IEEE Power & Energy Magazine - January/February 2017 - 68

challenges and bottlenecks emerging from several types of
interactions; such studies would likely have shown where
greater regulatory flexibility could have alleviated, if not
entirely avoided, the dire consequences.
Fast-forward 15 years, and California is preparing for
another such energy-system challenge, with scientific-technical discussions of system integration currently ongoing to
ensure that the necessary actions, preparations, and precautions
are taken on the technological side; the economic, financial, and
market environment; and an appropriate regulatory framework.
With the rapid growth of PV solar capacity and given no corrective flexibility measures, it can be expected that, around 2020,
stiff ramping rates by the non-PV remainder of the generation
system-of the order of 13 GW in
3 h-will have to be coped with.
This is illustrated by the so-called
Net Load-31 March
28,000
"duck curve" published by the Cali26,000
fornia independent system operator
CAISO, as shown in Figure 8.
24,000
In reaction to this duck curve,
22,000
studies have been initiated to
20,000
2012 (Actual)
demonstrate that appropriate flex2013 (Actual)
18,000
ibility measures, dealing with
Increased
2014
Potential
16,000
both the total demand and the net
2015
Ramp
Overgeneration
2016
or residual demand, can "teach
14,000
2017
2018
the duck to fly"-basically show2019
12,000
2020
ing that stiff ramping rates can be
10,000
avoided (see Figure 9). Whether
the measures currently suggested
0
will actually work remains to be
12 a.m. 3 a.m. 6 a.m. 9 a.m. 12 p.m. 3 p.m. 6 p.m. 9 p.m.
Hour
seen, but the fact that the discussion has started is encouraging; by
the time needed, appropriate soft
figure 8. The duck curve illustrating the "net" or "residual" load to be covered
by the non-PVs remainder of the electricity system in California. After the sun has
solutions may be implemented.
Megawatts

cap on the retail price of electricity, while gas prices-and,
thus, wholesale electricity prices-began to rise; increasing electricity demand; reduced imports of electricity from
other states; a slowdown in the pace of granting permits to
build new electric power plants, as a result of environmental
regulations; and market-power problems, including market
manipulation and even fraud. This crisis cost the California
economy (consumers, shareholders, taxpayers, and laid-off
employees, among others) several tens of billions of dollars and led to the drastic scaling back the energy-market
liberalization philosophy in the state. Policy and regulation
were major factors in the development of this crisis. In this
case, system studies would certainly have pointed to the

set in the early evening, electricity demand increases for air-conditioning, lighting, and cooking needs, leading to big ramping rates to meet electricity demand.
(Source: CAISO.)

Duck Curve with All Ten Strategies Compared to Original Load
4,000
3,500
3,000
MW

2,500
2,000
1,500
1,000
500
0

Post Strategies Total Load
Post Strategies Net Load
Original Net Load
1 2 3 4 5 6 7 8 9 1011 12 13 1415 16 17 18 19 2021 22 23 24
Hours

figure 9. Avoiding stiff ramping rates shown in Figure 8 (dotted curve) can be accomplished by well-chosen strategies to level off the net load (green curve). (Source:
J. Lazar, Teaching the "Duck" to Fly, RAP, 2016.)
68

ieee power & energy magazine

Energy-System-Integration
Challenges in China

China also faces considerable
challenges in terms of energysystem inflexibility, especially
for the integration of renewable
energy. Renewable energy is
growing in a nonmarket environment, where wind and solar generation is at the top of the merit
order. However, large amounts of
renewable energy are still being
curtailed or dumped, despite
the fact that it is scheduled with
first priority. This is because it is
obligatory for conventional generating units to offer flexibility
(by reducing their output) but
without any financial compensation. Because the flexibility is not
january/february 2017

Table of Contents for the Digital Edition of IEEE Power & Energy Magazine - January/February 2017