Ecodesign of photovoltaic grid-connected systems
Introduction
Solar Photovoltaic (PV) systems will be a major alternative in coming decades to cope with the scarcity of fossil fuels [1], [2]. The direct conversion technology based on solar PV has several positive attributes. Although hydroelectric, thermal and nuclear power are cheaper in generation, solar PV has an edge over them since it requires almost no maintenance and neither depletes natural resources nor pollutes while in operation [3], [4]. The energy source, our sun, is free and inexhaustible. PV technology is also very robust and has a long life.
The PV grid-connected system (PVGCS) performance depends exclusively upon the availability of solar energy at the site, system elements and configuration, and load parameters. The annual energy generated by a PVGCS is calculated as the sum of hourly production over the entire year. This hourly production depends on many parameters such as PV collector peak power, solar radiation on PV module plane, PV module temperature, shading, inverter efficiency and size, maximum power point tracking losses and the arrangement of the various electrical connections [5], [6], [7], [8].
The size and configuration of a PVGCS are critical for evaluating profitability and environmental performance [9], [10]. The search for an optimal arrangement of collectors in a field, trying to satisfy different objectives, constitutes an important challenge. The optimal deployment is principally based on production [5], [6], [11], [12], [13], [14] or economic [9], [12], [15] criteria. Another criterion that has lately been used to evaluate PVGCS is the environmental impact [3], [16], [17], [18], [19], [20].
As PVGCS is exclusively made with static components generating no particulate matter emission and requiring no fluid maintenance, the only potential impact of PVCGS during operation is related to the environmental impact on flora and fauna arising from change in land use. It can also cause changes in the economic activities. Emissions are generated by the use of fossil fuel-based energy [16], [21], [22] during the manufacture of the components, building and subsequent recycling of the components. This paper deals with this particular issue.
Although different models and tools have been developed to achieve the optimum PVGCS configuration, they are limited to a single objective evaluation, usually based on technical or economic criteria, and in few cases, on environmental criteria.
The goal of this work is to propose a system for generating alternative configurations of PV power plants, taking into account simultaneously three criteria based on technical, economic and environmental aspects, while considering different types of PV solar technologies through an optimization method. In the first part of this paper, the analysis of a literature review reports the different studies and tools that enable the modeling and design of a PVGCS. Secondly, the optimization approach is described in detail. Then, the results obtained after the proposed methodology was tested into single-objective studies are discussed. Finally, the major contribution of this work is highlighted along with some ideas that could be implemented in the future.
Section snippets
Literature review
System modeling forms a key part of the PV system design. It can provide answers to a number of important issues such as the overall array size, orientation and tilt, and the electrical configuration. The design criteria depend generally on the nature of the application. The applications of PVGCS vary from small building integrated systems to PV power plants. Modeling tools are available to provide solar radiation data, assess possible shading effects and produce the resulting electrical layout
PVGCS optimization approach
As explained in the previous section, several programs and mathematical models have been developed to calculate either the solar irradiance received at a given point on the planet or size a PVGCS. Most of the studies reviewed [5], [6], [9], [27], [28], [30] suggest optimizing PVGCS while considering only one criterion. Other authors [17], [19], [20], [31] address only the issue of the environmental impact assessment of the elements of a PV system with emphasis on the PV module technology. Our
Optimization of annual energy output
The example given by Weinstock and Appelbaum [28] (referred as WAP in the following) is used to validate the relevance of the proposed approach. The maximization of annual energy generation by the facility is the objective function. In all cases, the same geographical position (Tel Aviv), the same type of PV module and the available surface are considered. The same limitations as those used for the WAP example are used: minimum space between collector rows (Dmin) equal to 0.80 m, maximum
Conclusions
The goal of the present work was to develop a new approach for generating alternative configurations of PV power plant by adding an environmental assessment to the traditional way of determining the optimum PV power plant configuration. An integrated framework based on a PVGCS sizing simulator involving the computation of solar irradiance coupled to an outer optimization loop was thus designed and tested.
Our approach was applied to the maximization of annual energy generation by the facility as
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