Abstract:
Provided is a geothermal heat exchange system and method including a plurality of heat depots, each including a sealed container filled with a heat exchange fluid and further including an input heat transfer line and an output heat transfer line for carrying the heat transfer fluid. The input line proceeds through a top surface of the container at least a minimal distance into the container, and the output heat transfer line originates immediately at the upper surface of the container. Multiple heat depots connected to one another in a continuous unbroken chain are also provided.

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
       [0001]    This application claims the benefit of U.S. Provisional Patent Application Ser. No. 61/017,907, filed Dec. 31, 2007, and U.S. Provisional Patent Application Ser. No. 61/026,734, filed Feb. 7, 2008, the entire disclosures of which are hereby incorporated by reference. 
     
    
     FIELD OF THE INVENTION 
       [0002]    This invention generally relates to a system and method for geothermal heat exchange method utilizing heat depots, and, more particularly, to geothermal heat exchange utilizing heat depots having improved efficacy of heat exchange while greatly reducing required area of installation and removing the need for extensive drilling. 
       BACKGROUND OF THE INVENTION 
       [0003]    Geothermal heat exchange systems have been in use for some time. In a typical geothermal heat exchange systems, a working fluid, such as water, is used to carry heat between an internal heat exchanger in the user&#39;s location and a geothermal mass. Heat exchange systems often are designed to have both a “heating mode” and a “cooling mode”. During the heating mode, heat is transferred from a geothermal mass to the user&#39;s location, providing heat energy to the user. During cooling mode, heat is transferred from the user&#39;s location to a geothermal mass. 
         [0004]    Conventional heat pumps rely upon heat exchange between the heat pump and a geothermal mass by pumping the working fluid to the geothermal mass, where thermal energy is transferred via a primary heat exchange coil, and back to the user&#39;s structure to be heated, where an internal heat exchanger extracts the heat from this working fluid, in heating mode. The now cooled working fluid is then pumped back to the earth to be reheated through the primary heat exchange coil in contact with the geothermal mass. In cooling mode, this working fluid transfers heat from internal exchanger to geothermal mass. 
         [0005]    Direct heat exchange systems typically employ a ground coil system using a refrigerant as the working fluid and a copper ground loop as the heat exchanger. 
         [0006]    Closed loop water source heat exchange systems typically employ a closed water loop using antifreeze or water as the working fluid and a high density polyethylene glycol (HDPE) tube as the heat exchanger. 
         [0007]    Such geothermal heat exchange systems are one of the most effective ways of achieving heat exchange in heating and air conditioning systems, and especially with respect to heat pump type systems. Since the ground temperature is relatively constant at about 50° F. at a depth below the frost line, the availability of heat is also relatively constant. 
         [0008]    Generally, placing a geothermal loop heat exchange system to conduct thermal exchange in both water based heat pump and direct exchange heat pump systems incorporates several characteristics. 
         [0009]    First, thermal exchange is dependent upon total surface area of the geothermal loop tube exposed to the geothermal mass. 
         [0010]    Next, circulation of the working fluid or refrigerant requires a circulating pump or compressor. For a water based heat exchange system, a water pump circulates water constantly through the geothermal loop. For a direct heat exchange system, the heat pump compressor circulates refrigerant through the geothermal loop. Thus, due to the limitations of the circulating pump or compressor capacity, both types of systems are of limited length and diameter geothermal loop tube for conducting the heat exchange. 
         [0011]    A limited diameter geothermal loop tube restricts the available heat exchange surface area per unit length of the tube. Typical water based and direct exchange heat exchange systems use a horizontal, vertical or diagonal looping system. Horizontal looping requires extensive excavation of the geothermal mass. Thus, use of horizontal looping for a house or building with a small yard is not practical. 
         [0012]    Vertical or diagonal looping, however, requires drilling several holes to a depth of approximately 50-100 feet underneath the ground for direct exchange systems, and 200-300 feet for water source systems. And these systems also still generally require a modest size of land to install the necessary equipment. 
         [0013]    In addition, parallel horizontal looping and vertical or diagonal looping requires near equal geocontact among several loops, which requires thorough grouting during the loop installation. Unevenness of the geothermal contact or uneven geothermal heat transfer due to differences in underground soil composition, variation and contact results in a defective loop. In such a defective loop, the refrigerant or water passes underground, then through defective lines, resulting in low temperature change leading to dysfunction. In case of the direct heat exchange systems, the defective line has the lowest pressure load during the heating mode due to inability to vaporize refrigerant, and the highest pressure during the cooling mode due to lesser liquefying of the refrigerant, resulting in concentrated movement of the refrigerant through lower pressure lines due to the dysfunction. In case of the water source model, the propylene glycol, antifreeze used for heating mode use has high viscosity in lower temperature, leading to the restricted movement of the liquid movement through the defective lines. 
