Assessment of Large Scale Penetration of Variable Renewables
in Japan Considering Suppression of Power Fluctuation
Hiroto Shiraki
National Institute for Environmental Studies (NIES), JapanIntroduction
GHG emission reduction, Energy security, Uncertain nuclear policy

Generation cost, Long-term/Short-term power fluctuation

Demand →↑ Wind output

Generation & Demand
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Issue of renewables

Generation & Demand
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Increase of interests in renewables

How to fill the gap?

Demand →— Backup by fire power plants → CO2 emission— Introduce battery→ Increase of cost
— Parallel off of renewables → Decrease of benefit← PV output

Objectives: To estimate generation mix & costs under various penetration rate of renewable energy
To estimate suppression of power fluctuation under various penetration rate of renewable energy

MethodConstr. Balancing short-term fluctuation

Multi-regional generation planning model
Type: Bottom-up technology selection model
Objective function: minimize total system cost
Region: 10 region w/ interregional transmission line
Year: 2030
Demand pattern: 19 representative days, 1 hour stepCountermeasures against power fluctuation:— Load frequency control (LFC)— Parallel off— Battery for long –term fluctuation (SBST)— Battery for short-term fluctuation (SBLT)LFC_𝑆r,d,h ≥ LFC_𝐷r,d,h

LFC demand
LFC supply perType of generation
Abbrev.
generation Shot-term fluctuation
Coal boilerCOL
5%Coal IGCC
IGCC
5%Oil boiler
OIL
5%Open-cycle gas turbine
OCGT
10%
Combined-cycle gas turbine
CCGT
10%Pumped hydroPHY20% (20%)
Solar photovoltaic
PV10% per generation
Wind power w/o battery
WT
15% per capacity
Wind power w/ SBST(50% suppression) WT w/SBST1 7.5% per capacity
Wind power w/ SBST(100% suppression) WT w/SBST2 0% per capacity
Battery for long-term fluctuation
SBLT
20% (20%)-Electricity demand: 1005TWh, Nuclear: max 344TWh, Energy price: Reference case in WEO2009
45 emission case: NO emission target, +60% to -80% of emission in 1990 (5% step), -80% to -95% of emission in 1990 (1% step)

Generation mix & cost

1000

No emission target case: 484Mt-CO2 (+67% of 1990)
Main energy sources would change : COL → CCGT → WT&PV w/ SB
40% of electricity come from variable renewables in -90% emission case.
WT w/ SBST2 (100% suppression of short-term fluctuation) will drasticallyintroduced in the case stronger than -70% emission target.
• Generation cost in 90% emission reduction case → 1.7 times higher than that inNO emission target case.

800600400200Generation [TWh]300

I250IIIII

IV V

2001501005000%SBLT

10%
20%
30%
40%Penetration rate of WT & PV
WTWTw/SBST1WTw/SBST2

SBST capacity [GW]

For analysis… distinguished penetration stage
Stage I : WT w/o SBStage II : WT w/ SBST1 & PV
↓ Long-term fluctuation increased
Stage III : Stage II + SBLT
↓ PV saturation
Stage IV : WT w/ SBST2
50% ↓ LFC supply from GTCC reduced
Stage V: WT w/ SBST2
PV1009080706050403020100Stage IStage IIStage IIIStage IVStage V

Generation loss
by parallel off [TWh]2015PVWT
PVWT

Rate of generation loss→

105↓ Generation loss

NO55%
45%
35%
25%
15%
5%-5%
-15%-25%-35%-45%-55%-65%-75%
-85%
-95%

08%
7%
6%
5%
4%
3%
2%
1%
0%

Rate of generation loss

020

y = 0.92 x - 48.78
R² = 0.98

y = 0.57 x - 20.57
R² = 0.95

406080
WT capacity [GW]

100-95%

-85%

-75%

-65%

-55%

-45%-35%

-25%

-15%

-5%

5%

15%

25%

35%

CO2 emission caseTrans. loss
SBLT-charge
PHY-pump
PV
WTw/SBST2
WTw/SBST1
WT
SBLT
PHY
OIL
OCGT
CCGTw/CCS
CCGT
IGCCw/CCS
COL
HYD
NUC
DemandInstalled capacity of battery

y = 5.13 x - 494.58
R² = 0.92

y = 0.32 x - 7.02
R² = 0.98

45%

-200

55%

0NO

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Generation [TWh]Results : impact of power fluctuation

1200120• Regression analysis with simulation results• Required capacity of SBST per 1GW penetration ofWT was estimated• Short-term fluctuation could be balanced without
SBST if WT capacity was less than 20GW
• 5GW of SBST would be necessary for 1GW ofadditional WT in stage V because LFC supply from fire
power plants was restricted.

Parallel off of renewables• NO to +30% case: WT w/o SB was increased → Parallel off would increase• +30% to -15% case: WT w/o SB was substituted by WT w/ SBST1 → Parallel off would decrease• -15% to -70% case: WT w/ SB ST1 was increased → Parallel off would increase In -65% case, more than 7% of electricity generation was lost.

• -70% to- 95% case: WT w/ SBST2 was increased → Parallel off would decrease• Parallel off of PV was increased in the case stronger than -90% emission target

CO2 emission case

Summary & next step••••

Generation mix : 40% of electricity would be supplied by variable renewables in 90% emission reduction case.
Generation cost: in 90% emission reduction case → 1.7 times higher than that in NO emission target case.
Suppression of power fluctuation: Capacity of battery & parallel off would increase drastically if LFC from fire plants were restricted
Impact assessment of daily load curve change and geographical smoothing effect would be next research step
References 1) H. Shiraki, S. Ashina, Y. Kameyama, Y. Moriguchi, S. Hashimoto; Energy and Resources, 33-1, (2012), 1-10. (in Japanese) 2) S. Ashina, J. Fujino; (2008) Energy and Resources, 29-1, (2008), 1-7. (in Japanese)
The research works have been conducted with Dr. Ashina, Prof. Kameyama, Prof. Tasaki, Prof. Matsuhashi, and Prof. Moriguchi.