Power Generation

In an exclusive preview of a forthcoming paper in PV Tech Power, LONGi Solar and Huawei present their analysis from a bifacial project in the Middle East.

Leading PV inverter manufacturer Huawei discusses recent technical developments to a better understanding of bifacial solar module PV power plants, using three recent case studies. These efficient PV modules need to be used with devices such as inverters to maximize value. Recently, many inverters and solutions that match bifacial modules have appeared in the industry. Which solution is the best match for bifacial modules? Based on a large amount of experimental data, this article describes the solution needed for bifacial modules.

Using a prescribed test protocol to compare the measured performance of a solar PV power plant relative to its expected performance is often a means by which the value of the facility is determined. Performance testing is used contractually to determine matters such as the fee paid to a constructor, the price paid to a seller, and the cost of capital from a lender or investor. To ensure that performance testing produces consistent and independently verifiable results, it is essential that accurate and repeatable test methods be used. This paper outlines critical deficiencies in older solar PV performance testing protocols, and how the methods prescribed in ASTM E2848 and E2939 eliminate these deficiencies and enable test practitioners to produce consistent, verifiable results with a high degree of confidence.

As PV systems proliferate and become an important part of the global energy mix, it is increasingly important to forecast their energy output in order to ensure a safe and reliable integration of their variable output into electric power grids. One of the main prerequisites for that is the detailed recording and interpolation of the actual irradiance in a spatially resolved way. Such 2D irradiance maps would also allow the assessment of the performance of the many PV systems that do not have irradiance sensors installed at the site. The maps are ideally based on a dense network of irradiance sensors; however, in many cases the costs of high-precision pyranometers, real-time monitoring and frequent maintenance are prohibitive for such operational forecasting systems. On the other hand, many PV installations are in fact equipped with reference cells in the plane of array (POA) for evaluating and monitoring the performance of the systems. Adding this network of reference cells to existing pyranometer networks (from meteorological services or research institutes) would substantially help in improving the accuracy of the irradiance maps. This paper introduces an irradiance conversion technique that allows POA irradiance measurements from an on-site reference cell to be converted to global horizontal irradiance data, which can then collectively be used to generate large-area irradiance maps.

This paper presents the minimum aspects to consider for the commissioning of large-scale PV plants. This methodology has been successfully implemented in the commissioning of more than 40 PV facilities worldwide and it represents a very useful tool to assure the good performance of the PV project.

The pioneers of utility-scale PV construction have drawn on methods used in other industries to make power plants more efficient and more competitive. This paper investigates how cutting-edge techniques in modularndesign are being used to drive down plant costs. The evolution of modular design and its attractiveness to theinvestor community are discussed.

In PV power systems the choice of an appropriate location for the installation of the PV array box (or DC combiner box) is an important undertaking. It is essential that the box be placed so that the amount of DC cabling is minimized in order to not only save cable costs but also reduce voltage losses. This paper presents a fast solution to this problem, based on a mathematical model for the minisum location of the combiner according to the Manhattan metric between the PV array and the DC combiner box. The target function and its optimal solution (i.e. the most economical amount of cabling) for this particular model were obtained, and the optimality of the solution proved by contradiction. The application of this model is illustrated by means of two typical examples, involving an odd and an even number of strings in a PV array. The proposed model is efficient and easy to apply, and as such should be of interest to PV engineers and designers.

This paper considers the relative technical and economic performance, for selected sites in Southeast Asia, of PV plants using crystalline and thin-film PV module technology. Technical performance estimates are based on a forensic analysis of in-field data for two grid-connected PV installations in Thailand using polycrystalline and thin-film PV modules. These two case studies help to validate the performance simulation approach for the other considered countries with similar environmental conditions. The case studies show that Mott MacDonald’s yield analysis approach demonstrates acceptable accuracy for energy yield assessment in a grid-connected PV plant, at least under the observed environmental conditions, which are most relevant to Southeast Asia plants with polycrystalline and thin-film PV modules installed. The findings presented in this paper are relevant to project developers and investors who have an interest in selecting solar PV technologies for Southeast Asian regional conditions.

Beyond lowering energy costs and demand charges, Superstorm Sandy demonstrated the frailty of centralized power generation. Building owners/operators throughout the Northeast in the USA are evaluating distributed power generation options for supporting building-critical loads during future grid outages. Those options (many of which also incorporate commercial-scale grid storage solutions) include on-site diesel generators, micro-turbines, fuel cells and solar PV systems. As electrical vehicle (EV) charging is added to the mix, the grid requirements and demand costs will further increase. This article will discuss specific value streams for integrating energy storage with PV for commercial buildings, and technologies - specifically, advanced power converters – that will enable those benefits to be achieved.

As the PV capacity of utility systems increases, utility planners and operators are becoming more and more concerned about the potential impacts of power supply variability caused by transient clouds. Utilities and control system operators need to adapt their planning, scheduling and operating strategies to accommodate this variability while at the same time maintaining existing standards of reliability. Effective management of these systems, however, requires a clear understanding of PV output variability and the methods to quantify it. The present objective is to develop analytical methods and tools to quantify PV fleet output variability. This paper presents a method using location-specific inputs for estimating correlation coefficients, and discusses the key findings that resulted from applying the method to three separate geographical regions in the USA. The approach has potential financial benefits for systems that are concerned about PV power output variability, ranging from individual distribution feeders to state-wide balancing regions.