Abstract
A new coupled optical, thermal and electrical model is presented in this study and applied to a concentrating photovoltaic thermal (PV/T) system for predicting the system performance under various operational conditions. Firstly, a three-point-based electrical model and a method for extracting its five model parameters are developed by using the currents and voltages at the short-, open-circuit and maximum power points provided in usual PV module/panel datasheets. Then, the model and method are validated with the existing six flat-plate PV modules and subsequently are used to predict the hourly electrical performance of the CPV/T roof-top system designed by us under outdoor conditions on four clear days by integrating with a scaling law developed by us. Additionally, transient effect and water temperature on the storage tank are examined. It turned out that the CPV system could operate for 6 h a day with a peak instant electrical power of 50W/m2 and could generate 0.22kWh/m2 electricity a day in May–July. The error in hourly electrical energy gained between the predictions and observations is in a range of (3.64–8.95)% with the mean of 5.53% in four days, and the estimated water temperature in the storage tank agrees with the monitored one in range of 0.2–1 °C. The proposed methods as well as the electrical models could potentially be applied widely across the solar energy field for the management and operation of the electrical energy production from any CPV/T roof-top system.
Highlights
Electrical parameters at short- and open-circuit, and maximum power points are contained in all the flat-plate photovoltaic (PV) module datasheets which are usually measured under standard test condition (STC) (1 kW/m2 irradiance, 25 C cell temperature), whilst their current-voltage (IeV) curves are presented occasionally
We propose an analytical plus optimization method for extracting the five parameters of a singlediode electrical model for the new roof-top system based on the sensitivity analysis of n0, Iph0, Id0, Rs0 and Rsh0 performed previously in Ref. [23]
It was showed in that paper that the influence of n0, Iph0, Id0, Rs0 and Rsh0 on I has a ranking n0 > Iph0 > Id0 > Rs0 > Rsh0 from the most important to the least important. Based on this outcome, we propose that the three parametersn0, Id0 and Rs0, should be decided by an optimization algorithm defining the IeV equations at three points and the dP=dV equation at maximum power point (MPP), while Iph0 and Rsh0 are calculated analytically and iteratively with their expressions derived at short-circuit point (SCP) and MPP to achieve a better accuracy for a set of five parameters
Summary
Electrical parameters at short- and open-circuit, and maximum power points are contained in all the flat-plate photovoltaic (PV) module datasheets which are usually measured under standard test condition (STC) (1 kW/m2 irradiance, 25 C cell temperature), whilst their current-voltage (IeV) curves are presented occasionally. We propose an analytical plus optimization method for extracting the five parameters of a singlediode electrical model for the new roof-top system based on the sensitivity analysis of n0, Iph0, Id0, Rs0 and Rsh0 performed previously in Ref. It was showed in that paper that the influence of n0, Iph0, Id0, Rs0 and Rsh0 on I has a ranking n0 > Iph0 > Id0 > Rs0 > Rsh0 from the most important to the least important Based on this outcome, we propose that the three parametersn0, Id0 and Rs0, should be decided by an optimization algorithm defining the IeV equations at three points and the dP=dV equation at MPP, while Iph0 and Rsh0 are calculated analytically and iteratively with their expressions derived at SCP and MPP to achieve a better accuracy for a set of five parameters. The estimated results will be compared with the observations to confirm the feasibility of the method
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