Parabolic trough reflector

Adhesives play a critical role in the concepts developed for parabolic trough reflector modules. The need to develop adhesives that are compatible with silvered glass mirrors, that serve as structural members and can maintain these properties over 20 years has lead to a program to define appropriate candidates. 

Adhesives (128) play an important role in the construction of a solar parabolic trough reflector. The adhesives should be compatible with silvered glass mirrors and should be able to carry structural loads. Moreover the adhesives should be durable for at least twenty years without losing their properties. Adhesives screened for solar collectors were epoxies, urethanes, and acrylics. Three types of stress conditions were identified as the most likely causes of failure in the trough modules ... 

The resultant treatability data was used to size a 5-SCFM pilot-scale system (Figure 21.4.2) also built by Industrial Solar Technologies. This system consists of a parabolic trough reflector to focus incident sunlight onto a receiver tube containing the catalyst. The trough has a 91 cm aperture width and is 243 cm long. The reflective surface is covered... 

In this design, parabolic mirror reflectors (troughs) are used to track the trajectory of the Sun and to concentrate the sunlight onto absorber tubes that are located at the focal line of the parabolic mirrors. Inside the absorber tubes, heat-resistant oil is circulated. This heat-transfer fluid serves to transport the collected heat into boilers that generate steam to drive the turbine generators. 

As discussed previously, several solar photoreactor geometries can be reduced to cylindrical glass tubes externally illuminated by different types of reflectors, like parabolic troughs, CPC, V-grooves, or without reflector, directly illuminated by the sun. In this section the general solution of the PI approximation for this t)q5e of photo reactors is reported. This general solution is applicable to any particular reactor if the flux distribution impinging on the wall of the tubular reaction space is known. 

The aim of the solar thermal collector development is to improve and optimize them for the temperature level from 80 °C to 250 °C. There are different approaches like double-glazed flat plate collectors with anti-reflection coated glazing, stationary compound parabolic concentrator (CPC) collectors, evacuated tube collectors, vacuum flat plate collectors, small parabolic trough collectors, linear concentrating Fresnel collectors and a concentrating collector with a stationary reflector. 

FIGURE 13 Comparative peak performance for a tracking parabolic trough, an ISEC, contemporary (external reflector) evacuated CPCs (triangles) and flat plates. The ISEC s superior performance up to temperatures above 200°C, achieved with no moving parts, makes it an extremely flexible solar thermal collector. 

Compound parabolic collectors (CPCs) belong to the most promising photocatalytic solar reactors which combine the advantages of parabolic trough concentrator and non-concentrating system [178]. CPCs are low-concentration static collectors with reflective surface and can be designed for any given reactor shape (see Fig. 7.3a) [182]. The CPC reflectors are usually made from polished aluminum... 

Trough systems currently account for more than 90 percent of the world s solar electric capacity. They nse parabolic reflectors in long trough configurations to focus and concentrate sunlight (up to one hundred times) on oil-filled glass tubes placed along the... 

Typically, large-scale solar concentrators utilize parabolic reflectors in the form of trough, tower, or dish systems. These solar concentrators are characterized in terms of their mean flux concentration ratio Cr over an area Sa at the receiving focal plane as follows ... 

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. 

FIGURE 4 Cross-sectional profiles of ideal trough concentrators generalized for absorbers of different shapes. In practice the reflectors are usually truncated to about half their full height to save reflector material with only negligible loss of concentration. Such designs have come to be called compound parabolic concept raters, or CPCs. 

Example Solar concentrating technologies such as parabolic dish, trough, and Scheffler reflectors can provide process heat for commercial and industrial applications. However, the reflectors need to retain their surface properties and not corrode. 

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