A method for obtaining the I-V curve of photovoltaic arrays from module voltages and its applications for MPP tracking

For the purpose of control and monitoring of a Photovoltaic (PV) system its current-voltage (I-V) charac- teristic curve is traced. Usually such a test involves the interruption of the normal operation of the PV systems. In this paper a method for tracing the I-V curve from on-site measurements is proposed. During the measurement of the characteristic curve the normal operation of the PV system is not inter- rupted. The subjects of tracing the characteristic curve and Maximum Power Point Tracking (MPPT) of PV arrays are generally dealt with separately but the proposed method performs the measurement of the characteristic curve quickly and so it can also be utilized for MPPT purposes. Simulations and experi- ments have been conducted to confirm the operation of the proposed metho

Hourly Simulation of Energy Community with Photovoltaic Generator and Electric Vehicle

Europe has set the ambitious goal to become the first carbon-neutral continent by 2050. Therefore, it has undertaken several initiatives to promote the energy transition, including the active participation of citizens in the energy sector. In this context, recent European directives introduced the concept of energy community, whose members can consume, share, and store energy locally produced. This work proposes an energy and economic simulation of a renewable energy community powered by a 19.2 kWp photovoltaic system in the province of Cuneo, in Piedmont (Italy). The community consists of a prosumer, which owns the photovoltaic system and a charging station for electric vehicles, and other 17 energy users. Suitable indicators to assess the energy performance of the community (self-consumption and self-sufficiency) were evaluated starting from the estimated production and consumption power profiles. Then, an economic simulation was carried out to assess the economic return on the investment for the member who bore the initial costs and the annual economic savings for the others

Towards the Complete Self-Sufficiency of a nZEBs microgrid by Photovoltaic Generators and Heat Pumps: Methods and Applications

The present paper proposes a multidisciplinary procedure to correctly design a microgrid of all-electric nZEBs (nearly Zero Energy Buildings) from both electrical and thermal points of view. The procedure is suitable for new buildings supplied by local renewables, without the use of fossil fuel and with zero emissions. First, the thermal demand of each single nZEB is assessed, as a function of the installation site, building layout and physics, and material composing the envelope. Thanks to heat pumps, the thermal demand is transformed in electric load. Thus, the total electric consumption profiles, which include user's appliances and heating/cooling, are studied and compared with Photovoltaic (PV) generation supported by electrochemical storages. Both PV and batteries are simulated thanks to appropriate models. Regarding the PV production assessment, the present work proposes an improvement with respect to the use of traditional models, and it is based on experimental results on PV generators of recent production. The design methodology is applied to a real case of “energy community” composed of three nZEB units, that will be built in the campus of Politecnico di Torino, available to students and staff. The three units share PV production and storage capacity to reach the complete grid-independence

A Smart Battery Management System for Photovoltaic Plants in Households Based on Raw Production Forecast

A basic battery management system (BMS) permits the safe charge/discharge of the batteries and the supply of loads. Batteries are protected to avoid fast degradation: the minimum and maximum state-of-charge (SOC) limits are not exceeded and fast charge/discharge cycles are not permitted. A more sophisticated BMS connected to a photovoltaic (PV) generator could also work with the double purpose of protecting storage and reducing peak demand. Peak reduction by storage generally requires the forecast of consumption and PV generation profiles to perform a provisional energy balance. To do it, it is required to have accurate information about production profiles, that is, to have at disposal accurate weather forecasts, which are not easily available. In the present work, an efficient BMS in grid-connected PV plants for residential users is described. Starting from raw 1-day ahead weather forecast and prediction of consumption, the proposed BMS preserves battery charge when it is expected high load and low PV production and performs peak shaving with a negligible reduction in self-sufficiency

Experimental evidence of PID effect on CIGS photovoltaic modules

As well known, potential induced degradation (PID) strongly decreases the performance of photovoltaic (PV) strings made of several crystalline silicon modules in hot and wet climates. In this paper, PID tests have been performed on commercial copper indium gallium selenide (CIGS) modules to investigate if this degradation may be remarkable also for CIGS technology. The tests have been conducted inside an environmental chamber where the temperature has been set to 85 \ub0C and the relative humidity to 85%. A negative potential of 1000 V has been applied to the PV modules in different configurations. The results demonstrate that there is a degradation affecting the maximum power point and the fill factor of the current\u2010voltage (I\u2010V) curves. In fact, the measurement of the I\u2010V curves at standard test condition show that all the parameters of the PV modules are influenced. This reveals that CIGS modules suffer PID under high negative voltage: this degradation occurs by different mechanisms, such as shunting, observed only in electroluminescence images of modules tested with negative bias. After the stress test, PID is partially recovered by applying a positive voltage of 1000 V and measuring the performance recovery of the degraded modules. The leakage currents flowing during the PID test in the chamber are measured with both positive and negative voltages; this analysis indicates a correlation between leakage current and power losses in case of negative potential

