Comments, if any, may please be made in the format as given overleaf and ed to the undersigned at the above address.

Transcription

1 DRAFT STANDARD UNDER WIDE CIRCULATION DOCUMENT DESPATCH ADVICE Ref: MED 04/T-22,23 & 24 Date: Renewable Energy Sources Sectional Committee, MED 04 TO: a) The interested members of Mechanical Engineering Division Council, MEDC b) All members of Renewable Energy Sources Sectional Committee, MED 04, Solar Thermal Subcommittee, MED 04:1 c) All others interested Dear Sir(s), Please find enclosed the following document: Doc. No. TITLE MED 04 (1438) wc Draft Indian Standard All Glass Evacuated Solar Collector Tubes -Specification MED 04 (1439) wc Draft Indian standard storage water tank for all glass evacuated tube solar collector - Specification MED 04 (1440) wc Draft Indian standard all glass evacuated tubes solar water heating system Kindly examine the Draft standard and forward your views stating any difficulties which you are likely to experience in your business or profession, if this is finally adopted. Last date for receipt of comments: Comments, if any, may please be made in the format as given overleaf and ed to the undersigned at the above address. In case no comments are received or comments received are of editorial nature, you will kindly permit us to presume your approval for the above document as finalized. However, in case of comments of technical in nature are received then it may be finalized either in consultation with the Chairman, Sectional Committee or referred to the Sectional committee for further necessary action if so desired by the Chairman, Sectional Committee. The document is also hosted on BIS website Thanking you, Yours faithfully (T.V Singh) Encl: As above Sc F & Head (MED), ROOM NO: 203 MANAK BHAVAN 9 BAHADUR SHAH ZAFAR MARG NEW DELHI TELEFAX med@bis.org.in

2 Doc : MED 04 (1438)wc Draft Indian Standard All Glass Evacuated Solar Collector Tubes - Specification Not to be reproduced without the permission of BIS or used as a STANDARD Last date for receipt of comments is: 15 July SCOPE This standard specifies requirements of all glass evacuated solar collector tubes intended for low temperature non concentrating type solar collector. 2 REFERENCES The standards listed below contain provisions which, through reference in this text constitute provisions of this standard. At the time of publication, the editions were valid. All standards are subject to revision and parties to agreements based on this standard are encouraged to investigate the possibility of applying the most recent editions of the standards indicated below: IS No Title IS/ISO 9488:1999 Solar Energy - Vocabulary ISO 3585:1998 Borosilicate glass TERMINOLOGY In addition to the terms and definitions given in is/iso 9488, the following shall apply for this standard: 3.1 Absorber of all-glass evacuated solar collector tube- Inner glass tube with solar selective absorbing coating on its outer surface that absorbs solar radiation and converts it into thermal energy. 3.2 Angle of incidence - The angle between the direct solar irradiation and the normal to the aperture plane. 3.3 Average heat loss coefficient of an all glass evacuated solar collector tube - Thermal flow lost through the absorber unit surface area under the condition of no solar irradiance for every 1 C difference between the average temperature of the hot water filling up the all-glass evacuated solar collector tube and the average ambient temperature. 3.4 Bubble (stone) - Solid impurity contained in the glass body. 3.5 Diffuse flat plate reflector- Flat plate mainly with diffuse reflection, which is installed below at a certain distance from the all glass evacuated solar collector tube and used for increasing the solar radiation collected by the all-glass evacuated solar collector tube. 3.6 Knot - Vitreous body in glass that varies from the main component of glass. 3.7 Pyranometer - A radiometer used to measure the total solar radiation (direct, diffuse, and reflected) incident on a surface per unit time per unit area.

3 Doc : MED 04 (1438)wc 3.8 Reflector or Reflective Surface - A surface intended for the primary function of reflecting radiant energy. 3.9 Solar Irradiance - Irradiance is the rate of solar radiation received by a unit surface area in unit time in W/m Solar selective absorbing coating (surface) - Coating with high solar absorbing ratio and low emitting ratio Stagnation temperature - Maximum temperature of air within the all-glass evacuated solar collector tube under quasi-steady-state at specified solar irradiance when there is only air inside the all-glass evacuated solar collector tube 3.12 Stagnation parameter of an all glass evacuated solar collector tube - Ratio of the difference between stagnation temperature and ambient temperature and the solar irradiance Vacuum jacket in all glass evacuated solar collector tube - Jacket between the cover glass tube and inner glass tube of the all-glass evacuated solar collector tube, where air pressure is sufficiently low, thermal conduction and convection of air can be ignored Vacuum quality Vacuum performance in the evacuated tube which is expressed by disappearance ratio in axial length of the getter mirror after interior of an evacuated tube is heated. 4 DESIGN 4.1 STRUCTURE OF ALL GLASS EVACUATED SOLAR COLLECTOR TUBE The all glass evacuated solar collector tube shall comprise of the inner glass tube with solar selective absorbing coating on its outer surface and coaxial cover glass tube. The one end of the inner glass tube shall be closed at base and seated in a steel strut. The other end of the inner glass tube shall be thermally sealed with the other end of the cover glass tube. The space between the inner tube and outer cover tube shall be vacuumised before thermal sealing of the other end of cover tube. Fig. 1 Structure of all-glass evacuated solar collector tube Key 1 Inner glass tube; 2 Solar selective absorbing coating; 3 Vacuum jacket; 4 Cover glass tube; 5 Strut member; 6 Getter; 7 Getter mirror surface.

