A 5kW ELECTROLYSER/FUEL CELL SYSTEM WITH HYDROGEN ACCUMULATION COMBINED WITH A WIND GENERATOR COUPLED TO THE ELECTRIC GRID

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1 A 5kW ELECTROLYSER/FUEL CELL SYSTEM WITH HYDROGEN ACCUMULATION COMBINED WITH A WIND GENERATOR COUPLED TO THE ELECTRIC GRID Cristina Parrado a, Daniel Sopeña b, Andres Melgar b, Santiago Rodrigüez b a Construcciones y Obras Llorente S.A, C/ Aluminio 17, Valladolid Spain Telf: Fax: cristinap@collosa.es b Fundación Cidaut, Parcela Boecillo Valladolid Spain, Telf: Fax: dansop@cidaut.es, andmel@cidaut.es, sanrod@cidaut.es ABSTRACT: This communication presents the description of a pilot plant consisting of hydrogen production by means of an electrolyser run with wind energy, a power converter to get the maximum power for different wind speed conditions and a hydrogen storage system. This hydrogen is fed into a PEM fuel cell in order to obtain, after inverting, AC current under the conditions required by the electric grid. Results of the behavior of the electrolyser for different current conditions and the results obtained from the weather station data are shown. It also includes conclusions and further jobs. KEYWORDS : PEMFC, ELECTROLYSER, WIND ENERGY. INTRODUCTION Nowadays, wind energy is one of the most economical energy sources with a well-known technology. Nevertheless, the instability caused by the wind turbines to the grid and the unpredictable generated power due to the meteorology, make necessary to develop energy storage systems for this wind energy. These systems will allow supplying this energy into the grid with the required characteristics in periods of a higher demand. Hydrogen as an energy vector, together with electrolyser and fuel cell technologies can provide a technical solution to this challenge. The aim of the project is the development of practical knowledge that enables to defer in time the production and supply of electrical energy provided by the wind through the use of an energetic storage system based on hydrogen. The stored energy will be overturned to the grid in the peak periods of the electrical demand curve. A pilot plant of 5 kw electric power is being developed. The pilot plant consists of hydrogen production by means of an electrolyser run with wind, electricity and a hydrogen storage system. This hydrogen is fed into a PEM fuel cell in order to obtain, after inverting, AC current under the conditions required by the electric grid and when the demand is higher. The main investigation lines covered with this project can be blocked in three groups. Design and construction of a 5 kw pilot plant to produce electric energy. This plant integer a production and storage hydrogen system obtained from wind energy through a power converter system developed by Collosa y Cidaut, with a PEM fuel cell, and a DC/AC converter. The fuel cell was tested in a previous project where the hydrogen was obtained with a natural gas fuel processor. Definition and implementation of a control system that provides all the necessary processes control and monitoring functions to achieve reliable, safe and efficient operation. Definition of exportation approaches and better design of the plant. This phase contemplates different technical approaches for applying the results obtained from the project in different scopes: industrial scope in high power wind farms and also in the residential sector for small power. EXPERIMENTAL The developed system consists of six main modules: 1) a specific alkaline electrolyser for renewable sources with a production of 2 Nm 3 /h at an output pressure of 30 barg from Accagen, 2) Storage system with a total volume of 20 Nm 3 in compressed hydrogen bottles, 3) power generator to simulate the electrical energy 1/1

2 produced by a wind turbine of 20 KVA 4) a wind turbine that will be selected after the conclusions of the simulation 5) a 5 Kw Teledyne PEM Fuel Cell, 6) peripheral systems: power system that allows the adaptation of the given signal by the wind turbine at the input of the electrolyser with a MPPT (Maximun Power Point Tracking) function, humidity system for the fuel cell and the control system. The aspect of some of these components is presented in Figure 1 Figure 1. a) Electrolyser b) Power generator c) PEM Fuel Cell During this project an important research has been done not only related with manufacturers but also with the working and technical characteristics of the different equipments that are going to work together. In this phase one of the most important points has been the electrolyser acquisition. The decision has been made taking into account technical requirements, CE regulations and safety provisions. The power required by the electrolyser is provided to the process by a renewable source, whereas the power for auxiliary systems and control is provided by the net. The obtained unit include all the equipment for a safety and automatic hydrogen production. In particular this electrolyser is made it with special electrodes able to sustain the sudden and frequently repeated current interruption without the need of polarization maintaining current during the off state of the wind system. All the internal parts, in particular the electrodes, are made out of corrosion resistant materials, largely increasing the cell lifetime even when subject to very strong varying currents. On the other hand, the election has been linked with the election of the wind turbine. The main problem was that the offer for small wind turbines is very small. Not all the companies that offer these elements are ready to sell them because most of them are prototypes. This is one of the main problems to integrate the hydrogen production from wind energy in a small scale. The storage system is based in a well known and developed technology like the storage of compressed hydrogen in a stack of bottles. This systems has been bought to PRAXAIR SPAIN Figure 2. Hydrogen storage To characterize the developed power system we use an electric generator that simulates the signal generated by a wind turbine. Working on the power feed to the coil it can be obtained a constant voltage and acting over the generator accelerator is possible to simulate different wind conditions. 2/2

3 From this simulation it will be obtained power-speed curves for different wind speeds, so the AC/DC converter will try to get the maximum power for a wind speed condition, including the conditions related to voltage and current imposed by the electrolyser, as is shown in figure 3. Figure 3. Scheme of the system Figure 4. Basic converter scheme RESULTS In this section results obtained from different equipments working alone are presented. It has been carried out some test to determinate the behaviour of the electrolyser for different conditions as it is showed in the following figures. Figure 5. Electrolyser behaviour for sudden changes of current 3/3

4 Figure 6. Details of electrolyser behaviour for sudden changes of current Figure 5 shows the general behaviour in a long term test. Figure 6 shows the electrolyser behaviour when different current changes are applied (sudden changes from stationary conditions to reach different levels, also the system working at maximum power, and finally ramps cycles from Imin to Imax) keeping the temperature fixed at 80º C It has been necessary to study the wind potential in the zone and decide the best wind turbine according to the characteristics of the wind. Wind data were obtained by means of a weather station and used for the simulation process to establish the working parameters of the electrolyser These data have passed two processes: The first one for processing the obtained data. These data will be the base for the rest of the programs. The second one, numerical and visual conclusions are obtained, which allows to make a decision for selecting a wind turbine and its working conditions. With all this information we have made a study of the wind potential and a study of small market wind turbines too. Some of the visual conclusions are showed in figure 7 Figure 7. Different power curves calculated for different wind turbine models 4/4

5 In a previous project it has been carried out different test for characterising the fuel cell obtaining graphs voltage-current to check its proper working. Test using constant input flow rates and varying different parameters (inlet pressures, temperatures, ) were carried out. In figure 8 the test accomplished at different working temperatures of the fuel cell is shown. CONCLUSIONS Considering the mentioned above, conclusions about the compatibility of the different energy supply systems, the study of different wind conditions and the work with the adaptative electronics systems have allowed that the energy transferred from wind power into hydrogen will be maximum. But even some further jobs have to be done to obtain a good system overview. FURTHER JOBS Complete system integration Programming the control strategies that allow the interconnection between the different components. Carrying out all the integration and tests involving the system response to different working conditions, mainly related to wind conditions and energy requested, and their influence on the fuel cell. A study in which the technical aspects required for the exportation of the wind hydrogen generation systems to its implantation in high power wind farms will be presented. It will be also shown a performance study of the different components of the facility in different working conditions. 5/5