HEAT STORAGE SAUNA HEATER AND SAUNA CABIN

Description

[0001] The present invention relates to a heater for a sauna cabin (sauna storage heater, heat storage sauna heater) that can be operated independently of energy, without connection to the power grid, and without the use of fuels such as wood, gas, or oil. Furthermore, a sauna cabin using the heater according to the invention is described. Various approaches exist that propose a sauna heater that can be operated using renewable energy.

[0002] An obvious solution involves using photovoltaic systems combined with batteries, with the batteries providing the electricity to operate an electric heater for the sauna stove. However, this concept is complex, time-consuming, and expensive.

[0003] Furthermore, solutions are known that propose the use of solar cells to generate energy in sauna cabins. One example is DE10 2013 108 990 A1, which proposes such a solution as a secondary task, but does not disclose a detailed procedure.

[0004] JP 5 731 926 B2 proposes charging a water tank for a sauna using solar thermal energy, combined heat and power, or off-peak electricity. In addition to a heating function, the water tank should also have one or more nozzles for releasing steam.

[0005] DE 10 2018 003 136 A1 describes a sauna storage heater based on a pressurized water storage tank that is charged by a solar thermal collector. The disadvantage of this solution is the use of a pressure vessel (pressurized water storage tank). Such pressure vessels pose a potential danger if they are not properly maintained.

[0006] State-of-the-art solutions are particularly unsuitable for areas where there is no reliable power grid, no maintenance specialists or technical monitoring organizations.

[0007] The task, therefore, is to propose a sauna heater that combines simple construction, low maintenance, reliability, and manageable costs. The storage heater should also be able to heat the air in the sauna room to temperatures of up to 100°C when needed. The heat storage heater should be suitable for outdoor temperatures between -40°C and +50°C. Furthermore, a suitable sauna cabin design should be proposed. In the following, the terms "sauna" and "sauna cabin" are used synonymously.

[0008] According to the invention, the object is achieved with a sauna storage heater according to claim 1. The advantageous use of such a sauna heater in a sauna is disclosed in claim 15.

[0009] The sauna storage heater according to the invention has a heat storage container. The heat storage container contains a heat storage fluid. The heat storage fluid has a boiling point that, at atmospheric pressure, is above 100°C, preferably above 105°C, and most preferably above 120°C. The heat storage container has heat transfer fins on parts of the outer side of its wall that do not serve as a base. Preferably, no heat transfer fins are provided on the top surface of the heat storage container either. The heat transfer fins are preferably oriented vertically. A thermal insulation layer is arranged around the heat storage container and, by means of the heat transfer fins, spaced from the wall of the heat storage container. The base and top surfaces of the heat storage container are optionally completely or partially covered by a thermal insulation layer.

[0010] The heat storage tank is preferably made of stainless steel, steel with a corrosion-resistant coating, aluminum, or other materials that offer the necessary stability and good thermal conductivity. In one embodiment, the outer surface of the heat storage tank is made of a material with particularly good thermal conductivity, such as aluminum, while the base and top surfaces are made of materials with poor thermal conductivity. This serves to reduce heat loss.

[0011] In a simple design, the heat storage tank is made of welded stainless steel plates. Heat transfer fins, in the form of vertically running stainless steel strips, are welded to the outer wall (shell surface).

[0012] The heat storage container, and thus the entire sauna storage heater, preferably has a cuboid shape (preferably a cube). A cylindrical shape is also preferred. However, other shapes are also suitable, such as a pyramid or truncated cone. The sauna storage heater can thus be advantageously adapted to the available installation space. The sauna storage heater preferably stands directly on the floor. Optionally, support feet or a support frame are available.

[0013] Propylene glycol, a mixture of propylene glycol and water, or salt water, for example, is used as the heat storage fluid in the heat storage tank. When using salt water or similar heat storage fluids that are corrosive to the material of the heat storage tank or its internal components, the heat storage tank and its internal components (heat exchanger, heating element) are provided with a correspondingly resistant coating.

