Transportable air treating system and air treating method

Abstract

The invention relates to a transportable air treating system and method to heat, to cool, or to dry air within a construction The system comprises one or more air source heat pumps, a transportable housing comprising an indoor compartment and an outdoor compartment, one or more inlet air ducts configured to convey incoming air from the construction to the system, and one or more outlet air ducts configured to return treated air from each of the one or more air source heat pumps to the construction.

Description

[0001] Transportable air treating system and air treating method

[0002] Technical field

[0003] The invention relates to transportable air treating systems and methods for treating air using said transportable air treating systems. Particularly, the invention relates to heating, to cooling or to drying air within a construction.

[0004] During the construction of a building, the construction site often needs to be heated. Especially in countries where the temperature falls below freezing, heating of construction sites and unfinished buildings improves the working comfort and working safety of the construction workers. Moreover, materials and methods used at the construction sites often require dry and warm enough conditions for an adequate finish, e.g., concreting and surface treatment, such as painting.

[0005] Conventionally, heating of construction sites or, e.g., temporary constructions such as festival tents is carried out by using fuel-driven heaters, such as indirect oil heaters. These devices produce heat by combusting fossil fuels or biofuels and produce carbon emissions. Even though biofuel-compatible heaters exist, there is a need for completely carbon-free alternatives to reduce the carbon footprint of construction processes.

[0006] Moreover, these devices cannot provide cooling.

[0007] An object of the invention is to overcome the drawbacks associated with the conventional solutions.

[0008] Particularly, an object of the invention is to provide air treating systems that provide heating, cooling and air drying functionalities in a single system. A further object of the invention is to provide air treating systems that are free from carbon emissions.

[0009] A yet further object of the invention is to provide air treating systems that are easily transportable.

[0010] The features recited in the dependent claims and the embodiments in the description are mutually freely combinable unless otherwise explicitly stated.

[0011] The exemplary embodiments presented in this text and their advantages relate by applicable parts to all aspects of the invention, both to the system and to the method, even though this is not always explicitly mentioned.

[0012] Particularly, a transportable air treating system for treating air to heat, to cool, or to dry air within a construction is provided.

[0013] The transportable air treating system comprises one or more air source heat pumps, wherein each air source heat pump of the one or more air source heat pumps comprises an indoor unit and an outdoor unit.

[0014] The transportable air treating system comprises a transportable housing comprising an indoor compartment and an outdoor compartment. The outdoor compartment is in contact with an outside environment surrounding the system, i.e., surrounding air. This allows the outdoor units of the one or more air source heat pumps to transfer heat to and from the environment surrounding the system, i.e., directly to and from the surrounding air. The indoor compartment comprises a thermal insulation layer to thermally insulate the indoor compartment from the outside environment surrounding the system.

[0015] The transportable housing is configured to receive the one or more air source heat pumps such that the indoor unit of each air source heat pump of the one or more air source heat pumps is arranged in the indoor compartment of the transportable housing and the outdoor unit of each of the one or more air source heat pumps is arranged in the outdoor compartment of the transportable housing. The transportable air treating system comprises one or more inlet air ducts configured to convey incoming air from the construction to the system.

[0016] In the transportable air treating system, each air source heat pump of the one or more air source heat pumps is configured to circulate the incoming air through the indoor unit to produce treated air at a predetermined outlet air temperature. Each air source heat pump of the one or more air source heat pumps is also configured to transfer heat from the incoming air to the indoor unit and further to the outdoor unit, or from the outdoor unit to the indoor unit and further to the incoming air. The heat is transferred between the indoor unit and the outdoor unit of each air source heat pump by means of a heat carrier.

[0017] The transportable air treating system comprises one or more outlet air ducts configured to return the treated air from each indoor unit of the one or more air source heat pumps to the construction.

[0018] The thermal insulation layer in the indoor compartment of the transportable housing ensures an efficient heat transfer between the indoor unit and the outdoor unit. The outdoor unit of each of the one or more air source heat pumps is in direct contact with the environment surrounding the system, i.e., the outdoor unit experiences the outside temperature. For the heat pump to function properly, the indoor unit should be at a temperature substantially similar to the interior of the construction. Without the thermal insulation layer, the heat to be transferred from the indoor unit to the outdoor unit, or vice versa, would leak into the surrounding environment, which would be detrimental to the efficiency of the air treating system.

[0019] A method for treating air to heat, to cool, or to dry air within a construction is also provided.

[0020] The method comprises conveying incoming air from the construction to the system through the one or more inlet air ducts.

[0021] The method further comprises treating the incoming air using the one or more air source heat pumps by transferring heat from the incoming air to the indoor unit and further to the outdoor unit, or from the outdoor unit to the indoor unit and further to the incoming air. The heat is transferred by means of a heat carrier, thus producing treated air at the predetermined outlet air temperature.

[0022] The method further comprises returning the treated air from each indoor unit of the one or more air source heat pumps to the construction through the one or more outlet air ducts.

[0023] The present system and method have several advantages over conventional transportable heaters.

[0024] The air source heat pumps used in the presented system and method are electricity-driven. Thus, air treatment may be provided with zero carbon emissions.

