Environmental Engineering Reference
In-Depth Information
While the potential seems appreciable for tapping wave energy in coastal regions,
the much larger potential power at the open sea seems in practice unavailable, by
virtue of its remoteness.
On the other hand, one might conceive of ocean stations, large
floating facilities,
which need not be close to land. Such stations might be used, for example, as a basis
for desalinization of seawater, for extraction of deuterium from the sea, or for
electrolytic hydrogen generation. Possible ocean stations for hydrogen production
could also harvest wind and solar power. Schemes for delivery by tanker, analogous to
the shipping of oil and liquid natural gas, might evolve.
An ocean station seems more practical than a space station for the human
future, let alone facilities discussed (in the United States) for colonization of the
moon. We will return in Chapter 5 to an estimate of the cost of a satellite system to
send solar energy to earth from space.
An economically sound and competent city might launch its own ocean station, to
capture energy for its sphere of influence, and thus reduce dependence on its
surrounding grid. This scenario might extend to viable coastal cities worldwide,
perhaps Dhaka or Mumbai, beyond New York City.
1.1.3
Earth-Based Long-Term Energy Resources
Some of the long-term energy that is available is stored in the earth, or is the result of
the orbital motion of the moon around the earth. In addition, the composition of the
ocean contains enough deuterium, present from the beginning of the earth, to
constitute a long-term resource.
1.1.3.1 Lunar Ocean Tidal Motion
Tides are caused by the motion of the moon around the earth, in large part. In
funnel locations like the Bay of Fundy, the
flows can be large and rapid. Harvesting
tidal
flows can be similar to harvesting the
flow energy of a river. In some cases, all of
the
flow can be funneled into a single set of turbines, a situation more like that at
Niagara Falls. This is suggested by the arti
cial tidepool shown here in Figure 1.12.
Famous optimum locations, such as the Bay of Fundy, which has a tidal range of
17m, are at least partly exploited. At present, the 20MWtidal power plant at the Bay of
Fundy is the only such plant in operation. However, there is scope for more energy to
be tapped in this category.
An example of amuch larger potential is shown in Figure 1.13, based on tidal
ows
in the British Isles. In the analogy to the tidal basin, the North Sea roughly plays that
role in the example of the British Isles as the gateway between the Atlantic and the
North Sea. The energy
flow can be taxed on the intake and the exhaust of the cycle.
Calculations of the available power, up to 190 GW, are indicated on the diagram.
On smaller scales, the common occurrence of sandbars parallel to a beach suggests
many locations that could be utilized. In the Atlantic coast of the United States, the
Outer Banks of North Carolina enclose Pamlico Sound, an area about 2000 square
miles, or 5.18
10
9
m
2
. The tidal excursion at Cape Hatteras, on the ocean side, is
