Land-based aquaculture tank

Abstract

This land-based aquaculture tank comprises: an inner side wall that is formed from a material having a high thermal conductivity and stores aquaculture water on the inner side; an outer side wall that is formed from a material having a low thermal conductivity and is provided outside the inner side wall so as to surround the inner side wall at a distance, thereby providing a double structure; a warming space portion that is formed by a gap between the inner side wall and the outer side wall and is filled with air; and a heater disposed in the warming space portion. The present invention is configured such that the inner side wall is heated by heat radiation and heat conduction from the heater, and the aquaculture water stored on the inner side is heated.

Description

Land-based aquaculture tank

[0001] The present invention relates to a new type of land-based aquaculture tank that can be used in a closed recirculating aquaculture system (RAS).

[0002] The world population, which reached 5 billion in 1987, reached 6 billion in 1998, 7 billion in 2010, and is expected to reach 8 billion in 2022. This trend is expected to continue, with the world population estimated to reach 9.7 billion by 2050. This rapid population growth is changing dietary trends around the world. For example, there is a shift from a diet based primarily on agricultural and livestock production to one that includes more frequent consumption of seafood, a shift that is spreading globally. Population growth leads to increased demand in a country, which in turn drives economic growth. Furthermore, the globalization of information is leading developing countries to adopt the food cultures of developed countries. As a result, the nature of primary industries, particularly fisheries, is undergoing major changes.

[0003] In Japan, the custom of eating seafood was deeply rooted in areas close to the sea, but advances in logistics have led to the development of a seafood consumption culture in areas far from the sea as well. Furthermore, advances in refrigeration and freezing technology have made it possible to preserve food for long periods of time, and economic development has made it possible to obtain favorite foods from around the world. Due to these factors and advances in technology to improve fisheries yields, aquaculture production is showing signs of rapid growth in 2020, while wild fish catches have remained flat since the late 1980s.

[0004] Thus, in recent years, primary industries have seen a decline in wild-caught fisheries (Fishery), which are based on hunting, and the rise of agricultural aquaculture (Culture). The origins of agricultural agriculture (Agriculture) are thought to date back approximately 12,000 years, but in recent years, after this time has passed, the fishing industry has begun to shift from hunting fisheries (Fishery = Hunting) to agricultural aquaculture (Aquaculture). The history of aquaculture is much shorter than the history of agriculture, and it can be said that it is still in its infancy both globally and historically.

[0005] Compared to wild fishing, which is a hunting-based method, aquaculture, which is an agricultural method, is effective in preventing the extinction of endangered species caused by overfishing of natural resources and the destruction of ecosystems, but it also poses another problem: the possibility of environmental destruction.

[0006] Marine aquaculture, a form of aquaculture, involves raising large fish such as tuna and salmon that have grown to a certain size in an area enclosed by a net. Within this area, a single fish species exists in an overcrowded state that is not found in nature, and the fish are cultivated by adding feed and antibiotics to the enclosures. However, since this area itself is connected to the sea, the added substances are dispersed beyond the area. Furthermore, leftover feed and fish waste sink to the bottom of the water, potentially altering the environment of the area. To solve these problems, aquaculture is beginning to shift from marine to land-based farming.

[0007] Aquaculture conducted in brackish waters or lakes near river mouths is called inland aquaculture. Shrimp farming is a typical example of this type of inland aquaculture. The British Broadcasting Corporation (BBC) identified shrimp farming as the cause of 38% of mangrove forest destruction. This is because many shrimp farms clear mangrove forests to create open-cut ponds, which span enormous areas (several to hundreds of hectares). This size makes cleaning the ponds between seasons difficult, leading to continued cultivation without cleaning. This results in deterioration of water quality and frequent outbreaks of disease in farmed fish. When a farm site is deemed unusable, the neighboring area is cleared and the same cycle is repeated. It is said that tropical mangrove forests have been reduced by half over the past 30 to 40 years.

[0008] Furthermore, in this type of inland aquaculture, water is drawn in from upstream, but simply changing the location of the aquaculture from the sea to the mouth of a river results in the same problems as those encountered in marine aquaculture mentioned above: water containing administered drugs, feed residues, etc. is dispersed downstream into the sea.

[0009] In recent years, the United Nations' Sustainable Development Goals (SDGs) and other initiatives have exerted a social influence, leading to a growing trend toward environmental awareness. Given the history of aquaculture's environmental pollution and destruction, the aforementioned RAS (Recirculating Aquaculture System) is becoming a role model for aquaculture operators. In principle, RAS treats (purifies) and reuses aquaculture water without discharging it. Since the aquaculture water is not discharged from the tank area, the environmental impact is limited. Each aquaculture operator is conducting research and development to stay at the forefront of this technology, but due to its high technical difficulty, only a small number of operators have actually adopted it. One factor that makes it difficult to adopt RAS is the difficulty of disposing of feed residues dropped into the water. Feed for farmed fish, whose main ingredient is protein, is called SS (Suspended Solid) when it is suspended in water, scum when it floats as bubbles on the surface, and sludge when it settles and accumulates at the bottom. In all of these states, the majority of the content is protein, which begins with the decomposition of amino acids, followed by the conversion of ammonia nitrogen (NH ３ , N.H. ４ － ) → nitrite nitrogen (NO ２ － ) → nitrate nitrogen (NO ３ － This process (nitrogen cycle) is carried out by nitrifying bacteria, but if the amount of treatment exceeds the limit of the nitrifying bacteria present, the water may become damaged, resulting in a situation where farmed fish cannot survive due to the toxicity of ammonia nitrogen and other substances.

[0010] Another reason that RAS is difficult to adopt is the relationship between initial investment and operating costs. The land-based aquaculture tanks used in RAS are priced according to the initial investment of the operator, but running costs vary greatly depending on the quality of the equipment initially invested. If equipment exists that can reduce running costs with a low initial investment, RAS can be expected to become more widespread and expand globally.

[0011] As mentioned above, recent years have seen the dawn of full-scale aquaculture (the first stage of aquaculture (aquaculture 1.0)), and in this first stage, technological innovations have been implemented with a focus on "how to make the most of farmed fish." For example, these innovations include aeration of the aquaculture water, nitrogen circulation, and filtration to remove SS.

[0012] In the aquaculture industry, technology is important for "how to keep farmed fish alive," but it is surprisingly little known that the most important factor affecting aquaculture production volume is "water temperature control." China, the largest aquaculture producer, has traditionally used fossil fuels such as coal that it can procure domestically and from neighboring countries to provide heating energy in the winter. However, in Qingdao, Shandong Province, where the Institute of Oceanography of the Chinese Academy of Sciences is located, some aquaculture operators actually closed their operations during the extremely cold winter months, coupled with rising fossil fuel prices (around 2016).

[0013] The five major running costs associated with aquaculture - "juvenile fish costs," "feed costs," "labor costs," "utility costs," and "harvesting, packaging, and logistics costs" - vary depending on the fish being farmed, but in order to reduce "utility costs," many aquaculture operators choose locations where they can obtain water (seawater or freshwater) at the appropriate temperature, and where that temperature range is suitable for the farmed fish. These "utility costs" can be avoided by selecting the aquaculture location, but in other words, they can be said to determine the aquaculture location.

[0014] In this way, farming locations have been specified depending on the type of farmed fish, with some types being farmed in warm locations and others in cold locations, but in an age where dietary habits are globalized and logistics reach every corner of the world, it will be easier than ever for seafood to reach from production areas to consumption areas, but at the same time, with reports of fossil fuel depletion, local production for local consumption will likely be encouraged on a global scale. This means that what will be required of the aquaculture industry in the future is to produce farmed fish in any location, rather than in a location that is dependent on climatic conditions, and to respond to the diversifying dietary habits of consumers around the world.

[0015] In other words, the future aquaculture industry is expected to move from the first stage (aquaculture 1.0), when aquaculture began in earnest, to the second stage (aquaculture 2.0), when technology is developed that allows the selection of fish species to be farmed regardless of the farming location, and this technology will become widespread worldwide.

[0016] However, there have been few technical proposals for land-based aquaculture systems or land-based aquaculture tanks that can be used appropriately in this second phase of aquaculture. For example, Patent Document 1 discloses an assembled land-based aquaculture system with a denitrification function that is easy to install and allows for portable installation, and that includes a ring-shaped tank framework made by connecting multiple sturdy outer panels, a discharge tower for circulating water that is installed in the center of the tank inside the outer panels, a waterproof sheet that seals the tank as a whole, an oxidizing radical bubble generator, an adsorption decomposition tower tank, and a water purification filtration tower tank.

[0017] Japanese Patent Application Laid-Open No. 2022-171514

[0018] According to the land-based aquaculture system described in Patent Document 1, the aquaculture tanks can be installed easily and at low cost, and can be relocated, but no proposal is made regarding a configuration for maintaining the water temperature in the tanks at an appropriate value, which is required in the second stage of aquaculture.

[0019] Therefore, the present invention solves the above-mentioned problems of the prior art, and its object is to provide an on-land aquaculture tank that can thermally efficiently maintain the water temperature inside the tank at a temperature suitable for cultured fish.

[0020] According to the present invention, the land-based aquaculture tank comprises an inner side wall made of a material with high thermal conductivity and containing aquaculture water therein, an outer side wall made of a material with low thermal conductivity and provided outside the inner side wall so as to surround it at a distance so as to form a double structure, a heating space formed by the gap between the inner side wall and the outer side wall and filled with air, and a heater disposed within the heating space. The inner side wall is heated by thermal radiation and thermal conduction from the heater, and the aquaculture water contained inside is heated.

[0021] As described above, the land-based aquaculture tank of the present invention has a double-wall structure, and a heating space formed by the gap between the inner and outer side walls is filled with air. The inner side wall, made of a highly thermally conductive material, is heated by heat radiation and conduction from a heater disposed within the air-filled heating space, thereby heating the aquaculture water contained therein. The heater within the air-filled heating space is driven to heat the inner side wall by heat radiation (electromagnetic radiation) and heat conduction, thereby heating the inner side wall very efficiently. That is, the air and the inner side wall within the heating space are heated by heat conduction from the heater. Furthermore, since the heating space is filled with air, the inner side wall is heated energy-efficiently by heat radiation through the air. Of course, the inner side wall is also heated by thermal convection of the air within the heating space. In this way, the present invention effectively utilizes all of the thermal engineering concepts of "thermal conduction," "thermal radiation," and "thermal convection" to heat the inner side wall, which is made of a material with high thermal conductivity, and thereby heats the aquaculture water contained inside with good thermal efficiency.

[0022] It is preferable that the system further includes a bubble release mechanism that releases, as bubbles, air heated by the air in the heating space as it passes through the heating space into the culture water. For the same volume of water, the contact area between bubbles in water filled with small bubbles is much larger than in water filled with larger bubbles. This increase in contact area significantly increases the area for heat conduction. Since the heat transfer coefficient (Q) is proportional to the product of the heat transfer coefficient (h) and the surface area (A) where heat transfer occurs, the heat transfer coefficient (Q) increases proportionally as the surface area (A) where heat transfer occurs increases. If heated air is released into the culture water as bubbles, the surface area where heat transfer occurs increases dramatically, allowing for very efficient transfer of thermal energy to the culture water. For example, in a 20 m ３When millibubbles are released into the culture water (1 m high in a tank with a diameter of 5 m), the surface area (A) through which heat transfer occurs is a very large value of A = 480 ha. In this way, the air in the heating space between the inner and outer side walls is heated by the heater, and as it passes through the heating space, the air heated by this heated air is released into the culture water as bubbles, so the culture water is heated very efficiently.

[0023] In this case, it is more preferable that the bubble release mechanism is a mechanism that releases air heated by the air in the heating space as fine bubbles. If heated air is released into the culture water as fine bubbles, the surface area where heat transfer occurs becomes astronomically large, so that thermal energy can be transferred to the culture water extremely efficiently. For example, if the air is released into the culture water as fine bubbles, the surface area where heat transfer occurs becomes astronomically large, so that the surface area where heat transfer occurs becomes astronomically large, so that thermal energy can be transferred to the culture water extremely efficiently. ３ When fine bubbles are released into the culture water, the surface area (A) through which heat transfer occurs is an extremely large value of A = 480 ha x 1000.

[0024] It is also preferable that the heating system further comprises at least one fan provided in the heating space for circulating the air in the heating space, so that the air in the heating space is uniformly heated.

[0025] It is also preferable to further provide a lid member made of a material with low thermal conductivity that seals the top surface of the heating space. By sealing the top surface with a lid member made of a material with low thermal conductivity and insulating properties, the heating space is insulated except for the inner side wall. The inner side wall does not need to be insulated because the culture water is contained inside. As described below, if the top surface of the culture water is insulated with an insulating sheet, the area surrounding the heating space is almost completely insulated, greatly improving the heat retention of the heating space and resulting in extremely high thermal efficiency.

[0026] In this case, it is more preferable that the cover member has at least one through-hole, and the air bubble releasing mechanism is configured to send air into the culture water through the at least one through-hole and release it as bubbles. By providing the cover member with at least one through-hole, it is not necessary to provide through-holes in the inner side wall or the outer side wall for an air passage for the air bubble releasing mechanism.

[0027] It is also preferable to further provide a heat insulating member made of a material with low thermal conductivity that covers the upper surface of the culture water. Since the upper surface of the culture water is insulated by the heat insulating sheet and its sides are insulated by the outer side wall, the culture water is insulated all around and has very high heat retention.

[0028] It is also preferable to further provide a bottom wall that covers the entire bottom surface inside the outer side wall and is made of a material that has low thermal conductivity and is waterproof. By covering the entire bottom surface with such a bottom wall that has insulating and waterproof properties, the culture water is insulated above, below, and around the periphery, resulting in extremely high heat retention.

[0029] It is also preferable to further include a temperature sensor that detects the temperature of the culture water, and a control device that controls the operation of the heater in accordance with the temperature detected by the temperature sensor to adjust the temperature of the culture water within a desired range. By detecting the temperature of the culture water with the temperature sensor and controlling the heater on / off or strength in accordance with the temperature, the temperature of the culture water can be adjusted within a desired range.

[0030] It is also preferable that the inner side wall is formed using naval brass plate. Naval brass has very high thermal conductivity, making it ideal for the inner side wall for heat conduction. Naval brass also has high strength and seawater resistance, making it resistant to corrosion by seawater.

[0031] It is also preferable that the outer side wall is formed using a brick wall or mortar wall, which has very low thermal conductivity and is therefore ideal for the outer side wall to provide thermal insulation.

[0032] It is also preferred that the outer side walls be formed using Styrofoam® material, which has very low thermal conductivity and is therefore ideal for the outer side walls to provide thermal insulation.

[0033] It is also preferable that the outer side wall is formed using an iron plate coated with a mortar fireproof material or a Galvalume steel plate coated with a mortar fireproof material. The iron plate coated with a mortar fireproof material or the Galvalume steel plate coated with a mortar fireproof material has very low thermal conductivity and is therefore ideal for the outer side wall for thermal insulation.

[0034] According to the present invention, the heater in the heating space filled with air is driven to heat the inner side wall by thermal radiation and thermal conduction, thereby heating the inner side wall very efficiently. That is, the air in the heating space and the inner side wall are heated by thermal conduction from the heater. Furthermore, since the heating space is filled with air, the inner side wall is heated with high energy efficiency by thermal radiation through the air. Of course, the inner side wall is also heated by thermal convection of the air in the heating space. In this way, by effectively utilizing "thermal conduction," "thermal radiation," and "thermal convection," the inner side wall, made of a material with high thermal conductivity, is heated, thereby heating the aquaculture water contained therein with high thermal efficiency.

[0035] 1 is a perspective view schematically showing the overall configuration of an onshore aquaculture tank according to a first embodiment of the present invention. It is a cross-sectional view taken along line A-A in FIG. 1 , schematically showing the overall configuration of an onshore aquaculture tank according to the first embodiment. It is a partially cutaway perspective view schematically showing a partial configuration of an outer side wall, an inner side wall, and a cover member according to the first embodiment. It is an explanatory diagram schematically showing the configuration of an air bubble release mechanism according to the first embodiment. It is a partially cutaway perspective view schematically showing the configuration of an example of a cover member according to the first embodiment. It is a partially cutaway perspective view schematically showing the configuration of another example of a cover member according to the first embodiment. It is a perspective view schematically showing the overall configuration of an onshore aquaculture tank according to a second embodiment of the present invention. It is a cross-sectional view taken along line B-B in FIG. 7 , schematically showing the overall configuration of an onshore aquaculture tank according to a second embodiment. It is a cross-sectional view, similar to FIG. 8 , schematically showing the overall configuration of an onshore aquaculture tank according to a modified version of the second embodiment. It is a plan view and a front view of an upper fixing bracket and a lower fixing bracket according to the modified version of FIG. It is a perspective view schematically showing the configuration of an inner side wall of an onshore aquaculture tank according to a further modified version of the second embodiment. 12 is a perspective view showing a schematic overall configuration of an onshore aquaculture tank according to a third embodiment of the present invention. FIG. 13 is a cross-sectional view taken along line CC of FIG. 12 showing a schematic overall configuration of an onshore aquaculture tank according to the third embodiment. FIG. 14 is a partially cutaway perspective view showing a schematic configuration of an example of a lid member according to the third embodiment. FIG. 15 is a perspective view showing a schematic overall configuration of an onshore aquaculture tank according to a fourth embodiment of the present invention. FIG. 16 is a cross-sectional view taken along line DD of FIG. 15 showing a schematic overall configuration of an onshore aquaculture tank according to the fourth embodiment.

[0036] Figures 1 and 2 show the overall structure of an on-land aquaculture tank according to a first embodiment of the present invention, Figure 3 shows the structure of an outer side wall, an inner side wall, and a portion of the cover member according to the first embodiment, and Figure 4 shows the structure of an air bubble release mechanism according to the first embodiment. This first embodiment relates to an aquaculture tank having an outer side wall made of brick.

[0037] In Figures 1 and 2, reference numeral 10 denotes a cylindrical aquaculture tank that contains aquaculture water for land-based aquaculture of fish, shrimp, and other aquaculture targets. This aquaculture tank 10 has a double structure consisting of an annular inner side wall 11 that contains the aquaculture water and forms the tank body, and an annular outer side wall 12 formed around the inner side wall 11. The gap between the inner side wall 11 and the outer side wall 12 forms an annular heated space 13 filled with air. However, in the first embodiment, portions of the outer side wall 12 and the heated space 13 (the front side in Figure 1) are cut out, so that the inner side wall 11 is not completely annular, exposing the inner side wall 11. The bottom of the aquaculture tank 10 is formed by a circular, insulating bottom wall 14. By way of example, the aquaculture tank 10 has an inner diameter of 500 cm, an outer diameter of 560 cm, and a height of 120 cm. The culture tank 10 normally contains culture water up to a height of about 100 cm.

