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Proc. of the 4rth International Conference on Power Generation Systems and Renewable Energy Technologies (PGSRET) 10-12 September 2018, Islamabad, Pakistan



Techno-economic Analysis of PV/Wind/Biomass/Biogas Hybrid System for Remote Area Electrification of Southern Punjab (Multan), Pakistan using HOMER Pro Muhammad Umer Khan Department of Electrical Power Engineering USPCAS-E NUST Islamabad, Pakistan [email protected]



Muhammad Hassan Department of Electrical Power Engineering USPCAS-E NUST Islamabad, Pakistan [email protected]



Mazhar Ali Department of Electrical Power Engineering USPCAS-E NUST Islamabad, Pakistan [email protected] Abstract— Decentralized generation using hybrid renewable energy systems has emerged as economical and technically feasible solution for electrifying remote areas. This study emphases on designing a hybrid system consisting of PV/Wind/Biomass/Biogas energy resources to electrify a remote community in Multan, district of south Punjab. Three Different configurations of the hybrid micro-grid system (PV/Biomass, Wind/Biomass, and PV/Wind/Biomass) are modeled using HOMER Pro software and optimization results are presented. Results of techno-economic analysis shows that all three configurations of proposed hybrid system meet the load demand of 259.44 kWh/day. Further, all three hybrid system configurations in which animal manure is used as biomass resource instead of crops residue are more economical. Slurry produced in such can be used as a fertilizer for crops as Multan is an agricultural area. Keywords—Hybrid Energy System; Techno-economic analysis; Net Present Cost (NPC); PV/Wind/Biomass hybrid system.



INTRODUCTION Across the globe, energy is known as the driving asset for social and economic development of a country. There is a shift of one way basic demand from conventional resources to indigenous one. Renewables are adopting more rapidly worldwide that decreases the reliability of single dependent energy resources[1]. The sole based renewable power system requires a storage system as renewable energy is intermittent thus increase the cost of energy. Hybrid system is the best replica in view of increasing system reliability with less cost and no storage requirement [2]. A power system that has more than one generation resources is most suitable as unmet demand load of one resource can be compensated by the other resource or resources and for renewables, it has least generation cost and carbon emissions [3]. In the recent decade, Pakistan is facing severe energy crisis as thermal generation 978-1-5386-7027-9/18/$31.00 ©2018 IEEE



M. Haseeb Nawaz Department of Electrical Power Engineering USPCAS-E NUST Islamabad, Pakistan [email protected]



Rashid Wazir Department of Electrical Power Engineering USPCAS-E NUST Islamabad, Pakistan [email protected]



mostly depends upon the spiking prices of hydrocarbons. Renewables at the distribution end can reduce the transmission and distribution losses that are up to 20 percent in Pakistan. In the central region of Pakistan, there are good sunshine hours throughout the year and due to the sandy area, it has also a smooth profile of wind blow. This solar and wind profile can be used to model a hybrid system with cases of grid-connected and stand-alone system [4].Hybrid system with wind-solar energy can be implemented from small-scale power system such as for small home systems, apartments, commercial enterprises and educational institutes to large-scale power system such as mega cities in Nordic countries [5]. Hybrid power system uses back up batteries and quick response diesel generators as it faces reliability and stability issues due to intermittency nature of renewables. Power system must be sustainable at any cost to meet the load demanded. Hybrid system modeling involves multiple approaches such as programmable algorithms and built-in software tools for designing standalone or grid connected system with real-time data [6]. HOMER, RET Screen and IHOGA are most extensively used softwares for hybrid system designing across the world. A hybrid optimization model for electric renewables (HOMER) is developed by NREL (National Renewable Energy Laboratory, USA) and used in more than 192 countries for hybrid system modeling [7]. Sambeet Mishra and C.K. Panigrahi studied two cases of solar/wind/biogas hybrid system on HOMER software for remote electrification in India. They found PV/Biogas system more reliable and cost-effective than Wind/Biogas combination. Joan D Rozario and Shahinur Rehman from Bangladesh used biogas tool of Homer software with solar energy to increase the reliability of the system and provided a cost-effective solution[8]. Kiran Preet Kuar and Gursewak Singh analyzed remote electrification in a village area of India and use indigenous biofuels with solar energy to cater the demand of the area understudied. They used Homer



software to provide 1750 kW power from 1000 kW biogas plant and 750 kW solar energy[9]. W. Margaret Amutha and V. Rajini carried out a comparison of economic distance limit of grid extension and a standalone hybrid system consisting of solar, hydro, wind and batteries in the remote village of India. They concluded that results from HOMER software showed standalone renewable energy system is the most feasible and implementable solution than that of grid extension to the remote village[10]. Rumi Rajbongshi and Devashree TABLE I.



