US20130333859A1

US20130333859A1 - Geothermal column

Info

Publication number: US20130333859A1
Application number: US13/883,431
Authority: US
Inventors: Shawn Genung; Tony Penachio
Original assignee: GEOENERGY ENTERPRISES LLC
Current assignee: GEOENERGY ENTERPRISES LLC
Priority date: 2010-11-04
Filing date: 2011-08-03
Publication date: 2013-12-19
Also published as: EP2635856A4; WO2012060912A1; CA2817047A1; EP2635856A1

Abstract

An improved heat transfer column for geothermal heating and cooling in which refrigerant lines are wound in a spiral fashion about a vertically oriented support. The spiral tubing is surrounded by a flexible, semi-flexible, or rigid liner which is filled with water, the liner being positioned within a cavity in an earth mass. During operation, water within the tube rises and/or by convection and transfers heat evenly to the water within the liner for subsequent transfer to the earth mass. This heat is subsequently extracted from or rejected into the earth mass during a heat transfer cycle, and means is provided for transfer of a portion of the heat in the water to the ambient atmosphere.

Description

CROSS REFERENCE TO RELATED APPLICATIONS

The present application claims priority to U.S. Provisional application No. 61/410,050 filed Nov. 4, 2010, which is herein incorporated by reference in its entirety.

FIELD OF THE INVENTION

This invention relates generally to the field of geothermal heating and cooling, and more particularly to an improved heat transfer column positioned within an earth mass for transfer of heat to and from the earth mass.

BACKGROUND OF THE INVENTION

Any publications or references discussed herein are presented to describe the background of the invention and to provide additional detail regarding its practice. Nothing herein is to be construed as an admission that the inventors are not entitled to antedate such disclosure by virtue of prior invention.
Geothermal energy is becoming more and more important in the global environment as the supply of fossil fuels diminish, the demand for energy increases, control and demands from oil producing companies are at issue and the cost of energy continues to rise. Although large geothermal energy production facilities are being used throughout the world to produce more and more electricity especially in areas like California where there is tremendous inner earth activity, more focus needs to be placed on individual systems which are based on the earth's constant temperature at shallow depths to enable efficient heating and cooling for buildings and which can be installed at the site of use.
In order for individual systems to gain broader market acceptance, there is a need for better control of the earth-refrigerant interface, easier installation methods, and greater efficiencies.

SUMMARY OF THE INVENTION

These features, together with other objects and advantages which will become subsequently apparent in light of the present description, reside in the details of construction and operation as more fully hereinafter described and claimed, reference being had to the accompanying drawings forming a part hereof, wherein like numerals refer to like parts throughout.
An object of the present invention is to provide an improved earth-coupling in the form of a subsurface heat transfer column that is configured so that it is easy to install, has enhanced heat transfer qualities that uses an antifreeze-free liquid disposed therewithin to transfer heat to or from the surrounding earth mass in substantially vertical orientation. The antifreeze-free liquid eliminates the associated costs of such antifreeze fluid and also reduces the possibility of aquifer, groundwater or siol pollution by potentially environmentally hazardous antifreeze agents such as those commonly found in other geothermal heat exchange systems. This orientation and approach requires far less digging, drilling and landmass than conventional horizontal and deep vertical well systems and provides low impact to the environment (i.e. is “green”).
One embodiment of the improved heat transfer column includes at least one spirally wound refrigeration coil configured to communicate with a heat pump compressor; a hollow tube having an outer wall of diameter substantially greater than that of the at least one spirally wound refrigeration coil and positioned so as to surround said at least one spirally wound refrigeration coil, said outer wall having a substantially rigid configuration so that said hollow tube maintains its shape under the ordinary conditions of stress in its deployment; and a support member configured to retain a shape of said at least one spirally wound refrigeration coil and maintain a centrally located position of said at least one spirally wound refrigeration coil within said hollow tube.
In addition to the above aspects, the substantially rigid hollow tube configuration of the present invention allows for the production of a pre-fabricated unit that can be installed quickly and easily in the field without the need of skilled laborers. The outer wall may be constructed from flexible, rigid, or semi-rigid corrugated material designed to more efficiently transfer heat energy to the environment such that an antifreeze-free liquid vehicle in the hollow tube can be used, which is better for the environment. That is, the improved wall construction and heat circulation within the hollow tube of the present invention is such that antifreeze is not necessary, reducing the chance of contaminating the surrounding soil should an accidental leak/spill occur.
The new factory assembled unit of the improved geothermal column of the present invention are positioned within an earth mass whereby during operation, the refrigerant coils transfer heat to and from the antifreeze-free liquid vehicle disposed within the hollow tube to cause a convection cycle within the antifreeze-free liquid to bring the antifreeze-free liquid to a more uniform temperature throughout so as to prevent freezing in one part and overheating in others. This configuration and structure results in a superior degree of heat transfer with a reduction of hot or cold spots as would be experienced in traditional direct exchange geothermal technologies. This system can be used to replace traditional non-geothermal and geothermal HVAC (heating, ventilating and air conditioning) systems within buildings and structures and can be powered by the existing electrical grid, on-site or off-site stand alone electrical generators, solar voltaic cells, fuel cells or other such self contained electrical energy producing sources or devices.

