Methods to detect and mitigate catalyst support carbon corrosion in PEM fuel cells
Carbon black based electrodes are generally recognized as state of art for PEM fuel cell technology due to the high performance achieved with relatively low Pt content. However, the catalyst carbon support is prone to carbon oxidation. This leads to loss of catalyst area and overall performance, as well as higher mass transport loss due to an increased flooding tendency. This phenomenon is particularly severe when the fuel cell experiences repetitive start-stop cycles. Therefore, specific countermeasures against catalyst layer carbon oxidation are required, especially for automotive and backup power applications, where the startup/shutdown rate is considerably high. The authors evaluated a basic design that uses a stack shunt. A properly modified control protocol, which includes the stack shunt, is able to avoid high cathode potential peaks, which are known to accelerate catalyst carbon support corrosion and its negative effects. During two separate durability tests, one adopting the shunt design and another using non-protected shutdown, a 24-cell stack was subjected to continuous starts and stops for several months and its performance constantly monitored. Results show that when the shunt is used, there is a 37 percent reduction in the voltage degradation rate for each startup/shutdown cycle, and a two-fold increase in the number of startup/shutdown cycles before an individual cell reached the specified “End of Life” voltage criteria. Furthermore, ex-situ FE-SEM analysis revealed cathode catalyst layer thinning, an indication that the emerging degradation mechanism is the catalyst support carbon corrosion, as expected. This provides further support that the constant voltage degradation rate typically experienced in PEMFCs can be attributed primarily to the catalyst support carbon corrosion rate. The proposed shunt protocol is very cost-effective and does not require any substantial changes in the system. For this reasons, its adoption is recommended as a viable method to decrease the catalyst support carbon corrosion rate and extend the operating life of the PEMFC stack.
Design and development of a 7kW polymer electrolyte membrane fuel cell stack for UPS application
This work presents the PEMFC stack design methodology developed at CNR-ITAE, in the frame of a collaboration with an industrial partner, Electro Power Systems (EPS), operating in the Uninterruptable Power Supply (UPS) market. A detailed description of the design procedure of a 7 kW PEMFC stack is reported, starting from technical requirements of the UPS system to experimental tests. Bipolar plate layout, active area surface and shape, maximum (OCV) and minimum voltage, maximum cooling circuit pressure drop, maximum cathodic flow-field pressure drop, were the main constraint that influenced the constructive solutions. The electrochemical performances of Gore Primea 5621 MEA with SGL Sigracet GDL were chosen as reference to select the appropriate operating point in terms of current density and single cell voltage. A current density of 800 mA/cm2 was imposed as operating point of the stack, subsequently main stack parameters were calculated. Three different cathodic flow fields, that were designed to fulfill UPS system requirements, were tested in a single cell arrangement, to find the best gas flow path in terms of compromise between cell performance and pressure drop. Also a specific study was dedicated to the selection of gasket material to find the best compromise between cell performance and limited mechanical stress. The assembled 70 cells unit was tested in a test bench simulating the power system. Preliminary tests of the full unit yielded to a power of 6.2kW at 36 V.
GreenShelter for telecom applications. A new generation of shelters for telecom applications integrating fuel cell electric backup and a new cooling approach
A new generation of shelter for telecom application has been designed and manufactured. The basic approach was to overcome the limit of the current technology regarding cooling needs and energy consumption as well as maintenance costs and backup autonomy. In this perspective the following elements have been considered: to implement an active cooling with very low energy consumption or passive cooling, to backup the apparatus with fuel cell based power system, to integrate as much as possible both the technologies. Shelter cooling without air conditioning is possible with free-cooling and phase changing materials (PCM). Fuel cell based power systems give advantages in terms of wide range of accepted working temperature (from -5°C to 45 °C) and very low maintenance needs. The fuel cell based power systems have been tested by several different Telecom operators but up to now very small activities have been performed for a complete integration into the shelter. In this application a 3 kW power system provides 24 hours of autonomy to all the equipments installed in the shelter. To accomplish to a complete integration work a new generation of power system has been generated: the new release consist in a 19’’ core component equipped with fuel cell, power management and control system and a separated thermal split to dissipate the heat generated during the working time (backup). The result is a new generation of shelter with very interesting specifications. Experimental tests on the manufactured GreenShelter are in progress. Preliminary results confirm that in the same conditions of temperature and heat dissipation, the energetic gain of the GreenShelter solution can be up to 70% with respect to a traditional shelter with air conditioning. Not less important, the gain in terms of CapEx and OpEx could assest around 10% and 50-70%, respectively.
