US20100038052A1

US20100038052A1 - Geothermal hybrid heat exchange system

Info

Publication number: US20100038052A1
Application number: US12/504,240
Authority: US
Inventors: James R. Johnson; Jason R. Johnson
Original assignee: Individual
Current assignee: Individual
Priority date: 2008-07-16
Filing date: 2009-07-16
Publication date: 2010-02-18

Abstract

A geothermal hybrid heat exchange system is provided. The system includes a heat pump having a first fluid port and a second fluid port, a fluid reservoir, and at least one earth loop. A first end of the earth loop is connected to the first fluid port of the heat pump and the second fluid port of the heat pump and the second end of the earth loop are coupled in fluid communication with the reservoir so that fluid in the reservoir passes through the earth loop and the heat pump during heating/cooling operation of the heat pump.

Description

CROSS-REFERENCE TO RELATED APPLICATIONS

This application claims the benefit of U.S. Provisional Application No. 61/081,202, filed 16 July 2008.

FIELD OF THE INVENTION

This invention generally relates to a geothermal heat exchange system and more specifically to a hybrid heat exchange system.

BACKGROUND OF THE INVENTION

Geothermal heating/cooling systems utilize the constant temperature of the earth to provide heating in the winter and cooling in the summer. Geothermal heating/cooling systems can greatly reduce consumption of electricity, natural gas, propane, or heating oil, typically by one third or more. This reduction in carbon based energy results in a decrease in pollution and dependence on foreign oil. Though widespread experience has shown geothermal systems do save money, much of the market place has not embraced the technology. Were geothermal systems better accepted, not only would the users reap monetary benefit, but our environment and our economy would be enhanced by their use. The majority of new homes constructed could benefit from a geothermal system, but though use is increasing, significant numbers of users are lacking. This lack of use can be attributed to several factors. There is little promotion or advertising of such systems and there is very little detailed system information available, except for the geothermal heat pump itself. Manufacturers of geothermal heat pumps provide volumes of information pertinent to their equipment, but the heat pump is just one component of a system. Very little information can be found as to ground-to-line btu transfer rates, btu rates for heating versus cooling, etc. Several other major factors influence potential purchasers, such as cost, land space required, water supply, pump size requirements, and operating pressures.
There are other valid reasons many have not installed geothermal heating/cooling systems. Many property owners either cannot afford the installation cost or have property space restrictions that will not accommodate closed loop systems. Some property owners do not have adequate well water available for an open loop system, or local regulation does not allow injecting return water back down into the ground water. Other property owners are not comfortable with geothermal systems as they recognize ground source systems do have limitations and are concerned with consequences once a system has reached those limitations. To accommodate those limitations typically a secondary heating and/or cooling system is installed. Natural gas, propane, electricity, or heating oil usually powers the secondary backup system.
An open loop system is fairly simple. Water is pumped out of a ground source well at approximately 15 gallons per minute (g.p.m.), introduced into and through a heat pump where heat or cold is extracted from the water. The water then passes out of the heat pump, approximately 10 degrees colder or warmer than it was when it entered the heat pump, and is injected back into either the well it came from or into a second well or it enters some other use, such as irrigation. Some locales do not allow water to be injected back down into the ground water, possibly due to contamination issues due to the decrease or increase in temperature. The volume of water can be substantial. As an example, if the heat pump operates for 20 minutes, then 300 gallons of water must be both pumped from the ground and then disposed of. Pump operation can be expensive and, due to the high volume of water being pumped, pump maintenance can be another expense. A large percentage of properties do not have the required capability for this type system.
A closed loop system is somewhat more complicated and has a significantly higher cost. In a closed loop system the heat pump either extracts heat from within a closed loop or passes heat to the closed loop when in the cooling mode. Water (or other convenient liquid) is pumped through a ground loop, similar to a radiator, made up of high density polyethylene pipe (HDPE), which is buried in the ground. Much as air cools the water in a radiator, the constant temperature of the ground either heats or cools the water inside the closed HDPE loop. Typically, one closed loop is used for every ton capacity of the heat pump. For example, a 5 ton heat pump uses 5 closed loops and a 7 ton unit uses 7 closed loops. These multiple loops are connected to the heat pump by means of a manifold. These loops typically operate at a fairly high pressure and at a high flow volume. Both pressure and flow volume are adjusted for the individual system. When closed loops are utilized cost becomes a major factor. Space also becomes a factor as the typical individual loop requires a 3 foot wide trench for installation plus 30 inches of ground space on each side for adequate ground contact to perform the heat transfer. The average closed loop requires about 800 square foot of surface area. These loops most commonly consist of 600 foot of ¾ inch HDPE pipe installed in a 3 foot by 100 foot trench. This plastic pipe is generally installed in loops, like a Slinky toy, in such a way as each successive loop is 3 foot in diameter and overlaps the previous loop by about 18 inches. In this manner, 600 foot of pipe is installed in 100 foot of trench. A standard 5 ton system requires a surface area of approximately 4,000 square feet. A 7 ton system requires approximately 5,600 square feet. A closed loop system has a limitation in that if the water within the loop is cooled faster than the ground will heat it, then the heat pump stops generating heat. In reverse, if the water is heated by the heat pump faster than the ground will cool it, the heat pump stops providing cooling capacity. Another factor in the closed loop system is that the water is only pumped through the loops when the heat pump is operating.
A somewhat modified closed loop system is disclosed in U.S. Pat. No. 4,257,239, entitled “Earth Coil Heating and Cooling System”, issued Mar. 24, 1981. In this system the compressor and evaporator of the heat pump are separated with one acting as a compressor and the other acting as an evaporator during one mode of operation and a switch is included to reverse the operation in a second mode.
A somewhat modified closed loop system is disclosed in U.S. Pat. Nos. 2,529,154 and 2,689,090, both entitled “Heating System”, and issued Nov. 7, 1950 and Sep. 14, 1954, respectively. In this system an additional loop is included and positioned in the air or sunshine to compensate for undue ground cooling. Thus, basically a solar heater is included to compensate for periods when the ground is too cool.
It would be highly advantageous, therefore, to remedy the foregoing and other deficiencies inherent in the prior art.
Accordingly, it is an object of the present invention to provide a new and improved geothermal hybrid heating/cooling system.
Another object of the invention is to provide a new and improved geothermal hybrid heating/cooling system that is less expensive to install and to maintain.
Another object of the invention is to provide a new and improved geothermal hybrid heating/cooling system that is more efficient and requires less space.
Another object of the invention is to provide a new and improved geothermal hybrid heating/cooling system that offers increased capacity.
Another object of the invention is to provide a new and improved geothermal hybrid heating/cooling system that can be utilized to retrofit existing geothermal systems for increased capacity.
Another object of the invention is to provide a new and improved geothermal hybrid heating/cooling system that allows solar heating panels to be employed in conjunction to the closed loops.

