Available online at www.sciencedirect.com ScienceDirect
Energy Procedia 103 ( 2016 ) 357 – 362
Applied Energy Symposium and Forum, REM2016: Renewable Energy Integration with Mini/Microgrid, 19-21 April 2016, Maldives Design of Solar-Biomass Hybrid Microgrid System in Sharjah
Chaouki Ghenaia and Isam Janajrehb
aSustainable and Renewable Energy Engineering Department, University of Sharjah, PO Box 27272, Sharjah, UAE bMasdar Institute of Science and Technology, Abu Dhabi, UAE
Abstract
Micropower optimization model is used in this study to design renewable energy-based micro grid system: solar- biomass hybrid system for the electrification of the city of Sharjah. The principal objective is to explore the available renewable resources in Sharjah and to determine the optimal configuration to meet the desired electric loads of the city. The hybrid system consists of electrical loads, solar resources, biomass resources, and system components such as solar photovoltaic, biogas generators, biomass power, battery and converters. Input information on the primary loads, solar and biomass resource availability, technology options, components cost, constraints, and controls are determined. Hourly simulations with sensitive analysis were performed to calculate the energy to and from each component to design the most favorable renewable energy-based system. The optimized results of the alternative renewable energy- based hybrid systems with different levels of contributions by renewable resources are presented in this paper taking into account the technology costs, energy resource availability and the efficiency of the renewable energy system.
© 2016 The Authors. Published by Elsevier Ltd. This is an open access article under the CC BY-NC-ND license (http://creativecommons.org/licenses/by-nc-nd/4.0/). Peer-review© 2016 The under Authors. responsibility Published of the by scientific Elsevier committee Ltd. of the Applied Energy Symposium and Forum, REM2016:Selection and/orRenewable peer-review Energy Integration under responsibility with Mini/Microgrid. of REM2016
Keywords: Renewable Energy, Solar, Biomass, Hybrid System, Microgrid, Optimization, Power Generation
1. Introduction
Microgrid is locally controlled energy system that uses different types of renewable energy resources (solar, wind, biomass, hydro, ocean), energy generators (Diesel, gasoline, biogas, biodiesel), energy storage systems (batteries, flywheel, hydrogen, thermal), loads (residential, commercial and industrial) and control equipment (inverters and converters) as shown in Figure 1.
* Corresponding author. E-mail address: [email protected]
1876-6102 © 2016 The Authors. Published by Elsevier Ltd. This is an open access article under the CC BY-NC-ND license (http://creativecommons.org/licenses/by-nc-nd/4.0/). Peer-review under responsibility of the scientific committee of the Applied Energy Symposium and Forum, REM2016: Renewable Energy Integration with Mini/Microgrid. doi: 10.1016/j.egypro.2016.11.299 358 Chaouki Ghenai and Isam Janajreh / Energy Procedia 103 ( 2016 ) 357 – 362
The micro grid energy system can be connected to the utility grid (synchronized with traditional centralized grid) or can operate separately off grid (disconnected from the grid and function autonomously) as shown in Fig.1. The advantages of using locally controlled micro grids are the reduction in the overall energy consumption and the environmental impact, improvement of the energy efficiency, reliability of the energy supply, transmission losses reductions, voltage control, and security of the energy supply. In case of emergency with prolonged outages (caused by major storms or natural disasters), the micro grid power system can provide backup to the utility grid and to be more energy independent from the grid. A simple micro-grid model with optimization of local renewable energy for on-grid area was investigated by Nazir et al. [1]. The proposed micro-grid model integrates the power plants driven by renewable energy sources employing micro hydro and photovoltaic system which is connected to grid system. The results show the performances of the power plants and the maximum power produced from renewable energy sources.The micro-grid model with the largest capacity MHP produced the lowest energy cost, greatest reduction of CO2 emission, and largest fraction of renewable energy. However, this system required high initial capital cost. The PV power generation was always recommended with a minimum capacity. Heydari and Askarzadeh [2] performed a micro grid power