India has inaugurated the National Primary Standard Facility for Solar Cell Calibration at the CSIR–National Physical Laboratory (NPL), marking a major advancement in the country’s renewable energy and scientific measurement infrastructure, Union Minister of State (Independent Charge) for Science and Technology Dr Jitendra Singh said on Monday, 5 January.
The facility, known as the Solar Energy Complex, has been developed in collaboration with Germany’s Physikalisch-Technische Bundesanstalt (PTB), the German national metrology institute. It houses a laser-based Differential Spectral Responsivity (L-DSR) system that achieves the lowest measurement uncertainty globally at 0.35 per cent (k=2) for reference solar cell calibration.
The Solar Energy Complex was inaugurated along with the National Environmental Standard Laboratory during the 80th Foundation Day celebrations of CSIR-NPL.
A national facility for primary solar cell calibration
Officials said the Solar Energy Complex functions as India’s National Primary Standard Facility for Solar Cell Calibration, providing world-class primary calibration services for photovoltaic (PV) cells. Accurate calibration at this level is critical for reliably assessing solar cell efficiency, performance and durability.
Until now, Indian solar manufacturers and developers depended on overseas laboratories for such high-precision calibration. With the commissioning of the new facility, India joins a select group of countries with domestic primary photovoltaic calibration capabilities.
Describing the Solar Energy Complex as a “future-ready facility”, Dr Singh said it places India among global leaders in photovoltaic measurement standards.
He added that the facility would reduce India’s dependence on foreign certification agencies, save foreign exchange, shorten turnaround time for calibration, and enhance investor confidence in the country’s rapidly expanding solar sector.
German metrology expertise through PTB collaboration
The Solar Energy Complex has been developed in collaboration with PTB, one of the world’s most respected authorities in precision measurement and calibration.
PTB’s involvement enabled the transfer of high-precision calibration technology to India. The German institute itself operates one of the few laboratories globally capable of primary reference solar cell calibrations traceable to international measurement standards.
Officials said the collaboration ensures that calibration results produced at CSIR-NPL are internationally comparable, strengthening the credibility of Indian solar products in global markets.
Laser-based L-DSR system explains the precision edge
At the core of the Solar Energy Complex is the laser-based Differential Spectral Responsivity (L-DSR) system, a cutting-edge measurement apparatus used to evaluate how reference solar cells respond to different wavelengths of light.
Unlike conventional broadband measurement techniques, the L-DSR system uses laser-based spectral measurements, allowing significantly higher precision. Measurement uncertainty refers to how accurately a system determines the true response of a solar cell.
At an expanded uncertainty of 0.35 per cent (k=2), the system provides approximately 95 per cent confidence that the true value lies within ±0.35 per cent of the reported measurement — a level of precision among the best achieved globally by photovoltaic calibration laboratories.
India joins global photovoltaic standards network
Before the establishment of the Solar Energy Complex, India relied on foreign National Metrology Institutes such as PTB (Germany), NREL (United States), AIST (Japan) and TIPS (China) for primary solar cell calibration.
With the new facility, India now joins this group as a laboratory aligned with the World Photovoltaic Scale (WPVS), enabling domestic traceability to international photovoltaic measurement standards.
Environmental standards facility also inaugurated
Alongside the Solar Energy Complex, Dr Singh also inaugurated the National Environmental Standard Laboratory, the world’s second such facility.
Calling it a critical step towards strengthening India’s environmental governance framework, Dr Singh said, “Reliable, India-specific calibration and certification of air pollution monitoring systems was long overdue and would now enable transparent, traceable, and accurate environmental data.”
He said the laboratory will support regulatory bodies, industries and startups by ensuring pollution monitoring instruments are tested under Indian climatic conditions, improving policy enforcement under programmes such as the National Clean Air Programme.
Science reforms and CSIR-NPL’s legacy
Dr Singh said science and technology reforms will be key drivers shaping India’s socio-economic future, describing premier scientific institutions as “monuments of 20th and 21st century India”.
He noted that CSIR-NPL was operational even before Independence and later became an integral pillar of India’s post-Independence scientific architecture. CSIR itself predates independent India, making NPL one of the earliest among the Council’s 37 laboratories.
Speaking to reporters, Dr Singh said CSIR-NPL had been mentored by leaders including Dr Syama Prasad Mukherjee and Sardar Vallabhbhai Patel.
“For decades, half the nation synchronised its watches with the atomic clock housed at NPL,” he said, highlighting the laboratory’s role in establishing Indian Standard Time.
Dr Singh added that Indian scientists are no longer working in isolation within laboratories but are increasingly central to national expectations and aspirations.