SUMMARY OF THE INVENTION

Briefly, to achieve the desired objects of the instant invention in accordance with a preferred embodiment thereof, a novel geothermal hybrid heat exchange system is provided. The system includes a heat pump having a first fluid port and a second fluid port, a fluid reservoir, and at least one earth loop. A first end of the earth loop is connected to the first fluid port of the heat pump and the second fluid port of the heat pump and the second end of the earth loop are coupled in fluid communication with the reservoir so that fluid in the reservoir passes through the earth loop and the heat pump during heating/cooling operation of the heat pump.
In a specific embodiment of the present invention, the geothermal hybrid heat exchange system includes a heat pump, a relatively large underground fluid reservoir, and at least one earth loop. A first end of the earth loop is connected to the first fluid port of the heat pump and the second fluid port of the heat pump and the second end of the earth loop are coupled in fluid communication with the reservoir so that fluid in the reservoir passes through the earth loop and the heat pump during heating/cooling operation of the heat pump. In this embodiment the system further includes a circulating pump coupled to circulate fluid from the reservoir through the earth loop when the heat pump is not operating so that the reservoir operates like a heat sink and absorbs excess heat or cold from the fluid.
A specific method of the present invention includes the steps of providing a heat pump with a heat exchanger situated within an area to be heated/cooled and providing a relatively large underground fluid reservoir and at least one earth loop. The method then includes the steps of filling the heat pump, the earth loop, and the reservoir to capacity with a fluid and circulating the fluid from the reservoir through the heat pump and the at least one earth loop during heating/cooling operation.

