Specification (Minimum Technical Requirements laid down by MNRE for ensuring quality aspects of Solar Water Heating Systems being installed)

The FPC based systems will be from BIS approved manufacturers and ETC from MNRE approved manufacturers/suppliers. The Systems will have the following minimum requirements for installation:

General Requirements

  1. System installed in high windy area will be well grouted/ clamped with collectors installed in a way that it is able to sustain the highest wind pressure of that area.

  2. All the collectors will be south facing inclined at suitable angle to give best performance in winter

  3. There will not be any shadow falling on the collectors from nearby structures or of other collectors in front or back row

  4. Hot water pipe lines of any kind in colder regions will be fully insulated from the point of drawl of water from tank to delivery points. In other regions also care will be taken to avoid heat losses from pipelines.

  5. System will be installed nearest to the point of hot water usage to avoid longer pipeline & higher heat losses.

  6. Where water quality is bad either FPC based systems with Heat Exchanger or ETC based systems will be installed.

  7. The workmanship & aesthetics of the system will be good and it should be visible to anybody

  8. Air vent pipe, make up water and cold water tanks will be installed as required for smooth functioning of the system

  9. There won’t be any leakage observed in the system from tanks/ collectors/ pipelines

  10. No electric back up will be provided in hot water storage tank at places where electric geysers are already installed. At places where electric geysers are not installed, electric back up could be provided in upper portion of storage tank, if necessary. Other option is to have an instant/ small geyzer in bathroom with outlet of solar hot water storage tank connected to its inlet and thermostat set at say 40 C. This will help consuming less amount of electricity during non-sunny days.

Technical Requirements

Flat Plate Collectors : ISI mark (2 sq. m. absorber area for 100 litre tank capacity system in colder region and 125 litre for other regions)

Evacuated Tube Collectors/ Heat pipes

Type of tubes : 3 layer solar selective (Inner layer of copper coating should be visible). Detailed specifications of tubes will be as per the guidelines laid down by MNRE empanelment of manufacturers of ETC based systems & made available at MNRE website.

No. of tubes/ Absorber Area : 1.50 sq. m. of absorber area for 100 litre tank capacity system. Absorber area will be calculated as follows:
Area in Sq. Meter = 3.14 X No. of tubes X Radius in Meter X Length in Meter.

Accordingly, 14 tubes of Dia : 47 mm & length : 1500 mm and 10 tubes of Dia 58 mm & length : 1800 mm will be required for each 100 lpd system. For higher capacity systems, the no. of tubes calculated as per above could be slightly less. However,the minimum absorber area will not be less than that given in MNRE Circular No. 22/5/2009-10/ ST dated 02-03-2010.

Procurement: From reputed supplier (Details of supplier to be provided)

Storage Tanks, Piping, Support structure etc ( To be all indigenous & not imported)

Inner tank material : SS 304 or 316 grade min/ MS or any other material with anticorrosive coating for hard water with chlorine contents.

Inner tank thickness : For SS minimum thickness will be 0.5 mm when using argon arc or metal inert gas for welding & 0.8 mm when using other type of welding. For MS it will be 1.5 mm. No leakage under any kind of negative or positive pressure of water will be ensured.

Inner tank welding :TIG / Seam/ pressurized weld (Open arc weld not permitted )

Storage tank capacity :Not less than system capacity. In case of ETC based system, volume of tube & manifold not to be included in tank capacity.

Thermal insulation of : Minimum 50 mm thick CFC free PUF having density  of 28-32 storage tanks kg/ storage tanks cu.m for domestic systems and 100mm thick Rockwool of 48 kg per cu. m for other systems. For colder regions, it will be 1 ½ times atleast. In case of higher desity insulations, the thickness may reduce proportionately.

Thermal insulation of : Minimum 50 mm thick rockwool or 25 mm thick PUF on GI pipes. For colder regions, hot water pipes it will be 1 ½ times atleast. In case of composite pipes, it will depend on region to region. For higher density insulations, the thickness may reduce proportionately.

Outer cladding & Frames :Al/ FRP or GI powder coated. MS may also be used with special anti-corrosive protective coatings. Thickness of sheets will be strong enough to avoid any deformation the cladding.
Valves, cold water tank, vent pipe,: Of ISI mark or standard make
heat exchanger,make up tank& instruments

Support structure for Collectors: Of non corrosive material or have corrosion resistant protective coating. They will be pipng, tanks etc strong enough to sustain their pressure during the lifetime of system.

An undertaking will be given by the manufacturer/supplier confirming to above requirements. The manufacturer will also provide the detailed specifications of each and every part of his system to the beneficiary along with O&M Manual.