We cause most (85%) of CO2 emissions because we do not use appropriate technologies, and half of that comes from coal and gas-fired power plants alone. See a previous blog for further details. Renewable energy is on its way to replace fossil fuels. In this and the next blog article we ask the question: Are renewable energies really sustainable?
Let’s take a closer look first at solar cells (photovoltaics, PV) and in the next blog at wind turbines.
Example of an existing PV plant
This photo shows a typical PV plant [1], about 600 km west of Beijing in Inner Mongolia, built on grassland extensively farmed with goats and sheep (coordinates: N 40°42′26″, E 110°27′19″):
If you don’t know how a PV plant works, here is a simple explanation. Electric current normally is made of electrons flowing in metal wires. Solar cells are electronic devices where the electrons capture the energy of the sunlight and are immediately conducted into the wires. You cannot see the solar cells in this picture. Instead, you can see the modules (also called panels) where many solar cells are arranged side by side under a pane of glass to protect them from the weather. These modules are either mounted on steel frames (racks) next to each other in long rows, as you see here, or on roofs. The electric current is collected via wires running along the rows of modules and then fed into the public grid (via so-called inverters and a transformer station).
None of this causes emissions, and the installed structures disturb the land very little when adapted to local conditions and agricultural use – so the main environmental impacts of PV come from the mining of the necessary materials, besides the use of coal-fired electricity for cell and module production, and the use of petrol in the construction of the plants. The following quantities of materials were used for this PV plant [1]:
The horizontal axis at the bottom shows the materials in tonnes: almost 1500 tonnes of steel for mounting the modules, 800 tonnes of flat glass, and almost 200 tonnes of copper cable, 300 km long, running along the long rows from module to module and connecting the plant the nearest high-voltage line. However, this power plant has a (slowly decreasing) performance guarantee for 30 years and will continue to produce electricity after that [2], with more and more modules being replaced over time, the glass being reused and the basic structures being able to be used for longer than 100 years.
Sophisticated modelling predicts [3] that running the entire planet on 100% renewables will require at least 20 terawatts (TW) of PV installations, alongside wind energy and other energies and, of course, storage. Tera means 1012 or “thousand times giga”, and currently about 1 TW is installed. Up to 60 TW will need to be installed if wealthy countries do not want to have at least 1% of their land area covered by PV [4]–[6] and will import hydrogen, which requires about three times more PV electricity than direct PV electricity & storage. So, let’s assume that 40 TW will be installed. The PV system considered here has a capacity of 30 megawatts (MW), so that about 1.4 Million such systems would be required worldwide if no rooftop PV systems [7] were installed. These resulting material quantities are of course large and do not tell us much. Let us therefore compare these total quantities of materials with the amount mined worldwide each year [8]:
32 years of global silver production would be required, although silver is only used in milligram quantities per cell and its contribution is barely visible in the first graph. This is far too much [9]. The PV industry is aware of this, and silver can be replaced by copper or aluminium. The technology required for this replacement has been developed [10] but has not yet been widely deployed because the price of silver is still so low that switching to more complicated copper and aluminium deposition is not economically competitive.
This points to a general problem of sustainability: scarce elements are exploited until they are almost exhausted because only then do they become too expensive. A possible remedy would be mining rights issued by the UN, which are sold at a higher price for each metal the fewer reserves are left, and the profit is used to subsidise recycling.
The next material is glass made for PV. It must be highly transparent and also tempered to withstand hailstorms. Its production can be expanded because it is produced in much smaller quantities than window and bottle glass [11] and it is made from abundant raw materials, for example from sand mining.
Similarly with silicon: PV consumes more high-purity silicon than the electronics industry and has its own supply chain that it can expand because silicon is the second most abundant element on earth and, similar to glass, is extracted by mining of quartz deposits and sometimes of sand [12][13][14]. Most silicon is produced in impure form for steel production and other applications. The amount purified for PV and electronics is relatively small. Even if all global electricity were generated exclusively by PV by 2030, growth rates in the production of non-pure silicon would fall into historical range [15].
Finally, the amount of copper needed is also high, about 6 years of current world production. It is the only material for silicon PV that requires significantly more mining, as copper is also used for power grids, electric vehicles and wind energy (see below). All other materials do not pose a supply problem.
