WO2013007257A1

WO2013007257A1 - A method and an apparatus for controlling the humidity inside an enclosure

Info

Publication number: WO2013007257A1
Application number: PCT/DK2012/000082
Authority: WO
Inventors: Joergen Jessen Moeller; Kirsten Stentoft Hansen
Original assignee: Danfoss Solar Inverters AS
Current assignee: Danfoss Power Electronics AS
Priority date: 2011-07-14
Filing date: 2012-07-10
Publication date: 2013-01-17
Anticipated expiration: 2014-01-14
Also published as: DK177309B1

Abstract

An apparatus (100) for controlling the humidity inside an enclosure which defines a opening (102) for exchange of air between an inner space of the enclosure and surroundings thereof, wherein the apparatus (100) comprises: a desiccant member (106) which defines a flow passage (114) inside which is provided : a desiccant (118), and a means (120) for regenerating the desiccant; wherein the desiccant member (106) is arranged such that exchange of air through the opening (102) for exchange of air is caused to flow through the flow passage (114) of the desiccant member ( 106). A method for controlling the apparatus (100).

Description

A METHOD AND AN APPARATUS FOR CONTROLLING THE HUMIDITY INSIDE AN ENCLOSURE FIELD OF THE INVENTION

The present invention relates to an apparatus for controlling the humidity inside an enclosure. Moreover, the present invention relates to a method for controlling the humidity inside an enclosure.

BRIEF DESCRIPTION OF THE INVENTION

Nowadays, electric, electromagnetic and electronic components are used for many different purposes in almost every technological field. For protecting those electric, electromagnetic and electronic components (and also for protecting operating personnel, the environment or the like from an electric shock), such components are usually arranged in essentially closed cavities, for example in cabinets. Those cabinets generally offer protection against unintended contact with the components therein or even protection from wilful destruction by criminal subjects. Such cabinets are used, for example, in connection with solar inverters, which is a piece of equipment which takes DC power from one or more solar panels, and converts it into AC power suitable for connecting to the electrical grid. In a typical field system a number of solar panels will feed into a single box mounted outside. This box would contain a solar inverter and the output AC to an electrical grid.

When a box containing electronic equipment is placed outside it is influenced by both the temperature of the environment and the humidity of the air. One problem that occurs is that when temperatures fall during the night, the temperature inside the box also will fall and thereby water contained in the humid air inside the box condenses within the box on the electrical components thus causing short-circuits. Furthermore, boxes suitable for outdoor use are often constructed in a way in which passage of air in and out of the box is constrained in order to protect the contents from, for example, dust. Such a construction also hinders the dispersal of accumulated humidity within the box that might occur if there was free passage of air. Whilst this is a problem for any box containing electronic equipment, it is particularly noticeable for boxes containing solar inverters, since the solar inverter is not used during the night - because there is no sun - and therefore generates no heat during that period. Other types of equipment may well continue to generate heat and therefore not suffer so much with this problem. If condensation occurs regularly then it may also lead to longer term problems such as corrosion and delamination of PCBs which may reduce the lifetime and/or reliability of the electronic equipment. It is an object of one or more embodiments of the present invention to provide an inexpensive and reliable solution to the problem of condensation in electric cabinets.

Moreover, it is the object of one or more embodiments of the present invention to provide dehumidifying device, in particular a dehumidifying device for an essentially closed cavity device that is improved over dehumidifying devices according to the state of the art.

DESCRIPTION OF THE INVENTION

In a FIRST aspect, the present invention relates to an apparatus for controlling the humidity inside an enclosure which defines an opening for exchange of air between an inner space of the enclosure and surroundings thereof, wherein the apparatus comprises - a desiccant member which defines a flow passage inside which is provided :

- a desiccant, and

- a means for regenerating the desiccant; wherein the desiccant member is arranged such that exchange of air through the opening for exchange of air is caused to flow through the flow passage of the desiccant member. By providing a desiccant inside the desiccant member and a means for regenerating the desiccant, the humidity inside the enclosure may be controlled, as air flowing into the enclosure through the opening will pass through the desiccant member, whereby its humidity will be lowered due to the desiccant. Typically this will happen when the temperature inside the enclosure drops e.g. at night when the sun no longer heats the structure defining the enclosure. The decreasing temperature will cause the air inside the enclosure to contract, thus causing air to flow into the enclosure.

