A review of photovoltaic (PV) cell operating temperature (T c ) steady-state models developed from the year 2000 onward is shown in the present article. The goal is to help researchers and professionals in the field to choose the most significant parameters and suitable experimental arrangements to compose an accurate steady-state model. Initially, a brief description of T c is given and an overview of the models for calculating T c is presented. We present a summary of 33 correlations found in the literature for estimating T c and the synthesis of those correlations in three general forms. Additionally, we highlight the main parameters in the analyzed correlations along with their most accurate data collection methods. The parameters with the greatest influence on T c , appearing in a significant number of formulations, are discussed: solar absorbance, electrical efficiency, and transmittance of the PV cell/module glass cover; irradiance; ambient temperature; wind speed. Strategies of obtaining T c -using the module back side temperature or an internal sensor for direct measurement-for model validation purposes are also discussed.
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AbstractThe assessment of Intermittent Gas Lift (IGL) by computer calculations using the mechanistic models found in the literature usually approaches the IGL's operating cycle as a sequence of independent non-interacting stages, occurring back-to-back, without overlapping in time; that approach restricts the system analysis to the limited range of operational conditions when such particular behavior indeed exists. In fact, out of such range, some stages of the IGL cycle may be rather simultaneous than sequential, as previously assumed. This paper presents a new IGL mechanistic model and simulation scheme to consider the possible occurrence of both sequential and simultaneous stages throughout the IGL cycles. The dynamics of the IGL cycles is assessed through a simultaneous and coupled variable set of non-linear algebraic and time-differential equations, interactively defined on the run and solved according to the ongoing stages of the IGL cycle. A case study for a typical IGL well, producing from a low productivity reservoir partially depleted, at different operational conditions, shows how the IGL computer simulator can help the operator to set up the IGL parameters to maximize the well production or its economic gain.
The Intermittent Gas Lift (IGL) is an artificial lift method for petroleum production suitable for producing wells from depleted or low productivity reservoirs. In order to enhance the well production, many variants of the conventional IGL have been developed and used worldwide. One of these variants, the Inverted IGL (IGL-I), consists of removing the gas lift valve and reversing the flow paths inside the well: gas is injected through the tubing whereas liquid is lifted through the casing annulus. The oil production is believed to increase with the IGL-I due to the larger annulus storage capacity, at the expense of higher injected gas volumes. Despite of its potential for practical applications, the IGL-I has not been covered by the literature. Aiming to surmount such gap in the literature, this paper presents a model for the dynamical behavior of the IGL-I wells. The complexity emerged from the IGL-I cyclic operation is assessed through a simultaneous and coupled simulation scheme, comprising a variable set of non-linear algebraic equations and non-linear time-differential equations for the flow of oil and gas throughout the injection, transfer, elevation, production, decompression and loading stages of each cycle. The simulator provides the engineer with a valuable tool to investigate the well behavior of several IGL cycles. Based on the observed results, the designer may propose practical recommendations regarding the IGL-I design and operation.
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