Please bear in mind that these material estimates are based on a typical today’s example, without considering technological improvements in the years to come. I think it is interesting to look at the impact of today’s technology. It shows that current technology is feasible and that it is not necessary to wait for technological breakthroughs.
CO2 emissions caused by PV
After these material requirements, we should consider the CO2 emissions caused by the production and construction of the said PV plant [1]:
Most of the CO2 emissions come from coal-fired power generation and some from the use of petrol trucks. In this PV plant, the silicon was produced with hydropower; if pure coal power were used, the CO2 emissions in the top bar of the graph would double [16]. All these emissions are being continuously reduced to zero in the course of the energy and transport transition [17]. Only a small part is caused by “direct emissions”, where CO2 is released by chemical reactions in cement and silicon production and cannot be avoided by renewable electricity.
To power the entire planet with 100% renewable energy, the CO2 emissions from manufacturing and building all 40 TW of PV systems with today’s technology will sum up to about 10 gigatonnes (Gt), compared to about 43 Gt emitted globally this year alone (see this previous blog). This means that the global deployment of PV will cause only about 3% of the remaining CO2 budget [18] to meet the Paris Agreement’s warming target of 1.5 degrees Celsius. I call that pure luck. Scientists and engineers reduced PV’s CO2 emissions significantly over recent years:
Just 20 years ago, global PV deployment would have caused more than a quarter of the remaining CO2 budget… What could we do about global warming if scientists and engineers had not brought CO2 emissions of PV down?
By the way, the said PV system “earned back” all the energy, spent on its production and construction, within the first 20 months of its operation [1].
More sustainability issues
We should keep in mind that sustainability is more than avoiding the depletion of raw materials and limiting emissions. That said, resource footprints are generally well representative of the damage that is also done to human health and biodiversity [19]–[21]. In any case, other important aspects are the way in which the PV plant is recycled and the environmental and social damage it causes, for example through mining.
The EU required the PV industry to be recyclable from the beginning of mass deployment [21]. All parts of the PV systems and modules can be dismantled mechanically [23], [24]. For example, the silver fingers on the cells by scraping them off. So even if the PV industry continues to use silver, the silver will not be “locked in” at low concentrations and make recycling difficult, contrary to what we saw in a previous blog about materials for the lighting industry. The glass of the modules and some other parts will be reused and there will be no landfill for hazardous waste [25] [26]. However, the PV industry still has room to facilitate recycling and to optimise design for reuse.
To quantify the environmental impact, “life cycle analysis” studies are often carried out. I will explain this type of analysis in an upcoming blog on batteries. Such studies consistently show that the environmental impact of PV is small [24], [27], [28]. However, the life cycle studies show this in rather abstract parameters such as “acidification”, “eutrophication” and “ecotoxicity”. To give you a better grasp, let’s look at a concrete example instead of such parameters:
Coal mining is often done by opencast mining (rather than underground mining) to follow a rather thin coal seam, and therefore constantly digs up new land. If this land were used for PV plants instead of being mined, they would generate more electrical energy per year (!) than the one-time burning of the coal seam below [23], [24].
Coal power needs about 500 g of coal per kWh electric energy [47] while the said PV plant needs about 15 g of various materials. It is therefore not surprising that the mining of materials for PV plants (like copper and iron) is smaller than coal mining [31]:
Forecasts [32] estimate that copper production must be doubled for the next 30 years to meet the increasing demand from electric cars, power grids and renewable energies. The chart shows that even if this leads to more than a doubling of the mining area due to the lower quality of the ore, the area is still far smaller than the area currently used for coal mining. The environmental damage goes beyond the area detected by satellites [33], and for this reason, a radius of 5 km was included in the above chart. Still, coal mines pollute the environment through the air [34] and therefore further than 5 km. Also in copper mines, the purification of the ore is done on site, so it falls under the mining laws and not the industrial laws, and the liquid waste pollutes the environment [35] for more than a hundred years [36]. For an overview, see [37]. Therefore, it is important to keep in mind that about half of the copper mines are in regions with very low water availability, and about half are closer than 20 km to protected areas [38].