When on the other hand the temperature inside the enclosure increases, the air inside the enclosure expands and thus results in a flow of air out of the enclosure. In the latter case, operation of the means for regenerating will cause the humidity contained in the desiccant to be transferred to the air flowing out of the enclosure. This causes the desiccant to be dried, whereby it will be ready to be used once the temperature inside the enclosure drops again and air with high humidity flows into the enclosure. The enclosure may be defined by a structure such as a cabinet for accommodating an electrical circuit for controlling a solar panel. The structure may comprise sidewalls and an upper wall and a bottom wall. In one embodiment, the enclosure defines one single opening in connection with which, an apparatus for controlling the humidity is arranged. In other embodiments, the enclosure comprises a plurality of openings one or more of which (such as all of which) comprises an apparatus for controlling the humidity.

It will be appreciated that by providing an opening, with an apparatus according to the present invention, the humidity may be controlled sufficiently to ensure that the relative humidity of the air is so low that it does not damage any electrical components contained in the enclosure.

The desiccant member may define a longitudinal direction which extends in a direction transverse to an outer surface of the structure defining the enclosure. In one embodiment, the width of the desiccant member is at least two times the width of the desiccant member, such as three times the width, such as four times the width, such as five times the width. The cross-sectional shape of the desiccant member in a direction transverse to its longitudinal direction may be round such as circular or oval. Alternatively, the cross-sectional shape may be polygonal and thus defining three or more edges, such as three edges, such as four edges, such as five edges.

A seal may be provided between the desiccant member and structure which defines both the enclosure and the opening. The seal ensures that the flow of air is channelled through the flow passage and thus past the desiccant.

The desiccant may be provided in the form of spheres, or balls or pieces which is

accommodated inside the flow passage. It will be appreciated that by providing desiccant members which are spherical, small spaces are defined between neighbouring spherical members. In these small spaces, the desiccant defines a large number of desiccant surfaces whereby the total surface of the desiccant will be extremely large. When air flows through the flow passage, it will be forced to pass through these small spaces and thus contact the extremely large surface of the desiccant whereby vapour may be transferred to or from the air depending on whether or not the means for regenerating is operated. It will be appreciated that depending on the geometry of other shapes of the pieces of desiccant, the above may also be the case.

Examples of desiccants are silica gel (a highly porous, granular form of silica), calcium chloride and calcium sulphate. In one embodiment, the desiccant occupies at least 30 percent of total volume of the flow passage, such as at least 40 percent, such as at least 50 percent, such as at least 60 percent, such as at least 70 percent, such as at least 80 percent, such as at least 90 percent, such as at least 100 percent. The volume of the flow passage may be at least one tenth of a litre, such as at least one half of a litre, such as at least one litre, such as at least 5 litres, such as at least 10 litres, such as at least 15 litres, such as at least 20 litres, such at least 30 litres. Alternatively or additionally, the volume of the flow passage may be at least 1 percent of the total volume of the enclosure, such as at least 5 percent, such as at least 10 percent, such as at least 20 percent, such as at least 30 percent.

In one embodiment, the apparatus is an apparatus for reducing the humidity inside equipment for processing power generated from one or more intermittent power sources. In the context of the present invention, the term 'intermittent power source' shall be understood as any source of energy which is not continuously available due to one or more factors outside direct control of the intermittent power source and/or human beings. Intermittent power is often supplied by renewable energy sources such as by means of solar panels and devices for generating tidal energy. It will be appreciated that such energy sources may in some cases be very predictable. As an example tidal energy can be predicted with high precision and the same applies with solar energy - especially when combined with weather forecast information.

