Felipe Rosa

Design, Planning and Management of a Hydrogen-Based Microgrid

Efficient energy generation and consumption is a key factor to achieve ambitious goals related to air pollution and climate change. Modern electricity networks can include different kind of sources, such as renewable energy sources (RES). Then, hybrid systems are obtained by combining several sources and storage types in the new concept called microgrid (MG). In order to draw the best performance from these hybrid systems, a proper design and operation is essential. The purpose of this paper is to present a detailed report to properly undertake the building and management of a hydrogen MG in a simple and reliable way to continue struggling for more comprehension on the MG operation modes and prevent the reported failures in the literature. The experimental platform developed will provide the valuable knowledge and solid guidelines for future test centers and demonstration plants. The MG, located in Seville, Spain, incorporates an electrolyzer, metal hydride storage, fuel cell, and a battery bank as main components. The developed MG laboratory has been successfully tested. The results indicate reliable operation incorporating the hydrogen and batteries as energy storage.

Power management using model predictive control in a hydrogen-based microgrid

Due to the intermittent feature of renewable energies, microgrids usually require additional energy sources to operate when the stored energy or the renewable energy supply is scarce or are not present. Then, hybrid systems obtained by combining several sources and means of storage can be used. In order to draw the best performance of such systems, a proper energy management is essential. A key factor is to try to adapt the energy production to the demand, where Model Predictive Control (MPC) and supervision techniques can play an important role. The problem is more interesting when several possibilities for using the produced energy exist, and it is necessary to select how the energy is distributed among subsystems. Hence different objectives can arise (minimizing the use of conventional energy sources, energy saving, economic and quality aspects...). In this paper a supervisory MPC for optimal power management and control in a hydrogen-based Micro-Grid (MG) is designed. The system operation under appropriate constraints is also taken into account in the problem formulation. Simulations are carried out over experimentally validated models to demonstrate the goodness of the controller.

Solar hydrogen production: A spanish experience

Abstract In the framework of the solar energy activities carried out by INTAs Energy Laboratory, in 1990 a programme on solar hydrogen production and utilization was started. Within the general agreement between INTA and the regional government of Andalucia, a test and research plant for solar hydrogen production via water electrolysis was designed and erected in Huelva. The construction of the plant started in November 1991 and was finished in February 1992. The main objective of this facility is to test and evaluate the different technologies associated with solar hydrogen production, as well to stimulate research and development in this field in Spain. The plant is composed mainly of a 8.5 kW photovoltaic field with a flexible configuration of output voltage and current, and a 5.2 kW alkaline electrolyser. A test bench for PV module characterization, a conventional a.c./d.c. converter for electrolyser characterization and a d.c./d.c. maximum power point tracker as power matching system complete the test facility. The paper contains a technical description of the installation, the test plan to be performed, results concerning electrolyser characterization and some preliminary results of continuous operation.

CESA-1 thermal storage system evaluation

Abstract An evaluation follows of the CESA-1 solar thermal storage based on an eutectic mixture of 53% KNO3, 39% NaNO2, and 8% NaNO3 molten salt, existing on the Plataforma Solar de Almeria. Main parameters of the charge/discharge cycles (inlet/outlet temperatures, mass flows, and charge/discharge rates) were varied to simulate different solar multiples. The net thermal-to-thermal efficiency of this system was determined to be 72%, once the energy requirements to drive it are discounted. Thermal loss coefficients of both tanks were measured and found to be 0.327 and 0.265 W/m2 K for the hot and cold tank, respectively.

A comparison between conventional recuperative gas turbine and hybrid solid oxide fuel cell—gas turbine systems with direct/indirect integration

Abstract Conventional recuperative micro gas turbines have a 30 per cent low heating value (LHV) maximum efficiency at full load. Therefore, if they are to be used in a potential distributed energy scenario, solutions must be developed that increase efficiency. An innovative gas turbine-based technology is the fuel cell — gas turbine hybrid system. This work is aimed at studying how the basic performance of a conventional Brayton cycle changes when heat addition is done at a fuel cell. Two layouts are considered: a direct system where the compressor feeds the fuel cell directly and an indirect system where only heat is transferred between subsystems. Direct and indirect systems have been studied at full and part load, concluding that the efficiency versus pressure ratio curves of hybrid systems change substantially with respect to a traditional gas turbine; part-load efficiency hardly decreases. Maximum efficiency of hybrid systems doubles the efficiency of state of the art micro gas turbine and remains high at part load. Furthermore, the benefit of a certain increase in temperature is higher for hybrid systems than for conventional engines. Finally, a simple economic analysis shows that the total installation and operation/maintenance costs of hybrid systems make them competitive against conventional gas turbines.