[0038] In the first embodiment, the inner side wall 11 is formed by forming a flat metal plate with high thermal conductivity into an annular shape. Specifically, the inner side wall 11 is made of a naval brass plate processed into a cylindrical shape. Naval brass is an alloy of copper, zinc, and tin, and is strong and seawater-resistant, making it resistant to corrosion by seawater. Naval brass is widely used for military ship parts and has a thermal conductivity of 117 (W / m·k). This value is significantly higher than the thermal conductivity of corrosion-resistant stainless steel, which is approximately 16.7 (W / m·k). A drain port (drain) 11a is provided at the lower front portion of the inner side wall 11. By way of example only, the inner side wall 11 has an inner diameter of 500 cm, the same as the inner diameter of the aquaculture tank 10, a height of 115 cm, and a thickness of 3 cm.

[0039] In the first embodiment, the outer side wall 12 is formed of a material with low thermal conductivity. Specifically, as shown in detail in FIG. 3 , it is composed of brick walls 12a and 12b stacked in a double radial configuration and an insulating plate 12c inserted between the brick walls 12a and 12b. Brick (ordinary brick) has a very low thermal conductivity of 0.612 (W / m·k), and the insulating plate 12c is provided between the brick walls, resulting in a very low thermal conductivity of the outer side wall 12 and excellent thermal insulation. Furthermore, brick walls are inexpensive, easy to fabricate, and are less susceptible to deterioration by ultraviolet rays, resulting in a long service life and excellent aesthetics. The brick wall may be single-ply or triple-ply or more. In the case of triple-ply or more, insulating plates may be provided between the brick walls. Alternatively, insulating plates may not be provided. As a mere example, the outer diameter of the outer side wall 12 is 560 cm, the same as the outer diameter of the aquaculture tank 10, the height is 120 cm, the same as the height of the aquaculture tank 10, and the thickness is 20 cm.

[0040] In the first embodiment, the heating space 13 is formed by the gap between the inner side wall 11 and the outer side wall 12 and is filled with air. The heating space 13 includes an electric heater 15 (corresponding to the heater of the present invention), its heat-generating portion, and an air tube 16b (see FIG. 4 ) of the bubble release mechanism 16. The air tube 16b is provided to heat the generated bubbles with the air in the heating space 13. Note that the heat-generating portion of the electric heater 15, the bubble release mechanism 16, and the air tube 16b are not shown in FIGS. 1 and 3 . Because the outer side wall 12 and the bottom wall 14 have high thermal insulation properties, heat within the heating space 13 is hardly conducted to the outside via the outer side wall 12 and the bottom wall 14, and heat conduction occurs only to the inner side wall 11. Therefore, heat within the heating space 13 is transferred to the culture water via the inner side wall 11. As a mere example, the height of the heating space 13 is 115 cm, the same as the height of the inner side wall 11, and the width is 10 cm.

[0041] As shown in Figure 3, the upper surface of the annular heating space 13 is sealed by a plurality of arc-shaped cover members 17, each of which is made of a material with low thermal conductivity and has a meshed shape for thermal insulation. Wood and various foamed resin materials are used as the low-thermal-conductivity material for the arc-shaped cover members 17, taking into consideration ease of shaping and strength. Wood has a thermal conductivity of approximately 0.2 (W / m·k), providing sufficient thermal insulation, low manufacturing costs, and strength. Wood that has been coated with a fireproof and waterproof coating (e.g., hot-dip paint) and then molded is preferred.

[0042] The bottom wall 14 in the first embodiment is formed from waterproof and heat-insulating concrete and is provided over the entire bottom of the aquaculture tank 10. Although not shown, the bottom wall 14 is provided with an annular groove, into which the lower end of the cylindrical inner side wall 11 fits to secure the inner side wall 11. The fitting portion between the inner side wall 11 and the bottom wall 14 is treated with caulking or the like to prevent water leakage. Note that the structure for securing the inner side wall 11 to the bottom wall 14 is not limited to the structure described above and can be configured in various ways.

[0043] 2, the electric heater 15 in the first embodiment is provided in the heating space 13, and may be, for example, a commercially available 3 kW sauna heater. Although not shown, the heater's heat-generating portion, such as a nickel-chromium wire or a sheathed wire surrounded by a metal tube, is preferably installed in a meandering configuration along the circumferential direction of the heating space 13. The air and the inner side wall 11 in the heating space 13 are heated by thermal conduction and thermal convection from the electric heater 15 and the heat-generating portion, and the inner side wall 11 is effectively heated by thermal radiation, in which electromagnetic waves emitted from the electric heater 15 pass through the air in the heating space 13 and reach the inner side wall 11.

[0044] 2 and 4, the bubble release mechanism 16 in the first embodiment is composed of an air blower 16a that is provided outside the aquaculture tank 10 and generates air, a microbubble or fine bubble generating nozzle 16c that is provided in the aquaculture water in the aquaculture tank 10 and generates microbubbles or fine bubbles, an air tube 16b that is provided mainly within the heating space 13 and sends air from the air blower 16a to the microbubble or fine bubble generating nozzle 16c, and tube joints 16d and 16e that connect the air tube 16b to the inside and outside of the heating space 13. The air tube 16b is preferably installed in a winding shape along the circumferential direction of the heating space 13 so that the air passing through it is effectively heated by the air within the heating space 13. As the air blower 16a, for example, an air blower AP-35L manufactured by Seaforce Co., Ltd. can be used, as the air tube 16b, for example, a commercially available heat-resistant silicone tube can be used, and as the microbubble or fine bubble generating nozzle 16c, for example, a microbubble generating nozzle eco-bubble (registered trademark) S1 or S2 nozzle manufactured by Daikogiken Co., Ltd. can be used.

[0045] As shown in FIG. 1 , in the first embodiment, the entire top surface of the culture water in the culture tank 10 is covered with an insulating sheet 18 made of a material with low thermal conductivity. For example, a Crosslam thermal insulation sheet from KHV Corporation can be used as the insulating sheet 18. This thermal insulation sheet has a 12-layer structure with air inside, providing extremely high thermal insulation. Specifically, the Crosslam thermal insulation sheet is made of polyethylene, and in addition to the extremely low thermal conductivity of polyethylene (a single polyethylene sheet) of 0.33 to 0.50 (W / m·k), the 12 layers with air between them provide extremely high thermal insulation.

[0046] 2, in the first embodiment, the aquaculture tank 10 is provided with a temperature sensor 20 for detecting the temperature of the aquaculture water. The water temperature detected by the temperature sensor 20 is sent to the control device 21, which controls the operation of the electric heater 15. For example, when the control device 21 detects that the temperature of the aquaculture water has gradually decreased from 30°C to 27°C, the control device 21 outputs a signal to turn on the electric heater 15. This activates the electric heater 15, causing the temperatures of the air in the heating space 13, the inner side wall 11, and the aquaculture water to rise. When the control device 21 detects that the water temperature has reached 31°C, the control device 21 outputs a signal to turn off the electric heater 15. This causes the air in the heating space 13 to gradually decrease, and the temperature of the aquaculture water to gradually decrease.

[0047] As described above, in this first embodiment, the aquaculture tank 10 has a double structure consisting of an inner side wall 11 constituting the tank body for containing the aquaculture water and an outer side wall 12 formed around the inner side wall 11. The heating space 13, which is the gap between the inner side wall 11 and the outer side wall 12, is filled with air. Furthermore, a bottom wall 14 having thermal insulation properties is formed at the bottom of the aquaculture tank 10. An electric heater 15 is installed throughout the heating space 13. Furthermore, an air tube 16b of an air bubble release mechanism 16 is installed throughout the heating space 13. A microbubble or fine bubble generating nozzle 16c connected to the air tube 16b is disposed within the aquaculture tank 10. Furthermore, the top surface of the heating space 13 is sealed with a lid member 17, and the entire top surface of the aquaculture water in the aquaculture tank 10 is covered with an insulating sheet 18.

[0048] As described above, the aquaculture tank 10 is insulated on all sides by the outer side walls 12, the bottom wall 14, the lid member 17 that seals the top surface of the heating space 13, and the insulating sheet 18 that completely covers the top surface of the aquaculture water. The outer side walls 12 have a low thermal conductivity of 0.612 (W / m·k), and are constructed with a double-layered brick structure, with an insulating plate 12c inserted between them, resulting in extremely low thermal conductivity. The bottom wall 14 is made of concrete with low thermal conductivity (1.6 (W / m·k)), the lid member 17 is also made of wood with very low thermal conductivity (0.12 to 0.19 (W / m·k)), and the insulating sheet 18 is also made of a material with extremely low thermal conductivity. Therefore, the aquaculture tank 10 has very high insulation performance and is configured to minimize heat loss to the outside.

[0049] In fact, 200m ３ A similarly insulated aquaculture tank containing the culture water was placed inside an agricultural greenhouse, and the temperature of the culture water was measured without heating. The water temperature began to rise gradually shortly after sunrise, and this rise continued until sunset. When the air temperature inside the agricultural greenhouse was below 45-50°C, the water temperature ultimately rose by 1.0-1.5°C. The water temperature began to drop from sunset and continued to drop until sunrise in the morning, dropping by 1.0-1.5°C. No heating was used, and this gradual change in water temperature was caused only by changes in the room temperature inside the agricultural greenhouse.

[0050] If it is desired to maintain the temperature of the culture water in the culture tank 10 at, for example, 30°C, and the environmental temperature of the culture tank 10 (room temperature of the agricultural greenhouse) is 20 to 25°C throughout the year, the temperature of the culture water will gradually decrease to approach the environmental temperature (for example, 25°C). Heating will begin when the temperature of the culture water reaches a lower threshold temperature (for example, 27°C), and will end when the temperature of the culture water gradually rises to an upper threshold temperature (for example, 31°C).

