Solar energy efficiency

In contrast to this engine efficiency, one defines the solar energy efficiency w as... 

Applying the same procedure for determining the maximum power characteristics as before and assuming moderately concentrated sunlight for which C = 389 [1], the solar energy efficiency w increases from 13% to somewhat above 60%. For the limit case of C = Cmax—all solar radiation is captured by our planet—w is close to 85%. 

Another way to improve on the solar energy efficiency w is to apply selective coating on the converter s absorbing and emitting surface. These coatings... 

In photosynthesis, absorbed solar radiation is captured as chemical energy. In this spontaneous natural conversion of absorbed solar radiation, the solar energy efficiency ranges from 0.8% for land plants to 6.6% for sea plants. In laboratory experiments efficiencies above 30% have been observed. Table 17.1 summarizes the results of solar energy conversion, as discussed in this chapter and where the value for wind energy creation is given as reported in [14]. 

Unlike room temperature solar PV and photoelectrochemical electrolysis, the hybrid approach utilizes energy of the full solar spectrum, leading to substantially higher solar energy efficiencies. The IR radiation is energetically insufficient to drive conventional solar cells, and this solar radiation is normally discarded (by reflectance or as re radiated heat.) On the other hand, in the hybrid approach, as seen in Fig. 2... 

The goal of this research field is to produce hydrogen by usage of solar energy, the so-called solar hydrogen production. In order to utilize solar energy efficiently, it is indispensable to develop visible-light-driven photocatalysts [3]. 

A series of chlorotricarbonyl rhenium(I) complexes based on benzathiazole derivatives have been reported [34]. One of the chlorotricarbonyl rhenium(l) complexes, shown in Fig. 38.3c, exhibits a solar energy efficiency of around 1.43-1.76% [44]. Compared to other rhenium(l) 2,2 -bipyridine complexes, these were found to have a redshifted absorption because the heterocyclic ligands have lower jr-to- 7r energy levels [44]. 

In summary, the initial energy and electron transfer events of photosynthesis are under tight kinetic control. Photosynthesis captures solar energy efficiently because the excited singlet state of chlorophyll is quenched rapidly by processes that occur with time constants that are much shorter than the fluorescence lifetime, which is about 5 ns in diethyl ether at room temperature. 

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