Irradiance to Illuminance Conversion

The standard for measurement of solar irradiance utilizes the units of watts per meter squared (W/m2). Irradiance meters are both costly and limited in the ability to measure low irradiance values. With a lower cost and higher sensitivity in low light conditions, light meters measure luminous flux per unit area (illuminance) utilizing the units of lumens per meter squared or lux (lx). An effective conversion factor between W/m2 and lx would enable the use of light meters to evaluate photovoltaic performance under low solar irradiance conditions. A survey of the literature found no definitive and readily available "rule of thumb" conversion standard between solar irradiance and illuminance. Easy-to-find Internet sources contain conflicting and widely varying values of ranging from 688449 to 21000 lx for 1000 W/m2 (1 Sun) of solar irradiance. Peer-reviewed literature contains Luminous Efficacy equivalent values ranging from 21 to 131 lx per W/m2. This manuscript explores the relationship and establishes a theoretical and laboratory measurement guide for the conversion between solar irradiance and illuminance. The conversion factor includes standard data, and equipment calibration accuracy and uncertainty estimates. Solar Irradiance of 1 Sun (1000 W/m2) for an LED-based solar simulator is (116 ± 3) klx and (122 ± 1) klx for outdoor sunlight.

测量太阳辐照度的标准采用每平方米瓦特（W/m2）的单位。辐照度计成本高昂且在测量低辐照度值方面的能力有限。低成本的亮度计在低光条件下具有较高的灵敏度，它们通过单位面积的光通量（照度）来测量，使用的单位为每平方米流明（lx）或勒克斯。W/m2与lx之间的有效转换系数能够使亮度计在低太阳辐照度条件下评估光伏性能。文献综述发现，在太阳辐照度与照度之间缺乏明确且易于获取的“经验法则”转换标准。易于获取的互联网资源包含了从688449至21000 lx不等，对于1000 W/m2（1太阳单位）的太阳辐照度的冲突和广泛不同的数值。同行评审的文献中包含了从21至131 lx每W/m2的发光效率等效值。本文档探讨了两者之间的关系，并建立了太阳辐照度与照度之间转换的理论和实验室测量指南。转换系数包括标准数据、设备校准准确度和不确定性评估。基于LED的太阳模拟器的1太阳单位（1000 W/m2）的太阳辐照度为（116 ± 3）klx，户外阳光下的值为（122 ± 1）klx。