According to reports, the increasing share of Vacuum Tube Collector (VTC) systems imported to India took the Indian government to specify the standard requirements for evacuated solar collector tubes for non-concentrating solar thermal collectors and related storage tanks.
The industry and the manufacturers welcomed the publication of the new standards, released for public debate in early March 2013, as the aim of the Indian Ministry of New and Renewable Energy (MNRE) is to keep low-quality systems out of the sector.
“Because vacuum tubes still continue to be imported, there was a need to keep an eye on the quality,” says MNRE’s Joint Secretary, Tarun Kapoor. “This will also increase customer confidence, as systems will perform throughout their lifetime and provide the desired output.”
The MNRE had been working for a long time on devising new standards which now are imposed to manufacturers importing the tubes to show reports of testing laboratories from the country of origin. These reports will be approved by agencies like the Regional Test Centre.
The MNRE has released three sets of standards: Evacuated tube standards (MNRE STD 01:2013), Storage tank standards (MNRE STD 02:2013) and System standards (MNRE STD 03:2013).
Storage tanks with a capacity of up to 500 litres can be tested every two years either at an approved laboratory or at the manufacturer’s laboratory. Tests for tank capacities of more than 500 litres are to be carried out as per agreement between the manufacturer and the user. The selective coating of the tube is to have an absorptivity of 0.92 or higher at AM 1.5 and an emissivity of less than 0.07 when tested. A label on each evacuated solar tube, showing the manufacturer’s name or logo, the batch number and the date of production is also required.