Techno economic environmental assessment of hybrid renewable energy system in India

Received Dec 10, 2020 Revised Jul 9, 2021 Accepted Jul 23, 2021 The co-ordination of non-conventional energy technologies such as solar, wind, geothermal, biomass and ocean are gaining significance in India due to more energy requirements and high greenhouse gas emission. In this assessment, the sustainability of emerging the gird isolated hybrid solar photovoltaic (PV)/wind turbine (WT)/diesel generator (DG)/battery system for Arunai Engineering College (India) building is evaluated. The technoeconomic and environmental research was inspected by HOMER Pro software by choosing the optimal combination depends on size of the components, renewable fraction, net present cost (NPC), cost of energy (COE) and greenhouse gas (GHG) emission of the hybrid system. From the acquired outcomes and sensitivity investigation, the optimal PV-WT-DGBattery combination has a NPC of $28.944.800 and COE $0.1266/kWh, with an operating cost of $256.761/year. The grid isolated hybrid system is environmentally pleasant with a greenhouse gas emission of 2.692 kg/year with renewable fraction of 99.9%.


INTRODUCTION
Growth of population, globalization and the progression in innovation, builds the utilization in energy and the emission of a significant greenhouse gas (GHG), carbon dioxide (CO2) in the environment. In present days, the electric energy is mostly generated by conventional energy sources, for example, lignite, diesel and nuclear based energy sources. The fossil fuel based electric energy generation system derivatives drives two major issues, their consumption in nature and CO2 level in air prompting an unnatural weather change. Over the nation the non-renewable sources based electricity generation and consumer lines are integrated in a single grid. This structure of action ends up being advantageous for different spots, though, remote spaces suffer from restricted accessibility of electricity or no accessibility by any means, where the energy demand is less and the accessibility of petroleum products is far away from the heap request. The augmentation of grid such places bring about high establishment costs, less energy demand for most of the time. This is the place renewable energy sources (RES) coming to picture given their preferences, for example, accessibility at remote zones, unimportant contamination to the earth and less operating cost. International energy agency (IEA) forecasts that practically 30% of the electricity will produce from renewable sources by year 2020 [1]. assessed off grid hybrid solar-biomass system for provide electricity for rural areas in Pakistan. In this report the system initial capital cost and NPC are calculated as PKR 2.64 M and PKR4.48 M respectively and also electricity provide at COE 5.51 PKR/kWh for the application of agricultural purposes. The performance of hybrid solar photovoltaic/DG/battery in Sabah, Malaysia by Halabi et al. [44] using HOMER simulation tool. The outcomes shows the hybrid photovoltaic/DG/battery system configuration is the best optimal design compared to overall configuration. Renewable fraction of the system values varied like 0%, 39.89%, 42.38%, 59.21%, 86.90% and 100% depends upon different configuration of the hybrid system. The related investigations talked about give a good foundation to the current examination by introducing different techno-economic contextual investigations carried out in many countries. For the examinations reported in India, the gotten cost of energy is more because wrong selection of equipment and components for the feasibility investigation. A large portion of the investigations concentrated on NPC particularly in India contextual analyses. Accordingly, in this examination, HOMER Pro simulation software was used to define the optimal design of hybrid solar photovoltaic/wind/diesel/battery in southern region of India, Tiruvannamalai. It is evaluates the techno-economic analysis depends on the minimal NPC and COE with less environmental pollution effects. The various configuration were simulated and the optimal configuration for the investigation place is the hybrid PV-WT-DG-battery with a NPC and COE are $28.944.800 and 0.1266 $/kWh in that order.

STUDY AREA AND LOAD PROFILE DESCRIPTION
The grid isolated hybrid PV-WT-DG-battery is designed to make available electricity for Arunai Engineering College (Educational Institution) in Velu Nagar village, Tiruvannamalai with latitude 12 0 11.6' N and longitude 79 0 5.0' E. The Institution is located in North-West region of Tamilnadu and located in western mountainous hills, which has huge amount of solar potential and wind potential.
The Arunai Engineering College was established in the year of 1993, total area of around 105.50 sq.m. Spanning area for academic, hostels, playground and amenities purposes. The institution consists of several buildings and each building consists of three to four floors. The most of the buildings are used for the academics purpose and few buildings are used for the hostel and administrative purposes. The electricity is needs for academics, administrative and hostel buildings for various electrical appliances at different time duration. The academics and administrative buildings energy consumption is relatively high due to more number of lights, air conditioner, lifts, computers and electrical motors at time duration between from 8.00 am to 5.30 pm. In hostel buildings mostly light loads, air coolers and water heater are consuming electrical energy at time duration between from 5.00 pm to 9.00 am.
The total load and energy consumption of the administrative building is 19.8794 kW and energy consumption 158.873 kWh/day, while the total load and energy consumption for academic and hostel buildings are 355.8785 kW and 1490.9312 kW, 2649.719 kWh/day and 8527.0108 kWh/day as presented in Table 1. The overall three buildings total energy consumption per day, peak load and average energy consumption are 11335.5128 kW/day, 1,769.87 kW and 472.31 kW/day with a load factor of 0.27, 15% hour-hour and 10% day to day random variable were used to enable the load data to have some degree of variability at different times of the year. The load data is served into the HOMER software for the graphical representation of the hourly and monthly load profiles as illustrated in Figure 1.

SOLAR AND WIND POTENTIAL ASSESSMENT
To design a solar PV system, the information on the SR and clearness index of the particular site is required. The openness of this solar potential is dictated by the accessibility of enough daylight hours in the zone [45]. For this evaluation, [46] the information utilized for the investigation was acquired from National aeronautics and space administration (NASA) utilizing the latitude and longitude of the area.
The chose area is in Tiruvannamalai arranged at latitude 12 0 11.6' N and longitude 79 0 5.0' E with the forecast daily average SR is 5.14 kW/m 2 /day. The twenty two years the average value of the solar data was gained from NASA by means of HOMER Pro software, the solar data information comprising of the clearness index and solar radiation ranges from 0.454 to 0.634 and 3.99 kW/m 2 /day to 6.43 kW/m 2 /day respectively as introduced in Figure 2. The long stretch of November has the least SR is 3.99 kW/m 2 /day and the period of March has the most elevated SR estimation of 6.43 kW/m 2 /day. In any case, the month having least SR is still the solar system can be used to generate electricity. Wind is another renewable resource that can be tackled for power generation. Wind turbines are combined with inbuilt generators which transforms the wind energy into electrical energy [9]. To generate effective electrical energy from the wind system, the evaluation place must have the essential wind speed to be driving the wind turbine. The non-identical wind turbines are exist for electric power generation and can work at different wind speed be decided by manufacturers, the wind speed for wind turbine activity may differ between 2.5 m/s cut-in WS and 25 m/s cut-out WS [10]. In this evaluation, the average wind speed of the AEC campus location 3.29 m/s at 50 m height. The WS changes between 2.65 and 3.95 m/s for the whole year in this location [46]. The information utilized for this investigation was acquired from NASA by means of HOMER Pro software, twenty two years average wind speed information changes between 2.65 and 3.95 m/s as introduced in Figure 3. There is lower WS the month of November having an average WS of 2.65 m/s and higher WS of 3.95 m/s during the period of May. However, the average wind speed of the investigation place falls inside the necessary wind speed that can be utilized to exploit energy to generate electricity.

DESIGN AND SPECIFICATION DESCRIPTION OF HYBRID SYSTEM
The grid isolated hybrid electric energy system comprising of photovoltaic arrays, wind generator, diesel generator, battery, a converter, DC bus, AC bus and electric load as appeared in Figure 4. The batteries are used to store the surplus energy that can utilized while the solar photovoltaic and wind generator systems are not capable to encounter the load demand, while the diesel generator fills in as a reinforcement power flexibly when the solar, wind and the batteries also not capable to encounter load requirements. Various combination of hybrid frameworks have been proposed in various pieces of the globe dependent on the accessible renewable resources in those regions [47], [48]. In India, a few investigations have likewise been completed utilizing the accessible renewable resources [1], [11], [12], [27]. In this assessment HOMER Pro is utilized to design the hybrid PV-WT-DG-battery system and analysis the techno-economic feasibilities, optimization of power and sensitivity. It simulates various framework designs utilizing sources of info, for example, climate information for the chose location, component technical specifications, cost of the components and load information. HOMER Pro software simulates the wide range of framework arrangements and chooses optimal design with the less NPC and levelized COE. Figure 5 presents the architecture of the HOMER Pro software for techno-economic assessment.   Figure 5. Architecture of the HOMER Pro operation for Arunai Engineering College.

Output power of the solar photovoltaic array
The output power of the solar photovoltaic array is calculated by (1) [12], [35] in HOMER Pro. Where YPV, fPV, GT and GT, STC are the PV array rated capacity, derating factor, actual SR and test condition SR respectively. Tc and Tc, STC, αp, are the actual and standard test condition cell temperature and temperature coefficient respectively. In this assessment, Tat305TP305LBZ, rating of 0.305 kWp flat plate photovoltaic panel is selected and its capital cost, operation and maintenance cost (O & M), replacement cost (RC) and other technical parameters details are introduced in Table 2. The maximum capacity of the photovoltaic system considered for this assessment is 3500 kW.

Output power of the wind generator
The WS in wind turbine hub was assessed by HOMER Pro as (2) [12], [35].
Where Uanem is a WS, Zanem is a height of the anemometer, Zhub is a height of the hub and Z0 is a length of the surface. The wind system output power is determined as (3).
Where PWTG, STP is a output power of the wind turbine at standard conditions are determined utilizing the wind turbines output power curve, ρ is actual air density and ρ0 is air density at standard conditions. In this assessment selected a Generic 10 kW wind turbine framework which is chosen dependent on the cut-in and cut-out WS of the wind turbine, Height of WT and cost of the WT. Figure 6 represents the characteristic curve of the WT. The technical parameters of the WT, CC, RC, O&M cost are introduced in Table 3.

Diesel generator
The essential back-up power source, diesel generators have been generally utilized in hybrid power generation system so as to improve the reliability of the system. In this assessment, 500 kW diesel generators were chosen to fulfill a peak load demand of 1769.87kW with 10 % of operating reserve capacity. The fuel Here, PDG-rated, PDG-out are the generator rated power and generator output power. Efficiency of the diesel generator is determined by utilizing the derived equation [35].
Here, ρfue is the density of the fuel (kg/m 3 ) and HL-fue (MJ/kg) is the lower warming of the fuel. The DG efficiency curve as presented in Figure 7 and technical parameters of the diesel generator, CC, RC, O&M cost, fuel consumption and other parameters are introduced in Table 4.

Battery charge and discharge power
A battery maximum charge power (Pbatt, cmax) is measured using HOMER Pro is the base of three distinct limits on the batteries Pbatt, cmax, to be specific [12], [35].
, , , , = 1000 (9) Where, Q1, Q and Qmax are the accessible energy, sum of energy and capacity of the battery bank respectively. c, k and αc are the capacity ratio, constant rate and maximum rate of charge. Additionally, t, Nbatt, Imax, Vnom, gbatt, c, gbatt, rt are step time, battery quantity, battery nominal voltage, battery charge efficiency and round-trip efficiency respectively. The maximum discharge power (Pbatt, dmax) of the battery banks as calculated as (11), (12) and (13).
Where, , , In this assessment, a PowerSafe SBS 3900 lead-acid battery with 12 V, maximum capacity is 4300 Ah and nominal capacity of 51.6 kWh is selected for simulation. The round-trip efficiency of this battery is 97% with minimum state of charge (SOC) value is 30%. The technical and economic parameters details are introduced in Table 5. Figure 8 shows the capital and replacement cost variation curve.

Converter
There are two energy conversion in the electric system such as DC-AC and AC-DC conversion. Consequently, an inverter and rectifier are fundamental. In this assessment a Del82.764 converter, the rectifier had 100% limit comparative with the inverter and its efficiency was 98.5% and converter lifetime was 15 years. The converter technical and economical parameters are introduced in Table 6.

