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(11) | EP 4 800 322 A1 |
| (12) | EUROPEAN PATENT APPLICATION |
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| (54) | DIFFUSOR FOR GENERATING STEAM IN A BOREHOLE |
| (57) Herein a diffusor (6) designed to be positioned within a borehole (4) for generating
steam comprising: - a supply pipe (2) for supplying liquid having a supply capacity, the supply pipe (2) comprising a free end (2') and a plurality of supply pipe openings (18 18') arranged at the free end; - a diffusor element (12) comprising diffusor element openings; - a protection barrel (10) designed to be arranged around the free end (2') and the diffusor element (12); - at least two pressure sensitive elements (20, 20', 20'') is disclosed. The supply pipe (2) is connected to the diffusor element (12) via the at least two pressure sensitive elements (20, 20', 20''), the supply pipe openings (18, 18') varying in size in that the size of the supply pipe openings (18, 18') are decreasing towards the free end (2'), wherein the supply pipe openings (18, 18') are designed for handling a capacity that is 3 to 6 % above the supply capacity of the supply pipe (2) and wherein the diffusor element openings are distributed over the diffusor element (12), the diffusor element openings being designed for handling a capacity that is 6% to 12% above the supply capacity of the supply pipe (2). |
Technical Field
[0001] The present disclosure relates to a diffusor designed to be used in a borehole for the generation of superheated steam to extract geothermal energy. Typically, the boreholes in which this technology is used are about 7,000m deep, which means temperatures reach about 400°C.
Background
[0002] In the realm of geothermal energy extraction, advancements have been made to enhance the efficiency and sustainability of power generation systems. Traditional geothermal power generation involves extracting natural steam and hot water from geothermal regions, which often contain impurities like sulfur that can lead to scaling and reduced plant efficiency over time. To address these challenges, systems have been developed that utilize a boiling-water geothermal heat exchanger. This system is designed to optimize heat exchange efficiency while minimizing pressure and heat loss in piping.
[0003] The core of this technology involves a water injection pipe and a steam extraction pipe, both installed underground. Water is supplied to the injection pipe, where it is heated by geothermal energy to become high-temperature pressurized water. This water is then ejected into the steam extraction pipe, where it transforms into a single-phase flow of steam due to a pressure reduction. This steam is subsequently used to drive turbines for electricity generation.
[0004] Such systems can reduce the diameter of underground pipes, thereby decreasing the amount of circulating water needed and lowering construction costs. Additionally, the system can be integrated with existing geothermal wells, enhancing the flexibility and efficiency of power generation facilities. The use of a heat insulation portion further improves such system's efficiency by minimizing heat loss in low-temperature regions near the ground surface.
[0005] Overall, these advancements in geothermal technology may offer a promising alternative to fossil fuels, providing a sustainable and efficient means of generating electricity with minimal environmental impact.
[0006] However, the described systems come with some challenges. One of them is that the water that must be expelled at the bottom of the borehole is distributed and dispersed in an efficient and controlled way so that superheated steam is generated immediately. Another challenge is the extreme conditions at the bottom of the borehole due to chemicals that might be present, high temperature and moisture. From these conditions stems the aim to have connection elements that contain as few mechanical parts as possible.
[0007] In view of the previous it is an object of this disclosure to provide a diffusor for a geothermal energy extraction system, which diffusor is efficient, reliable and robust.
Summary
[0008] Disclosed herein is a diffusor that includes a supply pipe designed for delivering liquid. This supply pipe has a defined supply capacity, which indicates the volume of liquid that can be conveyed per unit time under typical operating conditions. The supply pipe is formed with a free end, near which multiple supply pipe openings are arranged. These openings enable the passage of liquid from the supply pipe into the surrounding environment within the borehole, ultimately to be converted into steam.
[0009] A diffusor element is then placed in communication with the supply pipe. The diffusor element is provided with diffusor element openings distributed over its surface or body, thereby allowing the emerging liquid to flow in multiple directions. In some configurations, these openings are arranged to ensure that the dispersion and spreading of liquid occurs over a larger area, promoting a more immediate and efficient transition to superheated steam when the high temperatures and pressure conditions at the bottom of the borehole are present. The diffusor element itself may be sized or shaped to meet the demands of the intended borehole application. The diffusor element is further arranged within a protection barrel that is placed circumferentially around the diffusor element and the free end of the supply pipe. The protection barrel shields these components from direct external contact with the harsh ambient environment, for example stones and rocks, helping to maintain operation over time and ensuring durability.
[0010] The diffusor can be positioned within a borehole for generating superheated steam from a liquid feed in a regulated and enduring manner, while withstanding the challenging physical and chemical conditions that can be present near the bottom of such a borehole. This embodiment seeks to enable the immediate production of superheated steam through an efficient and controlled distribution of the supplied liquid, while also keeping mechanical complexity to a manageable level. By placing particular emphasis on features that handle the elevated temperature, moisture, and chemical stresses at the bottom of the borehole, this diffusor provides improved durability and reduced risk of operational failure while sufficiently generating superheated steam so that the turbine can be powered at the surface.