In one embodiment, the desiccant member defines one or more outer openings through which air may flow between the desiccant member and the surrounding air, and one or more inner openings through which air may flow between the desiccant member and the inner space. The inner openings may be defined in a wall of the desiccant member, such as in a sidewall of the desiccant member and/or in a bottom surface/wall of the desiccant member. Moreover, a part of the desiccant member may extend out of the opening for exchange of air, or the opening(s) for exchange of air may be defined by the desiccant member. It will be appreciated that the larger the total area of each of the inner and the outer openings is, the easier it will be for air to flow into and out of the enclosure. Moreover, it will be appreciated that it is desirable that the size of the inner and the outer openings is chosen such that the desiccant cannot pass therethrough. Accordingly in one embodiment, the inner openings and/or the outer openings are dimensioned such that the desiccant is retained inside the flow passage. Thus when the desiccant forms

spheres/balls/pieces, the largest dimension of any of the inner and the outer openings may be smaller than the smallest dimension of any of the spheres/balls/pieces. In the context of the present invention, the term 'regenerating' shall be understood as the process of expelling at least a part of the humidity from the desiccant. The means for regenerating the desiccant may take any form. In one embodiment, this/these means is/are powered by means of a gas source such as LPG. In another embodiment, the means for regenerating is powered by electrical energy. The means for regenerating the desiccant may comprise one or more heating elements which is/are arranged to co-extends in the longitudinal direction of the flow passage e.g. inside the flow passage. The number of heating elements may be one, two, three, four, five etc. The heating elements may be arranged inside the flow passage such that an outer surface of the heating elements is in direct contact with some of the desiccant. In another embodiment, the means for spacing the desiccant apart from the heating elements may be provided. This may be a shield provided around the heating element.

In order to control the means for regenerating the desiccant, the apparatus may comprise a controller which is adapted to operate the means for regenerating the desiccant in response to a predetermined initiation parameter. As previously mentioned, the intermittent power source may be predictable to some degree. This may be used to control the means for regenerating the desiccant. As an example, solar power may be produced from sunrise to sunset. As the temperature inside the enclosure increases when the sun is shining, the controller may be adapted to initiate the operation when the temperature inside the enclosure rise at a certain rate or with a predetermined number of degrees, such as when the temperature rise with more than half a degrees per minute, such as more than one degree per minute, such as more than one and a half degree per minute. Alternatively it may be adapted to start operation when the temperature has increased 5 degrees relative to the lowest temperature recorded within the last 12 hours. In one embodiment, the predetermined initiation parameter is one more of:

- a predetermined initiation point in time (such as at a predetermined point in time in the morning or a predetermined point in time after a predetermined event such at a predetermined period of time after sunrise),

- a predetermined inner initiation temperature inside the enclosure (such as when the temperature inside the enclosure is a predetermined number of degrees above the lowest temperature recorded within a predetermined time period such as the last 12 hours or when the temperature is a predetermined number of degrees the dew point such as 4 degrees above dew point), - a predetermined outer initiation temperature outside the enclosure (such as a predetermined number of degrees above the dew point of the air present outside the enclosure, such as the temperature outside the enclosure is at a predetermined level),

- a predetermined initiation humidity inside the enclosure, (such as when the relative humidity is above a predetermined level such as above 50 %RH, such as above 60 %RH, such as above 70 %RH, such as above 80 %RH, such above 90 %RH, such as 100 %RH, or when the humidity increases at a predetermined rate)

- a predetermined initiation temperature of the desiccant member (By a predetermined initiation temperature of the desiccant member may be understood a temperature determined in the vicinity of the desiccant such as by means of a temperature gauge provided close to or in direct contact with the desiccant member) ,

- a predetermined initiation level electrical energy supplied by a predetermined apparatus (it will be appreciated that with an intermittent energy source, the level of electrical energy supplied will vary over time. As an example, the energy level of a solar panel is very low or even zero during the night. When the energy level rises to a predetermined level, the heating elements may be operated. This may e.g. be an energy level which is sufficiently large to ensure that thermal energy is generated by the heating elements or an energy level which is sufficiently large to ensure that a predetermined temperature of the heating elements is ensured). In some embodiments, the controller is adapted not to terminate the operation of the means for regenerating the desiccant at any point in time, i.e. the means for regenerating the desiccant is operated continuously. In other embodiments, the controller is adapted to terminate the operation of the means for regenerating the desiccant in response a predetermined termination parameter. In one embodiment, the predetermined termination parameter is one or more of:

- a predetermined termination point in time (such as a predetermined point in time in the evening. One example is, two hours before sun set),

- a predetermined inner termination temperature inside the enclosure (as an example the predetermined inner termination temperature inside the enclosure may be a

predetermined number of degrees above the dew point, such as one degree above the dew point, such as two degrees above the dew point, such as three degrees above the dew point, such as four degrees above the dew point, such as five degrees above the dew point - the dew point being the temperature at which the relative humidity is so high that dew is formed e.g. on the inner surfaces of the enclosure),

- a predetermined outer termination temperature outside the enclosure (again the

predetermined outer termination temperature outside the enclosure may be a predetermined number of degrees above the dew point, such as one degree above the dew point, such as two degrees above the dew point, such as three degrees above the dew point, such as four degrees above the dew point, such as five degrees above the dew point),

- a predetermined termination humidity inside the enclosure (such as when the relative humidity is below a predetermined level such as above 50 %RH, such as above 60 %RH, such as above 70 %RH, such as above 80 %RH, such above 90 %RH, such as 100 %RH, or when the humidity increases at a predetermined rate),

- a predetermined termination temperature of the desiccant member (By a predetermined termination temperature of the desiccant member may be understood a temperature determined in the vicinity of the desiccant such as by means of a temperature gauge provided close to or in direct contact with the desiccant member),

- a predetermined termination level electrical energy supplied by a predetermined

apparatus (again as the level of electrical energy supplied by an intermittent energy source varies over time, the predetermined termination level of electrical energy may be when the energy level is too low to operate the heating elements or an energy level which is too low to ensure that a predetermined temperature of the heating elements is achieved).

In a SECOND aspect, the present invention relates to a method of controlling the humidity inside an enclosure which defines a opening for exchange of air between an inner space of the enclosure and surroundings thereof, the apparatus comprising a desiccant member which defines a flow passage inside which is provided : a desiccant, and a means for regenerating the desiccant; the method comprising the step of:

- operating the means for regenerating the desiccant in response to a predetermined initiation parameter. In one embodiment, the method comprises the step of: - terminating the operation of the means for regenerating the desiccant in response to a predetermined termination parameter.

The termination parameter may be one of the predetermined termination parameters described under the first aspect of the invention. In one embodiment, the predetermined initiation parameter is one more of: a predetermined initiation point in time, a predetermined inner initiation temperature inside the enclosure, a predetermined outer initiation temperature outside the enclosure, a predetermined initiation humidity inside the enclosure, a predetermined initiation temperature of the desiccant member, a predetermined initiation level electrical energy supplied by a predetermined apparatus.

Again reference is made to the description of similar predetermined initiation parameters under the first aspect of the invention.

In one embodiment, the predetermined termination parameter is one or more of: a predetermined termination point in time, a predetermined inner termination temperature inside the enclosure, a predetermined outer termination temperature outside the enclosure, a predetermined termination humidity inside the enclosure, a predetermined termination temperature of the desiccant member, a predetermined termination level electrical energy supplied by a predetermined apparatus.

Again reference is made to the description of similar predetermined termination parameters under the first aspect of the invention.

In one embodiment, the desiccant member is arranged such that exchange of air through the opening for exchange of air is caused to flow through the flow passage of the desiccant.

The invention according to the second aspect may comprise any combination of features and/or elements of the invention according to the first aspect. BREIF DESCRIPTION OF THE FIGURES

The invention will now be described with reference to the figures in which :

Fig. 1 discloses a first embodiment of the apparatus for controlling the humidity, Fig. 2 discloses a second embodiment of the apparatus for controlling the humidity, and

Fig. 3 discloses diagram for a one embodiment for a control circuit for the apparatus for controlling the humidity.

DETAILED DESCRIPTION OF THE FIGURES Figs. 1 and 2 disclose a first and a second embodiment of an apparatus 100 for controlling the humidity inside an enclosure which defines an opening 102 in a sidewall 104 of the enclosure. In the embodiment to of Fig. 1, the remainder of the enclosure is not illustrated. However, the skilled person will readily realize that further sidewalls must be provided in order to define the enclosure. In one embodiment, the opening 102 is the only opening in the enclosure. However in other embodiments, further openings may be provided. These further openings may accommodate an apparatus 100 for controlling the humidity inside the enclosure. In any event, the only passage of air between the enclosure and the surroundings may be through the one or more apparatuses 100.

