Adaptive Load Sharing Strategy for Multi-Source Renewable Energy Systems

Modeling, control and simulation of a PV/FC/UC based hybrid power generation system for stand-alone applications

This research examines the integration of solar pv & wind turbines for hydrogen production and generate electricity directly or reconvert hydrogen to electricity through fuel cells. Electricity generated from sunlight and wind is promising for hydrogen production using water electrolyzer. The growth of energy system with the use of fuel cell technology requires basic understanding of fuel cell system as well as related power electronics. This research provides an overall system model including solar pv, wind turbine, electrolyzer, storage system, fuel cell systems, and grid integration model using MATLAB Simulink. Particular attention is paid to design energy mix from renewable energy. The power electronics system makes the electrical output synchronized with the existing power grid and load. In selecting DC-DC and DC-AC power converters, studies to the unique specifications have been carried out for system design purposes. The fuel cell output to the DC link can be transferred to loads with the converter and then to the grid using the three-phase ac grid-inverter. The system from the research can be developed with a combination of solar pv & wind turbine power plant, hydrogen production plant, hydrogen storage system, fuel cell power generator, hydrogen-based fueling station, electric vehicle charging station, and grid integration. Thus, this system has several advantages. Besides producing electrical energy, it can also be used as a backup power with hydrogen storage-fuel cells system. The hydrogen produced can also be used for various needs such as in petrochemical plants, oil refineries, and other industries.

<div class="htmlview paragraph">XCELLSiS Corporation is a Fuel Cell System Engineering and Integration company working in an Alliance with Ford Motor Company, DaimlerChrysler, Ballard Power Systems, and ECOSTAR. The goal of the Alliance is to successfully commercialize Fuel Cell propulsion systems in the automaker partner's vehicles. XCELLSiS is the Tier 1 Fuel Cell System supplier and system integrator with the Fuel Cell stack being supplied by Ballard. The power developed by the XCELLSiS system is transferred to the ECOSTAR drive motor completing the vehicle propulsion system.</div> <div class="htmlview paragraph">Fuel Cell powered vehicles have been produced by both automaker partners, Ford and DaimlerChrysler, and introduced to the public in conjunction with the Fuel Cell Alliance and the California Fuel Cell Partnership. The vehicles are code named Ford Focus Fuel Cell Vehicle and the DC Necar 4A. Through these vehicle experiences and developments, XCELLSiS and its partners have amassed knowledge of the operation of Fuel Cell Systems in fully functional, light duty vehicle environments to further augment heavy duty applications. Information from these experiences of Fuel Cells providing the primary source of propulsion in an automobile environment will contribute to the Alliance product development processes.</div> <div class="htmlview paragraph">This paper will look through the XCELLSiS Fuel Cell System development experience as it applies to the most recent vehicles. It will also discuss peripherally the vehicle interaction along with Fuel Cell System effects, which arose during the development of the Fuel Cell System.</div> <div class="htmlview paragraph">The paper will illustrate that vehicle experiences are technically challenging and many, however, not insurmountable. It will also support the automotive industry's high confidence regarding the future of Fuel Cells as a viable power source for light and heavy duty vehicle propulsion</div>

In this paper, a systematic analysis of seven control topologies is performed, based on three possible control variables of the power generated by the Fuel Cell (FC) system: the reference input of the controller for the FC boost converter, and the two reference inputs used by the air regulator and the fuel regulator. The FC system will generate power based on the Required-Power-Following (RPF) control mode in order to ensure the load demand, operating as the main energy source in an FC hybrid power system. The FC system will operate as a backup energy source in an FC renewable Hybrid Power System (by ensuring the lack of power on the DC bus, which is given by the load power minus the renewable power). Thus, power requested from the batteries’ stack will be almost zero during operation of the FC hybrid power system based on RPF-control mode. If the FC hybrid power system operates with a variable load demand, then the lack or excess of power on the DC bus will be dynamically ensured by the hybrid battery/ultracapacitor energy storage system for a safe transition of the FC system under the RPF-control mode. The RPF-control mode will ensure a fair comparison of the seven control topologies based on the same optimization function to improve the fuel savings. The main objective of this paper is to compare the fuel economy obtained by using each strategy under different load cycles in order to identify which is the best strategy operating across entire loading or the best switching strategy using two strategies: one strategy for high load and the other on the rest of the load range. Based on the preliminary results, the fuel consumption using these best strategies can be reduced by more than 15%, compared to commercial strategies.

