Due to the rapid depletion of fossil fuel reserves and increasing concern for climate change as a result of greenhouse gas effect, every country is looking for ways to develop eco-friendly renewable energy sources. Wind energy has become a good option due to its comparative economic advantages and environment friendly aspects. But there is always an ongoing debate if wind energy is as green as it seems to appear. Wind turbines once installed do not produce any greenhouse gases during operation, but it can and may produce significant emissions during manufacture, transport, installation and disposal stages. To determine the exact amount of emissions, it is necessary to consider all the stages for a wind turbine from manufacture to disposal. Life Cycle Analysis (LCA) is a technique that determines the energy consumption, emission of greenhouse gases and other environmental impacts of a product or system throughout the life cycle stages. The various approaches that have been used in the literature for the LCA of wind turbines have many discrepancies among the results, the main reason(s) being different investigators used different parameters and boundary conditions, and thus comparisons are difficult. In this paper, the influence of different parameters such as turbine size, technology (geared or gearbox less), recycling, medium of transport, different locations, orientation of the blade (horizontal or vertical), blade material, positioning of wind turbine (land, coastal or offshore), etc. on greenhouse gas emissions and embodied energy is studied using the available data from exhaustive search of literature. This provides tools to find better solutions for power production in an environmental friendly manner by selecting a proper blade orientation technique, with suitable blade material, technology, recycling techniques and suitable location.
The increasing demand for energy in the world is not only threatening our environment due to the pollutant emissions from the combustion of fossil fuels (natural gas, oil and coal) but also causing concern for future of energy once we deplete these resources. World population in 2015 is 7.3 billion and expected to rise to 8.4 billion by 2030. The major source of energy in almost all of the countries is still fossil fuel. However, the present reserves of fossil fuel resources cannot be expected to last forever. The total Greenhouse Gas (GHG) emissions globally in 2010 were 54 Gt CO2e [
Life Cycle Analysis (LCA) is a technique used to determine the energy consumption (Embodied Energy), GHG emissions and environmental impacts of a product or system throughout the life cycle stages (cradle to grave) namely, extraction of raw materials, transportation, manufacture, installation and disposal with or without recycling [
Various studies have been done on the LCA of wind turbine considering various parameters. The effects of wind turbine size on embodied energy and GHG emissions were studied by different researchers [
In the literature, different researchers used different parameters, approaches and boundary conditions for the life cycle analysis of wind turbine making it difficult to compare. The main purpose of this paper is to determine the effect of different parameters such as selection of turbine size, technology (geared or gearbox less), recycling, medium of transport, the location of the wind farm, the orientation of the blade (horizontal or vertical), blade material and wind turbine positioning on LCA and embodied energy and GHG emissions.
The main purpose of this paper is to study the effect of different parameters chosen by different researchers for life cycle analysis in order to investigate the effects of those parameter on life cycle analysis, embodied energy and energy emission. It has been observed that for performing life cycle analysis, different researchers have focus on different parameters. Some have compared the embodied energy and environmental emission for increasing turbine size [
As noted earlier, various studies in the literature used various approaches, boundary conditions, life cycle assessment stages and different parameters for the LCA. Thus, there are significant differences in energy embodied in the production, the EPBT and GHG emissions. The various parameters that influence the LCA, energy embodied in the product or system and GHG emissions are discussed in the following sections.
Due to the greater output and increasing efficiencies, there is an increasing trend towards larger wind turbine size (1 MW and above). As can be expected, with the increase in the size of the wind turbine, not only the output increases, but also the required material and embodied energy for manufacturing increases. However, it is necessary to determine whether these increases in wind turbine size and embodied energy provide a net energy saving and lower environmental impact.
