The present invention relates generally to geothermal cooling systems, and more particularly to a geothermal cooling device coupled with a superconducting heat transfer element for use as an air conditioner.
Ground source heat pump systems, also known as geothermal or geoexchange systems, have been used for cooling and heating homes for more than half a century. In 1993, the Environmental Protection Agency evaluated all commercially available technologies and concluded that ground source heat pumps were the most energy efficient systems available to the consumer.
Conventional ground source heat pump systems operate on a simple principle. In the cooling mode, heat from the building is collected at a heat exchanger and transferred to the heat pump, which concentrates the heat and transfers it to a ground source loop, which transfers the heat to the ground. In the heating mode, heat energy is absorbed from the ground and transferred to a heat pump which concentrates the heat and transfers it to the building's heat distribution system which in turn heats the building. In both modes, only a small amount of the heat energy comes from the electricity that runs the compressor; most of the energy comes from the air (in the cooling mode) and the ground (in the heating mode). This allows ground source heat pump systems to achieve more than 100% efficiency: every unit of energy consumed by the heat pump produces more than a unit of useful energy in the form of heat.
Even though ground source heat pump systems achieve efficiencies of up to 350% compared to less than 100% for most conventional systems, they have achieved a very low level of adoption in the commercial marketplace because their capital costs and installation costs have been much higher than conventional systems.
These high capital and installation costs have largely been due to fundamental inefficiencies in the ground loop subsystem. In a typical installation, the ground loop consists of hundreds or thousands of feet of looped plastic piping buried in deep trenches or deep holes drilled into the ground. An antifreeze solution such as glycol is pumped through this loop to transfer heat energy to the ground (in the cooling mode) or to absorb heat energy from the ground (in the heating mode). Few installations have sufficient available land for trenching so loops are most commonly installed in deep holes and this makes them relatively expensive for several reasons.
First, each loop consists of a supply and return line, which should fit down the same hole. With an outer diameter of an inch or more for each pipe and a tendency for these pipes to bow away from each other due to the plastic material's memory of being coiled for shipment, the hole should typically have a diameter of 4 to 6 inches to allow the loop to be installed. Holes of this size are relatively expensive to drill and require heavy equipment that disrupts landscaping, making it expensive to retrofit existing homes. Holes of this size also leave large voids around the loop that should be filled with materials such as bentonite clay in order for heat to transfer from the ground to the loop, which adds significantly to the cost of installation.
Second, having both supply and return lines in the same hole results in thermal “short circuiting” which reduces the efficiency of the loop. In the cooling mode, for example, heat absorbed by the building's cooling system is transferred to the fluid in the ground loop system and pumped down a supply line into a bore hole. As it goes down the hole it loses heat to the cool ground, causing the ground to warm up—more at the top of the hole because the fluid in the pipe is hottest as it enters the top of the hole. As the fluid goes down the tube it cools. When the cooled fluid comes back up the hole in the return line, it passes through the ground that was just heated, so the fluid in the pipe reabsorbs some of the heat it lost on the way down. This lowers the efficiency of the loop so the loop should be made longer to compensate, adding to the cost of drilling and piping.
Third, for the ground loop to function, the antifreeze solution should be pumped through hundreds or thousands of feet of small diameter piping. This consumes a significant amount of electric energy, lowering the overall efficiency of the system.
In recent years, a new ground source heat pump technology has evolved to overcome some of the inefficiencies of conventional systems. This technology, called “direct geoexchange,” replaces the conventional plastic ground loop with a small-diameter copper loop. Instead of an antifreeze solution, direct geoexchange systems pump a refrigerant through the loop to pick up heat from the ground or give off heat to the ground in the same way that conventional ground loops function.
Direct geoexchange has some significant advantages over conventional systems. First, the direct geoexchange loop runs directly to and from the heat pump's compressor, eliminating the heat exchanger that required by conventional systems to transfer heat from the loop to the heat pump. Second, the small diameter of the direct exchange loop makes it possible for loops to be installed in smaller diameter holes in the ground; this reduces the cost of drilling and backfilling the holes and reduces the size of the drill rig required to drill the holes, decreasing damage to landscaping in retrofit applications. Third, the copper pipes used in direct geoexchange transfer heat more efficiently to and from the ground so the total length of loop required is typically less than conventional systems. Because of these improvements, direct geoexchange systems can be cheaper to install than conventional ground source systems and more energy efficient.