         [0014]    Thus, unequal flow of water or refrigerant flow results between the dysfunctional and well functioning lines due to the high viscosity or comparative lower pressure of the line, which sometimes leads to the failure of the whole system. 
         [0015]    Another problem with existing geothermal heat exchange systems is that the prolonged running time of the geothermal heat pumps often causes super freezing of the land during the heating mode and super heating of the land during the cooling mode, reducing the efficiency of the heat pump system. Indeed, many systems operate with built-in pauses, in order to allow the geothermal mass surrounding the coils to return to its usual temperature. 
         [0016]    Therefore, both types of existing systems require high cost installation due to extensive drilling, land excavation and labor requirement, as well as requiring a relatively long period of time to install. 
         [0017]    Thus, there is a need for geothermal heat exchange system and method that does not require a limited diameter and length primary heat transfer coil to increase the efficiency over conventional loop systems. 
         [0018]    There is also a need for a geothermal heat exchange system and method that does not require extensive drilling or excavation to offset the prohibitively costly installation of conventional loop systems. 
         [0019]    There is also a need for a geothermal heat exchange system and method that is not prone to pressure, viscosity, and vaporization problems with respect to the heat exchange fluid. 
         [0020]    There is also a need for a geothermal heat exchange system and method that does not cause super cooling or super heating of the geothermal mass, thus allowing the prolonged unit runtime of geothermal heat exchange if needed. 
       SUMMARY OF THE INVENTION 
       [0021]    An aspect of the present invention provides a geothermal heat exchange system and method. The system and method include use of a plurality of heat depots. A heat depot includes a sealed container filled with a heat exchange fluid, composed of a material allowing efficient heat transfer between the heat exchange fluid and a geothermal mass external to the container. Each heat depot also includes an input heat transfer line and an output heat transfer line for carrying the heat exchange fluid, the input line proceeding through a top surface of the container at least a minimal distance into the container, and the output heat transfer line originating immediately at the upper surface of the container. The heat depots are connected to one another in a continuous unbroken chain having a first heat depot and a last heat depot, such that the output heat transfer line from one depot is the input heat transfer line for another depot, with the input heat transfer line for the first depot originating at an output from a pump from a user heat exchanger, and the output heat transfer line for the last depot terminating at an input for the user heat exchanger. In an embodiment of the invention, the heat exchange depots are buried in a geothermal mass such that the top surface of the containers of the heat depots are below the frost line. The heat exchange fluid is pumped into the first heat depot through its input heat transfer line, which then overflows through its output heat transfer line which is the input heat transfer line for the next heat depot in the chain, which then overflows into the next heat depot, and so on, until the heat transfer fluid flows into the last heat depot in the chain, from which it overflows through its output heat transfer line to the user heat exchanger, and on to the pump, completing the cycle in an amount of time measured by flow rates greater than two hours. 
         [0022]    In another aspect of the invention, the geothermal heat exchange system as described here is used and the heat depots are arranged to form a horseshoe shape as viewed from above. 
         [0023]    In another aspect of the invention, the heat transfer fluid is one of a refrigerant, water with antifreeze in a closed loop, or water with antifreeze in a separate heat transfer unit. 
         [0024]    Another aspect of the invention provides a geothermal heat exchange system and method including a plurality of heat depots. Each heat depot includes a sealed container filled with a heat exchange fluid, the container composed of material(s) allowing efficient heat exchange between the heat exchange fluid and a geothermal mass external to the container. Each heat depot also includes an input heat transfer line and output heat transfer line for carrying the heat transfer fluid, the input and output heat transfer lines running from a user heat exchanger fluid output line, through a series of heat depots and to a heat depot fluid input line to transfer heat between the user heat exchanger and the heat exchange fluid. The heat depots are interconnected by heat transfer lines, such that the output heat transfer line from one depot is the input heat transfer line for another depot, the input heat transfer line for the first depot originating at an output heat transfer line from a pump from a user heat exchanger, the output heat transfer line for the last depot terminating at an input for the user heat exchanger, and the heat exchange depots being placed in effective heat transfer contact with a geothermal mass. 
         [0025]    In one aspect of the invention, the geothermal heat exchange system and method described herein uses refrigerant as the heat transfer fluid, and in heating mode, the liquid refrigerant from a user heat exchanger is split into multiple small diameter heat transfer lines to allow sufficient heat transfer, depending on the scale of the user heat exchanger. In one embodiment, the multiple heat transfer lines are bundled into one or more multiples with a length of 50-250 feet, serving as a heat transfer line passing through multiple heat depots, then merging into one vapor line serving as an input to a user heat exchanger. 
         [0026]    In another aspect of the invention, the above system and method in cooling mode, the input of the user heat exchanger is the output of the system and the output of the user heat exchanger is the input. 
         [0027]    In another aspect of the invention, the geothermal heat exchange system and method described above uses water with antifreeze in a closed loop as the heat transfer fluid, and output from a user heat exchanger is entering into the input heat transfer line of the heat depot in heating and cooling mode. In one embodiment the heat exchange fluid is circulated by water pumps after passing through a series of heat depots. 
