Decentralized renewable energy solutions to foster economic development
Electricity supply and socio-economic development are closely linked. Innovative, sustainable decentralized energy solutions represent indeed the most efficient instrument to promote electricity access in remote and low load density areas. Within this framework efficient generation technologies are crucial for the provision of electricity access and, in turn, to foster local development although not yet sufficient to directly spur sustained growth. Inclusive business models able to foster productive uses of energy are necessary, although the cycle jump-start requires many different inputs. The following study will therefore analyze the existing nexus between electrification and development, further highlighting the important role of having a holistic point of view and building strong partnerships to achieve the most efficient and sustainable business model. Finally, systematic know-how dissemination and a consistent regulatory framework for decentralized energy systems will represent key elements for an effective energy policy within emerging economies.
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.
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.