Abstract Accurate determination of direct normal irradiance (DNI) is essential for evaluating and monitoring of concentrating solar power (CSP) and solar process heat (SPH) plants. Currently, a bi-axially tracked Pyrheliometer (PHM) is the most accurate measuring device, but requires high maintenance effort and is cost-intensive. As an alternative, the cost-effective pyranometer SPN1 was investigated by comparing highly resolved minute mean DNI measurements of two SPN1 devices to a reference PHM at the Institute for Solar Technology SPF in Rapperswil (Switzerland). To reduce systematic errors, a linear and a quadratic correction function have been applied to four years of measurements. They reduced the root mean square error RMSE from 48.8 W/m2 (11.5% of mean PHM DNI = 426 W/m2) to 37.9 W/m2 (8.9%) and 29.6 W/m2 (6.9%), respectively. It is also shown that even recalibrations based on only one month of data already reduced the RMSE to maximum 33.4 W/m2 (7.8%), if conducted between April and September. Considering the impact of solar elevation and DNI range on the SPN1 accuracy by bifurcating the correction functions only resulted in a negligibly small improvement of the RMSE. Finally, the influence of SPN1’s DNI measurement accuracy on the performance analysis of a real SPH plant in Switzerland was evaluated. After recalibration and correction of DNI values, the evaluation of monitoring data yielded annual efficiencies that were 15% and 12% higher in 2014 and 2015, respectively. It is recommended to recalibrate SPN1 devices over a minimum of one month against a PHM according to the methods presented in this paper.

中文翻译：

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SPN1 总辐射表与直接日射表的重新校准及其与聚光太阳能过程热电厂评估的相关性

摘要 准确测定直接法向辐照度 (DNI) 对评估和监测聚光太阳能 (CSP) 和太阳能处理热 (SPH) 发电厂至关重要。目前，双轴跟踪太阳辐射表 (PHM) 是最精确的测量设备，但需要大量维护工作且成本高昂。作为替代方案，通过将两个 SPN1 设备的高分辨率分钟平均 DNI 测量值与拉珀斯维尔（瑞士）太阳能技术研究所的参考 PHM 进行比较，研究了具有成本效益的总辐射表 SPN1。为了减少系统误差，对四年的测量应用了线性和二次校正函数。他们将均方根误差 RMSE 从 48.8 W/m2（平均 PHM DNI 的 11.5% = 426 W/m2）分别降低到 37.9 W/m2 (8.9%) 和 29.6 W/m2 (6.9%)。还表明，如果在 4 月和 9 月之间进行，即使仅基于一个月的数据进行重新校准，也已将 RMSE 降至最大 33.4 W/m2 (7.8%)。考虑到太阳高度和 DNI 范围对 SPN1 精度的影响，通过分叉校正函数只会导致 RMSE 的微小改进。最后，评估了 SPN1 的 DNI 测量精度对瑞士一家真实 SPH 工厂性能分析的影响。在重新校准和修正 DNI 值后，监测数据的评估产生的年效率分别在 2014 年和 2015 年提高了 15% 和 12%。建议根据本文中介绍的方法针对 PHM 至少在一个月内重新校准 SPN1 设备。