         [0028]    In another aspect of the invention, the geothermal heat exchange system and method described above uses water with antifreeze in a separate heat transfer unit embedded in the heat depot in a size of approximately one gallon as the heat transfer fluid, and output from a user heat exchanger enters the input heat transfer line of the heat depot in heating and cooling mode. In one embodiment, the heat exchange fluid is circulated by water pumps after passing through a series of heat depots. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0029]      FIG. 1  is a schematic diagram illustrating a typical heat depot and external line installation geothermal heat exchange system, in accordance with an embodiment of the present invention; 
           [0030]      FIG. 2  is a schematic diagram illustrating a typical heat depot and indoor line installation geothermal heat exchange system, in accordance with an embodiment of the present invention; 
           [0031]      FIG. 3  is a schematic diagram illustrating heat transfer direction in an exemplary heat depot geothermal heat exchange system in active heating mode, in accordance with an embodiment of the present invention; 
           [0032]      FIG. 4  is a schematic diagram illustrating heat transfer direction in an exemplary heat depot geothermal heat exchange system in active cooling mode, in accordance with an embodiment of the present invention; 
           [0033]      FIG. 5  is a schematic diagram illustrating heat transfer direction in an exemplary heat depot geothermal heat exchange system in idle heating mode, in accordance with an embodiment of the present invention; 
           [0034]      FIG. 6  is a schematic diagram illustrating heat transfer direction in an exemplary heat depot geothermal heat exchange system in idle cooling mode, in accordance with an embodiment of the present invention; 
           [0035]      FIG. 7  is a schematic diagram illustrating a heat depot, in accordance with an embodiment of the present invention; 
           [0036]      FIG. 8  is a schematic diagram illustrating alternative heat depot configurations, in accordance with various embodiments of the present invention; 
           [0037]      FIG. 9  is a schematic diagram illustrating an in-house heat depot connection, in accordance with an embodiment of the present invention; 
           [0038]      FIG. 10  is a schematic diagram illustrating a parallel heat depot connection, in accordance with an embodiment of the present invention; 
           [0039]      FIG. 11  is a schematic diagram illustrating a diagonal heat depot connection, in accordance with an embodiment of the present invention; 
           [0040]      FIG. 12  is a schematic diagram illustrating a heat depot geothermal heat exchange system, in accordance with an embodiment of the present invention; 
           [0041]      FIG. 13  is a schematic diagram illustrating in-ground connection of heat depot(s) and heat transfer loops using refrigerant as the heat transfer liquid, in accordance with an embodiment of the present invention; 
           [0042]      FIG. 14  is a schematic diagram illustrating in-ground connection of heat depot(s) and heat transfer lines when closed loop type heat pumps are used, in accordance with an embodiment of the present invention; 
           [0043]      FIG. 15  is a schematic diagram illustrating in-ground connection of heat depot(s) and heat transfer lines using the heat transfer media, in accordance with an embodiment of the present invention; 
           [0044]      FIG. 16  is a schematic diagram illustrating a heat depot used in the and heat transfer loops connection when the heat transfer media is refrigerant, in accordance with an embodiment of the present invention; 
           [0045]      FIG. 17  is schematic diagram illustrating an embodiment of the single heat depot unit connection when the heat transfer media is water in closed water loop, in accordance with an embodiment of the present invention; 
           [0046]      FIG. 18  is schematic diagram illustrating an embodiment of the single heat depot unit connection when the heat transfer media is water in heat transfer container, in accordance with an embodiment of the present invention; and 
           [0047]      FIG. 19  is schematic diagram illustrating an embodiment of the single heat depot unit connection when the heat transfer media is heat depot material. 
       
    
    
     DETAILED DESCRIPTION 
       [0048]    In the following description, for purposes of explanation, specific numbers, materials and configurations are set forth in order to provide a thorough understanding of the invention. It will be apparent, however, to one having ordinary skill in the art, that the invention may be practiced without these specific details. In some instances, well-known features may be omitted or simplified so as not to obscure the present invention. Furthermore, reference in the specification to “one embodiment” or “an embodiment” means that a particular feature, structure or characteristic described in connection with the embodiment is included in at least one embodiment of the invention. The appearances of the phrase “in an embodiment” in various places in the specification are not necessarily all referring to the same embodiment. 
         [0049]    The present invention advantageously provides for geothermal heat exchange system and method that does not require high cost installation due to extensive drilling, land excavation, labor requirement, as well as a relatively long installation period. 
         [0050]    The present invention also provides for a geothermal heat exchange system and method that does not require a limited diameter and length primary heat transfer coil. 
         [0051]    The present invention also provides for a geothermal heat exchange system and method that does not require extensive drilling or excavation to offset the loss of efficiency of conventional loop systems. 