[0025] The present system can provide cooling or air drying functionalities in addition to heating. Thus, the system is more versatile and its utilization rates may be increased compared to heating-only devices.

[0026] The present system is easily transportable by, e.g., trucks. Thus, the system can be brought into a desired location and is suitable for temporary use. In addition to construction sites, the system and method are usable in public events to heat or cool temporary event site constructions, such as marquees, exhibition tents or festival tents.

[0027] Brief of the

[0028] Figure 1 schematically presents an air treating system according to the invention;

[0029] Figure 2 schematically presents an air treating system comprising

[0030] 3 air source heat pumps;

[0031] Figures 3a-b schematically present air treating systems with different orientations of the one or more inlet air ducts;

[0032] Figures 4a-c schematically present air treating systems comprising a heater; and

[0033] Figures 5a-b schematically present air treating systems comprising one or more particle filters. Detailed description

[0034] The following reference numerals will be referred to in this application:

[0035] 100 transportable air treating system

[0036] 101 indoor unit of air source heat pump

[0037] 102 outdoor unit of air source heat pump

[0038] 103 heat carrier

[0039] 110 transportable housing

[0040] 111 indoor compartment of transportable housing

[0041] 112 outdoor compartment of transportable housing

[0042] 113 thermal insulation layer

[0043] 120 inlet air duct

[0044] 130 outlet air duct

[0045] 140 controller

[0046] 150 heater

[0047] 160 particle filter

[0048] 200 construction

[0049] Figure 1 presents a transportable air treating system 100 treating air to heat, to cool, or to dry air within a construction 200. The system comprises one or more air source heat pumps. Each air source heat pump of the one or more air source heat pumps comprises an indoor 101 unit and an outdoor unit 102.

[0050] The construction 200 may be any stationary or temporary construction, a construction site, or the like. Examples of constructions 200 where the system 100 is suitable for use include, but are not limited to, construction sites, such as unfinished buildings, temporary constructions such as tarpaulin or canvas constructions, e.g., marquees, exhibition tents, festival tents, or construction site covers, or any stationary constructions or buildings where temporary or transportable air treating systems are needed.

[0051] Referring to Figure 1 , the system comprises a transportable housing 110. The transportable housing comprises an indoor compartment 111 and an outdoor compartment 112. The outdoor compartment 112 is in contact with an outside environment surrounding the system 100. The indoor compartment 111 comprises a thermal insulation layer 113 to thermally insulate the indoor compartment 111 from the outside environment surrounding the system 100. The transportable housing 110 is configured to receive the one or more air source heat pumps. The indoor unit 101 of each air source heat pump of the one or more air source heat pumps is arranged in the indoor compartment 111 of the transportable housing 110 and the outdoor unit 102 of each of the one or more air source heat pumps is arranged in the outdoor compartment 112 of the transportable housing 110.

[0052] The indoor compartment 111 and the outdoor compartment 112 of the transportable housing 110 may be arranged either as separate structures or they may be arranged as one structural entity.

[0053] Preferably, the transportable housing 110 is arranged as one structural entity, such that the indoor compartment 111 and the outdoor compartment 112 share the same load-bearing structure. This allows the housing 110 to be transported as one unit and also enables a permanent assembly of the indoor unit 102 and the outdoor unit 102 of each of the one or more air source heat pumps within the transportable housing 110. In other words, the housing 110 may be transported while the indoor unit 101 and the outdoor unit 102 of each of the one or more air source heat pumps may remain assembled within the housing 110 enabling quick and easy installation of the system 100 at the desired location of use, i.e., adjacent to the construction 200.

[0054] The one or more air source heat pumps may preferably be air-to-air heat pumps. Air-to-air heat pumps may be compact in size while still providing efficient heat transfer. Thus, air-to-air heat pumps may be conveniently and efficiently arranged within the transportable housing 110, facilitating easy transportation of the system. Air-to-air heat pumps may also be conveniently permanently assembled, with very little assembly work needed after transporting the system 100 into the location of use. Systems utilizing air-to- air heat pumps may be particularly suitable for constructions without an existing heat distribution system, such as construction sites, temporary constructions or construction site covers.

[0055] The one or more air source heat pumps may be digital inverter type air source heat pumps. Other heat pump technologies may also be used. Nominal heat transfer capacity of each of the one or more air source heat pumps may be in the range of 10 to 50 kW, such as 15 to 30 kW or 20 to 30 kW. Each air source heat pump may have a heating capacity of 3 to 50 kW and a cooling capacity of 3 to 40 kW. The actual heating and cooling capacities of the one or more air source heat pumps depend on the temperature difference between the construction to be cooled or heated and the outside environment.

[0056] The system 100 may comprise 2 to 5 air source heat pumps. Each air source heat pump of the 2 to 5 air source heat pumps comprises an indoor unit 101 and an outdoor unit 102. The system 100 may comprise, e.g., 2 heat pumps, 3 heat pumps, 4 heat pumps, or 5 heat pumps. Figure 2 presents an air treating system 100 comprising 3 air source heat pumps. Each air source heat pump comprises an indoor unit 101 and an outdoor unit 102. By equipping the system with 2 to 5 air source heat pumps, the total heat transfer capacity of the system may be increased compared to a single heat pump system.

