Saturday, October 8, 2016

An AWEsome energy source: where do we stand with airborne wind energy?

Kite surfing on the ─▓sselmeer lake, in the Netherlands; a picture that I took a couple of weeks ago. These are not kites for airborne wind energy (AWE) but, for some reason, Holland is the country where the idea of energy kites seems to be most popular; in particular because of the work of the late Wubbo Ockels (1946 – 2014), pioneer of wind energy. The technology is promising, but there is a long way to go before it will become a commercial reality.

I have been following the development of airborne wind energy (AWE) for more than 10 years and I keep following it. This summer, I visited the campus of the Technical University of Delft, in Holland, where I met the people of "Enevate", the university spinoff dedicated to kite power, a field in which the university of Delft has been active for a long time. I found a dedicated group of young people, enthusiastic and competent, working hard at developing the concept. Recently, they scored a remarkable success obtaining the support of the EU Horizon program for the project "REACH" dedicated to airborne wind energy.

But where do we stand, today, with this technology? The idea of AWE is both simple and promising. The current generation of wind turbines work relatively well, but it is also a technology that's rapidly reaching its technical limits, given by the weight and the cost of the tower that supports the rotor. So, why can't we just get rid of the tower and have the rotor fly in the air? Think how much money we could save!

So, we fly a kite. The kite catches the wind energy and transmits it down to earth either by onboard generators or by pulling cables that act on a ground-based generator. This technology is called in various ways, but the term "Airborne Wind Energy" seems to have become the most common one. The development of this field has been going on for at least ten years. Some years ago, I wrote an early (rather overoptimistic) paper on the concept on "The Oil Drum." Recently, Euan Mearns wrote an also rather optimistic, but reasonably well-balanced, post on the subject. A much more negative review of AWE appeared in "GreenTech" as well as in another article published by some researchers of the Max Planck institute. You can find a recent review of the various technical implementations of the idea in a paper written by Cherubini et al.

So, where do we stand, today? There is no doubt that the concept of AWE is alive and well and that research on it is being performed in several laboratories all over the world with the support of governments and companies. The problem with all promising technologies is always the same: the promise must be kept. The technology must work and we can say that it does only if we have something that works and can be tested for a relatively long time. We don't seem to have arrived at that stage yet with AWE, but it is normal: research and development is a slow and expensive process; not something for mad scientists building spaceships in their basement. In my opinion, some early dreams of tapping the wind at very high altitudes, even getting energy from the jet stream, were much too ambitious. But that doesn't mean that the technology can't work. What can be done at the present stage is to work on small systems that go no higher than about 1000 m and that are manageable and relatively simple. Even for these systems, it takes time; there are still plenty of problems to solve. As somebody said, research is "1% inspiration and 99% perspiration". With AWE, there is still a lot of perspiration to do.

One problem when dealing with energy producing technologies is the "miracle trap." We all know that we have an enormous problem with fossil fuels in terms of both depletion and pollution. We need to replace them with renewable energy as fast as possible and most of us understand that it won't be easy (although not impossible). So, some people are actively searching for miracles and some found them in outright scams about cold fusion or mysterious unknown nuclear processes. Others use their faith on the miracles that will come as an excuse for doing nothing. And, finally, others have fallen into the opposite trap and tend to consider as a scam anything and everything that hasn't yet fulfilled its initial promises. Some people seem to have developed this attitude even toward AWE. But AWE is neither a scam nor a miracle. It is a technology being developed that needs to be studied and evaluated.

AWE may well fulfill an important role in energy production in the future but, for the time being, we need to deploy what works, and keep working on what's promising. And if we keep a cool head, we can make it even with what we have. We don't need miracles; we need to work for our future. And we need to start right now.



Ugo Bardi is a member of the Club of Rome, faculty member of the University of Florence, and the author of "Extracted" (Chelsea Green 2014), "The Seneca Effect" (Springer 2017), and Before the Collapse (Springer 2019)