Recently, photovoltaic (PV) system has attracted attention because of serious environmental and energy problems. However, if PV systems are intensively connected to the grid in a specific area, it is predicted that the voltage of the distribution feeder in power system increases due to the reversal power flow. Such degradation of electric power quality leads to the depression of PV output by power conditioners. In our previous research, we have overcome the problem by introducing the storage batteries and optimally charging and discharging them [1][2]. On the other hand, the residential fuel cell (FC) system has been a focus of attention because FC has achieved a primary energy efficiency of 80% by making the best use of generator waste heat. When the FC system is operated according to the residential thermal demand as a general operation, its electric output doesn't always follow the residential electric load. Therefore, it is also indispensable to introduce the storage battery to the hybrid system with a combination of PV subject to weather condition and FC giving the priority to heat supply. In this paper, we investigate the optimal operation of the storage battery for the hybrid PV and FC system.

Hydrogen/oxygen fuel cells were successfully utilized in the field of space applications to provide electric energy and potable water in human-rated space mission since the 1960s. Proton exchange membrane (PEM) based fuel cells, which provide high power/energy densities, were reconsidered as a promising space power equipment for future space exploration. PEM-based water electrolyzers were employed to provide life support for crews or as major components of regenerative fuel cells for energy storage. Gas/water and heat are some of the key challenges in PEM-based fuel cells and electrolytic cells, especially when applied to space scenarios. In the past decades, efforts related to gas/water and thermal control have been reported to effectively improve cell performance, stability lifespan, and reduce mass, volume and costs of those space cell systems. This study aimed to present a primary review of research on gas/water and waste thermal management for PEM-based electrochemical cell systems applied to future space explorations. In the fuel cell system, technologies related to reactant supplement, gas humidification, water removal and active/passive water separation were summarized in detail. Experimental studies were discussed to provide a direct understanding of the effect of the gas-liquid two-phase flow on product removal and mass transfer for PEM-based fuel cell operating in a short-term microgravity environment. In the electrolyzer system, several active and static passive phaseseparation methods based on diverse water supplement approaches were discussed. A summary of two advanced passive thermal management approaches, which are available for various sizes of space cell stacks, was specifically provided

In this paper, a DC-coupled photovoltaic (PV), fuel cell (FC) and ultracapacitor hybrid power system is studied for building microgrid. In this proposed system, the PV system provides electric energy to the electrolyzer to produce hydrogen for future use and transfer to the load side, if possible. Whenever the PV system cannot completely meet load demands, the FC system provides power to meet the remaining load. The main weak point of the FC system is slow dynamics, because the power slope is limited to prevent fuel starvation problems, improve performance and increase lifetime. A power management and control algorithm is proposed for the hybrid power system by taking into account the characteristics of each power source. The main works of this paper are hybridization of alternate energy sources with FC systems using long and short storage strategies to build an autonomous system with pragmatic design, and a dynamic model proposed for a PV/FC/UC bank hybrid power generation system. A simulation model for the hybrid power system has been developed using Matlab/Simulink, SimPowerSystems and Matlab/Stateflow. The system performance under the different scenarios has been verified by carrying out simulation studies using a practical load demand profile, hybrid power management and control, and real weather data.

A novel anti islanding detection method for grid connected fuel cell power generation systems

In this paper, a multi-agent control system for DC-coupled photovoltaic (PV), fuel cell (FC), ultracapacitor(UC) and battery hybrid power system is studied for commercial buildings & apartment buildings microgrid. In this proposed system, the PV system provides electric energy to the electrolyzer to produce hydrogen for future use and transfer to the load side, if possible. Whenever the PV system cannot completely meet load demands, the FC system provides power to meet the remaining load. A multi-agent system based-power management and control algorithm is proposed for the hybrid power system by taking into account the characteristics of each power source. The main works of this paper are hybridization of alternate energy sources with FC systems using long and short storage strategies to build the multi-agent control system with pragmatic design, and a dynamic model proposed for a PV/FC/UC/battery bank hybrid power generation system. A dynamic simulation model for the hybrid power system has been developed using Matlab/Simulink, SimPowerSystems and Stateflow. Simulation results are also presented to demonstrate the effectiveness of the proposed multi-agent control and management system for building microgrid.

