Large-scale Photovoltaic Farms Research Articles

Ecological construction status of photovoltaic power plants in China’s deserts

Solar photovoltaic (PV) is one of the most environmental-friendly and promising resources for achieving carbon peak and neutrality targets. Despite their ecological fragility, China’s vast desert regions have become the most promising areas for PV plant development due to their extensive land area and relatively low utilization value. Artificial ecological measures in the PV plants can reduce the environmental damage caused by the construction activity and promote the ecological condition of fragile desert ecosystems, therefore yield both ecological and economic benefits. However, the understanding of the current status and ecological benefits of this approach in existing desert PV plants is limited. Here we surveyed 40 PV plants in northern China’s deserts to identify the ecological construction modes and their influencing factors. We quantified the ecosystem service value (ESV) provided by these PV plants using remote sensing data and estimated the potential for ESV enhancement. Our results show that PV plant construction in desert regions can significantly improve the ecosystem, even with natural restoration measures (M1) alone, resulting in a 74% increase in average fractional vegetation cover (FVC) during the growing season, although the maximum average FVC of only about 10%. The integrated mode M4, which combined artificial vegetation planting M2 and sand control measures M3, further enhance the average growing season FVC to 14.53%. Currently, 22.5% of plants lack ecological measures, 40% employ only a single measure, but 92% of new plants since 2017 have adopted at least one ecological construction mode. The main influencing factors include surface type, policy support, water resources, ecological construction costs, and scientific management guidance. If artificial ecological construction were incorporated, a significant ESV could be achieved in these PV plants, reaching $8.9 million (a 7.7-fold increase) if assuming a targeted 50% vegetation coverage. This study provides evidence for evaluating the ecological benefit and planning of large-scale PV farms in deserts.

Large-Scale Photovoltaic Farms in the Qinghai Desert: Soil Quality Assessment Methods

Large-Scale Photovoltaic Farms in the Qinghai Desert: Soil Quality Assessment Methods

Economic and environmental analyses of the construction of on-site, large-scale photovoltaic farms

This paper addresses the construction of large-scale photovoltaic farms. The paper describes the issues of the current overconsumption of energy from traditional sources and the associated overuse of fossil fuels. Alternatives to these processes are presented based on literature sources, and the use of renewable energy sources, focusing on solar energy, is recommended here. In the research section, attention was focused on the economic and environmental aspects of ventures involving the construction of large-scale farms by manufacturing companies with high monthly energy consumption. In the first stage of the work, economic analyses were carried out based on data obtained from photovoltaic installation companies. For the simulation, an assessment of the costs and benefits of building a photovoltaic farm for a steel construction company located in eastern Poland was used. Another element of the research part of the study was an analysis of the results of a questionnaire survey, which was conducted among people living in the vicinity of such farms. On this basis, the environmental impact of neighbouring areas of this type of investment was estimated. Positive conclusions from the analyses made it possible to recommend the construction of this type of facility, especially for manufacturing plants with high electricity consumption.

A novel method for the site selection of large-scale PV farms by using AHP and GIS: A case study in İzmir, Türkiye

Effective and sustainable climate-friendly policies to reduce carbon dioxide emissions in line with the 2020 European Green Deal are necessary. Accordingly, renewable energies assumed a critical role, rendering the site selection of these systems very crucial. The present study proposes a novel approach to the site selection of large-scale photovoltaic (PV) plants using a combination of analytic hierarchy process (AHP) and geographic information system (GIS). In the study, the weights of criteria used for selecting solar PV panels are adjusted according to the installed capacity of the PV plant. The land of cost is included as a criterion in the AHP for the first time in PV plant site selection. Besides, a novel method called optimality-based site growing (OBSG) is introduced to further analyze the suitable sites obtained from GIS simulations and to determine the most suitable locations of PV farms. The proposed method is demonstrated with a case study of Türkiye, and the results show that the method effectively determines the most suitable locations for large-scale PV plants.

Stability of distribution network with large-scale PV penetration under off-grid operation

Large-scale photovoltaic (PV) penetration reduces system damping and causes stability problems on off-grid distribution systems. The single-machine equivalent method is typically used to simplify the full-order model by ignoring the differences in PVs. However, this results in substantial errors. When the differences between the control models of PVs are greater, the calculation results lead to greater error. Then the stability of the PV system cannot be judged. This study validated that the oscillation mode of the PV in the subsynchronous frequency band has a linear correlation with the operating conditions and control parameters. Accordingly, the authors proposed to divide the oscillation mode interval by taking the maximum and minimum PV operating conditions as the boundary to assess the stability of the system. Considering the difference in the operating conditions of the PVs, the average power was used to dynamically aggregate the PV electric farm to determine whether the system was at risk of instability. Finally, the effectiveness of the proposed method was verified through case studies on a 12-PV off-grid distribution system and a large-scale PV farm system. The verification results show that the proposed method can determine the stability of the distribution system accurately. The proposed method is significant for developing strategies to enhance the stability of off-grid distribution systems.

Identification of Factors Determining the Value of a Site for A Photovoltaic Farm: Analysis of Key Aspects

Site selection for a large-scale photovoltaic farm is a key investment decision made by development companies, significantly affecting the future success or failure of the project. Allocation of limited resources should be preceded by a multi-faceted analysis of pre-selected sites in order to select the optimal one. The evaluation should take into account all relevant economic, environmental, social, infrastructure and other criteria affecting the selection. Therefore, there is a need to develop a dedicated model for evaluating locations for their suitability and attractiveness for the construction of large-scale photovoltaic farms.

Value of deterministic day-ahead forecasts of PV generation in PV + Storage operation for the Australian electricity market

During the last decade, numerous solar forecasting tools have been developed to predict the energy generation of photovoltaic (PV) farms. The quality of solar forecasts is assessed by comparing predictions with measured solar data. However, this methodology does not consider the added value of the forecasts for their applications. As a consequence, what value could be given to the improvement of forecasts considering this evaluation framework?To answer this question, this work compares the value of different operational solar forecasts for a specific application. The aim is to look for relationships between the economic value and the error metrics defined to evaluate the forecast quality.A new generation of large-scale PV plants integrates ESS. The aim is to add flexibility to the injection of the production into the grid and thus to maximize the profit by taking advantage of the possibilities offered by the electricity market, such as energy arbitrage. To optimize the operation of these specific ESS, forecasting of the solar production is of paramount importance. The study case considered in this work is a large-scale PV farm of several megawatts associated with Li-ion batteries in the Australian energy market context.For this specific case study, the results show that the metrics used to evaluate the forecast quality based on the mean absolute error (MAE) have an almost linear relationship with the economic gain brought by applying the forecast. More precisely, an improvement of 1% point in MAE results approximately in an increase of 2% points in economical gain.

Design and Performance Analysis of a PV Control Scheme to Improve LVRT of Hybrid Power System.

Solar power stations worldwide have been rising every year as well as the usage of sustainable power has increased. The addition into the traditional electricity grid networks of renewable sources such as the photovoltaic (PV) system is an essential challenge, given its erratic power generation. The major issue is to detach PV from the faulty grid, which leads to fluctuation in the system's interconnected PV system and system-wide energy interruptions. The low voltage ride through (LVRT) enables the PV scheme should stay linked to the grid even under fault situations in short periods and must assist the grid return to regular situations according to the modern grid codes. Hence, this paper develops and analyzes five aspects of control strategy to increase PV station's LVRT capability. The in-depth simulation of the independent units of the grid-connected large-scale PV farm is accomplished using PSCAD/EMTDC to assess the feasibility of the suggested control tactic for the modified IEEE nine-bus system.

