Load Forecasting Model was developed for hourly and daily forecasting for the Laclede Gas Company, a large distribution company in the St. Louis area. The load is concentrated and largely weather-sensitive. Various methods and weather factors were evaluated using a Multi-Linear Stepwise Program on a digital computer. The equation that was selected included temperature, change in temperature, wind, radiation, and ground temperature. Other than temperature, the ground temperature had the greatest effect on the load. Essentially, the day is broken down into six periods and then into hourly amounts based on percentages of these periods.
The Laclede Gas Company is a gas distribution utility serving approximately 500,000 customers mostly in the St. Louis area. The system load is extremely weather sensitive and weather is very changeable from hour to hour and day to day. The average daily temperature ranges from below zero (0°F.) in the winter to above 90°F in the summer. This results in much load variation from hour to hour and day to day during the winter. The daily load varies from about 1200 MMCF on a peak day to below 100 MMCF on a summer day. (Figure I). In the early "fifties" the load was fairly flat; very little peak shaving was required and the natural gas pipeline adequately supplied the load. As more residential customers were added, the pipeline supply reached its limit. The low load factor, brought about by the predominantly weather sensitive load and the lack of significant base load, made pipeline gas prohibitively expensive under the demand and commodity rate schedule. Peak shaving means available at this time; above ground holder stations, propane-air and manufactured gas plants could not be economically expanded to meet the needs. Various means of alternate supplies were investigated and a natural gas underground storage field was selected as the most practical solution. Gas could be injected on days when the load was less than the contract demand quantity and withdrawn on days when the load exceeded the contract demand. An aquifer storage field near the service area vas discovered and successfully tested. Through the years, it was expanded to its maximum and then a propane cavern vas also constructed and a pipeline connected to the product lines for a supply. With the use of this storage field for a supply and the expansion of propane supplies, the pipeline currently supplies about fifty percent of a peak day. Re-injection during off peak loads has increased the amount of days that the contract demand pipeline gas can be utilized from about 14 days to over one hundred and twenty days during a normal weather beating season. With all these changes, the problem of scheduling the various sources of supply has become much more complex. Hourly, daily and winter season capacities, pipeline daily overrun penalty charges and hourly limitations, and the different costs of the types of peak shaving supplies make efficient scheduling and control mandatory. (Figure II).