[0014] The thermal insulation layer consists of state-of-the-art thermal insulation materials. Suitable materials include fiberglass, glass wool, temperature-resistant plastic, mineral wool, high-temperature polyurethane foam, or similar thermal insulation materials also used in construction that meet the required thermal resistance.

[0015] For safety reasons, the heat storage tank is equipped with a pressure relief valve that prevents the buildup of excessive internal pressure. The pressure relief valve is preferably located on the top (cover surface) of the heat storage tank.

[0016] One or more air inlets are provided in the thermal insulation layer near the bottom ends of the heat transfer fins. One or more air outlets are provided in the thermal insulation layer near the top ends of the heat transfer fins. The air inlets and outlets are connected by channels formed by the wall of the heat storage tank, the thermal insulation, and the heat transfer fins.

[0017] This allows for air circulation, with the cool air flow entering the space between the wall of the heat storage tank and the thermal insulation layer through the air inlet openings, being heated by the wall of the heat storage tank and the heat transfer fins, and leaving the space warmed through the air outlet openings. Directing the air flow through the space creates a beneficial chimney effect, which supports the heat transfer from the heat storage tank.

[0018] In one embodiment, the thermal insulation layer is modular and removable. This advantageously allows the thermal insulation layer to be removed from the heat storage container and the channels of the sauna storage heater to be cleaned.

[0019] To control the heat discharge from the heat storage tank, closures of the air outlet openings and optionally also the air inlet openings are provided.

[0020] The closures are preferably known flaps or louvre closures. The closures of the air outlets, or optionally also the air inlets, can themselves be equipped with thermal insulation. Furthermore, these closures can be arranged two or more times in succession in the direction of air flow, so that an air flow that would dissipate heat at the outer closure is slowed down or stopped by additional closures arranged in front of it.

[0021] Preferably, the closures are operated purely mechanically. This eliminates the need for auxiliary power. If auxiliary power is available, electromechanical, electronic, or other actuation methods are also possible, including temperature-dependent control of the closure position.

[0022] Heat is preferably introduced into the heat storage tank by solar thermal charging. For this purpose, at least one solar thermal collector (solar collector) is provided, which has a heat transfer medium circulating in a charging circuit. The heat transfer medium absorbs heat in the solar thermal collector and transfers it to the heat storage fluid of the heat storage tank via a heat exchanger located inside the heat storage tank. Of course, multiple solar collectors, charging circuits, and heat exchangers can be provided.

[0023] The circulation of the heat transfer medium in the loading circuit is either pump-driven (if auxiliary energy is available) or, preferably, due to the developing thermal circulation.

[0024] In one embodiment, the pipes of the charging circuit can be shut off individually or collectively near their exit from the thermal insulation layer of the heat storage tank to prevent unwanted discharge circulation within the circuit or single-pipe circulation during the night. Optionally, a Z-shaped siphon is also provided for each pipe to suppress single-pipe circulation.

[0025] Another option, which can be used either as an alternative to or in combination with solar thermal charging, is charging with photovoltaic energy. One or more electrical heating elements (resistance heaters) are then provided inside the heat storage tank, either as an alternative to or in combination with the heat exchanger. Energy is generated using one or more photovoltaic collectors. The heat exchanger, for transferring heat to the heat storage fluid in the heat storage tank, is preferably located in the lower third of the heat storage tank. This also applies to any heating element for photovoltaic charging of the heat storage tank.

[0026] In one embodiment, the photovoltaically generated energy serves only as auxiliary energy and not, or only partially, for thermally charging the heat storage tank. The photovoltaically generated energy can optionally be temporarily stored in a battery for this purpose. The generated auxiliary energy can, for example, be used to power a circulation pump for the heat transfer medium of the solar thermal circuit to charge the heat storage tank. Furthermore, the drive or control of the closures for the air outlet openings and, optionally, the air inlet openings, as well as the sauna cabin lighting, can also be operated with the auxiliary energy.

