Open University Integrating Renewables Conference 24 January 2006

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Open UniversityIntegrating Renewables
Conference24 January 2006

• Wind power on the grid
• What happens when the wind stops blowing?
• David Milborrow
• david.milborrow_at_btinternet.com

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Scope

• MUST examine electricity networks
• Problems with intermittent generation sources,
  e.g. nuclear, gas, cross-channel link, etc
• Behaviour of wind plant
• Assimilating wind into networks
• Issues and costs
• Storage
• Capacity credit
• Denmark and Germany Lessons to learn?

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• Electricity systems

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Why integrated systems?

• Smoothing of Demands and Generation sources
• Peak/average ratios
• House 15
• UK 1.5
• Lower plant margins needed -
• House at least 2peak
• Large electricity system 1.2 peak
• All leads to LEAST COSTS

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Firm power is a concept ONLY

• UK-France link
• 5 trips, Jan-Jun 2005, "cause unknown"
• 24 Jan, 0337, 1351, 9 May, 0656, etc
• Outage times cover maintenancefaults
• Source UCTE
• 2. Typical utility (ERCOT) forced outages 2,
  7 planned outages

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Reserves in a power system
Pumped storage is used as reserve All can cope
with demand increase or decrease Voltage
reductions may be used in emergencies
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Wind characteristics
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Smoothing makes a difference

• Wind turbines smooth wind variations
• Wind farms smooth them more
• Wind farms over the country smooth them even
  more!
• We now have data from Denmark that illustrates
  this

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Smoothing of power swings
Time interval 1 hour
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Running electricity systems

• Managing electricity systems is all about
  managing risks
• All estimates of uncertainty come with a range of
  probabilities, and
• Uncertainty margins do not add arithmetically a
  sum of squares law applies
• So the extra impacts of wind are small

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Costing the effects of wind

• Scheduling error with wind enables extra reserve
  capacity needs to be estimated
• Establish cost of extra reserve, based on
• Reduced efficiency of part-loaded plant
• Cost of plant, or,
• Market rates
• System operators do not care what the reserve is
  as long as it can increase or reduce output
  when asked

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Extra back-up capacity
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Extra costs for backup
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Capacity creditsThe Firm power issue



?
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Capacity credits depend on-

• Amount of wind on system
• Wind speeds
• Wind turbine types
• Winds at time of peak demand
• Utility operating proceduresWhen normalised
  for differences in wind speed, good agreement
  between most estimates for northern Europe

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Capacity credits - UK
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5 days in the life of west Denmark (January 2001)

• Even with 2400 MW of wind, demand variations
  still predominate
• Wind reduces net demand at peak times

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Storage
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Storage

• "Renewables need storage" ?
• Rather misleading!
• Only the intermittent sources
• "Storage can transform the economics of the
  intermittent renewables" ?
• Only if they are very low cost!
• Most studies conclude that economics must be
  studied separately may be useful to system, or
  as reserve

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Storage - problems

• With dedicated storage How do you size the
  store?
• Can you be sure it will not "overflow"
• Or run out during calms
• Very difficult to get best value from a store
  UNLESS USED FOR BENEFIT OF SYSTEM
• Even then Valuegtcost? is the acid test
• US DoE and UK SYSTEM cost targets 500/kW
• more if paid for ancillary services
• Economics of isolated systems are site-specific,
  so dedicated storage may be worthwhile

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Total extra cost impacts
Extra cost to consumers
Lower cost to consumers
Source Windpower Monthly, January 2006 method,
Power UK 109
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Lessons from Denmark and Germany

• West Denmark (20 wind) Irrelevant, say
  critics
• but links with Sweden, Germany and Norwayare
  finite, so effective penetration about 10
• and S.O. could manage with 100 wind without the
  links, or storage
• Germany (6 wind)but wind speeds lower than UK
  so
• higher balancing costs,
• low capacity credit

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Wind integration conclusions

• Thermal power sources (and consumers) will
  determine bulk of reserve costs for many years to
  come
• Capacity credits? Yes, roughlyaverage power
  declines as wind increases
• Problem areas?
• May be preferable, once wind input exceeds 10,
  to curtail wind output on a few occasions
• ..but wind will NEVER impose jolts on the
  system comparable with loss of a circuit of
  cross-channel link, or a 1320 MW nuke

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Thank you!
The End