Environmentally Oriented Analysis of Benefits and Expenditures in the Life Cycle of a Wind Power Plant

The motivation for this study was the need to extend and supplement the previously conducted research on technical objects in the renewable energy sector with analyses of the environmental impact of the production, operation and post-operational development stages of the wind power plant. The main purpose of the work was to investigate, analyze and assess the ecological effects of a real facility, which is a 2 MW Vestas V90/105 m wind farm, throughout its life cycle. The life cycle assessment analysis of the 2 MW wind power plant was performed using Impact 2002+ modeling. The results are presented for all impact levels and categories. The production stage was characterized by the highest total level of harmful effect. The use of recycling reduces the negative impacts of the life cycle by 6.5%. The investigated technical facility has the greatest negative impact during the production stage, especially in the area of depletion of fossil resources and human health.


Introduction
Global energy demand depends on many factors-the most important of them include the pace of the economic development of individual countries, population growth, the evolution of social structures, technical progress in the use of devices and the creation of new technical solutions [1][2][3][4][5]. The modern economy is based primarily on the consumption of goods and services. Commodities necessary for the functioning of society include the electricity, heat, and energy contained in liquid and solid fuels. A significant part of the total energy demand in the world is for electricity, without which it is difficult to imagine the existence of any area of life [6][7][8][9].
The ever-growing demand for electricity forces an increase in its production. The main sources of energy in the world are fossil fuels: coal and lignite, crude oil and natural gas. Unfortunately, the extraction of conventional fuels and the extraction of the energy contained in them is associated with the deterioration of the quality of the natural environment caused by the emission of harmful substances. The biggest problem is the emission of carbon dioxide accompanying the burning of fossil fuels, which, according to many scientists, largely contributes to the deepening of the greenhouse effect and the warming of the climate. According to one source [10], approximately 8 billion tons of CO 2 reach the atmosphere every year, and the amount will increase. Other negative impacts of traditional energy generation include the resulting waste, such as dust, ash, sulfur and nitrogen oxides, as well as heavy metals. Each of the emitted compounds cause the deterioration of the condition of the environment to a greater or lesser extent, and the tangible effects of their adverse impact include the contamination of water and soil, acid rains and climate changes [11][12][13][14][15][16][17].
The main aim of the work is to develop and implement a methodology for researching the ecological expenditure of a wind power plant throughout its life cycle, starting from its production, through its use, to the management of its potentials, including mainly raw materials, plastics and other materials.

Materials and Methods
The durability of wind farms is estimated at about 25 years [31]. The following three stages were adopted for the life cycle of the tested wind farm: design-shaping the resulting idea, use-the main stage of achieving the assumed goals of existence, and post-utility management-ending the life cycle. In the manufacturing process of a wind power plant, the initial idea takes on real material dimensions with the assumed properties. Important for this phase, in the context of environmental impact, is the appropriate organization and selection of optimal production processes characterized by low emissions of pollutants and waste. Usage processes are the main and the most important stage in the life cycle of a wind power plant, as it is then then that the goals for which the plant was built are realized. Power plant utilization covers all processes related to the use of a technical object in accordance with its intended purpose [32][33][34][35][36]. The last stage ending the life cycle of a wind power plant is post-utility management, which for a time was not taken into account as a separate phase in the existence of technical systems. The problems with the generated waste and the related environmental threats contributed to a change in the perception of post-use management issues, which are now considered among those important from the point of view of the rational use of materials, minimizing energy consumption and reducing environmental degradation. This resulted in the recycling of wind turbine components and the re-use of suitable components [34,35,37].
A life cycle assessment was carried out for an onshore, three-blade horizontal axis wind power plant with a capacity of 2 MW located in central Poland. Assessment of the life cycle of the plastics, materials and other components of renewable energy systems is possible thanks to the use of various models, including Life Cycle Assessment. Environmental LCA was chosen as the method of assessing the potential impact of the wind power plant on human health, ecosystem quality and resource depletion. In accordance with ISO 14040 (Environmental management, Life cycle assessment, Principles and framework) and ISO 14044 (Environmental management, Life cycle assessment, Requirements and guidelines) standards, the LCA analysis performed in this work included four stages: determination of the goal and scope, life cycle inventory (LCI), life cycle impact assessment (LCIA) and interpretation [38,39].
