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Why do we burn coal and trees to make solar panels?

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Abstract and Figures

All modern technologies are based on the non-renewable fossil fuels and fossil energy that made them possible. Solar photovoltaic (solar PV) technology is no exception. For example, every step in the production of solar PV power systems requires an input of fossil fuels - as the carbon reductants needed for smelting silicon from ore, to provide manufacturing process heat and power, for the intercontinental transport of materials, and for on-site deployment. The only "renewable" materials consumed in PV production are obtained by deforestation - by burning large areas of tropical rainforest for charcoal (another carbon reductant) and to provide the wood chips that are necessary for all silicon smelters to function. Additional mineral resources and fossil energy are needed for constructing factories, process equipment, and maintaining the PV manufacturing infrastructure itself. Silicon smelters, polysilicon refineries, and crystal growers all require uninterrupted, 24/7 power that comes mostly from coal and uranium. Both media and journal claims that solar PV can somehow "replace" fossil fuels for power have not addressed the “non-renewable reality” of the global manufacturing supply chains necessary for the mining, manufacturing, and distribution of PV power systems. Some previous accounts of solar PV production have omitted the raw materials and silicon smelters from the PV “supply chain” picture, which obscures the profoundly non-sustainable, fossil-powered basis of PV technology. A more complete overview of commercial PV production is presented herein, from the sources of raw materials to the deployed array. >38 references from published articles and industry sources are cited.
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Why do we burn coal and trees to
make solar panels? Thomas A. Troszak (2019/11/14 revision)
Figure 1. Workman shovels coal and lumpy quartz (silicon ore)
into a silicon smelter in China. (photo: Getty)
1. Most commercial solar PV modules use
photovoltaic cells
(solar cells) made from
highly purified silicon (Si).
Since the early 1900s, silicon “metal” is reduced from
quartz using carbon in submerged-arc furnaces, each
powered by up to 45 megawatts* of electricity. (Fig 1,2)
Figure 2. Diagram of a silicon smelter showing the three giant carbon
electrodes that provide arc temperatures > 3,000oF for smelting quartz
into “metallurgical grade” silicon (mg-Si) using carbon as a reductant.[26]
(John Wiley and Sons, Ltd.)
2. Why do we need to burn carbon to make solar PV? -
Elemental silicon (Si) can’t be found by itself anywhere
in nature. It must be extracted from quartz (SiO2)
using carbon (C) and heat (from an electric arc) in the
“carbothermic” (carbon+heat) reduction process
called “smelting.” (Si02 + 2C = Si + 2CO) Several
carbon sources are used as reductants in the silicon
smelting plant, which requires ~20 MWh/t of
electricity, and releases CO - resulting in up to 5 - 6 t
of CO2 produced per ton of metallurgical grade
(mg-Si) silicon smelted. [1] Thus, the first step of solar
PV production is gathering, transporting, and burning
millions of tons of coal, coke and petroleum coke -
along with charcoal and wood chips made from
hardwood trees - to smelt >97% pure mg-Si from quartz
“ore” (silica rocks). [1][2][3][4][5][6][7][8][9][10]
*45 megawatts (MW) is enough for a small town (about 33,000 homes).