In spite of these inherent advantages, direct geoexchange also has some significant disadvantages. First, both supply and return pipes run in the same hole, so the thermal short circuit problems of conventional systems remain. Second, the loop system pumps much more refrigerant through many more feet of piping past many more connections than conventional systems, so the potential for refrigerant leaks is increased.
Both direct geoexchange and conventional ground source heat pump systems have additional limitations that affect their usefulness. First, they are designed to heat and cool whole buildings, so neither can efficiently be installed on the incremental room-by-room basis on which most of the world—particularly the developing world—installs air conditioning. Second, they require significant amounts of electrical energy to operate pumps and compressors; this power is not often available or reliable in many parts of the world.
Most of the world either does without air conditioning (where money and electricity are in short supply), or uses refrigerant-based room air conditioners to cool individual rooms. Like geothermal systems (in the cooling mode), room air conditioners use a refrigeration circuit to absorb heat from room air and intensify it so it can be dissipated outside the building. Unlike geothermal systems, room air conditioners dissipate this heat into the outside air instead of the ground. Because air conditioning is usually used when the outside air is hot—often more than 40 degrees Fahrenheit hotter than the ground in a geothermal installation—the process of dissipating heat to the air requires air conditioners to work much harder and use much more energy than geothermal heat pumps to produce the same amount of cooling.
In spite of their high electrical power consumption, room air conditioners have dominated world markets because they are inexpensive to buy and simple to install. Rising demand for energy, however, is changing these markets. Rising demand is causing the cost of electricity to rise, making inefficient systems such as room air conditioners much less attractive to consumers. Rising demand is also causing shortages of power. Metropolitan areas such as Shanghai are finding that room air conditioners are consuming as much as two thirds of the capacity of the entire electrical grid on hot summer days, destabilizing the grid and leaving too little power for the manufacturing sector to operate during the day.
There is a need, therefore, for a cooling device that consumes significantly less power than conventional air conditioners and is cheaper to buy, easier to install and has fewer moving parts than ground source heat pump systems.
Cooling devices are provided that use a thermal superconducting transfer medium to absorb heat from a room and transfer that heat to the ground where it can be dissipated. The thermal superconducting transfer medium in these devices allows heat to move between building and ground without the assistance of a compressor or refrigeration circuit, and without the assistance of a ground loop and associated pumps, valves and circulating fluids. This reduces the power required to operate these cooling systems, and also eliminates or reduces refrigerant leaks and reduces cost and system complexity.
In one embodiment, a cooling device is suitable for coupling to a thermal superconductor geothermal ground coil extending below a ground level allowing passive thermal conduction to an earth source. The cooling device includes a thermal superconductor having a first end couplable to said thermal superconductor geothermal ground coil and a second opposing end configured as a thermal superconductor exchange segment, and a blower positioned in the region of said thermal superconducting exchange segment, and a thermostat controller associated with an indoor space and programmable to a desired temperature set point and for measuring temperature of said indoor space and further having a blower controller connected to said blower. The blower controller operates the blower in response to the difference between the set point and the measured temperature, for the purpose of operating in a cooling mode to efficiently cool an indoor space.
In another embodiment, a cooling device is operable without a thermostat and suitable for coupling to a thermal superconductor geothermal ground coil extending below a ground level allowing passive thermal conduction to an earth source. The cooling device includes a thermal superconductor having a first end couplable to said thermal superconductor geothermal ground coil and a second opposing end configured as a thermal superconductor exchange segment, and a blower positioned in the region of said thermal superconducting exchange segment, and a power connection for providing operating power to said blower when connected, and a switch connected to the power connection and the blower for controlling the blower. The blower may be manually controlled for the purpose of operating in a cooling mode to efficiently cool an indoor space.
In another embodiment, a simple cooling device not requiring a thermostat or switch is suitable for coupling to a thermal superconductor geothermal ground coil extending below a ground level allowing passive thermal conduction to an earth source and for connecting to a power source. The cooling device includes a thermal superconductor having a first end couplable to said thermal superconductor geothermal ground coil and a second opposing end configured as a thermal superconductor exchange segment, and a blower positioned in the region of said thermal superconducting exchange segment, and a power connection for providing operating power to said blower when connected. The blower may be powered by connecting the external power connector to the power source, for the purpose of operating in a cooling mode to efficiently cool an indoor space.
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With reference to the drawings, new and improved cooling devices and systems for improved cooling embodying the principles and concepts of the present invention will be described. In particular, the devices and systems are operable in the conditions where an earth source temperature is lower than an above ground temperature associated with an interior space to be cooled. The earth source may alternatively be a ground source or a body of water effectively below ground level.