[0057] The system 100 may have a nominal heat transfer capacity of at least 10 kW, such as at least 20 kW or at least 50 kW, such as in the range of 10 to 200 kW, 20 to 180 kW or 80 to 160 kW depending on the number of air source heat pumps, and on whether the system comprises the heater 150. The nominal heat transfer capacity of the system may be defined as the sum of the nominal heat transfer capacities of each of the one or more air source heat pumps and the optional heater 150.

[0058] Each air source heat pump of the one or more air source heat pumps typically have an air circulation capacity in the range of 2000 to 10 000 m3 / h, such as 3000 to 8000 m3 / h. The system 100 may have an air circulation capacity in the range of 2000 to 30 000 m3 / h, such as 5000 to 20 000 m3 / h.

[0059] Referring to Figure 1 , the system 100 may comprise one or more inlet air ducts 120. The one or more inlet air ducts 120 are configured to convey incoming air AIR1 from the construction 200 to the system 100 to be treated by the system 100. Each inlet air duct 120 has an inlet opening that is arranged within the construction 200 when in use. The incoming air AIR1 is sucked into each inlet air duct 120 through the inlet opening. The one or more inlet air ducts 120 may be arranged to convey the incoming air AIR1 to an interior space of the indoor compartment 111 , as schematically presented in Figure 3a.

[0060] Alternatively or in addition, the one or more inlet air ducts 120 may be arranged to convey the incoming air AIR1 directly to the indoor unit 101 of each of the one or more air source heat pumps, as schematically presented in Figure 3b. Conveniently, the number of inlet air ducts 120 is identical to the number of air source heat pumps, such that each of the one or more inlet air ducts 120 conveys incoming air AIR1 to each indoor unit 101 of the one or more air source heat pumps.

[0061] Each air source heat pump of the one or more air source heat pumps is configured to circulate the incoming air AIR1 through the indoor unit 101 to produce treated air AIR2 at a predetermined outlet air temperature TOUT.

[0062] Each air source heat pump of the one or more air source heat pumps may be further configured to transfer heat i) from the incoming air AIR1 to the indoor unit 101 and further to the outdoor unit 102, or ii) from the outdoor unit 102 to the indoor unit 101 and further to the incoming air AIR1 .

[0063] Regarding the heat transfer option i), an air-to-air heat pump may be configured to transfer heat from the incoming air AIR1 to the indoor unit 101 , to the outdoor unit 102, and further directly to the surrounding air (i.e., to the environment surrounding the system). Likewise, in the heat transfer option ii), the air-to-air heat pump may be configured to transfer heat directly from the surrounding air into the outdoor unit 102, to the indoor unit 101 and further to the incoming air AIR1.

[0064] The heat transfer in option i) produces cooled air, whereby the predetermined outlet air temperature TOUT of the treated air AIR2 is lower than temperature TIN of the incoming air AIR1 , referring to a cooling mode of the system. In the cooling mode, heat is transferred from the incoming air to the outdoor unit 102 of each of the air source heat pumps, and further to the environment surrounding the system. In other words, the one or more air source heat pumps are configured to cool the incoming air AIR1 by extracting heat into the heat carrier and further to the environment surrounding the system. The cooling mode may have two operational profiles: cooling and drying. When cooling, lamellae within the indoor unit 102 of each of the air source heat pumps cool down to temperatures close to 0°C, such as 0 to 5°C, and operation of the air source heat pump is controlled by means of a thermostat to stop cooling when a target air temperature has been reached. When drying, the lamellae are cooled down to the dew point of water while cooling the air, causing condensation of water on the surface of the lamellae within the indoor unit 102, thereby reducing the amount of water vapor in the air and thus drying the air.

[0065] The heat transfer in option ii) produces heated air, whereby the predetermined outlet air temperature TOUT of the treated air AIR2 is higher than the temperature TIN of the incoming air AIR1 , referring to a heating mode of the system. In the heating mode, heat is transferred from the environment surrounding the system and further to the incoming air AIR1 through the outdoor unit 102 and the indoor unit 101 of each of the air source heat pumps by means of the heat carrier. In other words, the one or more air source heat pumps are configured to heat the incoming air AIR1 with heat energy extracted from the surrounding environment.

[0066] The heat transfer is carried out by means of a heat carrier 103. The heat carrier 103 may be selected from heat carriers, i.e., refrigerants, that comply with the Ell regulation 2024 / 573, such as R32, R290, R744, or any combination thereof.

[0067] Referring back to Figure 1 , the system 100 typically comprises one or more outlet air ducts 130. The one or more outlet air ducts 130 are configured to return the treated air AIR2 from each indoor unit 101 of the one or more air source heat pumps to the construction 200. Each outlet air duct 130 of the one or more outlet air ducts 130 is typically arranged in contact with outlet of each indoor unit 101 of the one or more air source heat pumps. Thus, the number of the outlet air ducts 130 is conveniently identical to the number of air source heat pumps.

