Safer is Smarter - Kauai Island Utility Cooperative

Photos by Shelley Paik
KIUC’s electrical system has relatively low
industrial customer loading. The highest peaks
tend to be set by a combination of high tourism
and cloudy, light wind days, which cause loss of
solar output for water heating and photovoltaic
energy, while driving higher air conditioning use.
Lately, daily peak demand has been between
65,000 and 72,000 kilowatts (kW) due to mild
conditions in both the local climate and economy.
A recent day’s demand profile is shown in
Figure 1, with kW demand along the vertical y­axis
and time of day along the horizontal x­axis.
The last two highest all­time peaks were set
during the week between Christmas and New
Year’s Day, 2004 and 2007. The December 27,
2007, peak, shown in Figure 2, remains Kaua‘i’s
all­time highest peak demand, at 77,750 kW.
Theoretically, the entire load that resulted in
the all­time high peak is still connected to the
system—and perhaps even more has been
connected—so KIUC could be required to serve
that same demand, or more, once economic
conditions improve.
We know what causes the highest peak during a
given year. If you look at the demand profiles in
Figures 2 and 3, you will notice some similarities.
When does daily peak occur? Unlike the
mainland, which typically experiences its peak
demand in the afternoon, Kaua‘i’s peak occurs
within an hour after sunset.
Think about it: What are you doing at that
time? It is getting dark, and most people are
heading inside, turning on lights, cooking dinner,
bathing and watching TV. All the streetlights come
on. The demand solar systems have been handling
throughout the day is now placed back on
conventional generators, with most of the burden
being met by Port Allen. To ensure that burden is
met, every day the Port Allen crew attempts to
maintain the balance of forecasted demand and
required maintenance.
Supply
KIUC maintains a mix of conventional and
hydroelectric generating units that have various
pros and cons. Some units are very old, and some
are new. Some are more efficient, and some less.
Some are large, and some are small. Figure 3 lists
each of the units and shows that KIUC has
a total net generating capacity of about
117,000 kW, which is enough to power roughly
117,000 homes.
Figure 1 – Demand profile from August 19, 2010.
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