4 4.2 Dimensions and tolerances of All Glass Evacuated Solar Collector Tubes Doc : MED 04 (1438)wc The dimensions and tolerances of all glass evacuated solar collector tubes shall be as shown in Table1. Outer Dia of cover glass tube D Outer Dia of inner glass tube d Table 1 All dimensions in mm Thickness of cover & inner glass tube Tube Length L , , Sealed off part length S Absorber areas for different tube sizes (A A ) The minimum absorber areas for different tube sizes of all glass evacuated solar collector tubes shall be as shown in Table 2. Table 2 Outer Diameter of the All Glass Evacuated Solar Collector Tube, in mm Length of the All Glass Min Absorber Area, in m 2 Evacuated Solar Collector Tube, in mm Solar Selective Absorbing Coating The Solar selective absorbing coating shall be three target coating having three layer - absorption layer, bonding agent cum absorption layer & anti reflection layer. 5.0 GENERAL REQUIREMENTS 5.1 MATERIAL The material of glass tube shall be of Borosilicate glass 3.3 conforming to ISO The solar transmittance ratio of glass tube shall be 0.89 ( at air mass 1.5 i.e. AM 1.5) There Shall not be any bubble (stone) bigger than 1mm on the glass tube and there shall not be more than 1 bubble (stone) within a area of 10mm x 10mm and not more than 5 bubbles (stones) on the whole of the tube. There shall be no crack around the bubble There shall be no dense knots bigger than 1.5 mm on glass tube. There shall not be more than 5 knots on the whole tube The solar absorbing ratio of solar selective coating shall be Min 92% (at AM 1.5). 5.2 APPEARANCE AND DIMENSIONS The accumulative length of minor scratches shall not be more than 1/3 tube length and the scratches shall not be visible from a distance of minimum 1200 mm.

5 Doc : MED 04 (1438)wc The selective coating of the all glass evacuated solar collector tube shall have no smear, peel off and fade off Distance from the obvious colour fading area of the selective absorber coating at the open end of the all glass evacuated solar collector tube shall be no more than 50mm The strut member supporting the free end of the inner glass tube shall be properly placed and shall not be loose The inner and cover tube at the open end of the all glass evacuated solar collector tube shall have smooth ends without any glass peel off and shall not have any deformation The length of the all glass evacuated solar collector tube is the distance from the open end to the point at which the diameter of the outer glass cover measured 15mm Bending of the all glass evacuated solar collector tube shall not be more than 0.2 % The cross section of the open end of the all glass evacuated solar collector tube at a distance of 20mm mm) from open end is of round shape. The ratio of the radius maximum size to the minimum size of the cover glass is no more than The sealed end of the tube shall not have any sharp end and shall be smooth. 6 TEST SET UP 6.1 Solar radiation shall be measured using a class-i Pyranometer on the plane of solar collector. For this, a mounting stand shall be used. 6.2 For measuring ambient air temperature, the measuring sensor (a calibrated RTD) shall be located shaded by a Stevenson screen in the vicinity of the test set-up (not more than 10 m from it. It shall be ensured that there is no obstruction by any structure or building to alter (block or enhance) the free flow of the natural wind to the sensor. The outside surface of the Stevenson screen shall be of light colour, preferably white, and its bottom shall be kept at least 1 m above the ground level. 6.3 The surrounding air speed shall be measured on the collector surface at about its middle every half an hour with an accuracy of 0.1 m/s and the average value of the test duration shall be reported along with the test results. 7 TEST REQUIREMENTS The following tests shall be performed on sample of all glass evacuated solar collector tube: 7.1 Dimensions - Shall conform to the requirements given in clause Appearance and dimensions - Shall conform to the requirements given in clause Stagnation performance parameter test - The stagnation performance (Y) shall not be less than 190 m 2. o C/kW, when tested as per Annex A. 7.4 Stagnation solar irradiance test - The stagnation solar irradiance when tested as per Annex B shall be as under: a) Not more than 3.7 MJ/m 2 for 47 mm outside diameter cover glass tube, and b) Not more than 4.7 MJ/m 2 for 58 mm outside diameter cover glass tube.

6 Doc : MED 04 (1438)wc 7.5 Average heat loss coefficient test - Average heat loss coefficient (U LT ) shall be less than 0.85 W/m 2o C when tested as per Annex C. 7.6 Vacuum performance test - Shall meet the requirement given in Annex D. 7.7 Resistance to thermal shock test - There shall be no damage when tested as per Annex E. 7.8 Resistance to impact test - There shall be no damage when tested as per Annex F. 7.9 Resistance to internal pressure test - There shall be no damage when tested as per Annex G Absorptivity and emissivity test of the selective coating - Selective coating of the tube shall have absorptivity Min 0.92 and emissivity less than 7% when tested as per Annex H. 8. TEST REPORT. A test report shall be generated in the format given at Annex J. 9. MARKING 9.1Designation Designation of all glass evacuated solar collector tube shall comprise of following 5 parts: Part-1 All glass evacuated solar collector tube Part -2 Chemical symbol of solar selective coating Part -3 Outer diameter of cover glass and inner glass tube Part -4 Length of tube Part -5 Type of coating (Three target) Example: All glass evacuated solar collector tube having AlN/AlN-SS/Cu multilayer selective coating with 58 mm outer diameter of cover glass tube and 47 mm outer diameter of inner glass tube, 1800 mm length and three target coating shall be designated as: ET - AlN/AlN-SS/Cu - 58/ T 9.2 The all glass evacuated solar collector tubes may also be marked with manufacturer's trade mark or logo, batch no. or date of manufacture. 9.3 BIS Certification Marking Each Glass evacuated solar collector tube may also be marked with the Standard Mark The use of BIS certification mark is governed by the provisions of Bureau of Indian Standards Act, 1986 and the Rules and Regulations made there under. The details of conditions under which the license for the use of Standard Mark may be granted to manufacturers or producers may be obtained from the Bureau of Indian Standards. 10. PACKING The all glass evacuated solar collector tubes shall be suitably packed in boxes to avoid any damage during handling, storage and transportation.