[0068] The one or more inlet air ducts 120 and one or more outlet air ducts 130 may be thermally insulated from the surrounding environment to minimize heat losses in the air ducts, thus increasing the heat transfer efficiency of the system.

[0069] The thermal insulation layer 113 as well as the thermal insulation of the one or more inlet air ducts 120 and the one or more outlet air ducts 130 may independently be selected from the group comprising glass wool, cellulose such as wood fiber, rock wool, polystyrene foam, urethane foam, vermiculite, perlite, cork, and any combination thereof.

[0070] Referring to Figure 1 , the system may further comprise a controller 140. The controller 140 is operatively connected to the one or more air source heat pumps. The controller 140 is configured to control the operation of the one or more air source heat pumps according to at least one of the following: the predetermined outlet air temperature TOUT, inlet air temperature TIN, target air temperature TT inside the construction 200, present air temperature TPRES inside the construction 200, temperature difference TDIFF between the target air temperature TT and the present air temperature TPRES, outside temperature TEXT, and required heating power capacity PH. The controller 140 is typically configured to independently control the operation of the indoor unit 101 and the operation of the outdoor unit 102 of the one or more air source heat pumps.

[0071] The controller 140 may comprise a control unit configured to perform one more controlling tasks by executing a computer program code being stored on a memory. The controller 140 may further comprise a user interface configured to display information and to receive commands from the user. The controller 140 may further comprise a digital communication unit, for example, over a wired or wireless connection. Examples of the connections comprise field bus technologies such as Profibus, Scanbus, Internet Protocol and Ethernet connections.

[0072] The controller 140 provides accurate control of the outlet air temperature TOUT. Thus, the desired target air temperature TT within the construction 200 may be accurately determined according to heating or cooling needs, or needs to dry the air within the construction.

[0073] The predetermined outlet air temperature TOUT is the temperature of the treated air AIR2 when returned to the construction 200, i.e., the temperature of air being discharged to the construction 200 from the one or more outlet air ducts 130.

[0074] The inlet air temperature TIN is the temperature of incoming air AIR1 entering the system 100, i.e., the temperature of air at the inlet openings of each of the one or more inlet air ducts 120.

[0075] The target air temperature TT is a predetermined target temperature value for air inside the construction 200. The target air temperature TT may be selected as desired by the user. The target air temperature TT inside the construction 200 is typically selected in the range of 10°C to 25°C to provide comfortable circumstances for the user inside the construction 200. For example in construction work, working safety regulations typically require that the temperature inside the building under construction does not exceed 25°C, and the relative humidity RH does not exceed 50%.

[0076] The present air temperature TPRES is the temperature of air at any given moment inside the construction 200. Typically, the present air temperature TPRES is very close to or substantially equal to the inlet air temperature TIN.

[0077] The temperature difference TDIFF is the temperature difference between the target air temperature TT and the present air temperature TPRES, defined as TDIFF = |TT- TPRES| . During hot days, the system is typically used in the cooling mode, and the target air temperature TT is lower than the present air temperature TPRES. Conversely, during cold days, the system is conveniently used in the heating mode, and the target air temperature TT is higher than the present air temperature TPRES.

[0078] The system 100 may further comprise a heater 150. The heater 150 may be configured to heat air inside the indoor compartment 111 of the transportable housing 110. The heater 150 is typically arranged within the indoor compartment 111 of the transportable housing 110.

[0079] Nominal heat transfer capacity of the heater 150 may be equal to or higher than the sum of the nominal heat transfer capacities of the one or more air source heat pumps. In systems comprising one air source heat pump, the nominal heat transfer capacity of the heater may be equal to or higher than the nominal heat transfer capacity of the air source heat pump.

[0080] The heater 150 may extend the utilizable temperature range of the system when used for heating. The actual heat transfer capacity of air source heat pumps naturally decreases when the outside temperature TEXT decreases. For example at -20°C, the nominal heating capacity of an air source heat pump may drop to 30% of the nominal heating capacity at +15°C, or even less. Thus, the use of heat pumps alone cannot fulfil heating needs at cold temperatures. The heater 150 can provide the additional heat required to reach the predetermined outlet air temperature TOUT. The heater 150 may thus complement the one or more air source heat pumps with its constant heating capacity even at low outside temperatures.

[0081] The heater 150 may also extend the lifetime of the one or more air source heat pumps in the system 100. As the one or more air source heat pumps are typically digital inverter heat pumps, their principle of operation is to aim for the outlet air temperature TOUT. Therefore, at cold outside temperatures, the one or more heat pumps would run constantly when trying to reach the outlet air temperature TOUT, without ever reaching it due to the lowered heating capacity caused by the cold outside temperature TEXT. This constant running of the one or more heat pumps will rapidly deteriorate their performance, drastically decrease their lifetime and cause enormous replacement costs. The heater 150 assists in heating the air, whereby the one or more heat pumps may be operated at a lower power level, thus reducing their load and extending their lifetime. The need for heat within the construction is thereby mostly covered by the heater 150 at outside temperatures below a critical outside temperature Tc, and the one or more heat pumps are mainly used for air circulation.

