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Experience with primary reserve supplied from energy storage system
Philip C. Kjaer, Vestas Wind Systems A/SATV: ”Energy storage – a must for successful conversion to green energy”
Monday 28th September 2015 – DTU, Lyngby, DK.
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Content
• Motivation
• Application & Installation
• Test Results
• Conclusions & Perspectives
Vestas’ research programme on energy storage started in 2010:
Motivation: Identify value-add from wind power + energy storage.
Activities:
• Identify best match of applications (revenue) and ESS technology.
• Develop competence on optimal control w.r.t. ES life-time and ratings.
• Select & qualify suppliers.
• Verify life-time models.
• Demonstrate integration, functionality and economy.
Wind Power Plant with Energy Storage
Energy
Storage
Management
System
4 x 3MW 1.6MW x 0.25h
Lem Kær substation & energy storage system
Forecast Error Reduction
Idea: Reduce financial penalties for not meeting generation commitment.
Reality: Aggregation of several wind plants over a geographical spread allows
similar gains.
Ramp Rate reduction / power smoothening (dP/dt control)
Idea: For power quality in weak networks, keep output variations from the
combined Wind/ESS plant below a threshold.
Reality: no payment for service; fast wear-out.
The most meaningful single number
expressing battery lifetime is the
allowed no. of charge/discharge
cycles of a given charge depth at a
certain temperature.
Modelling:
• Determine ESS ratings to warrant life-time for a given mission profile
• CAPEX (MW & MWh ratings + fixed cost)
• OPEX (efficiency + capacity degradation + standby + replacements + availability)
Cost: storage life-time
The potential services a Wind Power Plant augmented by embedded Energy Storage can provide
• Ancillary services
• Primary Reserves
• Secondary Reserves
• Tertiary Reserves
• Black Start
• Load Shifting – Energy Arbitrage
• Transmission Curtailment
• Forecast Error Reduction
• Ramp Rate reduction (dp/dt control)
• Voltage Control
• Islanding
• (Transmission deferral)
Results from a 2009 Vestas study on a 66MW wind plant in three different locations (electricity markets).
NPV (%) relative to best case (GFR)
Primary Reserve
Energy Storage installation
ESS1:
53’ container
0.4MW / 0.25h
LiFePO4
BMS
Air-con
Fire suppression
Heat exchanger
Power electronic converter
Transformer 0.48/10kV
10kV circuit breaker
ESS2:
Power electronic converter
Transformer 0.48/10kV
Heat exchangers
ESS2:
53’ container
1.2MW / 0.25h
Li4Ti5O12
BMS
Air-con
Fire suppression
Power System Stability
Source: NationalGrid, U.K.
Frequency support. Primary reserve.
The Danish TSO, Energinet.dk, defines the primary reserve product as:
• “Regulation must be supplied at a frequency deviation of up to +/- 200 mHz relative to the reference
frequency of 50 Hz. This will normally mean in the 49.8-50.2 Hz range. A deadband of +/- 20 mHz is
permitted. The reserve must as a minimum be supplied linearly and be fully activated within 30 seconds
in the event of a frequency deviation of +/- 200 mHz.”
• “……… be able to deliver a constant level of active power (dicharge) for 15 minutes. After another 15
minutes it should be able to repeat the delivery.”
- Auctions take place at 15h00 the day before delivery, and bids are supplied in 6 blocks of 4 hours each.
- Upwards and downwards regulation (under- and over-frequency, respectively) are separate, ie. asymmetrical bids are permitted.
- For an ESS “up-regulation-only” provider, currently no requirements exist to the level and direction of the power flow when not delivering upwards regulation.
Board of DirectorsBert Nordberg, ChairmanBorn: 23 March 1956
Nationality: Swedish
Resident: Sweden
Position: President & CEO, Sony Mobile
Communications (Sweden)
Carsten BjergBorn: 12 November 1959
Nationality: Danish
Resident: Denmark
Position: CEO and Group President of Grundfos
Management A/S (Denmark)
Eija PitkânenBorn: 23 April 1961
Nationality: Finnish
Resident: Finland
Position: Vice President, Head of Corporate
Responsibility, Telia Sonera (Sweden)
Håkan ErikssonBorn: 8 April 1961
Nationality: Swedish
Resident: Australia
Position: Head of Ericsson Australia, New Zealand
and Fiji (Australia)
Jørgen Huno RasmussenBorn: 25 June 1952
Nationality: Danish
Resident: Denmark
Position: President and CEO, FLSmidth & Co. A/S
(Denmark)
Jørn Ankær ThomsenBorn: 17 May 1945
Nationality: Danish
Resident: Denmark
Position: Attorney at Law and partner, Gorrissen
Federspiel (Denmark)
Kim Hvid Thomsen**Born: 8 August 1963
Nationality: Danish
Resident. Denmark
Position: Industry technician and Senior Shop
Steward, Vestas Manufacturing A/S (Denmark)
Kurt Anker NielsenBorn: 8 August 1945
Nationality: Danish
Resident: Denmark
Position: Director
Knud Bjarne Hansen*Born: 26 March 1952
Nationality: Danish
Resident. Denmark
Position: Senior Vice President, Vestas Wind
Systems A/S (Denmark)
Lars Josefsson, Deputy ChairmanBorn: 31 May 1953
Nationality: Swedish
Resident: Sweden
Position: Independent consultant
Michael Abildgaard Lisbjerg**Born: 17 September 1974
Nationality: Danish
Resident: Denmark
Position: Skilled worker - Production & Shop
Steward, Vestas Manufacturing A/S (Denmark)
Sussie Dvinge Agerbo*Born: 5 November 1970
Nationality: Danish
Resident: Denmark
Position: Management Assistant, Vestas Wind
Systems A/S (Denmark)
*) Elected by company employees
**) Elected by Group employees
Test results
Danish TSO Primary Reserve approval test
0
200
400
600
800
1000
1200
-2000
-1500
-1000
-500
0
500
1000
1500
2000
2700 2900 3100 3300 3500 3700 3900 4100 4300 4500 4700
So
C [
0/0
0]
Po
we
r [k
W]
Time [sec]
15 minute activation
P_Elspec_ESS1+ESS2+AUX
SOC 1
SOC 2
Po
we
r [k
W]
Sta
te o
f C
ha
rge
>85% round-trip efficiency
Charge
SoC1 [%]
SoC2 [%]
Discharge
15 min 30 min0 min
90% SoC
10% SoC
1.4MW
-1.6MW
Frequency recordings
49.8 49.85 49.9 49.95 50 50.05 50.1 50.150
1
2
3
4
5
6
7x 10
6 No samples vs. frequency (1 sec update)N
um
ber
of
sam
ple
s
Frequency
Jan 1st 2013 – May 31st 2015
‘Up-regulation’ 49.98 Hz
“Our recordings have shown that continuous periods of 15 minutes of under-frequency (below 49.98 Hz) only occur in average 50 times per month (ie. <2%).”
