The problem is that the wind shifts slightly and instead of the wake turbulence enhancing the airflow over the next turbine it is disrupting it.

The main issue with egg beater technology is not aerodynamics. The main issue is keeping the sand out of the massive thrust bearing that holds these things up. That has always been the main issue.

Thanks for the review, Mike. Overall I found it quite reasonable, though we obviously reach different conclusions about the merits. Four points of correction:
1. Sandia's experimental program studied individual VAWTs, not arrays.
2. You state "He found that, unsurprisingly, differences in wind directions diminished the performance advantages for downwind VAWTs." In fact, we found the opposite: pairs of VAWT are largely insensitive to wind direction. See, e.g., figure 4a in the 2011 paper.
3. The statements "existing renewable energy technologies require substantial land resources in order to extract appreciable quantities of energy. This limitation of land use is especially acute in the case of wind energy" and "This solution comes at the expense of higher engineering costs, and greater visual, radar and environmental impacts" come from the same 2011 paper. In fact, they come from the same paragraph in that paper. The article gives the reader the incorrect impression that there has been a shift in our motivation for VAWT arrays, which is a bit disingenuous given the aforementioned placement of those statements. In any case, I think we probably agree that the most important metric is the levelized cost of the electricity.
4. You refer to "the level laminar flow necessary for his arrays to be most effective." In fact, the VAWT arrays we study in the field are in higher levels of turbulence than typical HAWT farms. Turbulence tends to decrease with altitude, so being closer to the ground (e.g. at 10 m vs 100 m) means turbulence is unavoidable.
These points aside, thanks again for providing a critical eye. As you know, wind energy has lots of snake oil salesmen, so I think your skepticism is healthy for the field. It's also why we are careful to limit our claims to what we can demonstrate in the field and publish in the peer-reviewed literature. I'll keep you posted on our current field test (now up to 24 VAWTs), which continues to support our hypothesis. More to come...
JOD

The problem with VAWTs is that they can only harness the wind's energy at certain points of their rotation, and all other angles are at less than optimal efficiency. HAWT blades are harnessing at maximum efficiency no matter their rotation, so long as they're pointed into the wind. Hence, you have to compensate with more of them, which increases the ground footprint of the installation, the cost, and the noise.

How about wind farms built on man made lakes such that fish farming can take place? One could even open the bases of the windmills such that fish could use the submerged portion of the base as habitat. Servicing the windmills could be done by boat. Awnings with solar cells could shade much of the lake so that we can grow good food, gather wind and solar power all in the same space. Victory is as easy as we allow it to be!

Why VAWT's are less sensitive is the sad fact they can't capture much of the wind's energy. Thus one downwind would have of a VAWT would have wind with more energy than downwind of a HAWT.
The facts are VAWT's take 3-10x's the material with far more parts, failure points to get 1/3 of the energy the same area of a good 3blade HAWT would that costs only 10-30% of a similar output HAWT.
I've done VAWT's and found they are great as linear ones on sailboat/the sails. But for generating electrical power from the wind you need torque and speed to get power. VAWT's lack speed.
The sad thing is all these VAWT people know this too. An even worse it costs 75% less to do it right in a HAWT!!
Nor is this rocket science as they perfected small WT's in the 30's before subsidized utility power killed them off. Many of them are still running today and are prized power producers. Why can't they do that now cost effectively? They are really simple machines.

I have followed Amory Lovins since 1983. In the field of energy he is the top scientist/engineer. So if he advocates decentralized (distributed), I will bet on it. However, this is a very complicated subject. As technology changes, the best solution changes.
We can be sure of two things remaining constant: 1. Govt. interference never helps, and sometimes makes progress impossible. 2. No "energy problem" would exist in the first place if energy suppliers operated on a level playing field, i.e., in a free market.

I can't help but wonder if gobbling up wind energy will at some point begin to have climatic effects. I wonder the same about current/tidal turbines in bodies of water. Both will certainly have local effects. Just sayin'.

@Fritz, I agree with your sentiment. Even by tapping Solar power you are stopping a portion of the environment of absorbing the normal amount of heat. - It is just one of life's little general rules: there is no such thing as a free lunch.
When alternative energy gets going in a BIG way, then it will become more visible.
In whatever way we generate our energy currently we will be having some side-effect, but the burning of fossil fuels is probably the worst offender. Our challenge is to spread our generation of power such that it is having a minimal impact on world and its environment.

Why is Mike so eager to discredit new technology? Does he work for a wind turbine manufacturer? In the interests of full disclosure I would like to know. John is a dedicated researcher in search of better methods of energy extraction from the wind. His published results should have everyone in the wind industry buzzing. Imagine having the potential to extract 10 times more energy from a given area of land using his practices.
Mike says the National Renewable Energy Laboratory (NREL) points out in its land use guidelines, modern wind farms take up less than 1 percent to a maximum of 2 percent of the land that they are spread over. This may be of importance to the farmers that own the land, but it is of little concern to a wind farm developer who has to build roads and transmission lines to turbines spaced far apart. Subsequently, other wind farm developers must settle for secondary locations with lower wind, which only increases the Levelized Cost of Energy.
I think John is doing great work and I am anxiously awaiting the results from his current projects.