Temperature differences (driven mostly by tilt of earth's axis)
Prevailing wind patterns interacting with the surface waters
(again driven mostly by tilt of earth's axis)
the rotation of the earth the Coriolis Force
shorelines of continental masses
The largest single current in the World is the Gulf Stream Current:
Tapping the Current for Energy:
Gulf current has 1000 times the flow of the Mississippi
River(!)
It is 80-150 km wide and 800-1200 m deep.
Current averages about 3 mph (but velocity varies a lot with depth - fastest
velocities are at the surface)
Density of water is higher as well
Its always there - no intermittency problem
no need for energy
storage
Build Turbines for underwater use
Anchor a foundation to the ocean floor
hundreds of miles long rigged with turbines
cables on ocean floor to shore deliver the electricity
Some Specifics to estimate total yield:
Ocean currents have approximately 830 times the energy density
of moving air (i.e. wind).
For a 2 m/sec current, the equivalent power density is 4 KW per
square meter. (recall that a 10 m/sec wind produces 600 watts per square
meter - now even though the density is 830 times larger, the power per
unit area goes as the velocity3 so the net gain is only
a factor of 6.5)
Assume underwater array of 3 blade turbines with blade length of
2 meters. That means 50KW unit capacity but in principle the spacing
between the turbines is small so can pack them tightly together.
So we build a 1 km leg with turbines space by 4 meters. Each leg
then has 250 units x 50 kw = 12.5 MW per km.
Now lets build parallel legs over a 10 km wide section in the middle
which each leg seperated by say 100 meters. So that's 100 legs in total.
Which means we have nameplated 1.25 GW if of power in just a 1 x 10 km
cross section of the gulf current.
Now repeat this over 100 km of Gulf stream and you have 125 GW. Repeat
this over 1000 km and you have 1.26 TW (or equivalent of US Total nameplate
capacity) Gee, Isn't this a solution?
Caveats:
An engineering challenge but there are few bad side effects
from producing energy this way
Obviously the capital costs are huge in this case but this
does represent a Large Scale Solution as the Gulf current is easily
4000 km in length.
A sensible, large scale local example that would provide florida with 35% of its
electrical needs 24x7.
Deployment is very much like that of a wind farm in terms of Unit capacity.
the Coriolis Force