7 Doc : MED 04 (1438)wc ANNEX A STAGNATION PERFORMANCE PARAMETER TEST (Clause 7.3) A-1 Test condition - These measurements shall be conducted outdoors. The plane on which the Pyranometer is placed shall be parallel with the plane of collector. Solar irradiance G 800W/m 2, Ambient temperature 20ºC t a 30ºC and wind velocity 4 m/s. A-2 Test bench set up - Place 3 all-glass evacuated solar collector tubes in parallel in south-north direction. The all glass evacuated solar collector tube to be tested shall be in the middle and the other two tubes are accompanying test tubes. The center to center spacing is twice the inner tube diameter. The center to the flat plate reflector spacing is 70 mm. The flat plate reflector has a diffuse reflectance no less than Air is used as the thermal conducting medium inside the all glass evacuated solar collector tube, the temperature shall be measured at the center of the tube and the sensor shall not contact the wall of the glass tube. A 50mm thick rigid polyurethane foam is used as thermal insulation cap at the open end of the all glass evacuated solar collector tube. The cap shall not cover the selective surface. The angle of inclination between the horizontal plane and the all glass evacuated solar collector tube is 士 5 of latitude of the location but not less than The measuring device is to be set up as shown in the Fig 2. A-3 Test Procedure: When the solar irradiance is G 800W/m 2 士 30W/m 2 record the solar irradiance, temperature inside the collector tube and ambient temperature every 5 minute, take 4 readings. Take the average value of the 4 readings of solar irradiance as solar irradiance G. Similarly, take the average value of 4 readings of temperature inside the collector tube and ambient temperature as temperatures t s and t a respectively. A-4 Test instruments: Pyranometer, class-1 Platinum Resistance Thermometer or RTD Sensor, Mercury Thermometer, Anemometer Fig. 2 Schematic diagram of thermal performance testing device of all glass evacuated solar collector tube Key 1 - All glass evacuated tube collector 2 - Diffuse flat plate reflector

8 Doc : MED 04 (1438)wc 3 - Platinum resistance thermometer 4 - Thermal insulation cap 5 - Pyranometer 6 - Radiation recording device 7 - Temperature testing device 8 - Data Logger 9- Mounting frame 10 - Mercury thermometer 11 - Thermometer Housing 12 - Anemometer A-5 Calculate the stagnation performance parameter Y of all-glass evacuated solar collector tube according to formula (1) t s - t a Y = (1) G Where as Y stagnation performance parameter, m 2 C/kW t s stagnation temperature, o C t a average ambient temperature, o C G solar irradiance, kw/m 2 B-1 Test conditions - Same as in A-1. ANNEX B STAGNATION SOLAR IRRADIANCE TEST (Clause 7.4) B.-2 Test Bench set up - Same as in A-2. All-glass evacuated solar collector tube uses water as the thermal conducting medium. B-3 Test Procedure Cover the all glass evacuated solar collector tube with opaque cover. Fill the water. Initially the water temperature should be lower than ambient. As soon as the water temperature is equal to ambient temperature, record the initial solar irradiance. Expose the all glass evacuated solar collector tube to the sun by removing the opaque cover. When water temperature inside the tube rises by 35 o C record the final solar irradiance. The difference between final solar irradiance and initial solar irradiance is stagnation solar irradiance.

9 Doc : MED 04 (1438)wc ANNEX C AVERAGE HEAT LOSS COEFFICIENT TEST (Clause 7.5) C-1 Test Conditions - This test shall be conducted indoors. The average ambient temperature during the testing period is 20 o C t a 30 o C and there is no wind directly blowing onto the all glass evacuated solar collector tube. C-2 Test Bench set up C-2.1 All glass evacuated solar collector tube is placed vertical to the horizontal plane. The open end is covered by the same thermal insulation cap as in A -2. C-2.2 There shall be three temperature measuring points from top to bottom in the all-glass evacuated solar collector tube. The measurement points are given as under : Tube Length (mm) L Distance from Open end to the Measurement points in mm , 750, , 900, 1500 C-3 Test Procedure - Fill up the all glass evacuated solar collector tube with hot water of minimum temperature 90 o C and drain it out after two minutes. Immediately after this preheating, fill up the all glass evacuated solar collector tube with hot Water of minimum temperature 90 o C. The water level must be up to a height of 40mm from the top of the tube (open end) for tube length up to 1500mm and up to a height of 50mm from top of the tube (open end) for a tube length of Record the first average temperature (t 1 ) of the 3 measuring points when the water temperature naturally drops to an average of 80 o C 士 0.2 o C. Record the second and third average temperature ( t 2 and t 3 ) of three measuring points at an interval of 30 minutes each. Simultaneously, record the corresponding three ambient temperatures (t a1, t a2 and t a3 ) at the same time. C-4 Test Instrument - Platinum Resistance Thermometer, Mercury Thermometer, C-5 Calculate the average heat loss coefficient U LT of the all-glass evacuated solar collector tube according to formula (2), (3) and (4). C pw.m ( t 1 - t 3 ) (2) U LT = A A ( t m - t a ) τ ( t 1 + t 2 + t 3 ) t m = 3.(3) ( t a1 + t a2 + t a3 ) t a = (4)

