Page 47 - Gi_April2020

igem news

DNV GL’s Jane Harrison, Senior
Network Analysis Consultant,
and Divyesh Mistry, Senior
Pipeline Consultant,
summarise the research as
the latest draft goes out for
industry consultation

AS PART OF THE ONGOING review and
update of IGE/GL/1 Edition 2 Planning
of gas distribution systems of maximum
operating pressure (MOP) not exceeding
16bar, the review panel has debated
the suitability of the design equations/
curves (Appendix 5) for modern
housing/appliances.
IGEM has funded a review of the FIGURE 1 NEW PREDICTED SIX MINUTE DESIGN CURVES FOR ALL CENTRAL HEATING GROUPS, AVERAGE ANNUAL CONSUMPTION OF 12000KWH
equations with the potential for revised
design diversity coefficients for use when IFI19 (an Ofgem Innovation Funding 1980 (grey dash), 1980-1990 (blue dash)
undertaking network design of mains to Incentive project from 2008), 564 loggers and post-1990 (pink dash).
multiple (two or more) consumers. were installed across a range of domestic This figure shows the differences in
In the late 1970s, British Gas asked premises in the Cadent network. the predicted design load per consumer,
for each region to design the mains and The loggers recorded flow data over a depending upon which property
service layout for a specified estate with period of two years with the aim of gaining grouping equation is used.
varying results. A key area of difference a better understanding of consumer For a smaller number of consumers,
was in the estimation of maximum demand. With permission from Cadent, the post-1990 equation generates
loads that systems would supply. DNV GL reviewed this consumer data a higher design load per consumer
Consequently, in the 1980s, British and has updated the design diversity compared to both the pre-1980 and the
Gas undertook some engineering equations for load groupings similar to 1980-1990 equations.
load research to try and understand those in IGE/GL/1 Appendix 5. This finding is thought to be due to
consumer behaviour and its application the higher proportion of combi boilers
in the design of networks. This finding is thought to be due present in post-1990 housing. These
The results from this work provided boilers produce hot water on demand
the basis for the design load equations/ to the higher proportion of combi and hence have a higher initial peak
curves in DEC 86/600 Planning and boilers present in post-1990 gas flow to meet this requirement.
Design of Distribution Systems (1986) and housing. These boilers produce Therefore, while their annual gas
consequently IGE/GL/1 Planning of gas consumption is lower than a traditional
distribution systems of MOP not exceeding hot water on demand and hence boiler, the design load is higher.
16bar, Edition 1 (1997) onwards. have a higher initial peak gas This effect has its highest magnitude
There is consensus in the industry flow to meet this requirement for single properties and small group
that the peak values and diversity sizes, where there is little diversity. For
equations generated from the data all three curves, for a larger n (number
collected in the 1980s may no longer The new methodology is based on of consumers) the non-coincidence
reflect the current housing stock or data gathered at six-minute intervals of these peaks (increased diversity)
consumer behaviour. and takes account of the daily profile, reduces the design load per consumer,
Other research projects have been rather than just the peak value in the as expected.
undertaken over the past 20 years by day (which was the method used to Initial results indicate that in all
DNV GL (when it was BG Technology) produce the current equations in GL/1). cases the new equations result in a
and National Grid (when it was This allows demand patterns for reduced design load per consumer,
Transco), but the industry has not multiple sites to be modelled far more where n is small compared to the
developed or agreed any definitive new accurately because demand profiles current equations in IGE/GL/1
relationships from these. are overlaid and there is therefore no Appendix 5.
Consequently, there has been no assumption of coincidence of peaks. For both the pre-1980 and the
further refinement of the relationship The number of domestic consumers 1980-1990 equations, there is a
between design flow rates and annual in the IFI19 data is similar to the slight increase in the design load
quantity or the modelling of diversity. number of consumers in the data sets per consumer for a larger number
Work is currently being undertaken used to develop the original equations. of consumers. The IGE/GL/1 panel
by SGN and DNV GL through the Real The new design equations reflect is reviewing these findings and will
Time Networks project to review the use of modern appliances and look to include the new equations and
modelling principles, such as peak insulation, along with more current example curves within the next draft of
flows and demand diversity. This consumer behaviour. As an example, the document.
Ofgem-funded innovation project is the curve in Figure 1 compares an
still in progress and the results will be average annual consumption figure IGEM/GL/1 Edition 3 is out for comment.
shared with the industry in the future. of 12,000kWh for all three new load Comment on this and other IGEM
In one of the more recent projects, groupings with central heating: pre- standards at www.igem.org.uk

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IGEMNews_GL1.indd 2 12/03/2020 12:26