NL2024159B1

NL2024159B1 - A method of electrically connecting off-shore devices for generating electricity to the shore, and a floater

Info

Publication number: NL2024159B1
Application number: NL2024159A
Authority: NL
Inventors: Aart Los Sven; Gerardus Franciscus Maria Holtacker Johannes; Ignatius Maria Van Roosmalen Cornelis; Gerrit Buitendijk Lennart; Hubert Boender Etienne
Original assignee: Nevesbu B V; Iv Offshore & Energy B V
Priority date: 2019-11-05
Filing date: 2019-11-05
Publication date: 2021-08-08

Abstract

A method of electrically connecting off—shore devices for generating electricity to the shore. To reduce the cost of electrically 5 connecting off—shore devices for generating electricity to the shore, an off—shore floater is used, said off—shore floater comprising a — a first Gas—Insulated Switchgear (GIS), — a transformer for generating High Voltage from a relatively low input voltage 10 — a second Gas—Insulated Switchgear; wherein in no particular order — a multitude of off—shore devices for generating electricity is electrically connected to a moored off—shore floater, and — the off—shore floater is electrically connected to the shore.

Description

A method of electrically connecting off-shore devices for generating electricity to the shore, and a floater The present invention relates to a method of electrically connecting off-shore devices for generating electricity to the shore.

Placing devices for generating electricity, such as wave energy devices or wind turbines, off shore is gaining popularity because of several reasons. For example, there is more wind above sea than above land, there are less complaints about any perceived negatives (noise pollution; visual pollution) and the space hasn't been claimed. The advantage of a remote location brings with it that it is also located further from the grid, and connecting devices for generating electricity to an on-shore grid is thus costly. Also, the further the devices for generating electricity are from land, the more energy will be lost to heat because of electrical resistance.

The object of the present invention is to reduce the cost of electrically connecting off-shore devices for generating electricity to the shore.

To this end, a method according to the preamble is characterized in that a moored off-shore floater is used, said off-shore floater comprising a ~ a first Gas-Insulated Switchgear (GIS), — a transformer for generating High Voltage from a relatively low input voltage ~ a second Gas-Insulated Switchgear; wherein in no particular order - a multitude of off-shore devices for generating electricity is electrically connected to the moored off-shore floater, and — the off-shore floater is electrically connected to the shore, wherein the floater comprises at least one stabiliser, and wherein the stabiliser comprises a plate having a density of at least 2 kg/liter suspended from the floater, said plate extending in a direction parallel to the earth surface.

Thus a reduction in cost can be achieved. This is in particular the case in water having a depth of at least 50 m, such as 100 m or more.

In the present application, a relatively low input voltage is a high voltage of at least 20 kV. It is converted to the relatively higher High Voltage by at least 50%.

The floater is for example a buoy or a semi-sub (semisubmersible rig).

The stabiliser helps to reduce the acceleration to which the GIS devices are subjected. The stabiliser stabilises the floater with respect to waves or swell. The stabiliser may be an active stabiliser, involving the movement of a mass such as water or a weight using an actuator towards a side that is lifted by the waves or swell to dampen the wave-induced motions of the floater.

Being suspended from the floater using at least one longitudinally extending element such as a chain, a cable or a rod, the element is always under tension, reducing shocks due to the floater being lifted or lowered by swell or waves.

The plate will typically be suspended at least 50 meters below the bottom of the floater, preferably at least 100 meters and more preferably at least 200 meters. The lower the plate is suspended, the less the plate itself is subjected to swell and waves, and the better it acts as a stabiliser.

The plate will typically have a surface area of at least 100 nm, preferably at least 250 m® and more preferably at least 500 me.

The plate is held preferably by at least three longitudinally extending elements attached at spaced apart locations on the plate, helping to ensure that the plate is kept horizontal. The plate has a density that is preferably at least 100% and more preferably at least 400% higher than the density of the surrounding water. The weight of the plate helps to lower the floater deeper into the body of water, rendering floater more stable.