10 3 Where as U LT Average heat loss coefficient, in W/(m 2 o C) t m Average water temperature inside the all-glass evacuated solar collector tube during the test, in o C t a Average ambient temperature, in o C τ Total testing time from water temperature t 1 to t 3, in s M Mass of water inside the all-glass evacuated solar collector tube, in kg C pw Specific heat of water, in J/kg oc) A A Absorber surface area, in m 2.(see 4.4) t a1, t a2, t a3 Corresponding ambient temperature recorded at the same time,in o C t 1, t 2,t 3 Three average water temperature inside the all glass evacuated solar collector tube at three measuring points each, o C. Doc : MED 04 (1438)wc ANNEX D VACUUM PERFORMANCE TEST (Clause 7.6) D-1 Air pressure test inside the vacuum jacket - Use spark leak detector to probe the vacuum jacket of the open end of the all glass evacuated solar collector tube. The intensity of spark and color shall be used to check the vacuum standard. D-2 Vacuum quality test - Electric heating rod (single-end outlet, diameter of 20mm and rated power of 1500 W) not less than 90% the length of the collector tube is placed inside the all glass evacuated solar collector tube. The electric heating rod is fixed with a aluminum fin type arrangement before being put into the collector tube. Both ends of the aluminum fins are covered with asbestos cloth to prevent direct contact of the aluminum wing with the collector tube wall. The opening of collector tube is covered with fiber glass. A thermocouple is placed at the middle of the collector tube to measure the inner glass tube temperature. The temperature of the inner glass tube is maintained at 340 C ( 10 C) for 48 h. The change in mirror surface of the getter is measured. The measurement will be made from the point of diameter of 15mm of the sealed-off end of the collector tube to the getter mirror surface edge. There shall be measurement at six equal portions. The average value of the 6 points represents the getter mirror surface axial length. If the rate at which the getter mirror has disappeared not more than 50%, it qualifies the criteria. ANNEX E RESISTANCE TO THERMAL SHOCK TEST (Clause 7.7) E--1 Test Conditions - This test shall be performed indoor. E-2 Insert the open side of the all glass evacuated solar collector tube into ice water ( 1 C) for a depth not less than 100mm and keep it for one minute. Take it out and immediately immerse it into a hot water bath of temperature not less than 90 C for a depth not less than 100mm and keep it for one minute. Take it out and immediately immerse in the ice water ( 1 C). Repeat this test three times and all glass evacuated solar collector tube shall not have any damage.

11 Doc : MED 04 (1438)wc ANNEX F RESISTANCE TO IMPACT TEST. (Clause 7.8) F-1 Test Conditions - This test shall be performed indoor. F-2 Fix the all glass evacuated solar collector tube on the test frame supported by 2 V-shaped groove with 5mm thick polyurethane liner with 500mm space in between. A steel ball of 30mm diameter is dropped from a height of 450mm oriented to the middle of the collector tube. The steel ball drops freely with vertical impact on the collector tube and the collector tube shall have no damage. ANNEX G RESISTANCE TO INTERNAL PRESSURE TEST (Clause 7.9) G-1 Test Condition - This test shall be performed indoor. G-2 Fill the all glass evacuated solar collector tube with water. Increase the water pressure evenly to 0.6MPa and keep it for one minute. The all glass evacuated solar collector tube shall not have any damage. ANNEX H ABSORPTIVITY AND EMISSIVITY TEST OF THE SELECTIVE COATING (Clause 7.10) H-1 Test Conditions - This test shall be performed indoor. H-2 Test Procedure for Absorptivity - Use a spectrophotometer with integral ball to measure the transmission ratio of the solar selective absorbing coating respectively at 150mm from the open end of the all-glass evacuated collector tube and at middle of the collector tube length within a wavelength of 0.3 µm~2.5 µm. Then calculate the solar absorbing ratio at AM1.5 and use the average value of the two to express the solar absorbing ratio of the solar selective absorbing coating inside the all-glass evacuated solar collector tube. H-3 Test Procedure for Emissivity- Place the tube of the all glass evacuated solar collector tube inside sealed water-cooled jacket. Place a electric heater inside and on two sides of the equipment to make a hemisphere emissivity measurement device. Under quasi-steady-state, directly measure the hemisphere emissivity of the selective absorbing coating of the absorber of the all glass evacuated solar collector tube at 80 o C 士 5 o C..

12 Doc : MED 04 (1438)wc ANNEX - J Proforma of Test Report (Clause 8) Official Stationary of the Test Laboratory/ Institution Address and Contact Details TEST REPORT A. GENERAL 1. Name and Address of manufacturer/supplier 2. Contact details of manufacturer /supplier 3. Details of sample submitted/model 4. Latitude & longitude of test laboratory Latitude Longitude 5. Duration of the Test Date of submission - Date of completion - B. SPECIFICATIONS OF THE TEST SAMPLE (All dimensions are in mm, unless specified otherwise) Evacuated Tube (ET) 1 Make/Model 2 Complete address of the manufacturer including e- mail/web site etc. 3 Type All Glass Evacuated Solar Collector Tube 4 Tube length, L 5 Outer diameter of inner tube (as per manufacturer s report), d 6 Outer diameter of outer tube, D 7 Details of selective coating(as per manufacturer s report) 8 Aperture (exposed) area of a single tube C. TEST RESULTS 1 Stagnation Performance Parameter Test 2 Resistance to Thermal Shock Test 3 Stagnation Solar Irradiance Test 4 Average Heat Loss

13 Doc : MED 04 (1438)wc Coefficient Test 5 Resistance to internal Pressure Test 6 Resistance to Impact Test Remarks Vacuum performance test i) Air Pressure Test ii) Vacuum Quality Test Selective Coating i) Absorptivity test ii) Emissivity test Any Other Details Date: Place: (Testing Officer) (Head of the Test laboratory)

14 Doc : MED 04 (1439)wc Draft Indian Standard STORAGE WATER TANK FOR ALL GLASS EVACUATED TUBES SOLAR COLLECTOR - SPECIFICATION Not to be reproduced without the permission of BIS or used as a STANDARD Last date for receipt of comments is: 15 July SCOPE This standard specifies requirements of storage water tank for all glass evacuated tubes solar collector. This standard covers only vented type storage water tank. 2 REFERENCES The standards listed below contain provisions which, through reference in this text constitute provisions of this standard. At the time of publication, the editions were valid. All standards are subject to revision and parties to agreements based on this standard are encouraged to investigate the possibility of applying the most recent editions of the standards indicated below: IS No Title IS 1079: 2009 Hot rolled carbon steel sheet and strip (sixth revision) IS 6911: 1992 IS 14246: 2013 Stainless steel plate, sheet and strip specification (first revision) Continuously pre-painted galvanized steel sheets and coils (first revision) Doc : MED 04 (1050) Test procedure for thermosyphon type domestic solar hot water heating system (under print) 3 DEFINITIONS 3.1 Closed Storage Water Tank Storage water tank working under the pressure of running water with one or more valves at its outlet system to control flow of water (not covered in this standard). 3.2 Vented storage water tank Storage water tank having opening to the atmosphere and pressure inside the tank is always equal to atmospheric pressure all the time. 3.3 Rated pressure - Allowable work pressure inside the water tank equal to the maximum pressure of the water supply system connected to the tank. 4 TYPE OF STORAGE WATER TANK 4.1Close type storage water tank Such type of storage water tank are close to collector but not integrated with the collector i.e. evacuated tubes of collector are connected to manifold and manifold is connected to storage water tank. A typical solar collector with close type storage water tank is shown in Fig.1.

15 Doc : MED 04 (1439)wc Fig 1 Close type storage water tank 4.2 Integrated type storage water tank Such type of storage water tank are integrated to the collector i.e. evacuated glass tubes of collector are directly connected to storage water tank. A typical solar collector with integrated type storage water tank is shown in Fig.2. Fig 2 Integrated type storage water tank 5 MAIN PARTS OF STORAGE WATER TANK 5.1 Inner tank Inner tank shall be manufactured from any of the following materials: Stainless steel sheet conforming to grade X02Cr19Ni10 or X02Cr17Ni12Mo2 of IS The thickness of sheet shall be minimum 0.5mm when fabricated using MIG or Argon arc welding and minimum 0.8mm when fabricated using other type of welding Mild steel sheet conforming to IS 1079 with anti-corrosive coating. This material is specially suitable for use of collectors in areas having high TDS (more than 300 PPM) and chlorides contents ( more than 50 PPM ) in water. The thickness of sheet shall be minimum 1.5 mm. The thickness of coating shall be minimum 150 micron and should be capable to

16 Doc : MED 04 (1439)wc withstand minimum five years warranty. Anti-corrosive coating may be enamel coating (glass lining or enamel lining) or special food grade coating. 5.2 Outer cladding - The material of outer cladding shall be continuously pre-painted galvanized steel conforming to IS Alternatively, material of outer cladding may be Aluminium /stainless steel/frp of suitable thickness. 5.3 Insulation Layer The insulation layer shall be pre-injected PUF of minimum thickness 50mm. The density of PUF shall be 28 to 32 kg/m 2. For tanks of water capacity more than 300 litre, Rockwool insulation of minimum 100 mm thickness is also permitted. 5.4 Inner Sealing The material of inner sealing shall be high temperature resistant silicon rubber. 5.5 Outer sealing - The material of outer sealing shall be EPDM rubber. 5.6 Sacrificial Anode (optional) - Additional corrosion protection may be provided by the installation of a sacrificial anode. The anode shall be manufactured from magnesium (or a material with higher protection potential) cored with a steel rod to ensure mechanical and wear strength suitable for the duty it has to perform and to withstand the mechanical shocks which may be induced during transport and installation. The anode shall be mounted in a robust manner at the end of the tank and shall be in electrical contact with the inner tank. The anode shall be easily replaceable. 6 GENERAL REQUIREMENTS 6.1 The outer cladding shall be smooth without any crack or obvious scratch and no coating peeling off. 6.2 Insulation layer shall be stuffed tightly. There shall be no obvious shrinkage or bulging of insulating material. 6.3 Outer sealing shall be without any defect. 6.4 Access door may be provided for easy periodic cleaning of the tank. 6.5 All holes of tank shall be provided with protective caps to avoid entry of any foreign material in the tank before its installation in the system.

