An-Najah National University Faculty of Graduate Studies Electrification of Remote Clinics by Photovoltaic – Hydrogen Fuel Cell System By Makawi Diab Hraiz Supervisor Prof. Marwan Mahmoud This Thesis is Submitted in Partial Fulfilment of the Requirements for the Degree of Master of Clean Energy and Conservation Strategy Engineering, Faculty of Graduate Studies, An-Najah National University, Nablus-Palestine. 2013 III Dedication Praise be to Allah, Lord of the Worlds To the Prophet Muhammad Blessings and peace be upon him To my father To my mother To my brothers and sisters To my wife To my son (Diab), and my daughter (Tlane) To all friends and colleagues To my teachers To everyone working in this field To all of them, I dedicate this work IV Acknowledgments It is an honour for me to have the opportunity to say a word to thank Allah alone without partner who helped me to complete this research . I would particularly like to thank the supervisor Prof. Dr. Marwan Mahmoud , who helped me and encouraged me and gave me his time a lot throughout the entire research work. Also, acknowledgement is given to technicians of renewable energy and environment research unit in Palestine Polytechnic University to help them get the unit to conduct laboratory experiments. Special thanks also to Dr. Abdel Raheem abu Safa, Dr. Momen Sughayyer, Dr. Osama Ata, Dr. Ramzi Qawasma, Eng. F Fidaa Al- Jaafreah and Dr. Abdelkarim Daud for their valuable and helpful suggestions. V اإلقرار أنا الموقع أدناه مقذم الرسالة التي تحمل عنوان Electrification of Remote Clinics by Photovoltaic – Hydrogen Fuel Cell System . Declaration The work provided in this thesis, unless otherwise referenced, is the researcher's own work, and has not been submitted elsewhere for any other degree or qualification. Student's name: إسم الطالب: Signature: التوقيع: Date: خ:التاري VI Table of content Page Content No III Dedication IV Acknowledgments V Declaration VI Table of content VIII List of figure X List of table XI List of Abbreviations XII Abstract 1 Chapter One 2 Introduction 1 6 Chapter Two 7 description of photovoltaic-hydrogen fuel cell system components 2 8 Photovoltaic Power Generation 2.1 9 Photovoltaic technologies 2.1.1 10 Characteristics of a Photovoltaic module 2.1.2 12 Maximum Power Point 2.1.2.1 13 Hydrogen Production From Water 2.2 14 Hydrogen Storage 2.3 15 Fuel Cell Technology 2.4 15 Historical development 24.1 16 Functional principle of a Fuel Cell 2.4.2 18 Fuel cell types 2.4.3 19 Advantages and disadvantage of fuel cell 2.4.4 20 V-I Characteristics of Fuel Cell 2.4.5 21 The improvement performance of the PEMFC 2.4.6 21 PEM Fuel Cell stack 2.4.7 22 Chapter Three 23 modeling of photovoltaic-hydrogen fuel cell system 3 23 Modeling of Photovoltaic Generator 3.1 23 Modeling of Photovoltaic cell 3.1.1 25 Modeling of Photovoltaic module 3.1.2 26 Modeling of Photovoltaic array 3.1.3 27 PEM Fuel Cell System Model 3.2 28 Electrical output of an ideal PEM Fuel Cell 3.2.1 28 PEM Fuel Cell Thermodynamics 3.2.1.1 30 PEM Fuel Cell electrical equation 3.2.1.2 31 Actual PEM Fuel Cell 3.2.2 33 Activation losses 3.2.2.1 34 Ohmic losses 3.2.2.2 VII 34 Mass transport losses 3.2.2.3 36 Chapter Four 37 Experimrntal results and analysis of photovoltaic- hydroge fuel cell system 4 37 Basic Specifications of the Photovoltaic Panel 4.1 38 The I-V Characteristics 4.2 40 Hydrogen Production 4.3 40 Basic Specification of Electrolyzer 4.3.1 41 The Efficiency of Electrolyzer 4.3.2 45 The Voltage-Load Characteristics of Fuel Cell 4.4 49 Practical Connection of Fuel Cells 4.5 52 Chapter Five 53 Sizing photovoltaic modul and fuel cell stack 5 53 Electrical Appliances at Health Clinics 5.1 54 System Sizing of Small Clinics Electrification 5.2 55 Load Demand 5.2.1 55 Solar radiation 5.2.2 55 Sizing the PV generator 5.2.3 56 Sizing of the PEM Fuel Cell 5.2.4 56 Sizing an Electrolyser 5.2.5 56 Case study 5.3 58 Power management strategy 5.3.1 62 Cost Comparison between Fuel Cell and Battery 5.4 64 Chapter Six 65 Conclusion and future work 6 65 Conclusion and Recommendation 6.1 65 Future Work 6.2 67 References 72 Appendix 73 Appendix (A) 73 Solar Cell and Hydrogen Fuel Cell Trainer 90 Appendix (B) 90 PEM Fuel Cell Datasheet 93 Details 93 Additional Information 94 Appendix (C) 94 Solar Radiation and Load Clinic 96 Appendix (D) 96 Experiments of PEMFC 99 Appendix (E) 99 PV module and PEMFC Stack Datasheet الملخص ب VIII List of figure Page Figure No. 8 Block diagram of the Photovoltaic with fuel cell system 2.1 9 Photovoltaic cell, PV module and PV array 2.2 10 Type of Photovoltaic Technologies 2.3 11 The I-V and P-V characteristics of typical PV module 2.4 12 The I-V curve of a PV module for defining the FF 2.5 14 Principle of PEM electrolyzer 2.6 17 Basic principle of a PEM Fuel Cell 2.7 21 The V-I and V-P curves of a PEMFC 2.8 21 A collection of fuel cells (stack) to increase the voltage 2.9 23 Equivalent circuit of PV cell 3.1 26 The I-V characteristics of a typical PV module consisting of 36 cells connected in series 3.2 27 The I-V characteristics of 3 PV modules connected in series. 3.3 27 The I-V characteristics of 3 PV modules connected in parallel. 3.4 28 A simple equivalent circuit for a PEM fuel cell 3.5 31 The V-I characteristic of PEM fuel cell 3.6 32 An equivalent circuit of the actual PEM fuel cell 3.7 32 The P-V of the PEM fuel cell 3.8 34 The V-I characteristics of PEM Fuel Cell affected by the activation losses 3.9 34 The V-I characteristics of PEM Fuel Cell affected by the ohmic losses 3.10 35 The V-I characteristics of PEM Fuel Cell affected by the mass transport losses 3.11 37 The Emona HELEX adds in module 4.1 38 Photovoltaic Panel 4.2 39 Measuring circuit for determination of the I-V and P-V characteristics of a PV module 4.3 40 Characteristics of photovoltaic module at (G=580W/m2) 4.4 41 The PEM electrolyzer used in the experiments to produce H2 and O2 4.5 43 Current source supplying the electrolyzer 4.6 45 I-V characteristics of the PEM elctrolyzer 4.7 46 The P EM Fuel Cell 4.8 47 (PEM) Fuel Cell connection with the electrolyzer , load and measuring devices 4.9 IX 48 The (V-I) characteristics of PEMFC 4.10 49 The relationship between the output power of PEMFC and voltage through variation of the load 4.11 50 Two PEM Fuel Cell connected in series 4.12 51 Two PEM Fuel Cell are connected in parallel 4.13 55 Daily load curve of small clinics 5.1 57 Solar radiation pattern obtained on 24/4/2012 5.2 58 Logical block diagram for PMS 5.3 60 The load demand and the output power of the PV generator 5.4 60 The demand load after provides of PV modules 5.5 61 The volume of Hydrogen production 5.6 62 Connection of the PV modules to build the PV generator 5.7 X List of table Page Table No. 13 Techniques of maximum power point tracking 2.1 19 Existing fuel cell technologies 2.2 29 Enthalpy (H) and entropy (S) at 1atm, 298.15K for selected substances 3.1 38 Photovoltaic Panel Specifications 4.1 39 Measured data for PV CELL (G=580W/m2) 4.2 41 PEM Electrolyzer Specifications 4.3 44 Measuring results of V,I,t, Eel and ηe for production 4.4 44 PEM Electrolyzer performance 4.5 45 PEM Fuel Cell Specification 4.6 47 The output current and voltage of PEM fuel cell at different loads. 4.7 54 Electrical loads of the small health clinics 5.1 59 Specification of PV module 5.2 59 The size of the PV modules during the period of solar radiation 5.3 61 PEM Fuel Cell Specifications 5.4 61 Parameter of sizing PV modules with PEM fuel cell 5.5 63 Specifications of PEM fuel cell 5.6 63 Comparison of the total cost between two systems 5.7 XI List of Abbreviations Direct Current DC Alkaline Fuel Cell AFC Electrolyser component EL Fuel cell FC Current-Voltage I-V Molten Carbonate Fuel Cell MCFC Membrane Electrode Assembly MEA Maximum Power Point MPP Maximum Power Point Tracker MPPT Phosphoric Acid Fuel Cell PAFC Proton Exchange Membrane PEM Power-Voltage P-U Photovoltaic generator PV Solid Oxide Fuel Cell SOFC Standard Test Conditions STC Standard Temperature Presser STP XII Electrification of Remote Clinics by Photovoltaic – Hydrogen Fuel Cell System By Makawi Diab Hraiz Supervisor Prof. Marwan Mahmoud Abstract Palestinian health clinics in remote areas suffer from limited electric networks due to Israeli restrictions and lack of infrastructure fund from National Authorities. Most of these areas are distant from the main medium voltage transmission lines, which makes the unfeasible to connect them to the main electric power grids. Therefore, renewable energy sources could be more clean and feasible solution, especially solar and bio-waste sources. A typical energy consumption pattern for a small health clinic will be used. In addition, the theses would be providing modelling of the proposed system. Experimental results obtained for a reduced scale model parts built in the lab to give insight into the system technical details. Fuel availability and clean energy production in fuel cells, given its chemical reactions occurs inside as well as production of electricity for unlimited time, are of the main system specifications. This contribution provides a power management strategy for solar and fuel cell system scaled to suite a typical small clinics from rural areas in Palestine The proposed control strategy is based on a logic-based method that consider the states of power supply sources and the demand to combine and switch in between giving priority to the much stable source. In addition, experimental results for system part have been done on scaled system in the lab. 1 Chapter One Introduction 2 1. Introduction Remote areas far from cities mostly lack water and electric networks. The inhabitants of these areas face considerable difficulties since they have to depend on small inefficient electric diesel generators and obtain their drinking water at expensive cost from tractor tanks. The distance of these areas from the main medium voltage