The dimensional effects of wind turbines have been studied through LCA by different researchers [
Though different researchers considered different situations, a common result is observed from the life cycle analysis of different sizes of wind turbines that though the embodied energy for large size wind turbines is higher, the net output as expected is higher. As a result, embodied energy per kWh output is lower for large wind turbine. Moreover, the large wind turbines have a greater positive environmental effect compared to smaller wind turbines. In the LCA of Crawford [
Parameters | Quantity | Embodied energy (kJ/kWh) | Energy output (MWh/yr) | Environmental impact (g CO2e/kWh) | Source |
---|---|---|---|---|---|
850 kW | 1 | 154.90 | 9486 | 9.29 | Crawford [ |
3.0 MW | 1 | 140 | 32,915 | 8.40 | |
4.5 MW | 1 | 300 | 11,700 | 15.80 | Tremeac and Meunier [ |
250 W | 1 | 1200 | 2.00 | 46.40 | |
5 kW | 20 | 424.3 | 204 | 17.80 net avoided | Kabir et al. [ |
20 kW | 5 | 221.5 | 196 | 25.10 net avoided | |
100 kW | 1 | 133.3 | 212 | 42.70 net avoided | |
330 kW (100 hub height) | 1 | - | 746 | 33.9633 | Demir and Taskin [ |
500 kW (100 hub height) | 1 | - | 1010 | 29.97 | |
810 kW (100 hub height) | 1 | - | 1670 | 20.41 | |
2050 kW (100 hub height) | 1 | - | 3960 | 16.27 | |
3020 kW (100 hub height) | 1 | - | 3990 | 22.29 |
more evident from the LCA results of Kabir et al. [
In order to determine the effect of using different technologies such as gearbox on material usage, CO2 emission and EPBT, Guezuraga et al. [
The total cumulative energy requirements, annual energy generated, EPBT and environmental emissions expressed as CO2e emissions for the 2.0 MW geared turbine and 1.8 MW gearless turbine are calculated. It is observed that the 2.0 MW geared turbine required little more energy (117.69 kJ/kWh) than the 1.8 MW wind turbine (116.15 kJ/kWh). But the 2.0 MW geared turbine generated 5980 MWh annually, while the 1.8 MW gearless turbine generated 3270 MWh only. The EPBT are 0.65 yr and 0.64 yr for the 2 MW geared turbine and 1.8 MW gearless turbine respectively. However, the 1.8 MW gearless wind turbine has a better environmental value than the 2.0 MW geared turbine in terms of the CO2 emission. The gCO2e/kWh for 2.0 MW geared turbine is 9.73 which is slightly higher than the emissions from the 1.8 MW gearless wind turbine (8.82 g CO2e/kWh). So it is observed that using a gear box increases the output, however, it also increases the energy required and the GHG emissions (
Parameters | Embodied energy (kJ/kWh) | Energy output (MWh/yr) | EPBT yr | Environmental impact (g CO2e/kWh) | Source |
---|---|---|---|---|---|
2.0 MW-geared | 117.69 | 5980 | 0.65 | 9.73 | Guezuraga et al. [ |
1.8 MW-gearless | 116.15 | 3270 | 0.64 | 8.82 |
The recycling of wind turbine materials has a great impact on LCA, required embodied energy, annual output and environmental emissions. The effect of recycling has been studied using LCA by different researchers [
Specifications | Scenarios | Embodied energy (kJ/kWh) | Energy output (MWh/yr) | EPBT yr | Environmental impact | Source |
---|---|---|---|---|---|---|
2 MW wind turbine | Nacelle, rotor, tower | - | 4000 | 0.40 | 2356 pt GWP avoided | Martinez et al. [ |
Nacelle, rotor, tower, foundation | - | 4000 | 0.40 | 2615 pt GWP avoided | ||
2 MW wind turbine | Reduction by half of the recycling | - | - | - | Approximate. 11, 500 point increase | Martinez et al. [ |
2 MW geared turbine | BCRS | - | - | 0.69 | 9.78 g CO2e/kWh | Guezuraga et al. [ |
WCRS | 207.99 | 5980 (2990 h) | 1.15 | 17.35 g CO2e/kWh | ||
WCRS and WCOS | 358.44 | 3470 (1738 h) | 1.99 | 29.48 g CO2e/kWh | ||
Vertical axis | 100% reuse | 0.00927 | 0.539 | - | 6.3079 g CO2e/kWh | Uddin and Kumar [ |
90% reuse | 0.01763 | 5.7514 g CO2e/kWh | ||||
80% reuse | 0.02597 | 5.1948 g CO2e/kWh | ||||
Horizontal axis | 100% reuse | 0.002245 | 1.782 | - | 1.7677 g CO2e/kWh (avoided) | |
90% reuse | 0.0030864 | 1.6554 g CO2e/kWh (avoided) | ||||
80% reuse | 0.0035476 | 1.54320 g CO2e/kWh (avoided) |
The result obtained from the Best Case Recycling Scenario (BCRS) is compared with the Worst Case Recycling Scenario i.e. without recycling (WCRS) and Worst Case Operation Scenario (WCOS) in terms of embodied energy required, annual energy generated, EPBT and environmental emissions. The results obtained are included in
