One of the persistent myths of wind energy is that vertical axis wind turbines (VAWTs) are better than the iconic three-bladed horizontal axis wind turbine (HAWTs). A wrinkle on this myth has surfaced over the past couple of years, that the balance of engineering compromises favours VAWTs for offshore applications. It’s true that offshore applications have some different conditions which might favour VAWTs over HAWTs, but what is the status of the efforts in this space? Should this rumbling be given credence?
First up: the SKWID by Modec, a Japanese marine engineering company. It’s an interesting concept, and possibly viable at some point in the future. It is intended to have a Darrieus wind turbine above water and a Savonius-style generator capturing currents below water, both supported by an anchored floating platform. It’s intended to be towed into place to provide additional electricity to remote offshore or island installations. The first prototype was in test in late 2013, and its output was as expected fairly low. Useful for its niche, but far from being competitive with HAWTs for utility-scale generation and not intended to be.
But then the prototype sank.
Of course, in the discussion where this was first referenced, it was stated that the Japanese government was investing heavily in utility-scale offshore VAWTs instead of offshore horizontal-axis wind turbines, which turned out to be inaccurate, wishful thinking by a VAWT advocate.
The Japanese reality of wind energy, of course, is floating platform HAWTs such as the ones now generating electricity offshore from Fukushima. Price is still high, but supportable with the rich Japanese feed-in-tariffs for renewables instituted after the Fukushima tsunami.
Next is the Nenuphar device (visualization on left), by a French company, which was touted when referenced as a significant investment by the government of France in offshore VAWT technology. Nenuphar is intended to be a helical Darrieus VAWT, a moderately common approach.
It stalled in December 2012 with a stump of the base constructed.
It’s worth looking at the commentary of the CEO of Nenuphar:
Indeed, Nenuphar CEO Charles Smadja said that based on performance alone, horizontal axis turbines would always be superior to their vertical axis equivalent.
However, Smadja believes that vertical-axis turbines come out on top in terms of cost of energy and installation. The low centre of gravity makes the machine more stable and minimises the gyroscopic effects.
That’s not a stunning endorsement backed up by referenced numbers and it’s certainly not an apples-to-apples LCOE comparison. The targeted 2MW VAWT would not be the biggest ever built — the long defunct 4 MW Eole Cap-Chat in Canada holds that record — but it would be the second biggest and with a different design, multiplying engineering challenges. If it actually launches and doesn’t rattle itself to bits, it will be interesting to watch, but initial offshore deployment has been delayed by three years so far.
Sandia has decades of experience developing and improving wind-turbine technology. They performed extensive R&D on vertical-axis wind turbines in the 1970s and 80s, none of which resulted in economically viable products in the long-term.
They are dusting off 30- to 40-year-old research into VAWTs that was shelved due to the proven superiority of HAWTs and doing further modelling to see if the comparative compromises are in favour of VAWTs offshore, as they weren’t in onshore applications. They are spending about $4 million on this effort. They are doing modelling to see if the lower centre of gravity and relative mechanical simplicity are advantageous, and thinking that it is possible to scale VAWTs up to the 10-20 MW range (although the biggest VAWT ever built was 4 MW and failed after six years).
This is a reasonable and small side bet in a rich industry. It’s not a major investment or commitment, but a research exercise by an organization with a long memory and a lot of investment in intellectual capital related to VAWTs. It’s conceivable it might turn into something. Once again, it’s a long way from any production capability in offshore VAWTs even if the results of modelling are favourable.
The next great hope was the Deepwind project in Europe. They proposed a simplified, long-shaft floating VAWT. It was established in 2010 as a four-year research project with one of the work packages devoted to creating a prototype. Their website shows no press releases since early 2011. As of early 2013, they were still presenting purely hypothetical designs with no physical prototypes. There’s no real evidence of movement subsequent to this.
Is Deepwind going to produce something of use? It’s worth quoting what they actually expect to get from the project:
The project comprises research on an emerging high risk energy technology. The project is to a large extent based on previous knowledge and development in vertical axis technology, but it is combined with recent deep sea-based offshore technologies and with advanced, large scale blade pultrusion technology in order to establish a new field of development. The expected results will reflect this new combination of different technologies, and will primarily give answers to whether the proposed technology has a chance to emerge into a development of large scale wind turbine systems based on the proposed concept. More specifically, the project work packages will result in a range of proof-of-principle tests and development of a toolbox of design tools that will support the overall key question.
To paraphrase, no working offshore VAWT will be delivered, but hopefully a discovery of whether it’s viable and a bunch of learning and tools that are useful for offshore efforts in general are targeted.
Next up is the Norwegian Gwind research project, which was also referenced as a hopeful contender to displace utility-scale offshore HAWTs. It’s yet-another-helical Darrieus VAWT design, this time with the secret sauce being gyro-stabilization in the base.
As this presentation shows, their intent isn’t actually displacing offshore HAWTs, but selling supplementary generation to remote waterborne facilities such as oil rigs and fish farms.
At least this device has actually made it to a small-scale prototype that was launched in September of 2013. Results aren’t in, but regardless, moving from a single small-scale research prototype to a production offering two orders of magnitude larger is a long and arduous road. Unlike the only other approach in this list to actually make it to a floating prototype so far, it apparently hasn’t sunk.
Finally, there is Vertiwind, a sub-project of the INFLOW program, which is at least a year behind in floating any VAWT. They claim to be the world’s first multi-axis VAWT, although it looks like just another Darrieus VAWT that exists only as a computer graphic.
Prior prototypes were solely onshore and they are far behind on their goals.
Their last press release was only able to tout their new website design as a win. That’s always a bad sign.
Claims were also made that the US National Renewable Energy Laboratory (NREL) was investing heavily in offshore VAWTs. I could find no evidence that this is true.
These projects were focused on solving the specific and known technical problems of scaling up offshore horizontal-axis wind turbines. The Upwind project resolved and prototyped components sufficient to overcome the engineering challenges of 10 MW devices, and has been proved by an 8 MW HAWT moving into production at a European testing facility in January 2014. The Innwind project is focused on resolving the known technical challenges with scaling to 20 MW offshore HAWTs and is funded to the tune of $30 million, multiples of Sandia’s much-earlier-stage research.
After reviewing all of the touted “heavy” investments by countries that will displace offshore HAWTs, we find research projects, a couple of small scale prototypes, and a lot of delays. And we see that the ongoing investment in research to scale HAWTs is much better funded and hitting its marks more clearly.
What about reality of offshore wind energy production?
There is real and rapid growth in offshore wind capacity. It’s not equal to onshore capacity by a long shot, and it costs more up front, but there are over 7 gigawatts (GW) of real, production, offshore HAWTs generating utility-scale electricity today. (By comparison, there are about 300 GW of onshore HAWTs today.)
There isn’t a single production VAWT in the water anywhere in the world and there’s no real indication that any of these research projects will reach fruition with something that’s competitive with HAWTs. If someone brings up offshore VAWTs as the sweet spot for this technology, you can be fairly sure that they are an enthusiast with little actual knowledge of what is occurring in the real world, or possibly just someone who hates the iconic three-blade wind turbine and is willing to believe anything negative about them.
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