transmission lines (33kV) and their low power demands make it unfeasible to connect them with the main electric power grids. Solar electric power systems (photovoltaic generators) represent an effective appropriate solution to these villages to cover the power demands of the most necessary equipment such as lighting, TV, computer, water pumps, refrigerators, etc. . . . As known, health clinics that serve all villagers are very necessary. These clinics depend mostly on their own small electric diesel generator or they obtain the electric power from some houses, which posses diesel generators, at very high cost. The electric loads in such clinics are small and consume only small amount of daily energy. The electric loads are mainly represented in lighting (florescent or CFL- lamps), small vaccine refrigerator (196 liter), computer, sterilizer, small water pump, centrifuge, weight and overhead fan [1]. The total daily energy demand of such appliances is relatively low and lies mostly in the range between 2 and 5kWh which can be easily supplied by means of solar photovoltaic generators especially in countries of high solar energy potential as Palestine where the daily average on annual basis exceeds 5.2 kWh/m²-day while the registered annual sunshine duration 3 exceeds 2800 hours. Providing electric power to isolated rural clinic is not a new application since it has started during the seventies of the last century [2]. A large number of remote health clinics especially in Africa, Latin America and south Asia have been successfully operated by photovoltaic generators with consequently positive impact on the health sector of those areas. However, the new issue in this thesis is the use of a photovoltaic generator with hydrogen and fuel cell instead of using the traditional lead acid batteries as a storage media. The new system with fuel cell is promising to be more efficient and economic than the traditional system [3]. Furthermore the new system is friendlier to environment since it produces no toxic polluting gases as CO2, CO....etc, and has no lead or mercury in its components [2]. The backup system is the fuel cell which is known with its high efficiency and fast response, fuel flexibility and clean energy production , since chemical reactions occurs inside the fuel cell [4] .In addition production of electricity for unlimited time are of the main system specifications . The photovoltaic generator (PV) produces, during the day light, (variable solar radiation )enough electric power to cover the requirements of the different loads in the clinic while the excess power would be used to supply the electrolyser producing hydrogen .In the night the fuel cell will provide the clinic with the necessary power without using storage batteries. The system under study in this thesis consists of PV generator and water electrolyser to produce hydrogen, that would be stored in a special storage 4 tank, to be used in periods of low solar radiation by proton exchange membrane ( PEM ) fuel cell to produce electric power [5]. The main objective of this thesis is to develop a reliable appropriate design for a PV- Hydrogen Fuel Cell system to be used in providing a remote clinic with the total necessary daily energy. The other objectives are the followings:  Access to design solar electric power generators that preserve the environment without pollution.  Identification of the control system that is mostly appropriate and safe for such compound system.  Determination of the techno- economic feasibility of using fuel cell as backup system instead of storage batteries. The thesis consists of the six chapters: Chapter 1 Chapter 1 Provides an introduction to the notion of the Photovoltaic – Hydrogen Fuel Cell System for Electrification of Remote Clinics and the objectives the thesis. Chapter 2 Studies all the components used in the system, such as photovoltaic, PEM fuel cell, electrolyser and hydrogen storage tank. Chapter 3 Describes the mathematical modeling for each part of the Photovoltaic Hydrogen Fuel Cell system. Chapter 4 Experimental results conducted in the laboratory and analysis of the Photovoltaic –Hydrogen Fuel Cell System Chapter 5 Studies the sizing system and analysis. 5 Chapter 6 Presents the main conclusion of this thesis and recommendation for future work. 6 Chapter Two Description of photovoltaic-hydrogen fuel cell system components 7 2. Description of photovoltaic-hydrogen fuel cell system components This chapter provides an overview of the main components of photovoltaic-hydrogen fuel cell system. Such a system includes a source of power (PV), a hydrogen generator and hydrogen utilization units. The system provides electrical energy continuously without interruption. Photovoltaic power generation, which converts sunlight into electricity, and has many advantages, including the inexhaustible it's free and environment-friendly. The system consists of hydrogen production units called electrolyzers, which operate on hydrogen generation through the separation of the water using photovoltaic as a power source. Hydrogen which is produced by electrolyzer , has the advantage of being highly purified, and without emission of any greenhouse gases. Battery pack is one of the popular options in energy storage. Stability of battery pack depends on some factors such as: response time of battery, discharge rate, life time and battery life cycle cost. Batteries can be used for daily storage but for seasonal storage, batteries are not practical because of the low storage capacity. As fuel cells can convert hydrogen energy to electrical energy, storing energy, in the form of hydrogen, is another solution for both daily and seasonal storage of electrical energy. Hydrogen tanks are less costly than batteries and despite longer life , they need less maintenance [6]. 8 The figure (2.1) shows the components of a photovoltaic-hydrogen fuel cell system. Figure (2.1): Block diagram of the Photovoltaic with fuel cell system. 2.1 Photovoltaic Power Generation Photovoltaic cells convert solar radiation directly into electrical energy, also known as solar cell. The photovoltaic word refers to “photo” meaning light and “voltaic” refer to generate electrical. The cell is made up of semiconductor material such as silicon. It is composed of a P-type semiconductor and an N-type semiconductor. Solar radiation emitting the photovoltaic cell produces two types of electrons, negatively and positively charged electrons, in the semiconductors. The electric current flows through an external circuit between the two electrodes. Photovoltaic cells are connected electrically in series and/or parallel circuits to produce higher voltages, currents and power levels. Photovoltaic 9 modules consist of PV cell circuits. A photovoltaic array is the complete power-generating unit, consisting of a number of PV modules. A photovoltaic cell, PV module and array are shown in figure (2.2). Figure (2.2): Photovoltaic cell, PV module and PV array. 2.1.1 Photovoltaic technologies Basically, there are three types of technology used in the manufacture of photovoltaic cells: Crystalline silicon ( Monocrystalline , Polycrystalline); Thin Film; and Concentrator. These technologies are shown in figure (2.3). A crystalline silicon photovoltaic cell is manufactured from thin a slice cut of a single crystal of silicon and called (Monocrystalline (Mono c-Si)) whereas other types of less expensive cell and efficiency are called (Polycrystalline or Multicrystalline (Multi c-Si)) , are made of a silicon chips ,scraped from cylindrical silicon crystals and then chemically treated in furnaces to increase their electrical properties .The efficiency range of Crystalline silicon is between 11% and 20%, and represents approximately 85% of the market [7]. 10 Thin film module is made of depositing a thin film of semiconductor material onto a plate of another material such as plastic, steel or glass. These PV cells have an efficiency of between 6-8% and accounts for approximately 4.2% of the global market sales [8]. Commercially, there are more types of thin module depending on the active material are made: Amorphous Silicon (A-Si), Cadmium Telluride (CdTe), and Copper Indium Diselenide (CIGS) [9]. Concentrator photovoltaic (CPV) converts light into electrical energy but focuses the sunlight onto a small area on the solar cell. One of its most important advantages is that it uses less space compared with other technologies and has high efficiency of about 30% [7], but the cost of this technology is relatively expensive. Figure (2.3): Type of Photovoltaic Technologies. 2.1.2 Characteristics of a Photovoltaic module The performance of a photovoltaic module depends on manufacturing technology and operating conditions (solar radiation and temperature). The curve of current –voltage (I-V) which determines the behavior of a photovoltaic cell is represented in figure (2.3). 11 Figure (2.4): The I-V and P-V characteristics of typical PV module [10]. The main electrical parameters that describe the performance of a photovoltaic cell are: 1. Short circuit current (Isc): The value of (Isc) can be obtained by connecting the terminals of a module via an ammeter and measuring the current. The value of Isc changes in function of solar radiation and very little of temperature . 2. Open circuit voltage (Voc): It’s the voltage of a PV module measured at its terminals at no load. 3. Maximum power point (Mpp): The maximum power point of a photovoltaic is a unique point on the (I- V) or (P-V) characteristics and the power supplied in this point is maximum, where measured in Watts (W) .its value can be calculated by the product Vmax and Imax. 4. Fill Factor (FF): 12 The ratio of output power at maximum power point to the power computed by multiplying Isc by Voc, as illustrated in Figure (2.4). The FF is obtained according the following equation: (2.1) It is an important performance indicator. Figure (2.5): The I-V curve of a PV module for defining the FF. Typically, crystalline silicon photovoltaic FF module is between 0.67 and 0.74 and thin film is 0.7 [11],[12].If the I-V curves of two individual PV modules have the same values of Isc and Voc, the array with the higher fill factor (squarer I-V curve) will produce more power. Also, any impairment that reduces the fill factor will reduce the output power [12]. 