Finally, mining can have negative social impacts. Copper in economically exploitable form is not evenly distributed across the planet. More than half of the additional copper production is expected to come from Central and South America [32], [39]. Positive impulses for regional economic development could not be empirically observed so far due to low labour intensity, loose ties to local suppliers and profit outflows [40]. Social conflicts often lead to the criminalisation of activists, repression and forced displacement [41].
Although PV has a much smaller share [42] of copper production than electric vehicles, and consumer products still account for about half of the total copper consumed [32], PV is part of the energy transition that doubles copper demand. So, an unbiased mind weighs the pros and cons not only for PV but includes the entire energy transition.
My personal reasoning:
1. The main negative impact of PV is copper mining, as silver must be obviously avoided to expand PV; the other environmental impacts are minor.
2. The main positive impact of PV is that it significantly reduces our CO2 emissions and thus mitigates far-reaching climate impacts.
3. The alternative to PV is continued coal mining and natural gas extraction. Even if we reduce our energy demand, they have far greater consequences than copper mining, and additionally cause global warming with all its consequences.
To get our climate under control, I see no other way than opening new mines. A shift to a globally deployed technology is hardly possible without a shift in materials. Some environmentalists hope or demand that this is not the case. I usually answer them with point 3 and suggest that they may demand better mining management. Why is mining allowed to pollute the environment so heavily while most other industries must process their waste?
By the way, switching from coal to natural gas is not an alternative: CO2 emissions are halved, but far more [43] methane emissions are produced. In a later blog article, I will go into more detail on how gas companies can support the energy transition with their valuable infrastructure.
Solar energy can be a sustainable backbone of our world running on 100% renewable energy if:
– Environmental and social conditions for copper mining are improved.
– Silver in silicon solar cells is avoided.
– The PV plants are placed in an environmentally responsible way [48-50].
Under these realistically achievable conditions, the use of PV electricity makes every country, business and household more sustainable.
I hope this blog article has given you a more nuanced view of PV electricity and its impacts.
Next time about wind energy.
Pietro
References
[1] This PV plant was built by Trinasolar.com and has a capacity of 30 MW. The median solar irradiance on that site is 1660278 Wh/m2/year. In its initial year, it produced 41714485 kWh, the warranty assures that in its 30th year, it will produce at least 33710021 kWh, and in total over the 30 years 1114352132 kWh [46]. A life cycle analysis can be downloaded from https://www.epditaly.it; go to search, type in “Trina”, and download the two pdf’s.
[2] Z. Liu et al., “Quantitative analysis of degradation mechanisms in 30-year-old PV modules,” Solar Energy Materials and Solar Cells 200, 110019 (2019). https://doi.org/10.1016/j.solmat.2019.110019
[3] D. Bogdanov et al., “Radical transformation pathway towards sustainable electricity via evolutionary steps,” Nature Communications 10, 1–16 (2019). http://dx.doi.org/10.1038/s41467-019-08855-1
[4] D. J. C. MacKay, Sustainable Energy — without the hot air. UIT Cambridge (2009), ISBN 978-0-9544529-3-3. http://www.dspace.cam.ac.uk/handle/1810/217849
[5] C. Holler and J. Gaukel, Erneuerbare Energien – ohne heisse Luft. Oekom Verlag (2018), ISBN 978-3962380809. http://ohne-heisse-luft.de
[6] P. Seligman, Australian sustainable energy – by the numbers, edition 1.3, Melbourne Energy Institute, University of Melbourne (2010).https://energy.unimelb.edu.au/__data/assets/pdf_file/0006/1944060/Australian_Sustainable_Energy-by_the_numbers.pdf