Applying a Relationally and Socially Embedded Decision Framework to Solar Photovoltaic Adoption: A Conceptual Exploration

Solar photovoltaic (PV) energy technology can play a key role in decreasing the amount of carbon emissions associated with electrical energy production, while also providing an economically justifiable alternative to fossil fuel production. Solar energy technology is also extremely flexible in terms of the size and siting of technological development. Large scale PV farms, however, require access to large tracts of land, which can create community-scale conflict over siting solar energy development projects. While previous scholarship offers frameworks for understanding the mechanisms at play in socio-technological system transitions, including the renewable energy transition, those frameworks fail to center community priorities, values, and concerns, and therefore often do not provide an effective means of addressing community conflict over solar siting. This paper provides a conceptual exploration of how a proposed framework can guide decision making for solar development across multiple scales and settings, while also illuminating the potential barriers and bottlenecks that may limit the potential of solar energy development to occur in scales and forms that receive community acceptance and at the pace necessary to address the greenhouse gas emissions currently contributing to the rapidly changing global climate.

Damping of Low-Frequency Oscillations in Power Systems by Large-Scale PV Farms: A Comprehensive Review of Control Methods

Global warming and the desire to increase the use of clean energy have led to increasing the installation and operation of renewable energy power plants (REPPs), especially large-scale photovoltaic (PV) farms (LPFs). Given that the LPFs are added to power system or replace conventional power plants, they must be able to perform the basic tasks of synchronous generators (SGs). One of these tasks is the ability to mitigate the low-frequency oscillation (LFO) risk. Also, one of the LPFs problems is reducing the power system inertia and increasing the risk of LFOs. Therefore, these types of power plants must damp the LFOs through a power oscillation damping controller (PODC), similar to the performance of power system stabilizers (PSSs) in the SGs. This paper represents an overview of the different PODCs and control methods for LFOs damping by LPF. It seems that it can be a driver for future studies. Different studies show that the application of PODCs for LPFs can play an effective role to damp the LFOs and increase the power system stability.

Targeted poverty alleviation through photovoltaic-based intervention: Rhetoric and reality in Qinghai, China

• We evaluate the implementation and potential impact of solar energy-based poverty reduction program in Qinghai, China. • PV stations, precisely planned to fulfill ‘targeted’ intervention, were aggregated into larger PV farms in implementation. • It is challenging to precisely target the poor, improve income, facilitate energy transition, and enhance local capacity. • Future energy-based development needs to sufficiently consider local contexts and promote local engagement. In 2014, China initiated a nationwide poverty reduction campaign through deploying photovoltaic (PV) systems in its vast rural areas, which aims to support over 2 million households. Despite the significant socioeconomic benefits anticipated by policy-makers, it remains unclear regarding the challenges of implementing such an ambitious program in remote rural areas and its effect on poverty reduction. Focusing on Qinghai, a province that serves as the testbed for solar energy development in China but suffers chronic poverty, we aim to assess implementation status of the program, and examine whether and how solar energy-based development affects rural household well-being and generates socioeconomic spillovers. Using data from multiple sources, including household survey, interviews, policy documents, and large-scale socioeconomic covariates, as well as advanced statistical and spatial analyses, we find there have been substantial adjustments to the plan of building small-scale PV stations across poor villages throughout Qinghai. While total installation capacity was met, the 97 planned PV stations in 39 counties were aggregated into 24 medium- to large-scale PV farms in 27 counties. We also find substantial challenges to precisely target the poor, improve their income, facilitate a transition in household use of energy, and enhance local capacity for economic development. Future PV-based intervention programs need to sufficiently consider local contexts and demands, and promote local engagement to achieve the twin goals of sustainable energy transition and poverty reduction.

