Fishery Solar Mounting System for Aquaculture Ponds

What Is a Fishery Solar Mounting System?

A fishery solar mounting system is a pile-supported PV structure built over a working aquaculture pond. On land, a ground-mount array stands on ground that rigs and trucks can drive on. Over a pond, the piles usually go into soft, saturated silt, and the waterline around them rises and falls with rain, drainage and harvest cycles. The steel frame sits in constant humidity above a splash zone at the waterline. Below the modules, the farm needs room for boats, feeders, aerators and harvest nets.

Fishery PV and fishery-solar hybrid describe the same project type, common in China and parts of Southeast Asia on freshwater fish and crab ponds, brackish shrimp ponds and coastal aquaculture ponds. Researchers use the broader term aquavoltaics, which also covers floating arrays. The appeal is dual use. One pond produces both fish and electricity, and in hot months the shade from the modules can also lower water temperature and evaporation.

Parts of a Fishery PV Mounting Structure

In a fishery PV mounting structure, loads pass from the modules through the clamps, rails and beams to the piles and into the pond bed.

The pile then passes those loads into the soil. Skin friction, the grip between the pile surface and the surrounding soil, works with end bearing at the tip to support downward loads. The same friction, helped by the pile's weight, resists wind uplift, and the soil pressing against the pile takes lateral loads.

Frame layout sets how many piles go into the pond. Single-post frames keep the pile count low and leave wider gaps between piles, although each pile carries a larger bending moment. Two-post frames spread the load over more piles. Stretch the spans to widen boat lanes and you cut the pile count, but the beams get heavier. With the same load per meter, doubling a beam's span roughly quadruples its bending moment and increases its deflection about sixteenfold.

How Pile-Mounted, Floating and Cable-Supported Systems Compare

Rigid pile-mounted frames suit shallow ponds whose beds can take driven piles, and they hold modules at fixed tilt or on single-axis trackers. Floating PV handles deeper water and large water-level swings, because its pontoons rise and fall with the water while moorings tied to the bed or banks hold them in place. Cable-supported systems, often called flexible mounting, are used where a site needs long spans, and they usually stand on piles too. They carry modules on prestressed steel cables strung between widely spaced supports. Fewer supports stand in the water, but cable tension, anchor loads and vibration need close checking.

Pond depth, bed soil strength and storm exposure decide which structures are practical. The drainage cycle and how much open water the farm needs under the array then narrow the choice.

Clearance Height and Row Spacing Over the Pond

Why not just set the array high and leave plenty of margin? Because every added meter of clearance lengthens the supports, raises the overturning moment where each pile enters the bed and adds material to every frame. The practical aim is the lowest clearance that keeps the array above floodwater and still leaves the farm room to work.

How High Should Modules Sit Above the Water?

The lowest point of the array has to clear the highest farming water level by the headroom that boats and nets need, and the design flood level by a freeboard margin. The farming level comes from the farm's operating plan, and the flood level from a hydrological study of the site.

Freeboard keeps modules and connections clear of wind-driven waves, floodwater and floating debris. Both clearances are measured to the lowest member, which is sometimes a beam or brace below the module edge rather than the module itself. Whichever needs the higher elevation governs.

Clearance set from a dry-season survey can fall short in the wet season, when workboats lose headroom and nets start catching on low beams and braces. Ponds harvested from the banks or by draining can often work with modest headroom. Farms that run workboats under the array need enough room for the boat, its crew and any nets or gear on board.

How Pile and Row Spacing Affect Light and Access

Over a pond, row spacing limits winter shading between rows, controls how much light reaches the water and sets the width of the lanes that boats and nets use. Along each row, the distance between piles depends on how far the rails or purlins can span and how much load each pile can take. A workable layout also keeps harvest zones and fish channels clear of piles, spaces supports to suit the farm's nets and leaves room around feeders and aerators.

For a sense of scale, a 2024 study published in Water examined a 20 MW plant in Fujian, China, built over coastal mud crab ponds 0.4 to 1.4 m deep. It reports piles at 5.0 m (16.4 ft) centers and rows 7.8 m (25.6 ft) apart. Module centers sat 2.35 to 3.02 m (7.7 to 9.9 ft) above the water. The clearance under the beams and braces was lower. Those figures describe a single site with 80% PV coverage.

Pile Foundations for Soft Pond Beds

Most pond beds have soft, saturated silt over firmer clay, sand or weathered rock, and the depth of that firmer layer largely decides pile length. As with pile foundations on land, the piles pass through the silt and develop most of their capacity in the firmer layers below. Water depth and the height of the pile top set the free length of pile above the bed. A longer free length increases the bending moment where the pile enters the soil. Before production piling starts, the foundation designer usually calls for load tests on a few piles to confirm compression, uplift and lateral capacity in the actual soil.

Why Pond Projects Use PHC Pipe Piles

PHC pipe piles are hollow, prestressed concrete piles spun-cast in a factory. For pond work they offer consistent quality, durability in permanently wet ground and a unit cost that suits projects needing thousands of piles. Often the pile also rises above the water and doubles as the column.

Installing Piles in Drained or Flooded Ponds

Piling in a drained pond is common on working farms. Land-based rigs work from mats or temporary platforms between production cycles, and a late start can push piling into the next farming season. If your ponds cannot be drained, or draining would take them out of production for too long, piles go in from pontoons, barges or the nearby banks. Floating equipment costs more, and platform movement makes it harder to hold each pile in position and plumb.

Corrosion Protection at Inland and Coastal Ponds

One fishery structure faces three corrosion environments at once. The pile shaft stays submerged or buried, and limited oxygen there slows corrosion. The upper frame is exposed to humid air. Between the two lies the splash zone at the waterline, where daily wetting and drying with plenty of oxygen breaks down coatings fastest. On a concrete pile that rises through the waterline, the splash zone falls on the concrete, and the coated steel begins at the pile top.

Zinc protects galvanized steel by corroding first, and chlorides from brackish pond water or sea spray speed up that loss. ISO 9223 grades how corrosive a site's atmosphere is, from C1 (very low) to CX (extreme). The categories below are typical starting points, and a site assessment sets the actual category.

Zinc wears away faster with each step up in category. For an 85 µm hot-dip galvanized coating on heavy steel sections exposed to the air, ISO 14713-1 estimates the time to first maintenance at 40 to more than 100 years in C3, 20 to 40 years in C4 and 10 to 20 years in C5. A collar or brace set low enough to catch wave spray will lose zinc faster. Near the coast, a coating that would need no maintenance over 25 years inland may need to be thicker or paired with a paint system.

On galvanized steel, corrosion usually starts where water collects on the lower frame members and connections. White zinc corrosion products appear first, and red-brown rust follows once the zinc is used up. Good detailing slows that process: joints kept above the splash zone, drain holes added to hollow sections before galvanizing, and zinc-rich paint on field cuts or drilled holes. Repairs near the waterline mean working from a boat or draining the pond.

Wind, Storm and Flood Loads on Open Water

Wind usually governs the structural design of a fishery array. Open water has almost no surface roughness to slow the air, so wind at module height blows harder over a pond than over farmland lined with hedges and buildings.

Fishery PV has no dedicated international structural code. Engineers apply general wind codes, using the site's wind speeds and surrounding terrain. Large multi-pond sites often fall into each code's open-water category.

Rows at the edges and corners of an array see higher pressure coefficients than interior rows. The structural engineer checks those frames and their clamp positions separately. On sites exposed to typhoons, hurricanes or cyclones, repeated gusts also put a cyclic load on the connections.

Over time, that cyclic loading can reduce bolt tension, which is why lock nuts or serrated flange nuts and torque checks after severe storms are common practice. Once preload is lost, the clamp grips the module frame less firmly, and the module can shift, rattle and flex in gusts. Repeated flexing may cause cell microcracks too fine to see.

The piles are checked against the design flood level as well as the farming water levels, since floodwater can push floating debris against them. In cold climates, piles are also sized for the sideways push of expanding ice and for ice that freezes to the pile and pulls upward as the water rises.

Fishery Solar Mounting Systems From Mibet

A fishery structure works best when its design starts from the pond's own water levels, bed soil, farming routine and corrosion exposure. Mibet supplies pile-mounted fishery solar mounting systems from the pile top up. The scope covers adjustable bolt-on collars that clamp the frame to each PHC pile, zinc-coated steel main beams and bracing, anodized 6005-T5 aluminum rails, mid and end clamps, and SUS304 stainless steel fasteners. Mibet's 2023 projects included a 44 MW fishery PV plant in Zhangzhou, China.

If you are planning a fishery PV project of your own, share your pond plan, water levels and any soil data with us for a preliminary layout and quotation.