[0011] In one configuration, the connection between the supply pipe and the diffusor element is facilitated by mechanical means using mechanical couplings or welding. Pressure sensitive elements have been selected or devised so that they respond to the local pressure conditions within the borehole and can thereby be positioned within or around the supply pipe to regulate fluid or liquid flow. Each of these at least two pressure sensitive elements has a mode of expansion or operation that depends on the magnitude of the pressure. By employing a design that uses minimal mechanical parts-meaning that each pressure sensitive element is capable of adjusting or reacting to pressure without a complex arrangement of springs, hinges, or other moving components-the overall reliability and longevity of the diffusor is enhanced. One of the pressure sensitive elements can be arranged to expand in a particular direction below a first pressure threshold, whereas the other can be arranged to expand in that same direction or in a similar direction above a second pressure threshold. This difference in threshold-based expansion behavior can be advantageous for controlling fluid flow or structural load distribution under various high-pressure conditions within the borehole, such as during initial liquid/fluid injection or sustained steam generation processes.
[0012] The pressure sensitive elements may be designed as O-rings, which are filled with a gas or a liquid that is sensitive to pressure changes. Using such O-rings that can either be placed within the supply pipe or around the supply pipe can be used to regulate and control the fluid flow in the supply pipe. This may be achieved by using O-rings that expand into the supply pipe, thereby obstructing fluid flow, when the O-rings are arranged within the supply pipe. Alternatively this may be achieved by arranging the O-rings around the supply pipe so that the supply pipe is hugged by the O-ring and thereby the cross section that is available for the fluid or liquid in the supply pipe can be manipulated by the O-ring. Alternatively, the O-ring may have another shape, while still being a ring or the like.
[0013] The supply pipe openings in the free end region are of varying size, specifically decreasing in size towards the free end. This means that as one moves along the supply pipe towards a free end, each successive opening is dimensionally smaller than the previous one. These varying sizes have been carefully chosen to handle a capacity that is 3% to 6% above the nominal supply capacity of the pipe itself. By doing this, the system provides a margin that helps to counteract any fluctuations in the delivery rate of the feed liquid. As a result, the exiting liquid achieves a more uniform distribution, which fosters faster heat exchange and, hence, an expedited generation of superheated steam in the high-temperature environment at the bottom of the borehole.
[0014] Likewise, the diffusor element openings, which are positioned on the diffusor's surface or body, are specified to accommodate a capacity that lies in the range of 6% to 12% above the supply capacity of the supply pipe. By ensuring that the diffusor element can handle this slightly higher capacity, further assurance is provided that the transitioning liquid will disperse effectively without generating bottlenecks or localized high-pressure zones. The distribution of the diffusor element's openings also contributes to a more even spread of fluid ejection, which in turn can help promote immediate vaporization under heated conditions, and can mitigate issues like localized overheating or undesired backflow within the borehole.
[0015] In some embodiments, a protection plate is provided on the upper end (that is, in a direction opposite the borehole depth) of the diffusor element. This protection plate can be arranged in an inclined manner so that incoming fluid, stones or rocks or other debris, or other materials that might enter from the upper portion of the borehole are redirected appropriately, thereby protecting the diffusor element openings. Inclining the protection plate may further improve the protective effect and may safeguard the inlet region from microbial buildup or sediment accumulation as water or liquid cannot accumulate due to the inclination.
[0016] The diffusor element may be formed in a longitudinal, cylindrical configuration whose diameter is greater than or equal to that of the supply pipe. By adopting a cylindrical shape, it is possible to maintain a consistent cross-section for ease of manufacturing and installation. In this way, for instance, the diffusor element can be slid over or otherwise guided along the supply pipe during assembly. The geometry ensures that fluid distribution can proceed uniformly around the cylinder's circumference, assisting in stable superheated steam generation throughout the cross-section.
[0017] In one embodiment, the diffusor element extends within the borehole for a length of approximately 2 to 6 meters, and sometimes more specifically for about 3 to 5 meters. The diameter in such an embodiment might be in a range of roughly 20 centimeters to 80 centimeters, optionally 30 centimeters to 60 centimeters, and sometimes even further refined to about 30 centimeters to 50 centimeters. These dimensions have been found to provide a balanced ratio between the diffusor element's outer surface area (and thus the potential area for fluid distribution) and the volume inside a typical borehole.
[0018] In many cases, the supply pipe openings that allow the liquid to pass outward are arranged on a straight line along the longitudinal axis that aligns with the direction of the borehole. This means that each opening is oriented such that the flow emerges in a manner consistent with the primary insertion direction of the diffusor. By placing openings along a straight line, it can become simpler to control drilling or shaping processes when manufacturing the supply pipe. Additionally, alignment along the borehole's axis helps direct the flow into the diffusor element in a predictable and continuous manner, minimizing disruptions that could hamper steam formation.
[0019] It is possible for the supply pipe openings to be circular in shape, with their diameters decreasing in size as they approach the free end. Making them circular can simplify manufacturing, such as by drilling or milling these apertures. With decreasing diameters along the final section of the pipe, the system exerts fine control over the liquid ejection profile. At the portion of the pipe that is farthest from the main source, it becomes advantageous to have smaller openings, ensuring that the ejection velocity and flow rates can be balanced for stable and steady outflow across the entire region.
