CalWave concludes 10-month test of its submerged wave energy generator

CalWave concludes 10-month test of its submerged wave energy generator
CalWave's xWave generator after 10 months of fully submerged open-ocean testing
CalWave's xWave generator after 10 months of fully submerged open-ocean testing
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CalWave's xWave generator after 10 months of fully submerged open-ocean testing
CalWave's xWave generator after 10 months of fully submerged open-ocean testing
Towing the xWave generator back in from its test site
Towing the xWave generator back in from its test site
Next up: a 100-kW xWave will be tested at the PacWave installation off Oregon
Next up: a 100-kW xWave will be tested at the PacWave installation off Oregon
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CalWave has been working on its xWave clean power technology for many years now, and has announced the successful conclusion of an extended open-ocean test off the coast of San Diego, in which the device demonstrated over 99% system uptime.

Wave energy is one of the less common renewable energy sources, and while there are many wave energy projects under development, the industry itself can be considered more or less embryonic at this stage. There's some promise in it; as CalWave points out, "ocean waves are 20-60 times more energy-dense, predictable and consistent compared to other forms of renewable energy."

On the other hand, extracting that energy is proving tricky. The ocean is a famously harsh environment for man-made objects, and energy assets need to pay off their significant capital expenses over decades of continuous operation to attract investment dollars. Most projects seem to stay in the testing phase for an awfully long time, and nothing to date has managed to go commercial on a grand scale.

CalWave is probably a good example; this company has been announcing the successful completion of tests since at least as far back as 2016, when it had a miniature 1/20th-scale model running in a test basin. The xWave is a boxy, buoyant little platform that's towed out to sea and anchored to the sea floor, with a tether length that holds it fully underwater.

Towing the xWave generator back in from its test site
Towing the xWave generator back in from its test site

The company is curiously vague in its communications about how its xWave device actually works. Indeed, here's the clearest statement we can find. "As a wave passes over the top, you get a pressure wave that causes motion relative to the sea floor, and with our anchors on the sea floor, we convert that relative motion to power," said COO Dan Petcovic in a 2021 video. From this, and some CAD illustrations in the same video, we assume that the xWave has four spools connecting cables to the sea floor, and it generates energy as these spools wind and unwind while the platform is pushed around by the waves.

Running it underwater, says the company, protects the xWave from catastrophic damage when the ocean's in a bad mood. These spools can also be automatically and individually braked to different degrees when the device gets pummeled by unusually large waves, to buffer the more extreme forces such that it can either shut down altogether, or retool itself to harvest energy from weather that would put other renewables out of commission. CalWave says the device's resiliency is the key to its market advantage, and that it should end up being a much lower-cost device than others in the space.

The most recent open-ocean test was scheduled for 6 months, but was extended to 10 months. CalWave says the x1 platform "achieved high performance as targeted and predicted," that it operated under fully autonomous control for about 80% of its operating time, that it demonstrated more than 99% uptime with zero operator interventions, and correctly shut itself down during particularly rough conditions with waves up to 15 feet high.

Anti-corrosion coatings and sacrificial anodes helped to prevent rust, and the company trialed an anti-biofouling coating as well, noting that uncoated areas did experience some biofouling, but that these didn't including moving parts, and there was no impact on operations. A third-party assessment verified it posed no danger to marine life.

So how excited should we be? I'm not sure, honestly. We don't know, for starters, how much power the thing produces. We do know that the company's next move will be to deploy a 100-kilowatt version of the xWave to be tested off the coast of Oregon for two years at PacWave South, "the nation's first accredited, grid-connected, pre-permitted wave energy test facility." The company's "utility-scale" designs are called the x100 and x800.

Next up: a 100-kW xWave will be tested at the PacWave installation off Oregon
Next up: a 100-kW xWave will be tested at the PacWave installation off Oregon

Frankly, anything operating at the kilowatt scale might be of some interest to islanders and small coastal communities, but these kinds of numbers aren't really relevant to national energy grids looking to scale up and decarbonize energy production. Indeed, CalWave's stated target of deploying 1 GW of commercial marine energy technology by 2035 is depressingly humble; in 13 long years' time, the company hopes to have rolled out a capacity around that of a single average nuclear power plant.

