Solar radiation data was updated through a joint project between National Institute of Solar Energy (NISE) of the Ministry and IMD from 23 locations, monitoring solar irradiation parameters. The updated data has been posted on the Ministry’s website and is also available in IMD/MNRE Handbook of Solar Radiation.
Cooperation between NREL (USA) and NISE of the MNRE has provided data which can be accessed in CD ROM form. These data sets contain high resolution solar resource maps in the form of NREL Solar Resource Maps and Toolkit for Northwest India.
MNRE has taken an initiative to augment Solar Radiation Resource Assessment Stations (SRRAs) at sites of high potential for solar power generation, which is being implemented by NIWE. Around 51 stations have been set up that use high quality, high resolution equipment/instruments to assess and quantify solar radiation availability along with weather parameters to develop a Solar Atlas. Implementation of the project started in February 2011 and all stations have already been installed, completed and commissioned. The monthly average (daily) wise data received from each SRRA station is available with NIWE.
Solar Insolation data made available by NASA under its Earth Science Enterprise program is also commonly used by the developers.
The India Meteorological Department (IMD) under the Ministry of Science & Technology is the nodal agency for setting up/monitoring weather stations.  There are around 45 radiation observatories. The measurements for global solar-radiation, diffused solar radiation and direct normal incidence is being carried out at 39, 23 and 21 locations respectively across India.

Till now availability of site specific data has been a challenge and therefore developers and financial institutions have been using macro level data sources like NASA. Going forward as more micro level data becomes available; it would be better for developers to source and use this data for project planning.

Solar Radiation Resource Assessment

Ministry of New and Renewable Energy (MNRE) sanctioned in 2010 to National Institute of Wind Energy (NIWE), formerly Centre for Wind Energy Technology (C-WET), Chennai, a mission mode project – the SRRA – to set up the world’s largest net work of solar radiation resource assessment stations all over the country to overcome the deficiencies in the availability of investor grade ground measured solar radiation data crucial for planning and implementation of solar power projects . In the first phase, 51 SRRA stations were set up by October, 2011, in 11 States 1 Union Territory and in the second phase, 60 SRRA stations (in 28 states and 3 UTs) and 4 Advanced Measurement Stations (AMS) by June,2014. NIWE, Chennai has also established 6 SRRA stations in Maharashtra for Maharashtra Energy Development Agency (MEDA), Government of Maharashtra under consultancy mode. The SRRA project envisages assessment and quantification of solar radiation, data processing, quality of data, modeling and making of solar atlas of the country (Click here for the Indian Solar Radiation Atlas), besides the collection and analysis of solar and meteorological data, crucial for planning and implementation of solar power plant.

srra

A typical SRRA station consists of two towers of 1.5 m and 6 m tall each for measuring solar and meteorological parameters respectively. The 1.5 m tall tower houses a solar tracker equipped with Pyranometer, Pyranometer with shading disc and Pyrheliometer to measure global, diffuse and direct irradiance respectively. The 6 m tall tower houses instruments for measuring ambient temperature, relative humidity, atmospheric pressure, wind speed & direction, rain fall and a state of-the-art data acquisition system. The solar sensors are traceable to the World Radiometric Reference (WRR) and the meteorological sensors are traceable to World Meteorological Organization (WMO). Each SRRA station is totally powered by solar panels. A trigger switch is also installed at each SRRA station to track the cleaning status of the SRRA stations on a daily basis. Data is sampled every second and averaged over a minute and transmitted to the Central Receiving Station (CRS) established at NIWE through GPRS mode.

The AMS is set up for quantification of attenuation of solar radiation due to the presence of aerosols in the atmosphere and for the measurement of the reflectivity of the earth (Albedo), incoming long wave radiation and atmospheric visibility for research and developmental activities. The four AMS installed are at National Institute of Solar Energy (NISE), Gurgaon, Indian Institute of Engineering Science and Technology (IIEST) – Howrah, Pandit Deendayal Petroleum University (PDPU), Gandhi Nagar and Prathyusha Institute of Technology and Management (PITAM), Tiruvallur. GIZ, Germany is providing technical assistance to attain and sustain high quality standards on quality measurements, checks, generation of reports and Solar Atlas of India. The applied quality control on the solar radiation data is based on Baseline Surface Radiation Network (BSRN) rules by the World Meteorological Organization (WMO), elaborated by the Management and Exploitation of Solar Resource Knowledge (MESOR).

NIWE has launched the Indian Solar Radiation Atlas, with 3 km X 3 km spatial resolution, on 03.06.2015, providing details of solar resources at any location. At present annual average values of GHI, DNI and DHI are provided along with the administrative details pertaining to the 3 km X 3 km grid. 1 to 3 years quality ground measured solar data has been used for geographical adjustment and validation of the long term (1999-2014) data from Meteosat-5 and Meteosat-7.