Light energy conversion system

Another important phytotoxic atmospheric pollutant that has been studied with respect to its inhibitory effects on plant photosynthesis is peroxyacetyl nitrate (PAN). This phytotoxicant applied for 30 min at 1 ppm depressed the incorporation of 1 C02 into intact pinto bean leaves, but only after visible tissue injury started to develop (20). From companion studies on isolated chloroplasts, it was concluded that PAN-induced inhibition was probably associated with the carboxylating reaction or the chloroplast light-energy conversion system leading to assimilative power. The inhibition appeared to result in a quantitative reduction (but not a qualitative change) in the early products of photosynthesis. 

The present chapter deals with the principles and recent advances in the investigation of light energy conversion systems based on semiconductor/liquid... 

Fig. 25). Alternatively, one can "reverse the process. Porphyrin array formation can start with imidazolyl zinc porphyrin, which can be immobilized using, for example, thiolate attachment on the electrode surface [90,91]. In this case the porphyrin attached to the electrode can serve as a molecular solder connecting the electrode to polymers made of hundreds of meso-meso-or bis(acetylene)-linked bis(imidazolyl zinc porphyrins) 55 [92]. Molecular wires or light-energy conversion systems could be built on the basis of such technologies. 

We have seen that, in photosynthetic bacteria, visible light is harvested by the antenna complexes, from which the collected energy is funnelled into the special pair in the reaction centre. A series of electron-transfer steps occurs, producing a charge-separated state across the photosynthetic membrane with a quantum efficiency approaching 100%. The nano-sized structure of this solar energy-conversion system has led researchers over the past two decades to try to imitate the effects that occur in nature. 

An earlier book, ACS Symposium Series No. 122, Thermodynamics Second Law Analysis, is an introduction to the direct application of the second law of thermodynamics to (1) process efficiency analysis and (2) cost accounting in energy conversion systems and chemical/metallurgic processes. Since the publication of that volume, there has been a steady growth in the interest in applying these methods, and hence, more applications that encompass a greater realm of processes have surfaced. The purpose of this sequel is to present these new applications—in particular those that shed additional light on the theory and practice of the subject. The reader may wish to refer... 

Sayama K, Mukasa K, Abe R, Abe Y, Arakawa H (2002) Photo-catalytic water splitting system into H2 and 02 under visible light irradiation mimicking a Z-scheme mechanism in photosynthesis. Solar Light Energy Conversion Team, Photoreaction Control Research Center, Advanced Industrial Science and Technology (AIST), Ibaraki, Japan... 

Light energy conversion and water-oxidation systems in photosynthesis... 

The emission spectrum of the sun consists approximately of 9 % UV light, 40 % visible, and 51 % IR [1]. Only UV, visible, and a small fraction of the near-IR can cause electronic excitation. Furthermore, we have to take into account that the excitation energy collected should be enough to drive the chemical reactions we would like to use to store the solar energy. Therefore, any practical photochemical solar energy conversion system has to be based on visible light absorption. 

The potential of purple nonsulfur bacteria for application as biological element in systems of light energy conversion into H2 energy is discussed. 

At present, we do not have novel photobioreactors and their creation is questionable at present. So, application of alternative systems incorporating purple bacteria for the light energy conversion is problem of great importance. 

CaTiOs semiconductors (Fig. 3) [138]. The light energy conversion efficiencies were estimated to be 0.001-0.016% in these systems. 

In the case of CdSe/polysulfide system, solution activity, conductivity, efficiency of the photoanode (fill factor), charge-transfer kinetics at the interface, and the stability of the photoelectrode are known to exhibit improvements in the trend Li > Na > K > Cs > for alkali polysulfide electrolyte. This trend is explained in terms of the secondary cation effect on electrochemical anion oxidation in concentrated aqueous polysulfide electrolytes [39]. In the case of Cd(Se,Te)/polysulfide system, the efficiency of light energy conversion is improved by using a polysulfide electrolyte without added hydroxide because of the combined effect of increasing the solution transparency, relative increase of 4 , and decrease in 83 in solution. For the same photoelectrode-electrolyte system, an optimum photoeffect was observed for a solution containing a sulfur-sulfide ratio of 1.5 2.1 with 1 2 molal... 

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