Evaluating Temperature Impact on Solar Home Systems (SHS)

Abstract

Access to electricity still lacks for a fifth of the world's population. Most of the areas are in the remote rural location. Due to the off-grid location, policies, and other social factors, the grid expansion in these areas is not economically viable. Installing Solar Home Systems (SHS) is considered to be a promising immediate solution, given that most of these areas are in the tropical region where it has the highest sun-hours in the world. SHS consists of PV modules for the energy generation, batteries for the energy storage, converters for the energy conversion, and load appliances for the energy consumption. However, its high ambient temperature can potentially harm the SHS in decreasing the performance and shortening the lifetime. The lower performance and lifetime can directly translate to have high capital expenses. Therefore a precise quantification of the performance and the lifetime is essential to all the stakeholders.

This thesis aims to evaluate and quantify the influence of temperature on the performance and the lifetime of SHS. To achieve the research goal, an integrated SHS model is proposed by considering the performance and the aging behavior of both PV modules and the batteries. Two different battery technologies: Li-ion and Lead-acid are involved in the evaluation. Moreover, the analysis was conducted for Sumba Island, Indonesia since it has great solar potential and also the potential market for the SHS. Furthermore, this work presents a comprehensive investigation of temperature impact from the PV module and battery component level to the system level.

Initial system design has been performed in which it requires a 330 Wp PV module, with a tilt and azimuth angle of 11 degrees and 6 degrees respectively, and 960 Wh of batteries to achieve the LLP of 9.5%. The simulation result of the PV component showed clearly that the PV energy yield reduces due to the higher ambient temperature is used. As for the battery, there is a converse behavior concerning the temperature impact in which an increase in temperature gives a positive effect on the capacity and internal resistance in the short term. However, in the long run, it has a severe aging rate.

By combining PV module and battery element in an integrated SHS model, it is shown that it achieves to have a 7.4% lower LLP compared to the initial sizing. However, as the aging plays a part, the LLP increases exponentially over the years and can achieve almost doubled the initial LLP. As the ambient temperature increases, it brings negative impacts for the SHS in terms of the performance and the lifetime. It results to have even higher LLP. A decreasing trend of battery lifetime is observed as the ambient temperature increases. Furthermore, it is seen that the system lifetime is limited by the battery lifetime.