Identifying the optimum storage capacity for a 100-MWe concentrating solar power plant in South Africa

[摘要] ENGLISH ABSTRACT: Central receiver power plants generate renewable electricity by exploiting theenergy provided by the sun. The conditions experienced in the Northern Caperegion of South Africa provide the ideal conditions for the development of theseplants. Without a storage medium these plants have capacity factors in the rangeof 25-30%. The inclusion of a thermal energy storage medium provides the abilityto increase the capacity factors of these plants. Although storage increases thecosts, it results in better utilisation of the power block and a decrease in thelevelised electricity cost (LEC). Eskom intends building a 100MWe centralreceiver dry cooled power plant in the Upington region. This research identifiesthe appropriate storage medium and ideal storage capacity to achieve the lowestLEC.A literature survey was performed to identify the different methods of storage thatare available. The different storage methods were evaluated and the best storagemedium for a central receiver power plant based on the developments of thevarious storage technologies was identified.To determine the costs associated with a central receiver power plant, datapublished by NREL was used. Different plant parameters were required toevaluate the costs. A power plant model based on efficiencies and energy balanceswas created to determine the required plant parameters. It provided the ability todetermine the effect of changing different plant parameters on the LEC andestimate the plant output. The power block parameters were initially varied todetermine the most efficient power block configuration. Once the most efficientpower block configuration was identified the solar field and storage parameterswere varied to determine the plant configuration which resulted in the lowestLEC.The most efficient power block configuration of 0.4206 was found for a systemcomprising of six feedwater heaters with the feedwater temperature of 230°C,main steam pressure 140 bar and an exit steam generator salt temperature of290°C. A solar multiple of 3.0 with 16 hours of storage resulted in a LEC ofR1.41/kWh with no system constraints. A capacity factor constraint of 60%resulted in a solar multiple of 1.8 with 8 hours of storage and a LEC ofR1.78/kWh.

[发布机构] Stellenbosch University