One of the important parameters affecting the LCA is the geographic location of the wind turbine farm, specifically the country. In order to determine the effect of location on the LCA, energy required, annual energy output and environmental emissions (g CO2e/kWh), Guezuraga et al. [
Specifications | Locations | Embodied energy (kJ/kWh) | Energy output (MWh/yr) | EPBT yr | Environmental impact (g CO2e/kWh) | Sources |
---|---|---|---|---|---|---|
2 MW geared turbine | Germany | 207.69 | 5980 | 1.15 | 17.35 | Guezuraga et al. [ |
Denmark | 242.61 | 5980 | 1.35 | 23.26 | ||
China | 424.41 | 5980 | 2.36 | 38.33 | ||
E-40 turbine (inland 65 m height) | P&O in Germany | 730 | 881.972 | - | 7.7 × 10−5 | Lenzen and Wachsmann [ |
P in Germany, O in Brazil | 290 | 2420.131 | - | 2.6 × 10−5 | ||
P Germany & Brazil, O Brazil | 220 | 2420.131 | - | 1.2 × 10−5 | ||
P&O in Brazil | 190 | 2420.131 | - | 4 × 10−6 | ||
P&O in Brazil, recycled steel | 140 | 2420.131 | - | 3 × 10−6 |
P = Production, O = Operated.
is much higher than that of coal, when the wind turbine is produced and operated (P&O) in Brazil, it shows the least energy requirement (140 kJ/kWh) and least CO2 emissions (3 × 10−6 g CO2e/kWh).The wind turbine produced and operated in Germany required the highest energy (730 kJ/kWh) and the highest CO2 emission (7.7 × 10−5 g CO2e/kWh).
In order to determine the effect of transportation on life cycle analysis, Tremeac and Meunier [
Specifications | Impact category | Embodied energy (kJ/kWh) | Climate change (tgCO2e) | Environmental impact (g CO2e/kWh) | Human health (DALY) | PEPBT yr | Source |
---|---|---|---|---|---|---|---|
4.5 MW wind turbine | Reference | 288 | 3691.1 | 15.80 | 5.126 | 0.58 | Tremeac and Meunier [ |
Case A (distance variation) | 360 | 4956.5 | 21.20 | 7.375 | 0.72 | ||
Case B (type of transport variation) | 252 | 2835.5 | 12.10 | 3.347 | 0.51 | ||
250 W | Reference | 1138 | 115.5 | 46.40 | 4 × 10−4 | - | |
Case A (distance variation) | 1332 | 141.2 | 58.80 | 4.30 × 10−4 | - | ||
Case B (type of transport variation) | 1044 | 85.8 | 35.80 | 3.80 × 10−4 | - |
It has been observed that most of the life cycle analysis of the wind turbine is done on the horizontal axis wind turbine as it is the most commonly used turbine. Due to many structural and manufacturing advantages, the horizontal axis wind turbine is becoming more popular. In 2014, Uddin and Kumar [
(18,280.8 kJ/kWh). The electricity generated from the horizontal axis wind turbine and vertical axis wind turbine was studied for over a year. The load factor was considered 35%. It was observed that the energy output of the vertical axis wind turbine is 0.539 MWh/yr and the horizontal axis wind turbine is more than double of that (1.782 MWh/yr). The total emissions and environmental impacts of both the wind turbines were also studied in terms of CO2, SO4 and GWP. It is observed that CO2 and SO4 emissions per functional unit are 0.24 kg and 9.55 gm respectively for the vertical axis wind turbine and 0.08 kg and 3.39 gm respectively for the horizontal axis wind turbine. The GWP is also larger for the vertical axis wind turbine. So considering all the aspects-total energy embodied, energy production and emission etc., it can be decided through the life cycle analysis that the horizontal axis wind turbine provides a far better overall result.
Parameter | Embodied energy (kJ/kWh) | Energy output (MWh/yr) | CO2 Kg | SO4 gm | Environmental impact (g CO2e/kWh) | Source |
---|---|---|---|---|---|---|
Vertical axis wind turbine | 19382 | 0.539 | 0.24 | 9.55 | 5400 | Uddin and Kumar [ |
Horizontal axis wind turbine | 18280.8 | 1.782 | 0.08 | 3.39 | 1800 |
The selection of blade material is an important parameter which can influence energy embodied and greenhouse gas emissions. From the comparison between the horizontal and vertical axis wind turbine discussed in the earlier section, it is observed that the embodied energy and emissions are high for a vertical axis wind turbine. Uddin and Kumar [
So it can be concluded that the blade material can provide a much improved embodied energy and environmental emissions by utilizing newer composites as opposed to aluminum.