Interview

Shamsodin Taheri Shamsodin Taheri, from the University of Quebec Outaouais, Canada, talks to us about his group's submission “Analysis of electrical behaviour of PV arrays covered with nonuniform snow” page 192. I am an Associate Professor of Electrical Engineering in the Department of Computer Science and Engineering at the Université du Québec en Outaouais (UQO). The expertise of my research group in the field of power energy has advanced our understanding of the performance of photovoltaic (PV) sources in cold-climate conditions. This research was inspired by the issues that PV plants in Canada experience during cold months. In recent years, we have collaborated with several industry partners, who own utility-scale PV plants, to evaluate the performance of their facilities. This ongoing research helps mitigate the technical challenges facing the integration of renewable energy sources into power grids in cold regions. PV systems have found different applications in cold areas for a long time, such as remote research facilities in the South and North Poles and space travelling. The majority of PV energy plants are presently installed in geographical cold locations with a considerable amount of snowfall every year. Furthermore, the solar energy industry is expanding competitively in cold climate regions. For example, in Canada, the installed capacity of solar PV grew from 95 MW to more than 2500 MW during 2009–2016. PV panel efficiency is not only influenced by PV technology, but environmental conditions can also influence their energy production. Accumulation of snow/ice decreases solar radiation reaching the PV panels, which results in a significant loss of power generation. Non-uniform snow accretion on PV panels often occurs due to ambient conditions such as wind, temperature variation, partial snow shedding and ground interference. This leads to power loss that is dependent on the configuration of the PV system. Owing to the increasing deployment of PV systems, there is a significant interest in optimal utilisation of PV potential in cold climate regions. A fundamental need for knowledge of the impact of nonuniform snow accretion on PV systems is therefore essential. This research has shown that the snow-covered PV panels can still produce a significant amount of energy depending on the pattern and depth of the snow accumulation. The portion of this energy that could be collected is decided by configuration of the PV array as well as the maximum power point tracking (MPPT) technique. Investigations concerning the effect of bypass diodes have shown that the PV string without bypass diodes generally experiences more power loss. In addition, the vertical and horizontal PV array layouts were tested to determine power loss due to nonuniform snow accretion. The horizontal PV array layout would be more effective in snowy climates. This work is helpful for PV system performance assessment, MPPT development and testing, power generation prediction, and proper arrangement of panels in cold regions. The accumulation of snow on PV modules weakens the intensity of incoming solar radiation and hence limits their ability to generate electricity during cold months. However, the true extent of such impact on the energy production of PV modules cannot be specified in a straightforward way, since it is not proportional to the snow-covered area. In some instances, snow covering only one cell can reduce the efficiency of a whole module by a noticeable amount. Snow is a complex phenomenon, and a quantitative characterisation of radiation transmittance through snow coverage requires knowledge of the physical properties of snow. In fact, the interaction of sunlight with snow to determine the influence of snow coverage on the PV modules is a challenge. This leads to changing the electrical characteristics of the PV array and producing multiple, local peaks on PV characteristics. Accurate modelling of the electric behaviour of PV modules and systems is a key element in improving system operation and efficiency. Hence, proper modelling approaches of the operation of PV generators under varying environmental conditions that improve their performance control and assist the design of PV converters and their MPPT controller have been achieved. Moreover, an appropriate tool has been proposed to determine the efficiency of PV farms under cold conditions. Furthermore, a high performance MPPT technique has been proposed to harvest the maximum energy of a PV array with multipeak characteristic under partial shading condition. Major progress must be made on the proper design and arrangement of PV arrays and power electronic interfaces, minimising the effects of snow on large-scale PV farms and the increasing the use of bifacial PV modules as a candidate for cold regions over the next ten years.

Deep Learning Based Module Defect Analysis for Large-Scale Photovoltaic Farms

The efficient condition monitoring and accurate module defect detection in large-scale photovoltaic (PV) farms demand for novel inspection method and analysis tools. This paper presents a deep learning based solution for defect pattern recognition by the use of aerial images obtained from unmanned aerial vehicles. The convolutional neural network is used in the machine learning process to classify various forms of module defects. Such a supervised learning process can extract a range of deep features of operating PV modules. It significantly improves the efficiency and accuracy of asset inspection and health assessment for large-scale PV farms in comparison with the conventional solutions. The proposed algorithmic solution is extensively evaluated from different aspects, and the numerical result clearly demonstrates its effectiveness for efficient defect detection of PV modules.