The floater may be anchored to the floor of the body of water by an anchor attached to the floor, for example using a chain or cable.

The floor is for a salt water body called a seabed, which term will be used hereinafter without restricting the scope of the invention to salt water bodies.

According to a favourable embodiment, the stabiliser comprises a balcony at an at least partially submerged section of the floater, said balcony extending continuously or semi-continuously over the circumference of the floater.

Such a passive stabiliser is relatively cheap, and reliable. The stabiliser will have a horizontal component extending over a distance of at least 1 meter, preferably at least 3 meters, and typically 7 meters or more.

According to a favourable embodiment, the floater comprises a multitude of levels.

This allows placement of the various components such as GIS devices etc. at a different levels.

According to a favourable embodiment, the floater comprises a multitude of levels, said levels separated by decks, wherein at least one level is provided with upright walls, and for at least one level two adjacent decks are formed as a torsion box using said upright walls.

This renders the floater more dimensionally stable, reducing forces exerted on the GIS devices, in particular if the GIS devices are placed on a deck that is part of the torsion box.

According to a favourable embodiment, the upright walls of a torsion box are corrugated upright walls, with ribs of the corrugation extending in an upright direction.

The use of such upright walls help to resist buckling of said upright walls and improves the strength of the torsion box.

According to a favourable embodiment, the off-shore floater has at least four decks, wherein the first and second Gas-Insulated Switchgears are located on a floor of a level wherein said floor is at or below the waterline or on a floor of an immediately adjacent level.

This reduces the forces to which the GIS is subject, allowing the off-shore floater to be used not just in fresh water lakes but also in inland seas (such as the Caspian sea) or open inland seas (Baltic sea) and even in open seas and the ocean, i.e. in water deeper than 50 m which is typically where the cost of installing a transformer station off shore start to rise exponentially.

According to a favourable embodiment, the transformer is located at a deck above the deck supporting at least one of the Gas-Insulated Switchgears.

This frees up space for the Gas-Insulated Switchgears to be located relatively close to the center of the off-shore floater.

According to a favourable embodiment, the off-shore floater comprises a DC Converter, and High Voltage alternating current from the transformer is converted into High Voltage direct current using said DC Converter.

This allows transport of the current over longer distances for a given loss of energy; or with less loss of energy for a given distance. By way of example, a relatively low voltage of 33 kV or 66 kV AC will be increased to a High voltage of 220 kV or 320 kV DC.

According to a favourable embodiment, the devices for generating electricity are wind turbines, preferably floating wind turbines.

The use of floating wind turbines allows for a windfarm irrespective of the water depth and/or soil condition (silt, sand, rock etc.) of the seabed.

Finally, the present invention relates to a floater containing electrical equipment, wherein the floater is a floater suitable as an off-shore floater.

Off-shore floaters containing electrical equipment are known in the art, in particular in the field of oil- and gas exploration. In relatively deep waters (of 50 m and more), towers or pillar structures to mount equipment become exceedingly expensive. For this reason, it is known to use moored off-shore floaters.

To this end, a floater according to the preamble is characterized in that said floater is suitable for use in the above method, and comprises — a first Gas-Insulated Switchgear (GIS), — a transformer for generating High Voltage from a relatively now input voltage ~ a second Gas-Insulated Switchgear, wherein the {floater comprises at least one stabiliser, and wherein the stabiliser comprises a plate having a density of at least 2 kg/liter suspended from the floater, said plate extending in a direction parallel to the earth surface.

In the present application, the term off-shore floater refers to its suitability to be moored off-shore and is not an indication of it actually being off-shore unless specifically indicated.

The plate will typically be suspended at least 50 meters below 5 the bottom of the floater, preferably at least 100 meters and more preferably at least 200 meters. The lower the plate is suspended, the less the plate itself is subjected to swell and waves, and the better it acts as a stabiliser.