Borgohain analyse both the case of on-grid and off-grid village electrification on HOMER. They recommend that area under the break-even distance must be electrified through grid extension while in other parts solar/biogas/DG standalone must be commissioned [11]. In this study a hybrid system consisted of Solar/Wind/Biomass/Biogas energy sources has been design to cater electrical needs of small community of 50 houses. To the best of author’s knowledge no such study especially for southern Punjab has been conducted.



LOAD CALCULATION OF 50 HOUSES FOR SELECTED COMMUNITY Hours of Use



Total Load (Wh)



Sr. No



Appliance



Wattage



No. in use Winter



Summer



Winter



1



Tube Lights



40



2



8



8



640



400



2



Energy savers



24



2



14



14



672



1400



Summer



3



Air Cooler



75



1



0



8



0



440



4



Water Pump



746



1



1



1



746



350



5



Ceiling Fan



50



3



0



14



0



1492 1200



6



TV



175



1



2



2



350



7



Electric iron



1200



1



1



1



1200



432



Total Load for 1 house



3.608 kWh



6.308 kWh



Total Load for 50 houses



180.4kWh



315.74kWh



Fig. 4. Biomass (Crops residue) Technical Potential in Multan Fig. 1. Monthly load profile of selected community



Fig. 5. Biomass (Animal dung) technical potential in Multan



RESOURCE POTENTIAL ASSESMENT



Fig. 2. Daily Solar Irradiance for Multan



Fig. 3. Average Wind Speed for Multan



Pakistan is blessed with the enormous potential of renewable energy resources including solar, wind and biomass energy resources. By 2025, Pakistan plans for 5% electricity generation through renewables by replacing conventional energy resources. The private sector is being encouraged for the development and commercialization of renewable energy resources through active policies formulated by AEDB (Alternative Energy Development Board). Biomass mapping project sponsored by World Bank and ESMAP (Energy Sector Management Assistance Program) is one of the steps taken towards using indigenous renewable resources for generating clean energy[12, 13]. This mapping project shows that Punjab especially south Punjab has the potential



Fig. 6. Schematic diagram of PV-Wind-Biomass hybrid system TABLE II.



TOTAL MANURE PRODUCTION FROM AVAILABLE ANIMALS



No of Animals N Cows (100) Buffalos (50) TABLE III.



Per head manure generation (ton/year) mj 4.38 3.285



Total production of manure (ton/year) Mn 438 164.25



TECHNICAL PARAMETERS AND COST OF BIOGAS GENERATOR



Capital cost ($/kW) Fuel Cost ($/ton) Lower Heating Value (MJ/Kg) Density (kg/m3 ) Contents of Carbon (%) Contents of Sulfur (%)



300 53 5.5 0.720 5.0 0



of biomass resources. Punjab also has good potential of solar radiation due to its location. Solar, Wind and Biomass energy resources are discussed below for selected site. A. Load Assessment: This study is focused on designing a hybrid system capable of catering load demand of proposed community in district Multan. Monthly load profile for the proposed community is calculated by taking residential load needs into account. Fans, lights and electric motor pumps are basic appliances used for calculating the load. The load has been distributed in winter and summer seasons. In summer, the load is high due to excess use of ceiling fans and air coolers since the temperature is high in Multan. Winter load is low on the other hand. The primary load for the proposed community of 50 houses is 259.44kWh/day whereas peak load is 37.30 kW/day. The monthly load profile of the proposed community is shown in Fig. 1. Monthly load calculation is also shown in TABLE I. Winter load is 180.4kWh/day for five months while summer load is 315.74kWh/day for seven months. B. Solar energy resource potential: Multan, a major city of Pakistan located in south Punjab, has longitude and latitude values of 30.1575° N and 71.5249° E respectively. Real-time solar irradiance data has



Fig. 7. Selected wind turbine power curve TABLE IV. Sr.No 1 2 3



Specification Capital cost Replacement Cost Relative capacity



TABLE V. Sr.No 1 2 3 4 5



TECHNICAL PARAMETERS AND COST OF CONVERTER Value 300 300 100



Unit $/kW $/kW %



TECHNICAL PARAMETERS AND COST OF BATTERY



Specification Capital cost String size Initial State of Charge Minimum state of charge Maximum discharge current



