ABSTRACT
A solar energy industrial or agricultural process heat system comprises conceptually a solar collector, intermediate heat storage and a means of conveying the collected heat between these and to the application. The solar collector is usually selected in terms of outlet temperature, as illustrated in Figure 9.1, matched to the process heat requirement. Where, and/or at times when, the collector outlet temperature is less than that at the process inlet, additional heating is provided. Many solar energy industrial and agricultural process applications do not involve energy storage because either the diurnal heat load is well-matched to the available insolation or auxiliary heating may be provided more readily. In solar process heat applications, where present, sensible energy storage has tended to be both low temperature and low energy density leading to large size and high initial cost. Only occasionally have latent or chemical energy storage systems been considered. For processes that continue during the night or during periods of insufficient insolation, providing auxiliary heating has been frequently found to be more viable economically than providing sufficient energy storage to enable solar fractions close to unity to be achieved. An exception is the concomitant solar energy collection and storage provided by a non-convecting solar pond (Norton, 1992). Auxiliary heating is also required where the magnitude and duration of the direct component are insufficient to render feasible a concentrating solar energy collector providing directly desired higher application temperatures. The availability of direct insolation also delineates the geographic locations for applications predicated on the use of concentrated solar energy. Non-imaging compound parabolic trough medium-temperature solar collectors can use the diffuse sunlight found in humid climates. In general vacuum tube collectors are used in medium temperature solar process heat systems. <italic>Principal solar energy collector types.</italic> https://s3-euw1-ap-pe-df-pch-content-public-p.s3.eu-west-1.amazonaws.com/9781315074412/feb3d8c8-9146-4af7-a5ce-b80347ae78a3/content/fig00588_B.tif" xmlns:xlink="https://www.w3.org/1999/xlink"/>
