Techno-economic feasibility study of using solar energy For operating sewage treatment plants

Abstract

Sewage treatment plants are the major consumers of energy throughout the world and most of the studies consider completely self-sufficient treatment plants or off-grid solar PV. This study presents the findings of the techno-economic feasibility study of using on-grid fixed tilt polycrystalline solar photovoltaic (PV) modules to generate power for operating small capacity sewage treatment plants (STP) ranging from 1 to 10 MLD. Recent ongoing 4 STP projects in Rajasthan, India is considered for the study. With fixed-tilt solar PV system, the maximum PV array capacity need to be installed is found to be 99kWp, 131kWp, 172kWp and 403kWp for 1.5, 2, 3, 8 MLD STP’s respectively. Life Cycle Cost Analysis of a base case scenario with 30 years of service life and 10% discount rate indicates that the Net Present Value (NPV) of the system comes around 3.7 Million INR, 5 Million INR, 6.5 Million INR and 15.3 Million INR for 1.5, 2, 3, 8 MLD respectively. The Internal rate of return (IRR) is found to be 18.5%, the normal payback period to be 5.4 years and Discounted Payback period to be 8 years for all 4 STP’s. Life Cycle Assessment results of the Solar PV modules indicates that the energy payback period is coming around only 1.6 years with carbon payback period of 142 days in comparison with conventional coal-based power plants. It is found that application of Solar PV in operating STP’s is highly favourable technically, economically as well as environmentally in a tropical Country like India.