## 1 Introduction
[20] examined the mutual exclusion or complementarities among different benefits of a CSP station involving power generation profits, capacity benefits, reserve services and peak-shaving services. [PERSON] et al. [21] investigated the economic and advantages of a CSP reserve and EH reserve, but the results only verified the complementary effects among the CSP reserve and thermal unit reserve. In addition, there is a reasonable economic utilization range for renewable energy. The pursuit of 100% consumption would greatly increase the reserve scheduling cost and restrict the power system to receive more renewable energy, which greatly hinders the development of renewable energy. [PERSON] et al. [22] set the minimum objective of the system power failure loss cost and the unit operating cost to optimize the system reserve, which could balance system economy and reliability. However, the global optimum results could not be guaranteed due to the spinning reserve and system operation were optimized separately. [PERSON] et al. [23] formulated the chance constraints including loss-of-load probability (LOLP), reserve requirements and line flow limits, which were converted into a linear programming model and was solved by a decomposition-based method. In this work, in order to estimate benefits of a CSP station in the high renewables penetrated power system, a chance-constrained stochastic unit commitment model with a CSP station is proposed. A scenario-based method is employed to represent the uncertainty of renewable energy [24; 25]. The reserve planning method takes into account the chance constraints including \"expected load not served (_ELNS_)\" and \"expected wind and solar curtailment (_EWVS_)\" and optimizes reserve scheduling and system operation coordinately. The main contribution of our contributions can be summarized as follows. 1. A two stage stochastic UC model is established to research on the economic and reliable values of a CSP with TES/EH in the high renewables penetrated power system, concerning the uncertainty of wind power, PV and the solar energy received by CSP. 2. A chance-constrained method is employed in UC model to optimize the system reserves according to the scenario-based renewable energy forecast data. 3. The dispatchability and profitability of a CSP with TES/EH in unit commitment are verified through the comparative experiments among various system configurations. The remainder of this paper is organized as follows. Section 2 describes the model of a CSP station with TES and EH equipment. Section 3 develops chance-constrained stochastic unit commitment model. A number of case studies based on IEEE-RTS 24 nodes system are carried out in Section 4 and discussed in Section 5. Finally, Section 6 concludes our research. Model of Concentrating Solar Power (CSP) Station Equipped with Thermal Energy Storage (TES) and Electrical Heater (EH)  
CSP utilizes solar power to generate electricity just like PV station, however, the conversion process of CSP is totally different from PV. CSP station is composed of four main parts, namely solar field (SF), TES system, power block (PB), additional EH equipment and the corresponding cleaning vehicle [26]. Heat transfer fluid (HTF) realizes the thermal cycling among different blocks. CSP station collects solar energy in SF to heat HTF. The heated HTF partially flows into \(PB\) to drive the steam turbine and then generates electricity. The rest of HTF could be stored in TES as thermal energy to be further used [27]. The capability of CSP station to utilize TES system makes CSP a dispatchable resource as thermal unit. EH equipment could absorb excess electricity in the power system and convert it into thermal energy to be stored in the TES system for later conversion. Therefore, EH could exploit the excess room of TES and expand the operating range of CSP station.