17 Doc : MED 04 (1439)wc 7 TEST REQUIREMENTS 7.1 Measurement of storage water tank capacity The capacity of storage water tank shall be within + 5 % of declared capacity when measured as per 8.1. Note The declared capacity of storage water tank shall be equal to capacity of the system. Volume of water in evacuated tubes and manifold shall not be accounted in the capacity of storage water tank. 7.2 Leakage test No leakage when tested as per Rigidity test There shall be no deformation or damage when tested as per Idle heating test There shall be no deformation, crack or other damage when tested as per Integral Test There shall be no leakage or damage when tested as per Performance test Heat loss coefficient of the system ( U L ) shall be <2 W/(m 2 0 C) when tested as per TEST PROCEDURE 8.1 Measurement of storage water tank capacity Volume of water required to fill the empty storage water tank at ambient temperature shall be measured to find the capacity in litres. 8.2 Leakage test F ill the storage water tank with clean water and release the air inside the tank. Close air vent and increase the pressure to 0.05 MPa and maintain the pressure for 5 minutes. There shall be no leakage or permanent deformity. 8.3 Rigidity test Raise one end of the storage water tank connected in the system without water by 0.1m and keep for 5 minutes before putting to original position. There shall be no damage and apparent deformation in the connecting parts of the storage water tank. 8.4 Idle heating test Install the system with water storage tank under test outdoors according to operating conditions. There shall be no presence of water inside the system Measure the daily cumulative solar irradiance on the plane of the collector which shall be more than 16 MJ/m 2. The average wind velocity shall be 4m/s or less. This test to be conducted for three consecutive days. At the end of the test there shall be no deformation, crack or other damage to storage water tank. 8.5 Integral test Install the system with water storage tank under test outdoors according to operating conditions. The system is filled with water. Measure the daily cumulative solar irradiance on the plane of the collector which shall be more than 16 MJ/m 2. The average wind

18 Doc : MED 04 (1439)wc velocity shall be 4m/s or less. This test to be conducted for three consecutive days. At the end of the test there shall be no leakage or damage to storage water tank. 8.6 Performance test Test the system with water storage tank under test for heat loss coefficient as per Indian Standard Doc : MED 04(1050). 9 TYPE OF TEST 9.1 Routine test Each inner tank shall be tested for leakage as per 8.2 for a period of 5 minutes by manufacturer. 9.2 Type test All the tests specified in 7.1 to 7.6 are type tests and shall be carried out initially for each capacity either in manufacturer s lab or outside approved lab for approval of the product. These tests shall be repeated every two years after initial approval or before if there is any change in design, technology or materials. 10 MARKING 10.1 The following information shall be marked on the storage water tank: i) Name of the manufacturer s or trade mark, ii) Water capacity in litres, iii) Serial No., and iv) Month and year of manufacture BIS Certification Marking Each tank may also be marked with the Standard Mark The use of BIS certification mark is governed by the provisions of Bureau of Indian Standards Act, 1986 and the Rules and Regulations made there under. The details of conditions under which the license for the use of Standard Mark may be granted to manufacturers or producers may be obtained from the Bureau of Indian Standards. 11 PACKING The storage water tanks shall be suitably packed in boxes to avoid any damage during handling, storage and transportation.

19 Doc: MED 04 (1440) Draft Indian Standard ALL GLASS EVACUATED TUBES SOLAR WATER HEATING SYSTEM Not to be reproduced without the permission of BIS or used as a STANDARD Last date for receipt of comments is: 15 July SCOPE 1.1 This standard specifies requirements of all glass evacuated tubes solar water heating system. This standard covers only non concentrating, direct, vented solar collector system that convert solar radiation to thermal energy for heating water based on thermo syphonic principle. 1.2 This standard do not apply to solar water heating systems which have an auxiliary heater as an integral part of the system, since the operation of the auxiliary input may influence the performance of the system. 2 REFERENCES The standards listed below contain provisions which, through reference in this text constitute provisions of this standard. At the time of publication, the editions were valid. All standards are subject to revision and parties to agreements based on this standard are encouraged to investigate the possibility of applying the most recent editions of the standards indicated below: IS No IS 277:2003 IS 2062:2011 IS 6911: 1992 IS/ ISO 9488:1999 Title Galvanized Steel Sheets (Plain and Corrugated) specification (Sixth revision) Hot rolled medium and high tensile structure steel specification (Seventh revision) Stainless steel plate, sheet and strip specification (first revision) Solar energy Vocabulary IS 14246:1995 Contimuously prepainted galvanized steel sheets and coils specification (Sixth revision) Doc: MED 04(1438) All glass evacuated solar collector tubes (under wc) Doc: MED 04(1439) DOC: MED 04(1050) Storage water tank for all glass evacuated tubes solar collector (under WC) Test procedure for thermosyphon type domestic solar hot water heating systems (under print) 3 TERMINOLOGY In addition to the terms and definitions given in IS/ISO 9488 and Doc: MED 04(1438) following shall also apply for this standard: 3.1 Ambient Air - Ambient air is the outdoor air in the vicinity of the solar collector system being tested.

20 Doc: MED 04 (1440) 3.2 Aperture Area - Maximum projected area through which the un-concentrated solar radiation enters a collector. 3.3 Water Draw-Off Rate - Rate at which water is withdrawn from a water heating System. 3.4 Direct Solar Water Heating System - Heating system in which the water to be heated is circulated through a collector where the solar heat gathered by the collector is transferred to the circulating water itself. 3.5 Concentrating Solar Collector - A solar collector which uses reflectors, lenses or other optical elements to concentrate the radiant energy passing through the aperture onto an absorber which has a surface area smaller than the aperture (not covered in this standard). 3.6 Cover Plate - The cover plate is the material or materials covering the aperture and most directly exposed to the solar radiation. These materials are generally used to reduce the heat loss from the absorber to the surroundings and to protect the absorber. 3.7 All glass evacuated tubes solar collector - Solar collector employing transparent glass tubes with an evacuated space between the tube wall and the absorber. 3.8 Forced System - In which heat transfer fluid is forced through the collector either by mechanical means or by externally generated pressure (not covered in this standard). 3.9 Gross Collector Area - Maximum projected area of a complete solar collector, excluding any integral means of mounting and connecting fluid pipe work. For an array or assembly of flat plate collectors, evacuated tubes or concentrating collectors, the gross area includes the entire area of the array, i.e. also borders and frame Heat Exchanger - Device specifically designed to transfer heat between two physically separated fluids. Heat exchangers can have either Single or double Walls Heat Transfer Fluid - Fluid that is used to transfer thermal energy between components in a System Indirect Solar Water Heating System - heating system in which the water to be heated is not circulated through a collector, but in which the solar heat gathered by the collector is transferred to the water by means of an intermediary fluid in a heat exchanger (not covered in this standard) 3.13 Open System - In which the heat transfer fluid is in extensive contact with the atmosphere Reflector or Reflective Surface: A surface intended for the primary function of reflecting radiant energy Solar Collector - A solar collector is a device designed to absorb incident solar radiation, to convert it to thermal energy, and to transfer the thermal energy to a fluid coming in contact with it Solar Energy -The energy originating from the sun's radiation primarily encountered in the wavelength region from 0.3 to 3.0 micrometers.