Optimal Damping Controller Design for Large-scale PV Farms to Damp the Low-frequency Oscillation

With increasing the number of large-scale photovoltaic (PV) farms (LPFs) connected to the power grids in the world, some characteristics of power systems are affected. Studies show that the LPFs could have the negative effect on low-frequency oscillation (LFO) relative to their location and size. Considering that the LPFs cannot be located in ideal points and their installation location depends on geographical conditions, it is important to consider an auxiliary controller as a damping controller for them. On the other hand, the new generation of LPFs has a centralized plant controller (CPC) for voltage and power regulation at the point of common coupling (PCC); therefore, it is required to add the damping controller to the CPC. In this paper, the LFO damping by an optimal damping controller (ODC) that implemented in the CPC of LPFs is proposed. The ODC structure is a single input 2nd-order lead-lag controller. A benchmark test system for LFO studies is used to show the performance of the proposed ODC. The robustness of ODC is assessed in the different operating conditions. The simulation results demonstrate the proper function of the proposed ODC for the wide range of operating conditions.

Real-Time Coordinated Voltage Control of PV Inverters and Energy Storage for Weak Networks With High PV Penetration

There are more large-scale photovoltaic (PV) plants being established in rural areas due to availability of low-priced land. However, distribution grids in such areas traditionally have feeders with low X/R ratios, which makes the independent reactive power compensation method less effective on voltage regulation. Consequently, upstream step voltage regulator (SVR) may suffer from excessive tap operations with PV-induced fast voltage fluctuations. Although a battery energy storage system (BESS) can successfully smooth PV generation, frequent charge/discharge will substantially affect its cost effectiveness. In this paper, a real-time method is designed to coordinate PV inverters and BESS for voltage regulation. To keep up with fast fluctuations of PV power, this method will be executed in each 5 s control cycle. In addition, charging/discharging power of BESS is adaptively retuned by an active adjustment method in order to avoid BESS premature energy exhaustion in a long run. Finally, through a voltage margin control scheme, the upstream SVR and downstream PV inverters and BESS are coordinated for voltage regulation without any communication. This research is validated via a real-time digital simulator MatLab cosimulation platform, and it will provide valuable insights and applicable strategies to both utilities and PV owners for large-scale PV farm integration into rural networks.

A two-level control strategy with fuzzy logic for large-scale photovoltaic farms to support grid frequency regulation

This study proposes a two-level coordinated control strategy with fuzzy logic for appropriately adjusting the total active power supplied to a grid by large-scale photovoltaic (PV) farms in order to regulate grid frequency. For a solar farm, the strategy includes a central coordinating controller and many local controllers at PV power assemblies, treated as agents. In detail, the central controller uses a frequency regulation module based on a new automatic-tuning fuzzy-logic controller scheme to compute the appropriate reference values according to the total power needed. Then, the individual reference value for each local controller is determined. Each local controller governs all power-electronic converters installed at the PV agent to inject power into the grid according to the individual reference value received. Additionally, each local controller uses an algorithm to manage the state-of-charge of the battery bank installed at the agent so that it remains in the safe range of 20–80% while operating and close to the desired idle value of 50% at the steady state. Besides, a special control mode is developed and integrated into the overall strategy to aid rapid recovery of the grid frequency under emergency conditions. Numerical simulations demonstrate that the suggested strategy has the good response in terms of injecting an appropriate amount of power into the grid to regulate the frequency deviation into acceptable ranges of ±0.2 (Hz) in the transient state and ±0.05 (Hz) at the steady state, even when the weather conditions (solar radiation, air temperature), AC system load, and important control parameters of the grid suddenly change. Furthermore, the effectiveness in improving the grid-frequency stabilization by using the proposed strategy is validated within a four-area power system, where four PV farms are connected and the operating parameters of the grids at the areas are fairly different.