The research began with the determination of the goal and scope. Based on the previous analysis of the current state of knowledge and technology, it was found that the literature lacks, in context, a detailed assessment of the life cycle of wind power plants [38,40,41]. The data used in the analysis were obtained from the producers of the renewable energy systems under consideration or were downloaded from the databases of the SimaPro software. The time range of the analysis is twenty-five years. The geographical scope of this research is the area of Europe, because the company that provided the data operates on the entire European market. The cut-off level established for the research was 0.1%. The analysis conducted should be classified as bottom-up and was mainly used to describe the existing situation (retrospective analysis), but also to create more pro-environmental solutions (prospective analysis). The level of advancement of the analysis classifies it among detailed analyses. The functional unit is the productivity of the researched object, which is 5325 MWh/year [38,42].
Based on the previous analysis of the state of knowledge and technology, it was acknowledged that the literature needs a detailed life cycle assessment of a wind power plants with particular attention to budget and to the benefits of their life cycle. It was also considerably important when articulating the goal and scope to accumulate as much and the best possible quality data on the objects of analysis as possible. This was possible thanks to cooperation with a company that produces materials and elements for wind power plants, which has a leading position on the European and domestic market. Due to the conclusion of a data confidentiality agreement with the company producing the RES system analyzed, this study does not disclose all detailed information on the structure of the analyzed subjects and their technological data [38,43,44].
The total weight of the elements and materials of the tested wind power plant is about two thousand tons. The foundations account for the largest share of the mass of the building-roughly 79% (of which roughly 96% is concrete and 4% is steel). Among the other most important elements of the power plant, one can distinguish the tower, contributing roughly 15% of the weight of the entire object (mostly made of steel), the nacelle, with a roughly 4% share (its elements are mostly made of cast iron-roughly 49% of the nacelle weight, steel-roughly 38%, aluminum-roughly 4%, polymer materials-roughly 3% and copper-roughly 2%) and the rotor, with a roughly 2% share (around 50% of this weight is a hub made mainly of nodular cast iron, and the other 50% comes blades made of polymers reinforced with fiberglass) ( Table 1) (data obtained from the manufacturers, the investor and the producers).
In the next step, a detailed analysis of the life cycle of the technical objects under investigation was created. The necessary simulation examination was conducted using SimaPro software and IMPACT 2002+ calculation processing. The acquired results and their rendition are presented in Section 3. The last part of the analysis, including the rendition of the acquired results, is presented in Sections 3-5.
The Impact 2002+ model is a combination of two methods-CML and Eco-indicator 99-and groups similar categories of intermediate points to endpoints. It is primarily used to calculate the maximum negative environmental impact that may occur in the territory of Europe. The spheres of evaluation, the technosphere and the ecosphere influence the results obtained by this model. Importantly, the model functions in the technical space, and the obtained results indicate damage caused in the ecological space.
The model of a wind power plant system as a research object is a representation of the actual and probable states of its environmental functioning. It is created as the result of analyses and studies or is imposed by the modeler.
The object of experimental research in this work was a Vestas V90/105 m wind power plant, operating and connected with its surroundings (environment).

Results
The results of the implementation of this stage for one life cycle of the Vestas V90/105 m wind farm, sorted by their impact categories, are presented in Tables 2-10. The results of the impacts were given in three units characteristic for Impact 2002+ modeling in the LCA method: PDF m 2 /r, DALY and MJ. The cut-off level for all analyses was 0.05%.