study by investigating the optimization of the size of a biomass-based PV power plant to supply the electrical power of agricultural wells located in Iran. The results show that the combination of PV and biomass systems could be an effective way to make a reliable and cost-effective hybrid energy system. Hybrid technology combination for electricity generation from a mix of renewable energy resources to satisfy the electrical needs in India was investigated by Sen and Bhattacharyya [3] and Kalappan and Ponnudsamy [4]. Four renewable resources: small-scale hydropower, solar photovoltaic systems, wind turbines and bio-diesel generators were considered [3]. Simulation, modeling and optimization using HOMER software was used to identify the optimal off-grid option and compares this with conventional grid extension. The results show that a hybrid combination of renewable energy generators at an off-grid location can be a cost-effective alternative to grid extension and it is sustainable, techno-economically viable and environmentally sound. Singh et al. [5] performed a computational simualtion and optimization of renewable energy systems using HOMER Pro Software. The optimization of solar, fuel cell, and biomass hybrid energy systems was investigated in this study. Yang et al [6] used simulation and modleing tools for sizing a stand alone hybrid solar-wind system with LSP technology by using genertic algorithm. The principal objective of this study is to explore the available renewable resources in Sharjah, United Arab Emirates and to determine the optimal configuration to meet the desired electric loads of the city using micro grid hybrid (solar-biomass) system.
2. Modeling and Simulation of Micro Power System
The micro power system modeling and simulation approach used in this study is discussed in details in this section. The micro power system is designed to generate electricity and heat based on the desired loads. The micro power system in general consists of electrical (solar PV; wind turbine; biomass power; biogas, gasoline, and Diesel generators; fuel cell) and thermal (space heating, water heating, biomass drying) energy systems; energy storage systems and conversion devices (AC to DC converters). Several combinations of electrical/thermal energy systems, conversion devices and storage technologies can be used. The system can model micro power systems connected to the grid and off grid. The loads, energy resources, components of the micro power system, and the operation of the integrated system are modeled in this study. The analysis and the design of the micro power system are based on the design options and the fluctuations of the key input data (intermittence of renewable energy resources such as solar and wind, and fuel prices for example). Simulation, optimization, and sensitivity analysis are needed to design the micro power systems based on the required loads. A technical feasibility study of each micro power system is performed based on the available technology and energy resources. An optimization approach is performed to simulate several candidate energy systems and determine the best micro power systems based on the technical constraints and to reduce the life cost of the system. A sensitivity analysis can also be performed to determine the Chaouki Ghenai and Isam Janajreh / Energy Procedia 103 ( 2016 ) 357 – 362 359 performance of the micro power based on the changes or the variations in the technology costs and energy resources availability.
2.1 Design of Micro Power Hybrid System
Renewable energy-based micro grid system: solar-biomass hybrid system for the electrification of the city of Sharjah (Latitude 25o 16’ north and Longitude 55o 19’ East) in the United Arab Emirates is proposed in this study. The Emirate of Sharjah is one of the Seven States of the United Arab Emirates. The Emirate of Sharjah comprises of the capital city of Sharjah and minor towns such as Kalba city and Khorfakhan. There is an increasing interest by the Sharjah government investment in implementing and utilization of renewable energies (solar water desalination, solar energy-generation plants, solar heating and cooling and public lighting using solar energy). The proposed study will explore the use of both renewable solar and biomass energy resources to design a micro grid power system in the city of Sharjah. The hybrid solar- biomass micro grid system (see Fig. 2) will include the following components: loads, solar PV, biogas (biomass based fuel) generator, batteries, and converters and inverters.
