Interested to see the suggestion of using these as anchors for wind turbines, surely if they are hundreds of metres underwater it wouldn't make sense to use them as a form of foundation (anchor) for a turbine as it would need hundreds of meters of structure to get the turbine above the water line?
Storage of energy appears to be the biggest issue for renewables, especially wind based systems, but being able to store a 'few hours' doesn't deal with the extended periods needed for when the wind isn't blowing. I'm not sure about off-shore wind, my knowledge is based more on the variations on-shore but you can see the variations in UK wind produced energy here http://www.gridwatch.templar.co.uk/ which highlights the fluctuations we currently see.
I'm trying to be positive but there is still a long way to go to match the on-demand system that we have today. Maybe we should be looking at people using power when it is available and deal with the issues that creates...

@ Nigel Giddings - There are plenty of seaborne wind turbine designs that can float on the surface. Look up the FLIP research vessel to see equivalent technology or 'floating wind turbines'. Once in place, the turbines are tethered securely in place to the seabed. But your point about storage is absolutely correct. Once we solve this power storage problem, and make it portable, we will start to see the technologies we all dream of =).

A rather "heavy-weight" a solution ...
I still think the energy bags as proposed by Seamus Garvey (Nottingham University) are a cheap and elegant - thus lightweight - solution.
Admittedly you need some water depth, but at some places that's not a problem at all. Nice background article: http://www.theengineer.co.uk/in-depth/the-big-story/compressed-air-energy-storage-has-bags-of-potential/1008374.article

I wonder if they considered using a low-density object that could store buoyancy energy when pulled under the surface of the water. The density of concrete is ~2320 kg/m3 and the density of water is ~1000 kg/m3. So, for a 1 meter cube, the downward force, ignoring density changes for water at increased depths, is not much different than the upward force of a void at the same depth. Given that it's less resource intensive to build a void than it is to build a solid, I think they should consider something along those lines.

Looking at various reports and studies, we have a lot of information on the intermittent of wind power. Its pretty site specific, as some places are just more windy then others. In general for the united states it appears that wind turbines run at full power about 25-30% of the time. I didn't look deeper to see how much of that 75% was complete dead wind.
The thing is the spheres don't have to make up for that entire 75%. They will be needed only when demand is high and wind is low. Then you switch on the spheres, which have a known power period.
We already have backup systems in place, with gas turbines. Unfortunately since the power has to be ramped up at a moments notice we have to use open cycle turbines, which are far less efficient then the close cycle versions. Closed cycle can be brought up to 2/3rd power in about 1 hour. So if you have a few hours worth of sphere power online, it gives you time to start up your super efficient backup systems in an organized manner.
Also the system can be expanded as you go to allow for long and longer sphere cycles, using the backup generators less.

Interesting idea but unless it can be done at about the same cost as conventional anchors it's a very expensive option. Since internal pressures need to be the same for the air to displace the water anyway the storage can be a lightweight structure anchored to the seabed and doesn't even need to be at the turbine site. That would permit it to be situated in deeper water and thus have a higher energy density which means for the same storage capacity you can have a smaller less costly unit.

What a waste of time materials and effort. Alternative energy research will never be what it should be until government investments are driven into low cost low maintenance consumer based systems that individually feed back into a rebuilt grid. The wind is always blowing somewhere and the sun is always shining somewhere in the USA for at least 8 hours. 200 million home based units could power all of the USA and probably Canada and Mexico at the same time

There's lots of wild conjecture about intermittent supply, but this is a half-decent study: http://www.stanford.edu/group/efmh/jacobson/Articles/I/Offshore/offshore.html
It's no surprise that the straightforward solution to intermittency is scale, but most of the fossil fuel brigade try to make the case that if it's not windy in one place then it's not windy anywhere; this study shows that that assumption is wrong.

There are at least TWO existing alternative approaches to making these spheres or any similar really large underwater structure. First, electro-deposition can, and has been used to build large underwater structures. A steel wire and rebar structure defines a skeleton through with a current is run which causes mineral ions, ( calcium & magnesium mostly), in seawater to electro-deposit onto the wire form. These can be made arbitrarily large and thick at the intended depth, literally, deposited/built in place. Alternatively this could be an ideal use for a team of robots to place concrete on a form. The form could be the same kind vinyl sheet used for swimming pools only far larger and inflated with sea water to establish the desired shape. Think something on a scale of a blimp only filled with seawater. Concrete is continuously mixed and placed by many small bots centrally controlled so that the leading, or "wet" edge of concrete is always being added to with more concrete. The objective is wind up with a single monolithic seamless structure cast in place. Third, both of these approaches could be combined in each sphere to gain the best of both construction techniques. This would side step having to build and then cart around an object significantly the size of a cruise ship or oil rig. Remember how well that worked from the news about Carnival cruises many big dead buoy ships and also several oil companies such as the oil rig that broke free in the arctic. Jockeying stuff that large against ocean currents provably has NOT worked well.

I think that more emphasis should be placed upon improvement of the grid system so that power could be moved from one area to another without the need of too much storage. We have many alternative energy sources and more will be forthcoming such as with wave or current (Gulf of Mexico) energy conversion