This paper concerns the ongoing studies on a Concentrated Solar Power (CSP) plant in operation in Ottana (Italy), comprising a 629 kW organic Rankine cycle (ORC) unit fed by a linear Fresnel solar field. Hexamethyldisiloxane (MM) and “Therminol SP-I” are used respectively as ORC working fluid and heat transfer fluid in the solar receivers. A two-tank direct Thermal Energy Storage (TES) system is currently integrated in the CSP plant, serving as a direct interface between solar field and ORC. With the view of improving the solar facility, two alternative TES configurations were proposed in this study: a one-tank packed-bed TES system using silica as solid storage media and another similar one including encapsulated phase-change material (molten salt). Comprehensive mathematical models were developed for simulating daily behaviour as well as for assessing yearly performance of the various TES technologies. Furthermore, a preliminary economic analysis was carried out. Results showed poorer response of the one-tank TES system to large fluctuations in the ORC inlet fluid temperature, leading to reduction in the mean ORC efficiency (18.2% as against 19.7% obtained with the two-tank TES). Conversely, higher energy storage density and lower thermal losses were obtained adopting the one-tank TES, resulting in about 5% more annual solar energy yield. Invariably, equivalent annual ORC energy production of 0.92 GWh/year was obtained for the three TES configurations. Additionally, adopting a one-tank TES system meant that the purchase costs of a second tank and its storage medium (thermal oil) could be saved, resulting in investment costs about 45% lower and, ultimately, levelized cost of storage about 48% lower than what obtains in the two-tank TES system.

中文翻译：

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温跃层与用于聚光太阳能发电厂的两罐直接蓄热系统：比较技术经济评估

本文涉及对在 Ottana（意大利）运行的聚光太阳能 (CSP) 发电厂进行的研究，该发电厂包括由线性菲涅耳太阳能场供电的 629 kW 有机朗肯循环 (ORC) 装置。六甲基二硅氧烷 (MM) 和“Therminol SP-I”分别用作太阳能接收器中的 ORC 工作流体和传热流体。两罐直接热能储存 (TES) 系统目前集成在 CSP 工厂中，作为太阳能场和 ORC 之间的直接接口。为了改进太阳能设施，本研究中提出了两种替代 TES 配置：一种使用二氧化硅作为固体存储介质的单罐填充床 TES 系统，另一种类似的包括封装相变材料（熔盐）。开发了综合数学模型来模拟日常行为以及评估各种 TES 技术的年度性能。此外，还进行了初步经济分析。结果表明，单罐 TES 系统对 ORC 入口流体温度的大波动的响应较差，导致平均 ORC 效率降低（18.2%，而双罐 TES 为 19.7%）。相反，采用单罐 TES 可以获得更高的能量存储密度和更低的热损失，从而使年太阳能产量增加约 5%。对于三种 TES 配置，始终获得 0.92 GWh/年的等效年 ORC 能源产量。此外，