Economic evaluation of the system
The NPC includes transformation of every single yearly advantage and costs stream happening at various focuses in the existence time of the project to their current value counterparts and including them to get the overall worth everything being equal and expenses of the project which is mathematically composed as [35] Here Rt, Ct, I, I0 and N are the income, expense, rate of interest, initial cost and project life time respectively. The COE is acquired by including up the net costs a yearly premise and partitions it by the yearly provided energy as (15) Where, It is an annual capital cost and replacement cost.
Where, CR is a replacement of the components, tR is a time of the replacement and nR is the no.of replacements during the existence time of the project. Likewise AGC and AMC are yearly net grid charge and maintenance cost, independently.

Environmental evaluation of the system
The GHG emission in hybrid PV-WT-DG-battery system results from the generation of electric power by the renewable resources and generators. For the diesel generator yearly CO2 emission is determined by using emission factor and yearly fuel utilization. For the grid integrated system, the emission level is calculated by using purchased net power from grid and its emission factor [35].

OPERATION STRATEGY
The grid isolated hybrid PV-WT-DG-battery system works in two principle techniques, specifically the cycle charging (CC) and load following (LF). The CC technique, the DG joined is utilized to supply power to the load and charge the battery bank simultaneously. While LF technique, the solar and wind turbines are serving demand simultaneously the battery bank charged by surplus power. In the occasion where the renewable power generation is not capable to encounter or inaccessible, the DG is arranged to attend the load. Fiure. 9 represents the operational flowchart for grid isolated hybrid PV/wind/diesel/battery system. The flow chart expresses the expresses overall power management of the system that is directs the flow of the energy in the hybrid system. For this assessment, the LF technique is implemented where just the renewable energy sources are utilized in charging the battery bank.
The charged battery storage system attends to serve the load demand in the occasion where the renewable sources can't serve the load requirements. The diesel generator can possibly serve the load demand when both renewable sources and battery storage systems are couldn't meet the loads. This decreases helps in decreasing the surplus power generation and furthermore helps in reduce NPC of the framework. There are circumstances that the load can't be given by the RES because of weather conditions. For instance, when  Figure 9. Operational flowchart for grid isolated hybrid PV/wind/diesel/battery system

SIMULATION RESULTS AND DISCUSSION
In this assessment designs a hybrid PV-WT-DG-battery electric system to attend the electric load requirements of Arunai Engineering College in Tiruvannamalai, Tamilnadu, India. HOMER Pro simulation tool was employed to model the hybrid renewable energy system by determining the optimal system configuration using the Arunai Engineering College electric load profile, weather data and component details.

Optimization analysis of the hybrid electric system
HOMER Pro software categorized all the possible framework arrangements for the Arunai Engineering College. The classified optimal configuration for Arunai Engineering College with an annual average SR of 5.14 kWh/m 2 /day and a fuel cost of 0.86 $/L are appeared in Table 7 and Figure 10. The optimization configurations are classified four kinds of power system with minimum NPC and COE as PV-WT-DG-Battery, PV-DG-battery, PV-WT-battery and PV-battery.
For the optimal PV-WT-DG-battery design contains 3500 kW photovoltaic panels, 1 kW wind turbine, 500 kW DG, 1.222 quantity of batteries with 2.090 kW converters. It has the total NPC of $28.944.800 and COE of $0.1266/kWh. For this design, the solar system has the higher capital expense followed by the batteries and the converter, the diesel generator has the least capital expense. In view of the NPC, the batteries have the higher NPC because of replacement cost followed by the solar photovoltaic and fuel cost of DG, the converter of the system has the minimum NPC. Table 8 presents the overview of the cash flow of the optimal setup investigated by various cost types. Table 8 presents the capital and replacement expenses are main cost of the system which includes for the most part the batteries and the solar system, followed by the diesel cost. The operating and maintenance cost is extremely minimum due to considered the system is mainly supplied by the solar and wind sources, which has the less operating expenses.    Table 7 and Figure 10. It is noticed that the design with the more number of batteries has the higher replacement cost because of more battery cost, it is in this way decided the quantity of batteries influences the expense of a framework. Furthermore, the total NPC and COE of all the feasible framework designs examined in Arunai Engineering College are demonstrated in Figure 11.  Table 9. Moreover, Figure 12 and Figure 13 shows the month average energy generation, surplus energy from the optimal hybrid PV-WT-DG-Battery system in Arunai Engineering College.

