Environmental Engineering Reference
In-Depth Information
with ships nearly as small (Santa Maria, 165 t), Great
Armada (1588) vessels averaged 515 t, and typical late
eighteenth-century ships of the India fleet rated 1200 t.
But speeds have roughly quadrupled. Roman cargo ships
usually sailed at 2-2.5 m/s, whereas in 1853, the
Boston-built and British-crewed Lightning logged
the longest daily run, 803 km at an average speed of 9.3
m/s (Wood 1922). And in 1890, Cutty Sark (a famous
tea clipper), ran 6000 km in 13 consecutive days, averag-
ing 5.3 m/s (Armstrong 1969).
R. Unger (1984) tried to quantify the contributions of
sailing ships by making a set of assumptions to calculate
their energy use during the Dutch Golden Age at about
200 TJ (6.2 MW) a year, roughly equal to the total en-
ergy output from all Dutch windmills, as estimated by
DeZeeuw (1978), but only a small fraction (less than
5%) of the country's huge peat consumption. But such
comparisons mean little. On the one hand, no amount
of peat would have made the seaborne trips to the East
Indies possible; on the other, the useful energy gained
from the peat was almost certainly less than one-quarter
of its gross heat value. Moreover, it is questionable to
compare a limited and rapidly depleting store of fossil en-
ergy with an abundant and renewable resource.
