Keywords

1 Introduction

Even though the expansion of generation, transmission network and distribution system are increasing day by day to meet growing load demand, however, today approximately 14% of world population has no access to electricity. The main objective of the microgrid network operator is to provide cost-effective, energy security and reliable power supply to customers. Microgrid provides significant benefits of including low-cost system, reliability, integrating excess renewable power generation to microgrid, growth of rural areas by providing electricity to remote areas, and emission reduction. Integration of renewable energy sources PV, wind and fuel cell in distribution system was discussed using hybrid Nelder–Mead Particle Swarm Optimization algorithm [1]. In [2], various nano-grid configurations are modeled using HOMER software to evaluate technical and commercial implications. Hybrid energy system with PV, wind, BES, diesel generator and hydroenergy sources were simulated in HOMER software for coastal area of Saudi Arabia [3], Urumqi, China [4], Kadayam, Tamil Nadu [5], Iran [6] to evaluate technical–commercial benefits. A feasible solution obtained among different configurations of PV/BES/wind/fuel cell energy sources Saudi Arabia using HOMER Pro software [7]. Techno-commercial benefits of island grid with hybrid energy sources in Turkey were simulated using HOMER software [8]. Authors have concluded that cost of energy in islanded grid mode is higher than grid electricity. Also quoted that BES was economical compared to fuel cell technology. A hybrid system was simulated using HOMER software to quantify techno-economic benefits for mobile base transceiver station in Nigeria [9]. PV + DG-based minigrid is simulated for Nigeria [10] using HOMER software. Energy management in microgrids was addressed in [11] to minimize operational cost. Electricity consumption pattern, wind power output and electricity prices were forecasted using seasonal autoregressive integrated moving average model. Techno-economic advantage of islanded microgrid with hybrid energy sources is presented using HOMER Pro software [12]. The average cost of a typical hybrid energy system was determined using HOMER software [13, 14]. Major benefits of BES in grid integrated with non-conventional energy sources were addressed for reducing operation cost, frequency regulation, power quality improvement, power fluctuation stabilization, peak load shifting and system stability [15]. Appropriate technology and size of BES for microgrid expansion problem were solved using mixed-integer linear programming [16]. Optimal sizing of BES was presented using mixed-integer programming for commercial applications [17]. Energy dispatch of DGs, BES in microgrids in presence of uncertainties presented in [18] using mixed-integer quadratic programming. Optimal energy scheduling problem was solved using an alternating direction method of multipliers algorithm [19]. Based on the literature survey, it may note that major work published was pertaining to sizing and energy dispatch. This paper addresses optimal sizing of PV/WT/DG/BES, energy management and techno-commercial aspects of the islanded microgrid in Velliangattu, Tamil Nadu, India. In Tamil Nadu, the potential availability of natural resources of solar and wind is wealthy. Solar and wind energy sources are pollution-free, environmentally friendly and unlimited energy resource to provide energy security. The region has significant solar irradiation for almost 300 days of clear sun, therefore suitable for solar power generation. Also, average wind velocity is 3–5 m/s which is more suitable for wind power generation. For accurate analysis, real-time data of solar irradiation and wind velocity for the site location (Tamil Nadu) is taken from the weather portal and considered in the simulation study. The main contribution of the paper is:

  • islanded microgrid system is modeled in HOMER Pro software to feed load demand, and best configuration is identified based on technical, commercial and emission results;

  • explores techno-economic benefits of islanded microgrid configurations of PV + DG + BES, WT + DG + BES and PV + WT + DG + BES;

  • simulation results are obtained for optimal capacity of PV, WT, diesel generator, converter, battery energy storage system and state of charge of BES;

  • seasonal load variation and renewable power generation are suitably taken care in the simulation study.

The paper is organized as follows: Section 2 explains the hybrid system schematic model of HOMER Pro software. Simulation results are presented in Sect. 3. Finally, the paper concluded in Sect. 4.

2 Islanded Microgrid with Hybrid Energy Sources

HOMER Pro software schematic configuration of standalone microgrid system with PV, wind, DG, battery energy storage system and load is shown in Fig. 1. Optimal capacity of each component is determined to meet load completely; therefore, unmet electricity demand is zero throughout the planning period. The hybrid microgrid system is modeled in HOMER Pro software, and best configuration is identified based on technical, commercial and emission results.

Fig. 1
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Schematic model of islanded microgrid with hybrid energy sources

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Daily load profile and yearly load demand pattern is shown in Figs. 2 and 3. Peak load demand and average daily load demand on the system are 13.23 kW and 127.17 kWh/day, respectively. Hourly variation of solar irradiation and wind speed is shown in Figs. 4 and 5 for selected site location.

