Water-cooled subsea power arrangement

Abstract

A water-cooled subsea power arrangement (1) comprising a liquid-filled enclosure (3) that encloses a heat-generating electric power unit (7). It further comprises a plurality of cooling channels (15)

Description

WATER-COOLED SUBSEA POWER ARRANGEMENTTechnical Field

[0001] The present invention relates to a water-cooled subsea power arrangement, configured to be installed in a body of water, such as on the seabed.Background Art

[0002] Many electric power units generate heat that must be dissipated away from the power unit. Typical units include transformers, variable speed drives, rectifiers, or switchgears. When such power units are installed subsea, it is known to exploit the relatively low water temperature for cooling the power units.

[0003] For instance, some solutions connect the oil inside an oil-filled enclosure to an external heat exchanger, so that the oil is cooled by the water. The cooled oil flows in a loop, out of the enclosure as warm oil, into the heat exchanger, and back into the enclosure as cooled oil.

[0004] This type of equipment is relatively complex and expensive, as it typically will include a pump for providing the flow of oil, and possibly valves for controlling the flow.

[0005] Publication EP3404198 B1 presents a solution that avoids these disadvantages, as it uses natural convection to provide flow of the cooling fluid. The cooling fluid is flown out of the enclosure containing the heat-generating electric unit, into an external pressure compensator. In the pressure compensator, the fluid is cooled, and then it flows back into the enclosure. In this solution, the pressure compensator shall thus provide the pressure-compensating function as well as the cooling function (working as a heat exchanger).

[0006] If the heat generated inside the enclosure that contains the heat-generating power unit is sufficiently low, it may be sufficient to provide the enclosure with cooling ribs or other protrusions that will guide the generated heat into the ambient seawater.

[0007] However, if this is not sufficient, it is common to guide the fluid in the enclosure, typically oil, out of the enclosure for external cooling.

[0008] An object of the present invention may be to provide a solution that avoids the need for flowing the fluid out of the enclosure.

[0009] Another object may be to provide a water-cooled subsea power arrangement with increased cooling capacity, while avoiding active cooling (i.e. using pump to obtain flow).

[0010] Further objects may be met with the invention, as will become apparent by the following disclosure.Summary of invention

[0011] According to the present invention, there is arranged a water-cooled subsea power arrangement comprising a liquid-filled enclosure that encloses a heatgenerating electric power unit, such as a subsea transformer, VSD (variable speed drive), or another electric heat-generating unit. The power arrangement further comprises a plurality of cooling channels. The cooling channels extend through the enclosure and have an inlet and an outlet. The inlet is arranged vertically below the outlet. Moreover, the inlet and the outlet of the respective cooling channels are both in liquid communication with the ambient sea water.

[0012] The liquid in the liquid-filled enclosure can be oil, or another dielectric liquid.

[0013] In this manner, ambient, cold seawater can flow through the cooling channels. As the skilled person will appreciate, the flow will be generated due to the reduced density in the heated water inside the cooling channels.

[0014] The electric power unit can typically be a high-power unit, meaning that it is configured for or rated for power higher than 5 MVA, or 10 MVA, or even higher than 50 MVA.

[0015] In some embodiments, the enclosure can comprise a base plate and a top plate, wherein the inlets are arranged in the base plate.

[0016] In other embodiments, however, some or all the inlets may be inlets arranged in the enclosure walls.

[0017] Moreover, the enclosure can have vertical enclosure walls that extend between the base plate and the top plate. The base plate and the top plate canextend horizontally beyond the enclosure walls. The enclosure can further comprise a plurality of ribs extending between the base plate and the top plate, wherein the ribs are in contact with and extending out from the enclosure walls. In such embodiments, the base plate and / or the top plate can comprise rib channel apertures at respective ends of rib channels that extend between and alongside adjacent ribs.

[0018] In some embodiments, the outlets of the cooling channels are arranged in the top plate. In other embodiments, the outlets are arranged in the enclosure walls. A combination is also feasible, with some outlets arranged in the top plate and other outlets arranged in the enclosure walls.

[0019] In some embodiments, the cooling channels can be straight. However, in other or combined embodiments, the cooling channels can comprise a vertical and straight lower portion, a curved portion connected to the top of the lower portion, and an end portion that ends at the outlet. As the skilled reader will appreciate, these portions can be pipes.