By designing the apparatus such that air can only move between the enclosure and the surrounding through the apparatus(es) 100, the humidity inside the enclosure may be controlled. This is explained in further detail below.

The apparatus 100 comprises an elongated desiccant member 106 which defines a plurality of inner openings 108 and a plurality of outer openings 110. During use, air flows from the enclosure to the surroundings through the inner openings 108, further through the longitudinally extending flow passage 114 of defined by the walls 116 of the desiccant member 106 and out through the outer openings 110. It will be appreciated that during use, the flow of air may be reversed as is explained in further detail below. However in the context of the invention, the term downstream shall designate the flow from the enclosure and towards the surroundings through the inner openings 108, the flow passage 114 and finally the outer openings 110.

As the outer openings 110 are subjected to the weather outside the enclosure, a cover 112 is provided which prevents rain from entering the apparatus 100 through the outer openings 110. In some embodiments, the apparatus 100 is provided on an upper surface of the structure which defines the enclosure. In other embodiments, the apparatus 100 is provided in a position in which the outer openings 110 are sheltered from the weather. This could be on a bottom surface of the structure which defines the enclosure. A desiccant 118 is provided inside the flow passage 114. In the figures, the desiccant is provided in the form of spheres or balls or pieces the size of which is large enough to ensure that the balls/spheres cannot pass through the inner openings 108 or outer openings 110. In one embodiment, the smallest dimension of each ball/sphere/piece is at least 10 percent larger than the largest dimension of the inner openings 108, such as 25 percent larger, such as 50 percent larger, such as 100 percent larger.

For simplicity reasons, the desiccant 118 is only illustrated in the lower right corner of the flow passage 114. But the skilled person will readily realise that a larger part of the flow passage 114 will be filled with the desiccant. In one embodiment, at least 25 percent of the volume of the flow passage 114 accommodates the desiccant, such as 50 percent, such as 75 percent, such as 90 percent, such as 100 percent.

In order to regenerate the desiccant 118, one or more means of regenerating the desiccant in the form of heating elements 120 are provided. In the embodiment of the figures, the heating element 120 is provided in the form of an elongated electrically controllable heating element 120. The elongated heating element 120 may be adapted to generate thermal energy when it is supplied with electrical energy. In other embodiments, a plurality of heating elements 120 is provided, such as two, three, four, five or ten. It is desirable that the heating elements 120 are arranged in the vicinity of the desiccant 118, such that thermal energy from the heating elements 120 may be transferred to the desiccant by thermal conduction and/or thermal radiation. It will be appreciated that due the flow of air in the flow passage 114, thermal energy will also be transferred to the desiccant 118 by thermal convection. In one embodiment, the heating elements 120 are arranged in direct contact with the desiccant 118.

The desiccant member 106 has a total width 122 and a total length (not indicated on the drawings). In some embodiment, the length of the desiccant member 106 is at least two times the width, such as at least three times the width, such as at least four times the width.

The inner length 124 of the desiccant member 106 corresponds the length of that part of the desiccant member 106 which extends inside the enclosure. As the desiccant member 106 is elongated in the figures, the inner length 124 of the desiccant member 106 is larger than the width 124 of the desiccant member 106. In one embodiment, a width 126 of the heating elements 120 is at least 50 percent of the length of the inner length 124, such as at least 75 percent, such as at least 80 percent, such as 90 percent.

In the embodiment of Fig. 1, the inner openings 108 are defined in the sidewall 104.

Contrary hereto the inner openings 108 of Fig. 2 are defined in the bottom of the elongated desiccant member 106. It will be appreciated that in yet another embodiment, inner openings 108 are provided in both the bottom and the sidewalls 104 of the elongated desiccant member 106.

