Collectors flat plate

The interfaces of importance in SECS are the solid/solid (S/S), solid/gas (S/G), and solid/ liquid (S/L) (4). The area-intensive nature of SECS components was established in the previous section. The major problem is collecting solar energy at a cost that is competitive with other energy forms. Thus, low initial cost is required for the materials, support structures, and production processes in the SECS of interest in Fig. 1 (6). This requires, for example, using thin films in mirrors, in photovoltaic systems, for antireflection coatings on windows, for passive collection, etc. in addition, these films must be made from inexpensive, durable, and easily processed materials (5). Inexpensive long-life materials in flat-plate collectors and durable, stable absorber coatings are also necessary. 

For solar thermal and photovoltaic systems using flat plate collectors, energy collection is optimized for collectors tilted south (in the northern hemisphere) at approximately the latitude of the site. 

Standard test conditions prescribed in photovoltaic standards require a total hemispherical irradiance on flat plate collectors of 1000 Wm 2 (a value that can obtained on a clear day around noon). 

The most common solar collector is the glass-covered flat plate type. Others include concentrating trough and tube-over-reflector collectors, and parabolic collectors. A flat plate collector uses a flat black absorber plate in a container box. Insulation behind the absorber plate and on the sides of the box reduce heat loss. The glazing may be flat glass, translucent fiberglass or clear plastic, on the sun side of the collector, 1 to 2 inches above the absorber. 

K. G. T. Hollands and J. L. Wright, Heat Loss Coefficients and Effective Products for Flat-Plate Collectors With Diathermanous Covers, Solar Energy (30/3) 211-216,1983. 

Hottel, H. C., Whillier, A., Transactions of Conference on Use of Solar Energy, Scientific Basis, Vol. II, Thermal Processes, Part 1, Section A, Flat-Plate Collectors, Evaluation of Flat-Plate Solar-Collector Performance, Tucson, Ariz., 78 (Oct. 31— Nov. 1, 1955). 

Polymers have many potential applications In solar technologies that can help achieve total system cost-effectiveness. For this potential to be realized, three major parameters must be optimized cost, performance, and durability. Optimization must be achieved despite operational stresses, some of which are unique to solar technologies. This paper Identifies performance of optical elements as critical to solar system performance and summarizes the status of several optical elements flat-plate collector glazings, mirror glazings, dome enclosures, photovoltaic encapsulation, luminescent solar concentrators, and Fresnel lenses. Research and development efforts are needed to realize the full potential of polymers to reduce life-cycle solar energy conversion costs. 

Polymeric materials are used In all solar technologies. In addition to such conventional applications as adhesives, coatings, moisture barriers, electrical and thermal Insulation, and structural members, polymers are used as optical components In solar systems. Mirrors on parabolic troughs are made up of metallized fluoropolymers and acrylics. Commercial flat-plate collectors are glazed with fluoropolymers and ultraviolet-stabilized polyester/ glass fiber composites. Photovoltaic (PV) cell arrays are encap-... 

Imaginative applications of polymers to fenestration can also be used for flat-plate collectors. A transparent, coated polymeric glazing which transmits the solar spectrijm but returns the Infrared radiation effectively Increases the Insulation provided by the glazing, because the Infrared radiation generated Inside the structure Is retained. A polymeric film which changes from transparent to opaque when heated above a transition temperature acts as an automatic window shade which could help control stagnation temperatures [9]. 

Wilhelm, W. G. "Low Cost, High Performance Solar Flat Plate Collectors for Applications In Northern Latitudes, BNL 30633, September 1981. 

Many current solar hellostat and flat plate collector designs which have been field tested show a vulnerability to long-term outdoor weathering ( ) Therefore, the purpose of this investigation was to evaluate potential protective polymeric materials,... 

The simplest types of solar dryers (e.g., cabinet dryers, tent dryers, and certain chimney shelf dryers) (see Eigures 14.1, 14.2, and 14.4), do not employ a separate absorber the role of the absorber is played by the irradiated material itself The majority of high-performance solar dryers are equipped with flat-plate collectors [205]. 

FIGURE 14.17 Setup of flat-plate collectors (a) air (b) liquid as working medium (1, covering 2, absorber 3, heat insulation). 

FIGURE 14.18 Scheme of flat-plate collectors without covering, with air as working medium (a) corrugated plate (b) trapezoid plate (c) triangle waved plate (as absorber). 

FIGURE 14.19 Scheme of air-type flat-plate collectors with covering (a) plane absorber, flow over absorber (b) plane absorber, flow under absorber (c) absorber with corrugated surface (d) finned absorber (in c and d, flow is under the absorber, perpendicular to the plane of the paper) (e) plane absorber, flow over and under absorber (two way). (From Vijeysundera, N.E. et al.. Solar Energy, 28, 363, 1982.)... 

FIGURE 14.20 Air-type flat-plate collector constructed with divided surface absorber (a) stepwise divided absorber made of overlapped plates (b) perforated double-plane absorber (c) matrix-type absorber. 

Flat-plate collectors with finned tube absorber (shown in Figure 14.22b) can be built of extruded elements. This is proposed for integrated or panel collectors. The absorber elements perpendicular to the plane of the paper can be ordered... 

FIGURE 14.22 Some designs of liquid-type collectors (a) absorber plate made of stamped sheets (b) collector with extended finned tube absorber elements (c) through (f) different tube-sheet, flat-plate collectors. 

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