If we assume that the x800 is an 800 kW unit, that suggests CalWave will need to make 1,250 unit sales to make that happen. Still, who knows? It'll all come down to Levelized Cost of Energy (LCoE); if this gear can sit out there pounding out electricity for decades, asking little in terms of maintenance and delivering energy back to shore at a fraction of the cost of other offshore generation technologies, it'll sell. If it can't, it won't.

The closest we can find to a projected LCoE for this device is a 2018 evaluation of the top wave energy converters tested at 1/20th scale as part of the Wave Energy Prize contest. A team of researchers split between the Sandia National Laboratory and the National Renewable Energy Laboratory put together its own "ACE" metric by which to evaluate the cost of energy from small-scale, early prototypes, and on this metric CalWave's device ranked reasonably well against other wave energy devices evaluated, sitting somewhere around third overall. On the other hand, from what we can tell, that prototype generates power using a different mechanism than the current prototypes.

Obviously, projections are just educated guesses, but with LCoE being of critical importance to these technologies' success, that's something investors – and technology fans in general – should be demanding some kind of figures on.

One final thought: CalWave says its recent 10-month test period exposed the xWave generator to two storms "representative of the largest storms in a 10-year period for a utility-scale system." And indeed, how many times over the last few years have you heard about "once in a century" weather events?

These early days of climate change appear to have brought with them a rapid increase in the frequency of severe weather events, and it seems reasonable to expect that we'll see more and more over the coming decades. We hope CalWave and the many other renewable energy projects in planning are factoring unprecedented extreme weather events into their designs.

Check out a short video below.

CalWave test

Source: CalWave

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The nice thing about (relatively) smaller installations is that they may provide some resilience. Bad conditions are less likely to put all of them offline at the same time.
Doug Houseman
Mechanism is buoyant boxes in the frame that move up and down as the level of water over the top increases/decreases. Those boxes create mechanical energy that is converted to electrical energy. This based on analysis of photos of the system. I have no inside knowledge. System should avoid many of the animal and air/water interface issues that stopped other systems. Energy conversion efficiency is the big question.
I spent my working life maintaining ships sailing on the worlds oceans. The maintenance nightmares that these invoke are frightening. Possibly they just bring them ashore? The cables? Cables under tension need to be maintained. Cables under tension under salt water will probably need replacement in 1-3 years. We replace lifeboat cables that are sitting in a reel and mostly unused after ten years. 5 years we swap them end to end, and they are strength tested annually. And the reels themselves? Where is the generator? On the other side of a seal so the reel can turn a generator? I just can't imagine how they could design this in such a way that it would still be running in 5 years. That's being generous.
These are crude estimates, so bear with me: One xWave X1000 running at 100% capacity factor will generate 8766 * 100 kW = 876.6 MW-h annually. My guess at the average CAISO market price is $60/MW-h, so one X1000 would gross about ($60 * 876.6 MW-h) = $52,596 per year. That hardly seems enough to cover installation and the inevitable maintenance (with enough left over to run a company), but I welcome alternate viewpoints and corrections to my math!
Peter Foley
Possible off grid power supply, very high maintenance,
Very high local environmental changes from wave moderation, such as lower smaller surfing waves, lower gas exchange between sea & atmosphere.

Far greater climate impact then any Co2 burning power source.

Wave action speeds up take of water into air, more wave power = less downwind rain....
what stops larger boats or sailboats with their deep keels from hitting the units and destroying both?
Wave energy has been touted for at least 40 decades. So, this current version should be more than mature enough that government subsidies are necessary. Not even the stealth subsidies when fossil fuel power plants are required to have capacity to serve as batteries for when this "more consistent" isn't providing power. Or changing the billing structure, to discourage the extra reserve capacity that fossil fuel plants have traditionally had, like what happened in Texas a couple of years back.
Maybe build a smaller scale unit and then assemble them into arrays for deployment in the Great Lakes so there is less corrosion. In winter, tow them in for cleaning and maintenance and redeploy when the ice clears.