In the embodiments of Figs. 1 and 2, the inner openings 108 are defined in the sidewall 104 or the bottom of the elongated desiccant member 106. However, in other embodiments the elongated desiccant member merely defines a structure which is adapted to hold a filter or screen in place. The screen/filter serves the purpose of retaining the desiccant in place inside the elongated desiccant member 106. In yet another embodiment, the elongated desiccant member 106 comprises a combination of passages (inner openings 108) defined in the sidewall 104 and/or the bottom and a filter/screen. It will be appreciated that a screen defines a plurality of inner openings 108.

Fig. 3 discloses one embodiment of an electrical diagram of an electrical circuit 200 for controlling the heating element 120. In the embodiment, of fig. 3 magnetically operated relays are used, however, the skilled person will readily realize that other kinds of electrically circuits 200 may be used to achieve the same result. In the diagram according to claim 3, the heating element 120 is operated after power up of the system. The heating element 120 is not shut off until it attains a certain temperature. When this happens, the heating element 120 is turned off, and is not switched on again until power has been off for a predetermined period of time. The entire electrical circuit is connected to an electrical power source which comprises a positive lead 218 and a negative lead 220. The electrical power source is an intermittent power source e.g. solar panels. When the electrical power source is energised, a portion of the voltage resulting is applied to the positive input 221 of the comparator 223. This portion is controlled by the voltage divider comprising the resistors 226 and 227. The voltage at the other input 222 of the comparator 223 is controlled by the resistor 225 and the Zener diode 224. The voltage of other input 222 of the comparator 223 is limited to a maximum related to the voltage of the Zener diode 224. As a result of this, the voltage at the output of the comparator 223 will remain low until the voltage between the positive lead 218 and the negative lead 220 has risen to a level related to the voltage of the Zener diode 224. At this point the relay A (reference number 206) will close as due to the field induced in A-coil 212 by current flowing from the output of the comparator into the capacitor 216. It will be appreciated that this current will slowly reduce as the capacitor 216 becomes charged and at some point in time it will be insufficient to keep the relay A closed, and the relay will open. Thus the circuitry comprising the resistors 225, 226, 227, Zener diode 224, capacitor 216 and the comparator 223 function to temporarily close the relay A when the input voltage (for example from a solar panel) has reached a preset level. The power circuit 200 is supplied with electrical energy from a source of intermittent electrical power e.g. a solar panel. When the intermittent power source starts to generate electrical power e.g. when the sun rises, a current flows through the A-coil 212 of the relay A (reference 206) which causes the A-contact 214 to close, as described above. The effect is that an electrical current flows through the heating element 120 whereby thermal energy is generated by the heating element 120. Moreover, it will be appreciated that an electrical current will also flow through the B-coil 208 of relay B (reference 204) whereby the B-contact 210 is closed. Thus, by the time the relay A opens again (when the capacitor 216 has charged sufficiently) the relay B 204 will have closed and a current path through the switch 210 will have been made, and the current through the heater 120 will continue to flow.

The resistor 228 discharges the capacitor 216 when the supply of electrical power is removed. The resistor 228 is selected such that the current flowing through it is not sufficient to close relay A (reference number 206). A temperature control switch 202 is provided in series with the heating element 120. The temperature control switch 202 is adapted to open at a predetermined opening temperature and is adapted to close at a predetermined closing temperature. Accordingly, the electrical current flowing through the heating element 120 will continue to flow through the B-contact 210 until the temperature control switch 202 reaches the predetermined opening

temperature. When the temperature control switch 202 opens, the current through heating element 120 drops and that the B-contact 210 opens, since the current through the relay coil 208 has now dropped. At this point no current flows through heating element 120 until the relay closes, which only happens when the power has been off for a period sufficiently long for the capacitor to discharge. Thus with this circuit, when power is applied, the heating element 120 will heat until the temperature control switch 202 has reached the predetermined opening temperature (determined by the characteristics of the temperature control switch 202). At this point in time, the temperature control switch 202 will switch off the heating element 120 which will not be turned on until power has been turned off for a predetermined period of time, (this period of time being determined by the values of the capacitor 216 and resistor 228).

As will be appreciated, it is also possible to achieve the above sequence by using a controller which comprises timers and drivers for switches. It will also be appreciated that the switches can comprise other technologies that the mechanical relays shown here, solid state switches such as SCRs, FETs or IGBTs may with advantage be used.

