WSP07315 - Laserfiche WebLink

Home Browse Search

B-2 Generally, firm power requirements involve scheduling higher monthly water releases in peak load months (typically December, January, July and August), and lower releases of water in months when electric power demand is less. This allows Western the limited ability to schedule greater purchases in low load months, when purchases are more economical. Long-term planning involves the determination of purchase power expenses, financial impacts to Basin Fund cashflows, and the sufficiency of established wholesale firm power rates. Using forecasted powerplant monthly release volumes, Western patterns releases within constraints at each powerplant to estimate available hourly SLCA/IP energy and capacity and to assess the need for seasonal purchases or sales. For Glen Canyon, hourly generation patterns are assumed for a typical weekday (Monday through Friday), and typical weekend days (Saturday, and Sunday) taking into account the daily fluctuation limit, ascending and descending ramp rates, and minimum and maximum flows. Seasonal and monthly decisions are then made whether to utilize either existing long-term energy purchase contracts, short-term or spot-market energy purchases, or combinations of these and other sources to satisfy contractual load obligations. Given the monthly pattern of forecasted releases, Western typically plans to purchase a majority of the on-peak energy during non-peak or "shoulder" months when it is usually least expensive. However, given restricted releases at Glen Canyon and Flaming Gorge and the pattern of monthly releases across a range of possible hydrologic conditions, purchases may be required during peak months and during on-peak hours for both weekend and weekdays at significantly greater expense. Purchase decisions are based on long-term purchase obligations, spot market energy prices, transmission availability, and any scheduled unit outages affecting other utilities, which affects prices and transmission. If SLCA/IP surpluses are expected, Western would quantify the magnitude of these surpluses, assess associated risks and benefits, and may extend short-term energy and capacity offers to existing firm power customers. Changes to forecasted reservoir operations can be expected throughout the water year due to the uncertainties of weather, expected snowpack, temperature patterns and streamflows (i.e, forecast error). Reclamation has recognized the significance of forecast errors and the need for an operational buffer at Lake Powell in its floodflow avoidance measures. As the monthly planned release volumes are modified to reflect changing conditions, Western must accommodate these changes in its load/resource planning and subsequent purchase or surplus sale activities.