         [0052]    The present invention also provides for a geothermal heat exchange system and method that does not require even heat exchange among geothermal heat exchange units or loops, and that is not prone to pressure, viscosity, and vaporization problems with respect to the heat exchange fluid. 
         [0053]    The present invention also provides for a geothermal heat exchange system and method that does not cause super cooling or super heating of the geothermal mass, thus allowing for prolonged unit runtime of geothermal heat exchange. 
         [0054]    Thanks to the inventive use of heat depots, this invention greatly reduces required area of installation, removing in-depth drilling needs and saves significant cost of installation. 
         [0055]    In systems using conventional geothermal heat pumps, such as many efficient HVAC systems, the widespread practical use of the system are hindered by the high expense of installation, the need for a medium to wide area of installation, and the need for extensive drilling. The current invention advantageously provides a new heat exchange system and method eliminating these problems. 
         [0056]    Thermal exchange efficiency, also known as thermal conductivity, is dependent upon the temperature differential between donors, total area of exchange, and the heat transfer rate. As shown in the following equations of conductive heat transfer, equation (1) and convective heat transfer equation (2): 
         [0000]        q=kAdT/s 1  (1) 
         [0000]      q=kAdT  (2) 
         [0000]    Where q=heat transferred per unit time (W, Btu/hr), A=heat transfer area (m , ft ), k=thermal conductivity of the material (W/m.K or W/m.° C., Btu/(hr ° F. ft 2 /ft)) for equation (1) and k=convective heat transfer coefficient of the process (W/m 2 K or W/m 2 ° C.) for equation (2), dT=Temperature difference across the material (K or ° C., ° F.), s=material thickness (m, ft). 
         [0057]    The “heat depot” geothermal heat exchange system and method of the present invention was designed to take advantage of both conductive and convective heat exchange by providing greater area for the conductive and highly convective inner material characteristics of heat depots. Thus, the present invention provides an innovative geothermal heat exchange system and method that does not require extensive large area excavation or prohibitively expensive drilling costs, without compromising heat pump efficiency. In fact, heat pump efficiency is actually enhanced. 
         [0058]    In the present invention, the heat depot heat pump is based on the principle of providing the optimal heat exchange in the heating and cooling mode between heat depots and a geothermal mass and/or other thermal sources. An exemplary heat depot geothermal heat pump system includes one or more geothermal heat pumps, multiple heat depots, and a heat transfer unit between heat depots and geothermal heat pump(s). 
         [0059]    External loops and heat depots generally consist of one or more heat depots and parallel/serial ground heat exchange loops embodied in heat depots. 
         [0060]    Increase in Heat Exchange Surface Area 
         [0061]    The present invention utilizes heat depots to use extensive surface area to conduct heat exchange. Traditional water based loop system utilizes 0.75″, 1″ and 1.25″ loops to conduct heat exchange. Due to the small additional benefit and harder to control, increasing loop diameter to increase heat surface area is limited. Due to the limited surface area of the exchange requiring 400-500 feet of horizontal loop or 300 to 350 feet vertical loop to provide each ton of unit size. (http://www.geoflexsystems.com/tutorial.htm). 
         [0062]    Traditional DX system utilize 0.25 to 1 inch copper looping to conduct heat exchange and requiring approximately 250 ft of length in horizontal loop and over 60-100 ft in vertical loop. The increase in loop size is limited due to limited capacity of the compressor to circulate refrigerant and dead space of heat conduction in the center of the large size loop. 
         [0063]    In order to provide large surface area of the heat exchange, the current invention uses heat depot(s), approximately 2-3 ft diameter container(s) and 3-4 ft in height to conduct heat exchange not using loop system, providing more than 20-100 fold increase in surface area per unit length of the system to conduct heat exchange compared to closed loop system. 
         [0064]    Working Both in Active and Idle Mode. 
         [0065]    The total material to conduct heat exchange in traditional system per ton unit in 1.25″ loop diameter and 400 ft length is 8.6 L or 2.3 Gallon. One ton unit of the loop system requires 2-3 Gallon/min fluid flow rate, the content of the heat in the loop system could supply approximately one minute supply of the heat to the heat pump without undergoing geothermal heat exchange. The invention uses large amount of the heat exchange media 350 gallon, minimum 133 L or 35.5 gallon per heat depot and 10 heat depots per tone of the system. Thus the system could provide heat to the heat pump a minimum of 177 min or 3 hrs without undergoing geothermal heat exchange. This large amount of the heat exchange media enables heat depot to conduct heat exchange even in idle stage in preparation for the active stage to increase overall performance of the system. 
         [0066]    No Requirement of the Extensive Drilling, 
         [0067]    No need for the extensive land excavation compared to conventional geothermal heat pump system. 