An OFF-GRID Base Station Powered By Sun Wind, and Water
With the fast deployment of mobile network the energy consumption is increasing at the same time. The Radio Access Network may occupy more than 60% total energy consumption of a mobile operator. How to improve the energy efficiency of the Base Stations is vital important. The renewable energy is now widely used to power the Base Stations and usually the Lead Acid Batteries are used to be the energy storage. In this paper a new hybrid pure renewable energy system for BTS is introduced. The Site is powered only by the Sun Wind, and Water. The most innovative technology is that a water electrolyzer and PEM hydrogen fuel cell is integrated together with solar panel and wind turbine as the energy storage system replacing the legacy lead acid batteries. This made the BTS can work totally off-grid and zero carbon emission.
Fuel Cell based Power System for Backup applications: Telecom Italia and other field test results
Fuel cell power system are currently under test by several different Telecommunication operators worldwide for backup applications. Compared to traditional systems (battery based ups, genset), the PEM fuel cell based power systems have both benefits (higher efficiency and better environmental impact) and drawbacks (higher cost, hydrogen supply need). In this paper a 7 kW fuel cell power system is described and the experimental data related to telecommunication and AC field tests are reported. The field test demonstrated a very good system performance either in terms of power delivery and reliability.
Energy transition technology roadmap. Distinguishing hype from reality – 2020 strategic technological plan and business targets
Climate change and global warming in particular may be a controversial scientific theory, particularly in the US, but its growing impact on business is undeniable. The energy generation landscape, to begin with, is being disrupted by the growth of renewables; transport is witnessing the affirmation of the electric car, in its pure form or as a hybrid, and, most pervasive of all, the search for energy efficiency is creating new businesses – think for example smart metering or behind-the-meter distributed generation – and is modifying existing ones in a variety of ways. Our vision of the macrotrends shaping the energy transition is consistent with the narrative of Bloomberg New Energy Finance's New Energy Outlook, to which we make extensive reference in this overview.
Optimization Models for Islanded Micro-Grids: A Comparative Analysis between Linear Programming and Mixed Integer Programming
"This paper presents a comparison of optimization methods applied to islanded micro-grids including renewable energy sources, diesel generators and battery energy storage systems. In particular, a comparative analysis between an optimization model based on linear programming and a model based on mixed integer programming has been carried out. The general formulation of these models has been presented and applied to a real case study micro-grid installed in Somalia. The case study is an islanded micro-grid supplying the city of Garowe by means of a hybrid power plant, consisting of diesel generators, photovoltaic systems and batteries. In both models the optimization is based on load demand and renewable energy production forecast. The optimized control of the battery state of charge, of the spinning reserve and diesel generators allows harvesting as much renewable power as possible or to minimize the use of fossil fuels in energy production.”
Performance Analysis of a hybrid micro-grid in Somalia
This paper presents a data analysis of an islanded diesel-PV-battery system, placed in Somalia. Operation of each generator is observed, concerning the most relevant performance indicators. Analysis is carried out during the first 11 months of operation, from November 2015 to September 2016. Investigations are divided into two periods, according to a significant load variation due to the connection of a new distribution line to the power plant. Thus, a comparison on load demand sharing among generators is realized between the two periods. In conclusion, benefits in terms of fuel consumption, CO2 emissions and money savings are presented.