[0020] In between the supply pipe and its free end, respectively and the diffusor element a gyroid may be positioned. The gyroid may be fabricated from an at least partially metallic material. A gyroid is a triply periodic minimal surface that offers a continuous structure with no straight lines, yielding good distribution of stress and thermal loading. Its surface geometry can allow fluid to flow through complex pathways, potentially enhancing mixing and contact with heated surfaces in an optimally distributed manner.
[0021] Although the geometry may be implemented in different ways, one route is to produce the gyroid by three-dimensional printing methods, enabling complex internal lattices or channels that are not readily achieved using traditional metalworking techniques. By printing the gyroid in metal, the resultant structure can exhibit adequate mechanical strength while still offering flexibility in design. Moreover, the porous or labyrinthine nature of a gyroid or gyroid structure may be used to further homogenize fluid distribution and intensify the heat exchange that leads to rapid steam generation.
[0022] As mentioned, the gyroid is positioned between the free end of the supply pipe and the diffusor element, effectively acting as an intermediate region. By placing this three-dimensional structure in that location, the fluid emerging from the supply pipe can pass through the labyrinth of the gyroid, thereby diffusing further before reaching the diffusor element's openings. This embodiment can lead to more thorough mixing of the liquid and the superheated environment, and can reduce issues like concentrated bursts of water that fail to vaporize quickly, basically homogenizing the generation of superheated steam.
[0023] The high temperature, chemical species present, and environmental moisture pose challenges that are met by ensuring the diffusor is formed from robust and, in certain implementations, corrosion-resistant materials. The at least two pressure sensitive elements with minimal mechanical parts reduce breakage and maintenance concerns. The combination of supply pipe openings, diffusor element openings, optionally the gyroid and protective enclosures ensures that fluid is effectively dispersed, heated, and converted to steam without creating pressure drop problems or mechanical blockages that might otherwise hamper reliability or continuous operation.
[0024] Because boreholes vary in depth, diameter, and physical conditions such as temperature and chemistry, the features described are likely to be arranged in multiple configurations. The diffusor element can be produced as a metal cylinder, possibly with or without an internal gyroid structure. The depth-locating features of the diffusor can be chosen to fit the exact geometry of the application, and the number of diffusor element openings can be adjusted in proportion to the supply pipe's capacity. In certain versions, the supply pipe openings may be arranged in multiple lines or patterns (though a single straight line along the axis is often used) to meet specialized requirements or non-standard borehole shapes. The pressure sensitive elements can also be adapted, in terms of the first and second threshold expansions, to match specific flow regimes or injection pressures.
[0025] In addition, the protection barrel can be built with specialized coatings or selected materials to resist abrasion, corrosion, or high-temperature oxidation, so as to ensure that the diffusor remains operational over years. Likewise, the diffusor element itself can be made from suitable alloys or composites that maintain structural integrity even when subjected to temperature swings, chemical contact, and mechanical stress from fluid flow and steam generation.
[0026] In operational practice, fluid is injected through the supply pipe at a certain flow rate. Since the supply pipe openings can accommodate 3% to 6% more liquid than the nominal supply capacity, small changes or surges in flow will typically not overload the system. Then, as fluid navigates the diffusor element, the latter's openings-which can tolerate 6% to 12% above the supply capacity-offer sufficient capacity for stable dispersion and vaporization. The distribution of openings, combined with any intermediate gyroid structure, ensures that fluid is never ejected in large, localized volumes but is instead sprayed or projected in many smaller streams or droplets. This method fosters more rapid heat exchange and makes it simpler for high subsurface temperatures to induce immediate steam production. The presence of the protection barrel, especially in chemically hostile or high-impact environments, further protects the assembly, diminishing the frequency of repairs or early failure.
[0027] Ultimately, the above leads to reduced downtime and simpler maintenance, aligning with the objective of delivering a more robust, self-adapting, high-performance diffusor solution for steam generation in challenging borehole conditions.
[0028] In specific embodiments the diffusor may be designed without a diffusor element and only the gyroid to distribute the liquid. The gyroid may thereby have a volume that exceeds the free end of the supply pipe so that the free end including its openings fits into the gyroid
[0029] The diffusor may comprise a pressure sensitive element shaped as a torus or a pipe section. This shape allows for efficient integration within the diffusor structure while providing a large surface area for pressure detection.
[0030] The pressure sensitive element may comprise a shell enclosing a three-dimensional space. This shell structure creates a contained environment for the pressure-sensitive components, protecting them from external factors while allowing for controlled deformation. The shell may comprise a wall having a wall thickness. The wall thickness is an aspect that can be varied to control the sensitivity and responsiveness of the pressure sensitive element. The wall may be made of temperature resistant and elastic material. This material choice ensures that the pressure sensitive element can withstand high temperatures often present in diffusor environments while maintaining its elastic properties for pressure detection. A compressible and/or expandable, pressure-sensitive fluid may be arranged within the shell. This fluid acts as the medium through which pressure changes are detected and translated into physical deformation of the shell.
[0031] The shell may be designed to allow expansion or contraction in a first direction upon external pressure change, as seen on a cross sectional plane cut through the shell. This directional expansion or contraction provides a clear and measurable response to pressure changes.
