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Flow Flexibility Capacity

Flow Flexibility Capacity. Joint Office 7 th December 2006. Effect of Within Day Demand Change. Consider situation where demand is falling:. Therefore imbalance should be resolved by flow change not by use of NTS storage. Effect of Within Day Demand Change.

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Flow Flexibility Capacity

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  1. Flow Flexibility Capacity Joint Office 7th December 2006

  2. Effect of Within Day Demand Change Consider situation where demand is falling: Therefore imbalance should be resolved by flow change not by use of NTS storage

  3. Effect of Within Day Demand Change Flexibility utilisation = cumulative offtake to 22:00 – (2/3) of daily flow Offtake Rate Planned Flow Rate at start of day 06:00 22:00 Time

  4. Effect of Within Day Demand Change The following example demonstrates the effect of a demand change at 22:00; 22:00 was chosen for the sake of clarity Offtake Rate Planned Flow Rate at start of day Actual Flow Rate 06:00 22:00 Time Change of flow to meet change of demand forecast increases flow flex utilisation

  5. Effect of Within Day Demand Change The following example demonstrates the effect of a demand change at 22:00; 22:00 was chosen for the sake of clarity Offtake Rate Planned Flow Rate at start of day Average Flow Rate Actual Flow Rate 06:00 22:00 Time Change of flow to meet change of demand forecast increases flow flex utilisation

  6. Effect of Within Day Demand Change The following example demonstrates the effect of a demand change at 22:00; 22:00 was chosen for the sake of clarity Offtake Rate Planned Flow Rate at start of day Average Flow Rate Actual Flow Rate Flexibility utilisation 06:00 22:00 Time Change of flow to meet change of demand forecast increases flow flex utilisation

  7. Impacts • DNs must ensure that their bookings of flow flex allow for this effect. • This artificially inflates the volume of storage required by a DN • Whilst the flow flex apparently taken has no impact on NTS storage • the NTS cannot simply oversell flow flex as they would then be unable to deliver if the DNs chose to use their allocation of flow flex to meet true diurnal demand • DN investment will be required to provide additional storage that is unnecessary • If a DN runs out of flow flex, they will have an incentive to keep within their flow flex limit by increasing their end of day stock • This hides the imbalance from the NTS, undermining both the “national” and “daily” elements of the balance • When demand has been under-forecast the opposite effect occurs with the apparent consumption of flow flex being understated • Thus NTS storage could be over-stretched without the connected parties having broken their flow flex limits

  8. Flow Flex Utilisation Correction • Presently: flow flex = flow (06:00 to 22:00) – 16/24 (end of day flow) • But can correct for within day demand change: Real flow flex utilisation = metered flow flex – correction Where correction = demand change * correction factor • Overruns triggered if real flow flex utilisation > booked flow flex

  9. Flow Flex Utilisation Correction Factors

  10. Example The following example shows how a falling demand throughout the day would result in a flow flex correction of 0.281 mcm representing 8% of the LDZ flow flex requirements

  11. Advantages of Correcting for Within Day Demand Change • Reveal real NTS diurnal support required by DNs • Avoids undermining NTS balance • No incentive for DNs to hide imbalance • Provide certainty to DNs when booking flow flexibility • Reduce costs of DNs investing to provide storage

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