Techno-Economic Evaluation of Hybrid Photovoltaic-Wind Energy Systems for Indonesian Government Buildings

An escalating population trajectory is directly proportional to the burgeoning demand for energy [1]. It is observed that primary energy reserves, specifically oil and coal, are diminishing, heralding the potential onset of energy deficits [2]. The depletion of fossil fuel reserves, coupled with the exacerbation of the greenhouse effect, has catalyzed a quest for alternative, eco-friendlier energy sources [3]. Renewable energy is being widely researched and developed to overcome these various problems [4], [5]. Intensive development has positioned solar energy as a renewable frontrunner [6]. The intrinsic characteristics of solar energy, notably its chemical-free and non-radioactive nature, render it benign to the environment [7], [8]. The application of solar energy is diverse, spanning electricity production, water heating, air heating, and support for various industrial drying processes [9], [10]. Nevertheless, the uneven distribution of solar irradiance necessitates sophisticated technology for optimization [11]. It has been posited that hybrid power plants could offer an economical and efficient solution [12]. The present study models an optimal generating system to address renewable energy requirements.

Solar and wind energy are burgeoning in popularity, with economic potential that is becoming increasingly competitive with that of conventional power plants [13], [14]. These renewable sources are profuse in nature and their utilization does not contribute to CO₂ emissions, thereby affirming their environmental soundness. Indonesia, straddling the equator, reaps substantial solar irradiance annually [15]. As an archipelagic nation subjected to monsoonal winds, it experiences two distinct seasons, offering opportunities to harness wind energy [16]. The synergy of solar and wind energy promises a complementary power source, with solar being predominant during the dry season and wind during the rainy season and nocturnal hours [17], [18]. The use of hybrid solar and wind energy has proven more effective than relying solely on solar energy in various regions of Indonesia [19].

Techno-economic analysis has been established as a necessary component in designing generating systems. This analytical approach quantifies in monetary terms the feasibility of engineering projects [20]. Such analysis has corroborated the viability of projects like the rooftop PLTS System on the Denpasar mayor's office [21]. Furthermore, Arifin et al. [22] have conducted simulations on the potential of interconnected PV-Wind hybrid systems in urban Java. This analysis aimed to create effective, renewable energy with technical, economic and environmental security to solve Indonesian energy crisis [23], [24]. The current research utilizes the HOMER software to examine cost-effectiveness and economic feasibility for power generation systems [25].

The objective of this research is to simulate PV-Wind hybrid energy as a sustainable, efficient, and eco-friendly source of electrical energy for government buildings in Semarang, Surabaya, Yogyakarta, Jakarta, and Denpasar cities. The adoption of an on-grid system configuration, connecting with the PLN (Perusahaan Listrik Negara) electricity network, is considered. This study analyses the techno-economic aspects of PV-Wind hybrid power generation for Indonesian government buildings, with simulation outcomes offering comparative insights and evaluation of factors affecting cost-effectiveness in system design.

The methodology of this study was systematically approached, initiating with a comprehensive literature review, followed by rigorous data collection, leading to detailed simulations and subsequent analyses. Simulations of the PV-Turbine Hybrid PLTS (solar power plants) were executed using the HOMER software to ascertain the optimal configuration of the hybrid systems, as shown in Figure 1.

The design of the Hybrid PV-Wind Turbine System was modeled utilizing the HOMER software, developed by the National Renewable Energy Laboratory (NREL) [26]. This tool facilitates the optimization of microgrid configurations, allowing for the computation of total energy output and variations in system costs, as well as the economic and financial feasibility of different designs. HOMER is instrumental in the assessment of power generation systems, determining their suitability for grid-connected (On-Grid) or off-grid (Off-Grid) applications.

In this methodology, HOMER was employed to identify the most efficient system configuration, prioritizing the results based on the NPC from the lowest to the highest [27]. Such a prioritization ensures the selection of the most cost-effective system to fulfill the electricity requirements of government buildings. Within the scope of this research, the specifications for the solar panel comprised the Schneider Conext CL25000 E with a generic PV model. The wind turbine selected was the Bergey Excel 6-R series, and the inverter was the KEHUA France KF-BCS 630K-B series. Figure 2 presents the On-Grid system design as conceptualized using the HOMER software.

Within the configuration under study, the solar panel array is connected to a wind turbine, serving as a direct current (DC) input. An inverter is then employed to transform the DC voltage from the PV cells and the turbine into alternating current (AC) voltage, which is subsequently delivered to the electrical load. Should the voltage generated by the renewable sources prove insufficient for the demands of government buildings, the national electricity utility, PLN, is posited to supplement the shortfall, as shown in Figure 3.