An attractive application of electrochemical impedance spectroscopy (EIS) is for diagnostic of a fuel cell (FC) or a battery system during operation. The use of EIS, however, is mostly limited to low-voltage (LV) FC systems and laboratory environments. Hence, the application of EIS in advanced diagnostics of a high-power system certainly lacks due to the voltage limitation and/or cost of the equipment. In this paper, a precision, low-cost electronic interface is proposed which enables the use of existing LV ac diagnostic tools with a production-size FC or battery stacks without the need for postprocessing of data. The interface, a dc level reducer (DLR), reduces only the dc component of the stack voltage to a safe voltage of <60 without altering the ac diagnostic components. This paper explains in detail the development of the DLR circuitry. The scalability and real-world capability of the interface are demonstrated by developing it for two voltage ratings. A set of circuits rated for 30 V is tested with a nine-cell proton exchange membrane FC (PEMFC) stack, and circuits rated for 200 V are tested on 90- and 110-cell commercial PEMFC stacks. The stack voltage is reduced by 60% on the nine-cell stack, and 60%–90% on the 90- and 110-cell stacks. The accuracy is measured using EIS data for 74 frequency points in the range of 0.1–20 kHz, with and without the DLR. The maximum relative error for point-versus-point comparison of the impedance is measured at 0.8% and 1.4% for 30- and 200-V rated circuits, respectively. These errors are well within the error of the industrial measurement equipment used, proving the fidelity of the ac signal output from the DLR.

JAMSTEC (Japan Agency for Marine-Earth Science and Technology) and MHI (Mitsubishi Heavy Industries, Ltd.) have been developing the AUV (Autonomous Underwater Vehicle) Urashima since 1998. Long-distance cruising AUVs generally need an AIP (Air Independent Propulsion) power source characterized by high-energy density and high-energy efficiency. Fuel cells are the preferred AIP power source for small underwater vehicles and PEFC (Polymer Electrolyte Fuel Cell) have been adopted for Urashima. It is understood that one of the main themes with fuel cell is storing the hydrogen, the metal hydride storage has been adopted for Urashima as a safer method of storing the hydrogen. In summer of 2002 the AUV Urashima successfully completed an autonomous 132.5 km long-distance cruise using large capacity lithium-ion rechargeable battery. In the meantime, a Closed Cycle PEFC (Polymer Electrolyte Fuel Cell) system with a metal hydride hydrogen storage system was developed as an alternative AIP power source in order to extend Urashima's cruising range. The lithium-ion rechargeable battery was replaced by the Closed Cycle PEFC system and this system became the main power source of Urashima in winter of 2002. Urashima, with its new power source (the Closed Cycle PEFC system) achieved the world's first and deepest fuel cell power source dive in summer of 2003 and completed an autonomous cruise of 220 km in spring of 2004. In sea trials, the fuel cell system with metal hydride hydrogen storage system worked adequately and underwater fuel cell operation was verified. There were no problem in supplying power to the vehicle and supplying hydrogen to fuel cell system. Urashima will carry out the AUV world record 300 km cruising at upcoming trial opportunity.

A Deep Sea Cruising AUV “URASHIMA” has been developed by JAMSTEC since 1998. The dimensions and weight are 10m (L), 1.3m (W), 1.5m (H), and about 7.5 tons in air. A main power source device system of AUV “URASHIMA” is a large capacity of lithium-ion (Li-ion) rechargeable battery system or Solid Polymer Electrolyte Fuel Cell (PEFC) system. AUV “URASHIMA” will be able to cruise for about 100km with Li-ion battery system and it will cruise for about 300km with fuel cell system. The cruising trial used by the fuel cell system will start at the end of 2002. The instruments for science researches are an automatic multi-water-sampling system, a CTDO, a side-scan sonar, a digital still camera with a thermoelectrically cooled CCD image sensor, a TV camera, and so on. Three operation modes, which are UROV mode, acoustic remote control mode and autonomous mode, are available. Those three kinds of modes are used acceding to each development stage and ocean researches. UROV mode is to monitor the state of the vehicle with fiber optics. At the first development stage of AUV “URASHIMA”, we carried out long cruising trial for about 100km and maximum operational depth trial at 3,500m used by Li-ion rechargeable battery system. URASHIMA was succeeded to reach at 3,518m depth of the seafloor at the sea trial of August 2001. We also carried out long cruising trial that was controlled by autonomous mode. Then, URASHIMA was cruised 70km distance at the sea trial of December 2001. We will have a next sea trail on May 2002 for 100km long cruising test. At the next development stage, we will carried out long cruising trial for 300km used by the fuel cell system.

