Interesting... I just happened to think of these two relevant recent article, where two basins in California have subsided up to 60mm, and parts of Jakarta falling by 2.5m (!) in 10 years, both from ground water removal...
I suspect you were using a pipe equation, not an aircraft drag coefficient equation - I hope. That would be more applicable to a flow through a small tube. In pipe head loss equations, f is the friction coefficient, and L is the Length. At least a pipe head loss equation might have something to...
It might be worth looking at electric cement mixers, which do a very similar job. They have them at Home Depot and Lowes. You might even be able to buy a drive system as a spare from one of them. The home versions appear to be fairly low-cost gear drive systems...
The energy required to mine, transport, and manufacture the cell phones sold each year will be quite large. The base stations also consume far more power than phones themselves, and also require energy to manufacture, including many rare materials.
On older 2G systems, the base stations I...
For grid level storage, there is a gravity system that has been tested:
http://www.aresnorthamerica.com/
http://www.scientificamerican.com/article/energy-storage-hits-the-rails-out-west/
It doesn't scale down that well, unless you live on a mountainside.
There are also grid level compressed...