[7] S. Joshi, S. Mittal, P. Holloway, P. R. Shukla, B. Ó Gallachóir, and J. Glynn, “High resolution global spatiotemporal assessment of rooftop solar photovoltaics potential for renewable electricity generation,” Nature Communications 12 (2021). https://doi.org/10.1038/s41467-021-25720-2
[8] US Geological Survey, “Mineral Commodity Summaries 2021” (2021). https://doi.org/10.3133/mcs2021
[9] Silver Institute, Washington, DC. https://www.silverinstitute.org
[10] J. T. Horzel et al., “Industrial Si Solar Cells with Cu-Based Plated Contacts,” IEEE Journal of Photovoltaics5, 1595–1600 (2015). https://ieeexplore.ieee.org/abstract/document/7279053
[11] K. Burrows and V. Fthenakis, “Glass Needs for a Growing Photovoltaics Industry,” Center for Lifecycle Analysis, Columbia University, New York. http://www.clca.columbia.edu/6_Burrows_Fthenakis_SolarMaterials.pdf
[12] K. Aasly, “Properties and behavior of quartz for the silicon process,” PhD thesis, Dep. Geology and Mineral Resources Engineering, Norwegian University of Science and Technology, Trondheim, Norway (2008). https://core.ac.uk/download/pdf/52098782.pdf
[13] M. J. Hilton and P. Hesp, “Determining the Limits of Beach-Nearshore Sand Systems and the Impact of Offshore Coastal Sand Mining,” Journal of Coastal Research 12, 496–519 (1996). https://www.jstor.org/stable/4298500
[14] A. Grbeš, “A life cycle assessment of silica sand: Comparing the beneficiation processes,” Sustainability (Switzerland) 8, 1–9 (2016). https://doi.org/10.3390/su8010011
[15] G. Kavlak, J. McNerney, R. L. Jaffe, and J. E. Trancik, “Metal production requirements for rapid photovoltaics deployment,” Energy & Environmental Science 8 (2015). https://doi.org/10.1039/C5EE00585J
[16] A. Müller, L. Friedrich, C. Reichel, S. Herceg, M. Mittag, and D. H. Neuhaus, “A comparative life cycle assessment of silicon PV modules: Impact of module design, manufacturing location and inventory,” Solar Energy Materials and Solar Cells 230 (2021). https://doi.org/10.1016/j.solmat.2021.111277
[17] G. Parkinson, “Rio Tinto plans massive 7GW wind and solar for smelters and iron ore mines,” RenewEconomy, 20-Oct-2021. https://reneweconomy.com.au/rio-tinto-plans-massive-7gw-wind-and-solar-for-smelters-and-iron-ore-mines/ RenewEcnomy is a well-researched energy analysis feed in Australia.
[18] Intergovernmental Panel on Climate Change (IPCC), “Global warming of 1.5°C” (2019).https://www.ipcc.ch/sr15/
[19] Z. J. N. Steinmann, A. M. Schipper, M. Hauck, S. Giljum, G. Wernet, and M. A. J. Huijbregts, “Resource Footprints are Good Proxies of Environmental Damage,” Environmental Science & Technology 51 (2017). https://doi.org/10.1021/acs.est.7b00698
[20] R. Heijungs, “Comment on ‘Resource Footprints are Good Proxies of Environmental Damage,’” Environmental Science & Technology 51, (2017). https://doi.org/10.1021/acs.est.7b04253
[21] Z. J. N. Steinmann, A. M. Schipper, M. Hauck, S. Giljum, G. Wernet, and M. A. J. Huijbregts, “Response to Comment on “Resource Footprints are Good Proxies of Environmental Damage″,” Environmental Science & Technology 51 (2017). https://doi.org/10.1021/acs.est.7b04926
[22] European Union, “Directive 2008/98/EC of the European Parliament and of the Council of 19 November 2008 on waste and repealing certain Directives” (2008). https://www.legislation.gov.uk/eudr/2008/98/data.pdf
[23] Y. Xu, J. Li, Q. Tan, A. L. Peters, and C. Yang, “Global status of recycling waste solar panels: A review,” Waste Management 75, 450–458 (2018). https://doi.org/10.1016/j.wasman.2018.01.036
[24] M. M. Lunardi, J. P. Alvarez-Gaitan, J. I. Bilbao, and R. Corkish, “Comparative life cycle assessment of end-of-life silicon solar photovoltaic modules,” Applied Sciences (Switzerland) 8, (2018). https://doi.org/10.3390/app8081396
[25] W. H. Huang, W. J. Shin, L. Wang, W. C. Sun, and M. Tao, “Strategy and technology to recycle wafer-silicon solar modules,” Solar Energy 144, 22–31 (2017). http://dx.doi.org/10.1016/j.solener.2017.01.001
