Bruno Cova Head of Power Systems, Markets and Regulatory

Assessing the maximum penetration of non-programmable RES generation in power systems with predominant thermal generation

Bruno CovaHead of Power Systems, Markets and RegulatoryDivision Consulting, Solutions & Services

Renewable Energy Seminar, Amman, 27th-28th March 2012

Source: AUE

Agenda

Trends towards a progressive decarbonisation of power systems

Increasing penetration of power generation from non-programmable RES

Problems to overcome to enhance generation from non-programmable RES

Possible solutions: Enhancing flexibility of the power system (generation / grid / demand) The role of transmission infrastructure (supergrids/electricity highways)

The CESI experience

2

Power generation in the world

Power Generation from main energy sources

Source: Enerdata Yearbook 2011 / CESI elaborationsWorld power production: ~21.240 TWh

40%

20%

7%

15%

16%2% COAL

GAS

OIL

NUCLEAR

HYDRO

RENEWABLE- Biomass- Solar- Wind- Geothermal

3

Power generation in the Arab Countries

Power Generation from main energy sources

Source: AUE statistical bulletin 2010 / CESI elaborations

Typical specific CO2 emissions (kg/MWh)95.9%

3.8%

0.2%

FOSSIL FUEL HYDRO RENEWABLE

750÷1000

750÷850

500÷700

350÷450

0

200

400

600

800

1000

1200

Coal Oil Gas OCGT Gas CCGTArab Countries power production: ~815 TWh

4

Trends towards a progressive decarbonisation of power systems: Europe

The EU 20-20-20 objectives to meet the goal of limiting the global surface warming to above pre-industrial level:

20% reduction of greenhouse gases (GHG) emissions in 2020 compared to 1990; 20% savings in energy consumption compared to baseline projections for 2020; 20% of overall energy mix from RES by the year 2020.

Long-term target (not binding yet) by 2050: decarbonisation up to 80-95% compared to 1990 level

Present trend of «carbon-free» generation in the EU power sector:

• 2010: 48%• 2020: 54% (2000 TWh)

5

China: announced in 2009 a target of CO2

emission reduction per unit of GDP between 40% and 45% compared to 2005 levels by 2020

US: Northeast’s Regional Greenhouse Gas Initiative (RGGI), the first cap-and-trade program in the United States (year 2009) to set mandatory CO2 limits for the power sector. RGGI caps power sector CO2 emissions at the 2009 levels and requires a 10% reduction by 2018

Trends towards a progressive decarbonisation of power systems: other regions

6

Trends towards a progressive decarbonisation of power systems: the Arab Countries

In the Arab Countries the share of RES power generation is limited to 4% out of which 3.8% from hydro (Egypt, Sudan, Iraq, Syria, Morocco)

…but Arab Countries are endowed with a huge potential of power generation from the sun and the wind

Source: TREC development group

Source: the Schott memorandum

From 1 sq km of desert one can obtain with CSP up to:

250 GWh/year of Electricity 60 Million m³/year of Desalted

Seawater

7


Which problems already

experienced in Europe ?

RES generating capacity in Europe [GW]

+46%

+149%

SolarWind

0

50

100

150

200

250

Hydro Wind SolarOthers

11478

2612

118194

38 32

2010

2020

8

Agenda





The CESI experience

9

Pag. 10

Additional reserve and balancing capability


Risk of overgeneration in low loading conditions

Voltage profile and reactive power management

Difficult transitions in the ramp up/down

hours

Network congestion

Critical behaviour of the system in dynamic conditions

Curtailed RES generation !!!

Pag. 11

Possible solutions

Maximisation of RES generation penetration while minimising the

risk of curtailment: a FOUR-LAYER TOP-DOWN APPROACH

1. Reserve Criterion

2. Network connection / Static analysis

3. Reliability analysis

4. Dynamic Analysis

Single Busbar model

Secondary and Tertiary reserves are sized to manage the frequency error and the largest generator tripping

Additional reserve to face the unpredictability of RES is estimated

Acceptable gradients of max power increase/decrease are taken into account to confirm the limit of non-dispatchable generation

RES energy feed points and network constraints are not considered yet

1. Reserve criterion – Part 1

Increase in reserve requirement

Source: IEA-Wind

12

Pag. 13

1. Reserve criterion – Part 2

Results

First evaluation of maximum RES penetration that can be accepted by the system

Secondaryincrease reserve

Tertiaryincreasereserve

Renewableproduction

Secondarydecrease reserve

Tertiarydecreasereserve

Additionalreserve forRESTraditional

generation

i iMINP

i iMAXP

Max{RES} = Demand - (∑i PMIN-i + Tertiary reserve + Additional reserve)

Pag. 14

2. Network connection / Static analysis

Load flow calculations in compliance with the N and N-1 security criteria (TSO rules)

The most significant load scenarios are considered (i.e. peak and low load conditions)

Check the congestions on transmission network Impact of wind production on the system’s voltage profile

Results

Distribution of RES energy production capacity

The best connection points of RES units on the network

Pag. 15

3. Reliability analysis – Part 1

Different scenarios of RES penetration are evaluated to highlight the effects of increased RES generation on the secure and reliable supply of electricity