[0051] In this first embodiment, heating is performed as follows. The air in the heating space 13 and the inner side wall 11 are heated by thermal radiation, thermal conduction, and thermal convection from the electric heater 15 installed in the heating space 13, and the culture water is efficiently heated by thermal conduction through the inner side wall 11. It should be noted that the air in the heating space 13 is heated. That is, the specific heat of water is 1 cal / °C, while the specific heat of air is 0.17 cal / °C, so air can be heated with less thermal energy than water. In addition, in the first embodiment, the inner side wall 11 is made of naval brass plate, which has a very high thermal conductivity (117 (W / m·k)), so the culture water is heated very efficiently. Furthermore, in the first embodiment, the air in the air tube 16b of the bubble discharge mechanism 16 is heated by the air in the heating space 13 and thermal radiation and thermal conduction from the electric heater 15, and the heated air is released as fine bubbles from the microbubble or fine bubble generating nozzle 16c into the culture water. Because the heated air is released into the culture water as fine bubbles with an astronomically large surface area for heat transfer, the culture water is heated extremely efficiently.

[0052] In a modification of the first embodiment, the outer side wall, inner side wall, and heating space can be configured to be continuous around the entire circumference of the water tank, as in the fourth embodiment described below. In this case, the outer side wall 12 is continuous around the entire circumference of the water tank and does not have any cutouts, improving thermal insulation. Furthermore, instead of the electric heater 15, a kerosene heater, heavy oil heater, gas heater, firewood heater, coal heater, or other heaters may be used.

[0053] In a modification of the first embodiment, the inner side wall 11 may be made of a plate of any metal material with high thermal conductivity, such as a copper alloy, an aluminum alloy, or an iron alloy, which is resistant to seawater.

[0054] In a modification of the first embodiment, the outer side wall 12 may be constructed of various materials with low thermal conductivity, such as mortar, concrete, or a wall made of locally produced stone such as Boso stone (Kanaya stone), instead of a brick wall.

[0055] In a modification of the first embodiment, the bottom wall 14 can be made of a highly water-resistant and heat-insulating resin-based material or military-grade rubber material instead of concrete.

[0056] 5 and 6 show a schematic partial configuration of an example of a cover member in a modified version of the first embodiment.

[0057] As shown in Figure 5, this modified embodiment has a double structure consisting of an annular inner side wall 11 that constitutes the tank body for containing the aquaculture water, and an annular outer side wall 12' formed around the inner side wall 11. The outer side wall 12' is made of a mortar wall with low thermal conductivity. The gap between the inner side wall 11 and the outer side wall 12' constitutes an annular heating space 13 filled with air. The upper surface of the heating space 13 is sealed by a plurality of arc-shaped, insulating cover members 17' that are made of a material with low thermal conductivity and have a meshed shape. The material that constitutes the arc-shaped cover members 17' is as described above.

[0058] As shown in Figure 6, the arc-shaped lid member 17' has a through hole 19 that passes through the lid member 17' in the vertical direction and communicates with the heating space section 13, and the air tube 16b of the bubble release mechanism 16 is connected to the inside and outside of the heating space section 13 via a tube fitting 16d inserted into this through hole 19.

[0059] 7 and 8 show a schematic diagram of the overall configuration of a land-based aquaculture tank according to a second embodiment of the present invention. The second embodiment relates to an aquaculture tank having outer side walls made of Styrofoam material.

[0060] In Figures 7 and 8, reference numeral 110 denotes a cylindrical aquaculture tank that contains aquaculture water for land-based aquaculture of fish, shrimp, and other aquaculture targets, along with the aquaculture targets. This aquaculture tank 110 has a double structure consisting of an annular inner side wall 111 that contains the aquaculture water and forms the tank body, and an annular outer side wall 112 formed around the inner side wall 111. The gap between the inner side wall 111 and the outer side wall 112 forms an annular heated space 113 filled with air. However, in the second embodiment, portions of the outer side wall 112 and the heated space 113 (the front side in Figure 7) are cut out, so that the ring is not formed, and the inner side wall 111 is exposed. The bottom of the aquaculture tank 110 is formed by a circular bottom wall 114 that has thermal insulation properties. As a mere example, the aquaculture tank 110 has an inner diameter of 500 cm, an outer diameter of 560 cm, and a height of 120 cm. The aquaculture tank 110 normally contains aquaculture water to a height of about 100 cm.

[0061] In the second embodiment, the inner side wall 111 is formed by forming a flat metal plate with high thermal conductivity into an annular shape. Specifically, the inner side wall 111 is formed of a flat naval brass plate processed into a cylindrical shape. Naval brass is an alloy of copper, zinc, and tin, and is strong and resistant to seawater corrosion. Naval brass is widely used for military ship parts and has a thermal conductivity of 117 (W / m·k). This value is significantly higher than the thermal conductivity of corrosion-resistant stainless steel, which is approximately 16.7 (W / m·k). A drain port (drain) 111a is provided at the lower front portion of the inner side wall 111. By way of example only, the inner diameter of the inner side wall 111 is 500 cm, the same as the inner diameter of the aquaculture tank 110, with a height of 115 cm and a thickness of 3 cm.

[0062] The outer side wall 112 in the second embodiment is formed of a material with low thermal conductivity. Specifically, it is composed of a plurality of H-shaped steel supports 122 and an arc-shaped Styrofoam plate whose circumferential ends are sandwiched between the two H-shaped steel supports 122. Styrofoam has an extremely low thermal conductivity of 0.022 (W / m·k), providing excellent thermal insulation. As a mere example, the outer diameter of the outer side wall 112 is 560 cm, the same as the outer diameter of the aquaculture tank 110, its height is 120 cm, the same as the height of the aquaculture tank 110, and its thickness is 20 cm.

[0063] The heating space 113 in the second embodiment is formed by the gap between the inner side wall 111 and the outer side wall 112 and is filled with air. The heating space 113 includes an electric heater 115 (corresponding to the heater of the present invention) and its heat-generating portion, as well as an air tube of a bubble release mechanism (not shown), similar to that shown in FIGS. 2 and 4 . The air tube is provided to heat the generated bubbles with the air in the heating space 113. Note that the heat-generating portion of the electric heater 115, the bubble release mechanism, and the air tube are not shown in FIGS. 7 and 8 . Because the outer side wall 112 and the bottom wall 114 have high thermal insulation properties, heat within the heating space 113 is hardly conducted to the outside via the outer side wall 112 and the bottom wall 114, and heat conduction occurs only to the inner side wall 111. Therefore, heat within the heating space 113 is transferred to the culture water via the inner side wall 111. As a mere example, the height of the heating space 113 is 115 cm, the same as the height of the inner side wall 111, and the width is 10 cm.

[0064] The top surface of the annular heating space 113 is sealed by multiple arc-shaped lid members, similar to those shown in Figure 3, made of a low-thermal-conductivity material and fitted with a meshing shape for thermal insulation. Wood and various foamed resin materials are used as low-thermal-conductivity materials for these arc-shaped lid members, taking into consideration ease of shaping and strength. Wood has a thermal conductivity of approximately 0.2 (W / m·k), providing sufficient thermal insulation, low manufacturing costs, and strength. Wood that has been treated with a fireproof and waterproof coating (e.g., hot-dip lacquering) and then molded is preferred.

[0065] The bottom wall 114 in the second embodiment is formed from waterproof and heat-insulating concrete and is provided over the entire bottom of the aquaculture tank 110. Although not shown, the bottom wall 114 is provided with an annular groove, into which the lower end of the cylindrical inner side wall 111 fits to secure the inner side wall 111. The fitting portion between the inner side wall 111 and the bottom wall 114 is treated with caulking or the like to prevent water leakage. Note that the structure for securing the inner side wall 111 to the bottom wall 114 is not limited to the structure described above and can be configured in various ways.

[0066] As shown in Fig. 8, the electric heater 115 in the second embodiment is provided in the heating space 113, and may be, for example, a commercially available 3 kW sauna heater. Although not shown, the heater's heat-generating portion, such as a nickel-chromium wire or a sheathed wire surrounded by a metal tube, is preferably installed in a meandering configuration along the circumferential direction of the heating space 113. The air and the inner side wall 111 in the heating space 113 are heated by thermal conduction and thermal convection from the electric heater 115 and the heat-generating portion, and the inner side wall 111 is effectively heated by thermal radiation, in which electromagnetic waves emitted from the electric heater 115 pass through the air in the heating space 113 and reach the inner side wall 111.

[0067] 2 and 4 is provided, and this bubble release mechanism is composed of an air blower that is provided outside the aquaculture tank 110 and generates air, a microbubble or fine bubble generating nozzle that is provided in the aquaculture water in the aquaculture tank 110 and generates microbubbles or fine bubbles, an air tube that is provided mainly in the heating space 113 and sends air from the air blower to the microbubble or fine bubble generating nozzle, and a tube joint that connects the air tube to the inside and outside of the heating space 113. The air tube is preferably installed in a winding shape along the circumferential direction of the heating space 113 so that the air passing through it is effectively heated by the air in the heating space 113. As the air blower, for example, the AP-35L air blower manufactured by Seaforce Co., Ltd. can be used, as the air tube, for example, a commercially available heat-resistant silicone tube can be used, and as the microbubble or fine bubble generating nozzle, for example, the eco-bubble S1 or S2 microbubble generating nozzle manufactured by Daikogiken Co., Ltd. can be used.

[0068] As shown in Figure 7, in the second embodiment, the entire top surface of the culture water in the culture tank 110 is covered with an insulating sheet 118 made of a material with low thermal conductivity. For example, a Crosslam thermal insulation sheet from KHV Corporation can be used as the insulating sheet 118. This thermal insulation sheet has a 12-layer structure with air inside, providing extremely high thermal insulation. Specifically, the Crosslam thermal insulation sheet is made of polyethylene, and in addition to the extremely low thermal conductivity of polyethylene (a single polyethylene sheet) of 0.33 to 0.50 (W / m·k), the 12 layers with air between them provide extremely high thermal insulation.

