CO₂ Buyback of Panels for Proposed 3MW system

Engineering 308

Presented to Andrea Alstone, Energy Manager

Facilities Management

Cal Poly Humboldt

Fall 2022

Objectives

Class Objective:

• The goal of this project is to analyze the carbon dioxide costs of a proposed 3MW of new solar photovoltaics at CPH versus its savings compared to our current grid energy.
• Products: A workbook and wiki page.

Individual Objectives:

• The goal of individual students was to create a spreadsheet to compare some aspect of the CO2 savings or costs and convey this information to a specific audience.
• Products: Spreadsheets, memes, and more

Outline

• Embedded CO_2e in our panels
• CO_2e from our grid
• CO_2e offset from our proposed solar production
• Buyback time for the CO_2e in our panels
• Spreadsheet and wiki
• MEMES!
• Appendix (just in case)

A comparative life cycle assessment of silicon PV modules: Impact of module design, manufacturing location and inventory

“This [2021] study closes this research gap by comparing the environmental impacts of sc-Si glass-backsheet and glass-glass modules produced in China, Germany and the European Union (EU), using current inventory data.”

We relied heavily on the findings from this paper to analyze the CO_2e embedded in two different panel types from a few locations

https://doi.org/10.1016/j.solmat.2021.111277

Glass backsheet (G-BS) and glass glass (G-G) modules

https://doi.org/10.1016/j.solmat.2021.111277

LCA system boundaries of the study

https://doi.org/10.1016/j.solmat.2021.111277

Global Warming Potential (GWP) for sc-Si G-BS and G-G modules produced in China,Germany and the EU

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https://doi.org/10.1016/j.solmat.2021.111277

Sankey diagram of embedded CO_2e for the highest (G-BS China and lowest (G-G EU) modules

https://doi.org/10.1016/j.solmat.2021.111277

Embedded CO_2e in panels

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For our 3MW array, the embedded CO_2e:

• G-G EU is 1,389 tons of CO_2e
• G-BS China is 2,679 tons of CO_2e

Conversions:

1000 kW/MW Common knowledge

2.205 lb/kg Engineering toolbox

2000 lb/ton Engineering toolbox

Our gridmix

This is most recent data we found for CPH energy mix.

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https://reports.aashe.org/institutions/humboldt-state-university-ca/report/2020-05-07/OP/energy/OP-6/

CO₂ in our current (2018) gridmix

Monthly energy generation from 3MW array and CO₂ avoided from the grid

Assumptions:

• 3MW Ppv (from RFP)
• 0.343 tons CO₂/MWh (from our grid)
• e_bos=0.9 (average estimate)
• e_shading=0.98 (from client)

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Our findings

Analysis leaves out

• Most embedded CO2e components that are site specific and the same (e.g. getting the panels to Humboldt, site installation, etc.)
• The Time-Of-Use variability CO2e in our gridmix

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Spreadsheet and Wikipage

• Spreadsheet: https://docs.google.com/spreadsheets/d/1WH9XovvbbvYCipAKgsEgWIDC_OD5-B5rI2btIQIv8uc/edit#gid=0
• Appropedia page: https://www.appropedia.org/Engr_308_CPH_3_MW_CO2_comparison

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Artful Works!

Questions?

Appendix

Embedded CO₂ in the sources

https://unece.org/sed/documents/2021/10/reports/life-cycle-assessment-electricity-generation-options

GHG emissions quoted from report

• Results for greenhouse gas (GHG) emissions are reported on Figure 1.
• Coal power shows the highest scores, with a minimum of 751 g CO2 eq./kWh (IGCC, USA) and a maximum of 1095 g CO2 eq./kWh (pulverised coal, China). Equipped with a carbon dioxide capture facility, and accounting for the CO2 storage, this score can fall to 147–469 g CO2 eq./kWh (respectively).
• A natural gas combined cycle plant can emit 403–513 g CO2 eq./kWh from a life cycle perspective, and anywhere between 92 and 220 g CO2 eq./kWh with CCS. Both coal and natural gas models include methane leakage at the extraction and transportation (for gas) phases; nonetheless, direct combustion dominates the lifecycle GHG emissions.
• Nuclear power shows less variability because of the limited regionalisation of the model, with 5.1–6.4 g CO2 eq./ kWh, the fuel chain (“front-end”) contributes most to the overall emissions.
• On the renewable side, hydropower shows the most variability, as emissions are highly site-specific, ranging from 6 to 147 g CO2 eq./kWh. As biogenic emissions from sediments accumulating in reservoirs are mostly excluded, it should be noted that they can be very high in tropical areas.
• Solar technologies generate GHG emissions ranging from 27 to 122 g CO2 eq./kWh for CSP, and 8.0–83 g CO2 eq./ kWh for photovoltaics, for which thin-film technologies are sensibly lower-carbon than silicon-based PV. The higher range of GHG values for CSP is probably never reached in reality as it requires high solar irradiation to be economically viable (a condition that is not satisfied in Japan or Northern Europe, for instance).
• Wind power GHG emissions vary between 7.8 and 16 g CO2 eq./kWh for onshore, and 12 and 23 g CO2 eq./kWh for offshore turbines.

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• Most of renewable technologies’ GHG emissions are embodied in infrastructure (up to 99% for photovoltaics), which suggests high variations in lifecycle impacts due to raw material origin, energy mix used for production, transportation modes at various stages of manufacturing and installation, etc. As impacts are embodied in capital, load factor and expected equipment lifetime are naturally highly influential parameters on the final LCA score, which may significantly decrease if infrastructure is more durable than expected.

https://unece.org/sed/documents/2021/10/reports/life-cycle-assessment-electricity-generation-options

Biomass embedded CO2

• https://www.eia.gov/energyexplained/biomass/biomass-and-the-environment.php

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