The results characterizing the environmental consequences occurring in the life cycle of the Vestas V90/105 m wind farm showed a particularly high level of negative impact during the production stage in the category of inorganic compounds causing respiratory diseases (7.33 DALY), processes related to the extraction of minerals (1,280,000 MJ) and non-renewable energy (2,470,000 MJ). Recycling would make it possible to minimize the harmful impact of the life cycle of the analyzed wind farm in most impact categories, including inorganic compounds causing respiratory diseases (−0.143 DALY), processes related to the extraction of minerals (−31,300 MJ) and non-renewable energy (−374,000 MJ) ( Table 2).   Table 3 Table 4 summarizes the results characterizing the environmental consequences for organic compounds that cause respiratory diseases occurring at individual stages of the Vestas V90 wind farm life cycle. The analyses performed indicate a significantly high level of negative impact for non-methane volatile organic compounds during the production of the tested technical object (0.003 DALY). Methane (7.90 × 10 −5 DALY), ethene (3.74 × 10 −5 DALY), pentane (2.33 × 10 −5 DALY) and butane (1.64 × 10 −5 DALY) also play an important role in shaping the impacts of this category, as to xylene (1.45 × 10 −5 DALY), fossil methane (1.12 × 10 −5 DALY) and propane (1.03 × 10 −5 DALY). In this case, recycling makes it possible to significantly reduce the harmful effects of non-methane volatile organic compounds (−6.42 × 10 −4 DALY) and methane (−3.91 × 10 −5 DALY). A particularly high level of negative impact during the production phase is evident (0.003 DALY). The use of recycling processes will make it possible to reduce the harmful impact of the life cycle of the tested wind farm by −0.001 DALY.
The results of the studies characterizing the environmental consequences for inorganic compounds causing respiratory diseases in the life cycle of the Vestas V90 wind farm are summarized in Table 5. The highest levels of harmful effects in this category for the production stage were produced by sulfur oxide (6.405 DALY), medium level-solid particles < 10 µm (0.439 DALY), nitric oxide (0.39 DALY), sulfur dioxide (0.03 DALY) and solid particles < 2.5 µm (0.026 DALY). The use of recycling will make it possible to reduce the negative impact of the life cycle of the wind processor, especially by reducing emissions of sulfur oxide (−0.066 DALY) and nitrogen oxide (−0.065 DALY). The production stage had the highest level of negative environmental impact (7.33 DALY). The results characterizing the environmental consequences of the ionizing radiation occurring in the various stages of the life cycle of the Vestas V90 wind farm are presented in Table 6. The highest level of harmful effects during the production stage was caused by the radon 222Rn isotope (0.0162 DALY), the carbon isotope 14C (0.0018 DALY) and the isotope cesium 137Cs (0.001 DALY). There is a visibly high level of negative impact for the production stage: 0.0193 DALY. Table 7 presents the results characterizing the environmental consequences for ozone layer depletion occurring in the various stages of the life cycle of the Vestas V90 wind farm. The analyses conducted revealed a significantly high detrimental effect in the production stage, especially for bromotrifluoromethane (0.001 DALY) and 1,2-dichloro-1,1,2,2tetrafluoroethane (0.0001 DALY) in this category of the environmental impacts of the investigated technical object. The highest level of harmful impact occurs during the production stage due to the production of the plastics, materials and wind turbine components (0.0012 DALY). Recycling will make it possible to minimize negative impacts throughout the life cycle in the analyzed category by a total of −0.0001 DALY.   Table 8 presents the results characterizing the environmental consequences for the processes related to land occupation, occurring in the various stages of the life cycle of the Vestas V90 wind farm. The very high level of negative impacts in this category for the production stage was particularly visible, mainly in the form of the use of class II-III land (2.58 × 10 4 PDF m 2 /y), the conversion of land into the area of mineral resource extraction (8.35 × 10 3 PDF m 2 /y), the use of class II-IV land (3.25 × 10 3 PDF m 2 /y), the use of III-IV class land (3.19 × 10 3 PDF m 2 /y) and its transformation into artificial water reservoirs (1.97 × 10 3 PDF m 2 /y). The highest level of harmful impact was recorded for the production process (3.34 × 10 4 PDF m 2 /y), while the levels are significantly lower for the use stage (3.96 × 10 3 PDF m 2 /y) and landfilling (2.92 × 10 3 PDF m 2 /y). The results characterizing the environmental consequences for the processes related to the extraction of minerals occurring in each stage of