21 Doc: MED 04 (1440) 3.18 Solar Storage Capacity - Quantity of sensible heat that can be stored per unit volume of store for every degree of temperature change Water Tank Capacity - Measured volume of the water in the tank when full. This capacity shall not include the water in the collector tubes and will be equal to system capacity Thermo-syphon System- The system which utilizes only density changes of the heat transfer fluid to achieve circulation between collector and storage tank Vented System - In which contact between the heat transfer fluid and the atmosphere is restricted either to the free surface of a feed and expansion cistern or to an open vent pipe only Working Pressure / Rated pressure - Maximum system pressure (in kg/cm 2 ) at which the water heater is designed to operate, or the maximum operating pressure (in kg/cm 2 ) assigned to the water heater by the manufacturer and marked on the water heater. 4 DESIGN 4.1 All glass evacuated tubes solar water heating system shall comprise of following main components: a) All glass evacuated tubes for solar water collector, b) Storage water tank for all glass evacuated tubes solar collector, c) Diffuse flat plate reflector (if provided), d) Manifold (applicable for closed type water storage tank in the system), e) Tube resting caps, and f) Supporting frame/stand. 4.2 All glass evacuated tubes in the solar water heating system shall conform to Doc: MED 04(1438). 4.3 Storage water tank in the solar water heating system shall conform to Doc: MED 04(1439). 4.4 Diffuse flat plate reflector if provided shall be bright Aluminium/ stainless steel sheet of suitable thickness. 4.5 Manifold when provided shall have header (inner container) of Stainless steel sheet conforming to grade X02Cr19Ni10 or X02Cr17Ni12Mo2 of IS 6911 and outer cladding shall be from continuously pre-painted galvanized steel sheet conforming to IS The insulation in manifold shall be PUF of minimum 25mm thickness. Alternatively, inner container of manifold may be of mild steel sheet conforming to IS 1079 or other equivalent with anticorrosive coating. 4.6 Tube resting caps shall be from UV stabilized ABS plastic material. 4.7 Supporting frame/stand for the solar heating system shall be manufactured from any of the following material : a) Mild steel conforming to IS 2062 with hot dip galvanized or powder coated b) Galvanized steel sheet conforming to IS 277 with powder coating c) Stainless steel

22 d) Aluminium with anodized coating The frame/stand shall be strong enough to support the system during its lifetime. 5 REQUIREMENTS 5.1 General Doc: MED 04 (1440) The system shall fulfill general safety requirements, e.g. care shall be taken to avoid protruding sharp edges on the outside of the system All parts of the system to be mounted outdoors shall be resistant to UV radiation and other weather conditions over the prescribed maintenance interval. Any maintenance or replacement of system parts required in order to maintain the system s normal working over a period of 10 years shall be clearly stated in the instruction manual The quality of all the work carried out on solar water heating system, including the pipe connections, brazing, welding, insulation of electrical conductors and attachment of accessories, shall be of such nature that the water heating system will perform its intended function without any failure. 5.2 Over temperature protection for system 5.2.1General The system shall be designed in such a way that prolonged high solar irradiation without heat extraction does not cause any situation in which special action by the user is required to bring the system back to normal operation When the system has a provision to drain an amount of water as a protection against overheating, the hot water drain shall be constructed in such a way that no damage is done to the system, piping or any other materials in the house by the drained hot water. The construction shall be such that there is no danger to inhabitants from steam or hot water from the drain When the overheating protection of the system is dependent on electricity supply and/or cold water supply, this shall be stated clearly in the instructions and on the system. 5.3 Over temperature protection for materials The system shall be designed in such a way that the maximum allowed temperature of any material in the system is never exceeded. 6.0 TESTING 6.1 Pre-conditioning Test All glass evacuated tube solar collector system shall be exposed to weather conditions for 2 days having solar irradiation on the plane of solar collectors more than 4.5 kw/ m 2. The

23 days for solar irradiance lesser than this value shall not be counted. Doc: MED 04 (1440) After preconditioning of 2 days, all parts shall be inspected for any visual sign of degradation, deformation, ingress of moisture/dust, etc. and shall be reported. 6.2 Test Requirements Following tests shall be conducted on sample of all glass evacuated tube solar heating system: Exterior test The sample shall meet the requirements given in Annexure A Leakage Test There shall be no leakage or damage in the system when tested as per Annexure B Stagnation Test There shall be no damage or deformation in the system when tested as per Annexure C External Thermal Shock Test There shall be no damage or deformation in the system when tested as per Annexure D Internal Thermal Shock Test There shall be no damage or deformation in the system when tested as per Annexure E Frost Resistance Test This test is applicable only to those systems which manufacturer claims to be frost resistant. There shall be no leakage, damage or twisting in the system when tested as per Annexure F Thermal Performance Test The thermal performance of the system shall be tested according to the test methods specified in Doc:MED 04(1050). The performance shall be reported in the test format as specified in Annex IV of this standard Resistance to Impact Test This test shall be carried out as per Doc: MED 04(1438) on each collector tube after dismounting from the system and kept horizontally. There shall be no damage on any collector tube. 7 INSTRUCTION MANUAL 7.1 The manufacturer shall supply an instruction manual with each system containing at least following information in easily understandable language: a) Brief description of system and its components b) Technical specification of the system