BRIEF DESCRIPTION OF THE DRAWING

In the drawing, to which reference will be made in the specification, similar reference characters have been employed to designate corresponding parts throughout the several views.

FIGS. 1A to 1C are perspective views of various stages of cutaways of one embodiment of a geothermal column according to an embodiment of the present invention.

FIG. 2 is a cross sectional view of a geothermal column according to an embodiment of the present invention.

FIG. 3 is a top view of a geothermal column according to an embodiment of the present invention.

FIGS. 4-5 are perspective views of the geothermal column according to an embodiment of the present invention.

DETAILED DESCRIPTION OF THE DISCLOSED EMBODIMENT

The present invention may be understood more readily by reference to the following detailed description of the invention taken in connection with the accompanying figures, which form a part of this disclosure. It is to be understood that this invention is not limited to the specific devices, methods, conditions or parameters described and/or shown herein, and that the terminology used herein is for the purpose of describing particular embodiments by way of example only and is not intended to be limiting of the claimed invention.
As used in the specification and including the appended claims, the singular forms “a,” “an,” and “the” include the plural, and reference to a particular numerical value includes at least that particular value, unless the context clearly dictates otherwise.
Ranges may be expressed herein as from “about” or “approximately” one particular value and/or to “about” or “approximately” another particular value. When such a range is expressed, another embodiment includes from the one particular value and/or to the other particular value. Similarly, when values are expressed as approximations, by use of the antecedent “about,” it will be understood that the particular value forms another embodiment.
It is also understood that all spatial references, such as, for example, horizontal, vertical, top, upper, lower, bottom, left and right, are for illustrative purposes only and can be varied within the scope of the disclosure. For example, the references “upper” and “lower” are relative and used only in the context to the other, and are not necessarily “superior” and “inferior”.
All methods described herein may be performed in any suitable order unless otherwise indicated herein or otherwise clearly contradicted by context. The use of any and all examples, or exemplary language (e.g., “such as”) provided herein, is intended merely to better illuminate the invention and does not pose a limitation on the scope of the invention unless otherwise claimed. No language in the specification should be construed as indicating any non-claimed element as essential to the practice of the invention.
As used herein, “comprising,” “including,” “containing,” “characterized by,” and grammatical equivalents thereof are inclusive or open-ended terms that do not exclude additional, unrecited elements or method steps, but will also be understood to include the more restrictive terms “consisting of and “consisting essentially of.”
The following discussion includes a description of a new and improved geothermal heat pump system of the present invention, related components and exemplary methods of employing the device in accordance with the principles of the present disclosure. Alternate embodiments are also disclosed. The geothermal heat pump system of the present invention provides a geothermal system that utilizes a vertical geothermal heat exchange column to exchange heat with the surrounding soil environment in an efficient and environmentally safe way. The system is designed to reduce the use of fossil fuels and therefore reduce the carbon footprint associated with conventional heating and cooling systems presently available on the market today.
Reference will now be made in detail to the exemplary embodiments of the present disclosure, which are illustrated in the accompanying figures. Turning now to the drawings, there are illustrated components of the geothermal column in accordance with the principles of the present disclosure.
In accordance with the invention, the device comprises a geothermal column, generally indicated by reference character 10, which includes at least one spirally wound refrigeration coil 11. The spirally wound refrigeration coil 11 can be configured to communicate with a heat pump compressor (not shown). These connections can be facilitated through ports 20 and 21 located on top cap 19. A refrigerant fluid such as a fluorocarbon (e.g. Freon®) optionally containing a lubricant oil (e.g., hydrocarbon or silicone based lubricant oil) is pumped through the refrigerant coil during operation of the geothermal column.