Environmental analysis of the hybrid system
From the design simulated by HOMER Pro, the hybrid PV-WT-DG-battery system has the more carbon dioxide emission of 2.692 kg/year, followed by hybrid PV-DG-Battery setup with CO2 of 2.355 kg/year. The PV-WT-battery and PV-battery arrangements have zero greenhouse gas emission due to the 100% renewable fraction of the system. This shows that the hybrid PV-WT-battery and PV-battery systems are the most environmentally friendly configurations with zero emission, but unfortunately not economically viable because they have the highest NPC and COE compared to the optimum configuration system. It shows the hybrid PV-WT-battery and PV-battery systems are the most environmentally friendly setups with zero emission, but not economically feasible due to higher value of NPC and COE compared to the other optimal design. The hybrid system with the optimal design dependent on the less NPC and COE is still environmentally friendly due to less amount of greenhouse gas emission with 99.9% of energy generated from renewable sources compared other setup. Table 10 represents the greenhouse gas emission of the various configurations simulated by HOMER Pro.

Sensitivity analysis of the hybrid electric system
Certain sensitivity factors were providing into HOMER Pro software to decide the optimal system arrangement and corresponding techno-economic assessments for such system. By performing the sensitivity assessment for this hybrid system, a different value of yearly average solar radiation, average temperature, oscillation in average WS, rise and fall of the fuel price and changing the multiplication value of the capital cost, RC and O&M cost of the photovoltaic and wind system were conducted.

Sensitivity analysis with the variation of average SR
When the hybrid PV-WT-DG-battery system model in HOMER Pro, the yearly average solar radiation ranges from 4.5 kWh/m 2 /day to 5.5 kWh/m 2 /day. As saw in Table 11, with the other design factors of the system are undisturbed, during the system is operating at yearly average SR was 4.5 kWh/m 2 /day, optimum size of the photovoltaic and wind turbine required were setup 3500 kW and 406 kW, which are 20 kW photovoltaic and 403 kW wind turbine more than when the system is operating at yearly average SR was 5.5 kWh/m2/day. Therefore, the capital cost, operating cost, NPC and COE was rises by around 62.2%, 38.37%, 53.46% and 53.44% correspondingly as compared with the system is operating at average SR was 5.5 kWh/m 2 /day appeared in Figure 14.  Figure 14. Cash flow summary of PV-WT-DG-battery system at different solar radiation 6.5.2. Sensitivity analysis with the variation of average temperature By keeping the yearly average solar radiation, wind speed and other design factors are constant for this optimal hybrid system, the yearly average temperature were ranges from 20 0 C to 45 0 C. When the hybrid system is operating at average temperature was 20 0 C, the quantity of the photovoltaic and wind turbine required were setup 3500 kW and 1 kW, the wind turbine quantity is 403 kW less than when the system is operating at yearly average temperature were 45 0 C as shown in Table 11. Accordingly, the capital cost, operating cost, NPC and COE was drops by almost 39.48%, 25.93%, 33.51% and 33.52% in that order as related to when the system is operating at temperature was 45 0 C as displayed in Figure 15.

Sensitivity analysis with the variation of average wind speed
The average WS of the WT changes between 2.5-5 m/s with fuel cost of 0.86 $/L, Temperature 27.07 0 C, Solar radiation of 5.14 kWh/m 2 /day. As observed in Table 11 when the system is operate at average WS was 2.5 m/s, the size of PV and WT wanted were found to be 3500 kW and 3 kW, the size of the WT is 40 kW greater than when the system is operates average WS was 5 m/s. Therefore, the capital cost, operating cost, NPC and COE was rises by roughly 2.99%, 13.16%, 7.95% and 7.94% respectively as associated to when the average WS was 5 m/s as presented in Figure 16.

