Industrial Data-Based Life Cycle Assessment of Architecturally Integrated Glass-Glass Photovoltaics
Abstract
:1. Introduction
1.1. Building Integrated Photovoltaics
1.2. Life Cycle Assessment
- Goal and scope: Definition of the System boundary & functional unit.
- Life Cycle Inventory (LCI): Elaboration of a mass balance for a process with all inputs and outputs.
- Life Cycle Impact Assessment (LCIA): Assessment of environmental consequences of the LCI such as climate change, natural resource depletion, ozone depletion, ecotoxicity etc. with specific indicators. A sensitivity analysis considers the individual effects of the choices made, i.e., flows and indicators.
- Interpretation: Identification of processes and flows with main environmental impact and recommendation of measures for improvement.
- Place the factors into a system boundary. For example, Jayathissa [20] estimated the energy load (heating, cooling, and lighting energy) in an office with windows fitted with dynamic BIPV, static shading, and no shading at all. The study compares the environmental impact of the German grid electricity to that generated by different BIPV technologies (thin film and crystalline), and the resulting reduction in energy loads. These results are further discussed in the context of this study in Section 3.5.
- Alternatively, these factors can be excluded from a system boundary along with building materials serving a similar purpose, (e.g., when replaced by BIPV in a façade). For example, Ng [21] estimated the lifetime performance of semi-transparent BIPV glazing when it replaces double glazing windows, which similarly impacts building energy performance.
1.3. Purpose of the Study
2. Methodology
2.1. PV Laminate Specifications for Life Cycle Assessment
2.2. Goal and Scope of Life Cycle Assessment
- up-to-date crystalline silicon cell production
- clear and multi-coloured glass production by a specific manufacturer
- glass-glass laminate production with various configurations by a specific manufacturer
- a hypothetical but realistic PV façade installation
- electricity generated from the façade facing south, east/west, and north
- and a comparison of the generated electricity to that of the Swiss low voltage electricity grid.
2.3. Life Cycle Inventory
2.3.1. LCI of Crystalline Silicon Cells
2.3.2. LCI of Solar Glass
2.3.3. LCI of PV Laminate
2.3.4. LCI of Further Processes and Components
2.4. Life Cycle Impact Indicators Selected for This Study
3. Results
3.1. Production of Multi-Coloured and Clear Glass
3.2. Production of Crystalline Silicon Cells
3.3. Production of PV Laminate
3.4. Installation of an Architecturally Integrated Photovoltaic Façade
3.5. Electricity Generation Based on Façade Orientation
- Increase electricity production by 3% (for example, by improving c-Si cell efficiency)
- Reduce impact during façade installation by 3% (for example, mounting system with lower eco-points)
- Reduce impact during lamination processes by 4% (0.04 × 0.6 = 2.4%, since 140 laminates contribute 60% of the total eco-points) (for example, reducing electricity consumption)
- Decrease solar glass impact by 20% (0.2 × 0.09 = 1.8%, since glass contributes 9% to the total) (for example, reducing loss and breakage)
- The north facing façade has the 2–5-fold GWP of the reference, and is unsuitable in any configuration. The worst-case GWP is infact comparable to that of coal power plants. The best-case GWP is, on the other hand, comparable to that of gas power plants.
- S-Si cells (with an efficiency of 17% in this study) are unsuitable under all conditions. They produce 13% more electricity than m-Si, but their GWP is also 54% higher. (see Table A1).
- Multi-coloured PV systems are superior to the Swiss low voltage electricity grid only when the laminates replace part of an existing rain cladding system. In this case, the GWP decreases by 36%: Solar glass (13%); the mounting system (19%); glass take-back and transportation (4%); and printing (0.4%).
- Clear glass m-Si photovoltaic on south facing façade is superior to the reference even when all the environmental impact is allocated to it.
- Different datasets (Ecoinvent 3.1 vs. 3.4)
- Lifespans of 20 years instead of 30 in this work.
- Annual yield of 855 kWh/m (irradiation) × 0.11 (efficiency) ≈ 94 kWh/m vs. annual yield of 700 kWh (facing south) × 24.6 kWp/252 m 68 kWh/m.
- EPBT m-Si: The EBPT of a PV façade facing south with clear and coloured glass is 6 and 8 years, respectively. Facing east/west, this increases to 8 and 11 years, respectively, while facing north, the EBPT exceeds 20 years.
- EPBT s-Si: The EBPT of a PV façade facing south with clear and coloured glass is 8.4 and 10.6 years, respectively. Facing east/west, this increases to 11.2 and 14 years, respectively, while facing north, the invested energy does not pay off at all.
4. Conclusions
Supplementary Materials
Author Contributions
Funding
Acknowledgments
Conflicts of Interest
Appendix A. BIPV Façade Results
m-Si | m-Si | s-Si | s-Si | |
---|---|---|---|---|
Clear Glass | Multi-Coloured | Clear Glass | Multi-Coloured | |
Capacity [kWp] | ||||
Laminate | 0.22 | 0.176 | 0.25 | 0.2 |
System | 30.8 | 24.64 | 35 | 28 |
Lifetime electricity generation [kWh] | ||||
South (700 kWh/kWp) | 582,054 | 465,643 | 661,425 | 529,140 |
East/West (530 kWh/kWp) | 440,698 | 352,559 | 500,793 | 400,635 |
North (200 kWh/kWp) | 166,301 | 133,041 | 188,979 | 151,138 |
Environmental Impact of all system components | ||||
GWP [kg CO eq] | 66,503 | 66,620 | 102,758 | 102,876 |
UBP [kPt] | 110,062 | 110,202 | 140,926 | 141,065 |
CED [MJ] | 899,456 | 901,865 | 1,353,856 | 1,356,286 |
Environmental impact for rain cladding replacement (without glass, mounting system and transport) | ||||
GWP [kg CO eq] | 41,965 | 41,965 | 78,221 | 78,221 |
UBP [kPt] | 83,634 | 83,634 | 114,497 | 114,497 |
CED [MJ] | 599,128 | 599,128 | 1,053,533 | 1,053,533 |
GWP [kg CO eq/kWh (%)] for all components vs. reference (0.123 kg CO eq) | ||||
South | 0.114 (−7.1%) | 0.143 (16%) | 0.155 (26%) | 0.194 (58%) |
East/West | 0.151 (23%) | 0.189 (54%) | 0.205 (67%) | 0.257 (109%) |
North | 0.399 (225%) | 0.501 (307%) | 0.544 (342%) | 0.681 (453%) |
Eco-points [kPt/kWh (%)] for all components vs. reference (0.256 kPt) | ||||
South | 0.189 (−26%) | 0.237 (−7.7%) | 0.213 (−17%) | 0.267 (4.0%) |
East/West | 0.250 (−2.6%) | 0.313 (22%) | 0.281 (9.8%) | 0.352 (37%) |
North | 0.662 (158%) | 0.828 (223%) | 0.746 (191%) | 0.933 (264%) |
GWP [kg CO eq/kWh (%)] for rain cladding replacement vs. reference | ||||
South | 0.072 (−41%) | 0.090 (−27%) | 0.134 (9.3%) | 0.148 (20%) |
East/West | 0.095 (−23%) | 0.119 (−3.2%) | 0.178 (44%) | 0.195 (59%) |
North | 0.252 (105%) | 0.315 (157%) | 0.470 (283%) | 0.517 (321%) |
Eco-points [kPt/kWh (%)] for rain cladding replacement vs. reference | ||||
South | 0.144 (−44%) | 0.180 (−30%) | 0.197 (−23%) | 0.216 (−16%) |
East/West | 0.190 (−26%) | 0.237 (−7.4%) | 0.260 (1.4%) | 0.286 (12%) |
North | 0.503 (96%) | 0.629 (145%) | 0.689 (169%) | 0.758 (196%) |
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Term | Definition |
---|---|
AC | Alternate current |
BIPV | Building integrated photovoltaics |
BOS | Balance of system |
CED | Cumulative energy demand |
c-Si | Crystalline silicon cell |
EPBT | Energy pay-back time |
EVA | Ethylene-vinyl acetate |
GWP | Global warming potential |
ISO | International Organization for Standardisation |
IPCC | Intergovernmental Panel of Climate Change |
LCA | Life cycle assessment |
LCI | Life cycle inventory |
MCGG | Multi coloured glass-glass |
m-Si | Multi crystalline silicon cell |
PV | Photovoltaics |
s-Si | Single crystalline silicon cell |
Parameter | Basic Configuration | Variants |
---|---|---|
Dimension of PV laminate | 1.00 m × 1.615 m | |
Weight of PV laminate | 35.47 kg | |