[0082] The one or more heat pumps may be operated at a capacity of, e.g., 0 to 10% of their maximum capacity, such as at a capacity of 5 to 8% of their maximum capacity, when the outside temperature falls below a critical outside temperature Tc. At temperatures below the critical outside temperature Tc, one or more outdoor units 102 of may even be switched off, whereby the one or more indoor units 101 may be used for air circulation without providing any heating. In this scenario, the heater 150 is the primary source of heat in the treated air AIR2. The critical outside temperature Tc may be selected in the range of -18°C to -30°C, preferably in the range of -20°c to -25°C.

[0083] The heater 150 may be arranged in an interior space of the indoor compartment 111 of the transportable housing 110, as schematically presented in Figure 4a or within the one or more inlet air ducts 120, as schematically presented in Figure 4b. In this arrangement, the incoming air AIR1 may be pre-heated before entering the indoor unit 101 .

[0084] The heater 150 may be arranged within the one or more outlet air ducts 130, as schematically presented in Figure 4c. In this arrangement, air exiting the indoor unit 101 of the one or more air source heat pumps may be heated, thus providing the treated air AIR2. This arrangement enables convenient heating of only air exiting the one or more air source heat pumps that is to be returned to the construction 200, minimizing heat losses in the air ducts.

[0085] The heater 150 may be an electric heater configured to convert electrical energy into heat. Electric heaters do not produce carbon dioxide emissions, whereby they are well suitable for use in the system presented herein. Electric heaters have a high electric-to-heat efficiency, they are compact in size and they do not require any other input arrangements besides an electrical connection, making them easy to install within the presented system.

[0086] The heater 150 may be a combustion heater configured to produce heat through combustion of a fuel. The fuel used by the combustion heater may be selected from renewable fuel, fossil fuel, and a combination thereof. The renewable fuel may be selected from a group comprising vegetable oils, biodiesel, biomethanol, bioethanol, biogas, synthetic fuels, such as electrofuels, and biomass, such as wood, e.g., pellets. The fossil fuel may be selected from natural gas, petroleum, and coal. Combustion heaters may conveniently be used within the presented system. When using a renewable fuel, the combustion heater may be carbon-neutral. Combustion heaters may easily provide the additional heating power required at a cold climate, and they may be operated without major modifications to the system.

[0087] When the system 100 comprises the heater 150, the controller 140 is further configured to control operation of the heater 150. Thus, the heater 150 is configured to be jointly controlled by the controller 140 with the operation of the one or more air source heat pumps. The heater operation is controlled according to at least one of the following: the predetermined outlet air temperature TOUT, inlet air temperature TIN, target air temperature TT inside the construction 200, present air temperature TPRES inside the construction 200, temperature difference TDIFF between the target air temperature TT and the present air temperature TPRES, outside temperature TEXT, and required heating power capacity PH.

[0088] The heater is 150 is configured to be used in addition to the one or more air source heat pumps to heat the incoming air AIR1 to produce the treated air AIR2, if the required heating power capacity PH exceeds the maximum heating capacity of the one or more air source heat pumps. The one or more outlet air ducts 130 are then configured to convey, or return, the heated, treated air AIR2 to the construction 200 to heat the construction.

[0089] The system 100 may further comprise one or more particle filters 160 configured to remove dust and particulate matter from air inside the indoor compartment 111 of the transportable housing 110. Preferably, each of the one or more particle filters 160 is arranged at each of the one or more inlet air ducts 120, as schematically presented in Figures 5a and 5b, or at each of the one or more outlet air ducts 130. More preferably, each of the one or more particle filters 160 is arranged at an inlet opening of the one or more inlet air ducts 120, as schematically presented in Figure 5a. The one or more particle filters 160 are configured to remove at least part of dust and particulate matter from the air to be treated. The dust removal may contribute to an extended lifetime of the one or more air source heat pumps by reducing the need to circulate dust and particulate matter through the indoor unit 101 and the outdoor unit 102 of each of the one or more air source heat pumps. Furthermore, with the filters, at least partially cleaned air with a reduced dust content may be returned from the system 100 back to the construction 200, improving the air quality inside the construction 200.

[0090] A method for treating air to heat, to cool, or to dry air within a construction 200 using the transportable air treating system 100 is schematically presented in Figure 1 . The method comprises a) conveying incoming air AIR1 from the construction 200 to the system 100 through the one or more inlet air ducts 120; b) treating the incoming air AIR1 using the one or more air source heat pumps by transferring heat from the incoming air AIR1 to the indoor unit 101 and further to the outdoor unit 102, or from the outdoor unit 102 to the indoor unit 101 and further to the incoming air AIR1 , by means of a heat carrier 103, thus producing treated air AIR2 at the predetermined outlet air temperature TOUT; and c) returning the treated air AIR2 from each indoor unit 101 of the one or more air source heat pumps to the construction 200 through the one or more outlet air ducts 130.