[26] F. del Pero, M. Delogu, L. Berzi, and M. Escamilla, “Innovative device for mechanical treatment of End of Life photovoltaic panels: Technical and environmental analysis,” Waste Management 95, 535–548 (2019). https://doi.org/10.1016/j.wasman.2019.06.037
[27] V. Aryan, M. Font-Brucart, and D. Maga, “A comparative life cycle assessment of end-of-life treatment pathways for photovoltaic backsheets,” Progress in Photovoltaics 26, 443–459 (2018). https://doi.org/10.1002/pip.3003
[28] S. lo Piano and K. Mayumi, “Toward an integrated assessment of the performance of photovoltaic power stations for electricity generation,” Applied Energy 186, 167–174 (2017). http://dx.doi.org/10.1016/j.apenergy.2016.05.102
[29] A. A. Pericak et al., “Mapping the yearly extent of surface coal mining in Central Appalachia using Landsat and Google Earth Engine,” PLOS ONE 13 (2018). https://doi.org/10.1371/journal.pone.0197758
[30] American Solar Economy, “Solar vs Coal, Land Area Comparison,” 29-Jan-2009. https://americansolareconomy.blogspot.com/2009/01/solar-vs-coal-land-area-comparison.html
[31] G. von M. M. Cherlet, C. Hutchinson, J. Reynolds, J. Hill, S. Sommer, World atlas of desertification (WAD). Publication Office of the European Union, Luxembourg (2018). Part IV, Limits to Sustainability, p. 134. http://wad.jrc.ec.europa.eu
[32] G. S. Seck, E. Hache, C. Bonnet, M. Simoën, and S. Carcanague, “Copper at the crossroads: Assessment of the interactions between low-carbon energy transition and supply limitations,” Resources, Conservation and Recycling 163 (2020). https://doi.org/10.1016/j.resconrec.2020.105072
[33] V. Maus et al., “A global-scale data set of mining areas,” Scientific Data 7 (2020). https://doi.org/10.1038/s41597-020-00624-w
[34] J. Cortes-Ramirez, S. Naish, P. D. Sly, and P. Jagals, “Mortality and morbidity in populations in the vicinity of coal mining: a systematic review,” BMC Public Health 18, (2018). https://doi.org/10.1186/s12889-018-5505-7
[35] X. Song, J. B. Pettersen, K. B. Pedersen, and S. Røberg, “Comparative life cycle assessment of tailings management and energy scenarios for a copper ore mine: A case study in Northern Norway,” Journal of Cleaner Production 164 (2017). http://dx.doi.org/10.1016/j.jclepro.2017.07.021
[36] L. Schneider et al., “Colonialism and the environment: The pollution legacy of the Southern Hemisphere’s largest copper mine in the 20th century,” The Anthropocene Review 1-21 (2020). https://doi.org/10.1177/2053019620968133
[37] GreenSpec, “Copper production and environmental impact” (2021). https://www.greenspec.co.uk/building-design/copper-production-environmental-impact/
[38] S. Luckeneder, S. Giljum, A. Schaffartzik, V. Maus, and M. Tost, “Surge in global metal mining threatens vulnerable ecosystems,” Global Environmental Change 69 (2021). https://doi.org/10.1016/j.gloenvcha.2021.102303
[39] S. Moreno-Leiva et al., “Renewable energy in copper production: A review on systems design and methodological approaches,” Journal of Cleaner Production 246 (2020).https://doi.org/10.1016/j.jclepro.2019.118978
[40] S. Luckeneder, S. Giljum, and T. Krisztin, “Do mining activities foster regional development? Evidence from Latin America in a spatial econometric framework,” Vienna University of Economics and Business, Institute for Ecological Economics, Working Paper Series 28 (2019). https://epub.wu.ac.at/7114/
[41] M. Weiß, S. Giljum, and S. Luckeneder, “Mining and social conflict in Latin America. Which factors drive conflict escalation?,” Fineprint Brief 11 (2020). https://www.fineprint.global/publications/briefs/mining-conflict-escalation/
[42] International Energy Agency (IEA), “The Role of Critical Minerals in Clean Energy Transitions,” Paris (2021). https://www.iea.org/news/clean-energy-demand-for-critical-minerals-set-to-soar-as-the-world-pursues-net-zero-goals This report gives smaller copper usage at present than in the said PV plant because IEA assumes smaller copper usage for roof top PV systems.