[0020] In some such embodiments, the curved portion may have a bending angle in the range of 30 to 50 degrees, for instance 45 degrees. In other embodiments, the curved portion may have a bending angle of substantially 90 degrees.

[0021] The cooling channels can advantageously be made of pipes containing copper-nickel (CuNi) (or Cupronickel), i.e. an alloy containing copper and nickel.

[0022] The electric power unit can for instance be a transformer, a switch-gear, a variable speed drive, a rectifier, a frequency converter, or a collector.

[0023] In some embodiments, the water-cooled subsea power arrangement further comprises a funnel which is arranged around the enclosure. The funnel comprises vertical lower walls that form a sea water duct between the vertical lower walls and the enclosure walls. This will provide a flow of sea water passing the enclosure in an upward direction.

[0024] In some embodiments, the funnel can comprise sound-absorbing means to adsorb sound produced by the heat-generating electric power unit. Such soundabsorbing means can for instance be inclusions in the material of the funnel walls, and / or a grooved surface.

[0025] There is also disclosed a row of at least two subsea power arrangements arranged at a subsea location, wherein the respective subsea power arrangements comprise a liquid-filled enclosure that encloses a heat-generating electric power unit, and further comprises a side wall. The side walls of adjacent enclosures are arranged opposite each other and with a mutual distance.

[0026] The liquid in the liquid-filled enclosure can be oil or another dielectric liquid.

[0027] In some embodiments, the row can comprise three, four, or five subsea power arrangements.

[0028] Advantageously, the respective enclosures comprise two parallel side walls. Moreover, the row of subsea power arrangements can be straight.

[0029] The side walls can face in a direction parallel with the direction of the straight row.

[0030] One or more of the heat-generating electric power units of the respective subsea power arrangements can comprise a subsea transformer.

[0031] In some embodiments, the respective subsea power arrangements are supported by one or more support arrangements, such that the lower rim of the volume defined between the oppositely arranged side walls is in fluid communication with the water present below the enclosures.

[0032] Advantageously, the two oppositely arranged side walls arranged with the said mutual distance between them can be parallel.

[0033] In some embodiments of the row, a ratio between the area of the respective side walls and the distance between them is in the range of from 7 m to 300 m.

[0034] The volume between opposite side walls of adjacent subsea power arrangements can be confined by baffles. This will enhance the flow rate of sea water between the subsea power arrangements.

[0035] In another embodiment, the volume between opposite side walls of adjacent subse power arrangements can comprise a row of vertically arranged pipes with open ends.

[0036] Furthermore, in some embodiments, the row can comprise subsea power arrangements as discussed above.

[0037] In some embodiments, there can be arranged two rows in parallel and with a mutual distance between each other. The mutual distance between the rows can be, but needs not be, the same as the mutual distance between two subsea power arrangements in one row.Detailed description of the invention

[0038] While various features of the invention have been discussed in general terms above, some more detailed, and non-limiting examples of embodiment will be presented in the following with reference to the drawings, in whichFig. 1 is a schematic side view of a water-cooled subsea power arrangement according to the invention;Fig. 2 is a schematic perspective view of the embodiment shown in Fig. 1 , however without the power unit indicated;Fig. 3 is a schematic side view of an embodiment resembling the embodiment shown in Fig. 1 , however provided also with a funnel;Fig. 4 is a perspective view of another embodiment according to the invention;Fig. 5 is a perspective schematic illustration depicting an alternative design of the cooling channels;Fig. 6 depicts an embodiment with the cooling channel design shown in Fig. 5;Fig. 7 is a schematic cross section side view of a part of an enclosure of a water- cooled subsea power arrangement according to the invention;Fig. 8 is a perspective view of a row of subsea power arrangements arranged at a subsea location;Fig. 9 is a schematic side-view of the row shown in Fig. 8;Fig. 10 is a top view illustrating an embodiment with two parallel rows of subsea power arrangements; andFig. 11 is a top view illustrating an embodiment similar to the one shown in Fig. 10.