[0091] The method may further comprise filtering air inside the indoor compartment 111 of the transportable housing 110 by means of one or more particle filters. Preferably, each of the one or more particle filters 160 is arranged at each of the one or more inlet air ducts 120 or at each of the one or more outlet air ducts 130. More preferably, each of the one or more particle filters 160 is arranged at an inlet opening of each of the one or more inlet air ducts 120. Filtering the air thus be carried out at the one or more inlet air ducts 120 or within the one or more outlet air ducts 130. Filtering the air has the advantage of improving quality of the treated air AIR2 to be returned to the construction 200. Placement of the one or more particle filters at the inlet opening of each of the one or more inlet air ducts 120 has an advantage of preventing dust and particulate matter from entering the one or more air source heat pumps or at least reducing the amount of dust and particulate matter entering the one or more air source heat pumps, thus increasing lifetime of the system.

[0092] The method may further comprise controlling the operation of the one or more air source heat pumps by a controller 140 according to at least one of the following: the predetermined outlet air temperature TOUT, inlet air temperature TIN, target air temperature TT inside the construction 200, present air temperature TPRES inside the construction 200, temperature difference TDIFF between the target air temperature TT and the present air temperature TPRES, outside temperature TEXT, and required heating power capacity PH. The controller 140 typically independently controls the operation of the indoor unit 101 and the operation of the outdoor unit 102 of the one or more air source heat pumps. The method may further comprise heating air inside the indoor compartment 111 by means of a heater 150. As schematically presented in Figures 4a-4b, the heater 150 may be used to pre-heat the incoming air AIR1 before entering the indoor unit 101 of the one or more air source heat pump. Alternatively or in addition, a heater 150 may be located within the one or more outlet air ducts 130, whereby the heater 150 may be used to heat air exiting the indoor unit 101 of the one or more air source heat pumps, thus providing the treated air AIR2, as schematically presented in Figure 4c.

[0093] Operation of the heater 150 may be controlled by the controller 140 according to at least one of the following: the predetermined outlet air temperature TOUT, inlet air temperature TIN, target air temperature TT inside the construction 200, present air temperature TPRES inside the construction 200, temperature difference TDIFF between the target air temperature TT and the present air temperature TPRES, outside temperature TEXT, and required heating power capacity PH. In other words, operation of the heater 150 and operation of the one or more air source heat pumps are jointly controlled by the controller 140.

[0094] If the required heating power capacity PH exceeds the maximum heating capacity of the one or more air source heat pumps, the heater 150 will be used in addition to the one or more air source heat pumps to heat the incoming air AIR1 to produce the treated air AIR2, i.e., heated air. The heated, treated air AIR2 is then returned to the construction 200 to heat the construction.

[0095] Operation of the one or more air source heat pumps and the operation of the heater 150 may conveniently be jointly controlled by the controller 140. In a typical controlling cycle, at least one of the following conditions is fulfilled:

[0096] - if the temperature difference TDIFF is at least 5°C after a first checkpoint time ti after switching on the one or more air source heat pumps, the heater 150 is switched on;

[0097] - if the temperature difference TDIFF is at least 5°C after a second checkpoint time t2 after switching on the one or more air source heat pumps, operation power of the heater 150 is increased;

[0098] - when the outside temperature TEXT approaches a critical outside temperature Tc, operation power of the one or more air source heat pumps is gradually decreased; and / or - when the outside temperature TEXT falls below the critical outside temperature Tc, the outdoor unit 102 of each of the one or more air source heat pumps is switched off, whereby the heater 150 is the primary source of heat in the treated air AIR2.

[0099] The target air temperature TT may be selected as desired by the user. The target air temperature TT inside the construction 200 is typically selected in the range of 10°C to 25°C to provide comfortable circumstances for the user inside the construction 200.

[0100] The first checkpoint time ti is typically in the range of 1 to 30 min, such as 5 to 10 min. The second checkpoint time t2 is typically in the range of 10 to 50 min, such as 15 to 30 min. The checkpoint times are selected such that the target air temperature TT may be reached within a tolerable amount of time. If the target air temperature TT inside the construction 200 has not been reached within the first checkpoint time ti after switching on the one or more air source heat pumps, indicated by the temperature difference TDIFF being at least 5°C, additional heating by the heater 150 is required and the heater 150 is switched on. If the target air temperature TT inside the construction 200 has still not been reached within the second checkpoint time t2 after switching on the one or more air source heat pumps, indicated by the temperature difference TDIFF being at least 5°C, power of the heater 150 is increased.

[0101] The critical outside temperature Tc may be selected in the range of -18°C to -30°C, preferably in the range of -20°C to -25°C. Below these temperatures, the heat transfer capacity as well as the lifetime of the one or more air source heat pumps drastically decrease.

[0102] When the outside temperature TEXT approaches the critical outside temperature Tc, operation power of the one or more air source heat pumps is gradually decreased. Thus, at high or modest temperatures, e.g., at 0°C and above, the one or more air source heat pumps may be operated at a power close to their maximum heat transfer capacity, e.g., at 70 to 90% of the maximum heat transfer capacity. When the outside temperature decreases, the maximum heat transfer capacity of the one or more air source heat pumps also decreases. Moreover, operating the one or more heat pumps at a power close to their maximum capacity may quickly deteriorate the performance of the one or more air source heat pumps. Thus, the heater is used as an additional source of heat, and the operation power of the one or more air source heat pumps may be gradually decreased. At temperatures approaching the critical outside temperature Tc, e.g., within 5°C to 10°C above the critical outside temperature Tc, the one or more air source heat pumps may be operated, e.g., at a power of 5 to 20% of their maximum heat transfer capacity.

