Project Dissertation submitted to Universiti Teknologi PETRONAS Chemical Engineering Program has partially fulfilled the requirement for. I would like to thank all the lecturers of Universiti Teknologi PETRONAS who guided me throughout the entire period of the project.
INTRODUCTION
- Background
- Problem Statement
- Objectives
- Scope of Study
This project aims to perform life cycle assessments (LCA) of solar cells using only the ReCiPe method, as this is the most suitable and best method to assess solar cells. The solar cells are monocrystalline silicon (mono-Si), polycrystalline silicon (poly-Si), amorphous silicon (a-Si) and cadmium telluride (CdTe).
LITERATURE REVIEW
Life Cycle Assessment
Types of Life Cycle Assessment (LCA)
An assessment of the part of a product's life cycle that is from sourcing to the factory door, which is before the product is shipped to the consumer. It is also known as closed-loop production, where the end of product life is the recycling process.
Phases in Life Cycle Assessment
This stage shows the results of the analysis and evaluates all the choices and assumptions made during the course of the analysis. The main elements of the interpretation phase are an evaluation of the results in terms of consistency and completeness, an analysis of the results and the formulation of conclusions and recommendations of the study (Williams, 2009).
Types of Life Cycle Assessment (LCA) Methods
The basic condition has 9 categories of influence, while the non-basic condition has 7 categories of influence (Acero et. al, 2014). This method consists of 14 intermediate impact categories, which are then combined into 4 damage categories, which are human health, ecosystem quality, climate change and resource depletion (Budavari et. al, 2011).
ReCiPe Method Environmental Impact Indicators (Goedkoop et. al, 2009)
To calculate the damage it has on the ecosystem, the characterization factor of the formation will be calculated using Eq. The characterization factor can then be multiplied by the amount of toxins (kg) to find out the severity of the human health damage.
Solar Cell
The single score is assessed in 3 types of perspective: individualistic, hierarchical and egalitarian. A grid-tied photovoltaic (PV) system is a type of energy system that supplies electricity directly to households and businesses using photovoltaic panels or solar panels as an energy source.
Types of Solar Cells
There are several types of solar cells that are commonly used in industrial and residential areas. It is important that the processes are studied as the type of process involved during the manufacturing phase of the solar cell determines the severity of its impact on the environment.
Manufacturing Process of Solar Cells
During the silane gas reaction, dopants such as phosphine and diborane are included in the reaction. In the case of amorphous silicon, this is to create the p-type, n-type region and p-n junction in the cell.
Difference between Current Project from Previous Researches
METHODOLOGY
Research Methodology
An initial investigation into the SimaPro software was conducted to gain a better understanding of the software. The output of the process was first entered by entering the amount and selecting the unit. The emissions and other waste yields from the process were then specified in the software.
The same process was repeated for all 4 types of solar modules and the data was saved in the software. This was done by software as it would generate a weighted total score for all life cycles.
Key Milestone
The life cycle of the Poly-Si solar module has the highest damage to the resource with a value of 0.51, followed by human health with a value of 0.34 and the lowest damage is to the ecosystem with a value of 0.13. The single result of the Poly-Si solar module was evaluated in 3 types of perspective which are individualistic, hierarchical and egalitarian. For hierarchical perspective, the chart shows that the Poly-Si solar module has a score of 288 Pt.
The individual evaluation of the Mono-Si solar module was evaluated in three types of perspective, which are individualistic, hierarchical and egalitarian. For hierarchical perspective, the graph shows that the Mono-Si solar module has a score of 260 Pt.
Gantt Chart
RESULTS AND DISCUSSION
Life Cycle Assessment (LCA) for Cadmium Telluride (CdTe) Solar Module
In the case of electrical installations, it has the greatest impact on the depletion of metals with a value of 0.12 and the smallest impact on the depletion of the ozone layer with a value of 0.00000026. Finally, for the CdTe module subset, it has the largest fossil depletion impact with a value of 0.065 and the smallest ozone depletion impact with a value of 0.0000032. In terms of damage to the source, the electrical installation subassembly has the largest contribution with a value of 0.133, while the inverter has the smallest contribution with a value of 0.032.
For the damage to human health, the electrical installation subassembly has the highest contribution with a value of 0.065 and the inverter has the lowest contribution with a value of 0.016. Finally, for the ecosystem damage, the cadmium telluride module subassembly has the highest contribution with a value of 0.025 and the electrical installation has the lowest contribution with a value of 0.0039.
