1. Introduction
For the last few decades, global energy demand has been slowly increasing. Although fossil fuel resources are reducing, global energy demand is rising rapidly. The use of renewable energies is a thoughtful approach and solution to the energy demand. Renewable energy is one source of sustainable and alternative energy that has grown in popularity in today’s world. Solar, wind, hydro, geothermal, and biomass are only a few examples of renewable energies. Solar energy is one of the most effective and important renewable energies [
1]. Solar energy is abundant in almost every region of the planet and has been used to generate energy for several years. Using PV modules, solar energy can be converted into a valuable source of electricity [
2]. Since it is reliable and environment-friendly, PV systems have been installed for energy generation in different parts of the world. Additionally, due to the continuous reduction of fossil fuels, PV systems have the ability to become a significant source of energy generation in the future. Energy generation from PV systems has grown rapidly across the world, with a total annual of 50 GW in 2015 [
3]. The amount of PV energy generated depends on many factors. Solar radiation, PV cell or module technology, and outside temperature are considered the main factors that influence energy generation. Japan is one of the PV energy producers in the world.
The capacity of PV systems installed in Japan till 2017 is 42 MW [
4]. PV energy has been increased in Japan in response to the global trend of growing environmental awareness. The new Feed-In-Tariff (FIT) system of Japan was released in July 2012 [
5] to accelerate the promotion of renewable energy sources such as solar power generation, wind power generation, geothermal power generation. Since then, grid-connected photovoltaic (GCPV) systems have increased rapidly. Recently, various literature studied the feasibility of the GCPV system using simulation software. The study [
6] compared different simulation software such as PV SOL, PV GIS, Solar GIS, and SISIFO to analyze the performance of a grid-connected PV system. The study [
7] uses PVsys software to analyze the performance of an 8.2 kWp GCPV in the Patagonia Region.
The PV module manufacturers report the performance of their PV modules in datasheets. These documents rely on the data that are collected under standard testing conditions (STC): 1000 W/
, 25 °C cell temperature, and Air Mass 1.5 (AM1.5) [
8]. This cannot be trusted in real PV systems, as most of the time, temperature and air mass differ from one location to another, and PV cell temperatures could reach much higher values. However, STC does not give any information about the actual performance of a particular PV system in real life and under actual weather conditions [
9]. To better evaluate the actual performance of the GCPV system, the impact of different parameters such as temperature, shading [
10], solar irradiance [
11], dust [
12], solar tracking system [
13], inverter efficiency [
14], and panel material [
15] have been investigated. In the study [
16], the influence of different PV cell spacings on the performance of the photovoltaic system was identified. The energy, environmental, and economic performance of an urban community hybrid distributed energy system was investigated [
17]. The paper [
18] studied the role of energy and environmental indicators for the power grid. In the study [
19], a photovoltaic array cleaning system design and evaluation were discussed. The result shows that using a cleaning system could increase the PV array energy generation by about 15%. Understanding the effect of weather conditions in outdoor exposure provides valuable input to PV energy projects at the planning and financing stages [
20].
Since the performance of the GCPV system under STC cannot be trusted, this paper aims to evaluate the GCPV system performance under actual weather conditions. The results show a significant decrease in energy generation. In 2019, while a total annual of 48,521 kWh of energy was expected to be generated, 38,071 kWh was generated and injected into the utility.
The main contribution in this study as follows:
Measure the actual energy generation acquired from the inverter of the GCPV system installed in Tochigi prefecture, Japan, over the year 2019.
An analytical model with solar irradiation obtained from Power Data Access Viewer (PDAV) was developed to investigate and evaluate the efficiency of the GCPV system monthly and annual energy generation by comparing the simulated and measured energy acquired from the inverter.
Analyze the techno-economic performance of the GCPV system after eight years of energy generation under actual weather conditions.
The structure of this paper is as follows:
The second section presents the current status of the FIT system in Japan, changing the rate over the years.
Section 3 describes the GCPV system location, data collection, and PV system configuration.
Section 4 presents descriptions and definitions of the technical and economic performance analysis of the GCPV.
Section 5 shows the technical and economic performance analysis results of the GCPV system. The correlation coefficient between the simulated and measured energy together with a comparison of the performance parameters with results from the literature is presented in
Section 6. Finally, the conclusions are presented in
Section 7.
7. Conclusions
The present study provides a detailed analysis of the performance of a 40.16 kWp GCPV system located in Tochigi prefecture, Japan, after 8 years of energy generation. A monitoring period of 12 months, ranging from January 2019 to December 2019, has been considered in the study. A proposed analytical model with solar irradiation obtained from PDAV was developed to simulate and evaluate the performance of the GCPV system energy generation by comparing the simulated and actual measured energy acquired from the inverter. Interestingly, analysis results confirmed that the solar irradiation data obtained from PDAV is reliable and can be used to evaluate the energy of other GCPV systems. Based on the PDAV data, the results revealed that the monthly solar irradiation trends moved in the same direction with the measured energy through the inverter and showed no statistically significant differences and provided a reliable result for the other areas.
The technical performance of the present GCPV system was analyzed using the parameters developed and defined in the standard IEC 61724-1 by the International Electrotechnical Commission (IEC). The main outcome of the technical analysis is presented below:
The annual reference yield ( ), array yield () and final yield () of the GCPV system calculated 3.84 h/d, 2.98 h/d, and 2.59 h/d, respectively.
The annual average
of the GCPV system is characterized at 68.1 %. The annual average
of the GCPV system is 10.61%.
Table 6 shows that the performance of the present system is entirely satisfactory, and the value of
and
is comparable to other plants installed in India
The GCPV system installation’s annual average energy output (38,071 kWh/year) is assumed to be constant over the project life with an average of 0.85 capture losses () and 0.39 system losses ().
Based on the economic data, the
of this GCPV system was US
$0.336/kWh, which agrees with the data presented by METI [
25]. The findings and method used in this study clearly show how a GCPV system performs under real weather conditions in relation to the targeted energy and can be applied around the world. The performance of the GCPV system was compared with that of other GCPV systems installed across the globe. This approach would benefit PV systems service companies, consumers, and other stakeholders.