Assessing future generating resources for energy, capacity, flexibility

The Council’s Power Planning Division staff is developing the Seventh Power Plan resource strategy, essentially a blueprint for acquiring generating resources and energy efficiency to meet future demand for electricity.

This is a complex task because the region’s power supply has become more complex over the past several decades. In the past, power planners simply designed resource strategies to meet the predicted energy needs of the region, making sure that electricity generation would be sufficient to meet anticipated demand. If there were shortfalls, during extreme heat or cold, for example, the vast capability of the Northwest hydroelectric system was generally sufficient to fill in the gaps.

Today, with the addition of more than 8,000 megawatts of variable wind generation and with increasing constraints on the operation of the hydroelectric system, to aid juvenile salmon and steelhead migration, for example, it no longer can be assumed that simply planning to meet anticipated energy demands will be sufficient.

Accordingly, the resource strategy today must include provisions to meet anticipated demand (energy), peak loads (capacity), and the ability to integrate resources like wind and solar whose output can change significantly over short periods of time (flexibility). In short, the power system must not only meet annual energy needs and  hourly  peak loads, but match generation to loads within in each hour without falling outside a small margin of error required to maintain a stable power system.

At the Council’s Power Committee December meeting, the Power Planning Division staff proposed to use the Council’s GENESYS model to determine the amount of energy and capacity that will be needed in the future to keep the loss-of-load probability at or below the 5-percent reliability standard. This information will then be used in the Council’s Regional Portfolio Model when it tests alternative resource strategies to determine the economics of minimizing the cost of satisfying energy and capacity needs.

To assess flexibility needs, the staff is proposing to analyze both operating reserves and the ramping capability of the power system, but this will be a more complex task. The staff will work with other experts to develop an appropriate methodology, incorporating demand response and the potential for an energy imbalance market, which may change the supply of, and demand for, flexible resources in the region.

The staff plans to discuss its approach to modeling future capacity requirements with the Council’s System Analysis Advisory Committee and the Pacific Northwest Utility Conference Committee’s System Planning Committee. Staff also will engage these same groups on its proposed framework and analytical approach to addressing system operating reserves and flexibility.