Fig. 1. Schematic of micro grid power system Fig. 2. Micro power solar-biomass hybrid system
2.2 Load and Solar/Biomass Resource Assessment
The 2012 load data was obtained from Sharjah Electricity and Water Authority (SEWA). The electricity was generated using 8 Diesel units, 35 gas turbines, and 8 steam turbines located in six different stations. The electricity generated in Emirates of Sharjah serves the Sharjah, Khorfakkan, and Kalba cities. Table 1 shows the 2012 minimum and maximum monthly loads in the city of Sharjah. The maximum loads for the year 2012 was obtained during the month of July and the minimum load was in January. The monthly solar horizontal radiation in Sharjah City is shown in Table 1. The annual average solar radiation in Sharjah is 8.30 kWh/m2/d. The solar radiation is available throughout the year, therefore considerable amount of solar power output can be generated. The type and the biomass resource availability in Sharjah includes crops and woody residues (forest residues - branches or stumps, and trees; primary mill residues - wastes generated by mill processes; and urban wood waste - waste from residential areas, as well as woody construction materials and used pallets). The proximate and ultimate analysis of the biomass fuels and the lower heating values of the fuels are needed to study the performance of the thermal chemical processes (gasification) used to convert the biomass to synthetic gas (biogas). In this study biogas or the gas derived from biomass is used as the primary fuel for the generators. For this study, the biomass resource used in the simulation was set to 500 tones/day from January to December (constant supply of biomass to generate the biogas fuel to run the generator). 360 Chaouki Ghenai and Isam Janajreh / Energy Procedia 103 ( 2016 ) 357 – 362
Table 1. Minimum and Maximum Loads and Solar Horizontal Radiation in Sharjah City
Month Min-Load Max-Load Solar-Horizontal (MW) (MW) radiation (kWh/m2/d) January 448 843 7.18 February 483 902 7.95 March 198 1069 8.73 April 714 1284 9.29 May 934 1694 9.35 June 1104 1777 9.06 July 1283 1922 8.79 August 1272 1892 8.83 September 1136 1837 8.54 October 877 1585 7.92 November 690 1233 7.21 December 529 956 6.69
3. Solar-Biomass Hybrid System Components and Sizing
The solar-biomass hybrid system is composed of solar flat PV system, biogas generator (Genset), batteries (generic Li-Ion batteries), and converters (Leonics S219CPH). A description of the selected parts for the solar-biomass hybrid system is summarized in Table 2. It is noted that a dual axis trackers was added in the PV system to maximize the power output for the system. The effects of temperature on the performance of the PV system were also included in this study. The performance of the PV system decreases with (1) increase of ambient temperature (high temperature in summer in the Sharjah) and (2) the accumulation of the dust on the solar panels (desert regions). The power output and the efficiency of the PV panel are given by:
ୋ PୀYf ൬ ൰ൣ1+Ƚ൫Tେ െ Tେ,ୗେ൯൧ (1) ୋ,ి
ଢ଼ౌ Efficiency୫୮,ୗେ = (2) ౌ ୋ,ి
WherePPV is the power output of the PV array [kW],YPV is the rated capacity of the PV array (power output under standard test conditions [kW]), fPV is the de-rating factor (account for soiling of the panels,
wiring losses,2 shading, and aging), GT is the solar radiation incident on the PV2 array in the current time step [kW/m ], GT,STC is the solar radiation at standard test conditions [kW/m ], DP is the temperature o o coefficient of power [%/ C], and TC is the PV cell temperature at the current time step [ C], and TC,STC is the PV cell temperature under standard test conditions [25oC]. For the biogas generator the slope for the variation of the fuel mass flow rate (kg/h) versus the power extracted from the generator was 0.35 (kg/h/kW). Based on the Biomass fuel consumption (kg/h) and the gasification conversion rate (0.70 kg biogas/kg biomass), the biogas fuel consumption (kg/h) and the biogas generator output power can be determined. Chaouki Ghenai and Isam Janajreh / Energy Procedia 103 ( 2016 ) 357 – 362 361
Table 2. Solar-Biomass Hybrid System Components