Glass thickness | 4 mm × 2 = 8 mm | |
Glass weight | 16.15 kg × 2 = 32.3 kg | |
Glass type | multi-coloured (80% performance) | clear glass |
Type of cells | 60 m-Si cells (220 Wp) | 60 s-Si cells (250 Wp) |
Thickness of cell | 0.2 mm | |
Wiring technology for cells | 3 busbar tap wirings | 36 active(smart) wirings [10] |
Parameter | Basic Configuration | Variants |
---|---|---|
PV type | m-Si (15% efficiency) multi-coloured | s-Si (17% efficiency) |
Laminate capacity (System capacity) | 176 Wp (24.6 kWp) | m-Si clear glass: 220 Wp (30.8 kWP) s-Si clear glass 250 Wp (35 kWp) s-Si coloured glass 200 Wp (28 kWP) |
Number of laminates | 140 | |
Laminates used over lifetime | 144.23 (1% rejected in construction of façade, 2% replaced due to early end of life) | |
Façade dimension | 21 m × 12 m = 252 m | |
Projected lifetime | 30 years | |
Annual yield/kWp installed before degradation according to façade orientation | Facing south: 700 kWh/kWp Facing east/west: 530 kWh/kWp Facing north: 200 kWh/kWp | |
Degradation of PV | 0.69 % per year from the first year, total 20 % for 30 years | |
Lifetime yield according to façade orientation | Facing south: 582 MWh Facing east/west: 440 MWh Facing north:166 MWh |
Processes and Components | Remark, Source/Reference |
---|---|
30 kWp inverter | LCA of low power solar inverters (2.5 to 20 kW) [31] |
Mounting and electric system | Ecoinvent 3.4 [25] |
Installation | Transportation and electricity for mounting, Ecoinvent 3.4 |
Cleaning and maintenance | Water consumption and waste water treatment, Ecoinvent 3.4 |
Take-back & recycling of laminate with one glass sheet | Energy consumption for shredding was adapted to the higher glass quantity in a glass-glass laminate. It is assumed the quality of the glass cullet is too low for recycling in float glass production [32]. |
Name | Unit | Remark |
---|---|---|
Global warming potential (GWP) | Grams CO-equivalents [g CO eq] | Contains Intergovernmental Panel of Climate Change (IPCC) climate change factors for a timespan of 100 years [33] |
Cumulative energy demand (CED) | MJ-equivalents [MJ eq] | Contains the energy content of renewable and non-renewable primary energy [23]. In this study, only non-renewable primary energy is considered. |
Ecological Scarcity 2013 | Eco-points [EP] | Eco-points reflect both the actual emission situation and the national or international emission targets pursued by Switzerland [34]. |
Energy Payback Time (EBPT) | Years | Time required to generated enough electricity, so that Non-renewable CED/kWh becomes the same as one of the reference electricity [23]. Refers to the efficiency of the Swiss low voltage electricity grid at the consumer end (9.43 MJ/kWh acc. to Ecoinvent 3.4) |
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Park, J.; Hengevoss, D.; Wittkopf, S. Industrial Data-Based Life Cycle Assessment of Architecturally Integrated Glass-Glass Photovoltaics. Buildings 2019, 9, 8. https://doi.org/10.3390/buildings9010008
Park J, Hengevoss D, Wittkopf S. Industrial Data-Based Life Cycle Assessment of Architecturally Integrated Glass-Glass Photovoltaics. Buildings. 2019; 9(1):8. https://doi.org/10.3390/buildings9010008
Chicago/Turabian StylePark, Jeeyoung, Dirk Hengevoss, and Stephen Wittkopf. 2019. "Industrial Data-Based Life Cycle Assessment of Architecturally Integrated Glass-Glass Photovoltaics" Buildings 9, no. 1: 8. https://doi.org/10.3390/buildings9010008