[0027] By using propylene glycol or a mixture of 90% propylene glycol and 10% water, the need for a pressure vessel is eliminated, allowing the advantageous use of a pressureless heat storage vessel. Propylene glycol is harmless to health, is used in aviation as a de-icing agent, and does not cause soil contamination in the event of a spill.

[0028] The heat storage sauna heater according to the invention advantageously combines a heat storage unit and a heating element in one device. This eliminates the need for a separate heating element for transferring heat to the sauna room. The installation of heat transfer fins on the outer wall of the heat storage container advantageously enables a compact design and reduced space requirements.

[0029] The heat output is advantageously designed to be switchable. The heat transfer from the sauna heater to the sauna room, preferably via a lever, through a manually or electronically operated flap or louvre system, enables a more robust construction than the state of the art and eliminates the need for circulation pumps and the like.

[0030] It is also within the scope of the invention to optionally monitor the load status of the heat storage sauna heater using thermal sensors, transmit it to the user via mobile phone or the Internet, and display it via an app. The app can also optionally be used to remotely control the sauna heater.

[0031] The sauna cabin according to the invention utilizes the heat storage sauna heater (sauna heater) described above. In some embodiments, the sauna cabin is designed as a Finnish sauna. By additionally installing an infusion heater, the infusion typical of Finnish saunas can be realized. However, it is also within the scope of the present invention to configure the sauna cabin as a hammam or steam sauna by operating the heat storage sauna heater at lower temperatures and generating high humidity by additionally installing a steam generator.

[0032] In a first embodiment, the sauna heater is installed in a sauna cabin nominally designed for four people. The compact dimensions of the sauna heater and the space-saving arrangement of the two sauna benches make it possible to significantly reduce the external dimensions of the sauna cabin. This enables easy transport and use even in more remote areas. The dimensions of the sauna cabin are preferably selected so that the entire sauna cabin can be transported in standard containers. The sauna cabin preferably has a rigid supporting frame that holds the sauna walls, ceiling, and floor. The supporting frame can be made, for example, from steel double-T beams. Optionally, the supporting frame has attachment points for crane hooks or threads for screwing in attachment eyes for crane hooks. This advantageously enables easy handling or relocation of the sauna cabin.

[0033] The one or more solar thermal and / or photovoltaic collectors are preferably arranged on the roof of the sauna cabin. Of course, an additional or alternative arrangement of the solar thermal and / or photovoltaic collectors next to the sauna or on a separate auxiliary frame is also possible. The dimensions of the solar collectors or solar cells, as well as the pipes for the heat transfer medium, are preferably selected so that the components can be stored in the sauna cabin during transport. The container with the heat transfer medium is also preferably housed in the sauna cabin during transport. In this way, prefabricated sauna cabins can be advantageously provided with all the materials necessary for installation and operation.

[0034] In one embodiment, the sauna cabin has an indicator on its exterior that indicates whether the sauna storage heater is sufficiently charged with heat energy and / or whether the sauna cabin is currently in use. This can be achieved, for example, by using one or more rows of LEDs on the outer edges of the sauna cabin, which light up or flash in different colors (e.g., heat storage charged - red, heat storage discharged - blue, optionally with the respective color component of the LED row depending on the charging level of the sauna storage heater). This indicator can optionally be operated using the auxiliary energy, which is also used to control the locking position or operate the circulation pump.

[0035] In further embodiments, multiple sauna storage heaters are arranged in a sauna cabin for larger groups of people. Scaling the use of the sauna storage heater according to the invention is possible, alternatively or in addition to varying the number of sauna storage heaters used, by adjusting the size of the sauna storage heaters used. Since larger sauna cabins usually also require a larger roof area, the installation of additional and / or larger solar thermal collectors on the roof is possible. Examples of implementation

[0036] The invention will be explained in more detail below using an embodiment and drawings: Fig. 1 shows schematically the heat storage furnace 1 according to the invention in a vertical sectional view. Fig. 2 shows schematically the structure of a cylindrical heat storage furnace 1 in a horizontal sectional view. Fig. 3shows schematically the sauna cabin according to the invention in a vertical sectional view. Fig. 4 shows schematically the sauna cabin according to the invention in a horizontal sectional view.