Figure 3. Pouring liquid metallurgical grade (~99% pure) silicon
into molds, to cool into silicon “metal”. (Getty)
3. Even more fossil fuels are burned later, to generate
electricity for the polysilicon, ingot, wafer, cell, and
module production steps shown. [21] As a result of all
these processes, the solar PV industry generates
megatons of CO and CO2. But as shown below (fig 4),
some often-cited descriptions of solar module
production omit the raw materials and smelting
process from the PV supply chain which obscures the
use of fossil fuels and the vast amount of deforestation
necessary for solar PV production. [1][3][9][27]
Figure 4. (source: National Renewable Energy Laboratory, 2018)
4. Raw materials for metallurgical-grade silicon
Raw materials for one ton (t) MG-Si (Kato, et. al) [37]
Quartz 2.4 t
Coal 550 kg
Oil coke 200 kg
Charcoal 600 kg
Woodchip 300 kg
Raw materials for one ton (t) MG-Si (Globe) [3]
Quartz 2.8 t
Coal 1.4 t
Woodchips 2.4 t
For 110,000 tpy (tons per year) MG-Si (Thorsil) [1]
Quartz 310,000 tpy
Coal, coke and anodes 195,000 tpy
Wood 185,000 tpy
Total 380,000 tpy
When calculating CO2 emissions from silicon smelting, “by
joint agreement” some authors exclude CO2 emissions from
non-fossil sources (charcoal, wood chips), power generation,
and transportation of raw material. [27]
5. Sources of carbon for solar silicon smelting
• Coal - Is a dense, rock-like fuel. The (low ash) coal
used directly for silicon smelting is mostly the ”Blue
Gem" from Cerrajón, Columbia, Kentucky, USA, or
Venezuela. [1][2][3][5][6][7][8]
The Cerrajón open-pit mine in Columbia supplies “Blue
Gem” coal for silicon smelters around the world.
A ”Slot Oven” discharging coke into a railroad car. (photo: Alamy)
• Metallurgical Coke (Metcoke) is a
tough, cinder-like solid fuel made
by "coking" coal in large “slot
ovens” - to drive out most of the
volatile tars, etc. to the atmosphere
as smoke, flame, carbon monoxide,
carbon dioxide, sulfur dioxide,
other gasses, and water vapor.
(photo: Getty Images)
The coking process is nearly
identical to the process used for
making charcoal from wood (see charcoal production
below). Restricting the
air supply to a large
mass of burning coal
allows about 40% of the
coal to “burn off” -
leaving behind a solid
residue (coke) with a
higher carbon content
per ton that the original
coal. It takes about 1.6 t
of coal to make a ton of
Metcoke looks like
porous, silvery grey coal.
Filling barges with petcoke outside Chicago, Ill, USA (photo)
• Petroleum Coke (Petcoke) - is a solid fuel in the form
of pellet-like granules, which are a carbon-rich
byproduct of crude oil refineries. Millions of tons of
petcoke are also made directly from raw bitumen (tar).
Due to its low price and high carbon content, petcoke
made in American refineries from "Canadian Tar
Sands” is a source of carbon exported from the U.S. to
silicon manufacturers in China. [9]
“Because it is considered a refinery byproduct, petcoke
emissions are not included in most assessments of the
climate impact of tar sands” [10]
“Beehive” charcoal ovens in Brazil (Alamy)
• Wood Charcoal- Many hardwood
trees must be burned to make wood
charcoal. In the traditional process,
wood is stacked into “beehive ovens”,
ignited, then mostly smothered to
prevent the wood from burning completely to ash. By
weight, about 75% of the wood is lost to the
atmosphere as CO, CO2, smoke, and heat.
Some silicon producers use “charcoal plantations,” but
they only supply a fraction of the current demand of
carbon for silicon production. The rest of the carbon
supply has to come from imported coal or coke, or the
cutting and burning of “virgin” rainforest. [13][14][15][16]
In Brazil, it is estimated that more than a third of the
country’s charcoal is still produced illegally from
protected species. [14] Brazil is a charcoal supplier to
silicon producers in other countries, including the
United States. Silicon smelters around the world use
charcoal from many sources, so solar silicon may be
smelted with charcoal made directly from rainforest
not grown on plantations.
This hardwood forest in the U.S. was clear cut to make wood
6. Hardwood Chips (also called
Metchips) - Matchbox-sized
fragments of shredded
hardwood must be mixed into
the silicon smelter “pot” for
many reasons - to allow the
reactive gasses to circulate, so
the liquid silicon that forms can settle to the bottom
for tapping, and to allow the resulting CO (and other
gasses) to escape the smelter “charge” safely. [4]
Solar silicon quartz rocks (Wacker Chemie)
7. Silicon ore - Quartz - (silica, silicon dioxide, SiO2)
Even if sufficiently pure, silica sand won’t work in any
silicon smelter, it is too fine. Selected high-purity
quartz is mined and graded into “lumpy” (fist-sized)
gravel for smelting. Worldwide, "solar grade” deposits
of quartz are somewhat scarce, and highly valued.
