Material and Component SpecificationsNon Imaging Concentrator

Prepared by IT Power India

Under UNDP-GEF market development & promotion of solar concentrator based process

heat application in IndiaMinistry of New and Renewable Energy

Government of India December 2015

Preface

This booklet outlines the material and component specifications of Non Imaging Concentrators for process heat applications. The purpose of this booklet is to layout the material and component specifications of key components of the Non Imaging Concentrator system so as to serve as a reference document to maintain quality in the field by manufacturers supplying and installing the system.

The booklet is intended to serve as a guide for stakeholders interested in Con-centrated Solar Thermal (CST) system based on this technology for applications in process heat for industry and help them set up a durable system which meets the necessary safety and quality standards. It is one of a series of such booklets produced to cover the field of commercially available CST systems marketed for process heat applications in India.

The specifications for key components and subcomponents of the Non Imag-ing Concentrator system and their relevant parameters are outlined in an easy to understand tabular format. Wherever applicable, images of the components and schematic diagrams have also been presented for easy identification of the components.

The booklet has been compiled with technical inputs from the developers and manufacturers of this technology. Inputs and suggestions of experts in the do-main of concentrated solar thermal systems and users have also been taken in the compilation of this booklet.

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Background

India has a very good potential of solar energy, with average solar irradiation be-ing around 4-7 kWh/m2/day. This abundant solar radiation can be used to meet the demand of low to medium process heat as required by various industries and institutions. Concentration of solar radiation to produce the temperature in the range of 100 to 450C or more is called concentrated solar thermal (CST) technol-ogy. This technology offers sizeable potential across diverse range of industries and commercial establishments in India.

There are six CST technologies commercially available in India, namely, Fixed focus automatically tracked elliptical dish (Scheffler) Dual axis tracked paraboloid dish Fresnel reflector based dish (ARUN dish) Single axis tracked parabolic trough concentrator Non-imaging concentrators Linear Fresnel reflector

About Non Imaging Concentrator TechnologyNon Imaging Concentrator (NIC) is similar to flat plate collector with the excep-tion of a compound parabolic collector (CPC) fixed at a tilted base.

Underlying principle The CPC reflector mainly consists of two parabolic reflectors each with different focal points and this is the reason it is named as a non-imaging concentrator be-cause no image of the source is formed at the focal point. These parabolas con-centrate the incoming radiation onto the receiver tube which is placed between the focus of two parabolas. The acceptance angle of reflector is the maximum angle through which incoming radiation can enter the collector. The receiver tube is specially coated and enclosed within a glass tube to reduce convection losses. The space between the absorber and glass tube may be evacuated. Non-imaging concentrator does not require any tracking system however, the module has to be oriented properly in order to increase its output energy. The NIC panel is generally mounted in the East-West direction with the panel facing south in-clined from the ground at an inclination angle of (Latitude Angle + 10).

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Key components of Non Imaging ConcentratorKey components of a Non Imaging Concentrator based system can be classified on the basis of their individual functions:

NON IMAGING CONCENTRATOR Collector Receiver Module

BALANCE OF SYSTEM Piping Instrumentation and Safety Mechanism Storage System (optional)

Key design variantsNon Imaging Concentrator is currently available in two primary designs, as given below [In brackets: Collector Size]

End-use applicationNon Imaging Concentrator is used for the low to medium process heat applica-tion. It can attain a maximum temperature up to 120C as per requirement in industries, commercial & residential complexes, religious places, etc.

Some of the typical application areas of a Non Imaging Concentrator are namely; Hot Water for Bathing Component Washing Community cooking Solar-assisted comfort cooling Laundry Effluent Treatment

SolPac NI30 (3.4 m2) by Thermax NIC (20 m2) by Bergen Solar

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The configuration of an industrial process heat solar system depends on the spe-cific application. It may consist of one or more number of Non Imaging Concen-trators in a system. Non Imaging Concentrators have been installed in various thermal applications across industries including vehicle manufacturing for wash-ing of automobile parts, chemical plants, etc. There are 2 key manufacturers of this technology and around 6 case specific examples of Non Imaging Concentra-tor installed across India. The list is given as an Annexure.