Recent advances in thermal superconducting materials can now be considered for use in novel energy transfer applications. For example, U.S. Pat. No. 6,132,823 and continuations thereof, discloses an example of a heat transfer medium with extremely high thermal conductivity, and is included herein by reference. Specifically the following disclosure indicates the orders of magnitude improvement in thermal conduction; “Experimentation has shown that a steel conduit 4 with medium 6 properly disposed therein has a thermal conductivity that is generally 20,000 times higher than the thermal conductivity of silver, and can reach under laboratory conditions a thermal conductivity that is 30,000 times higher that the thermal conductivity of silver.” Such a medium is thermally superconducting. In this disclosure, the term superconductor shall interchangeably mean thermal superconductor or thermal superconductor heat pipe. The available product sold by Qu Energy International Corporation is an inorganic heat transfer medium provided in a vacuum sealed heat conducting tube.
Alternate thermal superconductors may be equivalently substituted, such as thermally superconducting heat pipes. Heat pipes typically include a sealed container(pipe), working fluid and a wicking or capillary structure inside the container. Heat is transported by an evaporation-condensation cycle when a thermal differential is present between opposing ends. Working fluids can be selected with high surface tension to generate a high capillary driving force such that the condensate can migrate back to the evaporator portion, even against gravity. Some working fluids useful for the geothermal operating temperature range include ammonia, acetone, methanol and ethanol. Inside the tube, the liquid enters and wets the internal surfaces of the capillary structure. Applying heat at one segment of the pipe, causes the liquid at that point to vaporize picking up latent heat of vaporization. The gas moves to a colder location where it condenses, giving up latent heat of vaporization. The heat transfer capacity of a heat pipe is proportional to the axial power rating, the energy moving axially along the pipe. For maximum energy transfer the heat pipe diameter should be increased and the length shortened, making it operable but less preferred than a non-liquid superconductor such as the Qu product. In particular with respect to the ground loop, scaled-up heat pipe designs have been disclosed for geothermal heating applications, such as in PCT Publication No. WO 86/00124 (“Improvements in earth heat recovery systems”). These designs partially overcome the length to diameter ratio problem but preferably require a recirculation pump for the fluid. A two-way heat pipe design for ventilation heat-exchanger is disclosed in U.S. Pat. No. 4,896,716, and could be used for non-ground loop transfer as a two-way thermal superconductor.
When suitably configured for geothermal cooling, thermal superconductors of this kind result in many significant advantages. In particular, because they transfer heat at a very high rate, they are able to absorb heat in a building, transfer it quickly and efficiently out of the building over relatively long distances of hundreds of feet with little loss of energy, and then dissipate this energy into the cool ground, without the mechanical pumping of circulating fluids required to move heat in conventional geothermal systems.
In the preferred case, the depth of hole 34 is selected in combination with the transfer properties of geothermal heat exchange element 32, the heat absorbing properties of the ground at the hole and the quantity of heat required by the system to be dissipated into the ground. As per conventional geoexchange systems, the depth of hole 34 may be greater than is practicable for a single hole, so a plurality of holes may be substituted to receive a plurality of geothermal heat exchange elements 32 and 32a with an aggregate depth equal to or greater than the required depth of a single hole. As shown in
The coupler 28 couples between the ground loop superconductor 32 and a cooling device superconductor segment 26, providing for ease of installation and conduit routing into an interior location prior to connection. The cooling device superconductor segment 26 extends inside a housing 10. Persons familiar with the technology involved here will appreciate that coupler 28 could equivalently be alternatively positioned under the ground, above ground outside a building, inside the building but outside the housing 10, or even inside the housing 10, as selected for best ease of installation. Housing 10 includes two vented regions (not shown), an inlet region to draw hot air in, and an outlet region to push cool air out. Positioned within housing 10 and between the two vented regions is a thermally superconducting air exchanger 20 connected to or integral with the cooling device superconductor segment 26, which is further insulated by insulation 25 up to the air exchanger 20, and further includes power line 36. A blower 18 is positioned in proximity to the superconducting air exchanger to pull or push air through the exchanger for cooling, the preferred position being near the outlet vent region such that air is pulled over the air exchanger 20. Due to the superior heat transfer properties of the exchanger, the fan can be a low power, low throughput fan to conserve energy, or alternatively a variable speed fan. The fan is powered by powerline 36 coupled through controller 14 to external power line 12. The preferred fan has operating noise less than 45 dB and the external power line 12 can be DC powered by an alternative energy source (not shown). Superconducting air exchanger 20 may be configured in many possible designs provided sufficient net surface area is exposed to the air flow through cooling device 110, the illustrated design of an array of bars substantially corresponding to the fan diameter is a preferred example. Blower 18 is connected to controller 14 and power line 12 for control of fan operation. In some atmospheric conditions, condensate will form on the superconductor heat exchanger 20, and an optional drip tray 22 is shown positioned below to catch condensate and an optional water drain line 24 is shown connected to drip tray for runoff disposal.