2.1.2.1 Maximum Power Point To improve the efficiency of PV systems, various been performed. But, as solar energy is diffuse (less than 1 kW/m²), and photovoltaic cell efficiency is theoretically limited to 44%, efforts need to be strengthened on the energy transfer. This includes the design of the photovoltaic system and the energy management by seeking the Maximum Power Point (MPP). 13 Large amount of publications can be found on MPPT, and it is not easy to apprehend their differences and to estimate their performances [13]. The position of maximum power point is not known to determine this point used calculation models or by using a logarithms techniques, where vary in terms of complexity and simplicity, implementation, accuracy and the cost. Table (2.1) is shown the famous techniques used and simplicity in implementation [14]. Table (2 1): Techniques of maximum power point tracking . No. Methods of MPPT Techniques Cost (Component ,Sensor, Microcontroller) Percentage of matching with theoretical value (100%) 1 Constant Voltage (CV) Low 79.5 2 Short-Current Pulse (SC) Medium 90.7 3 Open Voltage (OV) Near to medium 94.6 4 Perturb and Observe (P&O a) Near to medium 98.9 5 Perturb and Observe (P&O b) Near to medium 99.3 6 Perturb and Observe (P&O c) Medium 87.7 7 Incremental Conductance(IC a) High 98.7 9 Incremental Conductance(IC b) Near to high 99.5 10 Temperature Methods High (90-97) 2 .2 Hydrogen Production From Water Many of technologies to produce hydrogen one of them is electrolyzer, which is an electrochemical device produced hydrogen from disassociate the water into hydrogen and oxygen by applied the electrical current from power supply (photovoltaic, which is suggested for this thesis). The electrical current must be direct current (DC) because it flows in one direction .An electrolyzer consists of electrolyte between two electrodes; one electrode is connected to positive of the power supply and produced oxygen. Another electrode is connected to negative of the power supply 14 and produce hydrogen .The amount of hydrogen generated is twice than oxygen, because the one mole of water consists of two moles hydrogen and one mole oxygen. The quantity of gases formed depends on the surface area of electrodes and the value of power supply. The main ways of water electrolysis are Alkaline and Proton Exchange Membrane. Water electrolysis in the anode place dissociates into protons, electrons, and oxygen is liberated, the protons pass through the membrane. The electrons pass Figure (2.6): Principle of PEM electrolyzer. through the power supply to the cathode.These electrons combine with protons to form hydrogen. PEM electrolyzer can have an overall efficiency of up to 85% [15]. The overall reaction of the water electrolyzer is: 2H2O O2 + 2H2 (2.2) 2.3 Hydrogen Storage Hydrogen is characterized by a low density of 0.08Kg /m 3 under normal conditions, so that its storage is difficult compared with liquid fuels. 15 Negative aspects of hydrogen and possible risks involved with its usage are primarily because hydrogen is colourless, odourless, tasteless and non-toxic under normal conditions. Hydrogen is potentially explosive; it has extremely low ignition energy, a low viscosity and high combustion, all of which are contributory factors to the hazards associated with hydrogen [16]. It can be stored in many basic configurations such as: compressed hydrogen gas in tanks or liquid hydrogen storage; or metal hydride; or complex chemical hydrides. The various storage types have different characteristics. The selection of a specific storage type depends on these characteristics, and mainly on energy density and cost of each type. Compressed gaseous hydrogen can be stored in pressure tanks at ambient temperature and 200 up to 700bar pressure. The most common materials used for hydrogen tanks are steel and aluminum. From all storage technologies, the compressed gaseous hydrogen has the longest history and cheapest price [17]. 2.4 Fuel Cell Technology The fundamental principle of the fuel cell is to convert chemical energy into electrical energy. A fuel cell is an electrochemical reactor which consumes fuel (in this thesis the fuel used hydrogen) and oxidation oxygen from air to convert the hydrogen and oxygen into pure water and electricity. 2.4.1 Historical development William Grove in 1839 was first discovered the basic principle of fuel cell by reversing water electrolysis to generate electricity from hydrogen and 16 oxygen .The principle that he discovered remain unchanged today [18]. Grove used four large cells, each containing hydrogen and oxygen, to produce electric power which was then used to split the water in the smaller upper cell. Commercial potential first demonstrated by NASA in the 1960’s with the usage of fuel cells on the space flights [19]. However, these fuel cells were very expensive .Fuel cell research and development has been actively taking place since the1970’s, resulting in many commercial applications ranging from low cost portable systems for cell phones and laptops to large power systems for buildings. The following are some applications of fuel cells: 1-Powering portable electronic equipment . 2-Providing off grid and backup power. 3-Powering homes . 4-Powering vehicles . 5-Powerplants . 2.4.2 Functional principle of a Fuel Cell The basic components of a single fuel cell are two electrodes, separated by an electrolyte. A fuel cell is an electro-chemical reactor which consumes fuel (hydrogen) and oxidant (oxygen from air) and converts them into water. In a fuel cell the equivalent of a combustion reaction takes place, however, At low temperature while separating electron and mass flow, fuel oxidation and oxygen reduction take place which and spatially separated at different 17 electrodes enabling the exchange of electrons. The reactions taking place in the fuel cell are more general in any electrochemical cell that require the transfer of electrons from the reactant to the electrode. These reactions are called redox-reactions. Materials, undergoing oxidation or reduction reactions, are called active materials. By definition: Oxidation reactions take place at the Anode. Reduction reactions take place at the Cathode. Separation of reaction sites is achieved by insertion of an electronically insulating but ionically conducting phase (electrolyte) between the site of reduction and the site of oxidation. Electrical current in the electrolyte is conducted by electrically charges particles (ions) exclusively. The ionic current is flowing only when the electrons taking part in the reaction are led across an external circuit. The reactions taking place at the electrodes can be described by equilibrium thermodynamic [20]. Figure (2.7): Basic principle of a PEM Fuel Cell The fuel cell, shown in figure (2.4) is described by the following reactions: Anodic reaction: H2 2H+ + 2e – (2.2) 18 Cathodic reaction: ½O2 +2H + + 2e - H2O (2.3) The overall reaction: H2+ ½O2 H2O (2.4) 2.4.3 Fuel cell types Fuel cell is classified as power generator because it can operate continuously, if fuel and oxidant are supplied. Five categories of fuel cells have received major efforts of research: (1) Polymer Electrolyte Membrane (PEM) fuel cells or PEMFCs (also called PEFCs), (2) Solid Oxide Fuel Cells (SOFCs), (3) Alkaline fuel cells (AFCs), (4) Phosphoric Acid Fuel Cells (PAFCs), and (5) Molten Carbonate Fuel Cells (MCFCs). PEM fuel cells are constructed using polymer electrolyte membranes (notably Nafion) as proton conductor and Platinum (Pt)-based materials as catalyst. Their noteworthy features include low operating temperature, high power density, and easy scale-up, making PEM fuel cells a promising candidate as the next generation power sources for transportation, stationary, and portable applications[21]. The applications of fuel cell depend on the values of the operation temperature and efficiency, the types of the fuel cell as shown in table(2.2).The Proton Exchange Membrane (PEMFC) and the Alkaline (AFC) operate at low temperature .PEMFC are used for the domestic power and mobile applications ,AFC for the space application. NASA first developed PEMFCs for the Gemini mission, but because PEMFCs had water-management problems, alkaline fuel cells were used through the 1990s. Improved PEMFCs promise to be more powerful, lighter, safer, simpler to operate, and more reliable. They will last longer, 19 perform better, and may cost much less than current alkaline fuel cells. PEMFCs use hydrogen fuel and produce only water so pure that NASA plans to use it as drinking water for spacecraft crews. NASA PEMFCs may also produce electricity for spacesuits, airplanes, uninhabited air vehicles, and reusable launch vehicles [19]. At medium temperature the Phosphoric Acid (PAFC) is operated and used for the co-generation application. Molten Carbonate (MCFC) and Solid Oxide (SOFC) are operated at high temperature more than 650C°. These two technologies are used for the high power application. There are significant differences in relation to temperature between the species used and the efficiency of every kind. To determine the appropriate type depends on the type of applications that would be used. Table (2.2): Existing fuel cell technologies [22], [18] . Type of Fuel Cell Electrolyte Fuel Temperature,[°C] Electrical Efficiency,[%] PEMFC Polymer H2 (20-80) 60 AFC Potassium hydroxide H2 (50-200) 60 PAFC Concentrated phosphoric acid H2 220 40 MCFC Molten carbonate melts CH4 650 45-50 SOFC Solid oxide CH4 (500-1000) 60 2.4.4 Advantages and disadvantage of fuel cell The fuel cell is very important for pollution disposal and greenhouse gases; the only product is water. It has a relatively higher efficiency and operates more silently than diesel engine. Maintenance isn’t complex because there are few moving parts in the system. The operating times are much longer 20 than batteries that to be disposed in hazardous waste landfills [28], the chemical energy to electrical energy is directly converted. The most important disadvantages of fuel cell, is in dealing with hydrogen in terms of production and storage [23] . In 2009, more than 35% cost reduction has been achieved in fuel cell fabrication [21] , But the cost of manufacturing fuel cells and materials are still higher than conventional sources (fossil fuels) and life time is limited which depends on the membrane[24] . 