Impacts of large amounts of wind power on design and operation of power systems, results of IEA collaboration

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Impacts of large amounts of windpower on design
and operation of power systems, results of IEA
collaboration
Holttinen H, Meibom P, Orths A, Lange, B,
OMalley M, Pierik, J, Tande J O, Estanqueiro A,
Gomez E, Söder L, Strbac G, Smith J C, van Hulle,
FHannele Holttinen,Operating Agent, IEA WIND
Task 25
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IEA WIND Task 25OBJECTIVEto analyse and
further develop the methodology to assess the
impact of wind on power systems

• First phase 2006-08, 11 countries EWEA
  participate
• Second phase 2009-11, 12 countries EWEA
  participate.
• GOALS
• Provide an international forum for exchange of
  knowledge
• State-of-the-art review and analyse the studies
  and results so far
• methodologies and input data, system operation
  practices
• State-of-the-art report published in 2007, final
  report expected Apr-09
• Formulate guidelines
• recommended methodologies and input data when
  estimating impacts and costs of wind power
  integration
• Quantify the impacts of wind power on power
  systems
• range of impacts/costs rules of thumb
• www.ieawind.org/AnnexXXV

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Wind power in the power systemimpacts on
reliability and efficiency
Adequacy
Balancing
Grid
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Flexibility and reserves

• Different time scale impacts of wind power
• Wind power impacts flexibility of conventional
  production units a lot at longer time scales
  (41224 hours)
• Reserves are operated during the operating hour,
  can be allocated some hours ahead

Real net load
Updated net load forecast
MW
Reserves
Net load forecast
Flexibility
Scheduled production
hours
0
1
2
3
4
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Increase in short term reserve requirements due
to wind

• Estimated by combining wind variability/forecast
  errors with that of load
• Statistically, comparing the distribution/3 to 5
  times standard deviation, without wind and with
  wind
• Can be made to different time scale data, for
  different time scale reserves in the system
• Usually the primary/instantaneous reserves are
  not much affected but more the secondary/tertiary
  load following reserves at time scales of 10
  minuteshours
• Larger impact if wind power forecast errors are
  left to be balanced with operating reserves
• Larger balancing areas ? reduced need for
  balancing
• The impact is estimated for the extreme cases,
  large variations of wind power are rare events

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Summary short term reserve requirements
Germany, Minnesota day-ahead
Four hours ahead
others in-hour

• different time scales for estimating the reserve
  requirement in-hour, 4 hours ahead, day-ahead
• UK, 2007 assumes 4 hours ahead wind variations
  (persistence forecast) combined with load
  forecast errors

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Increase in cost of balancing due to wind power

• In most cases even if high estimates of reserve
  requirements, the current conventional capacity
  can handle these and no new reserve capacity is
  needed in the system
• In all cases, clear increase in the use of short
  term operating reserves are seen
• This is also the experience of integrating wind
  power from Denmark and Spain
• Larger balancing areas ? reduced need for
  balancing and better resources for balancing
  (potential need for balancing through
  interconnection )

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Summary balancing costs

• Integration costs 0.5 - 4 /MWh
• Small compared to production cost /market value
  of wind power ( 40-60 /MWh)
• Not directly comparable due to only use of
  reserves or allocating investment for new
  reserve interconnection taken into account or
  not assumptions on thermal power costs

Experience from Denmark and Spain, cost of
balancing from electricity markets
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Summary of grid results

• Stability
• With limited penetration levels wind power can
  improve system performance by damping power
  swings and supporting post-fault voltage recovery
• At higher penetration levels requiring FRT
  capability for large wind power plants is
  economically efficient compared with modifying
  power system operation to ensure system security
• Grid reinforcements
• May be needed for stability, often needed if wind
  resource far from load centres and weak grid
• Building grid for the total wind power amount
  often significantly more cost effective than
  upgrading bit by bit

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Grid reinforcement costs from studies
DK studies from 20 to 50

• Not comparable
• Depends on wind resource location versus load
  centres
• Depends on how grid costs are allocated to wind
  power
• Grid reinforcement costs are not continuous,
  there can be single very high cost reinforcements

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Summary capacity value of wind power

• Even if mainly energy resource, wind has a
  capacity value to power systems. However, at
  larger penetrations the value decreases. Value
  decreases faster for smaller areas.

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Capacity value and capacity cost

• Cost estimates for the lower capacity value of
  wind power compared to thermal power plants
  should use correct comparison
• based on same amount of energy per year from wind
  (2000-3000 full load hours per year) and thermal
  power (6000-7000 h/a)
• The deviation between capacity value of wind
  power and capacity value of a thermal power plant
  with the same yearly energy production can be
  denoted as capacity cost
• if the power system with wind power or thermal
  power systems should have the same risk of
  capacity deficit, some capacity has to be added
• Added capacity is only used few hours per year,
  so important to use low investment cost plants
  for this purpose (Open Cycle Gas Turbines) or
  Demand Side Management.
• The range of 2-4 Euro/MWh for the wind power
  produced has been estimated by (Söder Amelin,
  2008).

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Main messages from comparisons

• The case studies are not easy to compare
• Different methodology, data, assumptions on
  interconnection
• Integration costs to be compared to f.ex.
  production costs or market value of wind power,
  or integration cost of other production forms
• Cost-benefit analysis integration costs vs.
  benefit from reducing total operating costs and
  emissions
• Issues impacting the amount of wind that can be
  integrated
• Large balancing areas aggregation benefits help
  reducing variability and forecast errors of wind
  power as well as help pooling more cost effective
  balancing resources.
• System operation/electricity markets at less than
  day-ahead time scales help reduce forecast errors
  of wind power.
• Transmission is the key to aggregation benefits,
  electricity markets and larger balancing areas.

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Recommendations for wind integration studies

• Capture the smoothed out variability of wind
  power production time series for the geographic
  diversity assumed
• Actual data from tens of wind farms and/or met
  towers or synchronized weather simulation
• Wind forecasting best practice for the
  uncertainty of wind power production.
• Examine wind variation in combination with load
  variations
• Capture system response through operational
  simulations
• Examine actual costs independent of tariff design
  structure
• Compare costs and benefits of wind power