Value 200 $ 2 100 % 20% 500



been fetched through Metrological High Precision (MHP) unit installed at MNS University, Multan. Four years solar irradiance data has been processed by taking hourly averages and then imported in HOMER Pro. Solar radiation data shown in Fig. 2 indicates that scaled annual average of solar irradiance is 4.94 kWh/m2/day over Multan. C. Wind energy resources potential Wind resources data is taken by NREL (National Renewable Energy Laboratory) resources available in HOMER Pro database. Data shown in Fig. 3 indicates that scaled annual average wind speed is 4.20 m/s for Multan. Wind speed potential is feasible for generating electrical energy. D. Biomass energy resources potential Pakistan is considered as an agriculture country which is rich in its biomass resources. The recently conducted biomass mapping project shows that Punjab has an enormous potential for biomass resource which includes crops residue and animal dung etc. Crop residues and animal dung both can easily be used for biogas production through combustion and digestion process respectively. Biogas production from both animal manure and crops residue are discussed further. 1) Biogas production by using Crops Residue: Four major crops of south Punjab including wheat straw, cotton stalk, sugar cane trash and bagasse are taken into account in this study [14]. Technical biomass feedstock potential of available crop residues is shown in Fig. 4.



2) Biogas production through animal manure: For the proposed community, an average of three cows per home is considered as suggested in some studies [15]. Production of manure by livestock is processed through anaerobic digesters for generating electricity. Total manure production [16] per year from available livestock of community is given by (1). ∑ Where: • • • •



(1)



Mn is total manure production per year Nj is specified number of group of animals n represent total no of animals mj represent per head manure production



Per head manure production from specific animals is taken from French agency [17]. Animal manure estimated to be generated through all animals is 1.65 ton/day calculated in Table II and shown in Fig. 5. Note that biomass fuel cost (53.25$/ton) is applicable for crop residues while animal dung is available free of cost since it is being fetched from the same community.



C.



Generic biogas fired generator whose capacity can be auto-set is used in this study. The generator has a minimum load ratio of 25% with a lifetime of 20,000 hours. Biogas generator’s properties including technical properties and costs are shown in above TABLE III. D.



Five components are included in designing of PV/Wind/Biomass hybrid system as shown in Fig. 6. These components are PV panels, wind turbine, biomass generator, batteries and converter. HOMER Pro search space capacity optimization is used. Detailed specifications including costs and technical parameters are discussed below. A.



PV Modules



Generic flat plate PV modules of 1kW capacity are used in this study. Capital cost (taken from local Pakistani manufacturers), per KW is 500$/kW whereas replacements cost is taken as 400$/kW. Lifetime of PV panels is 25 years and the de-rating factor is 80%. B.



Wind turbine



Different wind turbines are available in HOMER Pro database, but for this study, EOCYCLE E010 has been used due to its low cut-in speed i.e. 2.75m/s. Capital and replacement cost for wind turbine are 6000$ and 5000$ respectively. Wind turbine power capacity is 10kW and has a lifetime of 25 years. The power curve of a selected wind turbine is shown above in Fig. 7.



Power Converter



The converter is used to convert electrical energy from AC-DC and DC-AC. Since the output from PV panels is in DC form, converters are used to convert DC into AC to feed AC electrical load. Converter’s efficiency is 90% and lifetime is 15 years. Technical specifications with capital cost etc. are shown in above TABLE IV. E.



Batteries



System reliability is the most important and crucial parameter in power system operation. Since solar and wind energy are both intermittent in nature, so need of storage elements for the smooth running of the power system is essential. 6V Li-ion batteries with a nominal capacity of 1kW and lifetime of 25 years are used. Costs and technical parameters of the battery are given in above TABLE V.



HOMER PRO MODELLING HOMER Pro is originally developed by NREL and now is owned and operated by HOMER. It is used for optimization and designing of the proposed hybrid system in this study. It is a dominant tool for finding best possibly available hybrid system configuration for electrifying desired areas. Net Present Cost (NPC) is the main objective function upon which HOMER Pro decides before choosing the best hybrid system configuration. Simulations, sensitive analysis and optimization are the three main tasks performed by HOMER Pro [18, 19].



Biogas generator



SIMUALATIONS HOMER Pro simulates all available and possible hybrid system combinations to achieve the best cost-effective and feasible system configuration. HOMER Pro optimize different combinations of hybrid systems on basis of NPC with least cost system on the top. This paper includes different hybrid system configurations for electrifying the proposed community in Multan. Each hybrid system configuration is further classified in two categories; one using animal manure (Case 1: C1) while other use crops residue as a biomass resource (Case 2: C2). A.