Prior to the commencement of simulations with the HOMER Pro software, requisite data are inputted into the system. These encompass load profiles, renewable energy source data (inclusive of solar irradiance, ambient temperature, and wind velocity), along with technical and economic parameters. Table 1 delineates the list of components integrated into the aforementioned system. It is to be noted that these components are readily procurable within Indonesia, with particular availability on the island of Java.

Simulations for the design of the Hybrid PLTS destined for governmental structures are to be conducted within several notable urban centers across Indonesia, including Semarang, Surabaya, Jakarta, Yogyakarta, and Denpasar. The objective of these simulations is to ascertain the economic viability and potential of the aforementioned systems within five major Indonesian cities. The locations selected for the proposed development are depicted in Figure 4.

Solar power plants (PLTS) harness solar radiation, with the efficacy of conversion to electrical energy being contingent upon the PV cells' capacity to absorb this radiation. It has been observed that an augmentation in the intensity of solar radiation impinging upon the photovoltaic cell corresponds to an increased electrical output [28].

Data pertaining to solar radiation intensity across various urban locations, namely Semarang, Surabaya, Jakarta, Yogyakarta, and Denpasar, has been collated and is presented in Table 2. These measurements were procured from the archives of the National Aeronautics and Space Administration (NASA).

Denpasar City, exhibiting an average solar radiation intensity of 4.45 $\mathrm{kWh} / \mathrm{m}^2$, presents considerable prospects for the deployment of the Hybrid PLTS System. It is postulated that the efficiency of the energy output from such systems is positively correlated with higher intensities of incident solar radiation.

Wind velocity data, sourced from the NASA, facilitate the analysis of wind energy's potential integration into Hybrid PLTS, specifically within Semarang, Surabaya, Jakarta, Yogyakarta, and Denpasar. The wind velocity metrics for these municipalities are delineated in Table 3.

Elevated wind speed values correlate with enhanced efficiency in energy output from the generation system. The data presented indicates that Denpasar City exhibits the highest mean wind speed, registering at an average of 4.32 m/s, thereby underscoring its substantial potential for the deployment of the Hybrid PLTS System.

To list the total expense, Table 4 summarizes the data daily total load.

Photovoltaic solar panels are a device that can produce electrical energy from solar radiation [29]. The power produced by the solar panel module can be calculated using the following Eq. (1) [30].

where,

PPV: Power produced by the PV module (kW)

Fpv: PV derating factor

Ypv: Power output PV at standard conditions (kW)

GT: Instantaneous radiation on the surface of the PV module ($\mathrm{kW} / \mathrm{m}^2$)

GT, STC: Instantaneous radiation under standard conditions (1 $\mathrm{kW} / \mathrm{m}^2$)

The type of solar panel used in this Hybrid PLTS System is the Schneider Conext CL25000 E solar panel with generic PV. This solar panel has the specifications shown in Table 5 and can be seen in Figure 5.

A wind turbine is a device that captures kinetic energy in the form of wind energy and converts mechanical energy (turbine movement) into electrical energy through a generator [28]. The following equation is used to calculate the potential power produced by a wind turbine $\left(P_{m t}\right)$ every day [31].

where,

$P_{m t}$: The potential power produced by a wind turbine

$\rho$: Density of air ($\mathrm{kg} / \mathrm{m}^3$)

$v$: Wind speed (m/s)

$A$: Blade area ($m^2$)

$cp$: Turbine efficiency

The type of wind turbine used in this Hybrid PLTS System is Bergey Excel 6-R. This wind turbine has the specifications shown in Table 6 and can be seen in Figure 6.

The inverter functions to change the current from DC electric voltage (direct current) produced by the PV array into AC electric voltage (alternating current) with a frequency of 50Hz/60Hz [32]. Hybrid PLTS for Government Buildings uses a KEHUA France KF-BCS 630K-B inverter. The specifications of this inverter are shown in Table 7 and depicted in Figure 7.

The optimality of the system configuration is ascertained by the magnitude of the NPC, which reflects the aggregate cost of the system over its lifespan. The HOMER software sequences the optimization outcomes by ascending NPC values, thereby privileging the most cost-effective configurations [33]. The total NPC encompasses the entirety of the project expenditures, encapsulating component costs, replacement, maintenance, operational fuel, and the cost of capital. The NPC is calculable by employing the following Eq. (3) [22].

where,

Cann, tot: Total annual fee (Rp/year)

CRF: Capital recovery factor

$\mathrm{i}$: interest rate

Rproj: life of use (years)

In conjunction with the determination of NPC, the analysis further extends to the computation of the COE, representative of the average cost per kilowatt-hour for the electricity generated by the system. The COE is derived by the division of the total annualized system cost $\left(C_{\text {ann,tot }}\right)$ by the annual electrical energy output accommodated by the system $\left(E_{\text {served}}\right)$. This relationship is succinctly captured in the mathematical expression for COE, presented as Eq. (4) [34].

where,

Lprim,AC: AC loads per year (kWh/year)

Lprim,DC: DC loads per year (kWh/year)

Utilizing the HOMER software, the simulation conducts an optimization process to ascertain the most efficacious configuration of the proposed system. The optimal system configuration, as determined by HOMER, favors an on-grid setup. The annual energy output produced by the system across five cities is delineated in Table 8.

