An almost flat reservoir in the morning can be a completely different environment from an engineering perspective during a storm.
This is important to realize.
For a floating solar project, the answer to the floating SPL question is straightforward. Of course there are waves. Waves can be created by wind on any water body that is of considerable size. The important question here is whether the wave conditions are above the expected capability of the selected floats, connectors, mooring system, and electrical architecture throughout the lifetime of the plant.
But a second question arises:
Do we strengthen the floating system to cope with the waves, movement and rotation of the array, or do we make sure that the waves are dampened before reaching the system?
Floatex Solar believes that this aspect of wave protection should be considered in this way. The breakwater is hydrodynamic, not simply dependent on the size of the reservoir. This is also where floating solar engineering becomes important, because wave exposure has to be evaluated against the actual response of the complete system.
Start with fetch, not reservoir area
Not all positions within a proposed farm will be subject to the same wave forces.
The first design consideration is fetch, which refers to the distance of open water over which wind energy is transferred to the waves.
"Maximum fetch" may be somewhat misleading.
According to the US Army Corps of Engineers, an effective fetch refers to the distance the wind blows towards the location in question, and the maximum geometric distance across a reservoir does not always generate the maximum wave. Wind direction and velocity should also be taken into account. Significant wave conditions can still develop over a smaller fetch in the direction of predominant wind flow.
That gives us a more useful design picture for floating solar engineering.
| Site input | What we need to establish | Why it matters to FPV |
|---|---|---|
| Directional fetch | Open-water distance along important wind directions | Controls the distance available for wave development |
| Extreme wind climate | Speed, direction, duration and return period | Determines the energy available to generate waves |
| Water depth / bathymetry | Depth along wave path and around the array | Influences wave transformation and mooring geometry |
| Operating water levels | Normal, minimum and maximum levels | Changes depth, shoreline, fetch and mooring response |
| Wave period | Energy distribution across the wave spectrum | Can govern float motion and connector response |
| Array orientation | Heading relative to dominant waves | Changes how the floating structure responds |
| Shore geometry | Islands, bends, banks and obstructions | Can shelter, refract or redirect incoming waves |
In other words, a floating solar project should not receive a single label such as "calm reservoir" or "high-wave reservoir."
It needs a directional environmental design basis.
Wave height alone is not enough
One could simply define the maximum allowable wave height and leave it at that.
However, the science of this is far more complex.
A study released in 2026 in the journal Marine Structures demonstrated that FPV has a pronounced reaction to wave period and wave direction. Greater wave following was observed with larger waves, while shorter waves produced greater motion in windward floats. The reaction of the mooring also was greatly influenced by surge and heave.
This is critical because the resulting force depends on more than wave height alone, including wave period and direction.
What we are concerned with is the resulting response:
- relative movement between neighbouring floats;
- cyclic connector forces;
- pitch, heave and surge of the array;
- loading at perimeter and corner connections;
- peak and cyclic mooring-line tension;
- module and support-frame movement;
- cable bending, movement and restraint;
- wave overtopping or direct interaction with electrical components.
One recent publication concerning high-fidelity FPV analysis highlights the importance of considering the non-uniformity of the local force distribution since, in the rope-mesh structure, the connectors that run in the direction of the waves carried three to five times higher loads compared to the connectors that run perpendicular to the waves.
This is the reason why one should design according to the "wave height" and not according to the "controlling component." For floating solar engineering, that means assessing how the entire array responds to the environmental conditions rather than relying on a single wave parameter.
Most inland FPV does not automatically need a breakwater
It is important to note that there is an aspect of balance.
Wave damping does not need to be a standard procedure for all large-scale floating photovoltaic systems.
Wind pressure was the dominant factor in the majority of cases analyzed during a comparative engineering assessment of FPV systems on a small lake, large lake, and offshore. For the offshore system, which was open to the elements, waves were an important factor compared to other forces, making up around 50% of the environmental forces.
This is what we would expect physically because limited fetch can restrict wave development.
So for many reservoirs, the right solution can still be:
characterise the waves accurately -> engineer the float and station-keeping system for them -> do not add unnecessary protection infrastructure.
When should wave attenuation enter the discussion?
We would investigate attenuation more seriously when several exposure indicators begin appearing together.
These include:
- long effective fetch aligned with severe directional winds;
- wave conditions approaching or exceeding the qualified operating envelope of the chosen floating system;
- unacceptable connector, frame or mooring loads in dynamic analysis;
- persistent overtopping or green-water risk around critical equipment;
- high fatigue demand even when ultimate loads remain acceptable;
- a highly exposed windward perimeter controlling the design of a much larger sheltered array;
- reservoir geometry that gives one sector substantially greater exposure than the rest;
- situations where strengthening every downstream component costs more than reducing the incident wave energy.
Notably, project capacity is not on that list.
Wave exposure is probably going to be lower for the 200 MW plant located in an adequately sheltered reservoir compared to the much smaller one in a more exposed area of water.
Capacity affects scale. Exposure determines wave protection.
For a floating solar project, this distinction is important because capacity alone should not determine whether wave attenuation is required.
Wave attenuation also has to work for the actual spectrum
If the model shows that there is a need to shield against waves, then proceed with wave protection.
Nonetheless, this does not mean that all types of floating breakwaters will be effective.
The most common way of estimating wave attenuation is by comparing the wave height behind the protection structure with the incoming wave height. The lower the wave transmission, the greater the wave attenuation.
Nevertheless, it should be noted that the transmission coefficient depends upon the wavelength, period, width of the structure, draft, type of the wave motion and its direction.
The wave heights in FPV systems protected by a floating breakwater were reduced by up to 50–60% across part of the frequency range examined in the wave basin. At the same time, the transmission coefficient was almost 1 (no wave attenuation at all) at the lower frequencies.
More recent research has also established that the same principle applies: long-period waves are still much harder to buffer by conventional floating breakwaters, and wave attenuation strongly correlates with the wavelength-breakwater geometry ratio.
This places greater emphasis on the design process.
First, the waves to be attenuated have to be identified, followed by the selection of the attenuation system.
It should not be the other way around.
That sequence is central to floating solar engineering, particularly where wave attenuation is being considered as part of the array protection strategy.
Three possible responses to an exposed site
Wave attenuation is only one design lever.
| Site condition | Potential engineering response | Key consideration |
|---|---|---|
| Low/moderate waves within FPV design envelope | Engineer array directly for environmental loads | Usually avoids unnecessary infrastructure |
| Exposure concentrated from one direction | Reorient, relocate or locally protect the windward boundary | May solve the governing condition without protecting the entire plant |
| Higher waves causing unacceptable dynamic loads | Dedicated wave attenuation / breakwater system | Requires hydrodynamic and mooring design of its own |
| Very severe or broad-spectrum exposure | Reconsider FPV technology, site zone or structural concept | A conventional reservoir FPV system may not be appropriate |
| Different exposure across reservoir | Segment plant into environmental design zones | Avoid designing every MW for the worst local condition |
There is no need for the reservoir to fall within only one environmental classification category. One 5 MW island might be located in an area with natural shelter, while another might face the maximum fetch within the project.
If both islands are considered equal, it may either lead to underdesign or overdesign.
A breakwater becomes another floating structure that must survive
There is another mistake we try to avoid: treating wave protection as if it removes engineering risk without creating new risks of its own.
A floating breakwater has:
- buoyancy and stability requirements;
- its own motion response;
- anchors and mooring lines;
- connections;
- fatigue cycles;
- inspection requirements;
- storm survival conditions.
Modular floating breakwaters have been researched explicitly for fatigue damage to connection joints caused by repetitive wave loading.
In the latest physical tests, it has been shown that the attenuation capacity of the attenuator is influenced by variables such as the relative width of the structure, wave direction, water depth, and wave steepness. Relative width of the structure was the most critical variable among the many studied in one 2026 study.
Thus, the attenuation system has to be designed to perform reliably throughout its service life.
Before specifying it, our floating solar engineering questions include:
- What return-period wave condition are we designing against?
- Which wave periods are producing the critical FPV response?
- From which directions do those waves arrive?
- How much attenuation is actually required—not simply desirable?
- What transmitted wave spectrum will remain behind the structure?
- How does the breakwater behave at minimum and maximum reservoir levels?
- What are its own extreme and fatigue mooring loads?
- Can a breakwater failure create a new hazard for the solar array?
- How will it be accessed, inspected and repaired through the plant life?
If those questions cannot be answered, adding a breakwater can give the appearance of protection without demonstrating it.
Protect the array only as much as the site requires
Wave engineering should not be done with the intention of making the water around the floating solar power station perfectly still.
Rather, the aim is to make sure that the structure behaves within the set limits of the system; the loading and fatigue on the mooring, electrical movement, among other factors, remain within those limits.
Sometimes, all that is needed is to ensure that the array achieves this.
In other cases, simply adjusting the orientation, segmentation, or location might be all that is required.
In some locations, wave attenuation may be essential to protecting the structure.
The decision should emerge from wind climate -> directional fetch -> wave modelling -> FPV response -> allowable limits -> protection design.
That sequence is important to understand.
We see this as the difference between putting up a solar system on a water body and engineering a floating solar system to operate there for the next 25 years. That is ultimately the role of floating solar engineering: matching the protection strategy to the site's actual exposure rather than assuming that every project needs the same level of wave protection.
