Design and techno-economic analysis of an off-grid integrated PV-biogas system with a constant temperature digester for a cost-effective rural application

Abstract

This study addresses the issue of fluctuating output in cow dung-based biogas (BG) production due to temperature dependence. A thermal model is proposed and implemented in an area with abandoned BG resources, utilizing typical meteorological year (TMY) data. The model aims for constant BG output by maintaining digester temperature at 39 °C throughout the year. It is found that integrating heating with a 3100 CUM cow dung-based biogas digester (BD) increase the energy production capacity from 2.25 GWh/year to 3 GWh/year. Subsequently, three different cases are studied: standalone PV, PV-BG system, and PV-BG system with the heating arrangement, and they are scheduled using the area's TMY data, according to a strategy that can fulfil highly dynamic load curves with 690 kW peak and 264 kW average demand, as reported by the Government of India, with zero loss of power supply probability (LPSP). In the proposed case, the integration of heating reduced the PV and energy storage system (ESS) sizes by 65 % and 52 %, respectively. The current system imposes a COE of INR 2.1/kWh, which is 70 % cheap than grid electricity in the surrounding areas, with the help of proper resource estimation utilizing TMY data, integration of heating, and compressed biogas (CBG) production with energy.