What is the primary performance parameter for an evacuated tube collector?

The thermal efficiency, represented by an efficiency curve and coefficients (η₀, a₁, a₂) determined through the Thermal Performance Test as per Annex A.

Does this standard apply to the entire solar water heating system?

No, this standard is specific to the evacuated tube collector component only. The complete system is typically covered by standards like IS 12933.

What is the purpose of the stagnation resistance test?

To ensure the collector can withstand the high temperatures reached under maximum solar radiation with no water flow, simulating a power outage or no-use condition without degradation or damage (Clause 5.7).

Is this standard harmonized with any international standard?

Yes, it is largely based on and references the international standard ISO 9806 for test methods for solar collectors.

IS 16568

: 2016

Evacuated tube solar collectors - General requirements and methods of test

CurrentSpecializedSpecificationBIMMEP · Solar and Renewable Energy Installations

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This standard specifies the requirements and test methods for evacuated tube solar collectors (ETCs) used for heating fluids, typically in solar water heating systems. It outlines the material, constructional, safety, and performance criteria to ensure the quality, durability, and thermal efficiency of the collectors. The tests included are designed to verify performance under various operating and extreme conditions.

Specifies requirements for general characteristics and methods of test for evacuated tube solar collectors.

Quick Reference Values

Minimum test pressure for collector1.5 times the maximum operating pressure, but not less than 1.0 kg/cm²

Internal thermal shock test cold water temperatureNot more than 25 °C

Rain penetration test spray rate0.05 l/(s.m²)

Impact resistance test ball mass50 g (hardened steel)

Impact resistance test drop height1.0 m

Absorber coating absorptance (α)≥ 0.92

Absorber coating emittance (ε)≤ 0.08

Key Formulas

η = η₀ - a₁ * (T*m) / G - a₂ * G * (T*m)² — Collector efficiency formula, where T*m = (Tm - Ta)

Practical Notes

The thermal performance coefficients (η₀, a₁, a₂) are critical for system design and performance simulation. Always source these values from the official test report.

Pay close attention to the stagnation temperature resistance of the collector to ensure connected components like piping and safety valves are rated appropriately.

Verification of certification against this standard is often a prerequisite for availing government subsidies or incentives for solar thermal installations.