Ideally, a reaction system has both high STY and PSTY and is readily scalable into multi-liter dimensions. However, as can be seen in Table , this is difficult to achieve. While conventional stirred tank reactors with immersion lamps can have quite high PSTY of around 100 mmol d -1 W -1 in optimized systems, their productivity is rather low, especially at larger scales. Microcapillary systems tend to have an order of magnitude higher productivity but lower efficiency, mostly due to reflection and transmission losses. They also lack the option of conventional scale-up and are limited to numbering-up approaches.