[0103] When the outside temperature TEXT falls below the critical outside temperature Tc, the outdoor unit 102 of each of the one or more air source heat pumps is switched off, whereby the heater 150 is the primary source of heat in the treated air AIR2. With the outdoor unit 102 switched off, no heat transfer between the indoor unit 101 and the outdoor unit 102 takes place. Fans of the indoor unit 101 of the one or more air source heat pumps may still be used for circulating the incoming air AIR1 through the indoor unit 101 and the heater 150 to produce the treated air AIR2.

[0104] Example 1 .

[0105] An air treating system was constructed in a modified freight container serving as the transportable housing. Three air source heat pumps were installed in the container. Side walls of the container were partially removed to allow the outside units of the air source heat pumps to be in contact with the environment, and to transfer heat to and from the environment. A wall was constructed to separate the indoor compartment from the outdoor compartment. The indoor compartment was thermally insulated using Pll foam.

[0106] The indoor units of the air source heat pumps were installed in the indoor compartment, and the outdoor units were installed in the outdoor compartment, respectively.

[0107] The system was equipped with inlet air ducts and outlet air ducts. The inlet air ducts were installed to convey the incoming air directly to the inlets of the indoor units. A heater was installed in the outlet air ducts. Nominal capacity of each of the air source heat pumps was 26 kW, thus providing a total nominal capacity of 80 kW for the system. Nominal capacity of the heater was 80 kW.

[0108] The system has a total air circulation capacity of approx. 14 400 m3 / h.

[0109] Example 2.

[0110] The system of Example 1 was used.

[0111] Maximum cooling and heating capacities of the system at different outside temperatures TEXT are listed in Table 1 .

[0112] The air source heat pumps cannot typically be used at their maximum capacity at extended periods of time to avoid malfunctioning. At -20°C, for example, the air source heat pumps can typically be operated with a total power of ca. 30 kW. If the total required heating power exceeds said 30 kW, the heater will additionally be used. For example, if the total required heating power PH is 100 kW, the heater will provide ca. 70 kW of heating power.

[0113] At 0°C, the air source heat pumps can typically be operated with a total power of ca. 60 kW. Thus, with a similar 100 kW heating power requirement, the power requirement from the heater will be reduced to 40 kW.

Claims

Claims:1 . A transportable air treating system (100) for treating air to heat, to cool, or to dry air within a construction (200), the system comprising- one or more air source heat pumps, wherein each air source heat pump of the one or more air source heat pumps comprises an indoor (101 ) unit and an outdoor unit (102);- a transportable housing (110) comprising an indoor compartment (111 ) and an outdoor compartment (112), wherein the outdoor compartment (112) is in contact with an outside environment surrounding the system (100) and wherein the indoor compartment (111 ) comprises a thermal insulation layer (113) to thermally insulate the indoor compartment (111 ) from the outside environment surrounding the system (100), and wherein the transportable housing (110) is configured to receive the one or more air source heat pumps such that the indoor unit (101 ) of each air source heat pump of the one or more air source heat pumps is arranged in the indoor compartment (111 ) of the transportable housing (110) and the outdoor unit (102) of each of the one or more air source heat pumps is arranged in the outdoor compartment (112) of the transportable housing (110);- one or more inlet air ducts (120) configured to convey incoming air (AIR1 ) from the construction (200) to the system (100), wherein each air source heat pump of the one or more air source heat pumps is configured to circulate the incoming air (AIR1 ) through the indoor unit (101 ) to produce treated air (AIR2) at a predetermined outlet air temperature (TOUT) and to transfer heat from the incoming air (AIR1 ) to the indoor unit (101 ) and further to the outdoor unit (102), or from the outdoor unit (102) to the indoor unit (101 ) and further to the incoming air (AIR1 ), by means of a heat carrier (103); and- one or more outlet air ducts (130) configured to return the treated air (AIR2) from each indoor unit (101 ) of the one or more air source heat pumps to the construction (200).

2. The system (100) according to claim 1 , further comprising a controller (140) configured to control operation of the one or more air source heat pumps according to at least one of the following: the predetermined outlet airtemperature (TOUT), inlet air temperature (TIN), target air temperature (TT) inside the construction (200), present air temperature (TPRES) inside the construction (200), temperature difference (TDIFF) between the target air temperature (TT) and the present air temperature (TPRES), outside temperature (TEXT) , and required heating power capacity (PH).

3. The system (100) according to claim 1 or 2, further comprising a heater (150) arranged within the indoor compartment (111 ) of the transportable housing (110), wherein the heater (150) is configured to heat air inside the indoor compartment (111 ) of the transportable housing (110), preferably wherein the heater (150) is an electric heater or a combustion heater.

