Minimizing the Lead-Acid Battery Bank Capacity through a Solar PV - Wind Turbine Hybrid System for a high-altitude village in the Nepal Himalayas

Abstract

Of the estimated 1.6-2 billion people who lacked access to electricity at the end of the last millennium, millions have gained access to basic indoor lighting through off grid solar PV home systems with lead acid battery storage over the last decade. In Nepal, through government subsidy programs and INGO/NGO projects, around 350,000 solar PV home systems have been installed since 2001, mainly in remote, high altitude Himalayan communities. The author's field experience shows that within 6-24 months, 50-70% of the solar PV home systems are either not properly functioning, or not working at all. This is mainly due to substandard equipment, lack of user awareness, inability to maintain their systems, as well as the nonexistence of after sales services. Thus, an estimated 250,000 “dead”, flooded lead-acid batteries are either unsafely disposed of or lying around, posing huge potential hazards for people and the unique yet fragile Himalayan ecosystem. The research conducted demonstrates that by tapping into more than one renewable energy resource, converting the local available solar and wind resources into electricity through a solar PV - wind turbine hybrid RAPS (Remote Area Power Supply) system, the lead-acid battery bank capacity can be minimized by 57%, compared to an equivalent energy generating solar PV RAPS system, without jeopardizing, or reducing the village's load demands. This project shows that wind and solar resources are complimentary to each other over several hours in an average day. Thus, by utilizing both of the local wind and solar resources and converting them into electricity to meet the loads directly or to store into the lead-acid battery bank, it allows an average of 3-4hours longer electricity generation per day. This enables the design of smaller battery bank capacities for hybrid RAPS systems without limiting the end users’ energy services. Hence, long-term health risks to the people, as well as environmental damage to the delicate and exceptional Himalayan flora and fauna through disposed “dead” lead-acid batteries, is reduced.