BRIEF DESCRIPTION OF THE DRAWINGS

The foregoing and further and more specific objects and advantages of the instant invention will become readily apparent to those skilled in the art from the following detailed description of a preferred embodiment thereof taken in conjunction with the drawings in which:

FIG.1 illustrates a simplified schematic view of a geothermal hybrid heating/cooling system in accordance with the present invention;

FIG. 2 illustrates a simplified schematic view of another embodiment of a geothermal hybrid heating/cooling system in accordance with the present invention; and

FIG. 3 illustrates a simplified schematic view of another embodiment of a geothermal hybrid heating/cooling system in accordance with the present invention.

DETAILED DESCRIPTION OF A PREFERRED EMBODIMENT

Heat pumps, sometimes referred to as reverse cycle refrigeration units, are well known in the art. Basically, heat pumps include a compressor, an expansion valve, and two heat exchangers with one heat exchanger positioned within the enclosure to be heated/cooled and the other heat exchanger positioned outside. In the heating mode, for example, the inside heat exchanger operates as a condenser and is positioned to heat the air in the enclosure while the outside heat exchanger operates as an evaporator and is positioned to absorb heat from the low grade heat source (generally the atmosphere). In the cooling mode the system is switched so that the inside heat exchanger operates as an evaporator and is positioned to cool the air in the enclosure while the outside heat exchanger operates as a condenser and is positioned to transfer heat to the low grade cooling source
In, for example, a geothermal closed loop system the heat pump operates the same as described above but fluid circulating through the heat pump, or a portion of the heat pump, is circulated through one or more closed loops positioned to take advantage of the relatively constant temperature of the ground or earth (hereinafter an “earth loop”). It will be understood that the fluid circulating through the closed loop preferably heats or cools fluid within the heat pump itself by means of a heat exchanger but could in some specific applications actually be circulated through the heat exchangers of the heat pump as the sole driving fluid. Either or both of these configurations are included in the description of a heat pump in the following disclosure.
Turning now to FIG. 1, a simplified drawing is illustrated of a geothermal hybrid heating/cooling system 10 in accordance with the present invention. System 10 includes a heat pump 12, which may be a heat pump as described above or some modification thereof, and which includes two inlet/ outlet liquid ports 14 and 16. System 10 also includes one or more earth loops 18 having one end in fluid communication with liquid port 14 of heat pump 12. The other end of earth loops 18 is positioned in communication with a liquid 20 in a reservoir 22. As understood in the geothermal heating/cooling art, earth loops 18 are positioned in the ground in a relatively constant temperature position. Reservoir 22 will generally be a relatively large underground tank positioned to take advantage of the substantially constant temperature of the ground or earth. As an example, reservoir 22 will have a capacity many times more than the capacity of the system without the reservoir (i.e. the fluid capacity of heat pump 12 and earth loop 18). Thus, not only does the earth insulate liquid 20 in reservoir 22 from the fluctuations of the atmosphere but it also protects and maintains the temperature relatively constant.
Second liquid port 16 of heat pump 12 is connected in liquid communication with liquid 20 in reservoir 22 to complete the circuit. Thus, as liquid 20 is pumped from reservoir 22 through earth loops 18, it is returned to reservoir 22 by way of port 16 and vice versa. It will of course be understood that additional earth loops (similar to loops 18 and either in series or in parallel with loops 18) could be included in the line from reservoir 22 to port 14, if desired and convenient. Also, while reservoir 22 is described as ‘large’, it will be understood that the size will generally be determined by the size and capacity of system 10. For example, the reservoir of a two ton system might be at least twice as large as the reservoir for a one ton system.
Thus, in operation, water (or other convenient liquid) is stored generally underground in reservoir 22. Heat pump 12 is supplied with water from reservoir 22. The water is circulated through heat pump 12 and earth loops 18, which provide heating or cooling of the water, and is then returned to reservoir 22. The relatively large volume of water in reservoir 22 acts as a heat sink and absorbs any excess cold or heat from the water. The heat sink action of reservoir 22 allows excess btu transfer from heating at night (for example) to be absorbed by the water volume contained in reservoir 22 and disbursed later at off peak hours during the day. The opposite occurs when cooling is performed. The hot water is dumped into reservoir 22 and the heat is absorbed allowing it to be disbursed during off peak hours at night.