Life Cycle Assessment (LCA) for Amorphous Silicon (a-Si) Solar Module
For the subassembly of the a-Si module, it has the highest impact on metal depletion with a value of 0.15 and the lowest impact on ozone layer depletion with a value of 0.000012. For damage to human health, mounting on a sloping roof has the highest contribution with a value of 0.12 and inverter has the lowest contribution with a value of 0.016. Finally, for the resource damage, the amorphous silicon module subassembly has the highest contribution with a value of 0.23 and the inverter has the lowest contribution with a value of 0.032.
For hierarchical perspective, the graph shows that the life cycle of amorphous silicon (a-Si) solar module has a score of 269 Pt. The score for damage to human health is 974.5 Pt, damage to the ecosystem has a score of 99.1 Pt and damage to resources has a score of 110.7 Pt.
Life Cycle Assessment (LCA) for Poly-Crystalline Silicon (Poly-Si) Solar Module
For the subassembly of Poly-Si modules, this has the highest impact on fossil depletion with a value of 0.2 and the lowest impact on the formation of petrochemical oxidants with a value of 0.000015. For damage to human health, the Poly-Si module subassembly has the highest contribution with a value of 0.20 and the inverter has the lowest contribution with a value of 0.016. For damage to the ecosystem, the Poly-Si module has the highest contribution with a value of 0.1 and the electrical installation has the lowest contribution with a value of 0.004.
Finally, for the damage to resources, Poly-Si module sub-assembly has the highest contribution with a value of 0.27 and the inverter has the lowest contribution with a value of 0.032. The figure shows that the Poly-Si module sub-assembly has the highest damage score and the inverter sub-assembly has the lowest damage score.
Life Cycle Assessment (LCA) for Mono-Crystalline (Mono-Si) Solar Module
The inventory for the pitched roof mount required for a 1 kW mono-Si module is in Table 22. The life cycle of Mono-Si solar module has the highest damage to resource with a value of 0.44, followed by human health with ' a value of 0.32 and the lowest damage is towards the ecosystem with a value of 0.11. For damage to human health, Mono-Si module subassembly has the highest contribution with a value of 0.18 and inverter has the lowest contribution with a value of 0.016.
For damage to the ecosystem, the largest contribution is the Mono-Si module with a value of 0.078 and the lowest is the electrical installation with a value of 0.004. Finally, for resource damage, the Mono-Si module sub-assembly has the highest contribution with a value of 0.22 and the inverter with the lowest contribution with a value of 0.032.
Results Summary
CdTe solar module has the highest damage to resource with a value of 0.303, followed by human health with a value of 0.188 and the lowest damage is towards the ecosystem with a value of 0.053. For a-Si solar module, it has the highest damage to resource with a value of 0.55 followed by human health with a value of 0.31 and the lowest damage is towards the ecosystem with a value of 0.09. For Poly-Si solar module, it has the highest damage to resource with a value of 0.51, followed by human health with a value of 0.34 and the lowest damage is towards the ecosystem with a value of 0.13.
For CdTe solar module, it had a score of 157 Pt for hierarchical perspective, score of 159.2 Pt for individualistic perspective and 794 Pt for egalitarian perspective. 260 Pt for hierarchical perspective, score of 262 Pt for individualistic perspective and 1068 Pt for egalitarian perspective.
Comparison of Results and Interpretation
However, it can be seen that CdTe solar module has the lowest contribution to the impact indicators compared to the other solar modules. This indicates that CdTe solar module has the least impact on the environment compared to Poly-Si, Mono-Si and a-Si. Poly-Si has a high release of metals and gases to the atmosphere which increases the damage of the solar module to human health.
This makes Poly-Si the least environmentally friendly solar module based on the hierarchical perspective. On the other hand, CdTe has the lowest score compared to other solar modules, making it the most environmentally friendly solar module based on hierarchical perspective.
CONCLUSION AND RECOMMENDATIONS
Although the CdTe solar panels are more environmentally friendly and cheaper, crystalline silicon solar modules are still the most popular type of solar modules used in the industrial and domestic sectors. The reason for this is that crystalline silicon solar modules have higher efficiency compared to thin-film solar panels such as CdTe. This means that crystalline silicon solar modules, such as Mono-Si and Poly-Si, produce more power per unit area compared to CdTe solar panels, making it more preferable for power-generating industries and domestic users.
For future recommendations, photovoltaic companies should try to increase the efficiency of power generation with CdTe to make it more attractive to consumers, since CdTe is cheaper and more environmentally friendly. In addition, it is recommended that the results of this research be used to prepare new innovations, such as the implementation of CdTe solar module on solar cars, which would promote the development of green technology.
A life cycle impact assessment method that includes indicators of harmonized categories at intermediate and final levels.