[0037] The following example is based on a small sauna 20 with heat storage heater 1 for four people with a heating requirement of approximately 4 kW and a thermal energy storage capacity of between 10 kWh and 20 kWh for one sauna evening (corresponding to approximately 3-5 hours of use).

[0038] The heat storage tank 12 for the heat storage fluid 2 is cylindrical, 1 m high, 0.6 m in diameter, and constructed of pressureless stainless steel sheet. It thus has a capacity of over 300 liters. The side surface area is just under 2 m².

[0039] Fifty 2 mm thick aluminum sheets are attached to the outer wall of the heat storage tank 12, spaced approximately four centimeters apart, as heat transfer fins 3. Each sheet is 1 m long and 0.1 m wide. Thus, the total heat transfer surface area is more than 10 m² and, in the case of an average temperature drop of 20 K between the incoming cold air stream 10 to be heated and the heat storage fluid 2, ensures the above-specified heat flow of 4 kW in the hot air stream 11.

[0040] The heat storage container 12 is protected externally by a commercially available thermal insulation jacket 4 (mineral wool) with a thickness of 0.1 m. With an effective thermal conductivity of the thermal insulation material 4 of 0.1 W / mK, a maximum temperature difference of 100 K between the hot heat storage fluid 2 (120°C) and the cold sauna interior air (20°C), and an outer surface of the thermal insulation material 4 of 3 m2, the worst-case scenario for a fully thermally loaded heat storage sauna heater 1 results in a heat loss of 300 W, which is sufficiently small for the necessary insulation task.

[0041] By manually operating a flap mechanism 5, 6, which is mounted on the upper (and optionally also on the lower) edge of the heat storage sauna heater 1, the vertical flow channels 13 between the heat transfer fins 3 open, allowing the air to be heated. It is, of course, also within the scope of the invention to operate the mechanism electronically.

[0042] The heating (charging with thermal energy) of the heat storage fluid 2 can be achieved either by means of an electric heating coil 8 coupled to the photovoltaic system in the lower part of the heat storage tank 12 or by means of a heat exchanger 7 for the solar-thermally heated heat transfer fluid from the solar-thermal system (solar collector 23 and pipes 25). It is of course also within the scope of the invention to combine both heating methods and to heat the heat storage sauna heater 1 in a hybrid manner. Thus, in the absence of direct solar radiation (where the solar-thermal system hardly provides any heat), the photovoltaic system (not shown) could provide at least a certain amount of heat. In contrast, with a high proportion of direct solar radiation 24, the solar-thermal system 23, 25 would provide the majority of the heat.In this way, the advantages of the two heating technologies (photovoltaic yield even in hazy weather, solar thermal energy - good efficiency in direct radiation) could be combined.

[0043] For solar thermal loading of the heat storage furnace 1 over a day, an area of 5 m2< must be provided for the solar collectors.

[0044] The sauna heater 1 is arranged in a sauna cabin 20, which is nominally designed for four people. The sauna cabin 20 is entered through the door 26. Due to the compact dimensions of the sauna heater 1 and the space-saving arrangement of the two sauna benches 22, it is possible to reduce the external dimensions of the sauna cabin 1 so that two sauna cabins 1 fit into an international 20-foot standard container. This results in maximum external dimensions (W x L x H) of 2.35 x 2.80 x 2.30 m for the sauna cabin 1. The sauna cabin 1 has a cuboid steel frame made of double-T beams that runs along the outer edges of the sauna cabin 1. The sauna cabin 1 is lined on the inside and outside with surface-treated wooden boards. A 10 cm thick mineral wool thermal insulation layer is provided in the wall 21 between the inside and outside.The steel frame is exposed at the upper corners of sauna cabin 1 and has a threaded opening at each corner for eyelets for attaching crane ropes (not shown). Reference symbol