[0039] Fig. 1 is a schematic side view of a water-cooled subsea power arrangement 1 , hereinafter termed a power arrangement 1 . The power arrangement 1 has an enclosure 3 that is filled with oil. When the power arrangement 1 is arranged in the sea, such as on the seabed, the enclosure 3 is surrounded by sea water. A support arrangement 4 supports the weight of the enclosure 3 and provides access of sea water under it.

[0040] The enclosure 3 has an internal chamber 5. Inside the enclosure 3, i.e. in the internal chamber 5, the power arrangement 1 has a heat-generating electric power unit 7, hereinafter termed a power unit 7. In the shown embodiment, the power unit 7 is an electric transformer.

[0041] The enclosure 3 has a base plate 9 and a top plate 11 . Arranged between the base plate 9 and the top plate 11 the enclosure 3 has enclosure walls 13.

[0042] Since the power unit 7 generates heat, the oil contained in the enclosure 3 will become warm and must be cooled. Cooling channels 15 extend through the enclosure 3, between respective inlets 17 and outlets 19. The inlets 17 and outlets 19 communicate with the ambient sea water. Moreover, since the inlets 17 are located at a lower elevation than the outlets 19, sea water will flow through the cooling channels 15 as it is heated by the walls of the cooling channels 15. This will in cool the oil in the internal chamber 5, which in turn will cool the power unit 7.

[0043] By arranging the cooling channels 15 through the internal chamber 5 and thus in direct contact with the oil, one obtains an efficient cooling of the oil. Moreover, by using the temperature difference to obtain the said flow, one avoids additional equipment such as a pump and a pump motor.

[0044] Fig. 2 is a perspective view of the embodiment shown in Fig. 1 , however shown without the power unit 7.

[0045] Fig. 3 depicts another embodiment, wherein a funnel 21 is landed to surround the enclosure 3. The funnel 21 comprises a base portion with vertical lower walls 23 that are arranged in parallel and with a horizontal distance from the enclosure walls 13. Above the vertical lower walls 23 the funnel 21 has a funnel- shaped portion 25 that ends in an upper funnel duct 25. The upper funnel duct 25has a narrowed cross section, compared to the cross section defined by the vertical lower walls 23.

[0046] A sea water duct 24 is formed between the vertical lower walls 23 and the enclosure walls 13.

[0047] Since the enclosure walls 13 of the enclosure 3 will be warmer than the ambient sea water, the sea water will be heated by the enclosure 3 and flow upwardly through the funnel 21 as indicated with the arrows.

[0048] The funnel 21 contributes to the flow of seawater through the cooling channels 15, hence not only to the flow through the sea water duct 24 between the funnel 21 and the enclosure walls 13.

[0049] Some types of heat-generating power units 7, for instance transformers, produce sounds. The funnel 21 can in addition be used as a sound-absorber, to reduce the environmental effects by the produced sound. The funnel 21 can then be provided with sound-absorbing means (not shown).

[0050] A suitable material of the funnel 21 for providing the sound-absorbing characteristic, is a composite material, for instance GRP (glass reinforced plastic) and / or other polymer-containing materials. Sound-absorbing means may for instance comprise inclusions (e.g. gas inclusions) in the material (a porous material) and / or a grooved surface for sound absorption.

[0051] Reference is now made to Fig. 4, which depicts a schematic perspective view of a power arrangement 1 according to the invention. In this embodiment, the base plate 9 and the top plate 11 comprises base protrusions 9a and top protrusions 11 a that extend horizontally beyond the enclosure walls 13. Between the base protrusions 9a and the top protrusions 11a, there are arranged a plurality of ribs 27. The ribs 27 are attached to the enclosure walls 13, such that thermal heat can be transferred from the enclosure walls 13 to the ribs 27, and thus to the ambient sea water. Between pairs of adjacent ribs 27, there are thus formed a vertically extending rib channels 29. Sea water that is present in the rib channels 29 will be heated and thus flow upwardly in the respective rib channels 29.

[0052] Furthermore, in the embodiment shown in Fig. 4, there is advantageously provided rib channel apertures 31 in the base protrusion 9a and in the top protrusion11 a. The rib channel apertures 31 are arranged at the respective lower and upper ends of the rib channels 29. The rib channel apertures 31 enhances the flow through the rib channels 29, as a substantial part of the flow through the rib channels 29 will enter through the lower channel apertures 31 and leave through the upper channel apertures 31 . The rib channel apertures 31 will also contribute to cooling of the base plate 9 and the top plate 11 of the enclosure, in addition to the enclosure walls 13.

