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Own Use Gas

Own Use Gas. Review of 2000 Model. Overview. Summary of 2000 OUG project Information and data Model overview Original assumptions and recommendations Pre-heater energy losses overview Uncertainties Shipper concerns Possible solutions Initial recommendations

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Own Use Gas

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  1. Own Use Gas Review of 2000 Model

  2. Overview • Summary of 2000 OUG project • Information and data • Model overview • Original assumptions and recommendations • Pre-heater energy losses overview • Uncertainties • Shipper concerns • Possible solutions • Initial recommendations • Seeking a collaborative approach to estimation of OUG

  3. Shrinkage • Based on overall throughput • Leakage from low pressure network • Own Use Gas for pre-heaters • Theft of Gas • Advantica carried out study into the estimation of OUG in 2002 using data from 2000

  4. The methodology and model • Typical PRS layout

  5. Information and data • All NTS and LTS sites using pre-heating • Flow, inlet, outlet pressure, exit temperature • Data unavailable for some LDZs • Basic pre-heater meter readings from ~80 sites • Generally poor quality • Total system throughput • Pre-heater survey data • Site name, location etc • Operational measurements/limits • Ground temperatures – from work on statistical analysis of national and regional temperatures (2000)

  6. Information and data cont… • The percentage of sites from which suitable data was acquired was: • NTS: 64% - missing data for West Midlands LDZ North Wales LDZ • LTS: 34% - missing data for East Anglia, North West, and Scotland LDZs • Giving an overall site coverage of 42% for hourly data over the year 2000. • Over 3Gb of data was received, filtered and processed

  7. D D T T m & The methodology and model • The method is based around the equation • Where: • is the mass flow rate (kg/h), • is the rise in temperature in the heater (deg C), • is the specific heat capacity of the gas (kJ/kg/K), • is the efficiency of the heater and • is the energy used in the heater (in kJ/h) 1 = P ( kJ / h ) m Cp & h Cp h P

  8. Assumptions • Initial gas inlet temperatures set to Ground Temperature data for each LDZ throughout the year • Outlet temperature set to 0 deg C if no set-point available • Heaters are operational throughout the year • Preheat requirements are assigned to each station rather than by heater • LDZ pre-heater efficiencies are the same as NTS pre-heater efficiencies.

  9. Assumptions cont… • OUG usage estimated for missing LDZs using monthly scaling factor based on other LDZ data • A range of Hot Water Bath pre-heat efficiencies used in analysis • Used a figure of 50% based on previous OUG model assumptions and research reports

  10. Hot Water Bath Efficiencies • E7 Transco technical Specification for Gas Fired Water Bath Heaters Part 1 Basic Heater requirements 1993. • “Heat loss in flue gases shall not exceed 25% of gross heat input.” • “Heat losses from outer shell and associated gas pipe work shall not exceed 1% of the declared heater output.” • Thermal efficiency of Water Bath Heaters at Alrewas AGI MRS 403 • Efficiencies under various operating conditions between 53 and 66% • Efficiency tests on Water Bath Heaters at Coleshill AGI MRS I 2912 • Quotes range 58 to 66.5%

  11. Typical Water Bath Heater Flue Losses 25-40% Surface losses 0.5-1% OHT 9.1

  12. Hot Water Bath Energy Losses • A number of studies carried out in the early 80’s • Main energy losses via flue gas in the heating process • Surface losses account for 0.5-1% total energy lost • Highlighted that most pre-heaters operated below design efficiency (design efficiency typically around 70%) • Typically 30-42% in flue losses • Experiments showed this could be improved with correct burn/air flow rates

  13. 4.50E+06 4.00E+06 3.50E+06 3.00E+06 2.50E+06 Towton kWHrs 2.00E+06 1.50E+06 1.00E+06 5.00E+05 0.00E+00 Jan- Feb- Mar- Apr- May- Jun- Jul- Aug- Sep- Oct- Nov- Dec- 00 00 00 00 00 00 00 00 00 00 00 00 Months Model Validation 2000

  14. OUG Usage

  15. Uncertainties • Pre-heater efficiencies • Control regime of pre-heaters • Ground temperature assumptions • Scaling factor to estimate pre-heater consumptions for LDZs with missing data

  16. 95% confidence intervals attributed to missing data 0.0102% (assuming a heater efficiency of 50%). and 0.0137% (assuming a heater efficiency of 50%). Including variation in efficiency of the pre-heaters, the actual OUG percentage figure may lie between: 0.0073%(with 70% efficiency) and 0.0229%(with 30% efficiency) Uncertainties cont…

  17. Recommendations 2002 • Better estimation of pre-heater efficiencies • Include control strategies for pre-heaters • Improve mapping of sites with pre-heat and incomplete telemetry to similar sites • Extend metering of pre-heaters to improve model validation

  18. Summary of Shipper Concerns • Original study is 4 years old, data is 6 years old and likely to be out of date • Limited data impacts the accuracy of the model • Real pre-heater efficiencies are much lower than quoted in report • Insufficient meter readings to properly validate the model

  19. Small %OUG variation Large variation in % OUG partial analysis using 2005 data for 3-4 LDZs Review findings, potentially do remaining LDZs Model suitable for other years Solutions – Age of the model Investigate model sensitivity

  20. Has data quantity/quality improved for key variables? partial analysis using 2005 data for 3-4 LDZs Review findings, potentially do remaining LDZs No - need improvement plan Solutions – impact of missing data Investigate model sensitivity

  21. Solutions – pre-heater efficiencies • Summarise findings of previous pre-heater efficiency trials • Covers various pre-heater efficiency tests • Provides evidence of typical pre-heater efficiencies from the output of the experiments conductedProvides information needed to carry out on-site efficiency tests • Carry out pre-heater efficiency tests • Requires on-site monitoring equipment • Timeline significant as tests require variety of operating conditions • Use efficiencies to validate the model • Test pre-heaters makes/models that are most commonly installed • Use OUG model to calculate efficiencies

  22. Use model to calculate OUG Compare OUG vs consumption Determine Hot Water Bath efficiency Alternative solution – use model Site flows, pressures, temperatures Pre-heater metering

  23. Use model to calculate OUG Compare OUG vs consumption Solutions - validating the model Determine Hot Water Bath efficiency Site flows, pressures, temperatures Pre-heater metering

  24. Initial Recommendations • Model sensitivity analysis • Summary of pre-heater efficiency work • And/or • Validate model by carrying out pre-heater efficiency tests on sites with good telemetry and metering • Determine pre-heater efficiencies using wider sample of meter readings assuming model correct • Report findings and present back to forum

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