24 Doc: MED 04 (1440) c) Schematic diagram of all glass evacuated tubes solar water collector system; d) Instructions for assembly and installation of the system ( including mounting details, piping/plumbing diagram) and safety precautions; e) Instructions for operation and maintenance of the system; f) Troubleshooting mentioning common problems, their possible causes and solutions; g) List of service outlets; h) Warranty clause clearly indicating limitations. 8 MARKING Each system shall have the following information durably marked on a plate or label attached to the system at visible place: a) Name of manufacturer or recognized trade mark; b) Collector area in m 2 ; c) Water capacity of tank in litres per day (lpd); d) No. of evacuated tubes; e) Outer diameter and length of evacuated tubes; f) Serial No.; and g) Month and Year of manufacture.

25 Doc: MED 04 (1440) ANNEXURE A EXTERIOR CHECK (Clause 6.2.1) A-1 Test conditions - This test is conducted at normal temperature twice on the sample. Assemble the evacuated tube solar collector sample according to the manufacturer s instructions. First exterior check on the sample before starting other tests and second exterior check after completion of all tests. A-2 Test Procedure - This is visual check of the main parts of the evacuated tube solar collector system and any abnormal observation on the system is recorded. A-3 Test Result - There shall be no problem with the exterior of the sample. The result of the first and last exterior checks shall be consistent. ANNEXURE B LEAKAGE TEST (Clause 6.2.2) B-1 Test Conditions - This test is conducted at normal temperature twice on the sample. First leakage test on the sample after first exterior check and second leakage test before second exterior check. Test pressure shall be 0.06MPa. B- 2 Test Procedure - Fill the evacuated tube solar collector system with water at normal temperature. Release all the residual air inside the system through the exhaust valve and shut off the exhaust valve. Then slowly increase the pressure to the test pressure through the hydraulic source. Maintain the test pressure for 10 min. B-3 Test Result - Check any deformation, leakage or crack in the system during and after the test.. Results of the first and last tests shall be consistent. ANNEXURE C STAGNATION TEST (Clause 6.2.3) C-1 Test Conditions - Daily average ambient temperature t a 8, daily solar irradiation received by the evacuated tube solar collector H 17MJ/(m 2 d), the evacuated tube solar

26 Doc: MED 04 (1440) collector stays at least 1 day under stagnation in the sunlight. C-2 Test Procedure - With air as the medium, apart from the piping joint of the evacuated tube solar collector that is open for exhaust, the rest of the joints are sealed with stoppers. The temperature sensing element is put at the middle of the header pipe to monitor the air temperature at the middle of the header pipe during test. C-3 Test Result - Check the state of damage and deformation with the evacuated tube solar collector and record hour by hour the irradiation H, ambient temperature t a, air velocity u and the air temperature at the middle of the header pipe (stagnation temperature) during the test. ANNEXURE D EXTERNAL THERMAL SHOCK TEST (Clause 6.2.4) D - 1 Test Conditions - When the solar irradiation of the evacuated tube solar collector reaches over 700W/m 2, put the collector for 30min. D 2 Test Procedure - After stagnation period spray water evenly on the evacuated tube solar collector that meets the test conditions, the inclination angle between the spraying direction and the collector shall be no less than With water temperature at 15 ±10, the spraying quantity shall be more than 200kg/(m 2 h). Keep spraying water for 5 min. D - 3 Test Result - Check whether there is damage and deformation with any part of the evacuated tube solar collector and record the irradiation H, water flow and water temperature during the test. ANNEXURE E INTERNAL THERMAL SHOCK TEST (Clause 6.2.5) E - 1 Test Conditions - When the solar irradiation of the evacuated tube solar collector reaches over 700W/m 2, put the collector for 30min. E 2 Test Procedure - Supply water to the absorber of the evacuated tube solar collector that meets the test conditions for 5 min, with water temperature at 15 ±10, the flow shall be no less than 60kg/(m 2 h).

27 Doc: MED 04 (1440) E - 3 Test Result - Check whether there is damage and deformation with any part of the evacuated tube solar collector and record the irradiation H, water flow and water temperature during the test. ANNEXURE F FROST RESISTANCE TEST (Clause 6.2.6) F-1 Test Conditions - This test applies to the systems which the manufacturer claims to be frost resistant including systems that work under frost resisting circulation. This test is not applicable to those systems that use frost resisting liquid medium. This test is divided into frost resistance test conducted when the collector is filled with water and the frost resistance test conducted when the collector is empty. F 2 Test Procedure - Install the collector for the frost resistance test in a cold storage. The installation inclination angle is the minimum included angle to the horizontal plane recommended by the manufacturer. If this angle is not recommended, the installation inclination angle shall be Fill the collector with cold water of normal temperature, the water temperature t 1 range: 8 t Keep the collector at (-20±2) for at least 30min, then increase the temperature to +10, keep it for 30min. Such freezing and warming circulation shall be conducted 3 times. Discharge all the water from the collector. Keep the collector at (-20±2) for at least 30min, then increase the temperature to +10, keep it for 30min. Such freezing and warming circulation shall be conducted 3 times. F 3 Test Result - At the end of the test, check whether there is leakage, damage, deformation or twisting with the collector.