Probabilistic analysis using Monte Carlo method and considering: The probabilistic nature of

generation-transmission system over a whole year of operation

The unavailability of all power system components

Possible optimal exploitation of hydro sources

A simplified or complete network model

9 657 130519532601324938974545519358416489713777858433

0

5,000

10,000

15,000

20,000

25,000Annual photovoltaic production [MW]

9 603 11971791238529793573416747615355594965437137773183250

1,000

2,000

3,000

4,000

5,000

6,000

7,000

8,000Annual wind production [MW]

Pag. 16

3. Reliability analysis – Part 2

Results Three meaningful “Risk Indices”:

• Loss Of Load Expectation• Loss Of Load Probability• Expected Energy Not Supplied

Reliability of the system to fulfil power demand

The maximum RES penetration compliant with reliability standards

0

5

10

15

20

25LOLE [h/year]

LOLP[%]

EENS[p.u.]

Scenario AScenario BBound

Wind /solar curtailment due to network element overloads, lack of interconnection or minimum stable operation of conventional units in low load condition

Possible network reinforcements, new storage devices and reserve margins able to preserve the static reliability and the security of the system

Pag. 17

4. Dynamic Analysis – Part 1

Check the fluctuations due to RES production intermittency (mainly frequency due to wind)

Pag. 18

4. Dynamic Analysis – Part 2

Analysis of network response, voltages and frequency to major fault events

Results

Measures to avoid any RES production restriction due to dynamic constraints

&ĂƵůƚZŝĚĞdŚƌŽƵŐŚĐŚĂƌĂĐƚĞƌŝƐƟĐ

Pag. 19

Possible solutions

Energy storageTwo levels: small scale to smooth high frequency

low amplitude intermittency: batteries at s/s

large scale for systemwide stabilisation: hydro pumping / different policies for unit commitment : higher rate of start up/ shut down of unit : OC TG

Demand responsiveness Demand response from users……. including electric vehicles

Source EC

The role of transmission infrastructure: the electricity highways

20

The role of transmission infrastructure: electricity highways between Europe and the MENA region

21

Agenda





The CESI experience

22

Pag. 23

CESI experience

PREVISIONNEL AN 2016

HVDC to Europe

Max penetration of RES in Tunisia Max wind generation penetration in

Jordan

Renewable Integration Development Programme – Ireland

Max wind generation penetration in Italy

End of Presentation

24


Need for additional reserve to cope with the intermittency of non-programmable RES generation

Solar (PV) generation is treated like wind production with additional reserve equal to the half of wind one

Penetration: wind / solar production [MW] / demand

Additional reserve [%]: percentage of wind / solar generation

Generated power

Secondary increase reserve

i iMINP

i iMAXP

Tertiary increase reserve

Additional increase reserve

Renewable production Wind + solar

Secondary decrese reserve

Tertiary decrease reserve

Additional decrease reserve Traditional

generation

Increase in reserve requirement

Source: IEA-Wind

25


Wind generation in Spain on 4th and 5th March 2008 (source REE)

Excessive RES generation over the instantaneous demand: risk of overgeneration

Possible voltage problems

26

Downward wind modulation

Pag. 27

Example of SpainRamp rate up to 10% of installed wind capacity per hour

Situation 9th Mai 2005


Coping with sharp variations of RES generation

Difficult transitions during load ramp up/down

demand

windExample of Spain


Difficult upward/downward transitions

No correlation between wind/sun generation and demand !!!

Time (min)

Wind + Solar

Load Request

Gradient of generation

28

Pag. 29


Network congestions caused by RES generation: Sun and wind are location dependent – often remote locations w.r.t. the demand

centres No correlation between demand and non-programmable RES generation location

- power flowing on longer patterns through the network with risk of creating “scattered” congestions also relatively far away from RES generation areas

Expected congestion in the 150 kV of the Italian peninsular regions due to WF (year 2009) – (source: CIGRE, CESI-Terna paper)

Pag. 30


Critical dynamic behavior of the system caused by Intermittency in RES generation causing a higher stress

on the conventional units to balance the system

Risk of cascading effect leading to the

system collapse

Frequency (Hz)

Typical solar radiation

0.00

100.00

200.00

300.00

400.00

500.00

600.00

700.00

800.00

900.00

1000.00

1 3 5 7 9 11 13 15 17 19 21 23

Hours

Rad

iati

on

(W

/m^

2)

Winter

Summer

Solar Radiation (W/m2)

Faults (e.g.: short circuits on a network component)

Pag. 31


Risks of RES generation curtailment depending on:

(In)flexibility of power plants (in)adequacy of the transmission /distribution infrastructures (including

cross-border lines) Possibility of energy storage Demand responsiveness

Different feasible penetration levels of non-

programmable RES generation

5%10%

16%22%

28%

0%

5%

10%

15%

20%

25%

30%

35%

40%

1,000 2,000 3,000 4,000 5,000 RE

S p

enet

rati

on

fo

r ea

ch a

rea

Cu

rtai

led

no

n-p

rog

r. R

ES

gen

.

Installed RES capacity [MW]

Bruno Cova Head of Power Systems, Markets and Regulatory

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