Claims

1. An apparatus (100) for controlling the humidity inside an enclosure which defines an opening (102) for exchange of air between an inner space of the enclosure and surroundings thereof, wherein the apparatus (100) comprises - a desiccant member (106) which defines a flow passage (114) inside which is

provided :

- a desiccant ( 118), and

- a means (120) for regenerating the desiccant; wherein the desiccant member (106) is arranged such that exchange of air through the opening (102) for exchange of air is caused to flow through the flow passage (114) of the desiccant member (106).

2. An apparatus (100) according to claim 1, wherein the apparatus (100) is an apparatus for reducing the humidity inside an equipment for processing power generated from one or more intermittent power sources.

3. An apparatus (100) according to any of the preceding claims, wherein the desiccant member (106) defines one or more outer openings (110) through which air may flow between the desiccant member (106) and the surrounding air, and one or more inner openings ( 108) through which air may flow between the desiccant member (106) and the inner space.

4. An apparatus (100) according to claim 3, wherein the inner openings (108) and/or the outer openings (110) are dimensioned such that the desiccant (118) cannot pass therethrough.

5. An apparatus (100) according to claim 3 or 4, wherein the means (120) for regenerating the desiccant (118) comprises one or more heating elements which is/are arranged to co- extend(s) in the longitudinal direction of the flow passage (114).

6. An apparatus ( 100) according to any of the preceding claims, further comprising a controller which is adapted to operate the means ( 120) for regenerating the desiccant in response to a predetermined initiation parameter.

7. An apparatus (100) according to claim 6, wherein the predetermined initiation parameter is one more of: a predetermined initiation point in time, a predetermined inner initiation temperature inside the enclosure, a predetermined outer initiation temperature outside the enclosure, a predetermined initiation humidity inside the enclosure, a predetermined initiation temperature of the desiccant member (106), a predetermined initiation level electrical energy supplied by a predetermined apparatus.

8. An apparatus (100) according to any of claims 6 or 7, wherein the controller is adapted to terminate the operation of the means ( 120) for regenerating the desiccant in response a predetermined termination parameter.

9. An apparatus (100) according to claim 8, wherein the predetermined termination parameter is one or more of: a predetermined termination point in time, a predetermined inner termination temperature inside the enclosure, a predetermined outer termination temperature outside the enclosure, a predetermined termination humidity inside the enclosure, a predetermined termination temperature of the desiccant member ( 106), a predetermined termination level electrical energy supplied by a predetermined apparatus.

10. A method of controlling the humidity inside an enclosure which defines a opening (102) for exchange of air between an inner space of the enclosure and surroundings thereof, and utilising an apparatus (100) comprising a desiccant member ( 106) which defines a flow passage ( 114) inside which is provided : a desiccant ( 118), and a means (120) for regenerating the desiccant; the method comprising the step of:

- operating the means (120) for regenerating the desiccant in response to a

predetermined initiation parameter.

11. A method according to claim 10, wherein the method comprises the step of:

- terminating the operation of the means ( 120) for regenerating the desiccant in

response to a predetermined termination parameter.

12. A method according to claim 10 or 11, wherein the predetermined initiation parameter is one more of: a predetermined initiation point in time, a predetermined inner initiation temperature inside the enclosure, a predetermined outer initiation temperature outside the enclosure, a predetermined initiation humidity inside the enclosure, a predetermined initiation temperature of the desiccant member (106), a predetermined initiation level electrical energy supplied by a predetermined apparatus.

13. A method according to any of claims 10-12, wherein the predetermined termination parameter is one or more of: a predetermined termination point in time, a predetermined inner termination temperature inside the enclosure, a predetermined outer termination temperature outside the enclosure, a predetermined termination humidity inside the enclosure, a predetermined termination temperature of the desiccant member (106), a predetermined termination level electrical energy supplied by a predetermined apparatus.

14. A method according to any of claims 10-13, wherein the desiccant member (106) is arranged such that exchange of air through the opening (102) for exchange of air is caused to flow through the flow passage (114) of the desiccant member (106).