[0069] In the second embodiment, a temperature sensor (not shown) for detecting the temperature of the culture water is provided in the culture tank 110 similar to that shown in FIG. 2 , and the water temperature detected by this temperature sensor is sent to the control device to control the operation of the electric heater 115. For example, when it is detected that the temperature of the culture water gradually drops from 30°C to 27°C, the control device outputs a signal to turn on the electric heater 115. As a result, the electric heater 115 is activated, and the temperatures of the air in the heating space 113, the inner side wall 111, and the culture water rise. When it is detected that the water temperature reaches 31°C, the control device outputs a signal to turn off the electric heater 115. As a result, the air in the heating space 113 gradually drops, and the temperature of the culture water gradually drops.

[0070] As described above, in this second embodiment, the aquaculture tank 110 has a double structure consisting of an inner side wall 111 constituting the tank body for containing the aquaculture water and an outer side wall 112 formed around the inner side wall 111. The heating space 113, which is the gap between the inner side wall 111 and the outer side wall 112, is filled with air. Furthermore, a bottom wall 114 with thermal insulation is formed at the bottom of the aquaculture tank 110. An electric heater 115 is installed throughout the heating space 113. Air tubes of a bubble release mechanism are installed throughout the heating space 113. Microbubble or fine bubble generating nozzles connected to the air tubes are disposed within the aquaculture tank 110. Furthermore, the top surface of the heating space 113 is sealed with a lid, and the entire top surface of the aquaculture water in the aquaculture tank 110 is covered with an insulating sheet 118.

[0071] In this way, the aquaculture tank 110 is insulated on all sides by the outer side walls 112, the bottom wall 114, the lid member that seals the top surface of the heated space 113, and the insulating sheet 118 that covers the entire top surface of the aquaculture water. The outer side walls 112 are made of Styrofoam, which has an extremely low thermal conductivity of 0.022 (W / m·k). The bottom wall 114 is made of concrete with low thermal conductivity (1.6 (W / m·k)), the lid member is also made of wood with very low thermal conductivity (0.12 to 0.19 (W / m·k)), and the insulating sheet 118 is also made of a material with extremely low thermal conductivity. Therefore, the aquaculture tank 110 has very high insulation performance and is configured to minimize heat loss to the outside.

[0072] If it is desired to maintain the temperature of the culture water in the culture tank 110 at, for example, 30°C, and the environmental temperature of the culture tank 110 (room temperature of the agricultural greenhouse) is 20 to 25°C throughout the year, the temperature of the culture water will gradually decrease to approach the environmental temperature (for example, 25°C). Heating will begin when the temperature of the culture water reaches a lower threshold temperature (for example, 27°C), and will end when the temperature of the culture water gradually rises to an upper threshold temperature (for example, 31°C).

[0073] In the second embodiment, heating is performed as follows. The air in the heating space 113 and the inner side wall 111 are heated by thermal radiation, thermal conduction, and thermal convection from the electric heater 115 installed in the heating space 113, and the culture water is efficiently heated by thermal conduction through the inner side wall 111. It should be noted that the air in the heating space 113 is heated. That is, the specific heat of water is 1 cal / °C, while the specific heat of air is 0.17 cal / °C, so air can be heated with less thermal energy than water. In addition, in the second embodiment, the inner side wall 111 is made of naval brass plate, which has very high thermal conductivity (117 (W / m·k)), so the culture water is heated very efficiently. Furthermore, in the second embodiment, the air in the air tube of the bubble release mechanism is heated by the air in the heating space 113 and by thermal radiation and thermal conduction from the electric heater 115, and the heated air is released as fine bubbles from the microbubble or fine bubble generating nozzle into the culture water. Because the heated air is released into the culture water as fine bubbles with an astronomically large surface area for heat transfer, the culture water is heated extremely efficiently.

[0074] In a modification of the second embodiment, the outer side wall, inner side wall, and heating space can be configured to be continuous around the entire circumference of the water tank, as in the fourth embodiment described below. In this case, the outer side wall 112 is continuous around the entire circumference of the water tank and does not have any cutouts, improving thermal insulation. Furthermore, a kerosene heater, heavy oil heater, gas heater, firewood heater, coal heater, or other heaters may be used instead of the electric heater 115.

[0075] In a further modification of the second embodiment, the inner side wall 111 can be made of a plate of various metal materials with high thermal conductivity, such as copper alloy, aluminum alloy, iron alloy, etc., which are seawater-resistant, instead of naval brass.

[0076] In yet another modification of the second embodiment, the outer side wall 112 can be constructed of various materials with low thermal conductivity instead of Styrofoam panels, such as mortar walls, concrete walls, or walls made of local stone such as Boshu stone (Kanaya stone).

[0077] In a further modification of the second embodiment, the bottom wall 114 can be made of a highly water-resistant and heat-insulating resin-based material or military-grade rubber material instead of concrete.

[0078] Figure 9 shows the overall configuration of an on-land aquaculture tank 110' in a modified version of the second embodiment, in a cross section similar to that shown in Figure 8. Figure 10 shows the plan and front views of the upper and lower fixing brackets 123' and 124' in this modified version. In this modified version, the inner side wall 111' has the same configuration as the inner side wall 111 of the second embodiment, and an annular heating space 113' filled with air is provided in the gap between the inner side wall 111' and the outer side wall 112'. However, in this modified version, the outer side wall 112' is composed of multiple (here, 12) flat Styrofoam sheets. The left and right end faces of each Styrofoam sheet have a cross section that is inclined (75 degrees in this modified version) so that adjacent Styrofoam sheets are closely connected without any gaps. Each Styrofoam sheet is fixed to the inner side wall 111' by the upper fixing bracket 123' and the lower fixing bracket 124'. In FIG. 9, the heating space, the lid member, the bubble releasing mechanism, the electric heater, etc. are not shown.

[0079] 10(A) and (B), each upper fixing bracket 123' is made up of an arm portion 123a' whose base end is fixed to the inner side wall 111' by welding, and a wing-shaped retaining portion 123b' that is attached to the tip of this arm portion 123a' and is used to hold down the Styrofoam. Also, as shown in Figures 10(C) and (D), each lower fixing bracket 124' is made up of an arm portion 124a' whose base end is fixed to the inner side wall 111' by welding, and a wing-shaped retaining portion 124b' that is attached to the tip of this arm portion 124a' and is used to hold down the Styrofoam.

[0080] In this modified embodiment, the flat shape of the Styrofoam makes it extremely easy and inexpensive to manufacture, significantly reducing the manufacturing cost of the aquaculture tank. Moreover, installation is extremely easy. Furthermore, instead of using H-shaped steel supports 122 as in the second embodiment, the Styrofoam is fixed using simple and inexpensive upper and lower fixing brackets 123' and 124', which significantly reduces manufacturing costs and the labor required for manufacturing.

[0081] FIG. 11 shows a schematic configuration of an inner side wall 111" of an on-land aquaculture tank in a further modification of the second embodiment. In this modification, the outer side wall is also made of, for example, Styrofoam, which has heat insulating properties. However, in this modification, the inner side wall 111" is not formed by molding a flat metal plate into a ring shape, but is made of a thin corrugated metal member 111a" and a resin sheet 111b" stretched inside it. The corrugated metal member 111a" is bent into a ring shape so that its pitch direction is the up-and-down direction (the flow direction is the circumferential direction), and a resin sheet 111b" which is a waterproof sheet is stretched watertightly inside it to form the on-land aquaculture tank 110". Note that the heated space, lid member, bubble release mechanism, electric heater, etc. are not shown in FIG. 11.

[0082] According to this modified embodiment, the inner side wall is made up of a thin corrugated metal member and a resin sheet, which makes it extremely inexpensive and lightweight, making it very easy to manufacture and install, and making it possible to significantly reduce the manufacturing costs and labor required for the aquaculture tank.

[0083] 12 and 13 show a schematic diagram of the overall configuration of a land-based aquaculture tank according to a third embodiment of the present invention. This third embodiment relates to an aquaculture tank having outer side walls made of iron plates covered with a mortar fireproof material or galvalume steel plates covered with a mortar fireproof material.

[0084] In Figures 12 and 13, reference numeral 210 denotes a cylindrical aquaculture tank that contains aquaculture water for land-based aquaculture of fish, shrimp, and other aquaculture targets. This aquaculture tank 210 has a double structure consisting of an annular inner side wall 211 that contains the aquaculture water and forms the tank body, and an annular outer side wall 212 formed around the inner side wall 211. The gap between the inner side wall 211 and the outer side wall 212 forms an annular heated space 213 filled with air. However, in the third embodiment, portions of the outer side wall 212 and the heated space 213 (the front side in Figure 12) are cut out, so that the ring is not formed, and the inner side wall 211 is exposed. The bottom of the aquaculture tank 210 is formed by a circular bottom wall 214 that has thermal insulation properties. As a mere example, the aquaculture tank 210 has an inner diameter of 500 cm, an outer diameter of 560 cm, and a height of 120 cm. The aquaculture tank 210 normally contains aquaculture water up to a height of about 100 cm.

[0085] In the third embodiment, the inner side wall 211 is formed by forming a flat metal plate with high thermal conductivity into an annular shape. Specifically, the inner side wall 211 is made of a naval brass plate processed into a cylindrical shape. Naval brass is an alloy of copper, zinc, and tin, and is strong and resistant to seawater corrosion. Naval brass is widely used for military ship parts and has a thermal conductivity of 117 (W / m·k). This value is significantly higher than the thermal conductivity of corrosion-resistant stainless steel, which is approximately 16.7 (W / m·k). A drain port (drain) 211a is provided at the lower front portion of the inner side wall 211. By way of example only, the inner diameter of the inner side wall 211 is 500 cm, the same as the inner diameter of the aquaculture tank 210, with a height of 115 cm and a thickness of 3 cm.