Balance-of-Plant (BOP) cost for PEM fuel cell systems are now equal to or exceeding the cost of PEM fuel cell stack. The fuel cell systems cost analyses funded by the Fuel Cell Technologies Office (FCTO) of the U.S. Department of Energy (DOE) confirms the near equivalency of the BOP cost to fuel cell stack cost for PEM fuel cells in the studies by Battelle[1], Lawrence Berkeley National Laboratory[2], and Strategic Analysis Inc.[3]. The cost equivalency between the BOP and the PEM fuel cell stack is observed over the full spectrum of fuel cell applications; Material Handling Equipment (MHE) fuel cell systems, stationary fuel cell systems, automotive fuel cell systems. James et al[4]evaluated PEM automotive fuel cell costs and found that at production rates of 30,000 automotive units per year or greater the BOP cost were more than the PEM fuel cell stack cost, as shown in Figure 1.Battelle[5] reports the BOP cost is 3.5X the cost of the fuel cell stack in their analysis of the cost of a PEM 10 kW fuel cells for MHE; these data are represented in Figure 2 where the balance of plant is 59% of the fuel cell system cost at production rates of 10,000 MHE fuel cell systems per year.For a PEM 100 kW hydrogen fueled stationary fuel cell systems, Wei and McKone[6]of Lawrence Berkeley National Laboratory (LBNL) reported the ratio of BOP-to-stack cost is 1.3 at production rates of 1,000 hydrogen fueled units per year. For a PEM 100 kW reformate fueled stationary power plants, the LBNL data demonstrate the ratio of BOP to fuel cell stack cost is 1.1 for a production rate of 10,000 fuel cell systems per year.LBNL evaluated smaller hydrogen fueled PEM stationary, backup power (BUP) systems and the ratio of BOP to fuel cell stack cost was 1.5 for a 10 kW system. At BUP system production levels of 50,000, the ratio of BOP-to-fuel cell stack cost increased to 2.3 in the LBNL data.A three part approach to improving BOP performance, durability and reduced cost is:Increasing awareness of BOP specifications for performance, durability and cost within the supply chain.Optimization of manufacturing processes to reduce cost of BOP componentsDevelopment of fuel cell system BOP components that meet original equipment manufacturers specifications. Increasing awareness of BOP specifications: For many years, the approach to fuel cell BOP components has been to use Off The Shelf (OTS) components developed for non-fuel cell applications. Overall, this approach has not been successful because of a lack of awareness of the OEM specifications by the BOP manufacturers. The Ohio Fuel Cell Coalition brought the OEMs and BOP manufacturers together to share specifications, discuss manufacturing capabilities, and establish acceptable cost targets. The results of these exchanges will be presented.Optimization of Manufacturing Processes for BOP Components: The FCTO has sponsored manufacturing R&D programs for the last three years. Manufacturing R&D for BOP components will be discussed and recommendations for optimization of manufacturing methods for specific BOP components presented.Development of Fuel Cell Balance-of-Plant Components: Replacement of OTS components that are mismatch for fuel cell applications will in many cases require alternative materials and specialized designs to meet the OEM durability and performance requirements. The R&D pathways to identify alternative materials and specialized designs will be discussed.

