Patent Description:
In some environments, seasonal cooling and warming cycles may have a significant impact on the stability and integrity of structures, such as buildings, roads, and storage tanks, especially when such structures are built above permafrost soil layers. In such environments, maintaining the permafrost layer at or below freezing becomes a significant concern and is vitally important to maintaining the infrastructure in a stable state. One method for maintaining the integrity permafrost soils is to employ passive or active cooling systems. Generally speaking, passive cooling systems rely on temperature difference between the air and soil to function. Such systems function without external power and only operate when air temperatures are below freezing and lower than the ground temperatures. However, during extreme variations in weather, such systems may not be able to provide sufficient capacity for ground cooling applications. In contrast, an active cooling system allows for control of the cooling cycles and yields more predictable results, but typically requires external power for operation that may not be abundantly available or easily accessible in certain environments.

Accordingly, the present inventor has determined that it would be desirable to develop a hybrid thermosiphon cooling system that combines the advantages of both passive and active cooling for improved overall performance. Briefly, the improved system would continue to cool passively when air temperatures are sufficiently low, then provide powered active cooling as needed when air temperatures rise above the passive cooling threshold. Examples of a passive-active thermosiphon configured for freezing an area of soil according to the preamble of claim <NUM> are disclosed in <CIT> and <CIT>. Each of these documents discloses a thermosiphon including an evaporator section, a condenser section, and a refrigeration or heat exchange system operable to actively cool the condenser section. Additional aspects and advantages of the present invention will be apparent from the following detailed description of example embodiments, which proceeds with reference to the accompanying drawings. It should be understood that the drawings depict only certain example embodiments and are not to be considered as limiting in nature.

With reference to the drawings, this section describes particular embodiments and their detailed construction and operation. The embodiments described herein are set forth by way of illustration only and not limitation. The described features, structures, characteristics, and methods of operation may be combined in any suitable manner in one or more embodiments. In view of the disclosure herein, those skilled in the art will recognize that the various embodiments can be practiced without one or more of the specific details or with other methods, components, materials, or the like. In other instances, well-known structures, materials, or methods of operation are not shown or not described in detail to avoid obscuring more pertinent aspects of the embodiments.

With general reference to <FIG>, the following disclosure relates generally to an improved hybrid thermosiphon system <NUM> designed to maintain permafrost levels underneath buildings or structures <NUM> with minimal energy consumption. As further described in detail below, the disclosed thermosiphon system <NUM> may increase the stability of permafrost layers by consistently maintaining the frozen soil levels in such a manner so as to minimize the impact of seasonal cooling and heating. For example, during the cooler seasons when the air temperature is below freezing, the thermosiphon system <NUM> is able to efficiently maintain the permafrost layer by using the cold air temperature to provide sufficient cooling. When the air temperature rises above freezing during the warmer months, the thermosiphon system <NUM> provides additional cooling via an active refrigeration system <NUM> to minimize thawing or degradation of the permafrost layer. As further discussed in detail below, the thermosiphon system <NUM> strives to continuously maintain the permafrost layer at a consistent level (e.g., by minimizing thawing) despite seasonal temperate changes to avoid the need to refreeze regions of the permafrost that may have thawed, thereby reducing overall power consumption during the warmer months. Additional details and advantages of the thermosiphon system <NUM> are discussed below with reference to <FIG>.

<FIG> schematically illustrates various components of a thermosiphon system <NUM> designed to maintain the active frost layer <NUM> in a frozen state to avoid potential degradation and destabilization of the foundation underneath a structure or building <NUM>. As illustrated in <FIG>, in certain environments, the structure <NUM> may be built upon rock or soil that includes a permafrost layer <NUM> and an active frost layer <NUM>. The permafrost layer <NUM> consists of rock and/or soil that remains at or below the freezing point of water such that the layer remains frozen. The active frost layer <NUM>, on the other hand, includes rock and/or soil that freezes and thaws annually due to seasonal and climate changes. Accordingly, when constructing structures in such environments, the building design and foundation must account for the repeated freezing and thawing cycles of the ground to avoid potential structural integrity issues, which may eventually lead to the structure <NUM> being unsafe or uninhabitable. The following description provides a brief overview of the components of the hybrid thermosiphon system <NUM> and their interaction with reference to <FIG>, followed by a more detailed discussion relating to the structure and function of the active cooling system <NUM>.

