Evaluating the optimal portfolio of VRE capacity to be integrated into the power system: A case study of Zambia

The Zambian power system is today dominated by hydropower. In recent years, low rainfalls and increasing electricity demand have led to massive power shortages. Integrating variable renewable energy (VRE) has been proposed as a measure for diversifying the generation portfolio and increase energy security. This paper evaluates the optimal solar PV and wind power capacity portfolio to be integrated into the Zambian power system within 2030. System cost is used as the metric for evaluating the economic impact of integrating different portfolios of solar PV and wind power capacity. The optimal portfolio is found as the one resulting in the lowest system cost, and is identified as a portfolio consisting of 1470 MW solar PV capacity and 630 MW wind power capacity. Brief load flow analyses, with the optimal portfolio of VRE capacity integrated into the system, suggests that the current grid is suited for integrating the optimal portfolio of new VRE capacity, given the assumed distribution of new power plants. From a technical perspective, the flexibility of the dispatchable hydropower plants in the system is therefore considered the most critical factor when integrating renewable energy into the system. However, increasing the share of wind power capacity in the portfolio decreases the magnitude of average daily ramping required from hydropower plants. The findings presented in this paper can serve as a basis for government strategies in Zambia, and in similar countries in Southern Africa, for assessing integration of renewable energy sources in power systems.