The southern railway will be installing rooftop solar at Chennai Central and Basin Bridge yard. At central the capacity of the solar power plant will be 1.9 MWp and 250 kWp at Egmore station. This is the first time that the railway is installing a rooftop solar plant of mega-size. It has already installed small capacities across various stations previously.
Tamil Nadu has prepared a draft Solar Policy 2018 for the promotion of rooftop solar in the state. Until now it did not have any clarity on net-meter or gross-meter provisions. The net-meter provision allows the export of surplus solar energy to the grid and import of energy from it to meet any shortfall. The draft policy is likely to bring the clarification and the railway awaits that for its future plans for using rooftop solar. TEDA the renewable energy nodal agency of the state is also trying to promote solar energy from educational institutions.
Design of mega rooftop solar plant in the absence of Solar Policy
Chennai Central is one of the biggest railway stations in India. The 1.9 MWp plant at Chennai central has been designed in such a way that entire energy produced from it will be consumed on the premise itself. On weekends energy will be transmitted to Basin Bridge where demand is higher. This way the interaction of the rooftop solar plant with the grid will be minimum.
According to the railway, the total cost of the plant is 6.5 Cr./MW. It is because of the design that the cost is relatively high in contemporary times. For a mega size rooftop solar plant, the cost is around INR 4 Cr./MW. Railways will have to bear the additional cost of developing infrastructure to connect the Central and Basin Bridge.
Financial analysis of the solar project
With the higher cost, the payback on investment in rooftop solar will also be longer. But nonetheless, it will reduce the electricity cost of the railways. The southern railway pays INR 6.35 per unit to TANGEDCO and INR 6.67 with tax. Assuming that the base tariff escalates between 3%-5% the resultant savings over 25 years will vary accordingly
Despite a high initial cost of the rooftop solar plant, the Internal Rate of Return (IRR) and Return on Investment (ROI) will be extraordinary