Lai Chau 100 MW Floating PV: Anchoring Design and Construction Progress

Published: October 27, 2026 | Author: Weltrus Energy Team

A Weltrus floating array taking shape on the reservoir at Lai Chau. Modules are already down on the pontoons, and the array is held out on the water while construction continues.

Why Lai Chau Needs a Sunk Anchor

Lai Chau is a large-water floating plant, not a short line of modules beside a bank. The arrays sit well offshore, and there are many of them. A rope run back to shore would be long, crowded, and a poor hold once several arrays share the same reach of water. Weltrus therefore anchors this project with sunk blocks on the bed. That choice is the starting point of the application scheme for the site: Phương án ứng dụng hệ thống neo cho dự án quang điện nổi trên mặt nước 100 MW tại Lai Châu, Việt Nam.

Depth adds a second constraint. In deep water a block goes down slowly. The drop takes time, the block can land off the mark, and the rope that follows is long. The work quantity and the construction difficulty both rise. The practical answer is not a heavier copy of the same layout. It is fewer blocks and fewer ropes, while the array stays secure. That is why the Lai Chau design uses a Y-type pattern. Edge anchor points on the array and blocks on the bed are set at 2:1 or 4:1, chosen from the size of that array and the depth under it. One block serves more than one point on the edge. The layout stays safe, the blocks the crew must place go down in number, and the construction cost stays in line with the water in front of them.

The third constraint is the water level itself. Lai Chau moves. Rope length is designed from the maximum depth, and the way the rope is shortened or lengthened has to match how far the water moves and how often. A small change needs no crew. A slightly larger change can use a preset line that pulls the array back on its own. A large change on a long cycle can stay manual, which keeps the first cost down. A machine costs more up front. A fully automatic adjuster costs more still, and it earns that cost only when the swing is both very large and very frequent. On this project the provided water-level range is 40 m. Weltrus took that range, the depth, and the construction sequence together, and selected the Y-type sunk anchor with a five-section line that a crew can reset by hand.

The Y-Type Design Weltrus Is Applying

The design now guiding construction has three decisions in it, and each one is there to make the build possible.

First, the hold is a sunk block, because the arrays are far from shore and there are many of them. Second, the blocks are shared in a Y, at 2:1 or 4:1, so the bed is not covered with one block per edge point. Third, the line itself is built in five sections: anchor chain, wire rope, elastic rope, and two further wire-rope sections. The maximum length that line may need to be adjusted is estimated at 40 m for now, matching the water-level range the project supplied. As construction proceeds, each array takes the ratio and the mid-rope length that its own depth requires. The method stays the same across the plant.

This is a construction design, not a paper comparison of every anchoring product on the market. It tells the crew what to place, what to leave slack, and what to pull when the reservoir moves. The photographs from the site show that work happening: pontoons and rails going in, modules going down on the deck, and finished stretches of array already sitting on the water.

Line Build, Adjustment, and Site Work

The figures below are the design Weltrus is using at Lai Chau. Lengths that the scheme gives as a range are kept as a range. The 40 m adjustment is the current estimate from the water-level data, and the working adjustment the crew plans for is about 30 m once the lowest 10 m is left to the chain.

Weltrus installers fitting modules onto the pontoon deck. Walkways, floats, and module rows go in together so the array can be extended across the reservoir.

Five sections, each with a job

The bottom section is anchor chain, cut at 10–15 m. When the water falls only a little and wind pushes the array off station, that chain does the first correction by itself. Its weight draws the array back toward the original area, within a limit, and nobody has to climb on the bracket. That is why the lowest 10 m of level change is left alone. The rope above the chain only has to cover about 30 m of adjustment, even though the full range used for the design is 40 m and the maximum adjustment is still estimated at 40 m until the next site check.

Above the chain, the lower wire rope is made to the length that array needs. It is the piece that changes with depth, so it is fabricated to the callout rather than pulled from a single stock length for the whole 100 MW. The elastic rope in the middle takes up the difference when two lines on the same array are not exactly equal. It is there so a small mismatch does not leave one corner tight and another slack. It is not a substitute for cutting the wire to the right depth.

The two upper wire-rope sections are each 10–15 m. Both ends of each section keep a lock and a thimble, so the crew can pick the section up and pin it without splicing on the water. When the level drops more than 15–20 m, they haul the mid-upper thimble up and fix it on the anchor bracket. When the drop passes 30–35 m, they do the same with the middle thimble. When the water rises again, they run the steps backward and pay the line back out. The first cost stays below a mechanical or automatic system. Later adjustments stay short, and the crew spends less time on each reset.

Four ratchets when the array is too large to pull by hand

A small array can be walked back into place. A large one cannot. On those arrays Weltrus sets a simple ratchet at each of the four corners, each ratchet facing one direction. The crew winds the array back to station, then fixes the lower thimble on the bracket and leaves the line set for the new level. The ratchet is a construction and maintenance tool for the big blocks of the plant. It does not replace the five-section line. It makes that line usable once the array is wide enough that arm strength is no longer enough.

What construction looks like now

On the reservoir, the work is already past the drawing. Floats are linked into a deck. Metal rails run the length of the rows. Crystalline modules are going down on that deck, row by row, with installers working from the pontoon walkway rather than from a boat alongside every module. Stretches of array are already complete enough to read as a floating plant: a long rectangle of modules on white pontoons, held out from the rock bank, with more deck still open for the next rows.

That sequence matches the anchoring logic. The deck has to exist before the edge points can be tied to the Y-type blocks, and the blocks have to be down before the array is trusted to a change in level. Weltrus is building both together: the array the photographs show, and the sunk-anchor line the scheme specifies. Visitors looking at one finished rectangle should read it as progress on the 100 MW plant, not as the whole plant in a single frame. The same method, the same five-section line, and the same 2:1 or 4:1 block layout extend across the arrays still to come.

Site work of this kind also explains the adjustment design. A crew that is already on the pontoons can pull a thimble and pin it. They do not need a separate automatic machine for a 40 m range whose cycle allows a manual reset. The chain covers the small daily movement. The thimbles cover the large seasonal drop. The ratchets cover the arrays that have grown too wide to haul by hand. Each piece is sized to the way this reservoir actually moves.

What Still Follows Each Array

The method is set for Lai Chau. A few numbers stay with the array in front of the crew, because the scheme itself treats them that way.

• 2:1 or 4:1 is chosen per array. Both ratios are part of the design. Array size and water depth decide which one that block of the plant uses. The plant is not locked to a single ratio on day one.
• The 40 m figure is the current design estimate. It follows the water-level range provided for the project. The working rope adjustment is about 30 m, because the lowest 10 m is left to the chain. A later depth check can refine the mid-rope cut. It does not change the five-section build.
• Chain and upper wire are 10–15 m, not one stock length. The crew cuts inside that band and leaves thimbles on the wire. The elastic section only evens the lines out.
• Manual reset is the selected method for this range and this cycle. Preset, mechanical, and automatic options were reviewed. Manual, plus chain weight and corner ratchets, fits the cost and the way the water moves here.
• Module mechanical load still follows the float support. The anchoring scheme sizes the mooring line. The module datasheet and the pontoon manual size clamps and walkway load. Weltrus matches those two documents on the model that goes on each row.

Partners who want the same approach on another reservoir can start from this case. Send the water-level range, the depth, how far the arrays sit from shore, and the module code you want on the deck. Weltrus will set the block ratio, the five-section lengths, and the reset method the way they are being set at Lai Chau, and will align the module row with the pontoon support already going in on site.

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