Elsevier

Renewable Energy

Volume 64, April 2014, Pages 82-97
Renewable Energy

Ecodesign of photovoltaic grid-connected systems

https://doi.org/10.1016/j.renene.2013.10.027Get rights and content

Highlights

  • An optimization framework for PV grid-connected system design is proposed.

  • It manages simultaneously technical, economic and environmental criteria.

  • The maximization of annual energy generated by the facility is the objective function.

  • The analysis was carried out for different types of solar panel technology.

Abstract

Optimization approaches for PV grid-connected system (PVGCS) have focused on optimizing the technical and economic performances. The main objective of this study is thus to propose an integrated framework that manages simultaneously technical, economic and environmental criteria. Life Cycle Assessment (LCA) is applied for the evaluation of environmental impacts of PVGCS. The proposed framework involves a PVGCS sizing simulator involving the computation of solar irradiance coupled to an outer optimization loop, based on a Genetic Algorithm. The objective is to maximize the annual energy generated by the facility. The analysis was carried out for different types of solar panel technologies: monocrystalline silicon (m-Si), polycrystalline silicon (p-Si), amorphous silicon (a-Si), cadmium telluride (CdTe) and copper indium diselenide (CIS). The environmental impact assessment was achieved by use of the IMPACT 2002+ method embedded in the SimaPro software tool with Ecoinvent database. The other chosen criteria based on technical and economic aspects concern the payback time of investment (PBT) and energy payback time (EPBT).

To select the best option among the five choices under study, a weighted evaluation is performed on all criteria in order to obtain a score for each technology. The technology with the lowest total score is the a-Si technology. A more relevant analysis is then performed taking into account the environmental impacts per kWh produced, as new criteria. In this case, the CIS PV module technology best meets the objectives.

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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