[0053] In some embodiments it may be beneficial to avoid having the outlets 19 of the cooling channels 15 arranged in the top plate 11. This can for instance be in embodiments where pressure compensation equipment (for instance bellows) is placed on the top of the enclosure 3. In such embodiments, the cooling channels 15 may have the outlets 19 arranged in the enclosure walls 13, as shown in Fig. 5.

[0054] In this embodiment, the cooling channels 15 have a lower portion 15a that is vertical and straight, a curved portion 15b connected on top of the lower portion 15a, and an end portion 15c that ends at the outlet 19. The curved portion 15b ensures that the pressure drop over the angle change is not too high, since this would reduce the heat-induced flow of sea water through the cooling channels 15.

[0055] The enclosure 3 can advantageously be pressure balanced, so that there will be substantially zero pressure drop over the walls of the pipes that constitute the cooling channels 15.

[0056] Fig. 6 depicts this embodiment with a perspective view. As shown, the outlets 19 are located in the rib channels 29. Fig. 7 depicts a cross section side view of the same embodiment, with various flows of sea water indicated with the arrows.

[0057] In embodiments comprising the funnel 21 , the vertical walls 23 of the funnel 21 could advantageously be arranged with a horizontal distance from the ribs 27 and the base and top protrusions 9a, 11 a.

[0058] Fig. 8 and Fig. 9 depicts a solution where a row 100 of subsea power arrangements 101 are arranged subsea. The respective subsea power arrangements 101 have an enclosure 103 that is filled with oil. The enclosures 103 are surrounded by sea water. One or more support arrangements 104 support the weight of the enclosures 103 and provides access of sea water below them.

[0059] The respective enclosures 103 have an internal chamber 105. Inside the enclosure 103, i.e. in the internal chamber 105, the power arrangements 101 have a heat-generating electric power unit 107, hereinafter termed a power unit 107. In the shown embodiment, the power unit 107 is an electric transformer.

[0060] The enclosures 103 have side walls 1 13. The subsea power arrangements 101 are arranged in the row 100 such that side walls 1 13 of different power arrangements 101 are arranged opposite of each other and with a mutual distance 140.

[0061] Advantageously, as shown in the present embodiment, the opposite side walls 1 13 can be substantially parallel.

[0062] This configuration of the row 100 will heat the water present between the oppositely arranged side walls 1 13. The heated water will rise and provide a flow of water flowing upwardly in the space between the oppositely arranged side walls 1 13. This is illustrated with the arrows inserted in Fig. 9. The water flow will contribute to cooling of the side walls 1 13 and thus the oil inside the enclosure 103.

[0063] To obtain this effect, the mutual distance between two oppositely arranged side walls cannot be too large. Furthermore, if sufficient water is not present between the side walls 1 13 is not present, water may flow but the cooling effect may be neglectable.

[0064] Hence, a suitable ratio R between the area of the side walls 1 13 and the distance 140 between them should be chosen. For instance, the respective side walls 1 13 may have an area of 3 m x 4 m = 12 m2. The mutual distance between them could be 0,5 m. The ratio R would then be 12 m2 / 0,5 m = 24 m. A suitable range of ratio R can be from 7 m to 300 m.

[0065] A particular benefit of supporting the subsea power arrangements 101 in an elevated state with the support arrangements 104 is that water can access the area between the oppositely arranged side walls 1 13 from below. In such embodiments, the lower rim of the volume defined between the oppositely arranged side walls 113 is in fluid communication with the water present below the enclosures 103.

[0066] Fig. 10 is a top view of two parallel rows 100 of subsea power arrangements101 . The mutual distance 140 between the side walls 113 are indicated for side walls113 that extend in different orthogonal directions. Furthermore, baffles 115 are arranged to confine the volume between the side walls 113. This provides an increased flow of sea water and hence enhances the cooling function. It shall be clear to the skilled reader that the baffles 115 are optional. Advantageously, the baffles 115 can be vertically oriented.