[43] J. S. Rutherford et al., “Closing the methane gap in US oil and natural gas production emissions inventories,” Nature Communications 12 (2021). https://doi.org/10.1038/s41467-021-25017-4
[44] C. Pierce et al., “Monitoring of airborne particulates near industrial silica sand mining and processing facilities,” Archives of Environmental and Occupational Health 74, 185–196 (2019). https://doi.org/10.1080/19338244.2018.1436036 Solar cells require only a small fraction [23] of sand mined for today’s oil and gas fracking industry (“frac sand”). There is certainly enough to meet the Paris Climate Agreement from sites that are not environmentally sensitive. In contrast, sand for the building industry must have different properties and is relatively rare [45]. Still, silicon is frequently mined from quartz sand on beaches [13], which disturbs the environment more than mining of inland sand deposits [14] and rock quartz [12].
[45] P. Peduzzi et al., “Sand, rarer than one thinks,” UNEP Global Environmental Alert Service (GEAS), March 2014. http://na.unep.net/geas/archive/pdfs/GEAS_Mar2014_Sand_Mining.pdf
[46] M. G. Deceglie, D. C. Jordan, A. Nag, A. Shinn, C. Deline, “Fleet-Scale Energy-Yield Degradation Analysis Applied to Hundreds of Residential and Nonresidential Photovoltaic Systems,” IEEE J. Photovoltaics 9, 476–482 (2019). https://ieeexplore.ieee.org/abstract/document/8598843?casa_token=rcbaI1rQP6gAAAAA:S4hxApFt_ws2nJZtiojpmEe7tHZv21gKgTAgdvoQ_MUOAskwdAYU1aayID4B7Cg-f5y7msuttQ
[47] US Energy Information Administration (2021). https://www.eia.gov/tools/faqs/faq.php?id=667&t=2 and https://www.eia.gov/tools/faqs/faq.php?id=74&t=11
[1] This PV plant was built by Trinasolar.com and has a capacity of 30 MW. The median solar irradiance on that site is 1660278 Wh/m2/year. In its initial year, it produced 41714485 kWh, the warranty assures that in its 30th year, it will produce at least 33710021 kWh, and in total over the 30 years 1114352132 kWh [46]. A life cycle analysis can be downloaded from https://www.epditaly.it; go to search, type in “Trina”, and download the two pdf’s.
[2] Z. Liu et al., “Quantitative analysis of degradation mechanisms in 30-year-old PV modules,” Solar Energy Materials and Solar Cells 200, 110019 (2019). https://doi.org/10.1016/j.solmat.2019.110019
[3] D. Bogdanov et al., “Radical transformation pathway towards sustainable electricity via evolutionary steps,” Nature Communications 10, 1–16 (2019). http://dx.doi.org/10.1038/s41467-019-08855-1
[4] D. J. C. MacKay, Sustainable Energy — without the hot air. UIT Cambridge (2009), ISBN 978-0-9544529-3-3. http://www.dspace.cam.ac.uk/handle/1810/217849
[5] C. Holler and J. Gaukel, Erneuerbare Energien – ohne heisse Luft. Oekom Verlag (2018), ISBN 978-3962380809. http://ohne-heisse-luft.de
[6] P. Seligman, Australian sustainable energy – by the numbers, edition 1.3, Melbourne Energy Institute, University of Melbourne (2010).https://energy.unimelb.edu.au/__data/assets/pdf_file/0006/1944060/Australian_Sustainable_Energy-by_the_numbers.pdf
[7] S. Joshi, S. Mittal, P. Holloway, P. R. Shukla, B. Ó Gallachóir, and J. Glynn, “High resolution global spatiotemporal assessment of rooftop solar photovoltaics potential for renewable electricity generation,” Nature Communications 12 (2021). https://doi.org/10.1038/s41467-021-25720-2
[8] US Geological Survey, “Mineral Commodity Summaries 2021” (2021). https://doi.org/10.3133/mcs2021
[9] Silver Institute, Washington, DC. https://www.silverinstitute.org
[10] J. T. Horzel et al., “Industrial Si Solar Cells with Cu-Based Plated Contacts,” IEEE Journal of Photovoltaics5, 1595–1600 (2015). https://ieeexplore.ieee.org/abstract/document/7279053
