Performance Evaluation Concept for Ocean Thermal Energy Conversion toward Standardization and Intelligent Design
Performance Evaluation Concept for Ocean Thermal Energy Conversion toward Standardization and Intelligent Design
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DOI：
10.3390/en14082336
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发表时间：
2021-04
期刊：
影响因子：
3.2
通讯作者：
T. Yasunaga;K. Fontaine;Y. Ikegami
中科院分区：
文献类型：
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作者：
T. Yasunaga;K. Fontaine;Y. Ikegami
海洋热能转换（OTEC）利用一个非常简单的过程将主要储存在热带海洋中的热能转换为电能。在设计、运营和评估中，我们需要考虑OTEC的独特特性，以实现最佳性能或降低项目的电力成本。OTEC发电的概念和设计约束不同于传统的火力发电厂，这是由于利用了低温差。本研究从理论上认识了能量转换系统的独特性，并基于有限时间热力学和热源平衡条件，总结了适合于OTEC的性能评价方法。此外，还提出了海洋热能转换热效率归一化和火用效率的概念，将海洋中的可用热能定义为海洋中可传递的热能，将平衡条件定义为火用的死态。利用各种参考设计数据直观地显示了常规热效率与评价方法有效性之间的差异，并确定了常规热效率与火用效率之间没有明确的关系，而归一化热效率与火用效率肯定成正比。此外，火用效率显示了分级Rankine，Kalina和Uehara循环的有效性。因此，归一化热效率和火用效率对于分析系统的热质平衡和改进具有重要意义。
Ocean thermal energy conversion (OTEC) uses a very simple process to convert the thermal energy stored mainly in tropical oceans into electricity. In designs, operations, and evaluations, we need to consider the unique characteristics of OTEC to achieve the best performance or lower the electricity cost of projects. The concept and design constraints of OTEC power generation differ from those of conventional thermal power plants due to the utilization of a low temperature difference. This research theoretically recognizes the unique characteristics of the energy conversion system and summarizes the appropriate performance evaluation methods for OTEC based on finite-time thermodynamics and the equilibrium condition of the heat source. In addition, it presents the concept of normalization of thermal efficiency for OTEC and exergy efficiency based on the available thermal energy in the ocean defined as the transferable thermal energy from the ocean and the equilibrium condition as the dead state for exergy. The differences between conventional thermal efficiency and the effectiveness of the evaluation methods are visualized using the various reference design data, and it is ascertained that there is no clear relation between the conventional thermal efficiency and exergy efficiency, whereas the normalized thermal efficiency is definitely proportional to the exergy efficiency. Moreover, the exergy efficiency shows the effectiveness of the staging Rankine, Kalina, and Uehara cycles. Therefore, the normalized thermal efficiency and the exergy efficiency are important to analyze the heat and mass balance as well as improvement of the system.