PRACTICAL CONSIDERATION
The current commercial systems of PCP, as used in Japan, have
demonstrated their high reliability—over 98% of availability when
needed. The system is highly automated, and the operation cost
is low. In spite of that, the system has not been widely used even
in Japan due to the following reasons.
The current PCP systems have very low linefill rate (3%). This
means only 3% of the pipe length is occupied by capsules; 97%
is empty. As a result of this low linefill rate, large diameter pipe is
required to transport relatively small quantity of cargo—the
throughput is low! Note that unit freight transportation cost in $/
ton is directly proportional to the total system cost and inversely
proportional to the linefill rate or throughput. Therefore, a fivefold
increase in linefill from 3% to 15% would cut the unit cost
by half even if the total system cost is increased 2.5 times due to
increased throughput—more capsules, more handling facility, and
higher operation costs.