Also included in the geothermal column 10 is a hollow tube 12, which may have either horizontal, vertical, spiral or flat outer wall corrugations. The hollow tube 12 includes an outer wall 13 of a diameter substantially greater than that of the spirally wound refrigeration coil 11. The outer wall 13 can be positioned so as to surround the spirally wound refrigeration coil 11. The outer wall 13 can be of a substantially rigid configuration so that the hollow tube 12 maintains its shape. The geothermal column 10 also can include a support member 14, shown in this embodiment as being comprised of a column 17 and a plurality of combs 18 constructed, for example, as radially extending fins. Annular supports 23 are situated in a manner so as to retain their position within the hollow tube 12. The inner radius of the annular supports 23 is greater than the distance from the center of the column and an extended end 18a of each comb 18 if combs are employed in the embodiment. The combs 18 used in conjunction with the annular supports 23 restrict lateral movement of the support member 14 and allow vertical movement of the support member 14.
A bottom cap 22 is securely attachable to the bottom of the hollow tube 12 in a manner to provide a water tight seal between the bottom cap 22 and the hollow tube 12. The top cap may be fastened to the hollow tube 12 in such a way as to allow removal for service but secure attachment for transport and installation. This removable method of securement may allow for venting of any internal pressures built up within the column 10. Likewise, an alternate methodology of top cap securement would envision it being fastened and sealed to the hollow tube in a similar manner as the bottom cap.
The support member 14 is attached to the top cap 19. The support member 14 is configured to retain the shape of the spirally wound refrigeration coil 11. The support member 14 can also function to maintain a centrally located position of the spirally wound refrigeration coil 11 within said hollow tube 12.
The geothermal column 10 is designed to be positioned within a void in a surrounding earth mass (not shown). A non-antifreeze fluid 16 fills the space within the hollow tube 12 and surrounds substantially all of the surface area of the spirally wound refrigeration coil 11; water is a preferred non-anti-freeze fluid 16. The spirally wound refrigeration coil 11 is sized to optimum performance levels based on system requirements. System requirements can include size of an area to be heated/cooled, geological conditions in and around the geothermal column installation area, etc. The geothermal heat exchange column components are sized independently and as a system to match heat exchange from the copper coil to water to the heat exchange from the water to the earth, while optimizing the trade off between pressure drop and component cost. At the same time, critical oil entrainment velocities are ensured, and coil diameter to column diameter ratios are maintained to facilitate convective mixing in the described annulus. Further, overall dimensions are selected from a limited array of values that are constrained by commonly available materials (e.g. standard copper tube diameters, standard corrugated column diameters and lengths, common augur bit diameters, etc.) and practically maneuvered and transported sizes. Additionally, practicality is exercised in sizing geothermal columns to factors of or fractions of heating and cooling tons (one ton=12,000 btuh and is the commonly used measurement of HVAC system size). The required refrigerant velocity for oil entrainment is given roughly by the equation:
MinimumVelocity=A*SquareRoot(InnerDiameter)
where A is a constant that varies depending upon refrigerant phase and orientation (horizontal or vertical) of flow. Mass flow through each circuit (coil) within the heat exchanger is based on the rated mass flow of the selected compressor and its rated tonnage:
MassFlowCircuit=MassFlowSystem/ColumnsPerSystem/CircuitsPerColumn.
Minimum required mass flow through each circuit is determined by calculating the mass flow through a tube of given diameter in the liquid phase vertical orientation with certain density characteristics:
MinimumMassFlow=MinimumVelocity*CrossSectionalArea*Density(p,t).
Equating MassFlowCircuit to MinimumMassFlow allows a direct relationship between pipe diameter (via CrossSectionalArea) and the required number of circuits per column. Discretion here must be used to select applicable results based on practical applications such as even numbers of circuits or reasonable numbers of circuits relative to creating a practically sized manifold. Given the number of circuits required per column at a given pipe diameter as well as a mass flow at that diameter, and assuming certain operating conditions near the extremes (for example water temperatures near 32 or 90 degrees F.) one skilled in the art can determine the required length of tubing for effecting phase change from liquid to vapor or vice versa. Further, based upon this required circuit length and associated velocity and density at certain conditions including vapor quality, one can determine the pressure drop along the length of the circuit. Finally given the length of circuit, number of circuits, cost of raw materials, and pressure drop along the length, one can evaluate the tradeoff of pressure drop against added cost—both of