PV-Biomass Hybrid System



This hybrid system configuration includes solar and biomass as input power sources to fulfill load needs of the proposed community. Optimization results for PV-Biomass hybrid system for both cases (C1 & C2) are shown in Table VI. B.



Wind-Biomass Hybrid System



In this case, wind and biomass are used as primary input resources for electrifying selected community. Optimization results of Wind-Biomass hybrid system for both cases (C1 & C2) have been shown in Table VI. C.



PV-Wind-Biomass Hybrid System



This hybrid system uses all three resources i.e. PV, wind and biomass to cater the electrical load needs of the selected community. Optimized results using this hybrid system for both cases (C1 & C2) are shown in Fig. 8, Fig. 9 and Table VI.



Fig. 8. Case 1: PV-Wind-Biomass (Animal Manure) Hybrid System Optimization Result for Multan



Fig. 9. Case 2: PV-Wind-Biomass (Crop Residue) Hybrid System Optimization Result for Multan TABLE VI.



OPTIMIZATIONS RESULTS FOR DIFFERENT HYBRID COMBINATIONS FOR MULTAN Multan



PV (KW)



Wind Turbines in No’s



Bio (kW)



C1



C2



C1



C2



C1



C2



C1



C2



PV,Bio



10



35



---



---



45



10



0.069



0.189



Wind,Bio PV,Wind, Bio



---



---



1



4



45



40



0.064



0.140



10



40



1



3



45



30



0.065



0.110



Hybrid System Type



COE ($)



RESULTS AND DISCUSSION Three different hybrid systems configurations for both case 1 and case 2 have been simulated and best optimization results on the basis of NPC and COE are shown in Table VI. Results show that use of animal manure prove to be economical solution among all possible options as manure is available free of cost. COE for PV-Bio, Wind-Bio and PV-Wind-Bio for case 2 of crops residue ranges between 0.11$ to 0.18$. While in case 1 when animal dung is used, COE is 0.06$ since fuel cost of biomass is zero in this case. Table VI shows that the use of animal dung as a biomass resource greatly increases the share of biomass in hybrid system configuration and reduces COE. Since, Multan has good potential for solar and biomass with an average potential of wind but all three hybrid system configurations are capable of catering load needs. The main focus of this study is to discuss the technoeconomic feasibility of different hybrid system configurations including PV-Wind-Biomass as input power.



CONCLUSION Developing energy systems, which can cater to energy crisis while keeping environmental sustainability into account are of extreme importance. There exists a research gap for designing of hybrid systems in developing countries like Pakistan, where country is facing worst energy crisis. The changing atmospheric conditions force stakeholders to stop using conventional energy resources and to move towards renewables. Hybrid energy systems are preferable in this situation as compared to the single source energy system. PV/Bio, Wind/Bio and PV/Wind/Biomass hybrid systems all are found feasible in case 1 (when animal manure is used) with COE approximately 0.06$ for all systems with more than 50% excess energy that can be sold back to the utility in case of the grid-connected system. PV/Wind/Biomass Hybrid system configuration for case 1 produces 89,226kWh (67.5%) electrical energy from Biomass resource, 27,365kWh (20.7%) from wind energy resource and 15,503 kWh (11.7%) from solar energy resource all over the year. Hybrid system for case 2 (when crop residue is used) produces 63.1% (173,540kWh) electricity from wind, 32.9% (57,153kWh) from solar and 3.99% (6925kWh) from biomass energy resources throughout the year. Biogas production from animal manure available also reduced COE due to its zero fuel cost as compared to crops residue. Furthermore, slurry will also be produced in such case when animal manure is used as a fuel for biogas digester. This can be used as fertilizer in fields as Multan is an agricultural land. This can also generate some revenue when sold to local farmers. Decentralized micro-grids for electrifying remote areas is a growing trend and Government of Pakistan along with AEDB (Alternative Energy Development Board) can play a vital role in the development of such projects. Tax reductions with a subsidy on renewables-related equipments



can motivate the private sector for investment in designing such microgrids. Since Pakistan is blessed with enormous resources of renewables which can be used for lowering its dependence on fossil fuels. This study will help in designing such hybrid systems for making remote areas fully independent of grids. percentage input share of biomass in hybrid system configuration. REFERENCES [1]



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