[0067] Fig. 11 depicts an embodiment similar to the embodiment shown in Fig. 10. Instead of the baffles 115, a row of pipes 117 are arranged between the side walls 113 of adjacent power arrangements 1 . The pipes 117 can be vertically arranged and are open in both ends. They can advantageously be made of metal to ensure a good heat transfer through their walls. The pipes 117 provides an efficient flow of sea water between the enclosure walls 113, and thus enhances the cooling function.

Claims

Claims1 . A water-cooled subsea power arrangement (1 ) comprising a liquid-filled enclosure (3) that encloses a heat-generating electric power unit (7), characterized in that it further comprises a plurality of cooling channels (15), wherein the cooling channels (15) extend through the enclosure (3) and have an inlet (17) and an outlet (19), the inlet being arranged vertically below the outlet, and wherein the inlet (17) and the outlet (19) of the respective cooling channels (15) are both in liquid communication with the ambient sea water.

2. A water cooled subsea power arrangement (1) according to claim 1 , characterized in that the enclosure (3) comprises a base plate (9) and a top plate (11 ), and that the inlets (17) are arranged in the base plate (9).

3. A water cooled subsea power arrangement (1) according to claim 2, characterized in that- the enclosure (3) comprises vertical enclosure walls (13) extending between the base plate (9) and the top plate (11 );- the base plate and the top plate extend horizontally beyond the enclosure walls (13);- the enclosure (3) further comprises a plurality of ribs (27) extending between the base plate and the top plate, the ribs (27) being in contact with and extending outwardly from the enclosure walls (13);- the base plate (9) and the top plate (11 ) comprise rib channel apertures (31 ) at respective ends of rib channels (29) extending between adjacent ribs (27).

4. A water cooled subsea power arrangement (1) according to claim 2, or according to claim 2 and claim 3, characterized in that the outlets (19) are arranged in the top plate (11 ).

5. A water cooled subsea power arrangement (1) according to claim 2, or according to claim 2 and claim 3, characterized in that the outlets (19) are arranged in the enclosure walls (13).

6. A water cooled subsea power arrangement (1) according to any one of the preceding claims, characterized in that the cooling channels (15) comprise a vertical and straight lower portion (15a), a curved portion (15b) connected to the top of the lower portion, and an end portion (15c) that ends at the outlet (19).

7. A water cooled subsea power arrangement (1) according to one of the preceding claims, characterized in that the electric power unit (7) is a transformer, a switch-gear, a variable speed drive, a rectifier, a frequency converter, or a collector.

8. A water cooled subsea power arrangement (1) according to one of the preceding claims, characterized in that it further comprises a funnel (21 ) arranged around the enclosure (3), wherein the funnel comprises vertical lower walls (23) that form a sea water duct between said vertical lower walls and the enclosure walls (13).

9. A water cooled subsea power arrangement (1 ) according to claim 8, characterized in that the funnel (21 ) comprises sound-absorbing means to adsorb sound produced by the heat-generating electric power unit (7).

10. A row (100) of at least two subsea power arrangements (101 ) arranged at a subsea location, wherein the respective subsea power arrangements (101 ) comprise a liquid-filled enclosure (103) that encloses a heat-generating electric power unit (7), and a side wall (113), wherein side walls (113) of adjacent enclosures (103) are arranged opposite each other and with a mutual distance (140).11 . A row (100) according to claim 10, wherein the respective subsea power arrangements (101 ) are supported by one or more support arrangements (104), such that the lower rim of the volume defined between the oppositely arranged side walls (113) is in fluid communication with the water present below the enclosures (103).

12. A row (100) according to claim 10 or claim 1 1 , wherein a ratio (R) betweenthe area of the respective side walls (113) and the distance (140) between them is in the range of from 7 m to 300 m.

13. A row (100) according to one of the claims 10 to 12, wherein the volume between opposite side walls (113) of adjacent subsea power arrangements (101 ) is confined by baffles (115).

14. A row (100) according to one of the claims 10 to 12, wherein the volume between opposite side walls (113) of adjacent subsea power arrangements (101 ) comprises a row of vertically arranged pipes (117) with open ends.

15. A row (100) according one of the claims 10 to 14, wherein it is arranged opposite and with a mutual distance (140) to another row (100) according to one of the claims 10 to 12.

16. A row (100) according to one of the claims 10 to 15, comprising subsea power arrangements (1 , 101 ) according to one of the claims 1 to 9.

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