[0032] The cross sectional plane may be parallel with the first direction. This alignment ensures that the expansion or contraction is observed in the intended direction for accurate expansion to achieve the described function of the pressure sensitive element, namely controlling fluid flow in the supply pipe.
[0033] The first direction may be determined by a wall thickness of the shell, which is chosen to be smaller than the wall thickness of the shell in other parts, at least along a partial length of the wall in the cross sectional plane. This variation in wall thickness creates a path of least resistance for deformation due to pressure changes.
[0034] At least one of the pressure sensitive elements may be designed to be arranged within the supply pipe. This placement allows for direct detection of pressure changes within the supply pipe, providing immediate and accurate pressure readings.
[0035] The partial length of the wall with a smaller thickness may be oriented parallel with the first direction. This orientation maximizes the effect of pressure changes on the deformation of the shell.
[0036] When the pressure sensitive element is designed as a pressure sensitive sealing in the form of a torus, it may provide both pressure detection and fluid flow controlling functions simultaneously.
[0037] A central axis and a center of the torus may define a toroidal plane. This plane serves as a reference for the orientation and deformation of the pressure sensitive element.
[0038] The shell may have a wall thickness that is smaller on its top and bottom periphery than a wall thickness in other areas such as an inner periphery or outer periphery. This variation in wall thickness allows for controlled expansion in the first direction parallel to the toroidal plane upon pressure change.
[0039] This design of the pressure sensitive element allows for enhanced sensitivity to pressure changes while maintaining structural integrity and a primary - or first direction of expansion or contraction depending on pressure changes. The torus or pipe section shape provides a large surface area for pressure detection, while the variation in wall thickness allows for controlled and directional deformation. The use of temperature resistant and elastic material ensures durability in high-temperature environments, and the compressible fluid within the shell provides a responsive medium for pressure detection. The ability to integrate this pressure sensitive element within the supply pipe allows for direct and immediate pressure readings or controlling of fluid flow. Furthermore, when designed as a pressure sensitive sealing, it can serve dual functions of pressure detection and sealing, potentially simplifying the overall design of the diffusor and the supply pipe. These features may contribute to improved performance and reliability of the diffusor in various applications.
[0040] In this disclosure, certain terms and technical specifications will be used, these terms are herewith explained:
Defintion of terms used herein
Supply Pipe
[0041] As used herein, a "Supply Pipe" generally refers to a conduit or channel configured to transport liquid (or another fluid) from a source into a borehole or similar environment. In this broad sense, the supply pipe is the primary means for conveying fluid into the system.
[0042] In certain embodiments, the supply pipe includes:
- free end positioned within or adjacent a bottom of the borehole;
- a plurality of supply pipe openings arranged at or near the free end, optionally sized so that the openings decrease in diameter or cross-sectional area toward the free end or the other way around increase towards the free end depending on requirements;
- the openings having a fluid capacity engineered to exceed the nominal supply capacity of the supply pipe by about 3% to 6%.
[0043] These specific features may be implemented to optimize fluid distribution and manage flow rates within the borehole. However, the scope of the "Supply Pipe" is not limited by these particular dimensions or capacities.
Diffusor element
[0044] A "Diffusor Element," as used herein, generally refers to any structure or device arranged to disperse or distribute liquid delivered by the supply pipe. Its main function is to promote even or controlled dispersion of fluid within a borehole (or equivalent environment) so that steam or superheated steam can be generated. In certain embodiments, the diffusor element may include:
- a longitudinal, hollow shape for example cylindrical with a diameter greater than or equal to that of the supply pipe;
- a series of diffusor element openings distributed over its surface, which may be dimensioned to collectively handle a capacity approximately 6% to 12% above the nominal supply capacity of the supply pipe;
- a configuration that aids in uniform liquid distribution.
[0045] Such a design can enhance or optimize the distribution, mixing and diffusion of the fluid within the borehole in particular the bottom of the borehole. Nonetheless, the "Diffusor element" can take various shapes, sizes, and capacities beyond these examples such as a rectangular shape or a cone shape.
Protection Barrel
[0046] As used herein, a "Protection Barrel" generally refers to a protective structure arranged at or around the free end of the supply pipe and/or around the diffusor element and/or the gyroid if the diffusor element is not present. It is primarily intended to safeguard internal components from external impacts, environmental conditions, or mechanical wear.
[0047] In more particular forms, the protection barrel:
- encases or surrounds the free end of the supply pipe and the diffusor element and therewith the gyroid;
- shields these components from debris, geological shifts, or other environmental factors; and
- is dimensioned or positioned to preserve the structural and functional integrity of the diffusor as a whole over time.
[0048] Although often cylindrical or tubular, the barrel's shape, size, and material can vary, provided it serves the protective function described and as long as it fits into the borehole.
Gyroid
[0049] A "Gyroid," in the context of this disclosure, broadly refers to a three-dimensional structure with a complex, periodic geometry that can be made from metallic or non-metallic materials. It is employed to strengthen, support, or augment fluid diffusion within the borehole environment.