Sensitivity analysis with the variation of fuel price
The universal oil and gas area encounters changes in the costs of prepared raw petroleum items, among the few reasons for these value fluctuations are governmental strategies and complexities emerging from the extraction and handling of unrefined petroleum into items, for example, diesel fuel. Therefore, a sensitivity assessment of variation in diesel prices comes to be essential. Here, when the cost of fuel were differed between $0.5/L, $1.0/L and $1.5/L at SR of 5.14 kWh/m 2 /day , Temperature of 27.07 0 C, WS of 3.29 m/s, it was seen that costs of diesel impacted the total NPC and COE as found in Table 11. NPC observed at $0.5/L, $1.0/L and $1.5/L expanded in extent by 0.098%, 0.099% and 0.12% in that order. The cost of energy saw at $0.5/L, $1.0/L and $1.5/L expanded by 0.078%, 0.15%, and 0.24% correspondingly.

Sensitivity analysis with variations of PV and WT capital, RC and O&M costs
In this assessment, the photovoltaic and wind system initial cost, RC and O&M costs were given for the period of hybrid system model in HOMER Pro, hereafter an adjustment in the initial, replacement and O & M costs. At an yearly average SR of 5.14 kWh/m 2 /day, fuel cost of 0.86 $/L, average temperature of 27.07 0 C, average WS of 3.29 m/s, varying the initial cost, replacement cost, operation and O&M costs of the photovoltaic and WT was multiplied by 0.6 % and 1.4 % of the original cost. During the photovoltaic system costs are multiplied by 0.6 % and 1.4 %, the net present cost vary from $24,910,280 to $32,979,310 and COE from 0.1089 $/kWh to 0.1442 $/kWh as presented in Table 11. When the wind turbine costs are multiplied by 0.6 % and 1.4 %, the net present cost vary from $28,750,590 to $28,966,780 and COE from 0.1257 $/kWh to 0.1267 $/kWh as presented in Table 11.

Sensitivity analysis with variations of fuel price and average solar radiation
For this assessment, the average solar radiation and fuel cost considered for sensitivity analysis ignoring the wind speed. The solar radiation and fuel costs were both fluctuated to get the impact of variation on the hybrid system economy. In spite of the fact that the diesel cost is selected at $0.86/L, it ranges between $0.5/L-$1.5/L and the average solar radiation as well fluctuates between 4.5 and 5.5 kW/m 2 /day. Table 12 shows observed sensitivity results, due to the fuel cost and solar radiation fluctuations with corresponding NPC and COE. When solar radiation is increases and fuel cost decreases the system NPC and COE are decreases. Whereas a decrease the solar radiation and increases the fuel cost the system NPC and COE are increases. Figure 17 and Figure 18 exposed the total fuel cost per year and COE respectively for the hybrid PV-WT-DG-Battery system.  Figure 17. Effect of solar radiation (kWh/m 2 /day) and fuel price ($/L) on the total fuel price ($/year) of the optimal configuration system Figure 18. Effect of solar radiation (kWh/m 2 /day) and fuel price ($/L) on the COE of the optimal configuration system

CONCLUSION
In this assessment, a gird isolated hybrid solar photovoltaic/wind turbine/diesel generator/battery system for electricity generation for Arunai Engineering College in Tiruvannamalai, Tamilnadu, southern India. The HOMER Pro software is used to design a hybrid electric system. The proposed system simulation results were determined based on the minimum NPC and COE. In this system were found the four categorized optimal design configuration which take account of PV-WT-DG-battery, PV-DG-battery, PV-WT-battery and PV-battery systems. The acquired results from this hybrid system, it very well be determined that the combination of the energy sources with less NPC of $28.944.800 and COE of $0.1266 is the PV-WT-DG-battery and is the optimal combination for all the sensitivity results. a) the optimal PV-WT-DGbattery combination of the system has a renewable fraction of 99.9% with delivered yearly greenhouse gas emission of 2.692 kg, b) the fourth optimal PV-battery combination of the system has a zero-greenhouse gas emission due to the 100% renewable fraction. Unfortunately, the combination has the highest NPC of $30.601.110 and COE of $0.1338 because of the huge amount of costs need to spend for converter and storage batteries, c) the economic and environmental analysis has demonstrated that the optimal PV-WT-DGbattery combination system is economically and environmentally feasible for the reason that of less capital cost, operating cost, NPC and COE with less amount of greenhouse gas emission for electric power