Design requirements, solar energy collectors

This chapter reviews some of the main topics involved in the design and modeling of solar photocatalytic reactors, with particular emphasis on the authors research experience. Solar photons are source of energy that initiates photocatalytic degradation. Thus, proper consideration of radiative processes is key to address this subject. The determination of the directional and spectral characteristics of solar UV radiation, the interaction of the catalyst with radiation inside reaction spaces, the optical design of solar collectors, and the optical properties of the materials involved are all subjects where these concepts are necessary. Therefore, developments in this area should be solidly grounded on the fields of solar collector optics and radiative transfer, besides the more traditional chemical engineering aspects involved. This requires a multidisciplinary approach. 

FIGURE 12 (a) Details of the actual profile shape and collector design for the integrated stationary evacuated concentrator (ISEC) tube, which has achieved a thermal efficiency of 50% at 200°C. (b) Ray trace diagram showing how essentially all the solar energy incident within 35° is directed onto the absorber tube. Because the reflector cannot physically touch the absorber, as required for an ideal concentrator, a small fraction is lost in the gap between the reflectors and the absorber. 

Considering an outline design as suggested by Little (2011) (see Section 19.4.1), the collected electrical energy from solar collectors supported by satellite no. 1 at geostationary orbit would be beamed to Earth by laser onto satellite no. 2 positioned some 20 kilometres above the Earth. Satellite no. 2 would support the equipment to transform the laser to microwaves which would be beamed to a ground receiver. Ideally both satellites 1 and 2 would be fabricated from a polymer/libre composite skeletal space structure to support the collectors and equipment. Figure 19.9 illustrates the components that would be required for the SBSP system. 

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