Distributed storage for provision of ancillary services to the main grid: project PRESTO
This paper presents the three-year PRESTO research project (2013-2015). PRESTO is a self-funded project developed by the Department of Energy of Politecnico di Milano in cooperation with FIAMM Storage, Elvi Energy and MCM Energy Lab (an Italian spin-off). Within the project, experimental tests and numerical simulations were performed in order to evaluate the effectiveness of an Energy Storage System (ESS) in the provision of ancillary services to the main grid. This paper focuses specifically on the experimental and numerical analyses carried out in the project to develop an innovative control law for the primary frequency regulation, able to maximize the performances of the regulating service and effectively manage the ESS state of charge.
Optimal Management Algorithm for Battery Energy Storage System Included in an Islanded Micro-Grid
This work proposes an optimization method for the management of a Battery Energy Storage System (BESS) integrated in an islanded Micro-Grid, including Renewable Energy Systems (RESs) and generators burning fossil fuels. The optimized control of the battery State of Charge (SOC) allows to get the BESS available as much as possible to support the RES power production, hence minimizing the use of fossil fuels. The optimization of the BESS is based on load demand and RES production forecast. The Optimization Algorithm that has been adopted is the Linear Programming, using the method of the Interior Point.
Control loops design in a grid supporting mode inverter connected to a microgrid
This paper deals with some design aspects of the control loops in a droop-controlled VSI connected to other inverters of greater ratings or to a strong grid, which sets the frequency. The design of a damping resistor in series with the AC filter capacitor is discussed and the impact of strong feedback between the output current and the capacitor voltage is investigated. Moreover, an analysis of the derivative droop coefficients is carried out through a simplified equivalent circuit.
Hybrid micro-grid experimental application in Tanzania
This paper is intended to introduce the project Energy4Growing that aims at studying and setting up a hybrid micro-grid to supply power to a school in rural Tanzania. It describes the results of the early project actions which concerned in: (i) analysing the actual school power supply system through locally metered data; (ii) developing the first step of a new electro-mechanical model which addresses the simulation of operation and dynamics within an off-grid power system; (iii) validating the new model. In particular the paper focuses on describing the development and the first step implementation of the new modelling approach which address: (i) voltage and frequency analyses over medium term period by means of simplified electromechanical models of power sources and power electronics, (ii) the analysis of different dispatch strategies and their consequence on voltage and frequency trends, (iii) the effects of dispatch strategies on the energy performances of particular components such as battery bank or dump loads. The new approach has also been applied in modelling the current school power supply system.
Electricity tariff reform – Discourages energy efficiency
The solution suggested by the authority to resolve problems is to penalise and shift part of the financial burden on to those who produce renewable energy power, which seems to be contrary to what the legislations state. Here follows Giuseppe Artizzu’s opinion on the proposal for reform of the electricity rates of residential customers. Having summarized the proposed reform of the electricity rates for residential customers deeply discussed by the energy authority, we will host a debate about it on the following pages. We have published the opinions of GB Zorzoli the Honorary President of FREE, and of Chicco Testa, the President of Assoelettrica.
Opec had no choice
The long-awaited Opec Summit in Vienna on thursday ended with nothing concrete: cartel production in 2015 will remain the current one, despite the collapse of more than 30% of barrel price since this summer. Who has interpreted the decision as a deliberate choice by the Saudis to make a price war on American producers is wrong. Opec had no choice, the financial perspectives are grave for weaker members of the cartel, such as Venezuela and Nigeria, in a context of low oil prices. What determines the excess supply on the international oil market are not the big producers who challenge the hegemony of the Kingdom, but hundreds of small American oil companies, which drill as if there was no tomorrow. For these, the future consequences of petrol supply are not taken into consideration.
