From the article:

[Company] has tested a small model of the reservoirs in wave tanks and off the coast of Reggio Calabria, Italy. It’s now deploying a pilot of the floating components in advance of a full demonstration plant. By 2026, it’s hoping to deploy several commercial projects at sites around the world.

At full size, the turbines would generate around 6 to 7 megawatts of electricity each, and there will be one for every 100 meters of pipe. Deeper sites would have more storage potential, and each commercial site would host multiple reservoirs. Sizable hopes to deliver energy storage for €20 per kilowatt-hour (about $23), about one-tenth what a grid-scale battery costs. —-

Testing in calm reservoire is different from potentially .wild offshore (ocean/sea)

What happens to 100-200 m long pipe in underwater waves when e.g. a hurricane or a storm comes?

> What happens to 100-200 m long pipe in underwater waves when e.g. a hurricane or a storm comes?

Nothing, to a rounding error. The effects of surface storms are only noticeable to ~2x wave amplitude.

There are plenty of other forces at work, especially tides, but storms will only affect the surface plant.

What happens to 100-200 m long pipe in underwater waves when e.g. a hurricane or a storm comes?

That’s an excellent question, but it is also similar to asking what will happen to wind turbines in a storm.

Maybe some will break. Maybe that’s an acceptable outcome. Probably they can be improved to reduce that risk

Even in a storm, just a few meters below the surface (half the wavelength), the sea will be calm.

The bigger issue with this idea is that it's a megastructure sitting in the ocean, and salt water turns everything it touches into shit. Oh, and there's very little energy storage potential from just a salt gradient. You need to move way more water, to get less energy, but your container costs are fixed.

Land-based pumped hydro has no shortage of engineering problems (and risks if, you know, you get a dam collapse), but this has colossal capex costs.

It's anchored to the seafloor. Also surely we have the technology to hold a pipe in high sea, as this is what petrol platforms are doing.