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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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