CESA-1 project capabilities for high temperature material testing: Application to the HERMES wing leading edge tests

Abstract This is a report on the activities carried out at the CESA-1 Facility of the Plataforma Solar de Almeria within the framework of the HERMES Wing Leading Edge (W.L.E.) tests. It includes a description of the solar furnace, test procedure, instrumentation and test results, proving the capabilities of this facility in the field of high temperature material testing. It is not intended to compare the thermomechanical behavior of the materials tested. These tests to determine the thermomechanical behavior of two W.L.E.s (CC and CSiC) under simulated thermomechanical reentry conditions of the space vehicle HERMES, can be summarized as the performance of 1550° and 1730°C thermal cycles maintaining stationary conditions during 20 minutes. During this time a certain vertical temperature profile had to be reached on the W.L.E. and a set of mechanical tests (tension and compression) were carried out. Results demonstrate the flexibility of CESA-1 heliostat field control in tests of this nature. All heating and cooling rates, stationary conditions and temperature profile constraints imposed by the European Space Agency (E.S.A.) were satisfied successfully. The safety of the material was guaranteed and, finally, taking into account that we were using 55% of the total power of the heliostat field, material testing at even higher temperatures would seem to be possible.

Practical implementation of an hybrid electric-fuel cell vehicle

Electric vehicles are currently the focus of the researchers all over the world. High harmful gas emissions from conventional vehicles and the rising of new clean and competitive energy sources have leaded to an increasing interest of vehicle providers and consumers. In this paper, a practical example of an hybrid vehicle is addressed. The hybrid vehicle is driven by an array of batteries and a 5 kW fuel cell. The changes done in the vehicle chassis, the necessary power electronic converter and the control and monitoring systems are explained in this paper. Some experimental results are shown in order to show the vehicle performance. The vehicle range has been approximately doubled using the hybrid electric- fuel cell system. The proposed hybrid vehicle, tested under real weather conditions, has demonstrated a high robustness and reliability.

Fluid Flow in Polymer Electrolyte Membrane Fuel Cells

Polymer Electrolyte Membrane Fuel Cells (PEMFC) have attracted significant interest during the last few decades, as they are considered to be one of the most promising alternative clean power generation devices for portable, mobile and stationary applications. However, different technological barriers such as cost, durability, or heat and water management, are limiting the implementation of fuel cell systems into the global energy markets, and therefore significant research efforts and investments are being carried out. Fuel cells are devices where electrochemical reactions transform chemical energy available in fuels into electrical energy. Fuel cells are not limited by the thermodynamic restrictions of conventional power generation systems, such as the Carnot efficiency, meaning that fuel cells can be operated with higher efficiency for energy conversion. Additionally, the environmental impact is low as no combustion processes occurs and no pollutants are generated (U.S. Department of Energy [DOE], 2004). A typical fuel cell power system consists of different components: Single cells, where the electrochemical reactions occur. Stacks, consisting of the necessary number of cells electrically connected to provide the required power capacity. The balance of plant, or additional equipment to provide fuel and oxidants with the appropriate conditions, thermal management, electric power conditioning, and other functions. Single or unit cells are the core of a fuel cell. They convert the chemical energy contained in a fuel into electrical energy, via electrochemical reactions. The basic configuration of a fuel cell consists of an electrolyte layer or membrane in contact with an anode and a cathode on either side. In a PEM fuel cell, hydrogen is continuously supplied to the anode or negative electrode, and an oxidant, often oxygen or air, is also continuously supplied to the cathode or positive electrode. Electrochemical reactions occur at the electrodes, generating an electric current through the electrolyte thus driving the corresponding electric current that performs the electric work on the load. At the anode, hydrogen is fed to the cell and a reaction takes place at the catalyst layer: