photovoltaics Why grid connected PV can be optimal The impact of utility scale photovoltaic facilities on grid stability can be favourable if done properly. ESI Africa spoke with vice president of product management for First Solar, Mahesh Morjaria, to see how this is achieved. T he increasing cost competitiveness of solar photovoltaic (PV) technology (in South Africa’s Renewable Energy Independent Power Producer Programme PV prices fell from an average of R2.75/kWh in the first round to an indexed price of R0.88/kWh in the third round using 2011 as the base year) is seeing this energy carrier evolve in two directions globally. One is the proliferation of distributed solar PV on rooftops as owners of commercial buildings, businesses and homes see the benefits of offsetting their use of grid power. The second is the increase of utility scale grid connected photovoltaic systems. The global grid connected PV capacity has already reached over 100 GW. However, in many of the distributed rooftop solar applications all that happens is that the PV produces active power when the sun is shining. “The problem is that this does nothing for the voltage or reactive power control on the distribution network,” Morjaria says. A typical situation is where a home or commercial building at the end of a feeder system installs some PV; there could be times when it produces more power than is required and this comes onto the local distribution network. Feeder networks were not designed to accommodate distributed power. Typically at the utility end of the local network the voltage is high enough so that by the time it reaches the loads at the other end it remains within the regulated range. With a PV power supply at the end of the feeder, the result is that the neighbouring homes and businesses could experience fluctuating voltages that are higher than those stipulated for the network, which has an impact on electrical equipment being used. (It should be noted that this scenario arises in countries where net-metering is allowed; in South Africa no national regulation exists which enables this. Some municipalities in the country have piloted the concept but it is not widely accepted yet.) In contrast, utility scale PV facilities have sufficient voltage and power factor control capability to ensure they contribute to grid stability. Grid codes ensure this is so. “Most grid codes are First Solar’s Mohammed bin Rashid Al Maktoum solar park in Dubai. ESI AFRICA ISSUE 4 2013 5