IEEE Power & Energy Magazine - November/December 2019 - 27

Curtailment may be enacted for various reasons, including
transmission congestion, provision of down-regulation reserves,
and system balancing during oversupply periods.

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Generation (MW)

A se cond PV storage pla nt , 20 M W PVs wit h a
96 MW (nameplate) of PVs at the end of 2018. This is significant for an island with a midday demand of 55-65 MW. 20-MW/100-MWh battery system, was completed in
How did KIUC transform a resource mix that was 92% oil December 2018. Annual energy demand served by PVs is
expected to jump to 38% for 2019 due to this new plant.
based in 2010 into today's system?
As PV capacity increased, KIUC reduced minimum gen- That will increase further with a 14-MW PV 70-MWh storeration levels on its thermal generators from 50 to 25% and age plant scheduled for commissioning at the end of 2019.
Commercial operation of the second PV storage plant has
then later to 10%. This provided more flexibility for integrating midday PV output and enhanced the ability of thermal enabled KIUC to run at 100% renewable energy penetration
generator spinning reserves to manage the effects of sudden at times. For example, on 24 February 2019, KIUC ran the
cloud cover and the late afternoon ramp toward the evening grid for 25 min using 100% renewables with zero fossil-fuel
peak demand. However, continued PV growth exhausted this consumption (Figure 3). The mix for that period was 80% PV
flexibility, and KIUC realized that storage or load-shifting (some of which was backed with storage), 10% hydroelectric,
would be needed to accommodate future VER installations. and 10% biomass. The key to this achievement is the ability
This led to the first PV storage power purchase agreement of KIUC to operate its Kapaia GE LM2500 unit as a synbetween KIUC and SolarCity (now Tesla) for a combined chronous condenser. Operating the gas turbine in synchro13-MW PV and 13-MW/52-MWh battery, which was com- nous-condenser mode maintains significant inertia, voltage
support, and fault current contributions that ensure system
missioned in May 2017.
KIUC's daily peak demand occurs about one hour after sunset. security. KIUC is now working to extend these 100% renewTo balance the high solar penetration levels, KIUC uses thermal ables periods to 2-4 h, which will be enabled by the third PV
generators, dedicated battery energy storage systems, PV storage storage plant.
plants, and control algorithms developed in-house. KIUC typically holds
contingency reserves equivalent to
80
50% of the real-time output from PV
plants not backed by storage. Online
Average of Hydro
Average of Bio
70
fossil generation is increasingly
Average of Oil
Average of Solar
being replaced by battery storage for
60
the provision of spinning reserves.
KIUC has ample quick-start units.
50
However, if they are not already
online, they cannot start fast enough
40
to respond to cloud events. A typical
30
midday dispatch for very sunny days
in 2018 was 7 MW hydroelectric,
20
7 MW biomass, 1 MW oil, and the
rest (40-50 MW) from PVs, includ10
ing the PV storage plant. The results
speak for themselves. In 2018, 27% of
0
KIUC's annual energy demand was
served by utility-scale and distributed
PVs, with curtailment of potential
PV production lower than 0.6%. On
average, in 2018, PVs served 54% of
Time
demand at noon, but on an instantaneous basis, KIUC has reached as figure 3. The dispatch of the KIUC system on 24 February 2019 with 100% renewhigh as 85% PV penetration.
ables operation. Yellow: PV (Solar); gray: oil; green: biomass (Bio); blue: hydroelectric.
november/december 2019

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IEEE Power & Energy Magazine - November/December 2019

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