the life cycle of the Vestas V90 wind farm are presented in Table 9. The analyses conducted showed a particularly high, detrimental effect on the surroundings for the production stage of the technical object, mainly caused by processes related to the extraction of fossil nickel (1.04 × 10 6 MJ), fossil copper (8.31 × 10 4 MJ), and co-combustible bauxites (8.08 × 10 4 MJ)) and fossil chromium (4.95 × 10 4 MJ). The production stage of the plastics, materials and elements of a wind turbine is characterized by the highest negative impact on the environment (1.28 × 10 6 MJ). The choice of recycling as a method of post-consumer management will reduce the total harmful impact of the life cycle by −3.13 × 10 4 MJ. Table 10 presents the results of the studies characterizing the environmental consequences for the processes related to the extraction of non-renewable energy, occurring in the various stages of the life cycle of the Vestas V90 wind farm. The highest level of harmful impacts is characteristic of the processes related to the production of wind turbine components, including the extraction of crude oil, requiring 42.6 MJ/kg of nonrenewable energy (1.3 × 10 6 MJ) and natural gas, requiring 35 MJ/m 3 of non-renewable energy (6.11 × 10 5 MJ). A significantly high level of destructive impact on the environment was recorded for the production stage of the wind turbine (2.47 × 10 6 MJ). Reducing the negative impact of the existence cycle is possible through the use of recycling processes (−3.74 × 10 5 MJ). Figure 1 shows the amount of greenhouse gas emissions in the life cycle of selected elements of the Vestas V90/105 m wind farm. In this case, two options for post-use management were adopted, landfill or recycling, and the structure of the power plant was divided into the same four main parts: nacelle, rotor, tower and foundation. The foundations (2,518,579 kg CO 2eq ) were the highest in the lifecycle of greenhouse gas management in the form of landfill storage. The share of the mobile above-ground part of the power plant (nacelle + rotor) was smaller than that of the fixed part (tower + foundations) in the total negative impact on the surroundings of the entire analyzed power plant and amounted to 22%. On the other hand, assuming that the post-use development of the research object will take the form of recycling, it can be noticed that the greatest amount of GHG is also found in the foundations (1,587,491 kg CO 2eq ). In this case, the share of the mobile part of the above-ground wind turbine is about 1/3 of the total harmful effect of the Vestas V90/105 m life cycle.

Discussion
The aim of the research in this study was to assess the impact of the life cycle of the Vestas V90 wind farm on the environment. The research was performed using the LCA method and the Impact

Discussion
The aim of the research in this study was to assess the impact of the life cycle of the Vestas V90 wind farm on the environment. The research was performed using the LCA method and the Impact 2002+ model by means of the SimaPro 7.1 software (Pré Consultants B.V., Amersfoort, The Netherlands). To analyze the impact of the entire wind farm, various categories of impacts and the values of emissions of harmful compounds into the soil, water and atmosphere were taken into account. The cut-off level for all analyses was 0.05%.
LCA analysis in the field of wind energy initially focused on power plants with a capacity of less than one MW. Schleisner [45] concluded one of the first examinations of a 500 kW turbine, whilst Ardente et al. [46,47] carried out a study on a wind power plant consisting of 11 turbines with a capacity of 660 kW each. There are also studies devoted to local issues: Martínez et al. [48]  , disregarding other negative impacts on the quality of the environment and human health and the depletion of natural resources, which also require detailed analysis, especially from the perspective of the sustainable development of energy systems. Oebels et al. [51] investigated a 1.5 MW power plant and found that the life cycle of its steel tower was the primary reason for its highest greenhouse gas emissions. Kabir et al. [52] examined three models of wind turbines of different power, realizing that the more power a turbine has, the lesser its CO 2 emissions per kWh of generated energy. Chipindula et al. [55] carried out an LCA of offshore and onshore wind power plants with various capacities installed, resulting in the confirmation that an increase of the mentioned capacity translates into a decrease in carbon dioxide emissions per amount of electricity produced. Furthermore, Alsaleh et al. [53] examined a 2 MW turbine, taking into account various periods of the operation of this type of object, resulting in the conclusion that the production stage causes the highest GHG emissions into the atmosphere.