[0050] In certain embodiments, the gyroid may:
- be positioned between the free end of the supply pipe and the diffusor element, or integrated within the diffusor element;
- be designed to replace the diffusor element;
- be at least partially metallic and optionally produced by additive manufacturing (e.g., 3D printing) techniques;
- provide enhanced structural integrity, improved fluid dispersion pathways, or specialized flow characteristics owing to its intricate geometric form.
[0051] This definition of "gyroid" encompasses a range of gyroid shapes and material compositions, as long as the structure functions to bolster or optimize the diffusion process.
Pressure Sensitive Elements
[0052] "Pressure Sensitive Elements" generally refer to devices or structures that mechanically respond to variations in pressure by changing its external shape depending on pressure. In broad terms, pressure sensitve elements are designed to change their outer form depending on pressure conditions and adjust or react when certain pressure thresholds are reached.
[0053] Combining several pressure sensitive elements that are designed to change their outer form depending on different pressure thresholds, may enable operating environments for various purposes such as connecting or disconnecting the the diffusor element or gyroid, if no diffusor element is present, from the supply pipe and regulate liquid flow in the supply pipe.
[0054] The pressure sensitive element(s) may be called pressure sensitive connection element(s) or pressure sensitive actuator(s) or pressure sensitive O-rings.
Shell
[0055] The term "shell" describes a structural component of the pressure sensitive element that encloses a three-dimensional space. It is made of temperature-resistant and elastic material, allowing it to withstand the harsh conditions typically found in geothermal environments. The shell's design includes a wall with varying thickness, which is basically determining the direction of the expansion of the element in a predetermined direction. In a broad sense, a shell can be any enclosing three-dimensional structure that provides protection and containment. In this specific application, the shell's wall thickness is strategically varied to facilitate expansion in a desired direction, enhancing the element's functionality. The shell may be made of Teflon, rubber, polymer, carbon, graphene, or Kevlar, or any combination of these materials.
Pressure-Sensitive Fluid
[0056] The term "pressure-sensitive fluid" is a compressible medium contained within the shell of the element. This fluid responds to pressure changes by compressing or expanding, thereby enabling the presssure sensitive element to perform its function. Generally, pressure-sensitive fluids can include gases or liquids that are capable of undergoing volume changes under pressure. In the context of this disclosure, the fluid could be air, natural gas, hydraulic oil or other specific oils such as lubricating oil or heavy oils or other suitable substances that provide the necessary compressibility and responsiveness to pressure variations.
Wall Thickness
[0057] "Wall thickness" refers to the measurement of the shell's wall from its inner to its outer surface, typically as seen in a cross sectional plane. This parameter is determining the direction and extent of the element's and the shell's expansion and contraction, respectively. In a broad sense, wall thickness can affect the strength, flexibility, and thermal properties of a structure. In the specific context of the element, the wall thickness is varied along different sections of the shell to control the expansion and compression direction, ensuring that the element functions effectively under pressure.
Toroidal Geometry or Torus
[0058] The term "toroidal geometry" or "torus" describes the shape of the shell, which is similar to a torus or doughnut shape. This geometry is particularly useful in applications where a circular or ring-like structure is needed, such as in seals or O-rings. Broadly, toroidal shapes are used in various engineering applications for their ability to provide uniform pressure distribution and sealing capabilities. In the claims, the toroidal geometry is specifically adapted for use in geothermal applications, where it may serve as a pressure-sensitive sealing mechanism. The term toroidal geometry used herein covers ring-shapes, pipe-section shapes, torus-shapes and doughnut-shapes and combinations thereof.
Brief Description of the Drawings
[0059] The disclosure will be described in more detail in the following, by way of example and with reference to the appended drawings, in which
- Fig. 1
- schematically illustrates a geothermal system in which a diffusor according to this disclosure may be installed;
- Fig. 2
- schematically illustrates the diffusor visible in figure 1 in more detail;
- Fig. 3
- schematically illustrates a free end of a supply pipe;
- Fig. 4a
- schematically illustrates another embodiment of a diffusor;
- Fig. 4b
- schematically illustrates an enlarged view of figure 4b;
- Fig. 5
- schematically illustrates a section of the supply pipe with a pressure sensitive element;
- Fig. 6
- schematically illustrates a perspective view of pressure sensitive element according to one embodiment;
- Fig. 7
- schematically illustrates a perspective view of pressure sensitive element according to another embodiment;
- Fig. 8
- schematically illustrates a cross-sectional view onto the embodiment according to figure 6, cut along line VIII-VIII; and
- Fig. 9
- schematically illustrates a cross-sectional view onto the embodiment according to figure 7, cut along line IX-IX.
[0060] Referring to figure 1, a geothermal system 1 is shown, the geothermal system 1 comprising a borehole 4 extending through multiple subsurface layers. A supply pipe 2 is installed within the borehole 4 to introduce a working fluid or other medium into the geothermal formation. A steam return pipe 3 is arranged to channel steam or other gaseous byproducts back to a surface facility having for example a steam turbine for energy production.
