Life Cycle Assessment of Electricity Production from Airborne Wind Energy

119 Pages·2015·5.22 MB·English

by  Stefan Wilhelm

Life Cycle Assessment
of Electricity Production
from Airborne Wind Energy
II
by

Stefan Wilhelm

MASTER OF SCIENCE THESIS

at Institute of Environmental Technology and Energy Economics
University of Technology Hamburg

03.08.2015

Examiner: Priv.-Doz. Dr. W. Ahlf
Co-examiner: Prof. Dr.-Ing. G. Schmitz

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STATUTORY DECLARATION
I declare that I have authored this thesis independently, that I have not used other than the declared
sources and means. The thesis has not been submitted to any other examining body and has not been
published.

Hamburg, 03 August 2015
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Global energy supply is closely linked with some of the greatest challenges of our society. A rising demand
has to be met whereas conventional energy sources are depleting and emit considerable amounts of
greenhouse gases. Renewable energy technologies are increasingly promoted to face these issues,
especially in the electricity industry. Research has shown, that renewables are superior to conventional
energy technologies in many environmental aspects but are not free of burdens. However, the main causes
of impacts are shifted to other life cycle phases than operation. The emerging of airborne wind energy
(AWE), as a new stakeholder within the renewables, presents an ecologically promising option since it
accesses wind resources of outstanding quality with little material consumption. As of now, there is no
environmental assessment of this new technology available.
The goals of this study are (1) the determination of environmental burden of electricity generation with
AWE on the categories global warming and consumption of energy resources, (2) the identification of main
contributors to these categories, (3) the determination of the energy payback time and (4) an assessment
whether use of this technology would lower impact of electricity supply in the mentioned categories. An
AWE design is chosen for the investigations, which appears possible to become a dominating design. Even
though uncertainties arise from the analysis of a specific design, the outcomes of the study could serve as
a first reference for system developers and for decision-makers to evaluate support or engagement in this
technology.
To this end, a life cycle assessment (LCA) was executed, which allows tracking of category indicators from
cradle to grave. Specific AWE facilities of 1.8 MW were defined and analyzed in a 300 MW plant under low
wind conditions. The modeling follows an estimated dominating design or conservative choices. The
results are expected to be on the upper range. The results of the model are presented and discussed and
checked for robustness in a sensitivity study. A comparison to a similar conventional wind power plant and
the electricity grid mix allows a better classification of the results.
The category indicator result in global warming potential (GWP) is 5.611 g /kWh. 65 % of that occur
CO2-eq.
in the phase raw material and manufacturing, 3 % during installation, 28 % during operation and 4 % in
disposal. The cumulated energy demand (CED) is 75.2 kJ-eq./kWh. The invested energy during the entire
life cycle is 2.1 % of the total generated electricity and is recovered after 5 months or 153 days of operation.
This corresponds with an energy yield ratio of 48%. The tether accounts for 5.5 and 8.1 % in GWP and CED,
including its replacements. Lower lifetimes have significant influence, higher are with marginal effect. The
environmental effects from the wing manufacture arise by 75% from the carbon fiber reinforced polymer
but are only 2.6 and 5.6 % in GWP and CED. The biggest contribution is from generator and gearbox, which
account for 35 and 30 % in GWP and CED respectively, including replacement of all gearboxes. In total,
30 % of the impacts come from balance of station components and 70 % from the AWE facility. The latter
is the percentage that the system developer can influence directly.
Compared to a conventional wind plant that was modeled in a similar way, the AWE plant consumed 23 %
of the mass, causes 49 % of the GWP and consumes 55 % of the CED. Energy payback time was 2 times
lower. Compared to German electricity mix the plant causes 0.87 % of the GWP and has 0.74 % of the CED.
Even with a conservative approach the study confirms the expectation of low impact in the considered
categories and presents first numerical results.

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Abstract ........................................................................................................................................... VII
Table of contents .............................................................................................................................. IX
List of figures ..................................................................................................................................... XI
List of tables .................................................................................................................................... XIV
Abbreviations ...................................................................................................................................XV
1 Introduction................................................................................................................................ 1
2 Related background .................................................................................................................... 3
2.1 Atmospheric research ................................................................................................................... 3
2.2 Airborne Wind Energy ................................................................................................................... 6
2.2.1 Motivation for AWE ............................................................................................................... 7
2.2.2 Implemented concepts .......................................................................................................... 7
2.2.3 Technology status .................................................................................................................. 9
2.3 Components and Manufacturing ................................................................................................ 11
2.3.1 Wind Capturing components .............................................................................................. 12
2.3.2 System Control Components ............................................................................................... 14
2.3.3 Structural Components ....................................................................................................... 15
2.3.4 Mechanical power conversion components ....................................................................... 17
2.3.5 Electrical power conversion components ........................................................................... 17
2.3.6 Various additional ................................................................................................................ 18
2.4 Life cycle assessment................................................................................................................... 18
2.4.1 General aspects and principles ............................................................................................ 18
2.4.2 Stages of a LCA .................................................................................................................... 19
2.4.3 Auxiliary tools ...................................................................................................................... 25
2.5 LCA in wind power ....................................................................................................................... 26
3 Goal and scope definition .......................................................................................................... 30
3.1 Goal of the study ......................................................................................................................... 30
3.2 Scope of the study ....................................................................................................................... 31
3.2.1 Function and functional unit ............................................................................................... 31
3.2.2 System boundaries .............................................................................................................. 31
3.2.3 Product system: AWE plant ................................................................................................. 32
3.2.4 Energy yield estimation ....................................................................................................... 34
3.2.5 Impact categories ................................................................................................................ 35
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3.2.6 Data requirements, collection, quality, constraints and allocation .................................... 36
3.2.7 Assumptions ........................................................................................................................ 38
4 Life Cycle Inventory analysis ...................................................................................................... 39
4.1 Raw material and manufacturing ................................................................................................ 39
4.2 Wing system ................................................................................................................................ 40
4.3 Tethering ..................................................................................................................................... 42
4.4 Ground station ............................................................................................................................ 44
4.5 Launch and landing system ......................................................................................................... 47
4.6 Balance-of-station ....................................................................................................................... 47
4.7 Installation ................................................................................................................................... 49
4.8 Operation and maintenance ....................................................................................................... 50
4.9 Decommissioning and disposal ................................................................................................... 51
4.10 Conventional wind turbine .......................................................................................................... 52
5 Results and discussion ............................................................................................................... 54
5.1 Baseline results for the AWE plant .............................................................................................. 54
5.1.1 Material consumption ......................................................................................................... 56
5.1.2 CED and energy payback time ............................................................................................. 57
5.1.3 GWP and analysis of category indicator results .................................................................. 57
5.1.4 Correlations between categories and mass ........................................................................ 63
5.2 Sensitivity study ........................................................................................................................... 64
5.3 Comparison to conventional wind power and validation ........................................................... 68
5.4 Comparison to other energies ..................................................................................................... 72
5.5 Uncertainties and limitations ...................................................................................................... 72
6 Conclusions and further research .............................................................................................. 75
6.1 Conclusions .................................................................................................................................. 75
6.2 Further research .......................................................................................................................... 77
References ....................................................................................................................................... 79
Appendix ............................................................................................................................................ i

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