Safer is Smarter - Kauai Island Utility Cooperative

14 KIUC CURRENTS
Figure 2 – Demand profile from December 27, 2007.
As we learned previously, Kaua‘i’s demand
does not come close to approaching 117,000 kW,
so why do we have seemingly so much generation?
The simple answer is we must have enough
generating units to meet demand, while juggling
required maintenance and unexpected equipment
problems. The fact KIUC is an isolated, islanded
system not tied to another system that we can buy
power from when we are short on capacity means
we must maintain significant reserve capacity
compared to systems on the mainland, which are
for the most part connected to each other.
Overhead view of GT2 accessories and turbine.
One way of determining how much reserve
capacity we have to maintain is through our
Adequacy of Supply (AOS) measure. As a
regulated utility, KIUC annually evaluates its AOS
and files it with the Hawai‘i Public Utilities
Commission. The AOS criteria state that KIUC
must be able to (1) meet Kaua‘i’s evening, or
highest, peak demand with the largest unit out of
service, and (2) meet the morning peak demand
with the largest unit out of service and the third
largest unit scheduled out for maintenance.
We learned that our highest peak was 77,750
kW. As Figure 3 shows, Kapaia Power Station CT1
is the largest unit, with a net output of 26,600 kW.
That means we must maintain 104,350 kW to
meet AOS criteria one. AOS criteria two requires
additional pieces of information: the morning
peak demand and the size of our third­largest
unit. Morning peak demands during the last year
have been in the 65,000 to 70,000 kW range.
Figure 3 shows the third­largest unit is Port Allen
GT1, with a net output of 17,500 kW. That means
we must maintain 114,100 kW to meet AOS
criteria two.
As you can see, performing maintenance on our
larger units creates a challenging situation when
trying to ensure sufficient units are available to
meet all possible demand scenarios. Thankfully,
our second­ and third­largest units (Port Allen GT2
and GT1, respectively) are not dispatched often
and, therefore, do not require much maintenance,
so it is rare they are unavailable.