2.4.5 V-I Characteristics of Fuel Cell The theoretical voltage for the single PEMFC is about 1.23 V at standard Condition, the V-I and V-P characteristics of a PEMFC are illustrated in figure (2.5), but the actual voltage is less than 1V at open circuit condition and 0.5V at normal condition [10].The cell voltage less than its theoretical voltage due to the losses. The main source of losses can be divided into three; activation polarization dominates at low current densities in area I, is due to the slow charge transfer of the oxygen reduction and is the major source of losses. The second is governed by the ohmic polarization which is due to the resistance of the membrane and the third is bending down of the polarization curves due to the Concentration polarization. 21 Figure (2.8): The V-I and V-P curves of a PEMFC. 2.4.6 The improvement performance of the PEMFC The performance of the PEMFC can be improved by: a) Increasing the temperature of the PEM fuel cell. b) Increasing Pressure and flow rates of fuel (hydrogen) and oxygen. 2.4.7 PEM Fuel Cell stack A fuel cell stack consists of a multitude of single cells stacked up so that the cathode of one cell is electrically connected to the anode of the adjacent cell. In this way exactly the same current passes through each of the cells [25]. PEM fuel cells are connected between together in series to increase the voltage, and this structured is known as a stack and shown in figure (2.5). Figure (2.9): A collection of fuel cells (stack) to increase the voltage. 22 Chapter Three Modeling of photovoltaic-hydrogen fuel cell system 23 3. Modeling of photovoltaic-hydrogen fuel cell system This chapter presents the mathematical modeling for each part of the Photovoltaic Hydrogen Fuel Cell system. 3.1 Modeling of Photovoltaic Generator Three models are used to describe the equivalent electrical circuit of a PV cell module or array: the one-diode, the two-diode, and the empirical model. The most commonly used configuration is the one-diode model that represents the electrical behavior of the pn- junction [17]. 3.1.1 Modeling of Photovoltaic cell The equivalent electrical circuit of one-diode model consists of a real diode in parallel with a current source. The current source produces the current Iph and the current Id flows through diode. The current IL which flows to the load is the difference between Iph and Id and it is reduced by the resistances Rs and Rp [26]. Two resistances, Rs and Rp, are included to model the contact resistances and the internal PV cell resistance respectively. The values of these two resistances can be obtained from measurements or by using curve fitting methods based on the I-V characteristic of PV [27]. The equivalent electrical circuit for a PV cell or module is illustrated in Figure (3.1). Figure (3. 1): Equivalent circuit of PV cell. 24 The current source (Iph) depends on the solar radiation and the ambient temperature. The (I-V) characteristics of photovoltaic cell can be determined by the following equations [28]. The terminal current of the model (IL) is given by: IL = Iph –Id –Ip (3.1) Where, Iph: photocurrent from photovoltaic cell [A]. Id: is the current passing through none linear diode [A]. Ip: current through shunt resistance [A]. The photocurrent Iph is a function of solar radiation and temperature, it is determined from equation (3.2): Iph = [Isc +kI (Tc-Tr) ] G/Gn (3.2) Where, Isc: is the short-circuit of the cell at standard test condition (STC: Gn =1000W/m² and Tr =298.15K) [A]. kI: is the short-circuit current temperature co-efficient of the cell [A/ K]. Tc and Tr: are the working temperatures of the cell and reference temperature respectively. G and Gn: are the working solar radiation and nominal solar radiation respectively [W/m²]. The diode saturation current Id of the cell varies with the cell temperature, which is expressed in equation (3.3) as, 25 Id=Io [ e (q(VL+ILRs)/AkTc) -1] (3.3) Io: reverse saturation current of the diode [A]. q: is the electron charge [1.6021× 10 −19 C]. VL: output voltage of the photovoltaic cell [V]. Rs: series resistance of cell[Ω]. A: is the ideality constant of diode depend on the PV technology [1.2-3.3]. k: Boltzmann constant [1.38 × J/K]. The shunt current Ip is given by equation (3.4): Ip= (VL+ILRs)/Rp (3.4) Where Rp [Ω] is parallel resistance . 3.1.2 Modeling of Photovoltaic module A PV module is the result of connecting several PV cells in series in order to increase the output voltage. The characteristic has the same shape except for changes in the magnitude of the open circuit voltage [27], as shown in figure (3.2). 26 Figure (3.2): The I-V characteristics of a typical PV module consisting of 36 cells connected in series. [10]. The output voltage of a PV module is calculated by: Vmodule = n(Vd-ILRs) (3.5) Where n: is the number of PV cells connected in series in the module. Vd: is the voltage of the diode of the equivalent circuit of the cell [V]. 3.1.3 Modeling of Photovoltaic array The PV Arrays are composed of some combination of series and parallel of PV modules. The modeling of PV arrays is the same as modeling of the PV module from the PV cells. Modules in series, the (I–V) curves are simply added along the voltage axis. The total voltage is just the sum of the individual module voltages [10], as illustrated in Figure (3.3). 27 Figure (3.3): The I-V characteristics of 3 PV modules connected in series. For PV modules connected in parallel the total current is the sum of the currents of the modules whereby the total output voltage is equal to the voltage of one module, as shown in figure (3.4). Figure (3.4): The I-V characteristics of 3 PV modules connected in parallel. Practically the PV array will consist of a combination of series and parallel modules depending on the needed output power of the system. 3.2 PEM Fuel Cell System Model Modeling of the PEM fuel cell voltage is calculated from the energy balance between chemical energy in the reactants and electrical energy. 28 3.2.1 Electrical output of an ideal PEM Fuel Cell A simple theoretical model for a PEM Fuel Cell consists only of an ideal DC voltage source, as shown in figure (3.5). Figure (3.5): A simple equivalent circuit for a PEM fuel cell. The theoretical voltage Vth of the PEM fuel cell at STC can be determine by two mathematical methods, thermodynamics equations and electrical equations. 3.2.1.1 PEM Fuel Cell Thermodynamics The PEM fuel cell is converting chemical energy to electrical energy. The chemical energy released from the PEM fuel cell can be determined from the change in Gibbs free energy which is the difference between the Gibbs free energy of the product and the Gibbs free energy of the reactants [29]. The chemical energy released in a reaction can be thought of as consisting of two parts: an entropy-free part, called free energy G, that can be converted directly into electrical or mechanical work, plus a part that must appear as heat .The “G” in free energy is in honor of Josiah Willard Gibbs (1839–1903), who first described its usefulness, and the quantity is usually referred to as Gibbs free energy [10]. The chemical reaction is: H2+½O2 →H2O (ℓ) (3.6) Where (ℓ) indicate the water in liquid state . 29 The theoretical voltage value Vth of the PEM fuel cell can be determined by the equation (3.7): Vth= -∆G/nF (3.7) Where (Change free Gibbs energy): is the maximum possible amount electrical that a fuel cell can be produced [J/mol]. : is the number of electrons participation in reaction and in fuel cell is two electrons. F: is Faradays constant [96485.309 C/mol]. The change in free Gibbs energy is the difference between the electrical energy and heat. In chemical reactions, the difference between the enthalpy (H) of the products and the entropy (S) of the reactants tells us how much energy is released or absorbed in the reaction. The enthalpy of H2O depends on whether it is liquid water or gaseous water vapor [10] ,as illustrate in table (3.1). Table (3.1): Enthalpy (H) and entropy (S) at 1atm, 298.15K for selected substances [30] . ( ) ( ) State Substance 0.114 217.9 Gas H 0.130 0 Gas H2 0.161 247.5 Gas O 0.205 0 Gas O2 0.0699 -285.8 Liquid H2O 0.1888 -241.8 Gas H2O When the result is liquid water the enthalpy is -286J/mol. The equation (3.8) shows the relationship between electrical energy (∆H) and heat (T∆S) with the change in free Gibbs: 30 ∆G =∆H - T∆S (3.8) ∆H: is the change in enthalpy [J/mol]. T: is the temperature at STC [K]. ∆S: is the change in entropy [J/K/mol]. Substituting equation 3.8 in equation 3.7 the value of Vth of the PEM fuel cell at STC which is 1.229V . 3.2.1.2 PEM Fuel Cell electrical equation The theoretical voltage (Vth) across the two electrodes is: Vth=P/I (3. 9) Where P: electrical output power delivered [W]. I: output current [A]. The electrical power can be estimated by the following formula: P = We × r (3.10) Where, We: is the maximum electrical output of H2 at STC [237.2 kJ/mol]. r: the rate of flow H (mol/s) . The value of current can be estimated by the following formula: I = q × N × n × r (3.11) Where N: Avogadro’s number (6.022* molecule/mol). 