[0086] In the third embodiment, the outer side wall 212 is formed of a material with low thermal conductivity. Specifically, it is constructed of an iron plate coated with hot-dip mortar fireproofing or a galvalume steel plate coated with hot-dip mortar fireproofing. Because mortar fireproofing has a low thermal conductivity of approximately 1.5 (W / m·k), the iron plate coated with mortar fireproofing or the galvalume steel plate coated with mortar fireproofing has a correspondingly low thermal conductivity, providing excellent thermal insulation. Furthermore, the iron plate coated with mortar fireproofing or the galvalume steel plate coated with mortar fireproofing is inexpensive, easy to manufacture, and resistant to UV degradation, resulting in a long service life and excellent aesthetics. As a mere example, the outer diameter of the outer side wall 212 is 560 cm, the same as the outer diameter of the aquaculture tank 210, its height is 120 cm, the same as the height of the aquaculture tank 210, and its thickness is 20 cm.

[0087] The heating space 213 in the third embodiment is formed by the gap between the inner side wall 211 and the outer side wall 212 and is filled with air. The heating space 213 is provided with an electric heater 215 (corresponding to the heater of the present invention) and its heat-generating portion, as well as an air tube of an air bubble release mechanism (not shown), similar to that shown in FIGS. 2 and 4 . The air tube is provided to heat the generated air bubbles with the air in the heating space 213. Note that the heat-generating portion of the electric heater 215, the air bubble release mechanism, and the air tube are not shown in FIGS. 12 and 13 . Because the outer side wall 212 and the bottom wall 214 have high thermal insulation properties, heat within the heating space 213 is hardly conducted to the outside via the outer side wall 212 and the bottom wall 214, and heat conduction occurs only to the inner side wall 211. Therefore, heat within the heating space 213 is transferred to the culture water via the inner side wall 211. As a mere example, the height of the heating space 213 is 115 cm, the same as the height of the inner side wall 211, and the width is 10 cm.

[0088] As shown in Figure 14, the top surface of the annular heating space 213 is sealed by a plurality of arc-shaped cover members 217, similar to those shown in Figure 3, which are made of a low-thermal-conductivity material and have a meshed, insulating shape. Wood and various foamed resin materials are used as low-thermal-conductivity materials for the arc-shaped cover members 217, taking into consideration ease of shaping and strength. Wood has a thermal conductivity of approximately 0.2 (W / m·k), providing sufficient insulating properties, low manufacturing costs, and strength. Wood that has been treated with a fireproof and waterproof coating (e.g., hot-dip lacquering) and then molded is preferred.

[0089] The bottom wall 214 in the third embodiment is formed of waterproof and heat-insulating concrete and is provided over the entire bottom of the aquaculture tank 210. Although not shown, the bottom wall 214 is provided with an annular groove, into which the lower end of the cylindrical inner side wall 211 fits to secure the inner side wall 211. The fitting portion between the inner side wall 211 and the bottom wall 214 is treated with caulking or the like to prevent water leakage. Note that the structure for securing the inner side wall 211 to the bottom wall 214 is not limited to the structure described above and can be configured in various ways.

[0090] 13, the electric heater 215 in the third embodiment is provided in the heating space 213, and may be, for example, a commercially available 3 kW sauna heater. Although not shown, the heater's heat-generating portion, such as a nickel-chromium wire or a sheathed wire surrounded by a metal tube, is preferably installed in a meandering shape around the circumferential direction of the heating space 213. The air and the inner side wall 211 in the heating space 213 are heated by thermal conduction and thermal convection from the electric heater 215 and the heat-generating portion, and the inner side wall 211 is effectively heated by thermal radiation, in which electromagnetic waves emitted from the electric heater 215 pass through the air in the heating space 213 and reach the inner side wall 211.

[0091] 2 and 4. This bubble release mechanism is provided outside the aquaculture tank 210 and includes an air blower that generates air, a microbubble or fine bubble generating nozzle that is provided in the aquaculture water in the aquaculture tank 210 and generates microbubbles or fine bubbles, an air tube that is provided mainly in the heating space 213 and sends air from the air blower to the microbubble or fine bubble generating nozzle, and a tube joint that connects the air tube to the inside and outside of the heating space 213. The air tube is preferably installed in a meandering shape along the circumferential direction of the heating space 213 so that the air passing through it is effectively heated by the air in the heating space 213. As the air blower, for example, the AP-35L air blower manufactured by Seaforce Co., Ltd. can be used, as the air tube, for example, a commercially available heat-resistant silicone tube can be used, and as the microbubble or fine bubble generating nozzle, for example, the eco-bubble S1 or S2 microbubble generating nozzle manufactured by Daikogiken Co., Ltd. can be used.

[0092] As shown in Figure 12, in the third embodiment, the entire top surface of the culture water in the culture tank 210 is covered with an insulating sheet 218 made of a material with low thermal conductivity. For example, a Crosslam thermal insulation sheet from KHV Corporation can be used as the insulating sheet 218. This thermal insulation sheet has a 12-layer structure with air inside, providing extremely high thermal insulation. Specifically, the Crosslam thermal insulation sheet is made of polyethylene. The thermal conductivity of polyethylene (a single polyethylene sheet) is extremely low, at 0.33 to 0.50 (W / m·k), and the 12 layers with air between them provide extremely high thermal insulation.

[0093] In the third embodiment, a temperature sensor (not shown) for detecting the temperature of the culture water is provided in the culture tank 210 similar to that shown in FIG. 2 , and the water temperature detected by this temperature sensor is sent to the control device to control the operation of the electric heater 215. For example, when it is detected that the temperature of the culture water gradually drops from 30°C to 27°C, the control device outputs a signal to turn on the electric heater 215. As a result, the electric heater 215 is activated, and the temperatures of the air in the heating space 213, the inner side wall 211, and the culture water rise. When it is detected that the water temperature reaches 31°C, the control device outputs a signal to turn off the electric heater 215. As a result, the air in the heating space 213 gradually drops, and the temperature of the culture water gradually drops.

[0094] As described above, in this third embodiment, the aquaculture tank 210 has a double structure consisting of an inner side wall 211 constituting the tank body for containing the aquaculture water and an outer side wall 212 formed around the inner side wall 211. The heating space 213, which is the gap between the inner side wall 211 and the outer side wall 212, is filled with air. Furthermore, a bottom wall 214 with thermal insulation is formed at the bottom of the aquaculture tank 210. An electric heater 215 is installed throughout the heating space 213. Furthermore, air tubes of a bubble release mechanism are installed throughout the heating space 213. Microbubble or fine bubble generating nozzles connected to the air tubes are disposed within the aquaculture tank 210. Furthermore, the upper surface of the heating space 213 is sealed with a lid member 217, and the entire upper surface of the aquaculture water in the aquaculture tank 210 is covered with an insulating sheet 218.

[0095] In this way, the aquaculture tank 210 is insulated on all sides by the outer side walls 212, the bottom wall 214, the lid member 217 that seals the top surface of the heating space 213, and the insulating sheet 218 that covers the entire top surface of the aquaculture water. Because the thermal conductivity of the mortar fireproofing material used in the outer side walls 212 is low (approximately 1.5 W / m·k), an iron plate coated with mortar fireproofing or a galvalume steel plate coated with mortar fireproofing also has low thermal conductivity. The bottom wall 214 is made of concrete with low thermal conductivity (1.6 W / m·k), the lid member 217 is also made of wood with very low thermal conductivity (0.12 to 0.19 W / m·k), and the insulating sheet 218 is also made of a material with extremely low thermal conductivity. Therefore, the aquaculture tank 210 has very high insulation performance and is configured to minimize heat loss to the outside.

[0096] If it is desired to maintain the temperature of the culture water in the culture tank 210 at, for example, 30°C, and the environmental temperature of the culture tank 210 (room temperature of the agricultural greenhouse) is 20 to 25°C throughout the year, the temperature of the culture water will gradually decrease to approach the environmental temperature (for example, 25°C). Heating will begin when the temperature of the culture water reaches a lower threshold temperature (for example, 27°C), and will end when the temperature of the culture water gradually rises to an upper threshold temperature (for example, 31°C).

[0097] In the third embodiment, heating is performed as follows. The air in the heating space 213 and the inner side wall 211 are heated by thermal radiation, thermal conduction, and thermal convection from the electric heater 215 installed in the heating space 213, and the culture water is efficiently heated by thermal conduction through the inner side wall 211. It should be noted that the air in the heating space 213 is heated. That is, the specific heat of water is 1 cal / °C, while the specific heat of air is 0.17 cal / °C, so air can be heated with less thermal energy than water. In addition, in the third embodiment, the inner side wall 211 is made of naval brass plate, which has very high thermal conductivity (117 (W / m·k)), so the culture water is heated very efficiently. Furthermore, in the third embodiment, the air in the air tube of the bubble release mechanism is heated by the air in the heating space 213 and by thermal radiation and thermal conduction from the electric heater 215, and the heated air is released as fine bubbles into the culture water from the microbubble or fine bubble generating nozzle. Because the heated air is released into the culture water as fine bubbles with an astronomically large surface area for heat transfer, the culture water is heated extremely efficiently.

[0098] In a modification of the third embodiment, the outer side wall, inner side wall, and heating space can be configured to be continuous around the entire circumference of the water tank, as in the fourth embodiment described below. In this case, the outer side wall 212 is continuous around the entire circumference of the water tank and does not have any cutouts, improving thermal insulation. Furthermore, a kerosene heater, heavy oil heater, gas heater, firewood heater, coal heater, or other heaters may be used instead of the electric heater 215.

