Figure shows the comparison of the photon flux densities measured for the internal irradiation using three different amplifiers. The first prototype amplifier (EAP-00) was limited to a maximum electrical power uptake of 50 W and the employed wireless emitters featured a UVA-LED (OSA Opto Light OCU-440 UE365-X-T) with a rated radiant power of 80 mW each. In this case, the photon flux density perfectly follows the model previously established which estimates an effective output 𝑞 𝑊𝐿𝐸 of 17.5 nmol s -1 per emitter, corresponding to 5.7 mW radiant power, matching previously reported estimates for this configuration . A maximum photon flux density of 37.8 µM s -1 (12.4 W L -1 radiant power density) was achieved at 44 % fill factor. Studies at different scales of 25, 50, and 75 mL reaction volume showed that the photon flux density is scale-independent at constant fill factor, underlining its importance as critical parameter for up-scaling. However, the average power output of 5.7 mW is far below the nominal power of the employed highpower LEDs, which should be able to achieve up to 80 mW. Even accounting for the fact that they are driven by alternating current cannot explain this low value of 7 % of their nominal performance. Neither is the total radiant power (2.4 W) anywhere near the rated power of the amplifier (50 W), even accounting for inefficiencies in the wireless energy transfer and conversion into light energy. The limiting factor in this case was instead identified as insufficient electromagnetic field strength which led to insufficient voltage in the emitters to make full use of the LEDs' potential. Consequently, this system also showed a rather low wall-plug efficiency of only 2.9% in the best case (Table ). This is a consequence of the low use factor of the electromagnetic field by the WLEs so the majority of the power uptake is actually used for the upkeep of the electromagnetic field rather than to power the emitters. Therefore, the next prototype featured both an improved amplifier (EAP-01) with a nominal power output of 320 W as well as an improved design for the coils powering the electromagnetic field. The EAP-00 amplifier needed three coils connected in parallel due to its limited power output. Compared to the EAP-00 amplifier, the EAP-01 amplifier can drive the coils put in series. Therefore, each coil is driven by the full amplifier output current and not just one third of it. This leads to a higher magnetic field inside the reactor.