which impact the success of the invention negatively. The column containment vessel is sized based upon both the volume of the fluid contained, which is a function of the physical dimensions of the containment, and the amount of energy which can be transferred to or from the column which is based upon the tempeature differential between the fluid and the earth, the surface area of the transfer medium, and the thermal conductivities of the water, the containment, and the soil. The transfer rate of energy between the heat exchanger coil and the water given adequate minima of design is a function of the number of columns per the rated capacity of the compressor (e.g. two columns per ton), and as such the minimum design of the geothermal column is to sufficiently match that heat exchange into the earth. As the energy is absorbed or rejected by the earth, the earth will subsequently change temperature. As the temperature is measured in all directions away from the heat exchange column, the temperature change asymptotically approaches zero. Based upon a proposed work load of the system and an allowable earth temperature change rate, the minimum required geothermal column spacing can be determined for a geothermal column of particular size and energy transfer rate.
In a preferred embodiment at least one of upper oil trap 24, upper oil trap 25, and lower oil traps 26 provide oil entrainment and return. Oil entrainment and return is a critical design issue in nearly all HVAC products, as standard compressors are sealed and do not contain independent oil reservoirs. As such, the compressor relies on the refrigerant to carry oil away from and returning to the compressor in order to maintain lubrication. While the oil is designed to be miscible in the refrigerant, there is a certain velocity that is required in order to keep the oil from falling out of suspension. Oil separation resulting from poor design or improper operation can result in insufficient return and ultimately compressor failure. Additionally, in long piping runs or in unusually high vertical drops, oil which has naturally fallen out of suspension upon shut down of a system has a tendency to migrate to a natural low point. Often when the system is restarted, that oil only very slowly or never returns to the compressor. Vertical drops and rises and long piping runs are unavoidable aspects of the present invention. Embodiments of the present invention include optimized piping sizing to ensure sufficient oil entrainment, but also include newly designed oil traps into the piping configuration. Oil traps 24, 25 and/or 26 are incorporated at the top entrance and exit points of the spirally wound refrigeration coil 11. Upper oil traps 24 and/or 25 include a loop design having loops approximately 8″ in diameter oriented in a vertical plane. Lower oil traps 26 include a U-bend design.
Spirally wound refrigeration coil 11 includes one or more individual sections. In the drawings two sections 11 a and 11 b are shown. While individual sections are coiled and stacked vertically along the column 17, the lower exit of each coil extends to the lowest point in the column to equalize pressure head among all sections and to equalize the oil “plug” induced pressures among all circuits, aiding in oil return from the lowest points in the systems. That is, each section 11 a and 11 b are equal in length. By varying the number of sections, the heating/cooling capacity of the geothermal column 10 can be varied. For example, each section can represent ¼ of a ton of conditioning capacity—i.e. two sections can be incorporated into a ½-ton geothermal column 10, and four sections can be incorporated into a 1-ton geothermal column 10. As stated above, each section should preferably be of equal length in order to ensure equal refrigerant distribution to each column as a result of pressure differentials.
Sections 11 a and 11 b of the spirally wound refrigeration coil 11 can be so arranged such that the refrigerant enters at a plurality of positions in the coil and exits from the upper region. This arrangement assures that there is an equal distribution of refrigerant in the spirally wound refrigeration coil 11 so that the heat transfer can be uniform throughout the device, which, in turn, can prevent sections of the tubing from overheating or freezing.
Sections 11 a and 11 b of the spirally wound refrigeration coil 11 are preferably constructed from copper tubing. The tubing, which is preferably between one-eighth of an inch to 1 inch in diameter, are in full contact with the non-antifreeze liquid 16 in the hollow tube 12. The diameter of the tubing is determined by the number of columns and the cooling/heating capacity that the system is designed to cool/heat. By design, the non-antifreeze liquid 16 contained within the hollow tube 12 at the lower region is heated to a greater temperature than at the upper region, which causes the water within the tube to move upward to create a cyclic motion.
Depending upon operational mode (that is, heating or cooling mode), continuing compressor operation may cause an increase in the temperature of the lower region thereby increasing the rate of flow of the tube and, as a result, the mixing rate of the liquid mass is also increased. Since heat transfer is a function of temperature difference, the greater the difference between the refrigerant temperature and the water, the greater the heat transfer there between. Similarly, as heat is transferred from the refrigerant to the water, the difference between the water and the earth mass increases as does the heat transfer.
Although the support member 14 is depicted in FIGS. 1A to 1C as a column 17 and a plurality of combs 18, the support member 14 can be configured in other forms. As stated above, one use of the support member 14 is to maintain the form of the spirally wound refrigeration coil 11, while another use of the support member 14 is to maintain the lateral position of the spirally wound refrigeration coil 11 within the hollow tube 12. Yet another use of support member 14 is to provide vertical lifting support to the spirally wound refrigeration coil 11 during repair and/or replacement, to be described in more detail below.
In light of these uses, column 17 can be for example tubular in nature, i.e. a pipe, a thin rod, etc. Another embodiment envisions the use of spacing clips, other attachment devices or methodologies such as fusion welding that can be used to secure the tubing of the spirally wound refrigeration coil 11 to the column 17 and to maintain an evenly spaced coil.
Lift support 27 is provided on the top cap 19 of the geothermal column 10 to provide an attachment location for lifting means to lift the geothermal column 10. Lifting is required during installation and repair. During the installation process the top cap 19 can be secured to the hollow tube 12 and the entire geothermal column 10 can be lifted to be inserted into a pre-bored hole in the earth. During repair, the top cap 19 is unsecured from the hollow tube 12 and the top cap 19 the support member 14 and the spirally wound refrigeration coil 11 can be removed for inspection and access. This repairable design is unique to the present invention and prevents the need to excavate the entire geothermal column 10 for repair. Even in the event that the hollow tube 12 develops a leak, the top cap 19 the support member 14 and the spirally wound refrigeration coil 11 can be removed to effect a repair on the hollow tube 12. One embodiment of the repair envisions the use of a flexible non-porous insert that can be inserted into the hollow tube 12, and into which the top cap 19 the support member 14 and the spirally wound refrigeration coil 11 can be reinserted.
Also shown on top cap 19 are ports 28 and 29. Ports 28 and 29 can be used for access to the interior of hollow tube 12. Access can be used to fill the hollow tube 12 with the non-antifreeze fluid 16 after the geothermal column 10 is installed. In addition, a temp sensor and fluid level switch (not shown) can be installed and accessed through ports 28 and/or 29.
The geothermal column 10 is not normally a sealed unit, and as such, changes in temperature can result in expansion and contraction of the geothermal column 10 and subsequently the earth surrounding it. As such, there is moderate opportunity for water to escape as a result of evaporation during operation of a system incorporating a geothermal column 10. Loss of the non-anti-freeze fluid 16 can be detrimental to the efficient operation of the system incorporating a geothermal column 10. In order to mitigate this possibility, a float switch at the top of each geothermal column 10 wired to a single or multiple water solenoid valve(s) (not shown) and a power supply can be included. The solenoid valve(s) is/are plumbed into a water supply and, upon the triggering of the circuit by the float switch indicating an insufficient water level, water can be added to the geothermal column 10. Low water level alarms and/or indicators can also be incorporated into the system. In certain instances either cooled or warmed water can be introduced into the geothermal column 10 for enhancing or maintaining system performance as may be required.
It may thus be seen that the present invention can eliminate direct heat transfer from the refrigerant to the ground to obtain a number of substantial advantages. Rather than dispose the transfer tubing in horizontal orientation in the earth mass, the present invention provides for vertical positioning of refrigeration lines within a volume of water, such that the water circulates by convection to transfer heat to the landmass over a large vertically extending area. Depending upon requirements, several vertical columns may be provided, each functioning in a similar manner. Land utilization is increased, and installation and servicing is less disruptive.
It will be understood that various modifications may be made to the embodiments disclosed herein. Therefore, the above description should not be construed as limiting, but merely as exemplification of the various embodiments. Those skilled in the art will envision other modifications within the scope and spirit of the claims appended hereto.

Claims

What is claimed is:

1. A geothermal column, comprising:.

at least one spirally wound refrigeration coil configured to communicate with a heat pump compressor;

a hollow tube having an outer wall of diameter substantially greater than that of said at least one spirally wound refrigeration coil and positioned so as to surround said at least one spirally wound refrigeration coil, said outer wall having a substantially rigid configuration such that said hollow tube maintains its shape; and

a support member configured to retain a shape of said at least one spirally wound refrigeration coil and maintain a centrally located position of said at least one spirally wound refrigeration coil within said hollow tube.

2. The geothermal column of claim 1 wherein the at least one spirally wound refrigeration coil is fabricated from copper tubing.

3. The geothermal column of claim 2 wherein the copper tubing has a diameter of from about ⅛ inch to about 1 inch.

4. The geothermal column of claim 1 wherein the at least one spirally wound refrigeration coil includes at least one loop oil trap in an upper portion of the refrigeration coil and a U-shaped oil trap in a lower portion of the refrigeration coil.

5. The geothermal column of claim 1 further comprising a top cap removably attached to an upper end of the hollow tube, wherein the top cap includes at least one fluid access port for providing fluid communication with the interior of the hollow tube, at least two coil access ports through which respective end portions of the at least one spirally wound refrigeration coil are disposed, and a lift support to provide an attachment for means to lift or lower the geothermal column.

6. The geothermal column of claim 1 further including a bottom cap fixedly attached to a bottom end of the hollow tube to provide a water tight seal.

7. The geothermal column of claim 1 wherein the support member comprises an axial column and at least one attachment means for securing the spirally wound refrigeration coil to the support member.

8. The geothermal column of claim 7 wherein the attachment means comprises a comb having openings through which the at least one spirally wound refrigeration coil is disposed for support.

9. The geothermal column of claim 8 further comprising at least one annular support disposed on an inner surface of the hollow tube and having an inner diameter spaced apart from ends of the radially extending fins.

10. The geothermal column of claim 1 wherein the at least one spirally wound refrigerant coil comprises two or more refrigerant coils, each having a respective inlet and outlet, each being disposed around an axial column of the support member and each having U-shaped oil trap at the lowest point in the geothermal column.

11. The geothermal column of claim 5 wherein the support member is attached to the top cap.

12. The geothermal column of claim 1 further comprising a non-antifreeze fluid disposed within the hollow tube.

13. The geothermal column of claim 16 wherein the non-antifreeze fluid is water.

14. The geothermal column of claim 1 further comprising a refrigerant fluid flowably disposed within the spirally wound refrigerant coil.

15. The geothermal column of claim 18 wherein the refrigerant fluid comprises a fluorocarbon, and optionally a lubricant oil.

16. The geothermal column of claim 15 wherein the refrigerant fluid further comprises a lubricant oil.

17. A geothermal column, comprising:

a hollow tube having an outer wall of diameter substantially greater than that of said at least one spirally wound refrigeration coil and positioned so as to surround said at least one spirally wound refrigeration coil, said outer wall being fabricated from a corrugated material; and

18. The geothermal column of claim 17 wherein the outer wall is flexible.

19. The geothermal column of claim 17 wherein the outer wall is rigid.

20. A geothermal column, comprising:

a hollow tube having an outer wall of diameter substantially greater than that of said at least one spirally wound refrigeration coil and positioned so as to surround said at least one spirally wound refrigeration coil, said outer wall being fabricated from a flexible material; and