4. The system (100) according to claim 3, wherein the combustion heater is fuelled by a fuel selected from renewable fuel, fossil fuel, and a combination thereof, preferably wherein the renewable fuel is selected from a group comprising vegetable oils, biodiesel, biomethanol, bioethanol, biogas, synthetic fuels, such as electrofuels, and biomass, such as wood, e.g., pellets, and / or wherein the fossil fuel is selected from natural gas, petroleum, and coal.

5. The system according to any of claims 3 to 4, wherein the controller (140) is further configured to control operation of the heater (150) according to at least one of the following: the predetermined outlet air temperature (TOUT), inlet air temperature (TIN), target air temperature (TT) inside the construction (200), present air temperature (TPRES) inside the construction (200), temperature difference (TDIFF) between the target air temperature (TT) and the present air temperature (TPRES), outside temperature (TEXT), and required heating power capacity (PH).

6. The system (100) according to any of the preceding claims, comprising 2 to 5 air source heat pumps, wherein each air source heat pump of the 2 to 5 air source heat pumps comprises an indoor unit (101 ) and an outdoor unit (102), such as 2 heat pumps, 3 heat pumps, 4 heat pumps, or 5 heat pumps.

7. The system (100) according to any of the preceding claims, wherein the one or more air source heat pumps are air-to-air heat pumps.

8. The system (100) according to any of the preceding claims, further comprising one or more particle filters (160) configured to remove dust and particulate matter from air inside the indoor compartment (111 ) of the transportable housing (110), preferably wherein each of the one or more particle filters (160) is arranged at each of the one or more inlet air ducts (120) or at each of the one or more outlet air ducts (130), more preferably wherein each of the one or more particle filters (160) is arranged at an inlet opening of each of the one or more inlet air ducts (120).

9. A method for treating air to heat, to cool, or to dry air within a construction (200) using the transportable air treating system (100) of any of claims 1 to 9, the method comprising a) conveying incoming air (AIR1 ) from the construction (200) to the system (100) through the one or more inlet air ducts (120); b) treating the incoming air (AIR1 ) using the one or more air source heat pumps by transferring heat from the incoming air (AIR1 ) to the indoor unit (101 ) and further to the outdoor unit (102), or from the outdoor unit (102) to the indoor unit (101 ) and further to the incoming air (AIR1 ), by means of a heat carrier (103), thus producing treated air (AIR2) at the predetermined outlet air temperature (TOUT); and c) returning the treated air (AIR2) from each indoor unit (101 ) of the one or more air source heat pumps to the construction (200) through the one or more outlet air ducts (130).

10. The method according to claim 9, further comprising filtering air inside the indoor compartment (111 ) of the transportable housing (110) by means of one or more particle filters (160), preferably wherein each of the one or more particle filters (160) is arranged at each of the one or more inlet air ducts (120) or at each of the one or more outlet air ducts (130), more preferably wherein each of the one or more particle filters (160) is arranged at an inlet opening of each of the one or more inlet air ducts (120).

11. The method according to claim 9 or 10, further comprising controlling the operation of the one or more air source heat pumps by a controller (140) according to at least one of the following: the predetermined outlet air temperature (TOUT), inlet air temperature (TIN), target air temperature (TT) inside the construction (200), present air temperature (TPRES) inside theconstruction (200), temperature difference (TDIFF) between the target air temperature (TT) and the present air temperature (TPRES), outside temperature (TEXT) , and required heating power capacity (PH).

12. The method according to any of claims 9 to 11 , further comprising heating air inside the indoor compartment (111 ) by means of a heater (150).

13. The method according to 11 or 12, further comprising controlling the operation of the heater (150) by the controller (140) according to at least one of the following: the predetermined outlet air temperature (TOUT), inlet air temperature (TIN), target air temperature (TT) inside the construction (200), present air temperature (TPRES) inside the construction (200), temperature difference (TDIFF) between the target air temperature (TT) and the present air temperature (TPRES), outside temperature (TEXT) , and required heating power capacity (PH).

14. The method according to claim 13, wherein operation of the one or more air source heat pumps and the operation of the heater (150) are controlled by the controller (140), such that at least one of the following conditions is fulfilled:- if the temperature difference (TDIFF) is at least 5°C after a first checkpoint time (ti) after switching on the one or more air source heat pumps, the heater (150) is switched on;- if the temperature difference TDIFF is at least 5°C after a second checkpoint time t2 after switching on the one or more air source heat pumps, operation power of the heater (150) is increased;- when the outside temperature (TEXT) approaches a critical outside temperature (Tc), operation power of the one or more air source heat pumps is gradually decreased; and / or- when the outside temperature (TEXT) falls below the critical outside temperature (Tc), the outdoor unit (102) of each of the one or more air source heat pumps is switched off, whereby the heater (150) is the primary source of heat in the treated air (AIR2).

15. The method according to claim 13, wherein the first checkpoint time (ti) is in the range of 1 to 30 min, such as 5 to 10 min; wherein the second checkpoint time (t2) is in the range of 10 to 50 min, such as 15 to 30 min; and / or whereinthe critical outside temperature Tc is selected in the range of -18°C to -30°C, preferably in the range of -20°C to -25°C.

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