Solar water heaters based on Flat plate Collectors (FPC based SWH):

Here the solar radiation is absorbed by flat plate collectors which consist of an insulated outer metallic box covered on the top with glass sheet. Inside there are blackened metallic absorber (selectively coated) sheets with built in channels or riser tubes to carry water. The absorber absorbs the solar radiation and transfers the heat to the flowing water.

                                                                                                                           
              Flat Plate Solar Collectors is the earlier technology used in Solar Water Heating Systems; however they are still today the most efficient & reliable for Solar Water Heating Systems. Under soft water conditions they have a life of 20 years & more.. Our ATASH Flat Plate Collectors have been carrying the prestigious ISI Mark, since the last 12 years & our manufacturing for the same has been since the last 21 years.

General Specifications of Solar Water Heating System based on Flat plate Collectors (FPC based SWH):

Detailed specifications of various components of Solar Water Heating System are given below:

1. FLAT PLATE COLLECTOR

   As per BIS specifications and ISI certificate with area of 2 M² with selectively coated Cu-Cu absorber. Minimum one number flat plat collector with 2 M² areas for each 125 LPD capacity of system.

   1. ABSORBER

      1. Material : Copper sheet and Copper Tube
      2. Thickness of the sheet : 38 SWG (0.15MM)
      3. Risers: Diameter  : 12.7 mm O.D.(+ 0.5 mm) Thickness    : 24 SWG (0.56 mm) (as per IS 2502)
         Nos.  : 8 or 9 nos.
         
      4. Header:Diameter                     : 25.4 mm O.D. (0.71mm + 0.5mm) Thickness                    : 22 SWG (0.8 mm)
         Projection outside       : 40 mm (+0.5mm) including the collector box and the flanges
         
      5. Space between Riser Tubes: Maximum 12 cms from center to center of the risers. The free edges at the sides not to exceed 6 cm from the center of the extreme and riser tube. For independent fin or joints in the sheet an overlap of minimum 2 mm.
      6. Bonding between Riser & Sheet: Welding may be of continuous nature inter-arc-spot welding type with the product of number of spots per fin & area of spots exceeding the product length of the fin & twice the thickness of the fin for each fin (continuous welding). The brazing & soldering with minimum 40% tin solder or suitable brazing material. Brazing of soldering continuous with 10% of the total length of each fin & any continuous non-soldering area not exceeding 25mm at any stretch (Brazing/Soldering).
         
      7. Effective area of Absorber : 2 M² (± 0.1 M²) including the projected area of header
      8. Header-Riser joints: The assembly of risers with the header should ensure not more than 5mm tube protrusion inside the header. The riser should be brazed with suitable brazing alloys with or without the use of flux. Any flux used in soldering/brazing shall be mechanically remove & neutralized with the solution of sodium carbonate to avoid corrosion problems in future.
      9. Absorber Coating.

         i. Absorbivity	92 %
         ii. Emissivity	2.5%
         iii. Coating Stability	up to 300 ºC

         Deterioration in these values should not be greater than 5% in a year.
         The absorber panel should be degreased & suitable primer with proper adhesion & compatibility with base material should be used prior to the application of points.
         
      10. LEAKAGE TESTING OF RISER – HEADER ASSEMBLY: It should be treated for leakage & strength at a minimum hydraulic/pneumatic pressure of 5 kg/cm².
          

   2. FLAT PLATE COLLECTOR BOX:

      1. Overall dimensions of the box :
         1. Length       : 186 cm (±1 cm) /212 cm (±1 cm)
         2. Breadth     : 124 cm (±1 cm) / 104 cm (±1 cm)
         3. Height       : 10 cm (±1 cm)

      2. Collector box materials: Aluminum

         • 22 SWG Aluminum sheet for the bottom
         • Aluminum extruded sections of size of 100mm x 25 mm channel sections with thickness 1.6 mm for the sides.
         • 16 SWG Aluminum angle (dim.25mm x 25mm) for retaining collector glazing.

      3. Fabrication of the Box:

         Side channels should be welded by inert-arc gas welding or gas brazing to ensure leak proof continuity of the joints of the box.
         

      4. Attachment of Bottom Sheet:

         By riveting spot welding or with S.S. Screws & caulking of the joints with sealing paste of zinc oxide based or rubber based or silicon rubber based or epoxy based sealing compounds.  Caulking may be done on the inside joints or inside as well as outside joints to ensure leak proof joints.
         

   3. Collector Support Frame:

      1. The structure should be in a position to withstand a wind velocity of 100 Kms. / hr. A typical way do this is that it should be made with angle iron stronger than 35 mm x 35mm x 3mm and should have vertical support at top & bottom edge of the inclined plane of the collector at a distance of 2.5m or less.  The vertical support should be firmly grouted to the roof in the ground in case of ground mounted system.  The grouting blocks should be of minimum equal to 25 cm x 25 cm x 15 cm and finished properly.  In case the grouting is carried out on a roof already water proofed with asphalt the back support of the collectors may be angled to the parapet or the size of the grouting block should be increased to provide for a dead weight anchoring of 75 kg per leg of the vertical support.
      2. Painting of the Support Frame: Proper cleaning & degreasing of the surface should be done before painting. Two coats of zinc chromate, red oxide primer should be applied followed by one coat of enamel paint of suitable colour.
         

2. HOT WATER STORAGE TANK (Material of construction):

   
   

   Sr. No.	SWHS capacity in LPD	Cu (thickness in mm)	S.S. (thickness in mm)	MS coated with anti-corrosive treatment and epoxy paint stable up to 150ºC (thickness in mm)
   01	250 to 300	0.9 to 1.0 mm.	1.0 to 1.2 mm.	4.0 mm
   02	500 to 1000	1.2 mm	1.5 to 1.6	4.0 mm
   03	Above 1000	-	-	4.00 mm

   Jacketed Tank for Hot Water Storage (Material of construction):

   
   

   Sr. No.	SWHS capacity in LPD	Cu (thickness in mm)		S.S. (thickness in mm)		MS coated with anti-corrosive treatment and epoxy paint stable up to 150ºC (thickness in mm)
   		Tank	Jacketing	Tank	Jacketing	Tank	Jacketing
   01	250 to 300	0.9 to 1.0	0.6	1.0 to 1.2	0.8	4.0	2.0
   02	500 to 1000	1.2	0.6	1.5 to 1.6	0.8	4.0	2.0
   03	Above 1000	-	-	-	-	4.0	2.0

   1. Insulation of Tank:

      Specification of the insulation to withstand 100 ºC should be as given below:
      
      

      Sr. No.	SWHS capacity in LPD	PUF Insulation	Glass wool / Rock wool
      01	250 to 500	55 mm	100 mm
      02	500 & above	-	100 mm

   2. Cladding of Hot Water Storage Tank:

      Aluminum sheet of 24 SWG should be used as a cladding material for system capacity 250 LPD to 2500 LPD system.  For 3000 LPD to 3500 LPD system 28 SWG GI sheet with Powder Coating should be used. Chicken mesh should be used for securing the glass wool insulation to the tank outer surface.
      Safety valve at the hot water storage tank should be provided for system above 500 LPD.