Technical Strategies for Voltage Power Regulation in LV Distribution Networks
We report the integration of a novel voltage regulation strategy in the inverter control algorithm for Dispersed Generation (DG) applications. The adoption of a decentralized voltage control based on local curves allows the voltage profile to be controlled at the Point of Common Coupling (PCC) of the generators and, therefore, the capacity of existing distribution networks to host more generation from renewables. The work is focused on a low voltage distribution network and both the reactive power modulation and the real power curtailment are considered in the proposed local strategy. Both numerical and experimental analysis are necessary in order to test and validate the proposed voltage control strategy. Firstly, the performances of the proposed control are tested by a numeral analysis and the impact on both the electrical system and the inverter apparatus is evaluated. Secondly, the benefit of the control strategy is analysed by experimental analysis in a test facility to verify the feasibility of voltage regulation in a real feeder.
Hybrid distributed generation system for a rural village in Africa
Nowadays the use of distributed generating systems, which use a renewable energy source, has experienced a fast development. Moreover, their intrinsic intermittent nature can be overcome using hybrid systems which combine more energy sources. This paper proposes the study and design of a hybrid generation system able to cover the energy needs of a school in a rural village in Africa (Tanzania), combining renewable and/or alternative sources and storage systems. The final results consist in the definition of an electric grid architecture suitable to interface renewable and energy needs in the most reliable way, exploiting advanced regulation and control techniques.
Why solar energy has systemic relevance
Photovoltaics has assumed a role, sometimes that is a dominant one in the coverage of daily requirements. Its cost, especially in southern Italy, is competitive with that of fossil fuels. The near future is auto-consumption and accumulation. How can we change the logic of the electricity market? Giuseppe Artizzu’s article published in the latest issue of the magazine QualEnergia. In 2013 photovoltaics covered 7% of Italian electric requirements, a share that has no equal in the world. But due to the seasonal profile and time, this figure is not representative of the actual role that technology has taken. However in winter, there is a tangible impact on the wholesale price of electricity, the weight on the need is still limited, in summer and even more in the late spring technology has transformed the market, arriving to cover in a structural way 15-20% of the working day (significantly more for the holidays).
Harmonic Analysis of Output Filters for Grid Connected Converters in Battery Energy Storage Systems
Battery Energy Storage Systems, as well as many distributed generation systems, use voltage source inverter as interface with the grid. These converters require a filtering section to reduce current harmonics injected to the grid. Usually, harmonic filter is a series inductance connected between grid and inverter. Higher order filters can provide better harmonic attenuation at lower switching frequency and reduce filter size, with potential benefits for high power applications. This paper deals with the sizing and the frequency response of three different harmonic filters suitable to reduce the ripple in the grid current waveform. Dynamic simulations of a 100 kW Battery Energy Storage System highlight the better performance of high order filters.
Ho to put an end to dependence on russian gas
A couple of weeks ago it was suggested, provocatively but not too much so that the Russian gas taps should be closed to buyers. Provocation or not, the developments of recent days demonstrate that the energy dependence has a political cost which is too high. Now let’s spare ourselves yet another sterile call for a diversification of sources: we need a plan and its concrete and immediate implementation. Who says it takes decades does not know the market or has a conflict of interests. Exiting from this dependance doesn’t mean stopping the import gas from Russia; it simply means reducing imports to a level that could enable, if necessary, alternatives at a tolerable cost.
Electricity market. Is the design really obsolete?
In the Italian electricity system outlined there is the hypothesis that the closure of part of the thermoelectric capacity would compromise system security. It would be better to leave the reserve margin to drop and see if commodity prices return to levels compatible with ensuring the system. An article by Giuseppe Artizzu. Until three years ago, the time profile of the equilibrium price in the market followed the electric load curve faithfully. By 2012 the photovoltaics had brought a gradual but systematic reduction of price in the central hours of the day, preceded and followed by two short spikes in the early morning and late afternoon, also helped by migrating to those times of the programmable power production. In substance the hourly price curve doesn’t follow the load but the residual load, i.e. the portion not covered by intermittent sources at zero marginal cost.