A Comparative Performance Analysis of a 1 MW CIS PV System and a 5 kW Crystalline-Si PV System under the Tropical Climate of Indonesia

Despite being a tropical country with great potential for solar power, knowledge about the actual performance of photovoltaic (PV) systems in Indonesia remains limited. In this paper, using 5-minute resolution data from 2016 to 2018 obtained from a 1 MW Copper Indium Selenide (CIS) and a 5 kW crystalline silicon (c-Si) PV plant in West Java, we aim to answer the question of how a CIS PV plant performs and degrades in Indonesia’s tropical climate and how it compares to a PV system that contains c-Si technology. The methodological approach used includes performance analyses of these PV systems according to IEC standard 61724 and an investigation of the degradation rate using NREL/RdTools. The following results were derived from the analyses: the total annual H_i was 1500 kWh/m² or around 4.2 kWh/m²/day. The daily-averaged performance ratio, PR, was 91.7 % ± 4 % and 87.4 % ± 7 % for the CIS system with string inverters and a central inverter, respectively. The mean PR of the CIS systems was 12 % higher than that of the c-Si system, which was 79.8 %. Concerning the final yield, Y_f, the CIS system with a mean Y_f of 3.85 kWh/kWp outperformed the c-Si system by 14 %. The CIS system degraded by 1.53 % per year, which is less than the c-Si system with a degradation rate (R_d) of 3.72 % per year. From these results, it can be concluded that, in this case, CIS technology performs better than c-Si in Indonesia’s tropical climate. Uncertainties in the calculation and high values of R_d could be areas for further investigation.

Degradation; Indonesia; Performance; PV systems; Tropical climate

The first PV system applications in Indonesia can be traced back to 1978 and the installation of a  5 kWp solar water pumping system (Dasuki et al., 2001). Various other projects then followed, such as a solar home systems (SHS) pilot project (Reinders et al., 1999), desalination plants, basic medical applications, remote televisions, and water pumping systems (Veldhuis & Reinders, 2015). A large SHS demonstration project with a total capacity of 50 MWp was launched in 1994 (Veldhuis & Reinders, 2015), and the first urban PV system was introduced in 2003 (Ministry of Energy and Mineral Resources, 2012).

Since then, many other PV systems have been constructed and created employment (Elfani, 2011). However, it is only relatively recently that Indonesia has gained experience in the performance of PV systems (Kunaifi & Reinders, 2018), and it continues to be in the research and demonstration phase (Veldhuis & Reinders, 2015). To date, Indonesia has 12 utility-scale PV plants in operation, mainly for off-grid or industrial applications. The dominant PV technology applied is typically crystalline silicon (c-Si) technology.

The PV market in Indonesia is emerging and is expected to grow over the coming years across the vast expanse of Indonesia’s archipelago. The factors driving its growth include Indonesia’s unique geography, comprising six large and more than 17 thousand smaller islands. This type of geographical factor presents a challenge in terms of extending the conventional power grid to reach the whole of the country’s population of more than 260 million. The other motivations for solar electrification in Indonesia include, among others, the increasing demand for electricity (around 5.5 % annual growth) and economic growth of 5 % per year.

PV systems are suitable for use on the large islands (urban areas), particularly with respect to increasing the quality of the power supply (Nazir et al., 2016) as Indonesia is characterized by the relatively low reliability of its electricity supply (Kunaifi & Reinders, 2018). Meanwhile, on the smaller islands and in more remote areas, PV systems could play a significant role in providing electricity to local people who have not had it before, replacing fossil-fuel-generated electricity with renewables, and increasing the electrification ratio (PLN, 2018).

It is essential to monitor the operation of a PV system in order to identify performance trends. Monitoring data is also crucial for the localization of potential faults and to enable a comparison of PV system performance against design expectations and guarantees and between the different configurations and locations (The International Electrotechnical Commission, 2017). However, most PV systems in Indonesia are not monitored, with only a few equipped with basic monitoring systems. Accordingly, we have limited knowledge about the actual performance of PV systems operating under real environmental conditions in Indonesia. The two PV systems presented in this paper are among the few that are monitored.

Figure 1 Aerial view of the 1 MW PV plant in Cirata, West Java, Indonesia (Photo: PJB Cirata).

In September 2015, PT. Pembangkitan Jawa-Bali (PJB), a subsidiary of PLN, Indonesia’s state-owned utility company, commenced its entry into the PV business. PJB is a power generation company that operates mainly in Java and Bali, which are the islands with the largest and densest electrical power systems in Indonesia. PJB constructed and now operates and maintains nine power plants with a total capacity of more than 7 GW (PJB, 2019). Among those in operation by PJB is a 1 MW PV system located in the province of West Java, which at the time of its construction was the largest PV system on the island of Java (Figure 1). At the same location, PJB also installed other, smaller PV systems. After three years of operation, we can now, for the first time, analyze the monitoring data from the PV systems in West Java.

In this paper, we therefore seek to answer the following questions:

·      How is PJB’s 1 MW CIS-based thin-film plant performing, and how has it degraded in Indonesia’s tropical climate?

·      How do its performance and degradation compare to that of a 5 kW crystalline (c-Si) plant at the same location?

The motivation for analyzing the performance and degradation of PV systems lies in the fact that the long-term performance and stability of PV plants have a significant impact on the economics of such projects.

Besides performance, degradation is one of the most critical characteristics to consider in the solar PV business. Degradation describes the rate at which a PV module experiences a decline in output. The degradation rate, R_d, is therefore the rate at which the PV performance of a module decreases per year. R_d is an important measure for comparing the actual performance of PV systems against the PV performance warranty issued by the module manufacturer with respect to nominal power.

PV cells degrade (Meyer & van Dyk, 2004); however, the rate of degradation differs from one PV plant to another. Over the course of a 25-year operating life, a 20 % decline is considered a failure. Assuming linear degradation, an R_d greater than 0.8 % per year can be regarded as a problem (John et al., 2018). For a high-efficiency module, however, 50 % degradation may be acceptable (Jordan & Kurtz, 2013). Using data from outdoor field testing, the long-term behavior and lifetime of PV modules, including their degradation, can be quantified.

We compared the performance and degradation rate of a 1 MW CIS PV system and a 5 kW crystalline-Si PV system operating in the real tropical climate of Indonesia. Concerning the Y_f, the CIS system outperformed the c-Si system by 14 %. The daily-averaged PR of the CIS system was 89.6 % (mean PR of the central and string clusters), which is 12.2 % higher relative to the PR of the c-Si system of 80 %.

Based on monitored P_ac, the R_d of the PV systems in Cirata at the module level was high. The CIS system degraded by 1.53 % per year, while the R_d of the c-Si system was 3.72 % per year. However, at the system level, the R_d values were within acceptable boundaries. By considering the other technical performance indicators, it can be concluded that CIS technology performs better than c-Si in Indonesia’s tropical climate. However, there may be some uncertainty with respect to the calculation of the R_d. Such uncertainties are caused by soling and the relatively short two-year monitoring period. 

We appreciate the financial support from the Indonesia Endowment Fund for Education (LPDP) and the expert support from Advanced Research on Innovations in Sustainability and Energy (ARISE) of the University of Twente. Thanks to COST Action PEARL PV for the Short Term Scientific Mission (STSM) grant at Eurac Research in Bolzano, Italy.

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