         [0068]    Traditional loop system requires minimum 3 meter (10 feet) spacing between loops requiring enormous land if installed horizontally. In order to reduce land requirement two coiled loops (commonly called the “Svec Spiral” and the “Slinky”) was developed requiring less trenching than conventional straight pipe. As a result, the lower trenching costs and the savings in property disruption offsets the higher cost of coiled pipe. The ground overall mass required with straight verses the slinky pipe should be approximately the same. Care must be used when back filling a slinky type loop to ensure that pipes are spaced properly, (for example, see http://www.geoflexsystems.com/tutorial.htm). The slinky system requires a 100-foot trench, three feet wide and six feet deep in the slinky area, four feet deep in the pipe header area, using 750 to 800 feet of 0.75-inch pipe on a 17-inch pitch (http://www.alliantenergygeothermal.com/stellent2/groups/public/documents/pub/geo_wrk_des_clo — 001239.hcsp#TopOfPage) The current invention uses only 20-30 feet length (10-15 heat depots length placed adjacently) of the land for the installation of the heat depot(s), which is near equivalent land requirement for the vertical bore installation without need of the prohibitively costly drilling requirement. 
         [0069]    Providing step by step heat exchange using a cascade of the heat depots instead of the continuous well-mixed system of the traditional loop heat exchangers. 
         [0070]    The requirement of the heat exchange quantity is pending on the temperature of the heat exchange media and temperature differences between donor and recipient of the thermal energy. Heat exchange/transfer media immediately after outlet of the heat pump has highest demand of the heat exchange and its demand diminishes by passing through the seconds of the heat exchange. Traditional loop type heat exchange is well mixed system so the temperature of the heat exchange loops tends to be equalized diminishing overall efficiency. Current invention uses step by step heat transfer utilizing the heat transfer media. This step by step heat transfer causes gradual temperature differences among heat depots pending upon heat exchange needs. The first heat depot from the outlet of the heat depot has highest heat exchange demands, having lowest temperature during the heating mode and highest temperature during the cooling mode. Heat depots near the heat pump inlet maintains near nominal underground temperature still maintaining degree of temperature gradient to further increase heat exchange efficiency. 
         [0071]    Extensive internal heat reservoir capacity and hours long circulating time if used in circulating heat depot material to conduct heat exchange without causing superheating or super cooling as in the traditional loop system. 
         [0072]    Retaining over 350 gallon of the heat exchange media per ton unit has capacity to exchange required heat by changing its temperature by 4 F without conducting geothermal heat exchange. Geothermal heat pump requires 2 gallons/min water circulation by changing temperature 12 F per ton unit (12000 BTU/hr=2 Gallon/min*8.27 LB/Gallon*1 BTU/F*60 min/hr*12 F). Hence heat depot media returns original position by 175 min or 3 hr at continuous heat pump run, providing enough time to recover heat content lost or gain at heat depot. Through these, the current invention provides benefit of not causing superheating and supercooling even with exhausted run of the heat pump. Superheating and supercooling are results of exhausted run of the traditional heat pump eliminating geothermal temperature gradient, which is required for the efficient run of the geothermal heat pump system. 
         [0073]    Allowing sharing of the multiple heat exchange units by multiple heat pumps, which allows maximum efficiency when application requires both heating and cooling at the same time. 
         [0074]    Traditional closed loop geothermal heat pumps are run in a manner of one heat pump per one geothermal ground loop system. Current invention enables multiple to multiple connections of heat depot(s) unit and heat pump unit(s) like (1) one heat pump utilizes multiple sets of the heat depot units, (2) multiple heat pump utilize one set of heat depot units and (3) multiple heat pump utilize multiple sets of heat depot units. Large buildings sometimes require simultaneous run of the heating and cooling mode. In such a case, one heat requirements compensates the other needs of the heat needs possibly even eliminating the requirement of the geothermal heat exchange to maximize its efficiency. 
         [0075]    No branching requirement. Large capacity of the traditional heat pumps requires multiple loops of the heat exchanges loops. Unequal distribution of the heat exchange among these loops due to the minor geological differences would result in the concentrated heat transfer/exchange media flow causing deteriorating heat pump efficacy. The current system does not require branching to overcome these issues. 
         [0076]    The current invention link heat depots mostly in sequential mode not parallel mode having one entire sequence of the heat depots instead of the parallel arrangement of the traditional close loop systems of water source or DX. Hence the overall efficiency of the geothermal heat exchange capacity in current invention is not affected by the geological differences in heat conduction. 
         [0077]    Due to the limited heat exchange surface area per unit length loop and limited amount of the heat transfer media, traditional system requires instant heat exchange limiting prolonged running time while the current invention uses equilibrium heat exchange allowing prolonged running of the heat pump system. 
         [0078]    Traditional close loop system contains minimum volume of heat exchange media and surface area per unit length of the loops, the major heat exchange occurs during the active mode. The current invention contains extensive surface area and enormous heat capacity enable conducting geothermal heat exchange in equilibrium stage rather than instant. The ground temperature under the freezing points are around 40-60 F pending on the location. The ground temperature near by close heat exchange loops are greatly fluctuating causing superheating and supercooling pending on the length of the heat pump operation. The ground temperature near by heat depots are rather constant, so called equilibrium stage and 5-10° F. higher in cooling mode and lower in geoheating mode than nominal ground temperature, providing constant heat exchange efficiency regardless of the prolonged heat pump running time. 
