Concentrating collectors

Three main types of concentrating collectors have evolved for use in solar thermal systems low concentration paraboHc troughs, high concentration parabohc dishes, and central receivers (Fig. 3). Higher concentration produces higher temperatures in a working fluid and makes electrical generation more efficient. 

Marion, W., and Wilcox, S. (1994). Solar Radiation Data Manual for Elat-Plate and Concentrating Collectors. Golden, CO National Renewable Energy Laboratory . National Renewable energy Laboratoiy (NREL) Home Page. National Renewable Energy Laboratoiy. August 9, 2000 < http /Avww.nrel.gov/>. 

A solar Rankine heat engine with one concentrated collector used as the boiler is proposed. Saturated water at 1 kg/sec enters the pump of the... 

Fig. 2. Average monthly H2 production and demand (one-million FCVs). Average fuel consumption is from U.S. Federal Highway Administration data 16 and H2 supply is estimated from average monthly insolation values for six locations in the southwest U.S. with data from NREL s Solar Radiation Data Manual for Flat-Plate and Concentrating Collectors.17 Correlation between H2 supply and H2 demand is 0.61.

W. Marion and S. Wilcox, Solar Radiation Data Manual for Flat-Plate and Concentrating Collectors, Manual Produced by the National Renewable Energy Laboratory s Analytic Studies Division. Contract No. NREL/TP-463-5607, DE93018229, April, 1994. 

Concentrating collectors are only able to use a limited fraction of fhe diffuse solar radiation. This utilizable fraction can be estimated as the inverse of the concentration ratio of fhe collecfor (1/Cr) (Rabl, 1985). Because of this, parabolic trough photocatalytic reactors, which have a concentration ratio around 15 or higher, miss practically all diffuse radiation. This amounts to losing around half of fhe available UV solar irradiance. 

It is important to note that the accumulated available energy does not take into account the actual energy collected by each reactor. In fact, the actual collected energy is a function of concentration ratio, as concentrating collectors are able to capture only a 1 /Cr fraction of the diffuse radiation. In order to reflect this, another quantity can be defined called the accumulated collected energy... 

There are many technological schemes for petroleum preparation. However, technical and economic considerations determine which scheme is used and the location of installation. It is known that the lowest capital investment and operational costs for petroleum preparation are for installations in locations of the greatest petroleum concentration (collector stations, commodity parks, and head offices). 

Here, we consider a concentrating collector as shown in Fig. 2.45(a). With proper interpretation, however, the formulation given below may be applied to flat-plate as well as concentrating collectors. 

A fluid flows steadily with velocity V through a thick wall pipe of length l (Fig. 2P-13). The inlet temperature of the pipe is To. The effect of axial conduction is negligible. Under steady conditions, find (a) the outlet temperature of the fluid, (b) the axial variation in the inside and outside temperatures of the pipe wall, (c) Now, let the pipe be at the focus of a concentrating collector so that it receives uniform peripheral heat flux q" from the sun. Resolve (a) and (b). 

Interestingly, the flotation often decreases at high concentration of the collector. At much higher concentrations, collectors normally associate to form micelles in solutions. The activity of collector monomer does not increase appreciably above the critical micelle concentration (CMC) in any case, the concentration of interest in the case of flotation is usually in the pre-micellar region. Adsorption in the micellar region is of interest in other areas such as enhanced oil recovery. Detailed discussions are given in the next chapter. 

Solar heating requires concentrating collectors (e.g., parabolic) to produce the likely process temperatures and overall performance needed. It also limits operation to daytime hours and sunny days or requires a way of storing energy at high temperatures. 

Fig.7.6 FI manifold and main operation sequences for on-line coprecipitation ETAAS determination of Cd with the Fe(U)-HMDTC/IBMK system, a, delivery of stored concentrate (from previous sample) b, precipitation of sample with HMA-HMDTC c, washing of precipitate with aqueous solution of HMA-HMDTC and d, precipitate dissolution by IBMK. Pi, P2, peristaltic pumps KR, knotted reactor, B, solvent displacement bottle V, 4 5 channel injector valve C, PTFE concentrate collector tube (60 /xl) GF, graphite furnace and W, waste [23].

Compound Parabaloid Collector - A form of solar concentrating collector that does not track the sun. 

The superiority of acrylic polymers used for concentrating collector mirrors or lenses has been underlined [29]. Studies on reactivity of different polymers used as protective coatings or in film form for solar mirrors have established PMMA(3M)/Al/adhesive to be the most durable of the polymer/ mirror systems. 

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. 

In concentrating collectors, the effect of the mean collector operating temperature on the collector efficiency is much less pronounced as in non-concentrating systems. However, it... 

Concentrating Collectors. Hybrid solar lighting systems use sun-tracking focusing mirrors and optical fiber transmission to provide interior lighting. Typically half of the incident sunlight can be transmitted to rooms, where it replaces or supplements conventional lighting. 

Roy AS (1979) Concentrating Collectors, Solar Energy Conversion. An Introductory Course, Dixon AE and Leslie JD (eds) pp 185- 252. Oxford Pergamon. 

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