System Component Description Solar Photovotaics Solar flat PV, capacity = 10,000 kW, capital cost = $3000/kW, efficiency 14%, operating temperature = 47oC; temperature effects (temperature effects on power -0.5%/oC); derating factor
fPV = 80%, tracking system: dual axis tracking system; electrical bus DC, and life time = 25 years. Biogas Generator Generator: 50 kW Genset; capacity = 10,000 kW, capital cost = $500/kW, electrical bus AC, operation and maintenance = $0.03/hr. Fuel: biogas, Lower heating value = 5.5 MJ/kg, density = 0.72 kg/m3, carbon content = 2%, sulfur content = 0, fuel consumption = 0.35 kg/hr/kW, and life time 25 years.. Battery Generic Li-Ion Battery, capacity 20,000 strings, capital cost: $700 per battery, replacement $700 per battery, lifetime throughput (kWh) = 3,000, float life = 15 years, nominal voltage = 6 V, max charge current = 167 A, maximum discharge current = 500 A, and weight = 15 Lb. Converter Leonics S219CPH 5 kWh 48 Vdc, capacity 20,000 kW, and capital cost = $600/ kW
4. Results and discussions
The results of the optimal solar-biomass micro grid system are shown in Figure 3. The monthly average electrical production, the net present cost and the annualized cost (nominal cash flow) over the life (25 years) of the solar-biomass hybrid system are presented in Figure 3. The total electrical production from the hybrid system is 51,143,528 kWh/year with 37,621,420 kWh/year (74%) from the PV system and 13,522,106 kWh/year (26%) from the biogas generator. The total electrical production from the solar- biomass system represents 14% of the total yearly electrical demands (365 millions kWh/year) in the city of Sharjah.
Fig. 3. Monthly Average Electrical Production, Net Present and Annualized Total Cost of the Solar-Biomass Hybrid System
Figure 3 shows that the solar-biomass hybrid micro grid system can provide part (14%) of the total yearly electricity demand in Sharjah but the cost of the system is high. The results show that the initial capital cost of the PV system is high but the maintenance and operating cost is less. In the other hand, for the biogas generator the capital cost is less but the procurement of biomass fuel to produce biogas and the operation and maintenance of the generator and biomass over the 25 years is higher. The total net present cost of the integrated system is $154,901,904 with a levelized cost of the energy of 0.328 $/kWh. 362 Chaouki Ghenai and Isam Janajreh / Energy Procedia 103 ( 2016 ) 357 – 362
5. Conclusion
A simulation and modeling analysis is presented in this paper for the design of energy-based micro grid system. The micro grid hybrid system was designed based on solar PV and biogas generators integrated with batteries and converters to meet the desired electric loads of Sharjah city. Simulations and optimization and economic analysis were performed to test the performance and the cost of the proposed hybrid micro grid system. The results show that the solar-biomass hybrid system can provide up to 14% of the total yearly electrical demand in the city of Sharjah with the percentage shared by PV panel is 74% and 26% by the biogas generator. The cost of supply of the proposed renewable energy based electricity (0.328 $/kWh) is not cost effective and is less attractive to the users. New alternative and renewable biofuels with higher energy density for power generation from generators, and detailed sensitivity analysis to take into account the changes or the variations in the technology costs and energy resources availability need to be explored to increase the penetration of renewables in the energy mix and to reduce the cost of power generation from renewable energy systems.
References
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Biography Chaouki Ghenai is an Assistant Professor at the Sustainable and Renewable Energy Engineering Department at the University of Sharjah (UoS), and the Coordinator of the Sustainable Energy Development Research Group at the Research Institute of Science and Engineering (RISE). Dr. Ghenai research interests are renewable energy, energy efficiency, combustion, biofuels, alternative fuels, clean combustion technologies, waste to energy, sustainability, eco-design, energy-water nexus, energy planning and climate change mitigation assessment, modeling and simulation of micro gird power systems and air pollution.