With reference to <FIG>, the thermosiphon system <NUM> includes a plurality of thermosiphon evaporator pipes <NUM> each installed into the ground surface layer <NUM>. The evaporator pipes <NUM> are arranged generally vertically relative to the ground surface layer <NUM> and include a lower pipe tail section <NUM> that extends below the surface layer <NUM> and into or through the active frost layer <NUM>. Each evaporator pipe <NUM> is enclosed and houses a refrigerant or cooling fluid (e.g., a gas or liquid) that runs through to the lower pipe tail section <NUM>. During the cold months when the surrounding air temperature is lower than the ground temperature, the thermosiphon system <NUM> relies on the cold environmental air to cool the refrigerant in the evaporator pipes <NUM>, which in turn extracts heat from the active frost layer <NUM> via an evaporation process. In an example operation, the refrigerant removes heat from the active frost layer <NUM> through the lower pipe tail section <NUM>, the vapors of which move upwardly through the evaporator pipe <NUM> toward a thermosiphon condenser <NUM>. Condensation occurs at the condenser <NUM>, causing the refrigerant to flow downwardly against the walls of the evaporator pipes <NUM> to continue the refrigeration cycle where the refrigerant continues drawing heat from the soil to maintain the active frost layer <NUM> in a frozen state. This refrigeration cycle continues to operate in a passive state as long as the air temperature above the ground surface layer <NUM> is cooler than the temperature of the active permafrost layer <NUM>.

During the warmer summer months when the air temperature is higher than the temperature under the soil, the thermosiphon condenser <NUM> can no longer operate passively as described above. In such instances, a supplementary form of refrigeration is required to condense the refrigerant in the vertical portion of the thermosiphon evaporator pipe <NUM> below the condenser <NUM> to maintain the active frost layer <NUM> (and to some extent, the permafrost layer <NUM>) in a frozen condition. For such conditions, the hybrid thermosiphon system <NUM> further includes a powered active cooling system <NUM>. Additional details of the active cooling system <NUM> and its components is described in further detail below with collective reference to <FIG>.

<FIG> and <FIG> collectively illustrate details of the active cooling system <NUM> and its components. With collective reference to <FIG> and <FIG>, the active cooling system <NUM> includes an insulated evaporator system <NUM> and a refrigeration system <NUM> coupled to one another. The following section begins with a description of the insulated evaporator system <NUM> and its components, followed by a discussion of the refrigeration system <NUM> and its components and a discussion relating to the interaction of the two systems <NUM>, <NUM>.

With collective reference to <FIG> and <FIG>, the insulated evaporator system <NUM> includes a durable insulated shell <NUM> that surrounds the evaporator (or heat exchanger) portion <NUM> of the active cooling system <NUM>. In some embodiments, the shell <NUM> may include two separate shell portions that are removably coupled to one another to enclose the evaporator <NUM>. The shell portions may be coupled in any one of various suitable methods. As illustrated in <FIG> and <FIG>, the evaporator <NUM> and the shell <NUM> are installed onto the thermosiphon evaporator pipe <NUM> below a position of the thermosiphon condenser <NUM> without need for modification of the thermosiphon or other existing components. As illustrated in <FIG>, a lower portion of the shell <NUM> is buried into the ground surface layer <NUM>.

Returning to <FIG>, the refrigeration system <NUM> includes a durable, weatherproof enclosure <NUM> housing the electrical and mechanical components of the active refrigeration system. With reference to <FIG>, the refrigeration system <NUM> houses a cooling fluid, such as a mixture of liquid and gas phase refrigerant, which is delivered to the evaporator <NUM> via the conduits <NUM> (e.g., flexible piping) at a sufficiently low temperature to cause condensation inside the thermosiphon condenser <NUM>, thereby allowing the thermosiphon system to continue operating in a similar fashion as the passive state described above. Briefly, heat from the thermosiphon is transferred to the evaporator <NUM>, evaporating the refrigerant, which then is returned to the refrigeration system <NUM> via the conduits <NUM>. The refrigeration system <NUM> condenses the refrigerant and releases the heat to the atmosphere through condensers <NUM> which are coupled to the refrigeration system enclosure <NUM> before returning low temperature refrigerant back to the evaporator <NUM> to continue the refrigeration cycle.

