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  • 1. Fikari, Stamatia Gkiala
    et al.
    Ghaem Sigarchian, Sara
    KTH, School of Industrial Engineering and Management (ITM), Energy Technology, Heat and Power Technology.
    Chamorro, Harold R.
    KTH, School of Electrical Engineering (EES), Electric Power and Energy Systems.
    Modeling and Simulation of an Autonomous Hybrid Power System2017In: 2017 52nd International Universities Power Engineering Conference (UPEC), IEEE, 2017Conference paper (Refereed)
    Abstract [en]

    Renewable energy sources contribute to overcome the problem of environmental pollution and secure the energy independency every country needs, while at the same time the autonomous microgrids can improve the electrification rates of poorer countries. In this article, the modeling process and operation of an autonomous hybrid power system are studied for a hypothetical case study of electrification of a remote village of 100 inhabitants in Kenya. The microgrid consists of photovoltaics, wind turbine, batteries, diesel genset, basic loads of different priorities, water pumping and purification load. The system is modeled in Simulink MATLAB and is simulated in terms of power management. The primary load is categorized in different priorities, while water pumping and purification is used as deferrable load. The "load following" dispatch strategy is adopted. The outputs of the model are the power produced by the various sources and the power consumed by all loads during the simulation time, as well as the produced and consumed energy, information on the battery operation and the dumped power or the power shortage. Both the microgrid's operation and the performance of the dispatch strategy are evaluated considering the level on which the citizens' energy needs are covered and the efficient management of the produced energy. Managing the extra power or tackling the deficit of power in the system are the key issues to be addressed. After all, the model represents reliably the behavior of the microgrid and several improving actions are suggested, based on the results analysis.

  • 2.
    Ghaem Sigarchian, Sara
    KTH, School of Industrial Engineering and Management (ITM), Energy Technology, Heat and Power Technology.
    Design Optimization of a Complex PolygenerationSystem for a Hospital2018In: Energies, ISSN 1996-1073, E-ISSN 1996-1073, Vol. 11, no 1071Article in journal (Refereed)
    Abstract [en]

    Small-scale decentralized polygeneration systems have several energetic, economic and environmental benefits. However, using multiple energy sources and providing multiple energy services can lead to complicated studies which require advanced optimization techniques for determining optimal solutions. Furthermore, several parameters can influence the design and performance of a polygeneration system. In this study, the effects of heat load, renewable generation and storage units on the optimal design and performance of a polygeneration system for a hypothetical hospital located in northern Italy are investigated. The polygeneration system shows higher performance compared to the reference system, which is based on the separate generation of heat and power. It reduces fuel consumption by 14–32%, CO2 emissions by 10–29% and annualized total cost by 7–19%, for various studied scenarios. The avoided fuel and electricity purchase of the polygeneration system has a positive impact on the economy. This, together with the environmental and energetic benefits if the renewable generation and use of storage devices, indicate the viability and competitiveness of the system.

  • 3.
    Ghaem Sigarchian, Sara
    et al.
    KTH, School of Industrial Engineering and Management (ITM), Energy Technology. European Institute of Innovation and Technology, Sweden.
    Malmquist, Anders
    KTH, School of Industrial Engineering and Management (ITM), Energy Technology.
    Fransson, Torsten
    KTH, School of Industrial Engineering and Management (ITM), Energy Technology, Heat and Power Technology.
    Modeling and control strategy of a hybrid PV/Wind/Engine/Battery system to provide electricity and drinkable water for remote applications2014In: Energy Procedia: 2013 ISES Solar World Congress, Elsevier, 2014, Vol. 57, p. 1401-1410Conference paper (Refereed)
    Abstract [en]

    In this paper a small-scale energy system called emergency container is presented. This container has lots of applications and can be designed as stationary solution in remote areas such as rural electrification and a mobile solution for disaster situation, military purposes and exploration teams. In this study the container is a hybrid PV/wind/engine energy system that is designed to provide electricity and drinkable water for 1000 person in disaster situations. A transient model implemented in Transient Simulation System (TRNSYS) program is developed and performance of the system during one-year operation for two locations (Nairobi in Kenya and Nyala in Sudan) with relatively high solar insolation is analyzed. The result of the model is significantly important in order to choose the right size of the different components. Due to the fluctuations of solar and wind energy as well as the importance of the battery life cycle, there is a need to have a smart power management and an appropriate fast response control system. In order to achieve it and to fulfill the energy demand as much as possible through renewable energies, a dispatch strategy is introduced and a control algorithm is applied to the model. This control algorithm has increased system reliability and power availability. The transient simulation shows that the share of power generation by solar energy is 63% and 80% and the share of wind power is 27% and 12% in Nairobi and Nyala respectively. It means that most of the energy demand (around 90%) can be covered by renewable energy. This results in significant mitigation of environmental issues compared to using only diesel engine that is a common solution in disaster situations.