The highest level of harmful impact during the production of the Vestas V90/105 m wind farm was recorded in the categories of inorganic compounds causing respiratory diseases (7.33 DALY), processes related to non-renewable energy (2.47 × 10 6 MJ) and the mining of minerals (1.28 × 10 6 MJ). For the use phase, these were the key categories: non-renewable energy-related processes (2.09 × 10 5 MJ), inorganic compounds causing respiratory diseases (3.38 × 10 −1 DALY) and carcinogens (1.06 × 10 −1 DALY). However, in the case of post-use management in the form of landfill storage, the significant categories included carcinogenic compounds (1.55 DALY). The choice of recycling as a form of management makes it possible to reduce the negative impact of the life cycle of the plant, especially in the area of processes related to the acquisition of non-renewable energy (−3.74 × 10 −5 MJ) and inorganic compounds causing diseases respiratory system (−1.43 × 10 −1 DALY). The production stage was characterized by the highest total level of harmful effects. The use of recycling reduces the negative impacts of the life cycle by 6.5%. The technical facility has the greatest negative impact during the production stage, especially in the areas of the depletion of fossil resources and effects on human health.
The highest level of harmful emissions occurring in each stage of the life cycle of the Vestas V90/105 m wind farm was recorded with regard to the atmospheric environment, which was most influenced by the production stage; a medium level was recorded with regard to the aquatic environment, and the lowest with regard to the soil environment (the most significant influence of the production stage).
The term eco-design is defined as "the integration of environmental aspects into product design and development with the aim of reducing adverse environmental impacts throughout the whole product's life cycle" (ISO, 2011, ISO/TR 14062, 2012) [56]. Materials, elements, work teams and entire technical objects created in this way should be modeled on the life cycle naturally occurring in nature, which is an ideal example of a closed circulation of matter. The environmental aspects that should be analyzed in order to be able to talk about the introduction of eco-designing principles in the life cycle of wind power plants include, for example, issues such as: − use of materials with the lowest possible negative impact on the environment for production, − using fewer resources during the production process, − reduction of the amount of pollution and by-products, − ensuring an adequate service life, − facilitating the re-use of materials, components and/or workgroups, − striving to reduce the impact of post-consumer development on the environment.
As previously indicated, one of the main techniques used in eco-design is Life Cycle Assessment. The LCA studies carried out as part of this study enable the identification of both individual chemical compounds and substances, as well as materials, components, working units or entire stages of the life cycle of wind power plants, characterized by the greatest negative impact on the environment. This identification will make possible the introduction of changes in the subsequent cycles of newly designed wind power plants, in line with the key assumptions of eco-design and sustainable development.

Conclusions
In the light of the analysis of our research results and conclusions, the research goal of the work, which consisted of determining the potentials of environmental influences in the life cycle of the tested working machine, its productivity, expenditures and the environmental impact of the research object, has been achieved.
The main goal of the work was achieved by means of the development and implementation of a methodology for the research and evaluation of ecological expenditure in the life cycle of a wind power plant, starting from its generation, through its use, to the development of its potentials.
The LCA method was used to determine the environmental inputs of the research object, and within its framework the Impact 2002+ procedure was used as a tool for determining the environmental inputs of greenhouse gas emissions.
Among the possible actions to reduce selected inputs, our study suggests: − development and implementation by manufacturers of wind turbines using technology that allows for the replacement of faster-wearing elements, e.g., nacelles and rotors or their parts after the first life cycle, while leaving slower-wearing elements, e.g., foundations and towers, for the second life cycle, as this will allow for the second life cycle to reduce environmental inputs; − use of pro-environmental construction materials; − designing structures that enable easy post-use separation of materials and elements; − minimization of energy consumption, material consumption and emission intensity of production processes, use and post-consumer disposal of materials, materials and elements of a wind power plant; − optimization at the stage of designing the consumption of the materials (mainly steel) used to build wind farms that have the highest environmental impact; − development of comprehensive, pro-environmental standards regarding the method of post-consumer management of plastics, materials and elements of a wind power plant.
Due to significant differences in its impact on the environment depending on the form used (road, rail, sea or air transport) and the distances that must be covered for different locations both in relation to Poland, Europe and the world, the wind turbine transport stage was not included in the study.
In the future, it is planned to extend the conducted research to include other types of wind power plants (including offshore wind power plants) and to conduct LCA analyses of other renewable energy sources.