Nearly half of the 1,000-Mw capacity addition envisaged under the first phase of the national solar mission is likely to miss the commissioning schedule, with technical and equipment availability issues hampering progress in project execution.

Developers are required to commission these projects by May next as per the terms of the power purchase agreement (PPA).

In case of default on PPA, they would be liable to pay penalty. Apprehensive that they could fail to meet the committed schedule on power supply, developers have approached the nodal ministry for extension.

?Solar thermal power project developers have sought extension of 6-12 months for completing projects,? said Tarun Kapoor, Joint Secretary, ministry of new and renewable energy (MNRE), the nodal agency for the implementation of the solar mission.

The government has envisaged 20,000 mw capacity addition by 2022 under its flagship Jawaharlal Nehru Nation Solar Mission (JNNSM) programme. The scheme is being implemented in three phases.

In the first phase (2009-13), a total of 1,000 mw capacity is being developed, of this 470 mw is based on solar thermal technology. Total investment requirement for solar thermal projects is estimated at R6,000 crore.

Most of the developers had planned their projects based on satellite data relating to radiation. But a significant divergence from those data has been encountered during execution, necessitating re-engineering of the project.

?When bidding was held for allocation of these projects, there were no ground stations to measure solar radiation. They (bidders) had to rely on satellite data,? Kapoor told FE.

He added: ?But satellite data are not very reliable and have to be corroborated by ground data.? Since then, the MNRE has set up about 51 solar radiation stations. Besides companies have also set up their own stations.

The chronic shortage of a critical material, Heat Transfer Fluid (HTF) which is used to carry solar heat for converting water into steam, has further complicated things for developers.

There are only two suppliers of HTF globally and there is a long queue. That is the reason Indian solar power developers are facing delay in supply of the critical fluid, according to industry experts.

?Our technical committee has visited these projects a couple of days ago and is expected to submit its report soon,? Kapoor said.