8
On this assumption CLP conducted a feasibility study
on "Dual-firing", and from their evaluation concluded that even with higher capital costs (approx. 26%) there was
merit in future fossil-fired plant being dual-fired.
Accordingly this paper assumes that future expansion will
be dual-fired, although CLP have not yet made a final
· decision.
(f) Forecast
•
Having established the desired technical specifications
for future expansion the final phase of the plan requires
that appropriate consideration be given to the economic
aspects of expansion.
The economic advantages of a large unit are:
(i) cheaper capital cost per kw installed;
(ii) lower operation and maintenance cost due to
the lower manning level per kw installed.
However, a big unit requires a large complementary
spinning reserve to cater for its sudden loss to the overall
system, thus increasing the need for:"
(i) reserve capacity; and
(ii)
the running of inefficient generating sets.
In order to determine the optimum extent of future
generating capacity it is necessary to examine these factors
in detail and accordingly a number of different expansion
patterns were devised and analysed.
For each expansion pattern, a full simulation of system
operation was carried out in order to calculate the yearly
fuel expenses and operation and maintenance costs. These
costs were combined with the capital expenditure required
for the expansion, to form a complete cash flow picture. The
cash flows were then discounted to the year 1976, at an interest rate of 10% p.a., giving the total present cost of
the expansion patterns.
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