Abstract Four variants of the Organic Rankine Cycle (ORC) applied to geothermal power plants are optimized by means of numerical tools. These variants are: (i) the subcritical ORC with single-pressure heater (ORC/S/SC), (ii) the transcritical ORC with single-pressure heater (ORC/S/TC), (iii) the subcritical ORC with dual-pressure heater (ORC/D/SC), and (iv) the transcritical ORC with dual-pressure heater (ORC/D/TC). All the systems are recuperative and include a wet cooling tower. The objective function is the specific work output and design variables include operating pressures, mass flow ratios between the brine and the working fluid, superheaters effectiveness and cooling tower range. The systems are optimized for 20 different potential working fluids. The optimization is performed for inlet brine temperatures from 80 to 180 °C, and for ambient air wet bulb temperatures from 10 to 32 °C. The results show: (i) the superiority of ORC/D/TC for most of the cases, (ii) the relevance of using a dual-pressure heater at high sink temperature and low brine temperature, and (iii) the importance of choosing the right cooling tower range for an optimal power plant design.

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地热电厂优化设计：单压和双压有机朗肯循环的比较

摘要 通过数值工具对应用于地热发电厂的有机朗肯循环（ORC）的四种变体进行了优化。这些变体是：(i) 带单压加热器 (ORC/S/SC) 的亚临界 ORC，(ii) 带单压加热器 (ORC/S/TC) 的跨临界 ORC，(iii) 带双压加热器的亚临界 ORC -压力加热器 (ORC/D/SC)，和 (iv) 具有双压力加热器 (ORC/D/TC) 的跨临界 ORC。所有系统都是回热式的，包括一个湿式冷却塔。目标函数是具体的工作输出和设计变量，包括操作压力、盐水和工作流体之间的质量流量比、过热器效率和冷却塔范围。该系统针对 20 种不同的潜在工作流体进行了优化。对入口盐水温度从 80 到 180 °C 进行优化，环境空气湿球温度为 10 至 32 °C。结果表明：(i) ORC/D/TC 在大多数情况下的优越性，(ii) 在高水槽温度和低盐水温度下使用双压加热器的相关性，以及 (iii) 选择的重要性用于最佳发电厂设计的正确冷却塔系列。