[11] K. Burrows and V. Fthenakis, “Glass Needs for a Growing Photovoltaics Industry,” Center for Lifecycle Analysis, Columbia University, New York. http://www.clca.columbia.edu/6_Burrows_Fthenakis_SolarMaterials.pdf
[12] K. Aasly, “Properties and behavior of quartz for the silicon process,” PhD thesis, Dep. Geology and Mineral Resources Engineering, Norwegian University of Science and Technology, Trondheim, Norway (2008). https://core.ac.uk/download/pdf/52098782.pdf
[13] M. J. Hilton and P. Hesp, “Determining the Limits of Beach-Nearshore Sand Systems and the Impact of Offshore Coastal Sand Mining,” Journal of Coastal Research 12, 496–519 (1996). https://www.jstor.org/stable/4298500
[14] A. Grbeš, “A life cycle assessment of silica sand: Comparing the beneficiation processes,” Sustainability (Switzerland) 8, 1–9 (2016). https://doi.org/10.3390/su8010011
[15] G. Kavlak, J. McNerney, R. L. Jaffe, and J. E. Trancik, “Metal production requirements for rapid photovoltaics deployment,” Energy & Environmental Science 8 (2015). https://doi.org/10.1039/C5EE00585J
[16] A. Müller, L. Friedrich, C. Reichel, S. Herceg, M. Mittag, and D. H. Neuhaus, “A comparative life cycle assessment of silicon PV modules: Impact of module design, manufacturing location and inventory,” Solar Energy Materials and Solar Cells 230 (2021). https://doi.org/10.1016/j.solmat.2021.111277
[17] G. Parkinson, “Rio Tinto plans massive 7GW wind and solar for smelters and iron ore mines,” RenewEconomy, 20-Oct-2021. https://reneweconomy.com.au/rio-tinto-plans-massive-7gw-wind-and-solar-for-smelters-and-iron-ore-mines/ RenewEcnomy is a well-researched energy analysis feed in Australia.
[18] Intergovernmental Panel on Climate Change (IPCC), “Global warming of 1.5°C” (2019).https://www.ipcc.ch/sr15/
[19] Z. J. N. Steinmann, A. M. Schipper, M. Hauck, S. Giljum, G. Wernet, and M. A. J. Huijbregts, “Resource Footprints are Good Proxies of Environmental Damage,” Environmental Science & Technology 51 (2017). https://doi.org/10.1021/acs.est.7b00698
[20] R. Heijungs, “Comment on ‘Resource Footprints are Good Proxies of Environmental Damage,’” Environmental Science & Technology 51, (2017). https://doi.org/10.1021/acs.est.7b04253
[21] Z. J. N. Steinmann, A. M. Schipper, M. Hauck, S. Giljum, G. Wernet, and M. A. J. Huijbregts, “Response to Comment on “Resource Footprints are Good Proxies of Environmental Damage″,” Environmental Science & Technology 51 (2017). https://doi.org/10.1021/acs.est.7b04926
[22] European Union, “Directive 2008/98/EC of the European Parliament and of the Council of 19 November 2008 on waste and repealing certain Directives” (2008). https://www.legislation.gov.uk/eudr/2008/98/data.pdf
[23] Y. Xu, J. Li, Q. Tan, A. L. Peters, and C. Yang, “Global status of recycling waste solar panels: A review,” Waste Management 75, 450–458 (2018). https://doi.org/10.1016/j.wasman.2018.01.036
[24] M. M. Lunardi, J. P. Alvarez-Gaitan, J. I. Bilbao, and R. Corkish, “Comparative life cycle assessment of end-of-life silicon solar photovoltaic modules,” Applied Sciences (Switzerland) 8, (2018). https://doi.org/10.3390/app8081396
[25] W. H. Huang, W. J. Shin, L. Wang, W. C. Sun, and M. Tao, “Strategy and technology to recycle wafer-silicon solar modules,” Solar Energy 144, 22–31 (2017). http://dx.doi.org/10.1016/j.solener.2017.01.001
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Michele Bina says
A good analysis but perhaps a fallacious premise: “The main negative impact of PV is copper mining”.
It is not. The main content by weight of a PV panel is glass but the main GHG impact of PV panel production is in the production of metallurgical silicon, followed by the synthesis of chlorosilanes to produce polysilicon and finally the growth of single crystal silicon ingots.