Charging controller
Data recorded at site
0 1 2 3 4 5 6 7 8-100
-50
0
50
100
Fre
quency d
ev.
[mH
z]
Primary Reserve from Energy Storage. 25th March 2013
0 1 2 3 4 5 6 7 8-1
-0.5
0
0.5
ES
pow
er
[MW
]
0 1 2 3 4 5 6 7 80.75
0.8
0.85
0.9
0.95
Sta
te o
f charg
e
Time [h]
15-min limit reached
Data recorded at site
49.85->49.8649.87->49.88
49.89->49.949.91->49.92
49.93->49.9449.95->49.96
49.97->49.98
12
34
56
78
910
1112
0
20
40
60
80
100
Frequency [Hz]
Accum. duration of low frequency periods pr. month
Month
Dura
tion [
hours
]
49.85->49.8649.87->49.88
49.89->49.949.91->49.92
49.93->49.9449.95->49.96
49.97->49.98
23
45
67
8910
1112
0
1
2
3
4
Frequency [Hz]
Calculated energy [MWh] vs. frequency pr. month
Month
Energ
y [
MW
h]
Discharged during upward regulation 0.32 MWh/day
Charged 0.60 MWh/day
Absorbed for auxiliary power consumption 0.35 MWh/day
Duration of frequency below 49.98Hz 16%
Under-frequency energy demand 0.35 MWh/day
Recordings from 2013-2014
Primary reserve tariff evolution in Western Denmark
0 100 200 300 400 500 600 700 800 9000
20
40
60
80
100
120
140
Days
Tariff
[E
UR
/MW
h]
Tariff for ENDK1 primary reserve up-regulation
Jan 1st 2013 May 31st 2015
Net present value of green field investment
-1
-0,8
-0,6
-0,4
-0,2
0
0,2
0 2 4 6 8 10 12 14 16 18 20
NPV, per-unit vs years
2013
2014
0 100 200 300 400 500 600 700 800 9000
20
40
60
80
100
120
140
Days
Tariff
[E
UR
/MW
h]
Tariff for ENDK1 primary reserve up-regulation
Simulation power/energy ratio for primary reserve
ESS Capacity
(discharge time with
ESS full power )
PFRAVA
[%]
15 min discharge time 100,00
10 min discharge time 100,00
7.5 min discharge time 100,00
6 min discharge time 100,00
5 min discharge time 99.94
4 min discharge time 99.82
3 min discharge time 99.06
2 min discharge time 95.70
1 min discharge time 84.63
0.5 min discharge time 72.26
0.1min discharge time 48.39-2 0 2 4 6 8 10 12 14 16 18 20
30
40
50
60
70
80
90
100
110
120
ESS capacity [min]
PF
R s
erv
ice
av
aila
bili
ty [
%]
Simulations are based on 1 year grid frequency data (2012).
Wind power plant + energy storage applications
Down-regulation by wind power plant
Up-regulation by
energy storage system
Inertial Response + Primary Reserve
10600
10800
11000
11200
11400
11600
11800
12000
12200
0 500 1000 1500 2000 2500 3000 3500
Pref_AWPP_kW
P_Elspec_WPP_kW
P_Elspec_WPP_kW
Power smoothening
Power oscillation damping
From 2012-13: www.ewea.org + www.twenties-project.eu
Conclusions and Perspectives
1. The TSO has approved storage units for primary reserve market participation.
2. Apparently the only installation of its kind in Scandinavia. Commercial operation for 3 years.
3. The 15-minute constant power discharge effectively sizes the capacity. Only used for up-regulation.
4. The observed network frequency excursions are very modest � Low utilisation of storage (2%).
5. Effective full-cycle efficiency is 50% (30% incl. aux power losses).
6. Specific algorithm developed and approved for control of storage charging.
7. If symmetric bids are required, SoC controller must be adapted (and business case erodes).
8. Recent reserve power tariff reduction erodes business case.
9. Storage cost reduction required and expected.
10. Installed storage capacity may be reduced if requirements were matched to actual frequency excursions.
This would increase utilisation rate. Main circuit efficiency should then be optimised.
11. Blending other ancillary services may increase earnings.
Thanks to:
Thank you for your attention.
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