Reservoir 22 further allows water to be circulated constantly through loops 18, providing additional operating time for the ground to either heat or cool the water within loops 18. It will be understood that a lower circulating pressure or flow might be conveniently utilized during off times (i.e. non-heating/cooling operation) for heat pump 12 if desired. As an example of this structure, a control box 24 is electrically and physically attached to heat pump 12 to provide it with different circulating pressures or flows, e.g. a heating/cooling operation and a setting in which fluid is simply pumped from port 14 to port 16 or vice versa.
Referring to FIG. 2, a simplified drawing is illustrated of another embodiment of a geothermal hybrid heating/cooling system 200 in accordance with the present invention. System 200 includes a heat pump 212, which may be a heat pump as described above, or some modification thereof, and which includes two inlet/ outlet liquid ports 214 and 216. System 200 also includes one or more earth loops 218 having one end in fluid communication with liquid port 214 of heat pump 212. The other end of loops 218 is positioned in communication with a liquid 220 in a reservoir 222. In this specific example, a smaller circulating pump 224 is included in the system fluid circuit and activated when heat pump 212 is deactivated (i.e. between heating/cooling operation). By utilizing reservoir 222 and constant circulation, fewer loops 218 are required in any specific system, thereby reducing the space required and the cost.
Referring to FIG. 3, a simplified drawing is illustrated of another embodiment of a geothermal hybrid heating/cooling system 300 in accordance with the present invention. System 300 includes a heat pump 312, which may be a heat pump as described above, or some modification thereof, and which includes two inlet/ outlet liquid ports 314 and 316. System 300 also includes one or more earth loops 318 having one end in fluid communication with liquid port 314 of heat pump 312. The other end of loops 318 is positioned in communication with a liquid 320 in a reservoir 322. In this specific example, reservoir 322 also includes a water inlet 324 with a control valve 326 and a pump 328 connected to a water outlet 330. It will be understood that control valve 326 and pump 328 operate together and in conjunction with a sensor 332 in reservoir 320 or a sensor associated with heat pump 312. Alternatively, pump 224 (see FIG. 2) providing constant circulation or the pump in heat pump 312 can conveniently be connected to pump water from reservoir 322 through water outlet 330 to an external destination. If an operating temperature limit is reached (i.e. a saturation point), then hot or cold saturated water 320 is pumped out of reservoir 322 by way of water outlet 328 and reservoir 322 is refilled with fresh water by way of water inlet 324 coupled to some convenient source, such as municipal water, well water, etc. This feature overcomes the limitation factor commonly associated with a closed loop system.
Other methods of dealing with hot or cold saturated water in the reservoir are also contemplated. These methods include using auxiliary heating systems to heat the water in the reservoir if it becomes cold saturated. These auxiliary systems can include solar water heating panels which can heat water stored in the reservoir, or even gas or electric water heaters if necessary. In these instances, instead of using a pump to dump water, the water from the reservoir is run through, for example, solar heating panels and returned to the reservoir.
Thus, a new and improved geothermal hybrid heating/cooling system is disclosed. The new system overcomes many limitations commonly associated with standard closed loop systems. The new and improved geothermal hybrid heating/cooling system provides at least the following benefits: the ground space requirement is reduced by almost 50%; the cost of ground loops and installation are reduced by about 40%, overall efficiency is improved and the hybrid system provides for backup operation should the limitation point be reached, which reduces dependency on a secondary backup system.
Various changes and modifications to the embodiment herein chosen for purposes of illustration will readily occur to those skilled in the art. To the extent that such modifications and variations do not depart from the spirit of the invention, they are intended to be included within the scope thereof which is assessed only by a fair interpretation of the following claims.
Having fully described the invention in such clear and concise terms as to enable those skilled in the art to understand and practice the same, the invention claimed is:

Claims

1. A geothermal hybrid heat exchange system comprising:

a heat pump having a first fluid port and a second fluid port;

a fluid reservoir; and

at least one earth loop having first and second ends, the first end being connected to the first fluid port of the heat pump, and the second fluid port of the heat pump and the second end of the at least one earth loop coupled in fluid communication with the reservoir so that fluid in the reservoir passes through the earth loop and the heat pump during heating/cooling operation of the heat pump.

2. A geothermal hybrid heat exchange system as claimed in claim 1 wherein the reservoir is a relatively large underground tank.

3. A geothermal hybrid heat exchange system as claimed in claim 2 wherein the relatively large underground tank has a fluid capacity ten times the fluid capacity of the heat pump and the earth loop or more.

4. A geothermal hybrid heat exchange system as claimed in claim 1 further including a circulating pump coupled to circulate fluid from the reservoir through the earth loop when the heat pump is not operating.

5. A geothermal hybrid heat exchange system as claimed in claim 4 wherein the circulating pump is a component of the heat pump.

6. A geothermal hybrid heat exchange system as claimed in claim 1 wherein the reservoir further includes a fresh fluid inlet and a hot/cold saturated fluid outlet.

7. A geothermal hybrid heat exchange system as claimed in claim 6 wherein the reservoir further includes a flow of fresh fluid into the inlet of the reservoir and a flow of hot/cold saturated fluid through the fluid outlet of the reservoir controlled by a sensor and a circulating pump.

8. A geothermal hybrid heat exchange system comprising:

a heat pump having a first fluid port and a second fluid port, the heat pump including heating and cooling operations;

a relatively large underground fluid reservoir;

at least one earth loop having first and second ends, the first end being connected to the first fluid port of the heat pump, and the second fluid port of the heat pump and the second end of the at least one earth loop coupled in fluid communication with the reservoir so that fluid in the reservoir passes through the earth loop and the heat pump during heating/cooling operations of the heat pump; and

a circulating pump coupled to circulate fluid from the reservoir through the earth loop when the heat pump is not operating.

9. A geothermal hybrid heat exchange system as claimed in claim 8 wherein the circulating pump is a component of the heat pump.

10. A geothermal hybrid heat exchange system as claimed in claim 8 wherein the reservoir further includes a fresh fluid inlet and a hot/cold saturated fluid outlet.

11. A geothermal hybrid heat exchange system as claimed in claim 10 wherein the reservoir further includes a flow of fresh fluid into the inlet of the reservoir and a flow of hot/cold saturated fluid through the fluid outlet of the reservoir controlled by a sensor and a circulating pump.

12. A method of heating/cooling an area comprising the steps of:

providing a heat pump including a heat exchanger situated within the area to be heated/cooled, a relatively large underground fluid reservoir, and at least one earth loop;

filling the heat pump, the earth loop, and the reservoir to capacity with a fluid;

circulating the fluid from the reservoir through the heat pump and the at least one earth loop during heating/cooling operation.

13. A method as claimed in claim 12 including the steps of circulating the fluid from the reservoir through the heat pump and the at least one earth loop at a high rate during heating/cooling operation and circulating the fluid from the reservoir through the at least one earth loop at a lower rate during non-heating/cooling operation.

14. A method as claimed in claim 12 including a step of providing a circulating pump and connecting the circulating pump to circulate fluid from the reservoir through the earth loop, and further connecting the circulating pump to operate when the heat pump is not operating so as to utilize the reservoir as a heat sink.

15. A method as claimed in claim 12 including a step of providing a fluid inlet to the reservoir and coupling the fluid inlet to a source of fresh fluid, providing a saturated fluid outlet from the reservoir and coupling the saturated fluid outlet to a fluid disposal, and introducing fresh fluid from the fluid inlet to the reservoir and removing saturated fluid from the reservoir through the saturated fluid outlet when the fluid in the reservoir has reached a saturated state.