A single polysilicon plant like this one in Tennessee, USA. can
draw 400 megawatts of electricity, enough power for about
300,000 homes. (Wacker Polysilicon)
8. Polysilicon production
Metallurgical grade silicon (mg-Si) from the smelter is
only about 99% pure, so it must undergo two more
energy-intensive processes before it can be made into
solar cells. First, the Siemens Process converts (mg-Si)
from the smelter into polycrystalline silicon (called
polysilicon) by a high-temperature vapor deposition
This is a bit like “growing rock candy” on
hyper-pure silicon “strings” inside a pressurized-gas
filled “bell-jar” reactor.As a mixture of silicon gas
(made from mg-Si) and hydrogen gas passes through
the reactor vessel, some of the silicon gas molecules
“cling” to the electrically heated “strings” (called
filaments) causing them to grow into “rods” of
99.9999% pure (or better) polysilicon.
Left: When heated to around 1100°C the polysilicon “filaments”
standing beneath the reactor cover can “catch” about 20% of the
silicon atoms that pass through the reactor in gaseous form.
Right: Polysilicon “rods” after 5 days of growth. (Siemens AG)
Each batch of polysilicon “rods” takes several days to
grow, and a continuous, 24/7 supply of electricity to
each reactor is essential to prevent a costly “run abort.”
So polysilicon refineries depend on highly reliable
conventional power grids, and usually have two
incoming high-voltage supply feeds.
A polysilicon plant consumes ~1.6 - 6 t of
incoming mg-Si, and requires at least 175 MWh (or
more) of additional electricity per ton of polysilicon
produced - about 10 times the energy already used for
smelting each ton of mg silicon from ore. [11] After the
rods are removed from the reactor, they are sawed into
sections or broken into “chunks” for loading into
crucibles in the next step.
Polysilicon rods and sections being broken into chunks by hand
in a clean room. (Hemlock)
Polysilicon chunks being heated in a crucible. When melted, a
single crystal will be pulled out of the liquid polysilicon. (Getty)
9. Crystal growing (ingot production)
For making single-crystal solar cells (called mono PV)
the PV industry uses the Czochralski process to
further purify the polysilicon, and align the silicon
molecules into a single-crystal form.
First, polysilicon chunks are melted in a
rotating crucible in an inert atmosphere. Then a small
seed crystal of silicon is lowered into the molten
polysilicon. As the seed crystal is slowly withdrawn, a
single silicon crystal forms from the tip of the seed. As
the crucible turns, the polysilicon continues to grow
into a cylindrical ingot, leaving most of the non-silicon
impurities behind in the 5-10% of “pot scrap” remaining
after the crystal is drawn free.
Czochralski ingot being pulled from melted polysilicon.
(Image source: Siltronix)
Czochralski ingot after cooling (Image source: Getty)
This process requires several days, and uninterrupted
power. An ingot/wafer/cell plant can use more than
100 MWh additional energy per ton of incoming
polysilicon, about 6 times as much as the original
smelting of the silicon from ore. After slow cooling,
the ingot's unusable crown and tail are cut off (about
10%), the center is then ground down, the four “chords”
(long sides) are sawn off (about 25%) leaving a
rectangular “brick” so the solar wafers will be almost
square after slicing.
Czochralski process whole ingot (left), and brick and chords after
sawing (right), crown and tail (upper right) (SVM)
For multi-crystalline cells (called multi PV)
polysilicon is melted in rectangular quartz molds, then
allowed to cool slowly into a rectangular ingot of
multi-crystalline silicon. which is trimmed to remove
unusable portions, then sliced into bricks.
10. Wafer sawing
Then, like a loaf of bread, the silicon "bricks" are sliced
with wire saws into thin wafers, which will later be
processed into cells.
