Solar energy, conversion

In this chapter, we will focus on solar energy and its conversion to other forms of energy. Solar energy is renewable and as an immaterial source, radiation, its emission is equally immaterial. In nature, it induces closed material cycles with overall outputs that closely resemble those of industry mechanical, chemical, and electrical energy, and chemical products. These properties (i.e., renewability, no emissions, and closed material cycles) make solar energy an excellent candidate for energy supply to a sustainable society in the making. 

After the introduction, we will briefly discuss the main characteristics of solar radiation. Consistent with the scientific principles on which this book is founded, a rigorous thermodynamic analysis will then follow of the creation of wind energy, of photothermal and photovoltaic energy conversion, and of photosynthesis. Most of this chapter has been based on the monograph Thermodynamics of Solar Energy Conversion by De Vos [1]. 

Photosynthesis creates a global annual CO2 flux of 1.24 x 10 tonnes per year and an annual O2 flux of 10 tonnes per year. In its present technologically unenhanced form, photosynthesis already traps around 4000 EJ per year of solar energy globally in the form of biomass. The global biomass energy potential for 

Semi-conducting layer of Electrolyte (NR4+I7I2) fine Ti02 particles, coated. . . with monolayer of dye 

A dye which shows particular promise for this application is the octahedral ruthenium(n) complex of 2,2 -bipyridyl (234). While this type of system appears to offer considerable potential as a means of solar energy conversion, the efficiency of the technology, at its current state of development, is significantly lower than that of traditional silicon photocells. 

---

A. J. Nozik, in Photovoltaic and Photoelectrochemical Solar Energy Conversion, F. Cardon, W. P. Gomes, and W. Dekeyser, eds.. Plenum, New York, 1981. 

There is a large volume of contemporary literature dealing with the structure and chemical properties of species adsorbed at the solid-solution interface, making use of various spectroscopic and laser excitation techniques. Much of it is phenomenologically oriented and does not contribute in any clear way to the surface chemistry of the system included are many studies aimed at the eventual achievement of solar energy conversion. What follows here is a summary of a small fraction of this literature, consisting of references which are representative and which also yield some specific information about the adsorbed state. 

Much use has been made of micellar systems in the study of photophysical processes, such as in excited-state quenching by energy transfer or electron transfer (see Refs. 214-218 for examples). In the latter case, ions are involved, and their selective exclusion from the Stem and electrical double layer of charged micelles (see Ref. 219) can have dramatic effects, and ones of potential imfKntance in solar energy conversion systems. 

Anderson, J. M., and Andersson, B., 1988. The dynamic photosynthetic membrane and regulation of solar energy conversion. Trends in Biochemical Sciences 13 351 — 355. 

Kaneko,M. and Yamada, A. Solar Energy Conversion by Functional Polymers. Vol. 55, pp. 1—48. 

Photophysics, photochemistry and solar energy conversion with Ru(bipy)32+ and its analogues. K. Kalyanasundaram, Coord. Chem. Rev., 1982, 46, 159-244 (360). 

Molecular photocatalytic systems for solar energy conversion catalysts for the evolution of hydrogen and oxygen from water. K. I. Zamaraev and V. N. Parman, Russ. Chem. Rev. (Engl. Transl.), 1983,52,817-836(114). 

Newman, J. Photoelectrochemical Devices for Solar Energy Conversion 18... 

Today microemulsions are used in catalysis, preparation of submicron particles, solar energy conversion, extraction of minerals and protein, detergency and lubrication [58]. Most studies in the field of basic research have dealt with the physical chemistry of the systems themselves and only recently have microemulsions been used as a reaction medium in organic synthesis. The reactions investigated to date include nucleophilic substitution and additions [59], oxidations [59-61], alkylation [62], synthesis of trialkylamines [63], coupling of aryl halides [64], nitration of phenols [65], photoamidation of fluoroolefins [66] and some Diels-Alder reactions. 

As an example, GulnSe2 is a known low band-gap material (1.0 eV) that shows promise for use in solar energy conversion [106]. We can imagine preparing rare-earth based materials using the formulation shown in Table 14.5. 

Loferski JL (1956) Theoretical considerations governing the choice of the optimum semiconductor for photovoltaic solar energy conversion. J Appl Phys 27 777-784... 

Trigonal, metallic selenium has been investigated as photoelectrode for solar energy conversion, due to its semiconducting properties. The photoelectrochemistry of the element has been studied in some detail by Gissler [35], A photodecomposition reaction of Se into hydrogen selenide was observed in acidic solutions. Only redox couples with a relatively anodic standard potential could prevent dissolution of Se crystal. 

Gruszecki T, Holmstrdm B (1993) Preparation of thin films of polycrystaUine CdSe for solar energy conversion 1. A literature survey. Sol Energy Mater Sol Cells 31 227-234... 

---