3.3.2. Reservoir
In the traditional PHS for thermal power plants or nuclear
plants, two reservoirs are required to be located on the upper
mountain and the lower valley. With the technology development,
seawater can now also be used for pumped storage purposes, particularly
in some remote islands where there might not be enough
fresh water. Besides, remote islands are surrounded by sea, and
thus often geography and geology are suitable for seawater
pumped storage. The feasibility of using seawater for PHS was first
examined by Japan [54], and a pilot seawater pumped storage
plant was constructed at Okinawa, with a roundtrip efficiency of
77% [55,56].
Based on the geography and condition of this island in this project,
a seawater pumped storage is also proposed. Therefore one
upper reservoir is only needed. The sizing procedures are given
as below.
The efficiency of the micro turbine, generator and pipe line
could be estimated as 80%, 80% and 95% according to the
engineering practice and manufacturers’ specifications. Thus
the overall efficiency of turbine mode is determined as
gt = 80% 80% 95% = 60.8.
The water stored in upper reservoir should be adequate to meet
the power consumption in this island for the several days of required
autonomy. The potential energy released from the upper
pond can be derived as: