Helexia, a subsidiary of French renewables company Voltalia SA (<a href="https://live.euronext.com/en/product/equities/FR0011995588-XPAR" target="_blank">EPA:VLTSA</a>), has put on stream 28 rooftop solar photovoltaic (PV) plants in Romania with a combined capacity of 12.8 MW, the parent company said on Thursday.