Capacity value of photovoltaic and wind power plants in an isolated Mini-grid in the Kingdom of Saudi Arabia

Solar Photovoltaic (PV) and Wind power plants are becoming increasingly cost competitive when compared with conventional thermal power plants and in the not far future may set the ceiling price of electricity in many markets. The Kingdom of Saudi Arabia (KSA) is internationally known for its hydrocarbon reserves but is less recognized for its renewable energy resources, especially wind energy. These renewable energy resources, although known as Variable Energy Resources (VERs), can be efficiently integrated into conventional power systems to provide stable and reliable electricity, whether for national power systems or for isolated Mini-grid power systems in KSA. Traditional capacity measures as Capacity Factor (CF) and Reserve Margin (RM) are not able to deal with the intermittency of Wind and PV power plants. Statistical and probabilistic measures coming from System´s Adequacy methodology as Effective Load Carrying Capability (ELCC), Equivalent Firm Capacity (EFC) or Equivalent Conventional Power Plant (ECPP) are available to assess the capacity value of VERs. All of these methods are based on Generation Adequacy where VER is added to conventional power plants to fulfil the load. A case study was completed for a Mini-grid within the Saudi Electric Company´s (SEC) Southern Operating Area (SOA) where the Loss of Load Probability (LOLP) for the conventional thermal power plant was estimated and the addition of VER is assessed by using ELCC. Based on the available load data and VER profiles for PV a Capacity Credit of 51.8% was estimated, declining at a rate of 2.2% per MW_p of additional installed capacity. The ELCC for Wind was estimated to be 19.4%, declining at a rate of 1.4% per MW of additional installed capacity. It was also found that using VER improves the system reliability in terms of Loss of Load Expectation (LOLE). While excessive VER production does not impact LOLE it does impact the economics. A penetration of up to 25% wind or 30% PV does not result in curtailing VER production.