Copyright © 2005 Advantica Inc. (USA Only) and Advantica Ltd. (Outside USA). All rights reserved by the respective owner. 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 Seeking a collaborative approach to estimation of OUG

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

The methodology and model Typical PRS layout

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)

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 Over 3Gb of data was received, filtered and processed

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 )/(CpmhkJP T   m  T  Cp P 

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.

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

Hot Water Bath Efficiencies E7 Transco technical Specification for Gas Fired Water Bath Heaters Part 1 Basic Heater requirements “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%

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

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

Model Validation 2000

OUG Usage Efficiency Total Flow (kWh) Total OUG (kWh) % OUG 100%7.13E E %7.13E E %7.13E E %7.13E E %7.13E E %7.13E E

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

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

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

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

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

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

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 conducted Provides 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

Solutions – pre-heater efficiencies Summarise and report findings from previous pre-heater efficiency trials Carry out pre-heater efficiency tests Use OUG model to calculate them

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

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

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