Solar energy photosynthesis

Photosynthesis is the reverse of reaction (30.1) the formation of carbohydrates and oxygen from water and carbon dioxide with solar energy. Photosynthesis occurs in the chloroplasts contained in the cells of green plants. The chloroplasts hold two types of photosynthetic systems, which are called PSl and PS 11. These systems... 

In natural waters organisms and their abiotic environment are interrelated and interact upon each other. Such ecological systems are never in equilibrium because of the continuous input of solar energy (photosynthesis) necessary to maintain life. Free energy concepts can only describe the thermodynamically stable state and characterize the direction and extent of processes that are approaching equilibrium. Discrepancies between predicted equilibrium calculations and the available data of the real systems give valuable insight into those cases where chemical reactions are not understood sufficiently, where nonequilibrium conditions prevail, or where the analytical data are not sufficiently accurate or specific. Such discrepancies thus provide an incentive for future research and the development of more refined models. 

The capture of solar energy as fixed carbon in biomass via photosynthesis is the initial step in the growth of biomass. It is depicted by the equation... 

The maximum efficiency with which photosynthesis can occur has been estimated by several methods. The upper limit has been projected to range from about 8 to 15%, depending on the assumptions made ie, the maximum amount of solar energy trapped as chemical energy in the biomass is 8 to 15% of the energy of the incident solar radiation. The rationale in support of this efficiency limitation helps to point out some aspects of biomass production as they relate to energy appHcations. 

There are costs associated with loss of visibility and solar energy. These include increased need for artificial illumination and heating delays, disruptions, and accidents involving air, water, and land traffic vegetation growth reduction associated with reduced photosynthesis and commercial losses associated with the decreased attractiveness of a dingy communiW... 

Plants store solar energy by photosynthesis. During photosynthesis, carbon dioxide (COj) and water (H2O) in the presence of light are converted into glucose (C(,H 20(,) by the following chemical equation ... 

The food a person eats is a personal energy store hanking on photosynthesis. In photosynthesis, gaseous carbon dioxide, liquid water, and solar energy interact to produce solid carbohydrates, such as sugar and starch, and gaseous ox gen. 

Energy streams to Earth from the sun by electromagnetic waves. Photosynthesis depends on solar energy, and humans and animals rely on photosynthesis for food. In this sense, solar energy is not a lux-uiy, it is essential. 

The energy that powers terrestrial processes is derived primarily from the sun and from the Earth s internal heat production (mostly radioactive decay). Solar energy drives atmospheric motions, ocean circulation (tidal energy is minor), the hydrologic cycle, and photosynthesis. The Earth s internal heat drives convection that is largely manifested at the Earth s surface by the characteristic deformation and volcanism associated with plate tectonics, and by the hotspot volcanism associated with rising plumes of especially hot mantle material. 

Photocatalysis is a fundamental feature of life processes on our planet [1] (it provides photosynthesis in plants and bacteria) and of the chemistry of its atmosphere [2]. Work is under way to develop photocatalytic technologies for abatement of environmental problems [3,4]. Photocatalysis is anticipated to become in the coming years important also for selective organic synthesis [4]. In a more distant future thermal catalytic processes induced by heating with solcir radiation, together with photocatalytic processes may become important for environmentally friendly technologies of solar energy utilization [5-9]. 

Approaches to the fundamental need to shift from fossil to renewable feedstocks for chemicals production wiU range from modifications to, and developments of, traditional chemical, engineering and biotechnological methods (that maybe implemented on a relatively short timescale, say, 10-15 years) to much more radical processes (such as direct capture of solar energy, through artificial photosynthesis), requiring longer time to implement (say 15-30 years). 

Chemical models of photosynthesis have been used to investigate two types of reactions photosynthesis and photocatalysis. In photosynthetic processes the standard Gibbs free energy of the reaction is positive, and solar energy is utilized to perform work. In photocatalytic processes the free energy is negative and solar energy is used to overcome the activation barrier. 

This is the present state in the development of chemical systems for artificial photosynthesis. For solar energy conversion and... 

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