[0099] In a further modification of the third embodiment, the inner side wall 211 can be made of a plate of various metal materials with high thermal conductivity, such as copper alloy, aluminum alloy, iron alloy, etc., which are seawater-resistant, instead of naval brass.

[0100] In yet another modification of the third embodiment, the outer side wall 212 can be constructed of a wall made of various materials with low thermal conductivity, instead of an iron plate coated with a mortar fireproofing material or a galvalume steel plate coated with a mortar fireproofing material. For example, a mortar wall, a concrete wall, or a wall made of locally produced stone such as Boso stone (Kanaya stone) can be used.

[0101] In a modification of the third embodiment, the bottom wall 214 can be made of a highly water-resistant and insulating resin-based material or military-grade rubber material instead of concrete.

[0102] 15 and 16 show a schematic diagram of the overall configuration of an on-land aquaculture tank according to a fourth embodiment of the present invention. This fourth embodiment relates to an aquaculture tank having outer side walls made of continuous brick walls around the entire perimeter and further having a fan inside the heating space.

[0103] In Figures 15 and 16, reference numeral 310 denotes a cylindrical aquaculture tank containing aquaculture water for land-based aquaculture of fish, shrimp, and other aquaculture targets. This aquaculture tank 310 has a double structure consisting of an annular inner side wall 311 that contains the aquaculture water and forms the tank body, and an annular outer side wall 312 that extends continuously around the entire circumference of the inner side wall 311. The gap between the inner side wall 311 and the outer side wall 312 is filled with air, forming an annular heated space 313 that extends continuously around the entire circumference of the tank. The outer side wall 312 and the heated space 313 form a continuous ring without any cutouts. The bottom of the aquaculture tank 310 is formed by a circular, insulating bottom wall 314. By way of example, the aquaculture tank 310 has an inner diameter of 500 cm, an outer diameter of 560 cm, and a height of 120 cm. This aquaculture tank 310 normally contains aquaculture water up to a height of about 100 cm.

[0104] In the fourth embodiment, the inner side wall 311 is formed by forming a flat metal plate with high thermal conductivity into an annular shape. Specifically, the inner side wall 311 is made of a naval brass plate processed into a cylindrical shape. Naval brass is an alloy of copper, zinc, and tin, and is strong and resistant to seawater corrosion. Naval brass is widely used for military ship parts and has a thermal conductivity of 117 (W / m·k). This value is significantly higher than the thermal conductivity of corrosion-resistant stainless steel, which is approximately 16.7 (W / m·k). A drain (not shown) is provided at the bottom of the inner side wall 311 and penetrates the outer side wall 312. By way of example only, the inner side wall 311 has an inner diameter of 500 cm, the same as the inner diameter of the aquaculture tank 310, a height of 115 cm, and a thickness of 3 cm.

[0105] In the fourth embodiment, the outer side wall 312 is formed from a continuous material with low thermal conductivity around the entire periphery. Specifically, similar to the example shown in FIG. 3 , it is composed of two brick walls stacked radially in a double layer with an insulating plate inserted between the brick walls. Brick (ordinary brick) has a very low thermal conductivity of 0.612 (W / m·k), and the insulating plate between the brick walls provides excellent thermal insulation. Furthermore, brick walls are inexpensive, easy to fabricate, and resistant to UV degradation, resulting in a long service life and aesthetic appeal. The brick wall may be single-ply or triple-ply or more. In the case of triple-ply or more brick walls, insulating plates may be inserted between the brick walls. Alternatively, no insulating plate may be inserted. The outer side wall 312 is continuous around the entire periphery and has no cutouts, providing superior insulation. As a mere example, the outer diameter of the outer side wall 312 is 560 cm, the same as the outer diameter of the aquaculture tank 310, the height is 120 cm, the same as the height of the aquaculture tank 310, and the thickness is 20 cm.

[0106] In the fourth embodiment, the heating space 313 is formed continuously around the entire circumference of the tank by the gap between the inner side wall 311 and the outer side wall 312, and is filled with air. The heating space 313 includes an electric heater 315 (corresponding to the heater of the present invention) and an air tube (not shown) of a bubble release mechanism similar to that shown in FIGS. 2 and 4 . The air tube is provided to heat the generated bubbles with the air in the heating space 313. Note that the bubble release mechanism and air tube are not shown in FIGS. 15 and 16 . The heating space 313 includes at least one fan 323, such as an axial fan, positioned away from the electric heater 315 to send air in a circumferential direction. This at least one fan 323 may be composed of multiple fans arranged vertically. By providing at least one fan 323, the air in the heating space 313 heated by the electric heater 315 circulates through the heating space 313, particularly along its circumferential direction, so that it is heated evenly. Furthermore, because the outer side wall 312 and the bottom wall 314 have high thermal insulation properties, heat in the heating space 313 is hardly conducted to the outside via the outer side wall 312 and the bottom wall 314, and heat conduction occurs only to the inner side wall 311. Therefore, heat in the heating space 313 is conducted to the culture water via the inner side wall 311. As a mere example, the height of the heating space 313 is 115 cm, the same as the height of the inner side wall 311, and its width is 10 cm.

[0107] Although not shown, the upper surface of the annular heating space 313 is sealed by multiple arc-shaped lid members, similar to that shown in Figure 3, made of a material with low thermal conductivity and fitted together to provide thermal insulation. Wood and various foamed resin materials are used as low-thermal-conductivity materials for these arc-shaped lid members, taking into consideration ease of shaping and strength. Wood has a thermal conductivity of approximately 0.2 (W / m·k), providing sufficient thermal insulation, low manufacturing costs, and strength. Wood that has been coated with a fireproof and waterproof coating (e.g., hot-dip lacquer) and then molded is preferred.

[0108] The bottom wall 314 in the fourth embodiment is formed of waterproof and heat-insulating concrete and is provided over the entire bottom of the aquaculture tank 310. Although not shown, the bottom wall 314 is provided with an annular groove, into which the lower end of the cylindrical inner side wall 311 fits to secure the inner side wall 311. The fitting portion between the inner side wall 311 and the bottom wall 314 is treated with caulking or the like to prevent water leakage. Note that the structure for securing the inner side wall 311 to the bottom wall 314 is not limited to the structure described above and can be configured in various ways.

[0109] 16 , the electric heater 315 in the fourth embodiment is provided in the heating space 313, and may be, for example, a commercially available 3 kW sauna heater. At least one fan 323 is provided in the heating space 313, so that the air in the heating space 313 circulates circumferentially around the heating space 313 and is heated evenly. Thus, the air in the heating space 313 and the inner side wall 311 are heated by thermal conduction and thermal convection from the electric heater 315, and the inner side wall 311 is effectively heated by thermal radiation, which occurs when electromagnetic waves emitted from the electric heater 315 pass through the air in the heating space 313 and reach the inner side wall 311.

[0110] 2 and 4 is provided, and this bubble release mechanism is composed of an air blower that is provided outside the aquaculture tank 310 and generates air, a microbubble or fine bubble generating nozzle that is provided in the aquaculture water in the aquaculture tank 310 and generates microbubbles or fine bubbles, an air tube that is provided mainly in the heating space 313 and sends air from the air blower to the microbubble or fine bubble generating nozzle, and a tube joint that connects the air tube to the inside and outside of the heating space 313. The air tube is preferably installed in a winding shape along the circumferential direction of the heating space 313 so that the air passing through it is effectively heated by the air in the heating space 313. As the air blower, for example, the AP-35L air blower manufactured by Seaforce Co., Ltd. can be used, as the air tube, for example, a commercially available heat-resistant silicone tube can be used, and as the microbubble or fine bubble generating nozzle, for example, the eco-bubble S1 or S2 microbubble generating nozzle manufactured by Daikogiken Co., Ltd. can be used.

[0111] As shown in Figure 15, in the fourth embodiment, the entire top surface of the culture water in the culture tank 310 is covered with an insulating sheet 318 made of a material with low thermal conductivity. For example, a Crosslam thermal insulation sheet from KHV Corporation can be used as the insulating sheet 318. This thermal insulation sheet has a 12-layer structure with air inside, providing extremely high thermal insulation. Specifically, the Crosslam thermal insulation sheet is made of polyethylene. The thermal conductivity of polyethylene (a single polyethylene sheet) is extremely low, at 0.33 to 0.50 (W / m·k), and the 12 layers with air between them provide extremely high thermal insulation.

[0112] In the fourth embodiment, although not shown, a temperature sensor for detecting the temperature of the culture water is provided in the culture tank 310, similar to that shown in FIG. 2 , and the water temperature detected by this temperature sensor is sent to the control device to control the operation of the electric heater 315. For example, when it is detected that the temperature of the culture water gradually drops from 30°C to 27°C, the control device outputs a signal to turn on the electric heater 315. As a result, the electric heater 315 is activated, and the temperatures of the air in the heating space 313, the inner side wall 311, and the culture water rise. When it is detected that the water temperature reaches 31°C, the control device outputs a signal to turn off the electric heater 315. As a result, the air in the heating space 313 gradually drops, and the temperature of the culture water gradually drops.

[0113] As described above, in this fourth embodiment, the aquaculture tank 310 has a double structure consisting of an inner side wall 311 that constitutes the tank body containing the aquaculture water and an outer side wall 312 that extends continuously around the entire circumference of the tank. The heating space 313, which is the gap between the inner side wall 311 and the outer side wall 312, is filled with air. An insulating bottom wall 314 is formed at the bottom of the aquaculture tank 310. An electric heater 315 is provided within the heating space 313. At least one fan 323 is provided within the heating space 313 to circulate air within the heating space 313 in the circumferential direction. Furthermore, air tubes for a bubble release mechanism are installed throughout the heating space 313. Microbubble or fine bubble generating nozzles connected to the air tubes are located within the aquaculture tank 310. Furthermore, the upper surface of the heating space portion 313 is sealed with a lid member, and the entire upper surface of the culture water in the culture tank 310 is covered with a heat insulating sheet 318.

