S.A. Gamboa

Electrodeposited and selenized (CuInSe2) (CIS) thin films for photovoltaic applications

Abstract In the present communication, the authors report results on the characterization of electrodeposited and selenized (CuInSe 2 ) (CIS) thin films. The selenization process was carried out using a technique called chemical vapor transport by gas (CVTG). The precursors as well as selenized films were characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM) and electron microprobe analysis (EPMA). The film stoichiometry improved after selenization at 550°C. The films were formed with a mixed composition of the binary as well as the ternary phases.

A CdTe/PMeT photovoltaic structure formed by electrodeposition and processing

CdTe thin films were electrodeposited from an ethylene-glyco-based bath by the galvanostatic method. As-deposited and tellurized films were characterized by structural, optoelectronic and photoelectrochemical methods. The film stoichiometry improved after tellurization of the film at 300°C by a technique called chemical vapor transport by Gas (CVTG) in a tubular furnace. Tellurized films showed near stoichiometry with p-type conductivity in the bulk and n-type surface conductivity. Schottky barrier type photovoltaic junctions were obtained using a heavily doped PMeT (poly-3(methylthiophene), prepared by electropolymerization, displaying nearly metallic behavior, and CdTe obtained by electrodeposition. A solar to electrical conversion efficiency of the order of 1% was obtained in the case of PMeT/CdTe junction.

Temperature, cycling, discharge current and self-discharge electrochemical studies to evaluate the performance of a pellet metal-hydride electrode

Abstract In this paper, we report electrochemical charge/discharge of hydrogen for a pellet metal-hydride electrode using an MmNi5−XMX alloy as active material. Strong dependence of temperature and discharge current was found for electrochemical applications. Pellet electrode showed good stability over 250 charge/discharge cycles. Self-discharge studies were carried out on completely charged electrode. The capacity of this electrode to absorb/desorb hydrogen could be defined as a stochastic function of some variables like temperature, cycling and discharge current conditions. More studies are in progress for calculating electrochemical parameters in these metal-hydride electrode systems.

Photovoltaic structures based on polymer/semiconductor junctions

CdTe and CuInSe 2 (CIS) thin films were electrodeposited and characterized for photovoltaic applications. Schottky barrier-type photovoltaic junctions were obtained using a heavily doped PMeT (poly-3-methylthiophene), prepared by electropolymerization, displaying nearly metallic behavior, and semiconductors such as CdTe and CIS obtained by electrodeposition. The photovoltaic structures formed and studied are Mo/CIS/PMeT/grid and Mo/CdTe/PMeT/grid Schottky barrier junctions. Solar to electrical conversion eƒciency of the order of 1% was obtained in the case of PMeT/CIS and PMeT/CdTe junctions. ( 1998 Elsevier Science B.V. All rights reserved.

Cyclic Voltametry Investigation of a Metal Hydride Electrode for Nickel Metal Hydride Batteries

In this study, an -type hydrogen-absorbing alloy, was used as the negative electrode material. The metal-hydride (MH) electrode was charge/discharged over 200 cycles. The discharge capacity of the alloy was 250 mAh g−1. The specific discharge capacity as a function of discharge current density and temperature effect is also discussed. Hydrogen diffusion reaction in the MH alloy powder of the negative MH alloy electrode dominates the high-rate discharge capability of the metal hydride electrode in a nickel metal hydride (Ni/MH) battery. Cyclic voltametry technique was used to analyze the charge-transfer reactions at the electrode/electrolyte interface and hydrogen surface coverage capacity. The charge-transfer reaction in the negative electrode reflects a capability of hydrogen reduction and oxidation reactions at the electrode/electrolyte interface.

A documented analysis of renewable energy related research and development in Mexico

The research and development of renewable energy sources in Mexico has recently started to be considered as a form of contributing to solve the environmental problems caused by the irrational use of fossil fuels to meet the human and industrial energy requirements. The major areas of renewable energy research in Mexico are solar thermal energy, photovoltaic energy, wind energy, geothermal energy, materials for renewable energy, energy planning and economy and lately new programs such as hydrogen energy, fuel cells, etc. In Mexico, there are many important institutions such as universities, research centers and industries working on research, development and analysis of renewable energy sources. The industrial involvement is comparatively less in this kind of research. In this work we present results from a documented, statistical and analytical research carried out on the renewable energy related research and development activities in various important Mexican research and development institutions. Many factors affecting the complete understanding of the research and development of renewable energy sources are presented in this paper.

Thermodynamics of Fuel Cells

In this chapter the basic thermodynamic and electrochemical principles behind fuel cell operation and technology are described. The basic electrochemistry principles determining the operation of the fuel cell, the kinetics of redox reactions during the fuel cell operation, the mass and energy transport in a fuel cell, etc., are described briefly to give an understanding of practical fuel cell systems. The ideal and practical operation of fuel cells and their efficiency are also described. This will provide the framework to understand the electrochemical and thermodynamic basics of the operation of fuel cells and how fuel cell performance can be influenced by the operating conditions. The influence of thermodynamic variables like pressure, temperature, and gas concentration, etc., on fuel cell performance has to be analyzed and understood to predict how fuel cells interact with the systems where it is applied. Understanding the impact of these variables allows system analysis studies of a specific fuel cell application.

Electrochemical characterization of a MmNi5−xMx electrode for rechargeable Ni/MH battery

Abstract In this paper, we report results obtained from the electrochemical characterization of MmNi5−xMx electrodes supported on nickel foam substrates. Results of structural and compositional characterizations are also presented. The results obtained in this work indicate that the MmNi5−xMx electrodes possess potential characteristics for hydrogen evolution reaction (HER) and for hydrogen storage.

State of the Art of Sorption Refrigeration Systems

Sorption cooling systems have been used commercially for some decades for different applications including air conditioning and refrigeration, using a diverse range of thermodynamic cycles and technologies for many size and capacities. However, their use has been limited mainly because of their low efficiency and high investment costs, at least compared with compression systems that are widely used all over the world. Because of this, sorption and desiccant systems have been used, in general, only when large amounts of waste thermal energy that can be used as the energy supplied to the system are available, and recently with, for example, solar and geothermal technologies.

Cogeneration Fuel Cells – Air Conditioning Systems

As already discussed in Chapter 1, energy is a finite resource and its rational use implies an increase in energy efficiency. The electric generation efficiency is always less than 100% due to resistive, transmission and distribution losses, which can be quantified as heat sent to the environment. This waste heat determines the quantity of energy that can be used by other systems in order to improve the process efficiency.