         [0079]    As is evident from the above discussion, the general refrigeration cycle of a “HD” heat pump is similar to a conventional water-to-air or water-to-water heat pump or “DX” heat pump in that it includes a compressor, an expansion device, a reversing valve, and a refrigerant-to-ambient heat exchanger. The unit functions as both a heating and cooling device and also generates domestic hot water. The “HD” heat pumps differ from conventional geothermal liquid source heat pumps and “DX” in that the heat exchanger which transfers heat to and from the earth is mediated by heat depot, an heat exchange unit without utilizing long length of heat exchange pipes. 
         [0080]    Heat pumps absorbs or dissipates heat into heat depot utilizing heat transfer pipes. Heat depot exert heat exchange between external part of the unit and geothermal mass. A heat depot heat pump uses heat depots as a heat exchange mediator by
       (1) providing several tens to hundreds time of heat exchange area per unit length of the external part of the unit.   (2) heat depots serving as heat charging units in heat mode and as heat dissipating units in cooling mode even in idle mode to prepare for the active mode.   (3) No requirement of the extensive drilling,   (4) No need for the extensive land excavation compared to conventional geothermal heat pump system, and   (5) providing step by step heat exchanging using a cascade of the heat depots instead of the continuous well-mixed system of the traditional loop heat exchangers.   (6) Extensive internal heat reservoir capacity and hours long circulating time if used in circulating heat depot material to conduct heat exchange without causing superheating or super cooling as in the traditional loop system.   (7) Allowing sharing of the multiple heat exchange units by multiple heat pumps, which allows maximum efficiency when application requires both heating and cooling at the same time.   (8) No branching requirement. Large capacity of the traditional heat pumps requires multiple loops of the heat exchanges loops. Unequal distribution of the heat exchange among these loops due to the minor geological differences would result in the concentrated heat transfer/exchange media flow causing deteriorating heat pump efficiency. The current system does not require braching to overcome these issues.       
 
         [0089]    Due to the limited heat exchange surface area per unit length loops and limited amount of the heat transfer media, traditional system requires instant heat exchange limiting prolonged running time while the current invention uses equilibrium heat exchange allowing prolonged running of the heat pump system 
         [0090]      FIG. 1  illustrates an exemplary geothermal heat exchange system  100  with heat depots and external installation of the heat transfer line(s). In accordance with an embodiment of the present invention, a house  101  to be heated and/or cooled includes a heat pump  102 . The system  100  further includes one or more transfer line(s)  103  and heat depots  104  for geothermal heat exchange installed below the frost line  105 , e.g. over 3 feet under ground. Heat depots  104  conduct geothermal heat exchange when there is a temperature difference between the heat depots  104  and the surrounding geothermal mass (not explicitly depicted), regardless of whether the heat pump  102  is in active or idle stage. Heat depots  104  mediate heat exchange to or from the heat pump  102  through heat transfer line(s)  103 . 
         [0091]      FIG. 2  illustrates an exemplary heat depot and indoor line installation geothermal heat exchange system  200 . In an embodiment of the present invention, a house  101  to be heated and/or cooled includes a heat pump  102 . The system  200 , further includes placement of heat depots  104  around the perimeter  208  of the house  101 . Heat transfer lines  103 ,  206  link heat depots  104  to heat pump  102 . In arranging the heat depots  104  around the perimeter  208 , the area required to install the heat exchange system  200  is reduced. 
         [0092]      FIG. 3  illustrating heat transfer direction in an exemplary heat depot geothermal heat exchange system  300  in active heating mode. In accordance with an embodiment of the present invention, the arrows  301  indicate the general direction of heat flow into the heat pump  102  through the heat depots  104  from the surrounding geothermal mass. 
         [0093]      FIG. 4  illustrates heat transfer direction in an exemplary heat depot geothermal heat exchange system  400  in active cooling mode. In accordance with an embodiment of the present invention, the arrows  401  indicate the general direction of heat flow out of the heat pump  102  through the heat depots  104  to the surrounding geothermal mass. 
         [0094]      FIG. 5  illustrates heat transfer direction in an exemplary heat depot geothermal heat exchange system  500  in idle heating mode. In accordance with an embodiment of the present invention, the arrows  501  indicate the general direction of heat flow into the heat depots  104  from the surrounding geothermal mass when a temperature gradient exists between the heat depots  104  and the geothermal mass. 
         [0095]      FIG. 6  illustrates heat transfer direction in an exemplary heat depot geothermal heat exchange system  600  in idle cooling mode. In accordance with an embodiment of the present invention, the arrows  601  indicate the general direction of heat flow from the heat depots  104  to the surrounding geothermal mass when a temperature gradient exists between the heat depots  104  and the geothermal mass. 
