Off-grid solar energy storage system with hybrid lithium iron phosphate (LFP) and lead-acid batteries in high mountains: a case report of Jiujiu Cabins in Taiwan

TL;DR

The paper reports a case study of an off-grid solar energy storage system at Jiujiu Cabins, Taiwan, highlighting a 2021 outage due to aging lead-acid components and interlinked systems. It documents a detailed on-site survey and a 2021 upgrade that reorganized the solar power lines, replaced inverters, and introduced eco-friendly LFP batteries to form a hybrid ESS. The work presents the current energy architecture and EMS data, and outlines a future plan to replace remaining lead-acid, expand PV and ESS capacity, and develop a cloud-native EMS. The findings demonstrate practical viability of a green, hybrid ESS approach for remote high‑altitude huts and provide a blueprint for similar installations.

Abstract

Mountain huts are buildings located at high altitude, offering a place for hikers and providing shelter. Energy supply on mountain huts is still an open issue. Using renewable energies could be an appropriate solution. Jiujiu Cabins, a famous mountain hut in Shei-Pa National Park, Taiwan, has operated an off-grid solar energy storage system (ESS) with lead-acid batteries. In 2021, a serious system failures took place, leading to no electricity. After an detailed on-site survey, a reorganization and repair project implemented, the energy system came back to operate normally. Meanwhile, a eco-friendly lithium iron phosphate battery (LFP battery) ESS replaces part of the lead-acid battery ESS, forming a hybrid ESS, making a better and green off-grid solar ESS. In this case report, the energy architecture, detailed descriptions, and historical status of the system are provided. An on-site survey of the failed energy system, a system improvement project, and future plan are listed.

Figures (9)

• Figure 1: Entrance of Jiujiu Cabins (2021).
• Figure 2: Aerial photography of Jiujiu Cabins (2021). The lodge complex. It includes Chengkung Yurts, a restaurant (reception room), Longmen Inns, a machine room, toilet, etc., all of which are separate buildings. (Photographer: Yu-Chun Lin)
• Figure 3: Energy architecture of Jiujiu Cabins (2021). The off-grid solar ESS of Jiujiu Cabins is composed of two independent power supply systems combined with the same hybrid ESS. This ensures that two PV arrays can generate electricity and supply two sets of 110 V$_\mathrm{AC}$ loads. The ESS is a newly added LFP battery system, which is used in conjunction with the existing lead-acid battery ESS to form a hybrid ESS. An additional backup power input terminal is also added, allowing for the connection of an external generator as a backup power source.
• Figure 4: Ground-mounted PV system 1 PV array 1 is a ground-mounted PV system with a power generation capacity of 2.1 kW$\mathrm{_p}$. It is composed of 28 75W$\mathrm{_p}$ solar modules.
• Figure 5: Ground-mounted PV system 2 PV array 2 is a ground-mounted PV system with a power generation capacity of 3.2 kW$\mathrm{_p}$. It is composed of 40 80W$\mathrm{_p}$ solar modules.