[0061] Towards the lower end of the borehole 4, a diffusor 6 is positioned near a bottom 8 of the borehole to disperse fluid in this case a liquid within the borehole 4 to use the heat, which is about 400°C to generate superheated steam. The bottom 8 of the borehole 8 marks the terminal depth where the geothermal resource is accessed for heat exchange, as mentioned. The arrangement illustrated in figure 1 thereby allows the geothermal system 1 to circulate liquid (or fluid) between the surface and subsurface in a closed system, converting geothermal energy into a usable form for electric energy generation. The system is a closed system, since the superheated steam can be condensed back to liquid, for example water, and then water can be injected back into to borehole 4 via the supply pipe.
[0062] Turning to figure 2, a diffusor 6 is illustrated that includes a protection barrel 10 and a diffusor element 12 housed within the barrel 10. The supply pipe 2 is shown adjacent to the diffusor 6 and is configured to deliver liquid at a rate of approximately 8 liters per second. The supply pipe 2 has openings, as explained in figure 3, with a capacity greater than the supply rate of the supply pipe 2 itself but lower than the capacity of the diffusor element 12.
[0063] A protection plate 14 is positioned so that it can be arranged inclined to shield the diffusor element 12 from incoming fluid or debris, while a bottom plate 16 is provided to protect the diffusor element 12 from the bottom side of the borehole (not shown in figure 2). The diffusor 6 is designed to distribute the supplied liquid efficiently via small holes arranged on its surface, thereby enabling the generation of superheated steam once the liquid has been heated by the surrounding geothermal environment. The higher capacity of the diffusor element 12, ensures that the fluid flow from the supply pipe 2 is effectively dispersed for optimal superheated steam generation without exceeding the diffusor's 6 operational limits.
[0064] The protection barrel 10 is preferrably made of resistant and strong material such as steel or chrome steel, titan or the like. The diffusor element 2 is made of a steel alloy, titan alloy or any other suitable material that can resist chemically challening environments and high heat around 400°C.
[0065] A free end 2' of the supply pipe 2 is connected to the diffusor 6 and forms part of the diffusor 6 herein. The free end 2' is attached to the diffusor element 2 by mechanical means using clamping mechanisms, form fit mechanisms, bayonet connector and/or welding.
[0066] Referring to figure 3, a free end 2' of the supply pipe 2 is shown with a plurality of openings 18, 18' arranged along its length and in a direction of the borehole 4. The openings 18, 18' are designed to become progressively smaller in the direction towards the bottom 8 of the borehole 4 so that opening 18 is smaller than opening 18', which is located further down towards the bottom 8 of the borehole 4, as depicted in figure 1. In some embodiments, the openings 18, 18' can be grouped so that each set of openings becomes smaller in a downward direction and then while each group has overall smaller openings 18, 18'; in other embodiments, the openings are sequentially reduced in size without distinct groupings.
[0067] Because the supply pipe 2 is subject to harsh geothermal conditions, it is typically fabricated from highly resistant and durable materials such as stainless steel or nickel-based alloys or heat and chemical resistant and fibre-reinforced polymers or even fibre-reinforced rubber. These materials help the supply pipe 2 maintain structural integrity under high pressures, high temperatures, and potential corrosive elements encountered in the borehole 4. Such robust construction and the strategic arrangement of the openings 18, 18' ensure reliable fluid delivery for generating superheated steam in the geothermal system. The lateral edges of the openings 18, 18' may be specifically treated to avoid clogging.
[0068] Referring first to figure 4a, a side view of the diffusor 6' is shown, whereby the diffusor 6' is inserted within the borehole 4. The supply pipe 2 extends down along the borehole 4, terminating in a free end 2' that is arranged within the diffusor 6'. The inclined protection plate 14 is arranged on top of the diffusor element 12 and the diffusor 6', respectively, positioned to protect the diffusor element 12 from direct fluid impingement or debris entering from above. The entire assembly can be housed or enclosed within a protection barrel 10, which helps maintain the structural integrity of the diffusor 6', especially under high-temperature and high-pressure geothermal conditions.
[0069] Turning to figure 4b, an enlarged portion highlights additional features within the diffusor 6'. A gyroid 22 is arranged in the space between the supply pipe 2 (and its free end 2') and the diffusor element 12. This gyroid 22 is configured to optimize liquid (or fluid) distribution and promote efficient generation of superheated steam. Shown just above the gyroid 22 are one or more pressure sensitive elements in the form of O-rings 20 and 20', which are arranged within the supply pipe 2. The pressure sensitive elements 20, 20' are arranged to to regulate the liquid flow rate depending on present pressure and pressure changes within and around the supply pipe 2. By incorporating the gyroid 22 and the pressure senstivie elements 20, 20', the flow of liquid through the diffusor element 12 is carefully controlled and diffused, improving heat exchange and steam production. It is to be noted that, even though two pressure sensitive elements 20, 20' are shown it is also possible to only employ one pressure senstive element 20 within the supply pipe 2 or to have different types (or similar types) of pressure senstive elements distributed along the length of the supply pipe 2 within the borehole 4.
[0070] It is to be noted (not shown) that the diffusor (not shown) may be designed as a gyroid only and not comprise the diffusor element but still connected to the free end 2' of the supply pipe 2 and comprising the inclined protection plate.
[0071] The gyroid 22 and the diffusor element 12 may be made of a tough and resistant material such as a titanium alloy or a chrome steel other other suitable alloy that can resist high temperatures and humidity over a long time.