Assessing the role of variable renewables in energy transition: methodologies and tools

Due to the environmental impacts brought by current energy schemes, the energy transition, a new paradigm-shift from fossil fuels to renewable energy, has been widely accepted and is being realized through collective international and local efforts. Electricity, as the most direct and effective use of renewable energy sources (RES), plays a key role in the energy transition. In this paper, we first discuss a viable pathway to energy transition through the electricity triangle, highlighting the role of RES in electricity generation. Further, we propose methodologies for the planning of wind and solar PV, as well as how to address their uncertainty in generation expansion problems. Finally, by using a web-based tool, “RES-PLAT” 1 , we demonstrate the scheme in a case study of the North Africa, which evaluates the impacts and benefits of a large-scale RES expansion

Self-Consumption and Self-Sufficiency in Photovoltaic Systems: Effect of Grid Limitation and Storage Installation

This paper presents a methodology to maximize the self-sufficiency or cost-effectiveness of grid-connected prosumers by optimizing the sizes of photovoltaic (PV) systems and electrochemical batteries. In the optimal sizing procedure, a limitation on the maximum injection in the grid can affect the energy flows, the economic effectiveness of the investments, and thus the sizing results. After the explanation of the procedure, a case study is presented, and a parametric analysis of the effect of possible injection limits is shown. The procedure is applied to size plants for an Italian domestic prosumer, whose electric load profile was measured for a year. A software program developed using the proposed methodology is also briefly presented. It is used for both research and educational purposes, both in laboratory classes and in remote lesson

In-field monitoring of eight photovoltaic plants: degradation rate along seven years of continuous operation

The results of more than seven years (October 2010-December 2017) of continuous monitoring are presented in this paper. Eight outdoor photovoltaic (PV) plants were monitored. The monitored plants use different technologies: mono-crystalline silicon (m-Si), poli-crystalline silicon (p-Si), string ribbon silicon, copper indium gallium selenide (CIGS), thin film, and cadmium telluride (CdTe) thin film. The thin-film and m-Si modules are used both in fixed installations and on x-y tracking systems. The results are expressed in terms of the degradation rate of the efficiency of each PV plant, which is estimated using the measurements provided by a multi-channel data acquisition system that senses both electrical and environmental quantities. A comparison with the electrical characterization of each plant obtained by means of the transient charge of a capacitive load is also made. In addition, three of the monitored plants are characterized at module level, and the estimated degradation rates are compared to the values obtained with the monitoring system. The main outcome of this work can be summarized as the higher degradation rate of thin-film based PV modules with respect to silicon-based PV modules.</p

Synergistic freshwater and electricity production using passive membrane distillation and waste heat recovered from camouflaged photovoltaic modules

A sustainable supply of both freshwater and energy is key for modern societies. In this work, we investigate a synergistic way to address both these issues, producing freshwater while reducing greenhouse gas emissions due to electricity generation. To this, we propose a coupling between a photovoltaic (PV) device and an innovative desalination technique based on passive multi-stage membrane distillation. The passive distillation device is driven by low-temperature heat and does not need any mechanical or electrical devices to operate. The required heat is recovered from the back side of the PV device that, for the first time, mitigates the aesthetic and environmental impact thanks to an innovative surface texture. The aim is to demonstrate the feasibility to generate PV electricity from the sun and, simultaneously, freshwater from the waste heat. The solution is studied by numerical simulations and experiments at the same time, achieving a good accordance between these two approaches. The device is able to produce up to 2 L m-2 h-1 of freshwater under one sun irradiance. Furthermore, a relative photovoltaic efficiency gain of 4.5% is obtained, since the temperature of the PV module is reduced by 9 °C when coupled with the desalination technology. This work paves the way to compact installations made of such passive units, which may easily provide energy and safe water with low environmental and visual impact, especially in off-grid areas and emergency conditions

An Innovative Method to Evaluate the Real Performance of Wind Turbines: Case Study from Mauritania

The power-wind speed curve of a Wind Turbine (WT) is measured by the manufacturer in ideal conditions, and the wind speed is detected at the entrance of the WT rotor. However, in wind power plants, this quantity is rarely available because, generally, the wind speed is measured by an anemometer behind the WT. In this case, this value is lower than the wind speed at the entrance of the WT rotor. As a result, the WT performance, evaluated using these wind speed data, may be unrealistic. Thus, their correction is performed by a technique similar to instrument calibration in which the data distribution is compared with the wind speed of the manufacturer's power curve. In this context, the present work proposes an innovative method to correctly assess the performance of WTs. In particular, it is based on the manufacturer curve, correcting the wind speeds measured behind the WTs rotor. The correction is applied to one WT (rated power = 2 MW) of a wind farm in Mauritani