Hydrogen fuel cells are an attractive technology to power zero-emissions heavy-duty vehicles, including road vehicles, such as trucks and buses, as well as marine, rail, and mining applications. Hydrogen fuel cell powertrains can offer several advantages over incumbent technologies, such as diesel engines, including higher efficiency, reduced emissions, higher torque, and no noise pollution. Additionally, they offer fast fueling and adequate fuel storage for applications demanding longer range. In comparison to light duty fuel cell vehicles, which have begun early commercialization, fuel cell systems for heavy duty applications have important differences in their requirements and typical operation. Heavy duty fuel cell systems must offer high durability and efficiency to provide a competitive total cost of ownership considering capital costs, fuel costs, and lifetime. Furthermore, load-hauling applications, such as trucks, rail locomotives, and mining vehicles, must provide higher average and peak power while meeting heat rejection and onboard packaging constraints.Efforts to develop effective fuel cell materials, components, stacks, and systems for heavy duty applications must be guided by new targets and testing protocols. Fuel cell system modeling is essential to determine how application requirements translate to specific demands for the fuel cell system and components.The Department of Energy has set system-level targets for long-haul class 8 fuel cell trucks at 25,000 hour lifetime, 68% peak efficiency, and $80/kWnet fuel cell system cost by 2030 and ultimate targets of 30,000 hour lifetime, 72% peak efficiency, and $60/kWnet fuel cell system cost.[1] This presentation will discuss the system-level targets as well as the development of new targets and testing protocols for heavy duty fuel cell components and materials. This includes specific performance tests for different operational requirements, accelerated stress tests, and targets combining durability, performance, efficiency, and cost. We will also discuss differing needs between heavy duty applications, each of which presents unique requirements for fuel cell systems. It is desirable to address these unique requirements with standardized, cross-platform fuel cell stacks and components to enable high volume, low cost manufacturing, which requires the development of suitable cross-platform targets. [1] U.S. Department of Energy. “Hydrogen Class 8 Long Haul Truck Targets”. DOE Hydrogen and Fuel Cell Technologies Program Record. December 12, 2019: https://www.hydrogen.energy.gov/pdfs/19006_hydrogen_class8_long_haul_truck_targets.pdf

The harmful influences of the fossil fuels on the environments have convinced the authorities to set official targets to 100% phase out the sales or registrations of new internal combustion engines (ICEs). As alternatives, batteries and fuel cells are suggested to provide the required power for different applications such as cars, buses, trucks, etc. Although there have been many investigations on the possibility of using integrated fuel cell and battery system as the prime mover for different types of vehicles, limited number of investigations have been developed in the airplane sector.At the current stage, the current suggested integrated system of battery and fuel cell is not able to provide the required power for huge passenger planes, but they can generate the needed electricity to run small size planes (around 100kW to 300 kW), hence the objective of the current study is related to the domain of Unmanned Aerial Vehicles (UAVs). UAVs are designed to fulfill long and high-altitude flight missions. The flight duration and flight altitude have been proved to be improved using the proton exchange membrane fuel cells (PEMFCs) as the prime-mover of the UAVs. However, the low acceleration of the PEMFCs has triggered the idea of combining PEMFCs and Lithium-Ion (Li-ion) battery. Thus, the integrated system can improve the low range of batteries by maintaining high acceleration and fast re-fueling time.Among different types of fuel cells, PEMFCs are established to be the best option for mobility applications, and the well-known Nickel Manganese Cobalt (NMC), and Lithium Titanite Oxide (LTO) Li-Ion batteries are considered as the most efficient types. Among the existing Li-Ion batteries in the market, LTO enjoys from the highest performance, lifespan, and safety by higher costs, whereas NMC provides acceptable performance with low costs and high specific energy. In comparison to the batteries, proton exchange membrane fuel cells (PEMFCs) have faster refueling time and higher ranges, hence the integration of batteries and fuel cells can provide the needs of UAVs.The utilization of PEMFC in an UAV results in the size and weight reduction of the system in addition to improving the flight endurance. Batteries can also ameliorate the acceleration and thrust of the system. So far, it is believed that fuel cells can be suitable for cruise flight while batteries are more appropriate for other flight modes. This study analyzes the possibility of integrating the PEMFC technology to the batteries as an alternative for fossil fuel-based combustion engines for the small sized UAV application. The proposed hybrid system, which is shown in Fig. 1., is designed to provide around 950W power for a UAV with a weight of 14 kg. PEMFC will be used as the selected type of fuel cell while NMC is the considered type of Li-Ion battery. The goal of this study is the characterize the dynamic performance of the current integrated system in an optimized condition. The integrated model of the fuel cell and battery is developed in the MATLAB/Simulink software to be controlled by an energy management system, which provides power to a DC variable power load, representing the different loads of an UAV flight. The load is mainly supplied by the fuel cell, while the battery intervenes in the following cases: As a support when the load is too high for the fuel cell,As a support when the fuel cell takes too long to respond to a load variation,As an additional load when the state of the charge of the battery is low (meaning that the fuel cell recharges the battery). Figure 1