• Energy Research

In this work, we have characterized single nickel metal hydride (NiMH) cells with Electrochemical Impedance Spectroscopy (EIS) technique to determine online the state of the batteries. Studying the variations of the obtained impedance spectra at specific frequencies, which correspond to part of the spectra that change mostly during the charge and discharge processes of the batteries, we have constructed and interpreted diagnostic diagrams through a mathematical model based on Dempster-Schafer Theory of Evidence in order to determine the SOH.

Abstract The State of Health (SOH) of a battery is important to know the maximum energy that a battery can release while is operative and to plan the correct maintenance. In this work, we have implemented a diagnostic method to evaluate the SOH of single nickel metal hydride (NiMH) cells, that have an important role in power tools applications. Single NiMH cells of 1.2 V and 1.3 Ah have been characterized with Electrochemical Impedance Spectroscopy (EIS) technique to evaluate the SOH with synthetic methods. Through the study of an equivalent circuit model, we determine that three free parameters synthesize the information contained in an impedance spectrum. A new simplification allows us to construct a diagnostic diagram with only two degree of freedom. A mathematical approach based on the Dempster–Schafer Theory of Evidence has been implemented to interpret the diagnostic diagram. Combining the points obtained by the impedance spectra (IS) at different State of Charge (SOC) and SOH, the Theory of Evidence can improve the estimation of the SOH iteratively, a great advantage compared to the classic Theory of Probability.

This work has the purpose to analyze thermal performance of emergency shelters with the aim to develop different solutions which can improve the internal environmental conditions, in accordance to the parameters that describe thermo-hygrometric comfort, to the materials of which they are generally made of and to the climatic conditions under which they may be exposed. The object of the study was a tent equipped with a photovoltaic system produced by CHOSE (Center for Hybrid and Organic Solar Energy) at the University of Rome Tor Vergata. Through the use of the software IDA Indoor Climate and Energy 4.5, a simulation model was built based on experimental data collected from May 7 to May 15, 2013; model calibration was carried out comparing the simulation with the experimental data and the model was used for the formulation of different improvement solutions. The shelter model was analyzed in two different Italian climatic conditions using climatic data from Torino (winter) and Palermo (summer). The suggested optimization solutions were proven to be useful to improve the indoor climate and energy needs of the unit. The procedure can be applied to various climatic conditions and to different locations.