About half of the "brick" is lost as "sawdust" in the
wafer slicing process, and this can't be recovered. So,
after all of the energy and materials that have gone into
making each "brick", much of the incoming polysilicon
does not ever become finished wafers. Some of the
heads, tails, chords, and trimmings can be etched (to
remove contamination) and remelted using additional
energy if the purity of the scrap is sufficient to justify
the expense, otherwise they are discarded as waste.
11. Cell and module production.
Once the wafers are sliced, they are made into “cells”
by adding layers of other materials and components in
a series of additional production steps.
Diffusion Furnace in the PV-TEC at Fraunhofer ISE.
Loading of the diffusion tubes with batches of multicrystalline
silicon wafers. The wafers, sorted into quartz boats, are brought
into the (up to) 1000 °C hot quartz tubes. (Fraunhofer ISE)
Then the cells are assembled into modules. Beside
silicon wafers, most solar PV modules also require
many other energy-intensive materials - aluminum (for
the frame), silver, copper, glass, plastic, highly toxic
rare earth metals, acids, and dozens of other chemicals
for processing the polysilicon into cells and modules. A
lot of electricity is needed to power the cell production
and module assembly, a supply of natural gas is used to
provide heat in the process.
Solar module inspection on the assembly line. (Solar World)
12. Other materials and steps
Once the modules are made, the whole PV system
usually needs steel or aluminum framing, concrete, and
some empty land (or a rooftop) to position it securely
toward the sun, a lot of wiring to connect (through
DC/AC inverters and transformers) to the existing
power grid, or directly to battery banks,
PV support structure and concrete foundation (Hill & Smith)
Of course, it takes a lot of energy and resources to
make steel, aluminum, concrete, inverters, copper
wiring, and all of these other materials. In many cases,
the "balance of system" components in a PV
installation can require as much (or more) “up-front”
resources and energy to make as the modules. [21]
In addition, the amount of fossil fuels and
non-renewable resources needed to construct and
maintain new PV production infrastructure (smelters,
polysilicon refineries, etc.) is considerable, but has
been excluded from all “life cycle analysis”(LCA) of
solar PV production by definition. [38]
13. Transportation
Throughout the solar PV manufacturing process all of
the materials and products must be shipped to and
from more than a dozen countries around the world in
large barges, container ships, trains, or trucks - all
powered by non-renewable oil. [36]
14. Power
Worldwide, only a few silicon smelters, like those in
Norway, are powered primarily by hydro-electricity.
Elsewhere, the current majority of smelters, polysilicon
refineries, ingot growers, cell and module factories are
running on grids powered mostly by fossil fuels and
uranium. At present, more than 50% of all solar silicon
is made in China, where the industrial grid is powered
largely by fossil fuels, primarily low-grade coal.
Depending on the “energy mix” available, the quantity
of coal, coke, or gas that is being burned to deliver
power 24/7 to the PV factories may be far greater than
the amount needed as the carbon source for smelting
silicon. To provide a realistic assessment of the total
environmental impact of PV manufacturing, this must
be added to the “fossil fuel bill” for solar PV
production - along with the “embodied energy“ of PV
factories. [11][12][21]
15. Conclusions
Every step in the production of solar photovoltaic (PV)
power systems requires a perpetual input of fossil fuels -
as carbon reductants for smelting metals from ore, for
process heat and power, international transport, and
deployment. Silicon smelters, polysilicon refineries, and
crystal growers around the world all depend on
uninterrupted, 24/7 power that comes mostly from coal
and uranium. The only "renewable" materials consumed
in PV production are obtained by deforestation - for
wood chips, and by burning vast areas of tropical
rainforest for charcoal used as a source of carbon for
silicon smelters. So far, both media and journal claims
that solar PV can somehow "replace fossil fuels" have not
addressed the non-renewable reality of global supply
chains necessary for mining, manufacturing, and
distribution of PV power systems. Based on current
world production levels of solar PV, an attempt to
replace conventional electricity production with solar
PV would require a dramatic increase in the amount of
coal and petcoke needed for silicon smelting, along with
the increased cutting of vast areas of forest for charcoal
and wood chips.
Readers are encouraged to examine all of the references
below, to become aware of other aspects with solar pv
manufacturing and deployment that are beyond the
scope of this paper.
[1] Thorsil (2015) “Metallurgical Grade Silicon Plant - Helguvík, Reykjanes municipality (Reykjanesbær),
Reykjanes peninsula, Iceland Environmental Impact Assessment (EIA) Capacity: 110,000 tons”
Thorsil_Lingua-2-%20konsekvensutredning.pdf (1) “Thorsil's initial assessment report was based
on using...Coal from El Cerrajon in Columbia...for an annual production...of 110,000 tpy [of
mg-Si]…would correspond to 605,000 tpy of carbon dioxide…The Environment Agency feels
that…such exhaust would significantly increase Iceland's overall emissions“
[2] Efla (2013) “Environmental Impact Assessment of a SILICON METAL PLANT AT BAKKI IN
faa93b/eia_island_silizium.pdf (2) “The main raw materials used for the production of Silicon
Metal are quartzite... coals (mainly from [Cerrejón] Columbia, Venezuela, and USA), charcoal,
wood chips”
[3] “New York State Department of Environmental Conservation - Facility DEC ID: 9291100078 PERMIT
Under the Environmental Conservation Law (ECL) Permit Issued To: GLOBE METALLURGICAL
INC (3) “Globe
Metallurgical produces high purity silicon metal...The facility is a major source of emissions
of sulfur dioxide, carbon monoxide, hydrogen chloride and nitrogen oxides… “The submerged
electric arc process is a reduction smelting operation...Reactants consisting of coal, charcoal,
petroleum coke, or other forms of coke, wood chips, and quartz are mixed and added at the top
of each furnace... At high temperatures in the reaction zone, the carbon sources react with
silicon dioxide and oxygen to form carbon monoxide and reduce the ore to the base metal
[4] “The Use and Market for WOOD in the ELECTROMETALLURGICAL Industry” (4) [woodchips are used in smelters]...to provide a
large surface area for chemical reaction to take place more completely and at improved
rates…To maintain a porous charge, thereby promoting gentle and uniform - instead of violent
- gas venting…To help regulate smelting temperatures…To keep the furnace burning smoothly
on top…To reduce conductivity…To promote deep electrode penetration…To prevent bridging,
crusting, and agglomeration of the mix…To reduce dust, metal vapor, and heat loss; and as a
result to improve working conditions near the furnace.
[5] Healy, N., Stephens, J. C., & Malin, S. A. (2019). “Embodied energy injustices: Unveiling and
politicizing the transboundary harms of fossil fuel extractivism and fossil fuel supply chains.” Energy
Research & Social Science
, 48
, 219-234. (link) (5)“Cerrejón is one of the world’s largest open-pit
coal mines [supplying silicon manufacturers] extraction often entails the physical
displacement of populations or the “slow violence” of landscape destruction, water
contamination and livelihood disruption”
[6] What Terrible Injustices Are Hiding Behind American Energy Habits?
By Itai Vardi • Friday, November
16, 2018 (link) (6) “There is a clear ‘consumer blindness’ and citizens and residents are often
unaware of where the fuel they consume is coming from and what injustices were inflicted on
communities within those sites of fossil fuel extraction,” said Healy. “Exposing these injustices
of energy ‘sacrifice zones’ — like [the Cerrejón open-pit coal mine] in La Guajira, Colombia …—
could be critical for future energy policy decision-making.”
[7] 2017/06/18/why-this-part-of-coal-country-loves-solar-power-215272 (7)“the seam in Whitley County
[Kentucky] is an even more valuable variety of metallurgic coal known as “blue gem.”...“You
need the blue gem to make the solar panels, and that’s what people don’t know,” Moses told
me, articulating a simple truth: “Without Coal Valley, there’s no Silicon Valley”
n-production-while-coal-prices-continue-to-soar-600823111.html(8) “Colombian coal accounts
for close to 75% of coal imports to the U.S… New Colombia Resources' Blue Gem coal is only
found on the KY-TN border and central Colombia and is used to produce specialty metals such
as Silicon to make solar panels, electric car batteries, and many more next generation
[9] (9) “Figure
5. [graph] Chinese Petcoke Consumption by Sector (2013 silicon=6%) (2014 silicon=7%) A
significant share of the petcoke used in China [which was made in U.S. refineries] is imported
from the United States,...“According to the U.S. Energy Information Administration (EIA), U.S.
petcoke exports to China… a staggering 7 million metric tons in 2013...accounting for nearly 75
percent of Chinese petcoke. 
[10]Petroleum Coke: The Coal Hiding in the Tar Sands (10) “Because it is considered a refinery
byproduct, petcoke emissions are not included in most assessments of the climate impact of
tar sands"...
(11) “these furnaces would have a voracious appetite for electricity: around 105 megawatts on a
continuous basis, roughly the equivalent of 68,000 homes...the facility would demand more
power than the dam could provide....Producing one ton of silicon metal requires about six tons
of raw materials...Nearby sawmills would send seven or eight trucks per day to deliver wood
chips, which are integral to the smelting process….“The smelting process requires a rare type
of metallurgic coal known as “blue gem,” … Operations at the smelter would demand
approximately 48,000 metric tons of coal per year—roughly 40 rail cars each month.”
[12] (12) “A nuclear
plant is 1200 megawatts. Fully built out, [Wacker Polysilicon] could be a third of a nuclear
plant [400 MW]...Not everybody out there can handle that size of a load. We’re selling the fact
that we [TVA] have the reliability, and we have a very diverse portfolio across coal, nuclear and
[13]Jungbluth, N., M. Stucki, R. Frischknecht, S. Büsser, and ESU-services Ltd. & Swiss Centre for Life
Cycle Inventories. (2009) "Part XII photovoltaics." Swiss Centre for Life Cycle Inventories
(link) (13)
“An issue of concern... is the use of charcoal in this [photovoltaic silicon] process that
originates from Asia or South America and might have been produced from clear cutting
rainforest wood”
[14]Eikeland, Inger Johanne, B. Monsen, and Ingunn S. Modahl.(2001) "Reducing CO2 emissions in
Norwegian ferroalloy production." Greenhouse Gases in the Metallurgical Industries: Policies,
Abatement and Treatment, (Met. Soc. CIM), Toronto
325 . (link) (14) Most of the charcoal
used…[for silicon production] imported from Asia and South America. The crude, traditional
methods of charcoal making, which are still widely used in these continents, are inefficient
and strongly pollute the environment.”
[15]Nisgoski, Silvana & Muniz, Graciela & Morrone, Simone & Schardosin, Felipe & França, Ramiro.
(2015). NIR and anatomy of wood and charcoal from Moraceae and Euphorbiaceae species. Revista
Ciência da Madeira - RCM. 6. 183-190. 10.12953/2177-6830/rcm.v6n3p183-190. (link) (15) “charcoal
supply is still present in illegal cutting of native forests, which represented 30-35% of total
output [in Brazil]… charcoal consumption represents the deforestation of approximately 1.6
million hectares or 16.000 km² of the Cerrado Biome”
(16) “Dehong's silicon
industry … “has caused a serious damage to forest resources," and estimated that "119,700 tons
of charcoal were consumed in the production of industrial silicon in Dehong prefecture in
2014… 31 square miles—"of forests were cut down. (…) In 2016, the [silicon] industry consumed
nearly twice that amount (216,273 tons of charcoal)
[17]BP Statistical Review of World Energy, 67th Edition, June 2018 (17) “despite the huge policy push
encouraging a switch away from coal and the rapid expansion of renewable energy in recent
years, there has been no improvement in the mix of fuels feeding the global power sector over
the past 20 years. Astonishingly, the share of coal in 2017 was exactly the same as in 1998. The
share of non-fossil fuels was actually lower, as growth in renewables has failed to compensate
for the decline in nuclear energy.”
[18]De Castro, Carlos, Margarita Mediavilla, Luis Javier Miguel, and Fernando Frechoso. "Global solar
electric potential: A review of their technical and sustainable limits." Renewable and Sustainable
Energy Reviews
28 (2013): 824-835. (link) (18) “based on real examples...our results show that
present and foreseeable future density power of solar infrastructures are much less (4–10
times) than most published studies… an overview of the land and materials needed for large
scale implementation show that many of the estimations found in the literature are hardly
compatible with the rest of human activities.”
[19]Koomey, J. G., Calwell, C., Laitner, S., Thornton, J., Brown, R. E., Eto, J. H., ... & Cullicott, C. (2002).
Sorry, wrong number: The use and misuse of numerical facts in analysis and media reporting of
energy issues. Annual review of energy and the environment
, 27
(1), 119-158. (link)(19)
“Unfortunately, numbers that prove decisive in policy debates are not always carefully
developed, credibly documented, or correct...A common mistake in the media has been to apply
this statistic (1000 homes per MW) to intermittent renewable power sources...Intermittent
renewables generally produce far fewer kilowatt-hours per MW than conventional power
plants...this widely used equivalence between homes and MW should generally not be applied
to intermittent renewables such as...PVs.”
[20] Shaner, Matthew R., Steven J. Davis, Nathan S. Lewis, and Ken Caldeira. (2018) "Geophysical
constraints on the reliability of solar and wind power in the United States." Energy & Environmental
11, no. 4 (2018): 914-925 (link) (20) “Achieving 99.97% reliability with a system
consisting solely of solar and wind generation... would require a storage capacity equivalent to
several weeks of average demand…Three weeks of storage (227 TW h) [which] results in~6500
years of the annual Tesla Gigafactory production capacity or a ~900x increase in the pumped
hydro capacity of the U.S.”
[21]Carbajales-Dale, Michael, Charles J. Barnhart, and Sally M. Benson.(2014) "Can we afford storage?
A dynamic net energy analysis of renewable electricity generation supported by energy storage."
Energy & Environmental Science
7, no. 5 (2014): 1538-1544. (link)
(21) “PV technologies (CIGS and
sc-Si)…cannot ‘afford’ any storage while still supplying an energy surplus to society… since
they are already operating at a deficit...These technologies require large, ‘up-front’ energetic
investments…A fractional [energy] re-investment of greater than 100% … means that the
industry consumes more electricity than it produces on an annual basis, i.e. running an energy
[22] Milligan, M., Ela, E., Hein, J., Schneider, T., Brinkman, G., & Denholm, P. (2012). Renewable Electricity Futures
Study. Volume 4: Bulk Electric Power Systems: Operations and Transmission Planning
NREL/TP-6A20-52409-4). National Renewable Energy Lab.(NREL), Golden, CO (United States). (link)(22)
“although REFutures describes the system characteristics needed to accommodate high levels of
renewable generation, it does not address the institutional, market, and regulatory changes that may be
needed to facilitate such a transformation…[and] a full cost-benefit analysis was not conducted to
comprehensively evaluate the relative impacts of renewable and non-renewable electricity generation
[23] Lithium Ion batteries for Stationary Energy Storage - The Office of Electricity Delivery and
Energy Reliability, Pacific Northwest National Laboratory (23) “Despite their success in mobile
applications, Li-ion technologies have not demonstrated sufficient grid-scale energy storage
feasibility “
[24]Lessons Learned Report - Electrical Energy Storage DOCUMENT NUMBER CLNR-L163
AUTHORS John Baker, James Cross, EA Technology Ltd, Ian Lloyd, Northern Powergrid
PUBLISHED 08 December 2014 (24) “The round trip efficiencies for the [Li-ion] EES systems
have been calculated [in actual use]… between 41% and 69% where parasitic loads are included“
[25] (25) “using the
kind of lead-acid batteries available today to provide storage for the worldwide power grid is
[26] Luque, A., & Hegedus, S. (Eds.). (2011). Handbook of photovoltaic science and engineering
John Wiley & Sons. (link)(26) “Photovoltaics is polluting just like all high-technology or