Embodied energy (kJ/kWh) | Energy output (MWh/yr) | Environmental impact (g CO2e/kWh) | Source | |
---|---|---|---|---|
Aluminum fan (Base case) | 50 | 0.539 | 12 | Uddin and Kumar [ |
Thermoplastic fan | 30 | 0.539 | 10.5 | |
Fiberglass plastic fan | 25 | 0.539 | 10 |
The position of the wind turbine, whether on-land, coastal or offshore area, has a significant impact on the environment and energy production. The wind turbines on coastal and offshore area generally get higher wind velocity as compared to the ones on the land. So the energy output is higher for them. But the offshore and the coastal wind turbine require special support due to the tides. This may cause higher cost and larger environmental effects.
Various researchers considered the position of the wind turbine as an important parameter in their life cycle analysis [
Specifications | Locations | Embodied energy (kJ/kWh) | Renewable energy | Environmental impact | Source |
---|---|---|---|---|---|
3000 kW wind turbine | Land (85 m) | - | 5001/yr | 195,000 pt | Angelakoglou et al. [ |
Coastal (95 m) | - | 10,989/yr | 301,000 pt | ||
Offshore (105 m) | - | 15,519/yr | 452,000 pt | ||
5 MW wind farm | Offshore | 175.49 | 12,500 MWh/yr | 16.5 g CO2e/kWh | Schleisner [ |
9 MW wind farm | Onshore | 118.08 | 19,800 MWh/yr | 9.7 g CO2e/kWh | |
186 × 1.65 MW | Onshore | - | 1073 × 103 MWh/year | 8.21 g CO2e/kWh | Wang and Sun [ |
100 × 3 MW | Offshore | 1423 × 103 MWh/year | 5.98 g CO2e/kWh | ||
100 × 3 MW | Onshore | 789 × 103 MWh/year | 4.97 g CO2e/kWh | ||
116 × 850 kW | Onshore | 198 × 103 MWh/year | 0.19 - 0.28 g CO2e/kWh |
The purpose of this research was to study the various parameters that influence the life cycle analysis of the wind turbine. It has been observed from the previous results that there are significant differences that arise among the results of life cycle analysis, required embodied energy and environmental emissions due to selecting different parameters and different analysis techniques. It is observed that a significant change of energy embodied, energy generated and greenhouse gas emissions is observed due to change of the analysis process, turbine size, technology (geared or gearbox less), recycling, medium of transport, different location, orientation of the blade (horizontal or vertical), blade material and positioning of the wind turbine. These parameters can be very helpful in making decisions for better power production and better environmental effects.
From the life cycle analysis, it can be concluded that the large scale wind turbines are more energy efficient and more environmentally friendly than the medium scale wind turbine. However, wind turbines that are too large in size may cause an increase in environmental emissions in the manufacturing stage. Again, using different technology such as the geared turbine increases the energy output, but also causes environmental emissions. Recycling of turbine material is a good option to decrease the initial energy requirement and environmental
emissions. It is observed that when recycling different parts of the wind turbine and foundation, a better environmental effect is observed. The location (country) of wind turbines also influences the environmental emissions during the manufacturing and disposal stages as the economy of a country determines the preliminary stage energy requirements. It is observed that by choosing a location which is near to the manufacturing spot and is reachable by river, train or such medium of transport, energy requirement and environmental emissions can be decreased. The energy output and environmental effects can be improved by the choosing proper blade orientation for the wind turbine. The horizontal axis wind turbine gives better energy output and reduced GWP. Lastly, it is observed that the offshore and coastal wind turbines have greater energy output compared to an onshore wind turbine. However, offshore and coastal wind turbines need extra support and additional structural features which will increase the initial cost and environmental emissions.
The results from this life cycle analysis can be used in choosing proper turbine size, technology, recycling technique, transportation medium, suitable location and blade material, more energy efficient and environment friendly designs can be selected.
Nazia Binte Munir,Ziaul Huque,Raghava R. Kommalapati, (2016) Impact of Different Parameters on Life Cycle Analysis, Embodied Energy and Environmental Emissions for Wind Turbine System. Journal of Environmental Protection,07,1005-1015. doi: 10.4236/jep.2016.77089