Rooftop PV Systems-Do they really make commercial sense?
Apart from promoting the utility scale solar power projects, Government of India took a target of 100 MW of roof top systems connected to the 440V or 11 kV to feed tail end electricity and reduce the transmission and distribution losses. One of the major advantages in the roof top systems is that they reduce the DG based captive power generation, especially in case of commercial buildings. If we consider 30% captive power generation in these commercial buildings, the average cost of power to these consumers is about 8.5 Rs/kWh, this is the point where the roof top systems make commercial sense. But do they really have roof top space to accommodate the solar power at their roof?. The vertical high rise glass buildings which are energy guzzlers hardly have any rooftop space for solar power systems. The buildings in tier 2 and tier 3 cities can have buildings which are much more horizontally spreads are good case for accommodating the rooftop systems. Although the glass facade in case of high rise buildings can be of solar PV as building integrated PV systems, however they extract very less energy due to the limitation of solar energy falling in a perpendicular fashion on them. Our limitation is that we design buildings and then think of solar to integrate with the existing design.
In-order to achieve its solar portfolio obligations New Delhi Power Limited has already proposed a rooftop PV programme with a target of 50 MW for 10,000 customers in the first phase of JNNSM. The experiences in Germany and California on roof top systems show a great relief to the distribution losses. Adopting the rooftop system in India as well is likely to provide a great relief to the Indian utilities as well in terms of reduced distribution losses. While the cost of utility scale projects have already come down to about Rs. 8 Cr./MW, it is important to develop market based mechanisms through which the cost of roof top systems can be brought down. Current rooftop systems cost almost Rs. 16-20 Cr./MW, due to the higher labour, transaction and implementation costs. The economics of rooftop systems makes sense only to the consumers who have high dependency on the captive DG sets, which they use in the event of grid failure. It is important to have more generic guidelines for grid integration, connectivity, net metering, etc for large scale deployment of roof top systems.