Development of the Non Imaging Concentrator in the country requires compo-nent and material standards to be followed for maintaining the quality in the field by the manufacturer and thereby assurance of the quality by the end-user.The following section covers detailed specifications of various components and materials of a Non Imaging Concentrator.

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Schematic Diagram of CST based system with Non Imaging Concentrator (Courtesy: CSH India)

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Material and Component Specifications

CollectorThe Non-imaging concentrator uses a compound parabolic concentrator (CPC) reflector to capture the incident sun rays. The metal reflector of high reflectivity is generally used. The acceptance angle of the reflector determines the amount of sunlight that will enter and get reflected to the receiver placed at its focus.

SpecificationsReflector

Parameter Specification

Type Weather proof, scratch resistant Compound Para-bolic Concentrator

Material Pure Aluminium Sheet / Alloy Aluminium sheet

Shape Cylindrical with parabolic cross section

NON-IMAGING CONCENTRATOR

CPC Reflector

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Parameter Specification

Thickness 0.3 0.8 mm

Reflective Coating Aluminum with 7 layer coatings for weather proof-ing and reflectivity.

Reflectivity At least 90%

Protective Coating Anodizing / Epoxy, Polyester (PE), Polyurethane (PU), Fluorocarbon coating / Lacquer coating

Durability Minimum 10 years

ReceiverThe receiver of a Non-imaging concentrator is an evacuated type linear tube placed at the focus of CPC reflector. It transfers the heat reflected by CPC collec-tor to the heat transfer fluid flowing through the tube

Exploded View of Receiver (Source: Andy Schroder)

Receiver CPC collector Schematic (Source: Andy Schroder)

Receiver

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International Organization for Standardization1

Specifications

Receiver

Sub components Specification

Absorber

Design U shaped tubing attached to metal fins. This unit is con-tained in an internal glass tubeMaterialU Tube Copper, Stainless steel.Metal Fins Aluminium sheetGlass Borosilicate Glass 3.3 conforming to ISO1 3585

Absorber Coating

Type & MaterialOuter surface of Internal Glass tube is selectively coated with Aluminium Nitride based proprietary materialAbsorptivityAt least 92 % to 95% at AM2 1.5

Outer Glass Cover

DesignGlass tube with vacuum between Internal and outer glass tubeMaterialBorosilicate Glass 3.3 conforming to ISO 3585TransmittanceAt least 90 to 96 % at AM 1.5Outer Diameter47-70 mmThickness 1.6 2.0 mm

Absorber - Glass fixing

U shaped copper tube is connected to the header pipe with prior arrangement on header to fix the tubing.

Internal glass tube is closed at the base and seated in a steel strut. Other end of internal glass tube is thermally sealed with one end of outer glass tube.

The other end of outer glass tube is thermally sealed after ensuring the desired vacuum

Air Mass26

ModuleCPC reflector and receiver tube assembly are placed above the module with a proper fixing mechanism. A module can have a number of receiver tubes as per design with individual CPC reflector. Module can be connected in series or paral-lel to other module. Series connection is used for high temperature requirement whereas parallel for high flow rate.

The basic framework of the stand is a steel structure. The structure is designed to withstand wind speed under an operating condition as per the prevalent struc-tural design code. The overall system rests on a civil foundation.

Specifications

Module

Parameter Specification

Design & MaterialBack cover made of Aluminium sheet fixed on Aluminium or steel Frame

Fixing of Receivers

One end of receiver tube is fixed on to the module with the help of brackets and standard fasteners

Fixing of Reflectors

Reflectors are glued or attached to the frame by standard glue material

Back Sheet Frame Module Stand

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Module Stand

Sub components Specification

Structural Support

Foundation

DesignStructural steel support made of standard angles and sec-tions which are further fastened to the civil structure

MaterialCarbon Steel

Protection from corrosionCathode Electrode Deposition painting processStrength Designed as per IS3 875 and allied/applied codes

DurabilityMinimum 10 years