AEMO EDD312 (2012)
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EDD312 (2012) is the preferred index for modelling Victorian medium-to-long term gas demand. AEMO will be using this index for modelling Victorian medium-to-long-term gas demand in the 2014 National Gas Forecasting Report (NGFR). EDD312 indicates three-hourly observations between 3am of the current calendar day to 12am of the following calendar day.
The EDD312 (2012) formula is shown in the table below.
EDD312 (2012) = Temperature Degree Day (DD312) Wind chill
0.037 * DD312 * 0.604 * Wind312
0.144 * Sunshine hours
2 * Cosine (2*PI*(day – 190)/365)
Temperature T312: This is the average of the eight three-hourly Melbourne temperature readings (in degree Celsius) from 3am to 12am the following day inclusive as measured at the Bureau of Meteorology’s Melbourne Station. Equal weighting is applied to all observations.
The Degree Day (DD) DD312 = 18 – T312 if T312 < 18
= 0 if T312 is greater than or equal to 18
T312 = (T3AM + T6AM + T9AM + T12PM + T3PM + T6PM + T9PM + T12AM) / 8
18 degrees C represents the threshold temperature for residential gas heating – this threshold (of about 65 degrees F) is a fairly common standard internationally.
Average Wind312: This is the average of the eight three-hourly wind observations (measured in knots) from 3am to 12am the following day inclusive measured at the Laverton and Moorabbin Stations. Equal weighting is applied to all observations.
A localisation factor is applied to account for the shift from the Melbourne wind station (closed in 1999) to the average of Laverton and Moorabbin wind stations in order to align them with the Melbourne wind station reading. This factor is highlighted in red.
W312 = (W3AM + W6AM + W9AM + W12PM + W3PM + W6PM + W9PM + W12AM) / 8
Sunshine Hours: This is the number of hours of sunshine above a standard intensity as measured at the Weather Bureau’s Tullamarine Station.
Seasonal Factor (COSINE function): This factor models seasonality in consumer response to different weather. It indicates that residential consumers more readily turn on, adjust heaters higher or leave heaters on longer in winter than in the shoulder seasons for the same weather or change in weather conditions. For example, central heaters are often programmed once cold weather sets in resulting in more regular use. This change in consumers’ behaviour is captured in the Cosine term in the EDD formula, which implies that for the same weather conditions heating demand is higher in winter than in the shoulder seasons or in summer.