With particular reference to <FIG>, the refrigeration system <NUM> may be coupled to vertical supports <NUM> adjacent the evaporator system <NUM>. In other embodiments, the refrigeration system <NUM> may be coupled directly to the evaporator system <NUM> along the shell <NUM>. Preferably, the conduits <NUM> include self-sealing quick disconnect fittings <NUM> to connect the evaporator system <NUM> and refrigeration system <NUM>. The fittings <NUM> provide a number of advantages for the thermosiphon system <NUM>. For example, the fittings <NUM> allow the systems <NUM>, <NUM> to be easily separated from one another without the need to remove the cooling fluid. This design also simplifies transportation of the systems <NUM>, <NUM> to and from the often remote locations in which the thermosiphon system <NUM> is installed. In addition, the fittings <NUM> simplify and reduce the cost of installation by eliminating the need for a licensed refrigerant technician on-site since units can be charged with refrigerant in an urban center prior to transport. Moreover, the fittings <NUM> facilitate repair/maintenance work that may be needed for the systems <NUM>, <NUM> without requiring an on-site technician since the systems <NUM>, <NUM> may be transported individually as needed.

Returning to <FIG>, the refrigeration system <NUM> preferably includes a heater <NUM>, a cooling unit <NUM> (such as a combination cooling coil and fan), a compressor head pressure control <NUM>, and a hot gas bypass control <NUM> to facilitate reliable operation under a wide range of heat loads and environmental conditions. These components may be controlled by a process controller <NUM> and operated to maximize efficiency of the overall system.

In some embodiments, the thermosiphon system <NUM> may further include temperature and/or pressure sensors (not shown) operable to determine the temperature of the thermosiphon and the operating conditions within the refrigeration system <NUM>. When specific temperature and pressure parameters are met, the respective sensor(s) may send a signal to the process controller <NUM>. Upon receiving the signal, the compressor <NUM> may be activated and begin cooling to continue the refrigeration cycle and maintain the active frost layer <NUM> in a frozen state. In some embodiments, the process controller <NUM> may be programmed to vary the speed of the compressor <NUM> to further stabilize system operating conditions as needed.

In some embodiments, the system <NUM> may further include a variety of solar panels <NUM> used to power the refrigeration system <NUM>. For example, with reference to <FIG>, the structure <NUM> may include an array of solar panels <NUM> arranged to generate electricity throughout the year, primarily during the warmer summer months and shoulder seasons. Accordingly, during operation, the power generated by the solar panels <NUM> may be used to offset the power consumption of the active cooling system <NUM>. In other embodiments, the active cooling system <NUM> may operate via a conventional power source, such as batteries or fuel, by a combination of solar energy and a conventional power source, or any other suitable power sources.

With reference to <FIG>, it should be understood that the size of the active cooling system <NUM> components determines the rate of cooling and heat extraction within the evaporator pipes <NUM>. Preferably, the active cooling system <NUM> has sufficient capacity so as to maintain the active frost layer <NUM> sufficiently cooled to avoid thawing cycles. As illustrated in <FIG>, the system <NUM> may include a plurality of active cooling systems <NUM> operable to service a number of thermosiphon evaporator pipes <NUM>. For example, in some embodiments, each evaporator pipe <NUM> may include an active cooling system <NUM>. It should be understood that in other embodiments, any suitable number of active refrigeration systems <NUM> may be used as needed.

It should be understood that many of the features, components, and processes described herein are for illustration purposes. Accordingly, one having ordinary skill in the art may rearrange the features and process steps described herein in any of the embodiments without departing from the principles of the disclosure. In addition, it is intended that subject matter disclosed in portion herein can be combined with the subject matter of one or more of other portions herein as long as such combinations are not mutually exclusive or inoperable. In addition, many variations, enhancements and modifications of the concepts described herein are possible.

Claim 1:
A hybrid thermosiphon system (<NUM>) comprising:
a thermosiphon pipe (<NUM>) mountable along a ground surface (<NUM>), the pipe including a tail section (<NUM>) extending below the ground surface and into an active frost layer (<NUM>) when the pipe is mounted;
a condenser (<NUM>) in fluid communication with the thermosiphon pipe;
an evaporator (<NUM>) coupled to the pipe and positioned between the condenser and the ground surface; and
a refrigeration system (<NUM>) in fluid communication with the evaporator, the refrigeration system operable to cool and deliver a refrigerant to the evaporator,
wherein when an ambient air temperature is less than a threshold temperature, the thermosiphon pipe, condenser, evaporator, and refrigerant cooperate to cool the active frost layer and maintain a frozen state thereof without the refrigeration system cooling the refrigerant, and wherein when the ambient air temperature exceeds the threshold temperature, the refrigeration system cools the refrigerant prior to delivery to the evaporator,
characterised in that the hybrid thermosiphon system further comprises:
an insulated shell (<NUM>) coupled to the thermosiphon pipe and surrounding the evaporator, the insulated shell including separate shell sections removably coupled to one another to enclose the evaporator, wherein the evaporator and the insulated shell are configured to be installed onto the thermosiphon pipe below a position of the condenser without need for modification of the thermosiphon pipe.