The HOMER simulation additionally yielded results for the annual electricity load consumption for each city, as detailed in Table 9.

Drawing from the data presented in Table 8 and Table 9, it emerges that Denpasar City exhibits the most substantial potential, boasting the highest total electric power production at 1,360,195 kWh/year. Conversely, Semarang City demonstrates the least total power consumption, recorded at 943,170 kWh/year.

The NPC serves as a financial metric to ascertain the cumulative expenditure associated with the establishment and operational maintenance of a power generation facility. The NPC encompasses a multitude of financial aspects within each system configuration, such as initial capital outlay, costs of component replacement, operations and maintenance (O&M), fuel expenditures, and end-of-life salvage value [31]. The NPC figures play a pivotal role in evaluating the financial viability of each proposed system configuration; configurations with lower NPC values are indicative of greater economic potential. The simulation-derived NPC values for the various configurations under consideration are delineated in Table 10.

Based on the data in Table 10, it can be concluded that the city with the highest potential is Denpasar City, with an NPC value of IDR 27,529,340,000.00.

The COE represents the average monetary expense incurred for each kilowatt-hour of electricity generated by the system [35]. This metric is integral to gauging the economic efficiency of the system configurations devised. Optimal configurations are characterized by lower COE values, which denote a higher economic advantage. The simulation results yield the COE values for the respective configurations, which are systematically cataloged in Table 11.

Based on the data in Table 11, it can be concluded that the city with the most potential is Denpasar City, with a COE value of IDR 997.17.

The BEP delineates the juncture at which revenue equals the costs, signifying a neutral financial position wherein neither profit nor loss is realized over a specified duration. It is a critical measure for evaluating the financial viability of energy systems. A lower BEP suggests a swifter recovery of investment, indicating a system with enhanced economic potential. The BEP values derived from the HOMER-based simulation across the various cities are delineated in Table 12, illustrating the comparative economic outcomes for each locale.

Based on the data in Table 12, it can be concluded that the city with the most potential BEP value is Semarang City, with a BEP value of 3.1 years.

The outcomes of the HOMER software simulations have identified Denpasar as the city offering the most auspicious prospects for the PLTS configuration in government edifices. The optimization facilitated by the HOMER software enabled the ascertainment of the most favourable system configuration, which was determined by assessing various metrics including the total electrical energy generated, total electrical energy utilized, NPC, COE, and BEP. The monthly electrical output from the optimized system configuration is depicted in Figure 8, whilst the cash flow projections for the proposed model, as simulated for Denpasar City, are exhibited in Table 13.

In this investigation, an evaluative comparison was conducted of on-grid hybrid PV-Wind Turbine PLTS tailored for governmental structures across five major Indonesian urban centers: Semarang, Yogyakarta, Surabaya, Jakarta, and Denpasar. Utilising the HOMER software, system configurations were simulated and optimized. The results indicate a superior efficiency and cost-effectiveness for the hybrid (PV/Wind) system over a standard PV system, given identical electrical loads.

It was revealed through modelling that the hybrid system, when connected to the grid, obviates the need for supplementary battery storage under standard operational parameters. Moreover, surplus renewable energy is seamlessly integrated into the grid. Pertinent metrics considered in the assessment of system design potential encompassed total electrical output, consumption figures, NPC, COE, and BEP.

The simulations executed via the HOMER software identified Denpasar as the city with the highest potential for the implementation of hybrid PV/Wind Turbine systems in government buildings. The findings demonstrate Denpasar's capability to generate 1,360,195 kWh/year, with total electricity consumption recorded at 1,214,136 kWh/year. The NPC was determined at approximately IDR 27,529,340,000.00, and the COE was ascertained at IDR 997.17, suggesting a viable investment with the BEP projected at 8.2 years. The estimated initial construction cost for the PLTS at government edifices in Denpasar stands at IDR 4,149,376,743.96.

It is envisaged that the outcomes of this study will contribute to the advancement of renewable energy utilization, notably in harnessing solar and wind energy. The innovation presented by this hybrid PLTS design is anticipated to facilitate a reduction in future investment costs for componentry. Consequently, such hybrid power generation systems are poised for escalated development in the ensuing years.