Camino Fernández

Hydrogen production: Two stage processes for waste degradation

The dark fermentation process generates hydrogen by biological means. It presents two main advantages: fulfilling requirements for mild operational conditions and gaining benefit from the residual biomass. The process itself may be seen as a pre-treatment step in a complete stabilisation chain, with the aim of attaining the valorisation of residual biomass. However, increasing the yield of H2 production is an imperative task. In this manuscript, a review of recent work in the field of fermentative hydrogen production is presented. As dark fermentation has a maximum yield of 33% (on sugars), a description is also presented of possible second stage processes for the degradation of dark fermentation effluents. Alternatives considered were photofermentation and bioelectrochemical systems (BES) as processes capable of converting fermentation sub-products into H2. Anaerobic digestion as a final stabilisation stage was also considered owing to the wide application of this technology in the treatment of bio-wastes.

Black-box modeling of DC-DC converters based on transient response analysis and parametric identification methods

Today, ¿black-box¿ behavioral models of power converters are becoming interesting for system-level analysis. These models can be used to evaluate the response of power electronics systems which are composed of commercial converters, since they can be fully parameterized by analyzing the actual converter response. In this paper a new identification method of ¿black box¿ models for DC-DC converters is presented. This method is based on the analysis of the step transient response of the converter, which is obtained by means of simple experiments. The identification of the model is carried out using well established fitting algorithms, which can be applied using commercial tools.

Genetic learning of fuzzy reactive controllers

This paper concerns the learning of basic behaviors in an autonomous robot. It presents a method to adapt basic reactive behaviors using a genetic algorithm. Behaviors are implemented as fuzzy controllers and the genetic algorithm is used to evolve their rules. These rules will be formulated in a fuzzy way using prefixed linguistic labels. In order to test the rules obtained in each generation of the genetic evolution process, a real robot has been used. Numerical results from the evolution rate of the different experiments, as well as an example of the fuzzy rules obtained, are presented and discussed.

Linear-Non-Linear Control Applied in Multiphase VRM

Microprocessors are exigent loads that require specific power supplies, voltage regulator modules (VRM), that provide a well-regulated voltage, high efficiency and very good dynamic response. Multiphase interleaving synchronous buck converters are one of the best topological alternatives. In this paper a new approach to the non-linear control of multiphase VRMs is proposed. Thanks to the non-linear control, the proposed approach provides very good dynamic response and allows higher equivalent inductance values that other solutions, which means that, from the transient response point of view, the number of phases or the frequency can be reduced

Overview of different alternatives for the contact-less transmission of energy

When a physical connection cannot exist between the power source and the load, a transformer is usually used as a power link to transfer the energy. Primary and secondary windings of this transformer are usually separated a distance that is quite large compared to its own size. This means that coupling is low and leakage inductance is higher or comparable to the magnetising inductance. Therefore, voltage gain is low and a considerable part of the primary current will flow through the magnetising inductance and go back to the power source. An important effort has been done in the last years, proposing different topologies suitable for contact-less applications and suggesting design rules in order to improve coupling of the contact-less transformer. This paper presents an overview of many of the proposals, comparing the converters results in terms of efficiency, size, coupling of the transformer and control method.

Application of a packed bed reactor for the production of hydrogen from cheese whey permeate: Effect of organic loading rate

The production of H2 was studied using a packed bed reactor with polyurethane foam acting as support material. Experiments were performed using mixed microflora under non sterile conditions. The system was initially operated with synthetic wastewater as the sole substrate. Subsequently, cheese whey permeate was added to the system at varying organic loading rates (OLR). The performance of the reactor was evaluated by applying a continuous decrease in OLR. As a result, a significant decrease in H2 yields (HY) was observed with the decrease in OLR from 18.8 to 6.3 g chemical oxygen demand (COD)/L d. Microbial analysis demonstrated that the prevalence of non-hydrogen producers, Sporolactobacillus sp. and Prevotella, was the main reason for low HYs obtained. This behavior indicates that the fermentation under non-sterile conditions was favored by high concentrations of substrate by creating an adverse environment for nonhydrogen producer organisms.

Control strategy for modular Dual Active Bridge input series output parallel

This paper is focused on a power converter system based on Dual Active Bridge modules input-series and output-parallel connected (ISOP). Converter modularization is a promising technique from a practical point of view, providing higher input voltage, lower cost and better performance. On the other hand, Dual Active Bridge converter is an interesting topology in bidirectional applications. However, the ISOP connection of DAB converters implies some important control issues, since the connection of independent modules does not ensure a proper distribution of the power, voltages and currents. In this paper a dynamic study of the DAB converter with ISOP connection is done and a control strategy is proposed to warranty a stable operation and an adequate input voltage distribution.

Reduction of the Switching Frequency and the Number of Phases in multiphase VRM by applying Linear — Non — Linear Control

Voltage Regulator Modules (VRM) are DC-DC converters that regulate the microprocessors power supply voltage. These devices require a very low and well-regulated voltage with high currents and very fast dynamic response. In addition, high efficiency values are needed because of size restrictions. Multiphase interleaving synchronous buck converters are one of the most interesting options to meet these dynamic voltage specifications. In this paper, a cost-effective and high density solution based on a classical multiphase VRM is proposed by using linear-non-linear control. This control technique provides a reduction of the number of phases and the switching frequency compared to classical control strategies based on linear control. This analysis has been validated with experimental results in a VRM prototype with eight interleaved synchronous buck converters.

Modeling methods for Solid State Power Controllers (SSPC)

There is a clear trend in the aircraft industry to use more electrical system in order to satisfy the growing aircraft load demands. This higher electrical power demand has resulted in the increase of DC voltage levels in order to reduce the power losses and the wiring size by decreasing the current levels. Traditional protections, like electromagnetic circuit breakers, are not suitable for protection of high voltage DC systems. As a consequence new technologies like Solid State Power Controllers (SSPC) have been introduced. SSPC combine the functions of connecting loads to the main electrical bus and protecting the electrical installations from overloads and short-circuits. In order to analyse these new protection devices in the onboard Power Distribution System (PDS), models of SSPC have to be developed. This paper presents and analyses two different SSPC models. The first model is based on SSPC internal structure and the second model is based on the SSPC behaviour. Finally, the SSPC behavioural model has been validated within an experimental test bench using commercial SSPC.

Supporting Efficient Multinational Disaster Response through a Web-Based System

The current process to deal with disaster mitigation has a number of drawbacks that can be solved using web technology. The basic problem is that there is a unidirectional and asynchronous flow of information among the different agents involved in a disaster mitigation procedure. This situation often results in a lack of coordination in the resources provision and in a useless assistance. In this paper we introduce ARCE, a web based system envisaged to cope with the lack of synchronism among assistance requests and responses in a multinational environment as the Latin-American Association of Governmental Organisms of Civil Defence and Protection is. ARCE makes uses of role-based access policies (RBAC) and information flow mechanisms to offer an efficient and reliable communication channel.