         [0096]      FIG. 7  illustrates an exemplary heat depot  700 . In accordance with an embodiment of the present invention, the heat depot  700  includes an input heat transfer line  720 , entering the heat depot body  721  through an orifice  722  and exiting through an orifice  723  to an output heat transfer line  725 . 
         [0097]      FIG. 8  illustrates exemplary alternative heat depot configurations a, b, c, d, e, f and g. In accordance with various embodiments of the present invention, the heat depot  821  may take on several different configurations, including, but not limited to, those shown in  FIG. 8  as a, b, c, d, e, f and g. In each of these configurations, the heat depot  821  includes at least one input orifice  822  and at least one output orifice  823 . 
         [0098]      FIG. 9  illustrates an exemplary in-house heat depot connection  900 . In accordance with an embodiment of the present invention, the in-house heat depot connection  900  incorporates a heat depot orifice  927 , connecting heat transport line  926  through the exterior wall  928  of the house to be heated/cooled. 
         [0099]      FIG. 10  illustrates an exemplary parallel heat depot connection  1000 . In accordance with an embodiment of the present invention, heat depots  1032  are connected to the input  1030  and output  1034  of the heat pump (not depicted) through heat transfer lines  1031  and  1033 . In an embodiment of the present invention, the heat depots  1032  are arranged in a parallel configuration. 
         [0100]      FIG. 11  illustrates an exemplary diagonal heat depot connection  1100 . In accordance with an embodiment of the present invention, heat depots  1032  are connected to the input  1030  and output  1034  of the heat pump (not depicted) through heat transfer lines  1031  and  1033 . In an embodiment of the present invention, the heat depots  1032  are arranged in a perpendicular configuration. 
         [0101]      FIG. 12  illustrates an exemplary heat depot geothermal heat exchange system  1200 . In accordance with an embodiment of the present invention, the heat pump system  100  utilizes refrigerant as the heat transfer media. In an embodiment of the invention a compressor  1235  compresses refrigerant from a supply of vapor refrigerant in a liquid-vapor separator tank  1234  through a vapor line  1241 . The compressed vapor enters a solenoid tube  1236  through line  1242 . in heating mode, solenoid tube  1236  moves refrigerant vapor to an in-house heat exchanger  1237  through line  1243 . After exchange of heat, liquefied refrigerant enters refrigerant flow adjuster  1238  through line  1244 , and then enters heat depot  1239  to conduct heat exchange through line  1245 . After passing through the heat depots  1239 , vaporized refrigerant enters the compressor  1235  through line  1246  and the solenoid tube  1236 . 
         [0102]      FIG. 13  depicts an exemplary in-ground connection of heat depot(s) and heat transfer loops using refrigerant as the heat transfer liquid. Depicted are heat depots  104 , vapor refrigerant line connecting in-house heat pump  1306 , splitter of one refrigerant vapor line into multiple heat transfer refrigerant lines  1307 , bundle of the heat transfer refrigerant lines  1308 , splitter of one refrigerant liquid line into multiple heat transfer refrigerant lines  1309  and one refrigerant liquid line connecting into heat pump  1310 . The sizes of the depicted lines are dependant on the heat pump requirements. In a preferred embodiment, the recommended number of splits for 1307 and 1309 are dependant on the capacity of the heat pump. Split refrigerant lines are bundled together or separately to pass through heat depots  104  to transfer heat between heat pump and heat depots  104 . Also in a preferred embodiment, the recommended outer diameter of the heat exchange lines is about 1 inch, and the total length of the bundled heat transfer refrigerant lines is 60 to 250 feet. The length of the bundled heat transfer refrigerant lines may be changed by the heat pump and heat exchange line specifications. In general, the number of the heat depots required is 10-15 heat depots per unit ton capacity of the heat pump. If total length of the heat exchange line exceeds recommended length (e.g., 8 ton capacity), an additional heat depot field may be required. Brine solution (10-20%) may be used in heat depots for this application to avoid freezing nearby refrigerant lines. 
         [0103]      FIG. 14  depicts an exemplary in-ground connection of heat depot(s) and heat transfer lines when closed loop type heat pumps are used. Depicted are heat depots  104 , heat transfer liquid line coming from heat pump  1411 , and heat transfer liquid line returning into heat pump  1412 . Single or multiple bundled copper line(s) are recommended in a preferred embodiment to be used as the heat transfer line in order to accommodate rapid heat transfer, as well as for other reasons. In order to accommodate the required length of the heat transfer lines, lines could be curved inside heat depots or any other means of expanding surface area could be considered. The number of the heat depots  104  required may be 10-15 heat depots per unit ton capacity of the heat pump. Again, brine solution (10-20%) may be used in the heat depots  104  for this application to avoid freezing in the heat transfer lines. 