31 Substituting the equations (3.10) and (3.11) in equation (3.9) the value of Vth of PEM fuel cell at STC which is 1.229 V. The ideal theoretical voltage Vth of PEM fuel cell can be determined by using two methods (thermodynamics and electrical equation), in the two methods the Vth is 1.229V as shown in figure (3.2). Figure (3.6): The V-I characteristic of PEM fuel cell. 3.2.2 Actual PEM Fuel Cell The actual fuel cell voltage Vactual is lower than the theoretically voltage Vth due to various losses .There are three main sources of losses: 1) Activation losses. 2) Ohmic losses. 3) Mass transport losses. A equivalent circuit for the fuel cell is consisting of a voltage source in series with some internal resistance shown in Figure (3.7). 32 Figure (3.7): An equivalent circuit of the actual PEM fuel cell. In general actual voltage of PEM fuel cell generates only about 60–70% of the theoretical maximum. Figure (3.8) : The P-V of the PEM fuel cell[10]. The power at zero current, or at zero voltage, is zero, there must be a point somewhere in between at which power is a maximum. As shown in the figure (3.8), that maximum corresponds to operation of the fuel cell at between 0.4 and 0.5 V per cell .Over most of the length of the fuel cell I –V graph, voltage drops linearly as current increases. The output voltage of the PEM fuel cells is defined by the equation (3.9) [30]: 33 ( { ( ) ⁄ } ) (3.9) Where VS: Stack output voltage [V]. N: Number of cells in stack. VS0: Cell open circuit voltage at standard pressure [V]. (RT/nF): The Tafel slope, usually in the range from 0.03 to 0.12 V for 24◦C. R is the universal gas constant, F is Faraday’s constant, T is the operating temperature and n=2 is the number of transferred electrons. PH2: Partial pressure of hydrogen inside the cell. PO2: Partial pressure of oxygen inside the cell. PH2Oc: Partial pressure of gas water. Pstd: Standard pressure. L: Voltage losses. 3.2.2.1 Activation losses Activation losses result from the energy required by the catalysts to initiate the reactions. The relatively slow speed of reactions at the cathode, where oxygen combines with protons and electrons to form water, tends to limit fuel cell power. The effect activation losses on the V-I characteristics is shown in figure (3.7). 34 The voltage at zero current, called the open-circuit voltage, is a little less than 1 V, which is about 25% lower than the theoretical value of 1.229 V [10]. Figure (3.9): The V-I characteristics of PEM Fuel Cell affected by the activation losses. 3.2.2.2 Ohmic losses Ohmic losses result from current passing through the internal resistance posed by the electrolyte membrane, electrodes, and various interconnections in the cell. Another loss, referred to as fuel crossover, results from fuel passing through the electrolyte without releasing its electrons to the external circuit. Figure (3. 10): The V-I characteristics of PEM Fuel Cell affected by the ohmic losses. 3.2.2.3 Mass transport losses Mass transport losses result when hydrogen and oxygen gases have difficulty reaching the electrodes. This is especially true at the cathode if water is allowed to build up, clogging the catalyst. 35 Figure (3.11): The V-I characteristics of PEM Fuel Cell affected by the mass transport losses. 36 Chapter Four Experimrntal results and analysis of photovoltaic- hydrogen fuel cell system 37 4. Experimrntal results and analysis of photovoltaic-hydroge fuel cell system In this chapter, the evaluation of the system components (photovoltaic, electrolyzer, fuel cell) was performed, the efficiency of each component was measured .Practical experiments on the characteristics and performance of the system components was carried out under the variable load. For the purpose of this study, a lab unit (PEMFC) produced by HELEX company," Solar and Hydrogen Fuel Cell Trainer " illustrated in figure (4.1) is used. The unit will be exposed to experiment tests to present the function of the system. Figure (4.1): The Emona HELEX adds in module. 4.1 Basic Specifications of the Photovoltaic Panel The panel output is a DC voltage when illuminated by either sun or lamp. 38 Figure (4.2): Photovoltaic Panel. Each PV panel includes 5 silicon cells, connected in series as shown in figure (4.2).The specification of PV Panel used in experiment is illustrated in table (4.1). Table (4. 1): Photovoltaic Panel Specifications Number of Cells Per Module 5 silicon cells, series Voltage at Maximum Power point 2.4V DC Current at Maximum Power point 200mA DC Power Output 0.48W Cell Area 37.2cm²(12*62*5) Open Voltage circuit 2.8V at 1000W/m² Short Current Circuit 250mA at 1000W/m² 4.2 The I-V Characteristics In order to measure the (I-V) and (P-V) characteristics of the used photovoltaic panel, a variable load was connected to the PV panel as illustrated in figure (4.3). The solar radiation intensity on the surface of the PV module was measured to 580 W/m 2 . The obtained results are illustrated in table (4.1). 39 Figure (4.3): Measuring circuit for determination of the I-V and P-V characteristics of a PV module. From the measured data in table (4.2) the Vmpp is equal 2.073V and Impp is equal 129mA and the maximum power point (MPP) is 267.4mW under the condition 580W/m 2 and the room temperature amounting to27 °C. Table (4.2): Measured data for PV CELL (G=580W/m 2 ) Load voltage Current Power (Ω) (V) (mA) (mW) Open circuit 2.736 0 0 32 2.384 75 178.8 16 2.073 129 267.417 8 1.461 180 262.98 4 0.859 210 180.39 2 0.447 215 96.105 1 0.233 219 51.027 0.5 0.111 221 24.531 0.25 0.095 222 21.09 Short circuit 0 221 0 Figure (4.4.a) illustrates the (I-V) characteristics of photovoltaic cell and the (P-V) of photovoltaic as shown in figure (4.4.b), the (I-V) and (V-P) depending on the measured data. 40 (a) The (I-V) Characteristics (b) The (P-V) characteristics Figure (4.4): Characteristics of photovoltaic module at (G=580W/m 2 ). 4.3 Hydrogen Production With reference to the thermodynamics data the amount of hydrogen can be obtained from decomposition water under standard temperature pressure (STP: 0 °C, 1 atm, and 22400 ml). For hydrogen one mol occupies (22400 ml) . As in our system, the volume of hydrogen is (10ml). So, 10 mol H2 = (10/22400 moles of H2) =0.00045 moles of H2. One mole of water occupies 18 ml, from the equation (2H2O(l) ⤍ O2(g) +2H2 (g)) that once as much H2O is needed to create the amount of H2, So 0.00045 moles of H2O needed to create the 10 ml of H2 =0.00045 mol H2, And 0.00045 mol H2O ×18 ml=0.0081 ml of H2.So,10 ml H2 (g) =0.0081 of H2O(l). Therefore, the volumetric ratio of H2 (g) : H2O(l) is 1234 :1. 4.3.1 Basic Specification of Electrolyzer The type of elctrolyzer used in experiment is Polymer Electrolyte Membrane (PEM), the specification is shown in table (4.3). 41 Table (4.3): PEM Electrolyzer Specifications. Power Consumption 800mW Required Voltage 1.4 to 1.8V DC Maximum Current 0.5A DC Rate of Hydrogen Production 3ml/h (at 0.5A) Consumption of Distilled Water 0.1ml/h (at 0.3A) Maximum Storage Capcity 10ml H2 and 10ml O2 4.3.2 The Efficiency of Electrolyzer The method used in this thesis to produce hydrogen is electrolysis of water. The type of the used electrolyzer is proton exchange membrane (PEM). This PEM is covered from both sides with catalyst material on either as shown in figure (4.5). Figure (4.5): The PEM electrolyzer used in the experiments to produce H2 and O2. The chemical reaction at the anode and cathode is as follows: At the anode, the water decomposed into positively charged hydrogen ions (H+) and Oxygen. The electrons are produced at the anode by this oxidation reaction: 2H2O(ℓ) O2(g) + 4H + (aq)+4e - 42 (ℓ, g and aq are liquid, gas and aqueous) At the cathode, addition of 4e to hydrogen in aqueous state is produces hydrogen gas. Four electrons with four ions of H2 are required to produce two moles of hydrogen gas: 4H + (aq) +4e - 2H2(g) The chemical overall equation for the electrolyzer is transfer of 4 electrons through the circuit, two molecules of hydrogen gas are created and one molecule of oxygen gas is created as previously illustrated in figure (2.13): 2H2O(l) + 4e - O2(g) + 2H2(g) The theoretical decomposition voltage for electrolyzer is 1.23V but the actual voltage value is higher due to the following reasons: 1- Electrode material. 2- Texture of electrode surface. 3- Type and concentration of electrolyte. 4- Current density and temperature. The difference between theoretical and actual voltage is called over voltage and must be made as low as possible. A current source was used to supply the PEM electrolyzer for studying of its performance and characteristics. The circuit of experiment is shown in figure (4.6). 43 Figure (4.6): Current source supplying the electrolyzer . The efficiency of the electrolyzer can be determined by: ηe = EH / Eel (4.1) Where ηe : Efficiency of the elctrolyzer. EH : Energy content of the hydrogen generated . Eel: Electrical energy used to produce that hydrogen. The energy content of H2 at normal temperature pressure NTP (NTP: 25 °C, 1 atm, and 22400 ml) and a volume of 22400 ml is equivalent to 286 kJ. In this case where 10 ml H2 was produced the energy content is 119 J. The electrical energy can be calculated as follows: Eel = V ×I ×t (4.2) Where, V: Terminal voltage of the current source. I: Current supplied to electrolyzer. t: Time needed to produce 10 ml of hydrogen gas. 44 The values of V, I and t where measured. The measuring results with the respective calculated values of Eel and ηe are illustrated in table (4.4). Table (4.4): Measuring results of V,I,t, Eel and ηe for production (10 ml H2 EH = 119J). No.Test Time (s) Current (mA) Voltage (V) Eel J (W.s) efficiency (%) 1 306 247 1.77 133.78 88.9 2 310 247 1.76 134.76 88.3 3 324 248 1.83 147.04 80.9 4 309 248 1.75 134.11 88.7 Average 312.3 247.5 1.77 137.42 86.7 The measured average value of electrical energy to produce 10 ml H2 is 137.42 W.s, which results an efficiency of electrolyzer amounting to 86.7%. To determine the I-V Characteristics of the electrolyzer an adjustable voltage source, was used .The voltage was increased from 1.2V at an increment of 0.05 V each 20 seconds .At end the corresponding current of the electrolyzer was measured as illustrated in table (4.5). Table (4.5): PEM Electrolyzer performance. Voltage at PEMEZ(V) Current into PEMEZ(mA) 1.2 0 1.25 0 1.3 0 1.35 0 1.4 0 1.45 4 1.5 24 1.52 70 1.55 94 1.6 120 45 It should be mentioned that the hydrogen bubbles started forming at V=1.45V. The measuring circuit for determining the I-V characteristics is shown in figure (4.7). Figure (4.7): I-V characteristics of the PEM elctrolyzer. The I-V characteristics of PEM electrolyzer is shown in figure (4.7). The current increases exponentially with voltage increasing. The voltage must be kept less than 1.8 V otherwise the electrolyzer will be destroyed as indicated in the datasheet. 4.4 The Voltage-Load Characteristics of Fuel Cell The type of fuel cell utilized in this thesis proton exchange membrane fuel cell (PEMFC).The basic specifications is shown in table (4.6). Table (4.6): PEM Fuel Cell Specification Type Polymer Electrolyte Membrane (PEM) Hydrogen Membrane Catalyst Material 0.4 mg/cm2 Pt Rate of Hydrogen Consumption 7ml/min (at 1.0 A DC) Voltage Output 0.4 to 1.0V DC Output Power 0.5W Input Terminals 2*Oxygen tube terminals 2*Hydrogen tube terminals 46 The PEMFC consists of electrolyte between two electrodes, inlets and outlets for H2 and O2 as well as electrical terminals for connecting of the load as illustrated in figure (4.8). Figure (4.8): The PEM Fuel Cell. The maximum theoretical output voltage of fuel cell which is a result of reaction between H2 and O2 is 1.23V.This value is obtained as discussed in chapter three. This theoretical voltage isn’t reachable because the various losses happen during in practical actual application. The decrease of these losses can be achieved by: 1- Improvement the catalyst materials. 2- Used high conductive materials. 3- Optimized electrodes structure. The connection of the experiment equipment for measuring the characteristics of the PEM fuel cell is shown in figure (4.9). 47 Figure (4.9): (PEM) Fuel Cell connection with the electrolyzer , load and measuring devices Both sides of elcetrolyzer are filled with distillated water and connected to the current source. When the hydrogen gas is formed and the stored capacity is 10 ml the current source must should be switched off. At this time started the experiment for the characteristics of the PEM fuel cell, changing the value of the load and record the values voltage and current for the PEM fuel cell .All thisvalues are shown in table (4.7). Table (4.7): The output current and voltage of PEM fuel cell at different loads. Load current voltage (ohm) (mA) (V) open circuit 0 0.825 32 23 0.752 16 44 0.724 8 82 0.683 4 148 0.631 2 245 0.556 1 360 0.457 0.5 512 0.346 0.25 631 0.239 48 The shape of the obtained experimental (V-I) of the PEMFC is shown in figure (4.10) and the maximum voltage of the PEMFC is less than theoretical voltage 1.23 , which is correct due to the mentioned losses . Figure (4.10): The (V-I) characteristics of PEMFC. The PEMFC maximum output power is achieved between (0.25 and 2) ohm and this shown in figure (4.11) .The maximum power point drops after the fuel cell has consumed the remaining gas within its casing. The rate of consumption of gases is not constant and is affected by the power delivered to the load. The output power would drop when prevent the gas flow into device. 0 0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.8 0.9 1 0 200 400 600 800 Current (mA) V o lt ag e (V ) 49 Figure (4.11): The relationship between the output power of PEMFC and voltage through variation of the load. ηfc = Eel / EH (4.3) Where ηfc: Efficiency of the PEM fuel cell. Eel : Electrical energy generated from the PEM fuel cell (Power*time). EH : Energy content of the hydrogen . The electrical energy output delivered to the load from the PEMFC is equal (47J) and from the experiment the hydrogen is 10 ml ,so the energy contained in it is equal (119J). Therefore the efficiency of the PEM fuel cell is 39.5%. 4.5 Practical Connection of Fuel Cells Fuel cells can be connected series or parallel to increase the output power, where multiple of identical fuel cells are packaged together is known as stack. 0 50 100 150 200 250 300 0 100 200 300 400 500 600 700 800 Power(W) V o lt ag e (V ) 50 To produce a higher output voltage from fuel cells there is one way, the fuel cells have to be connected in series and the experiment circuit is shown in figure (4.12). Figure (4.12): Two PEM Fuel Cell connected in series. Both fuel cells are connected in series and supplied with hydrogen and oxygen from the electrlyzer. The electrical terminals of fuel cells are connected in series. To produce a higher output current from fuel cells, they must be connected in parallel.The experiment circuit is shown in figure (4.13) and the inlets and outlets for gases are the same connections as in series but the connection of the electrical terminals of the fuel cells is parallel through diodes .Using diodes is very important because the current would flow from the fuel cell output with higher output voltage value into the fuel cell with the lower output voltage ,this current flow in fuel cell must be avoid otherwise the fuel cell will be destroyed. 51 Figure (4.13): Two PEM Fuel Cell are connected in parallel. Both fuel cells are connected in parallel and supplied with hydrogen and oxygen from the electrlyzer. The electrical terminals of the fuel cells are connected in parallel. The current readings from the output of the fuel cells are about double than one fuel cell. 52 Chapter Five Sizing photovoltaic module and fuel cell stack 53 5. Sizing photovoltaic modul and fuel cell stack This chapter focuses on sizing of the PV array and the PEM fuel cell depending on the load and solar radiation. 5.1 Electrical Appliances at Health Clinics The energy demands of a health clinic and the climate condition will be critical factors in the selection of the most appropriate renewable electrification technology. The electrical devices used in rural health clinics are listed here after: 1- Vaccine Refrigeration, vaccines are stored for up to one month and require a stable temperature between 0°C and 8°C, Once the vaccines have been exposed to temperatures outside this range, potency is forever lost[15]. 2- Lighting, electric light greatly improves emergency treatment, birthing, maternity care, surgery, administrative tasks, and other medical functions. 3- Blood Chemical Analyzer, it’s a medical device that analyses blood sample by count the cell number (red blood cells, white blood cells and platelets) and Hemoglobin concentration. This device consists from diaphragm pump, photo cell, suction and aperture. 4- Sterilization, Sterilization requires rather high temperatures, approximately 120°C. 5- A microscope apparatus and a microscopic method that uses the microscope apparatus for examining a sample or a specimen, such as but not limited to a tissue sample or a tissue specimen. 54 6- A centrifuge is a piece of clinics equipment, generally driven by an electric motor that puts an object in rotation around a fixed axis, applying a force perpendicular to the axis. It’s used to separate of blood samples according to density of the components from each other. [33]. 7- Blood chemistry analyzer, used to measure the concentration of some solute materials in blood such as blood sugar concentration and urea concentration. This device needs AC voltage to for its operation. Table (5.1) shows the common equipment types used in rural health clinics including typical power ratings. The time of day power needed and the peak power demand have an impact on the sizing of equipment [32]. Table (5. 1) :Electrical loads of the small health clinics Equipment Quantity Power (W) Time (Hours ) Total Energ y(kW h/day) Refrigerator-Vaccine 1 60 10 0.6 Refrigerator-Non-med 1 300 5 1.5 Centrifuge 2 242 4 1.94 Microscope 2 20 6 0.24 Blood Chemical Analyzer 1 88 4 0.35 Hematology Analyzer 1 230 4 0.92 Small electrical application (Radio +Mobile charger) 1 230 2 0.46 Tube -Fluorescent 4 40 8 1.28 Desktop Computer 1 230 4 0.92 Total 8.2 5.2 System Sizing of Small Clinics Electrification The photovoltaic generator produces power, when solar radiation is sufficient, for electric power demands different loads while the excess 55 power will be stored and partially used for hydrogen production. When solar radiation is absent, the fuel cell will provide the necessary power .In this thesis, the load profile of a rural clinic and the average daily solar radiation in Palestine are considered in the system design. 5.2.1 Load Demand A typical daily load curve for a small clinic is given in figure (5.1). The maximum consumed power during a day is 670W and energy consumption is 8.2kWh/day. Figure (5.1): Daily load curve of small clinics. 5.2.2 Solar radiation The geographical location of Palestine is within a considerably high solar belt represented in 5-6 kWh/m 2 –day. The daily average of solar radiation in Palestine amount to 5.4 kWh/m 2 –day . 5.2.3 Sizing the PV generator The important parameters for system sizing are the average daily solar radiation energy and the load consumption. These parameters can be used 56 to calculate the peak power of the PV generator. The size of PV generator can be determined by the equation (5.1): Area of PV=Ed / [ASR* ηpv *ηch *ηIN *ηel*ηfc] Ed: daily energy consumption. ASR: average daily solar radiation. ηpv :efficiency of photovoltaic. ηch: efficiency of charger controller. ηIN: efficiency of Inverter. ηel: efficiency of electrolyzer. ηfc: efficiency of PEM fuel cell. 5.2.4 Sizing of the PEM Fuel Cell The PEM fuel cell supply is required when there is not enough solar radiation and in the night. Fuel cells use hydrogen as fuel under normal temperature conditions. Its power can be calculated according to the maximum load required. 