Fig. 2
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Daily electricity demand pattern

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Fig. 3
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Yearly load demand variation

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Fig. 4
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Hourly solar irradiation profile

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Fig. 5
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Hourly wind speed profile

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3 Economic Modeling

HOMER Pro software optimizes various possible configurations and ranks each feasible configuration based on net present cost (NPC). NPC of a system includes present value cost and revenue earned. Capital cost, replacement cost, operation & maintenance cost, and fuel cost are included in NPC calculation. NPC is calculated using Eq. (1).

$${\text{NPC}} = \frac{{C_{{{\text{ann}},{\text{ tot}}}} }}{{{\text{CRF}}\left( {i, N} \right)}}$$
(1)

\(C_{{{\text{ann}},{\text{tot}}}}\) is total annualized cost ($/year), i is rate of interest (%), CRF is capital recovery factor and N is project lifetime (years). Project lifetime is considered as 20 years in the simulation study. CRF is determined using the following equation.

$${\text{CRF}}\left( {i,N} \right) = \frac{{i\left( {1 + i} \right)^{N} }}{{i\left( {1 + i} \right)^{N} - 1}}$$
(2)
$$i = \frac{{i^{\prime} - f}}{1 + f}$$
(3)

i is the actual rate of interest, \(i^{\prime}\) is the discount rate of interest and f is the inflation rate.

Levelized cost of energy (LCOE) is the ratio of total annualized cost to total electrical load served \(E_{{{\text{served}}}}\) (kWh/year).

$${\text{Levelized COE}} = \frac{{C_{{\text{ann, total}}} }}{{E_{{{\text{served}}}} }}$$
(4)

Polycrystalline-type Canadian Solar MaxPower makes PV panel considered in the simulation study. The efficiency of PV panel is 16.94%, and lifetime is set as 25 years. Capital and replacement cost of PV system is considered as 900$/kW, and O&M cost is 10$/kW/year. Bergey Windpower making wind generator is considered in this paperwork. Capital and replacement cost of wind turbine system is considered as 15,000$/kW, O&M cost is 75$/kW/year, and lifetime is set as 20 years. Cut-in and cut-out speeds are taken as 3 m/s and 20 m/s, respectively. Rotor diameter and hub height of wind turbine is 15.81 m and 10 m, respectively. Diesel generator of TDPS make is considered in the simulation study. Capital and replacement cost of DG is considered as 900$/kW, O&M cost is 0.04$/kW/year, and fuel price is 1$/liter. Trojan-make BES is included in the simulation study. Capital and replacement cost of BES is considered as 220$/kW, O&M cost is 4$/kW/year, and lifetime is set as 10 years.

4 Results and Discussions

This paper simulates islanded microgrid with hybrid energy sources PV/DG/wind/BES in remote village Velliangattu, Tamil Nadu, India, using HOMER Pro software to quantify techno-commercial benefits, and the optimal scheme is determined based on annual net present cost. Simulation results are obtained for optimal capacity of PV, WT, diesel generator, converter, battery energy storage system and state of charge of BES. Simulation results have been obtained for following configurations:

Case 1: PV + WT + DG + BES.

Case 2: PV + DG + BES.

Case 3: WT + DG + BES.

System architecture details are given in Table 1 for three configurations. It is observed that PV + WT + DG + BES system is most optimal among other scenarios. Total annual load consumption of the system is 45,583 kWh/year which is met by PV power production 15,885 kWh/year, DG power production 14,679 kWh/year and wind turbine power production 23,948 kWh/year. It is evident from simulation results that total electricity demand is being supplied by 67.8% renewable fraction and 32.2% non-renewable fraction. Levelized COE of the optimal system is 0.7801$/kWh, and NPC value is $459,662.80. The total initial cost is low for case-2 hybrid system PV + DG + BES and high for case-1 PV + WT + DG + BES. Total operating cost and cost of energy (COE) are low for case-1 PV + WT + DG + BES compared to other hybrid systems. NPC and cash flows of hybrid system case-1 are shown in Figs. 6 and 7.

Table 1 System architecture details
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Fig. 6
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Annual net present cost of hybrid system case-1

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Fig. 7
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Cash flows for hybrid system case-1

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Cost comparison of various hybrid energy systems is indicated in Fig. 8. Optimal energy dispatch of the hybrid system is depicted in Figs. 9 and 10 to balance electricity demand and power generation. The simulation results indicate that hybrid microgrid system with PV + WT + DG + BES system reduces CO emissions by 72% and CO2 emissions by 15.3% per year as compared to the islanded microgrid system operating with DG alone. Rate of return (IRR) is 13.2%, return on investment (ROI) is 9.4%, and payback period is 7 years for the hybrid system.

Fig. 8
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Cost analysis of different hybrid energy systems

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Fig. 9
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Daily power dispatch of hybrid system

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Fig. 10
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Yearly power dispatch of the hybrid system

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5 Conclusion

This paper evaluates techno-commercial benefits of islanded microgrid with hybrid energy sources in remote village Velliangattu, Tamil Nadu, India. Different feasible configurations of a hybrid system with PV/WT/DG/BES are studied in this paper, and comparative analysis has been presented. Capital cost, operational cost, fuel cost, cost of energy and total cost are determined for each configuration. From simulation results, it is observed that configuration PV + WT + DG + BES has lower NPC and COE compared to other configurations considered in the simulation study. This paper can be useful to microgrid operator for decision making, solid investment toward rural electrification, design a competitive islanded microgrid and optimal energy dispatch.