         [0104]      FIG. 15  depicts an exemplary in-ground connection of heat depot(s) and heat transfer lines (connection) using the heat transfer media. Depicted are heat depots  104 , heat pump exit liquid recipient line  1513 , heat depot connection line to pass through heat depot liquid  1514 , air relief line  1515 , air relief line inter connection line  1516  and air relief hole into the open space  1517  and liquid supply line  1518  to the heat pump. Unlike a closed loop system, the flow of the heat depot liquid is not mediated by the pressurized water pump but by the gravity difference between highest points of  1513  and  1518 . In idle stage, line  1513  may not be fully filled with liquid. In active mode, heat pump pumps liquid through line  1518  and dumps into line  1513 . The height difference between line  1513  and  1518  generates gravitational force of the heat transfer liquid flow through heat depots via inter connection line  1515 . Temporarily formed air may be removed through air relief line  1515 - 1517  via loop  1516 . Line  1517  may be placed a minimum of 1-2 feet above any of the heat depots and line  1513 . In order to accommodate unpressurized liquid flow rate, in a preferred embodiment, the recommended outer diameter of lines  1513 ,  1514  and  1518  is above one inch depending on the heating and cooling needs. The number of the heat depots required may be 10-15 heat depots per unit ton capacity of the heat pump. Brine solution (10-20%) may be used in heat depots  104  for this application to avoid freezing. 
         [0105]      FIG. 16  depicts an exemplary heat depot using heat transfer lines when the heat transfer media is refrigerant. In accordance with an embodiment of the present invention, bundled refrigerant copper tubing  19 , the main body of the heat depot  20 , a lower washer to hold copper tubing  21 , an upper washer to hold copper tubing  22 , an upper cap  23  and a lower bottom  24 , are depicted. In a preferred embodiment, the recommended diameter of the heat depot upper  23  and lower cap  24  is 2 ft or larger. Also in a preferred embodiment, the recommended height of the heat depot is 3 ft or higher. The washers  21  and  22  are preferably water tight to prevent leakage. 
         [0106]      FIG. 17  depicts an exemplary single heat depot unit connection using water as the heat transfer media in a closed loop. In accordance with an embodiment of the present invention, bundled closed loop copper/HDPE tubing  25 , the main body of the heat depot  20 , a lower washer to hold copper tubing  21 , an upper washer to hold copper tubing  22 , an upper cap  23  and a lower bottom  24 , are depicted. In a preferred embodiment, the recommended diameter of the heat depot top  23  and bottom  24  is 2 ft or larger. Also in a preferred embodiment, the recommended height of the heat depot is 3 ft or higher. The washers  21  and  22  are preferably water tight to prevent leakage. In order to provide enough heat transfer, copper/HDPE tubing may be provided with fins or rounded into multiple circle depending on the heating and cooling needs. Closed loop copper/HDPE tubing may be filled with antifreeze to prevent freezing during the heating mode. Heat transfer lines can alternatively be formed from materials other then copper/HDPE. 
         [0107]      FIG. 18  depicts an exemplary single heat depot unit connection when the heat transfer media is water in heat transfer container. In accordance with an embodiment of the present invention, the upper top of the heat depot  25 , the main body of the heat depot  20 , upper cap  23 , lower bottom  24 , heat transfer container  26 , input heat transfer line  26 - 1 , heat transfer main body  26 - 2  and output heat transfer line  26 - 3  are depicted. In a preferred embodiment, the recommended diameter of the heat depot  24  is 2 ft or larger, and the recommended height of the heat depot is 3 ft or higher. The heat transfer container should be composed of material(s) with high heat conduction potential. Preferably, the thickness (height) of the container is approximately 1-2 inch and diameter is same or less than the diameter of the heat depot. 
         [0108]      FIG. 19  depicts an exemplary single heat depot unit connection when the heat transfer media is heat depot material. In accordance with an embodiment of the present invention, reference numerals  20 ,  23 ,  24 ,  26 ,  27  represent the side, top and bottom of the heat depot, respectively. The main body of the heat depot  20 , upper cap  23 , lower bottom  24 , heat depot material transfer line  26 , and air relief line  27 , are also depicted. In a preferred embodiment, the recommended diameter of the heat depot ( 23  and  24 ) is 2 ft or larger and the recommended height of the heat depot is 3 ft or higher. In operation, as heat depot material moves from a current heat depot to a next heat depot, the current one is supplied with heat depot material from previous heat depot through transfer line  26 . Air formed during the long-time run may be relieved from the heat depot through air relief line  27 . The content of the heat depot material may be checked and supplemented as necessary. 
         [0109]    Although the invention herein has been described with reference to particular embodiments, it is to be understood that these embodiments are merely illustrative of the principles and applications of the present invention. It is therefore to be understood that numerous modifications may be made to the illustrative embodiments and that other arrangements may be devised without departing from the spirit and scope of the present invention as defined by the appended claims.