The plate will typically have a surface area of at least 100 mn’, preferably at least 250 m' and more preferably at least 500 mm.

According to a favourable embodiment, the off-shore floater has at least four decks, wherein the first and second Gas-Insulated Switchgears are located on a floor of a level wherein said floor is below the waterline or on a floor of an imediately adjacent level.

This reduces the forces to which the GIS is subject, allowing the off-shore floater to be used not just in fresh water lakes but also in inland seas (such as the Caspian sea) or open inland seas (Baltic sea) and even in open seas and the ocean.

According to a favourable embodiment, the off-shore floater comprises a DC converter for converting High Voltage alternating current from the transformer to direct current.

This allows transport of the current over a longer distances for a given loss of energy; or with less loss of energy for a given distance.

The present invention will now be illustrated with reference to the drawing where Fig. 1 shows schematically a floater connecting a wind turbine to the shore; Fig. 2 shows schematically a side view of the floater of Fig. 1; Fig. 3a to Fig. 3g show top views of the various decks of the floater of Fig. 2; and Fig. 4 shows schematically an alternative embodiment of the floater of Fig. 1.

Fig. 1 shows schematically a floater 100 (buoy 100) connecting a floating wind turbine 190 on a body of water 192 (sea) with a water surface 192 to the shore 185. The floating wind turbine 190 is connected via a cable 191 carrying relatively low voltage (e.g. 66 kV) to a floater 100. In the floater 100, the voltage is increased and converted to DC, and the resulting DC current is transported to the shore 195 via a cable 196 to a station 197 from where it is distributed to the mains or any other recipient.

The floating wind turbines 190 and the floater 100 are anchored to the sea bed 199 using mooring lines 110.

Fig. 2 shows schematically a side view of the floater 100 of Fig.

1. The floater 100 comprises a plurality of decks, with contiguous lines indicating the levels of the decks as shown in top view in Fig. 3a to Fig. 3g.

The floater 100 of Fig. 2 shows ballast chambers 201, a crew cabin 202 and a landing platform 203 for a helicopter. Over the circumference of the floater 100 there is a balcony 204 which helps to stabilise the floater in case of swell and waves.

Fig. 3a to Fig. 3g show top views of the various decks of the floater of Fig. 2, from top to bottom.

Above the chambers 201 for ballast (ballast tanks filled with sea water) there is the first deck 310 (Fig. 3a) comprising a room 311 for a ballast water pump, a cable cellar 312, room 313 for a sewage treatment plant for treating sewage from the crew cabin 202, a room

314 for a sea water heat exchanger to maintain the temperature of various equipment in the floater, a room 315 comprising a pump for filtering sea water, and a room 316 for an oil pump.

Fig. Sb shows a second deck 320 located above the first deck 310, comprising rooms 321 for spare parts, service rooms 322 and rooms 323 for (diesel) generators.

Fig. 3c shows a third deck 330 located above the second deck 320, comprising rooms 331 for regulating transformer & auxiliary transformer systems, rooms 332 for auxiliary switchboard systems comprising an auxiliary switchboard 10 KV AC system), and rooms 333 for batteries.

Fig. 3d shows a fourth deck 340 (fourth level) located above the third deck 330, comprising a room 341 for a compensation reactor (35 MVA), rooms 342 for mooring equipment and a room 343 for a first Gas-Insulated Switchgear (GIS) of 155 kV, a room 344 for a second Gas-Insulated Switchgear (GIS) of 400 kV. This is a protection measure between the floater 100 and the shore station 197.

Fig. 3e shows a fifth deck 350 located above the fourth deck 340, comprising halls 351 for valves (i.e. static DC converters for converting AC into DC), reactor halls 352 comprising reactors for smoothing the direct current reducing ripple voltage, a rooms 353 for converter transformers and a room 354 for Valve Service Cooling.