[0114] As described above, the aquaculture tank 310 is insulated on all sides by the outer side walls 312, the bottom wall 314, the lid member sealing the top surface of the heated space 313, and the insulating sheet 318 covering the entire top surface of the aquaculture water. The outer side walls 312 are made of bricks with a low thermal conductivity of 0.612 (W / m·k), and are double-layered with an insulating plate inserted between them, resulting in extremely low thermal conductivity. The bottom wall 314 is made of concrete with low thermal conductivity (1.6 (W / m·k)), the lid member is made of wood with very low thermal conductivity (0.12 to 0.19 (W / m·k)), and the insulating sheet 318 is also made of a material with extremely low thermal conductivity. Therefore, the aquaculture tank 310 has very high insulation performance and is configured to minimize heat loss to the outside.

[0115] If it is desired to maintain the temperature of the culture water in the culture tank 310 at, for example, 30°C, and the environmental temperature of the culture tank 310 (room temperature of the agricultural greenhouse) is 20 to 25°C throughout the year, the temperature of the culture water will gradually decrease to approach the environmental temperature (for example, 25°C). Heating will begin when the temperature of the culture water reaches a lower threshold temperature (for example, 27°C), and will end when the temperature of the culture water gradually rises to an upper threshold temperature (for example, 31°C).

[0116] In the fourth embodiment, heating is performed as follows. The air in the heating space 313 and the inner side wall 311 are heated by thermal radiation, conduction, and convection from the electric heater 315 installed in the heating space 313. The culture water is then efficiently heated by thermal conduction through the inner side wall 311. It should be noted that the air in the heating space 313 is heated. That is, the specific heat of water is 1 cal / °C, while the specific heat of air is 0.17 cal / °C. Therefore, air can be heated with less thermal energy than water. Furthermore, in the fourth embodiment, the inner side wall 311 is made of naval brass plate, which has a very high thermal conductivity (117 W / m·k), so the culture water is heated very efficiently. Furthermore, in the fourth embodiment, at least one fan 323 is installed in the heating space 313 to blow the air in a circumferential direction. Since at least one fan 323 is provided, the air in the heating space 313 is blown in the circumferential direction and heated evenly. Furthermore, in the fourth embodiment, the air in the air tube of the bubble release mechanism is heated by the air in the heating space 313 and thermal radiation and thermal conduction from the electric heater 315, and the heated air is released as fine bubbles into the culture water from the microbubble or fine bubble generating nozzle. Because the heated air is released into the culture water as fine bubbles with an astronomically large surface area for heat transfer, the culture water is heated extremely efficiently.

[0117] In a modification of the fourth embodiment, the outer side wall and the heating space 313 may be configured to be interrupted at a portion thereof rather than being continuous around the entire circumference of the tank, as in the first, second, and third embodiments. In this case, at least one fan 323 provided in the heating space 313 is configured to circulate and blow air in the heating space 313 in the vertical and circumferential directions. Furthermore, a kerosene heater, heavy oil heater, gas heater, firewood heater, coal heater, or other heaters may be used instead of the electric heater 315.

[0118] In a further modification of the fourth embodiment, the inner side wall 311 may be made of a plate of any metal material with high thermal conductivity, such as a copper alloy, an aluminum alloy, or an iron alloy, which is resistant to seawater, instead of naval brass.

[0119] In a modification of the fourth embodiment, the outer side wall 312 may be constructed of various materials with low thermal conductivity, such as mortar, concrete, or a wall made of locally produced stone such as Boso stone (Kanaya stone), instead of a brick wall.

[0120] In a further modification of the fourth embodiment, the bottom wall 314 can be constructed of a highly water-resistant and heat-insulating resin-based material or military-grade rubber material instead of concrete.

[0121] The outer side walls and bottom wall of the land-based aquaculture tank of the present invention can be formed using a 3D printer with mortar or concrete, which allows for the production of highly accurate outer side walls and bottom walls at low cost and in a short time.

[0122] For the land-based aquaculture tank of the present invention described above, a verification experiment was conducted to examine the relationship between the amount of energy consumption (electricity consumption) and the rise in water temperature when the aquaculture water was actually heated. The land-based aquaculture tank used for the measurement was the land-based aquaculture tank 110' of the modified version shown in Figure 9 of the second embodiment.

[0123] Generally, 200 m ３ The theoretical value of energy consumption when raising the temperature of water by 4°C (= ΔT) is (200m ３ ×998 kg / m ３ ) × 4.2 kJ / (kg × °C) × ΔT = 78,802,080 kJ (approximately 78 GJ). ３ The theoretical value of energy consumption when raising the temperature of water by 1°C Q Ｔ Is Q Ｔ = 78,802,080 kJ / 10 / 4 = 1,970,052 kJ (power consumption is about 546.9 kW). ３When the actual energy consumption Q required to increase the water temperature by 1°C was measured, it was found to be 25,200 kJ, and the power consumption in this case was approximately 7 kW. This corresponds to a power consumption of approximately 1.3% of the theoretical value, and according to this example, it is possible to increase the water temperature with extremely little power consumption.

[0124] In land-based aquaculture, it is known that the temperature of the culture water in the aquaculture tank 10 has a significant impact on the growth of the cultured organisms. For example, in shrimp farming, it is known that a difference of 4°C in culture water temperature between 23°C and 27°C results in a 2.8-fold increase in individual weight, and a difference of 6°C in culture water temperature between 23°C and 30°C results in a 4.1-fold increase in individual weight. According to this embodiment, the temperature of the culture water, which is closely related to growth, can be increased with extremely little power consumption, making it possible to effectively eliminate constraints imposed by the climatic and geographical conditions of the aquaculture site, and it has been found that this can greatly contribute to the growth of the new generation aquaculture industry.

[0125] The above-described embodiments, modifications, and examples are all illustrative of the present invention and are not limiting, and the present invention can be implemented in various other modified and altered forms. Therefore, the scope of the present invention is defined only by the claims and their equivalents.

[0126] The land-based aquaculture tank of the present invention can be applied not only to new land-based aquaculture tanks such as RAS, but also to general aquaculture tanks, and can also be applied to tanks other than aquaculture tanks, such as heated water tanks such as heated pools and bathtubs.

[0127] 10, 110, 110', 110", 210, 310 Aquaculture tank 11, 111, 111', 111", 211, 311 Inner side wall 12, 12', 112, 112', 212, 312 Outer side wall 12a, 12b Brick wall 12c Heat insulation board 13, 113, 213, 313 Heated space section 14, 114, 214, 314 Bottom wall 15, 115, 215, 315 Electric heater 16 Bubble release mechanism 16a Air blower 16b Air tube 16c Microbubble or fine bubble generating nozzle 16d, 16e Tube joint 17, 17', 217 Lid member 18, 118, 218, 318 Heat insulation sheet 19 Through-hole 20 Temperature sensor 21 Control device 111a" Metal corrugated plate member 111b" Resin sheet 123' Upper fixing metal fitting 123a', 124a' Arm portion 123b', 124b' Retaining portion 124' Lower fixing metal fitting 323 Fan

Claims

1. An on-land aquaculture tank comprising an inner side wall formed of a material with high thermal conductivity and containing aquaculture water inside; an outer side wall formed of a material with low thermal conductivity and surrounding the inner side wall at a distance so as to form a double structure; a heated space formed by the gap between the inner side wall and the outer side wall and filled with air; and a heater disposed within the heated space, wherein the inner side wall is heated by thermal radiation and thermal conduction from the heater, and the aquaculture water contained inside is heated.

2. An on-land aquaculture tank as described in claim 1, further comprising a bubble release mechanism that releases air heated by the air in the heating space as it passes through the heating space into the aquaculture water as bubbles.

3. An on-land aquaculture tank as described in claim 2, characterized in that the bubble release mechanism is a mechanism that releases the air heated by the air in the heating space as fine bubbles.

4. The land-based aquaculture tank according to claim 1, further comprising at least one fan provided within the heating space for circulating air within the heating space.

5. An on-land aquaculture tank as described in any one of claims 1 to 4, further comprising a lid member formed of a material with low thermal conductivity and sealing the upper surface of the heated space portion.

6. An on-land aquaculture tank as described in claim 5, characterized in that the cover member has at least one through hole, and the bubble release mechanism is configured to send air into the aquaculture water through the at least one through hole and release it as bubbles.

7. The land-based aquaculture tank according to claim 1, further comprising an insulating sheet made of a material with low thermal conductivity, which covers the upper surface of the aquaculture water.

8. The land-based aquaculture tank according to claim 1, further comprising a bottom wall covering the entire inner bottom surface of the outer side wall and made of a material with low thermal conductivity and waterproofing.

9. The land-based aquaculture tank described in claim 1, further comprising a temperature sensor for detecting the temperature of the aquaculture water, and a control device for controlling the operation of the heater in accordance with the temperature detected by the temperature sensor to adjust the temperature of the aquaculture water within a desired range.

10. The land-based aquaculture tank according to claim 1, characterized in that the inner side wall is formed using naval brass plates.

11. The land-based aquaculture tank according to claim 1, characterized in that the outer side walls are formed using brick walls or mortar walls.

12. The land-based aquaculture tank according to claim 1, characterized in that the outer side walls are formed using Styrofoam material.

13. The land-based aquaculture tank according to claim 1, characterized in that the outer side walls are formed using iron plates or galvalume steel plates covered with mortar fireproof material.

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