[0072] Figure 5 illustrates a perspective view of a part of the supply pipe 2 and how a pressure senstive element 20" is arranged around the supply pipe 2 or the free end of the supply pipe 2'. The arrows in figure 5 illustrate how the pressure sensitive element 20" is capable to hug or constrict the supply pipe 2 or its free end 2' and therewith also an inner cross section of the supply pipe 2 or free end of the supply pipe 2' in order to control liquid or fluid flow in the supply pipe 2, depending on the present pressure in the borehole. Several such external pressure senstive elements 20" may be arranged along the supply pipe 2 and in the borehole 4 (c.f. figure 1), respectively.
[0073] It is to be noted that other shapes of pressure senstive elements may be used, especially if they are arranged within the supply pipe, as long as they can control or regulate the fluid flow in the supply pipe upon expansion or contraction. A balloon shape may for exampel be used.
[0074] Figure 1 illustrates a pressure sensitive element 2, 2a, 2b in the form of an O-ring or sealing. The pressure sensitive element 2, 2a, 2b comprises a shell 4, 4a, 4b made of a flexible and elastic material. The shell 4, 4a, 4b may also be made of a temperature resistant material. In figure 1, a plane III - III is illustrated, which indicates a cross-sectional cut through the pressure sensitive element 2, 2a, 2b and its shell 4, 4a, 4b, respectively, as indicated in figures 3a and 3b.
[0075] Figure 6 illustrates a pressure sensitive element 20, 20', 20" in the form of an O-ring or sealing. The pressure sensitive element 20, 20', 20" comprises a shell 22a made of a flexible and elastic material. The shell 22a may also be made of a temperature resistant material. In figure 6, a plane VIII - VIII is illustrated, which indicates a cross-sectional cut through the pressure sensitive element 20, 20', 20" and its shell 22a, respectively, as indicated in figure 8.
[0076] Figure 7 illustrates an embodiment of the pressure sensitive element 20, 20', 20" in the form of a sealing, which is pipe-section shaped or ring shaped. The pressure sensitive element 20, 20', 20" also comprises a shell 22b and a plane IX-IX is illustrated which indicates a cross-sectional cut through the pressure sensitive element 20, 20', 20" and the shell 22b, respectively, as indicated in figure 9.
[0077] Turning now to figure 8, a cross-sectional view of two embodiment of the sealing 20, 20', 20"or O-ring of figure 6 is illustrated. The arrows A illustrate an expansion and contraction direction based on the hereinafter described design of the sealing or O-ring. The shell 22a illustrated in figure 8 may be filled with a pressure sensitive fluid 28 or liquid, which typically expands or contracts depending on surrounding pressure.
[0078] Figure 8 illustrates a cross-sectional view of a pressure sensitive element 20, 20', 20" having a shell 22a with walls 30. The pressure sensitive element 20, 20', 20" comprises a top periphery 24a and a bottom periphery 24a'. Further, the pressure sensitive element 20, 20', 20" also comprises an inner periphery 26a' and an outer periphery 26a. As can be seen from figure 8 along a partial length L of the wall 30, at least more or less parallel with the bottom periphery 24a' and the top periphery 24a, a thickness of the wall 30 is reduced compared with the wall thickness along the inner - and outer periphery 26a', 26a. This leads to an expansion and contraction of the pressure sensitive element or sealing 20, 20', 20" along the arrows A depending on surrounding pressure changes. Studying figure 8 it also becomes clear for the skilled person that the thickness of the wall 30 that is smaller than the rest of the wall can be further varied to provide sealings, O-rings or pressure sensitive elements 20, 20', 20" that can interact with one another along various pressure ranges and/or pressure change ranges. This the reason why the reference numbers 20, 20' and 20" are used through the figures, in order to indicate the versatility and to show that each illustrated pressure sensitive element may be replaced with one that is configured slightly different.
[0079] Figure 8 further illustrates a central axis Z of the toroidal shape, torus or shell 22a, which toroidal shape 22a has a toroidal plane defined by the central axis Z. The central axis Z defines a circle and therewith defines the toroidal plane, also together with a centre of the toroidal shape 22a and shell 22a, respectively. It is to be noted that both embodiments in figures 6 to 9 of the pressure sensitive elements 20, 20', 20" have and define such central axis Z, which are similar or the same as illustrated in figure 8. However, for the sake of simplicity the central axis Z and therewith the toroidal plane is only illustrated in figure 8.
[0080] Figure 9 illustrates the embodiment of the pressure sensitive element 20, 20', 20" according to figure 7, in a cross-sectional view. The pressure sensitive element 20, 20', 20" comprises a shell 22b with a wall 30. The pressure sensitive element 20, 20', 20" comprises a top periphery 24b and a bottom periphery 24b'. Further, the pressure sensitive element 20, 20', 20" also comprises an inner periphery 26b' and an outer periphery 26b. As can be seen from figure 9 along a partial length L of the wall 30', at least more or less parallel with the top periphery 24b and the bottom periphery 24b', a thickness of the wall 30' is reduced compared with the wall thickness along or on the inner - and outer periphery 26b', 26b. This leads to an expansion and contraction of the pressure sensitive element or sealing 20, 20', 20" along the arrows A depending on surrounding pressure changes. Studying figure 9 it also becomes clear for the skilled person that the thickness of the wall 30' that is smaller than the rest of the wall can be further varied to provide sealings, O-rings or pressure sensitive elements than can interact with one another along various pressure ranges and/or pressure change ranges. Further, in figure 9 the borehole 4 (or a supply pipe for that matter) is also indicated and from the figure 9 it becomes clear that the pressure sensitive element 20, 20', 20" can regulate fluid flow within the borehole 4 or supply pipe by increasing or decreasing the cross- sectional area available for the fluid flow depending on decreasing or increasing pressure.