Fig. Sf shows a sixth deck 360 located above the fifth deck 350, with the crew cabin 202 (living quarters) and a room 361 for an Air Handling Unit HVAC transformer.

Fig. 3g shows a seventh deck 370 located above the sixth deck 360, comprising the platform 203 for a helicopter.

Fig. 4 shows schematically an alternative embodiment of a floater 100, which is moored using mooring lines 110. Apart from the balcony 204, the stabiliser comprises a further stabiliser, here in the form of a horizontal plate 410. The plate 410 is connected to the bottom of the floater 100 using rods 420'. This further stabiliser 410 acts strongly against vertical motions of the floater 100 that would be caused by waves, thus reducing the accelerations to which GIS are 3% subjected.

Claims

Conclusions l. A method of electrically connecting offshore devices (110) for generating electricity to the shore (195), characterized in that an anchored offshore float (100) is used, the offshore float (100) comprising: - a first gas-insulated control station ("Gas-Insulated Switchgear", GIS), - a transformer for generating high voltage ("High Voltage") from a relatively low input voltage - a second gas-insulated control station; wherein in no particular order: - a plurality of offshore electricity generating devices (110) are electrically connected to the anchored offshore float (100), and - the offshore float (100) is electrically connected to the shore (195), wherein the float (100) comprises at least one stabilizer, and wherein the stabilizer comprises a plate (410) having a density of at least 2 kg/litre suspended from the float (100), the plate (410) being in extends in a direction parallel to the Earth's surface.

The method of claim 1, wherein the stabilizer comprises a balcony (204) on an at least partially submerged portion of the float (100), the balcony (204) extending continuously or semi-interruptedly about the circumference of the float ( 100) extends.

The method of any of claims 1 or 2, wherein the float (100) comprises a plurality of levels.

The method of claim 3, wherein the float (100) comprises a plurality of levels, the levels being separated by decks, at least one level having upright walls, and two adjacent decks being formed for at least one level. as a torsion box using the upright walls.

Method according to claim 4, wherein the upright walls of a torsion box are ribbed upright walls, wherein the ribs of the rib structure extend in vertical direction.

A method according to any one of claims 3 to 5, wherein the offshore float (100) has at least four decks, the first and second gas-insulated control stations being located on a floor of a level where the floor is at or below the waterline or on a floor of an immediately adjacent level IO.

A method according to any one of claims 3 to 6, wherein the transformer is located on a deck above the deck carrying at least one of the gas-insulated control stations.

A method according to any one of the preceding claims, wherein the offshore float (100) converts high voltage (high voltage) alternating current from the transformer into high voltage direct current using the DC converter is converted.

A method according to any one of the preceding claims, wherein the devices for generating electricity are wind turbines, preferably floating wind turbines (190).

10, Float (100) comprising electrical equipment, the float (100) being a float (100) 1s suitable as an offshore float (100), characterized in that the float (100) is suitable for use in above method, and includes: - a first gas-insulated control station ("Gas-Insulated Switchgear", GIS), - a transformer for generating high voltage ("High Voltage") from a relatively low input voltage - a second gas-insulated control station,

wherein the float (100) comprises at least one stabilizer, and wherein the stabilizer comprises a plate (410) having a density of at least 2 kg/litre suspended from the float (100), the plate (410) being in extends in a direction parallel to the Earth's surface.

The float (100) of claim 10, wherein the offshore float (100) has at least two decks, the first and second gas-insulated control stations being located on a floor where the floor is below the waterline or on a floor of an immediately adjacent level. lies.

A float (100) according to any one of claims 10 or 11, wherein the float (100) comprises a plurality of levels, the levels being separated by decks, at least one level being provided with upright walls, and for at least at least one level and two adjacent decks are formed as a torsion box using the upright walls.

The float (100) of any one of claims 10 to 12, wherein the offshore float (100) comprises a DC converter for converting high voltage AC power from the transformer to DC power.