  • 4.
    Ghaem Sigarchian, Sara
    et al.
    KTH, School of Industrial Engineering and Management (ITM), Energy Technology.
    Malmquist, Anders
    KTH, School of Industrial Engineering and Management (ITM), Energy Technology.
    Martin, Viktoria
    KTH, School of Industrial Engineering and Management (ITM), Energy Technology.
    Design Optimization of a Complex Polygeneration System for a Hospital2018In: Energies, ISSN 1996-1073, E-ISSN 1996-1073, Vol. 11, no 5, article id 1071Article in journal (Refereed)
    Abstract [en]

    Small-scale decentralized polygeneration systems have several energetic, economic and environmental benefits. However, using multiple energy sources and providing multiple energy services can lead to complicated studies which require advanced optimization techniques for determining optimal solutions. Furthermore, several parameters can influence the design and performance of a polygeneration system. In this study, the effects of heat load, renewable generation and storage units on the optimal design and performance of a polygeneration system for a hypothetical hospital located in northern Italy are investigated. The polygeneration system shows higher performance compared to the reference system, which is based on the separate generation of heat and power. It reduces fuel consumption by 14-32%, CO2 emissions by 10-29% and annualized total cost by 7-19%, for various studied scenarios. The avoided fuel and electricity purchase of the polygeneration system has a positive impact on the economy. This, together with the environmental and energetic benefits if the renewable generation and use of storage devices, indicate the viability and competitiveness of the system.

  • 5.
    Ghaem Sigarchian, Sara
    et al.
    KTH, School of Industrial Engineering and Management (ITM), Energy Technology, Heat and Power Technology.
    Malmquist, Anders
    KTH, School of Industrial Engineering and Management (ITM), Energy Technology, Heat and Power Technology.
    Martin, Viktoria
    KTH, School of Industrial Engineering and Management (ITM), Energy Technology, Heat and Power Technology.
    Optimal planning and design method for complex polygeneration systems: A case study for a residential building in ItalyManuscript (preprint) (Other academic)
    Abstract [en]

    Polygeneration energy systems using multiple energy sources (e.g., wind, biomass, solar) and delivering multiple energy services (i.e., heating, cooling, and electricity) have potential economic and environmental benefits over traditional energy generation systems. However, for maximized benefits, such systems must be the correct size and have a suitable operating strategy implemented. In this study, an optimization model is proposed to identify the optimal design and operating strategy of a complex polygeneration system. The system includes photovoltaic modules, solar thermal units, wind turbines, combined heat and power units, energy storages (hot, cold, and electric), vapor compression and absorption chillers, and a boiler. The interactions between these units are managed based on the integrated operating strategies: following thermal load, following electric load and modified base load. A particle swarm optimization is used as an optimization algorithm and the objective function is defined to minimize the annualized total cost, fuel consumption, and carbon dioxide emissions using a weighting factor method. The careful incorporation of the realistic operation of the CHP is considered in the theoretical model. This includes the effects of the part-load operation and outdoor temperature on the efficiency and power output of the CHP. In addition, the size dependency of the unit cost of the chillers and CHP units over the search space is taken into account. With this approach, the achieved results would be as close to real conditions as possible. Six configuration scenarios are examined for a case study in a residential building complex located in northern Italy. It is concluded that implementation of the optimized polygeneration system has energetic, economic, and environmental conservation benefits in all these scenarios. The annualized cost and fuel consumption of the optimal solutions decreased by 3–19% and 10–37%, respectively, for the various scenarios compared to the separate generation system.

  • 6.
    Ghaem Sigarchian, Sara
    et al.
    KTH, School of Industrial Engineering and Management (ITM), Energy Technology.
    Malmquist, Anders
    KTH, School of Industrial Engineering and Management (ITM), Energy Technology.
    Martin, Viktoria
    KTH, School of Industrial Engineering and Management (ITM), Energy Technology.
    The choice of operating strategy for a complex polygeneration system: A case study for a residential building in Italy2018In: Energy Conversion and Management, ISSN 0196-8904, E-ISSN 1879-2227, Vol. 163, p. 278-291Article in journal (Refereed)
    Abstract [en]

    The operating strategy can affect the optimal solution and performance of a polygeneration energy system. In this study, the effect of operating strategies: following thermal load; following electric load; and modified base load on the optimal solution of a polygeneration system for a residential building complex in the northern part of Italy is investigated. For the optimal solutions, a comparative analysis is carried out considering the techno-economic and environmental performance of the system. The result elaborates on how the benefits achieved in a polygeneration system are influenced by the choice of operating strategy. In the building complex, implementation of the operating strategies shows considerable energetic, economic and environmental benefits compared to conventional separate heat and power generation. The ranges of annualized total cost reduction of 17-19%, carbon dioxide emission reduction of 35-43% and fuel consumption reduction of 30-38% are achieved for the various operating strategies. However, each of the operating strategies has its own advantages and drawbacks which emphasizes the importance of post-processing of the results in order to make the right choice. For example, the following thermal load shows the advantage of a higher carbon dioxide emission reduction. On the other hand, one drawback is its lower self-sustainability in terms of electric power compared to the other strategies.

  • 7.
    Ghaem Sigarchian, Sara
    et al.
    KTH, School of Industrial Engineering and Management (ITM), Energy Technology.
    Orosz, Matthew S.
    Hemond, Harry F.
    Malmquist, Anders
    KTH, School of Industrial Engineering and Management (ITM), Energy Technology.
    Optimum design of a hybrid PV-CSP-LPG microgrid with Particle Swarm Optimization technique2016In: Applied Thermal Engineering, ISSN 1359-4311, E-ISSN 1873-5606, Vol. 109, p. 1031-1036Article in journal (Refereed)
    Abstract [en]

    Designing an energy system using multiple energy sources including renewables and providing multiple energy services (e.g. electricity, heating) can enhance the reliability and efficiency of the system while mitigating the environmental footprint. However, interaction among various components, variation of the energy demand profile, and local ambient conditions make design optimization a complex task, and suggesting that efficient simulation tools and optimization techniques can help designers to determine the best solutions within a reasonable timeframe and budget. Previous work on a dynamic microgrid simulation tool called "u-Grid" used an exhaustive search technique to find optimum configurations. However, the high computational cost of the exhaustive search was a motivation to explore alternative optimization methods to improve the optimization process and also to enhance search speed. In this paper Particle Swarm Optimization (PSO) has been presented as a global optimizer and incorporated within the problem context. Results from the exhaustive search have been used as a benchmark for testing and validation of the newly introduced optimization technique. The result shows that the PSO method is an efficient technique which has the ability to determine a high quality design solution for an optimized microgrid with a relatively low computational cost. Applying this PSO-based algorithm to the case study has reduced the total computation time a factor of about 6 in a significantly smaller computational platform.

  • 8.
    Ghaem Sigarchian, Sara
    et al.
    KTH, School of Industrial Engineering and Management (ITM), Energy Technology, Heat and Power Technology.
    Paleta, Rita
    Malmquist, Anders
    KTH, School of Industrial Engineering and Management (ITM), Energy Technology, Heat and Power Technology.
    Pina, André
    Feasibility study of using a biogas engine as backup in a decentralized hybrid (PV/wind/battery) power generation system: Case study Kenya2015In: Energy, ISSN 0360-5442, E-ISSN 1873-6785, Vol. 90, no 2, p. 1830-1841Article in journal (Refereed)
    Abstract [en]

    In this study, a hybrid power system consisting of PV (Photovoltaics) panels, a wind turbine and a biogas engine is proposed to supply the electricity demand of a village in Kenya. The average and the peak load of the village are around 8kW and 16.5kW respectively.The feasibility of using locally produced biogas to drive a backup engine in comparison to using a diesel engine as backup has been explored through a techno-economic analysis using HOMER (Hybrid Optimization Model for Electric Renewables). This hybrid system has also been compared with a single diesel based power system.The results show that the hybrid system integrated with the biogas engine as backup can be a better solution than using a diesel engine as backup. The share of power generation by PV, wind and biogas are 49%, 19% and 32%, respectively. The LCOE (Levelized Cost of Electricity) of generated electricity by this hybrid system ($0.25/kWh) is about 20% cheaper than that with a diesel engine as backup ($0.31/kWh), while the capital cost and the total NPC (Net Present Cost) are about 30% and 18% lower, respectively.Regarding CO2 emissions, using a biogas engine as backup saves 17 tons of CO2 per year compared to using the diesel engine as backup.

  • 9.
    Ghaem Sigarchian, Sara
    et al.
    KTH, School of Industrial Engineering and Management (ITM), Energy Technology, Heat and Power Technology.
    Strand, Torsten
    KTH, School of Industrial Engineering and Management (ITM), Energy Technology, Heat and Power Technology.
    Spelling, James
    KTH, School of Industrial Engineering and Management (ITM), Energy Technology, Heat and Power Technology.
    Malmquist, Anders
    KTH, School of Industrial Engineering and Management (ITM), Energy Technology, Heat and Power Technology.
    Modeling and Analysis of a Hybrid Solar-Dish Brayton Engine2012In: Proceedings of the International SolarPACES Conference 2012, 2012Conference paper (Refereed)
    Abstract [en]

    Small-scale recuperated gas turbines with a highly efficient recuperator would appear to have considerable potential to be used in solar/fossil-fuel hybrid dish systems. The hybrid solar gas turbine can be configured in several different fashions, with the key difference being the relative positions of the solar receiver and burner as well as the operation mode of the burner.

    Steady state and transient models have been implemented in Engineering Equation Solver and the performance of various configurations are studied and compared. Layouts in which the receiver is located before the turbine (pressurized receivers) demonstrate higher performance compared to the one in which the receiver is located after the turbine (atmospheric receivers). The variation in operation throughout the year is taken into account and the performance of the system analyzed for two different cities (Yechang in China and Bechar in Algeria, with low and high solar insolation respectively). The integration of a solar receiver into a micro gas turbine reduces the yearly fuel consumption by around 15-16% in Yechang and up to 40% in Bechar. This will result in reductions of CO2 emissions as well as leading to lower daily operating costs. The hybrid nature of the Dish-Brayton system guarantees availability of the engine to meet the electricity demand whenever it occurs, allowing the system to supply dispatchable power.

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