[0081] In general, the arrows A in figures 8 and 9 illustrate a first direction A, along which the pressure sensitive elements 20, 20', 20" can expand and contract depending on pressure changes. Further, both figures 8 and 9 also illustrate the pressure sensitive fluid 30, 30' arranged with in the shell 22a, 22b. The aspects of this disclosure have now been illustrated referring to figures 1 to 9.
1. A diffusor designed to be positioned within a borehole for generating steam comprising:
- a supply pipe for supplying liquid having a supply capacity, the supply pipe comprising a free end and a plurality of supply pipe openings arranged at the free end;
- a diffusor element comprising diffusor element openings;
- a protection barrel designed to be arranged around the free end and the diffusor element;
- at least two pressure sensitive elements;
characterized in that the supply pipe is connected to the diffusor element, the supply pipe openings varying in size in that the size of the supply pipe openings are decreasing towards the free end, wherein the supply pipe openings are designed for handling a capacity that is 3 to 6 % above the supply capacity of the supply pipe and wherein the diffusor element openings are distributed over the diffusor element, the diffusor element openings being designed for handling a capacity that is 6% to 12% above the supply capacity of the supply pipe.2. The diffusor according to claim 1, further comprising a protection plate arranged
on an upper end of the diffusor element, the protection plate being arranged in an
inclined manner.
3. The diffusor according to any of claims 1 or 2, wherein the diffusor element is of
a longitudinal and cylindrical shape and wherein its diameter is greater or equal
to that of the supply pipe.
4. The diffusor according to the previous claim, wherein the diffusor element has a length
of 2 to 6 m, preferably 3 to 5m, as measured along a direction of the borehole and
wherein a diameter of the diffusor element is between 20cm to 80cm, preferably 30cm
to 60cm and more preferably 30cm to 50cm.
5. The diffusor according to any of the preceding claims, wherein one of the at least
two pressure sensitive elements is designed to expand in a first direction below a
first pressure threshold and wherein the other of the at least two pressure sensitive
element is designed to expand in the first direction above a second pressure threshold.
6. The diffusor according to any of the preceding claims wherein the supply pipe openings
are arranged on a straight line, which aligns with a direction of the borehole and
wherein the diffusor element is connected onto the supply pipe openings.
7. The diffusor according to any of the previous claims wherein the supply pipe openings
are circular and wherein the diameter of the openings is decreasing towards the free
end.
8. The diffusor according to any of the previous claims wherein the diffusor is being
shaped as a gyroid and made of an at least partially metallic material.
9. The diffusor according to the previous claim, wherein the gyroid is produced by 3D
printing.
10. The diffusor according to any of the previous claims 8 to 9, wherein the gyroid is
arranged in between the free end of the supply pipe and the diffusor element.
11. The diffusor according to any of the previous claims, wherein the pressure sensitive
element (20, 20', 20") is shaped as a torus or a pipe section and comprises:
- a shell (22a, 22b) enclosing a three-dimensional space, the shell (22a, 22b) comprising a wall (30, 30') having a wall thickness, the wall (30, 30') being made of temperature resistant and elastic material;
- a compressible and/or expandable, pressure-sensitive fluid (28) arranged within the shell (22a, 22b);
wherein the shell (22a, 22b) is designed to allow expansion or contraction in a first direction (A) upon external pressure change, as seen on a cross sectional plane cut through the shell (22a, 22b), the cross sectional plane being parallel with the first direction (A) and wherein the first direction (A) is determined by a wall thickness of the shell (22a, 22b);, which is chosen to be smaller than the wall thickness of the shell (22a, 22b) in other parts, at least along a partial length (L) of the wall (30, 30') in the cross sectional plane.12. The diffusor according to the previous claim, wherein at least one of the pressure
sensitive elements (20, 20', 20") is designed to be arranged within the supply pipe
(2,2').
13. The diffusor according to the previous claims 11 or 12, wherein the partial length
(L) of the wall (30, 30') with a smaller thickness is oriented parallel with the first
direction (A), the pressure sensitive element (20, 20', 20") is designed as a pressure
sensitive sealing in the form of a torus.
14. The diffusor according to the previous claims 11 to 13, wherein a central axis (Z)
and a center of the torus define a toroidal plane and wherein the shell (22a, 22b)
has a wall thickness that is smaller on its top and bottom periphery (24a, 24a', 25b,
24b') than a wall thickness in other areas such as an inner periphery or outer periphery
(26a, 26a', 26b, 26b') to allow expansion in the first direction (A) parallel to the
toroidal plane upon pressure change.