That said, this impact is falling dramatically because we are using about one fifth of the silicon used in 2005 per Watt. So most lifecycle analysis studies of PV are wrong and produce higher GHG emissions / W than is true today.
Pietro (Author) says
Hi Michele,
thank you for your comment, you are very welcome and I appreciate your experience as a supply chain management consultant. I have the impression that the main reason for our disagreement is the power supply for silicon production. Trinasolar deliberately buys silicon from provinces that attract new industry with 100% hydropower, e.g. Yunnan province. The PV power plant described consumes 55 tonnes of silicon and 174 tonnes of copper. If silicon had the main impact on greenhouse gases, silicon production (up to wafering) would have to produce more than three times as many emissions as copper production. This is not the case with the use of hydropower in silicon production. To give a sense of this, I say in my blog: “Using pure coal-fired electricity would double the CO2 emissions in the top bar of the graph”. Furthermore, I look not only at greenhouse gas emissions, but also at the sum of other impacts in the life cycle analysis (LCA). There, copper mining is worse than silicon mining for the reasons described in the blog. This leads me to conclude that copper is the main problem. As you say, silicon’s impact is “declining dramatically” because we are using less and less silicon per electricity generated. In my collection of data in [https://web.tresorit.com/l/zg5JS#sZgEIJ_cc1DZRDYSFI9VKA] (safe link), less than 4 g of Si / W is used these days, in 2005 it was about three times that. This could additionally explain our discrepancies.
I like to add that the inclusion of the electricity mix in the LCA is certainly not trivial. For example, if someone claims to use 100% renewable energy, this claim is relativised by the withdrawal of renewable electricity elsewhere in the grid. This also applies to PV production. Many LCA studies simply take the national average of the electricity mix. The catch, however, is how large the region is over which the electricity mix is averaged. I advocate only averaging over regions over which the electricity is actually transported. The hydropower electricity from Yunnan is not transported to the Shanghai region, where one of Trina’s factories is located, nor to Thailand, where another factory is located that contributed panels to the power plant described. The distance is too great. Therefore, hydropower is not included in the electricity mix of Trina’s cell and module production (which increases the carbon footprint), but consequently the silicon purchased does not have many fossil emissions (which reduces the carbon footprint).
What the electricity mix looks like on average has recently become political. The EU is promoting PV production in Europe and there are intentions to put up import barriers with carbon footprint requirements for PV products from Asia. If you average the electricity mix across China, you get a higher footprint for Asian PV than for European PV. I consider this problematic for two main reasons:
A) By averaging the whole national electricity mix, companies are not motivated to reduce their footprint as all their efforts are not included in the average. This is the case in both the EU and China.
B) Tracking the footprints of individual products is complex and inevitably leads to political issues. Should a product from Germany be assessed with the German electricity mix or the EU electricity mix? How much PV electricity from Spain and Italy is included in the German mix? The same applies to China’s many provinces.
I think an effective alternative to B is proposed by William Nordhaus, e.g. in [https://www.foreignaffairs.com/articles/united-states/2020-04-10/climate-club] or in his Nobel Prize speech. Instead of going after individual products, a number of countries should form a “climate club” in which they agree on a CO2 price schedule and impose tariffs on all (not specific) products imported from non-club member countries. Simulations show that even a 4% tariff makes it tempting for non-club members to join the club. This allows the club to grow without getting bogged down in complexities and disputes over the footprint of individual products.
Hector says
Excellent analysis
Trevor Dudley says
Excellent article. Close to the facts. Well stated.
Pierre says
Hi Pietro,
It seems to me that the modelling of Bogdanov in reference [3] actually predicts a need for a bit more than 63 TW by 2050 and not 20 TW.
Pierre
Pietro (Author) says
Hi Pierre, I chose 40 TW because I have collected about 10 different studies that model a global energy transition towards 100% renewables, and they of course give different amounts of required PV capacity. 40 TW is in the middle range. The required capacity depends strongly on how much energy is transported and consumed in the form of hydrogen, compared to direct electricity (hydrogen requires at least three times the electricity). Since we do not know what the future will look like, I hope it seems reasonable to you that I assume 40 TW of required PV capacity. Pietro