The controlled operation of the geothermal cooling device 110 provides user comfort and control of cooling. Controller 14 may be programmed as a thermostat controller responding to a temperature sensor 16 (such as a thermocouple) associated with the space to be cooled, or as a cooling device controller that receives input from a remote thermostat and sensor associated with the space (not shown). The controller is shown within the housing 10, but may alternatively be in any suitable location provided it is in communication with the blower and temperature sensor. While the simplest implementation is one temperature measurement, multiple temperature measurements could also be weighted or averaged for the purpose of feedback set points in the controller 14. In the case of a multi-speed fan, alternatively a second temperature sensor could be positioned on or near the air exchanger 20 to determine the initial fan speed for faster cooling. Unlike conventional central geothermal heat pumps, which are large, noisy and require greater power than available from a standard household outlet, the geothermal cooling device 110 can be operated from a standard outlet connected to power line 12, anywhere in the house, very quietly and in a small form factor housing. The housing 10 for geothermal cooling device 110, may be positioned anywhere within the interior room to be cooled; it does not have to be near or in a window region. Preferably the housing is positioned to provide optimum or adequate air mixing and cooling for the room.
With the controller 14 set to a desired room temperature T1 via a manual input (not shown), or a remote control input or a second remote thermostat (not shown) in communication with the controller 14, the controller senses existing room temperature T2 and if higher than T1, operates the blower 18 to circulate air until the temperature reaches T1. Alternatively, as common in the art, various thresholding or smoothing processes can be programmed to avoid jitter and to determine when to switch the blower 18 on or off. In the example of a multi-speed blower, the blower speed can be programmed to change proportional to the rate of change of existing temperature T2, in addition to on or off. The geothermal cooling device 110 can be programmed to operate for inputs that act as related proxies for associated interior temperature and that have known characterized relationships to temperature.
The geothermal cooling device 110 of
The geothermal cooling device may operate from an alternative energy power source for even more economical sustainable operation, as shown in
Alternatively, for reducing potential thermal losses through coupler 28 shown in
Due to the advantages of lightness and compactness, interior mounting can be considered for geothermal cooling devices that was previously not feasible. In
Housing 10 has inlet vents 53 underneath and outlet vents 54 at the room facing side, such that cooled air is circulated as shown by the arrows in
In the examples of geothermal cooling devices thus far, a thermostat has been used to control operation. The superconducting air exchanger can be effectively “cool” with no power and doesn't have to be “disconnected” from the ground loop. Therefore, for further parts reduction it may be desired to remove the thermostat and provide manual controls only, as shown in
In these examples and embodiments described, insulation has been shown on superconductor segments designed for low thermal loss transfer (that is, not the ends of the superconductor segments), and is the preferred example, whether or not explicitly stated in figure descriptions or numbered on drawings. However, as noted previously, the cooling device described will operate with no insulation or with some transfer lines insulated or combinations of insulated or uninsulated portions of the superconductors thereof.
In these examples housing has been described as split housing in a preferred case, however it will be appreciated that the various embodiments can be integrated into existing structures or enclosed in a single housing.
Although particular embodiments of the invention have been described by way of example, it will be appreciated that additions, modifications and alternatives thereto may be envisaged. The scope of the present disclosure includes any novel feature or combination of features disclosed therein either explicitly or implicitly or any generalization thereof irrespective of whether or not it relates to the claimed invention or mitigates any or all of the problems addressed by the present invention. The applicant hereby gives notice that new claims may be formulated to such features during the prosecution of this application or of any such further application derived therefrom. In particular, with reference to the appended claims, features from dependent claims may be combined with those of the independent claims and features from respective independent claims may be combined in any appropriate manner and not merely in the specific combinations enumerated in the claims.
Number | Date | Country | Kind |
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2,530,560 | Nov 2005 | JP | national |