Light energy conversion optimization

The rate of H2 production by one unit of photobioreactor s volume is not useful for estimation of strain capabilities or for measurements of efficiency of light energy conversion. However, it is useful unit of measurements for optimization of hydrogen production by particular photobioreactor. From practical point of view it does not matter how much cells are in the photobioreactor or how much hydrogen is produced by one unit of illuminated surface. The rate of hydrogen production by the whole photobioreactor is of first importance. For a comparison of different photobioreactors it is better to express rate of hydrogen photoproduction per unit of its volume. So, it is practical unit for estimation of actual hydrogen photoproduction. 

We are interested in the efficiency of the light energy conversion which can be calculated for monochromatic light at the maximal absorbance of chlorophyll with optimal use of the light quanta from the ratio between the stored and the absorbed energy ... 

The spectral response of two devices with different thin PEOPT layers is shown in Figure 15-24. The IPCE for the 30 nm PEOPT device is as high as 23% at the maximum and still 17% for the thicker device. Also of importance is the similarity between the action spectrum and the absorption spectrum of the conjugated polymer. Both curves are very similar with the absorption spectrum slightly red-shifted. The energy conversion efficiency of the most optimized device was calculated to be 1.7% at low light intensities (15 pW/cm ) under monochromatic illumination. 

Rabinowitch discovered this redox equilibrium was the most light-sensitive known -thionine dyes absorb at 500-700 nm, comparable with values of maximal solar radiation - and as a result would possess a high level of PG sensitivity. As explained in the later sections, the thionine-iron (a dye and reductant, respectively) redox cell yielded a low energy conversion efficiency (<1 %), but the results were somewhat promising due to the ability to manipulate the dye and/or reductant - and subsequently established much research into optimization of the necessary components within the system [9, 15]. 

Organic dyes having appropriate HOMO and LUMO levels can be tuned to optimize the light to electrical energy conversion. The photocurrent action spectrum obtained with the Ti02 film coated with ascorbic acid is shown in Figure 21-19. The spectrum is characterized by a maximum located at 415 run, closely matching the absorption of the... 

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