5.2.5 Sizing an Electrolyser The rated power of the electrolyzers can be calculated by the equation (5.3): Pel =PPV-PL,min (5.3) Pel : rated power of the electrolyzer. PPV: output power of PV modules. PL,min : minimum of the clinic load . 5.3 Case study A typical solar radiation pattern is for one average day at southern Palestinian villages shown in Figure (5.2) [34]. The solar radiation is 57 obtained for 24 hour on 24/4/2012, and the solar radiation average in this daylight (6:30 AM to 19:30 PM) is 0.538 kW/m². Figure (5. 2): Solar radiation pattern obtained on 24/4/2012. The day is classified into three periods for operating the system: 1- Morning (5:00 AM – 8:30 AM): in this period of day the sun rise and the solar radiation will increase slowly so the fuel cell will provide the needed low power demand. 2- (8:30 AM – 6:30 PM): during this period the solar radiation will increase to reach its maximum values. Thus the power output from the PV generator can meet the load demand until the solar radiation decreases the sunset. During this period the Fuel cell still shutdown. 3- During the time (6:30 PM – 5:00 AM): where no sunlight exists, the PV power output is zero. The fuel cell must give the required power to meet the load demands. 58 5.3.1 Power management strategy The main aim for the applied Power Management Strategy (PMS) in the adopted system is to satisfy the load requirements of the clinic use. The operation of the fuel cell should satisfy the load pattern requirements in terms of duration and power level for the various operation times. Figure (5.3): Logical block diagram for PMS. The adopted PMS is must be built to provide the operating modes under variable weather conditions to ensure the satisfaction of the power requirements. The logical block diagram for PMS is shown in Figure (5.3). It is built on the bases of power sources states and load demand pattern with the priority given to solar energy supply, thus if power difference 59 between solar and load P ˂ 0, based on instantaneous power supply, then the necessary power to satisfy the load is provided by the fuel cell. The PV modules provides the necessary power to meet the total load demand, and the excess power from the PV modules will provides the electrolyzer to produce the hydrogen . To determine the size of the PV modules during the day is divided into two periods, the first period is the period of solar radiation sufficient to provide the load demand. The following illustrate calculate the size of the solar generator required in this period: The energy consumed in this period is 7150kWh, The area of photovoltaic needed to supply the clinic load is about 11.6 m 2 and using Mono- crystalline with module area 1.67m 2 , and the number of modules to installation is 7 module, as illustrated in table (5.2). Table (5.2): Specification of PV module Parameter Nominal Value Peak Power (W) 250 Maximum Power Point Voltage(V) 48.5 Maximum Power Point Current(A) 5.15 Open Circuit Voltage (V) 58.1 Short Circuit Current(A) 5.58 Size of Module (mm) 1580*1058*46 Figure (3.5) shows the output power of the 7 PV modules and the load demand. Table (5. 3): The size of the PV modules during the period of solar radiation. Ed (kWh) ASR (kWh/m 2 ) ηpv(%) ηch(%) ηIN(%) Area of PV(m 2 ) No. module 6950 5400 14.5 90 85 11.6 6.94 60 Figure (5.4): The load demand and the output power of the PVgenerator. Figure (5. 5 ): The demand load after provides of PV modules. The exceeded energy of PV modules in the first period is 1.166 kWh, which used in the second period and the output energy of fuel cell is 0.460 kWh. The second period the fuel cell provides the demand load which is 1.920 kWh, and the maximum consumption is about 270W ,the size PEM fuel cell is Pfc=300W. This mean the rated power of fuel cell is 533W. Stack electrical efficiency for commercial fuel cell is about 43%, nominal power is 533 W and operating temperature of fuel cell is 53°C performances as given in Table (5.2). 61 Table (5.4): PEM Fuel Cell Specifications Parameter Nominal Value Nominal Stack Power (W) 533 Nominal Stack Voltage(V) 35 Nominal Stack Current(A) 2.7 Nominal Stack Efficiency (%) 43 Number of cells 42 To determine the size of the PV generator must take into account the efficiency of electrolyzer and the efficiency of the PEM fuel cell. The area of photovoltaic needed to supply the clinic load is about 7.16 m 2 and using Mono-crystalline with module area 1.67m 2 , and the number of modules to installation is 4 module, as illustrated in table (5.5).The figure (3.5) shows the output power of the 4 PV modules and the demand load . Table (5.5): Parameter of sizing PV modules with PEM fuel cell. The volume of hydrogen production during the day 24/4 is shown in figure (5.5). Figure (5. 6): The volume of Hydrogen production. Ed (kWh) ASR (kWh/m 2 ) ηpv (%) ηch (%) ηIN (%) ηel (%) ηfc (%) Area of PV(m 2 ) No. module 1460 5400 14.5 90 85 85 40 7.16 4.29 62 The total necessary PV modules amount 11.3 modules there for we use 12 modules with following connections to produce a nominal DC voltage of 48V for supplying of the electrolyzer and electrical appliance in the small clinics. Figure (5. 7 ): Connection of the PV modules to build the PV generator The above PV generator figure (5.7) has an open circuit voltage and short circuit 58V and 5.58A which correspond to a peak power of 3kW. 5.4 Cost Comparison between Fuel Cell and Battery The capacity of the battery can be determined by the equation (5.): CAH=Ed/ [DOD* ȠB*VB] (5.) CAH: Ampere hour capacity. DOD: Depth of discharge. ȠB: efficiency of battery. VB: voltage of battery. The CAH for one day needed to supply the load 8.2kWh is 804Ah, for two days CAH must be doubled (1608Ah) .The number of batteries is 24 63 (2V/100Ah) where each two batteries have to be connected in series to deliver 24V at the output of the storage system. The specification of the fuel cell is illustrated in table (5.6). Table (5. 6): Specifications of PEM fuel cell. Parameter Nominal Value Nominal Stack Power (kW) 1.26 Nominal Stack Voltage(V) 24.3 Nominal Stack Current(A) 52 Nominal Stack Efficiency (%) 46 Cost($) 4500 In table (5.7) illustrated the prices the component for each system Table (5. 7): Comparison of the total cost between two systems. Cost system with Battery($) Cost system used Fuel cell ($) Photovoltaic 1575 3500 Battery 13440 - Electrolyzer - 1000 Fuel cell - 4500 Total 15015 9000 In the table (5.7) the cost of using fuel cell is less storage battery, the difference of the costs of the two designs is 6015 $.The system depending on battery has higher cost storage for long intervals is required .The system of fuel cell can store energy for long time at lower cost since storage of produced hydrogen is in tank. 64 Chapter Six Conclusion and Future work 65 6. Conclusion and future work 6.1 Conclusion and Recommendation Main purpose of this thesis is to investigate electrification of health clinics far from the electric grid, by environment friendly system consisting of photovoltaic generators and fuel cells. The advantages of this system in comparison of using storage batteries are represented in the lower cost and in protection the environment. Clinics need electrical power throughout the day without a break because they contain vaccines and this system supplies electricity to the clinic load daytime and night without interruption. During the process of the fuel cell experiments show that it should be supplied with hydrogen for three minutes before taking readings because membrane initially need to stimulate the production of electricity and in order that the fuel cell operates at nominal efficiency. Distilled water should be used in the electrolyzer where the membrane is put in the process of separating water into hydrogen and oxygen. Non- distilled water leads to the destruction of the membrane of the electrolyzer. In this system the electrolyzer to produce hydrogen consumes a part of electrical energy generated from PV, and can be dispensed with using other elements. Fortunately, hydrogen can be generated from bio-waste material available locally using economic technologies. 6.2 Future Work This thesis establishes a new direction for research in Palestine related to Fuel cell and PV systems. Studies that can be carried out in the future are 66 summarized in the following: 1- Management process control of pressure and flow of hydrogen gas through the electrical and mechanical system. 2- Design a control system to regulate the functioning of the system depending on the load demand. 3- Feasibility study for fuel cells and compare with other systems for different applications. 67 References [1] Antonio C.Jimenez ,Ken Olson ,Renewable Energy for Rural Health Clinics, ,1998. [2] Marwan M. Mahmoud , Imad Ibrik, Field experience on solar electric power systems and their potential in Palestine ,Renewable and Sustainable Energy Reviews, 2003;7:531-541. [3] Timothy E. Lipman, Jennifer L. Edwards, Daniel M. Kammen, Fuel cell system economics: comparing the costs of generating power with stationary and motor vehicle PEM fuel cell systems. [4] Jean-Marc Joubert 1, Bernard Lachal, Klaus Yvon, Evaluation of a 5 kWp photovoltaic hydrogen production and storage installation for aresidential home in Switzerland Pierre Hollmuller ,International Journal of Hydrogen Energy ,2000. [5] M. Sedighizadeh, and A. Rezazadeh ,Comparison between Batteries and Fuel Cells for Photovoltaic System Backup, World Academy of Science, Engineering and Technology 36 2007. [6] Halimeh Rashidi, Saeed Niazi, Jamshid Khorshidi , Optimal Sizing Method of Solar-Hydrogen Hybrid Energy System for Stand- alone Application Using Fuzzy Based Particle Swarm Optimization Algorithm, Australian Journal of Basic and Applied Sciences, 6(10): 249-256, 2012 ISSN 1991-8178. 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[13] Ghislain REMY, Olivier BETHOUX, Claude MARCHAND, Hussein DOGAN, Review of MPPT Techniques for Photovoltaic Systems, Laboratoire de Génie Electrique de Paris (LGEP) / SPEE-Labs, Université Pierre et Marie Curie P6, Université Paris- Sud 11,FRANCE. [14] ROBERTO FARANDA, SONIA LEVA, Energy comparison of MPPT techniques for PV Systems, ISSN: 1790-5060, Issue 6, http://www.evoenergy.co.uk/solar-pv/our-%20%20%20%20%20%20%20%20%20%20%20%20%20technology/pv-cell-comparison/ http://www.evoenergy.co.uk/solar-pv/our-%20%20%20%20%20%20%20%20%20%20%20%20%20technology/pv-cell-comparison/ 69 Volume 3, June 2008, Department of Energy, Politecnico di Milan , ITALY. [15] Abdulhamid El-sharif, Simulation Model of a Solar-Hydrogen Generation System, Newcastle University. [16]http://www.esru.strath.ac.uk/EandE/Web_sites/9900/hybrid_PV_FC/hy drogenstorage.html last access. [Access Date 12-8-2013 (12:30 PM)]. [17] Abou El-Maaty Metwally Metwally Aly Abd El-Aal, Modelling and Simulation of a Photovoltaic Fuel Cell Hybrid System, A Dissertation in for the Degree of Doctor in Engineering] the Faculty of Electrical Engineering, University of Kassel, GERMANY. [18] James Larminie, Andrew Dicks, Fuel Cell Systems Explained, 2003. [19] http://www.nasa.gov/centers/glenn/technology/fuel_cells.html, [Access Date 24-7-2013(1:37 PM)]. [20]International Summer school on PEM Fuel Cells Applications and] Integration,2011,Azmir,Turkey . [21] Yun Wanga, Ken S. Chenb, Jeffrey Mishlera, Sung Chan Choa, Xavier] Cordobes Adrohera, A review of polymer electrolyte membrane fuel cells: Technology, applications, and needs on fundamental research, a Renewable Energy Resources Lab (RERL) and National Fuel Cell Research] Center, Department of Mechanical and Aerospace Engineering, University of] California, Volume 88, Issue 4, April 2011, Pages 981–100, USA. http://www.esru.strath.ac.uk/EandE/Web_sites/9900/hybrid_PV_FC/hydrogenstorage.html%20last%20access.%20%20%5bAccess%20Date%2012-8-2013 http://www.esru.strath.ac.uk/EandE/Web_sites/9900/hybrid_PV_FC/hydrogenstorage.html%20last%20access.%20%20%5bAccess%20Date%2012-8-2013 http://www.nasa.gov/centers/glenn/technology/fuel_cells.html 70 [22] Build A solar Hydrogen Fuel Cell System, Phillip Hurley,2004, USA. [23] D.K. Ross, Hydrogen storage: The major technological barrier to the] development of hydrogen fuel cell cars ,University of Salford, Uk, Volume 80, Issue 10, 3 August 2006, Pages 1084–1089] [24] Jacques Rozière and Deborah J. Jones, non-fluorinated polymer matterials FOR pROTONeXCHANGE mEMBRANE fUEL cELLS Vol. 33: 503-555 (Volume publication date August 2003) Laboratoire des Agrégats Moléculaires et Matériaux Inorganiques, Université Montpellier II, France [25] Frano Barbir, PEM Fuel Cells. [26]¹ Tomáš Skočil, ² Manuel Pérez Donsión, Mathematical Modeling and] Simulation o Photovoltaic Array,¹ University of West Bohemia, Pilsen] , ² University of Vigo, Spain. [27] Mohammad Husain Mohammad Dradi, Design and Techno- Economical] Analysis of a Grid Connected with PV/ Wind Hybrid System in Palestine (Atouf Village-Case study). [28] S. Sheik Mohammed-a, Modeling and Simulation of Photovoltaic module using MATLAB/Simulink, International Journal of Chemical and Environmental Engineering October2011,Volume2, No.5, Salalah, Sultanate of Oman. [29] Jay Tawee Pukrushpan ,Modeling and Control of Fuel Cell Systems and Fuel Processors, A dissertation submitted in partial fulfillment of the requirements for the degree of the Doctor of Philosophy, 2003, University of Michigan. 71 [30] Andrea, E.; Ma ˜nana, M.; Ortiz, A.; Renedo, C.; Egu´ıluz, L.I.; P´ erez, S.; Delgado, F,A simplified electrical model of small PEM fuel cell , University of Cantabria, Cantabria, Spani . [31] http://www.sciencedirect.com/science/article/pii/S1364032109000872 [Access Date 12-9-2013 (1:30 PM)] . [32] http://tools.poweringhealth.org/[Access Date 12-6-2013 (12:30 PM)] [33]http://www.frankshospitalworkshop.com/equipment/documents/centrif uges/wi kipedia/centrifuge.pdf[Access Date 12-8-2013 (11:00 PM)] http://www.sciencedirect.com/science/article/pii/S1364032109000872 http://www.esru.strath.ac.uk/EandE/Web_sites/9900/hybrid_PV_FC/hydrogen%20%20%20%20%20%20%20%20storage.html%20last%20access.%20%20%5bAccess%20Date%2012-8-2013 http://tools.poweringhealth.org/ http://tools.poweringhealth.org/ http://www.frankshospitalworkshop.com/equipment/documents/centrifuges/wi%20kipedia/centrifuge.pdf http://www.frankshospitalworkshop.com/equipment/documents/centrifuges/wi%20kipedia/centrifuge.pdf http://www.esru.strath.ac.uk/EandE/Web_sites/9900/hybrid_PV_FC/hydrogen%20%20%20%20%20%20%20%20storage.html%20last%20access.%20%20%5bAccess%20Date%2012-8-2013 72 Appendixes 73 Appendix (A) Solar Cell and Hydrogen Fuel Cell Trainer 74 75 76 77 78 79 80 81 82 83 84 85 86 87 88 89 90 Appendix (B) PEM Fuel Cell Datasheet 91 H-300 H-SERIES PEM Fuel Cell SystemLeightweight, efficient, low cost, high power densities, semi-integrated 200W fuel cell system. Opening new possibilities for integration and innovative application development. Including: - Connections and tubing - Electronic valves - Electronic control box - 300W stack with blower - Fuel cell ON / OFF switch - SCU ON / OFF switch - Manual http://www.bredec.com/shop/distributed-energy/redev/pem-fuel-cell-stack/h-300-pem-fuel-cell.html http://www.bredec.com/shop/distributed-energy/redev/pem-fuel-cell-stack/h-300-pem-fuel-cell.html http://www.bredec.com/shop/distributed-energy/redev/pem-fuel-cell-stack/h-300-pem-fuel-cell.html http://www.bredec.com/shop/distributed-energy/redev/pem-fuel-cell-stack/h-300-pem-fuel-cell.html 92 Details H-300 Technical Specification Type of Fuel Cell....................... PEM Number of Cells......................... 72 Rated Power.............................. 300W Rated Performance.................... 43V @7.2A Output Voltage Range................ 39 - 69V Weight (with fan and casing)....... 2kg / 4.4lbs Size (mm / in.)......................... 104x280x90 / 4.1x11x3.5 Reactants................................. Hydrogen and Air Rated H2 Consumption.............. 4.2l/min 259in3/min 93 Hydrogen Pressure..................... 0.4 - 0.45Bar / 5.8 - 6.5PSI Purging Valve Voltage................. 12V Blower Voltage........................... 4 - 12V Controller weight........................ 362.4g / 0.8lbs Controller size (mm / inch)......... 88x133x40 / 3.5x5.28x1.6 Hydrogen supply valve voltage.... 12V Ambient Temperature................. 5 - 35°C / 41 - 95°F Max. Stack Temperature............. 65°C / 149°F Hydrogen Purity......................... 99.999% dry H2 Humidification........................... Self-Humidified CoolingAir................................. Air (integrated cooling fan) Start up Time............................ <30s @ 20°C / 60°F System Efficiency....................... 40% @ 43V Additional Information Weight 2.0 http://www.bredec.com/shop/customer-service/ 94 Appendix (C) Solar Radiation and Load 95 Time Load Power(W) Solar Rad. (kW/m 2 ) 5:00 50 0 6:00 50 0.012 7:00 50 0.10225 8:00 450 0.1405 9:00 670 0.416 10:00 660 0.667 11:00 650 0.853 12:00 660 0.983 13:00 650 0.98 14:00 660 0.9245 15:00 650 0.819 16:00 650 0.628 17:00 650 0.456 18:00 550 0.238 19:00 200 0.0037 20:00 200 0 21:00 200 0 22:00 200 0 23:00 50 0 0:00 50 0 1:00 50 0 2:00 50 0 3:00 50 0 4:00 50 0 5:00 50 0 96 Appendix (D) Experiments of PEMFC 97 0 0.2 0.4 0.6 0.8 1 0 200 400 600 800 Experiment of PEMFC characterictics Experiment of PEMFC characterictics Experment 2 0 50 100 150 200 250 300 0 100 200 300 400 500 600 700 800 Power of PEMFC at diffrent loads 98 Varied step load profile response of fuel cell 99 Appendix (E) PV module and PEMFC Stack Datasheet جامعة النجاح الوطنية كمية الدراسات العميا تزويد العيادات الصحية في المناطق النائية بالكهرباء باستعمال أنظمة الخاليا الشمسية وخاليا الوقود العاممة بالهيدروجين إعداد مكاوي دياب مكاوي حريز إشراف أ.د مروان محمود قدمت هذه األطروحة استكماال لمتطمبات الحصول عمى درجة الماجستير في هندسة الطاقة ستراتيجية الترشيد بكمية الدراسات العميا في جامعة النجاح الوطنية نابمس فمسطين. النظيفة وا 3102 ب المناطق النائية بالكهرباء باستعمال أنظمة الخاليا الشمسية وخاليا تزويد العيادات الصحية في الوقود العاممة بالهيدروجين إعداد مكاوي دياب مكاوي حريز إشراف أ.د مروان محمود الممخص العيادات الصحة الفمسطينية في المناطق النائية تعاني في الغالب من عدم وجود الشبكات الكهربائية بسبب القيود اإلسرائيمية وعدم توفرالبنية التحتية من السمطات المحمية. معظم هذه الرئيسية ، مما يجعل ربطها مع شبكات الطاقةالمناطق هي بعيدة عن خطوط نقل الجهد المتوسط الكهربائية الرئيسية غير عممي. ولذلك، يمكن لمصادر الطاقة المتجددة وخاصة الطاقة الشمسية وخاليا الوقود تمثل حموال أكثر نظيفة وموثوقة و مجدية . ويتضح نمط استهالك الطاقة نموذجية من عيادة صحية مقترح. وتعرض النتائج التجريبية التي تمت لمنظام الذي بني في المختبر إلعطاء نظرة ثاقبة عمى التفاصيل الفنية نظام . عطاء التفاعالت الكيميائية التي نتاج الطاقة النظيفة عن طريق خاليا الوقود ، وا توفر الوقود وا تحدث في داخل الخمية وكذلك إنتاج الكهرباء لمدة غير محدودة ، هي من المواضيع الرئيسية الشمسية لمنظام في هذه األطروحة . تقدم األطروحة أيضا استراتيجية إلدارة الطاقة لنظام الخاليا والوقود لتغطية الطمب عمى الطاقة الكهربائية من عيادة صغيرة نموذجية في المناطق الريفية في فمسطين . وتستند استراتيجية الرقابة المقترحة عمى الطريقة المستندة إلى المنطق الذي يعتبر مركز و إعطاء األولوية مصادر إمدادات الطاقة والحمل يتطمب الجمع بينها والتبديل في ما بينها لممصدر أكثر استقرارا .وأخيرا ، تمت دراسة النظام من حيث المقارنة المالية بين استخدام الوقود لتزويد العيادات الريفية بالكهرباء في هذه األطروحة . وقد وجد أن بطاريات و خاليا استخدام خاليا الوقود هو أكثر جدوى اقتصاديا.