Chapter 3
Contribution of Variable Power Sources to Supply Adequacy
Previous chapters have dealt with the operational impacts of variable power sources such as wind and solar power. These impacts refer only to the operations time frame, which might vary from a few seconds to several minutes or hours. In the operational time frame, the impacts that need be managed (as described by the operational experience and desktop studies reviews) are mostly constrained to the need to compensate fast wind variations within the different dispatch time frames so that demand is met without the need for considerable amounts of new operating reserves. As described in the previous chapters, system flexibility is key to containing the operational impacts and costs of managing increased amounts of renewables, when operational impacts and associated costs start becoming more noticeable. In the previous chapter we explained the difference between operating reserves and long-term planning reserves. Long-term planning reserves are required to ensure the system will be able to meet the demand. The ability of a system to meet current and future demand is usually referred to as supply adequacy. Sometimes terms are used interchangeably and supply adequacy is also referred to by some as supply security. In this chapter we will use the term supply adequacy.1
Definitions and Metrics for Supply Adequacy The ability of a system to meet current and future demand is largely determined by the expected demand and the ability of existing and future sources to meet such demand. Adequacy will depend as well on the ability of the system components to be there when needed. All components in a system are subject to potential failure and such potential failures have direct impacts on the adequacy of the system. In addition, the type of supply has a great deal of impact on system adequacy. For instance, systems that depend on a large amount of hydropower have traditionally understood that water is not always available in the same amounts in the different seasons of the year. In addition, extreme dry years could lead to lower
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