[0045] 1Heat storage heater (total) 2Heat storage fluid 3Heat transfer structures 4Heat insulation 5Flap system 6Flap actuator 7Thermal heat supply element 8Electrical heat supply element 9Safety valve 10Cold air flow 11Hot air flow 12Heat storage tank 13Air flow channels 20Sauna cabin 21Sauna cabin wall 22Sauna bench 23Solar collector 24Incident solar radiation 25Pipes of the solar thermal circuit 26Sauna cabin door

Claims

1. Sauna heater, comprising a heat storage container (12) with a heat storage fluid (2), characterized in that - the boiling temperature of the heat storage fluid (2) at normal pressure is above 100°C, preferably above 105°C and most preferably above 120°C, - at least one heat exchanger (7) and / or at least one heating element (8) is arranged in the lower third of the heat storage container (12), - the heat storage container (12) has heat transfer ribs (3) at least on parts of the outer side of its wall, - a thermal insulation layer (4) is arranged around the heat storage container (12) and spaced from the wall of the heat storage container (12) by means of the heat transfer ribs (3), - at least one air outlet opening is provided in the thermal insulation layer (4) in the region of the upper ends of the heat transfer ribs (3), - in the region of the lower ends of the heat transfer ribs (3) at least one air inlet opening is provided in the thermal insulation layer (4), wherein the air inlet and air outlet openings are connected by channels (13) formed by the wall of the heat storage container (12), the thermal insulation layer (4) and the heat transfer ribs (3).

2. Sauna heater according to claim 1, characterized in that the air outlet openings and optionally also the air inlet openings are designed to be closable.

3. Sauna heater according to one of the preceding claims, characterized in that the closing of the air outlet or air inlet openings is done manually or electrically.

4. Sauna heater according to one of the claims 2 or 3, characterized in that the closures of the air outlet or air inlet openings are arranged two or more times in succession in the direction of air flow and / or in that the closures of the air outlet or air inlet openings are provided with thermal insulation.

5. Sauna heater to one of the preceding claims, characterized in that the heat storage container (12) has a cuboid shape, preferably a cube shape, a cylinder shape or the shape of a pyramid or truncated cone and / or that the heat storage container (12) has a pressure relief valve (9).

6. Sauna heater according to one of the preceding claims, characterized in that the standing surface and the top surface of the heat storage container (12) are completely or partially covered by a thermal insulation layer (4).

7. Sauna heater according to one of the preceding claims, characterized in that the thermal insulation layer (4) is designed to be removable.

8. Sauna heater according to one of the preceding claims, characterized in that the heat exchanger charges the heat storage container (12) with thermal energy through a solar thermal circuit (23, 25) and / or that the heating element (8) charges the heat storage container (12) with thermal energy through a photovoltaically powered electrical circuit.

9. Sauna heater according to one of the preceding claims, characterized in that the heat transfer medium (2) is propylene glycol, a mixture of propylene glycol with water or salt water.

10. Sauna heater according to one of the preceding claims, characterized in that the sauna heater has at least one battery and associated control electronics to enable photovoltaic charging of at least one battery.

11. Sauna heater according to claim 10, characterized in that the sauna heater further comprises a transmitting and receiving module for wirelessly controlling the sauna heater and the air inlet and outlet openings.

12. Sauna heater according to claims 10 or 11, characterized in that a circulation pump for circulating the heat transfer medium (2) of the solar thermal circuit (23, 25) is driven by means of the electrical energy of the batteries.

13. Sauna cabin with a sauna heater according to one of claims 1 to 12, characterized in that the one or more solar thermal and / or photovoltaic collectors (23) are arranged on the roof of the sauna cabin (20).

14. Sauna cabin according to claim 13, characterized in that the sauna cabin (20) has a display on its outside which signals whether the sauna storage heater (1) is sufficiently loaded with thermal energy and / or whether the sauna cabin (20) is currently in use.

15. Use of a sauna heater according to one of the claims 1 to 12 in a sauna cabin (20).