Archive for July 26, 2010

Need to overcome solar inverter challenges and issues in India

Did you know that Indian made inverters typically come with a two-year warranty, while foreign inverters are generally available with a five-year warranty with AMC? It can be extended up to 10 years.

According to Dr. J. N. Roy, vice president (R&D/Engineering), Solar Semiconductor Pvt Ltd, while Indian made inverters could be mostly installed indoors, the foreign ones could be deployed both indoors and outdoors. In terms of durability, Indian inverters are expected to last at least 20 years, while foreign inverters had already proved that they can last this distance!

These limitations or challenges facing Indian made inverters were highlighted by Dr. Roy during a workshop on solar inverters, organized by the India Semiconductor Association (ISA) on 23 July, 2010, in Kolkata, India.

In terms of control, Indian inverters did not support wireless features as yet, while it is already available on foreign inverters. In terms of design and support, while Indian inverters were generally custom made, the foreign inverters were standardized and had simulation support. As for efficiency, while Indian inverters had efficiency less than 94 percent, their foreign counterparts boast efficiency higher than 97 percent — a telling differentiator.

In terms of battery voltage, Indian made inverters were available supporting 24V, 48V, 96V, 120V and 240V, respectively. Foreign made inverters support 24V and 48V as fixed. They are light and compact, as compared to large and heavy for locally made inverters. While Indian inverters are generally EC and TUV approved, the foreign inverters are EC and TUV approved and UL listed, respectively.

Dr. Roy also highlighted the challenges faced by power control units (PCUs) in India  and touched upon the desired features of inverters.

Roy said that inverters today have a mean time between failure (MTBF) of less than 10 years. The computed MTBF above 100 years has already been achieved in recent modular solar inverters. Incidentally, solar PV panels easily meet the 25 years life requirement.

He provided case studies, such as off-grid DC couple system, off-grid AC couple system, and off-grid pump systems. In the off-grid pump systems, there were no batteries/grid as buffer. Power consumption can be matched with power generation by controlling speed of the pump. He advised making power generation as close as possible to maximum power.

Dr. Roy provided several examples of inverters. While multi string inverter and central inverter were examples of classification based on installations, solar inverters with and without transformer were examples of classification based on topology. Read more…

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