat exchanger in fluidic contact with a refrigerant circulated by said heat pump and said water circulated by said water pump;

a blower;

an air coil in fluidic contact with air circulated by said blower and said refrigerant circulated by said heat pump;

a controller coupled to said water pump, said heat pump and said blower; and

a thermostat coupled to said controller;

whereas said controller receives input from said thermostat and selectively activates said water pump to circulate said water through said geothermal pad and said heat exchanger, said heat pump to circulate said refrigerant through said heat exchanger and said air coil, and said blower to circulate air through said air coil;

whereas heat is exchanged between air and said refrigerant circulated through said air coil;

whereas heat is exchanged between said refrigerant and said water circulated through said heat exchanger; and

whereas heat is exchanged between said water and said geothermal pad.

2. The apparatus of claim 1 wherein said geothermal pad includes two or more longitudinal channels.

3. The apparatus of claim 2 wherein said two or more channels include a top inside surface and a plurality of vanes extending from said top inside surface to disrupt laminar flow of said water through said two or more channels.

4. The apparatus of claim 2 wherein said two or more channels include a lower inside surface and a plurality of vanes extending from said lower inside surface to disrupt laminar flow of said water through said two or more channels.

5. The apparatus of claim 2 wherein said two or more channels include a side inside surface and a plurality of vanes extending from said side inside surface to disrupt laminar flow of said water through said two or more channels.

6. The apparatus of claim 1 wherein said heat pump circulates said refrigerant in a first direction to cool said air and in a second direction to heat said air.

7. The apparatus of claim 1 further comprising an inlet solenoid valve coupled to a water supply and an outlet solenoid valve; said inlet solenoid valve responsive to commands received from said controller to fill said geothermal pad with water; said outlet solenoid valve responsive to commands received from said controller to empty water from said geothermal pad.

8. The apparatus of claim 7 further comprising a water level sensor coupled to said controller; whereas said controller receives input from said water level sensor and selectively activates said inlet solenoid valve to fill said geothermal pad with water.

9. A geothermal heat exchange system comprising:

a heat pump controller coupled to a compressor, a blower, a water pump, a thermostat, and a water temperature controller;

said water temperature controller coupled to an return water temperature sensor, an exit water temperature sensor, and a water level sensor;

said return water temperature sensor coupled to a return water line to a geothermal pad;

said exit water temperature sensor coupled to an exit water line from said geothermal pad;

said water pump circulating water through said geothermal pad and a heat exchanger;

said heat exchanger in fluidic contact with a refrigerant circulated by said compressor and said water circulated by said water pump;

a blower;

whereas said heat pump controller receives input from said thermostat and selectively activates said water pump to circulate said water through said geothermal pad and said heat exchanger, said heat pump to circulate said refrigerant through said heat exchanger and said air coil, and said blower to circulate said air through said air coil;

whereas heat is exchanged between said air and said refrigerant circulated through said air coil;

whereas heat is exchanged between said water and said geothermal pad.

10. The apparatus of claim 9 wherein said geothermal pad is in contact with a heat sink.

11. The apparatus of claim 9 wherein said geothermal pad is in contact with a concrete floor.

12. The apparatus of claim 9 wherein said geothermal pad includes two or more longitudinal channels.

13. The apparatus of claim 9 wherein said heat pump circulates said refrigerant in a first direction to cool said air and in a second direction to heat said air.

14. The apparatus of claim 9 further comprising an inlet solenoid valve coupled to a water supply and an outlet solenoid valve; said inlet solenoid valve responsive to commands received from said water temperature controller to fill said geothermal pad with water; said outlet solenoid valve responsive to commands received from said water temperature controller to empty water from said geothermal pad.

15. The apparatus of claim 14 whereas said controller receives input from said water level sensor and selectively activates said inlet solenoid valve to fill said geothermal pad with water when a water level in said geothermal pad is below a predetermined level.

16. The apparatus of claim 14 whereas said inlet solenoid valve is responsive to commands received from said water temperature controller to fill said geothermal pad with water when a temperature of the water is above a predetermined temperature; said outlet solenoid valve responsive to commands received from said water temperature controller to empty water from said geothermal pad.

17. The apparatus of claim 14 further comprising an inline heater in fluidic contact with said water and coupled to said water temperature controller; whereas said inline heater is responsive to commands received from said water temperature controller to heat said water when a temperature of said water is below a predetermined temperature.

18. The apparatus of claim 14 further comprising a water leak sensor coupled to said water temperature controller; whereas said water temperature controller is responsive to an input received from said water leak sensor to disable filling of said geothermal pad.