high-energy industries only with different toxic emissions … Manufacturing of PV modules on
a large scale requires the handling of large quantities of hazardous or potentially hazardous
materials (e.g. heavy metals, reactive chemical solutions, toxic gases”
on_and_Silicon_metal_in_Norway (27) “These emission factors only include CO2 emitted from fossil raw
materials in the reduction process. CO2 from biological, renewable sources is not included (according to
joint agreement). Neither is CO2 emitted from electric power production or during transportation of raw
[28] Cleaning Up Clean Energy - (28) “the
(PV) industry has largely overlooked investigative reports revealing current problems with
production waste, particularly pertaining to Chinese manufacturing. Until these concerns
receive more attention, promises of panel recycling will quell any public anxiety, preventing
the creation of necessary safeguards to stop rogue firms from unsafe manufacturing practices”
why-do-they-produce-so-much-toxic-waste/#256668c121cc(29) “We estimate there are 100,000
pounds of cadmium contained in the 1.8 million panels,” Sean Fogarty of the group told me.
“Leaching from broken panels damaged during natural events — hail storms, tornadoes,
hurricanes, earthquakes, etc. — and at decommissioning is a big concern.”
ig-environmental-problem (30) Lu Fang, secretary general of the photovoltaics decision in the China
Renewable Energy Society, wrote...By 2050 these waste panels would add up to 20 million
tonnes, or 2,000 times the weight of the Eiffel Tower...Tian Min, general manager of Nanjing
Fangrun Materials, a recycling company in Jiangsu province that collects retired solar panels, said
the solar power industry was a ticking time bomb.“It will explode with full force in two or three
decades and wreck the environment, if the estimate is correct,”
d-states/ (31) “We’ve conducted some toxicity testing on modules, and we have seen results showing
that the presence of lead is higher than the threshold allowed by the TCLP (toxicity
characteristic leaching procedure)...There is a potential for leaching of toxic materials such as lead
in landfill environments. If modules are intact, it’s a low risk, but as soon as they’re broken or
crushed, then the potential for leaching is increased.”
ulen.html (32) "Based on installed power and performance weight, we can estimate that by the year
2016, photovoltaics has spread about 11,000 tonnes of lead and about 800 tonnes of Cd
(cadmium)," the study said”
[33] (33)
“disposal in “regular landfills [is] not recommended in case modules break and toxic materials
leach into the soil” and so “disposal is potentially a major issue.”
[34] Tao, Coby S., Jiechao Jiang, and Meng Tao. "Natural resource limitations to terawatt-scale solar
cells." Solar Energy Materials and Solar Cells
95, no. 12 (2011): 3176-3180.“Material scarcity prevents most current solar cell
technologies from reaching terawatt scales. (…) Scarce materials in solar cells include indium,
gallium, tellurium, ruthenium, and silver. - Natural resource limitations to terawatt-scale solar
[35] Metal-demand-for-renewable-electricity-generation-in-the-netherlands “The current global
supply of several critical metals is insufficient to transition to a renewable energy system.
…production of wind turbines and photovoltaic (PV) solar panels already requires a
significant share of the annual global production of some critical metals… Furthermore,
mining is often associated with significant environmental and social costs”
“Although the CO2 intensity of many major ship classes decreased (i.e., they became more
efficient) from 2013 to 2015, total CO2 emissions from ships increased. For example, although
the CO2 intensity of general cargo ships (measured as emissions per unit of transport supply)
decreased by 5%, CO2 emissions increased by 9% Thus, increases in distance traveled due to a
greater demand for shipping more than offset gains in operational efficiency during the
period studied”
[37] Kato, K., Murata, A., & Sakuta, K. (1998). Energy pay-back time and life-cycle CO2 emission of
residential PV power system with silicon PV module. Progress in Photovoltaics: Research and
, 6
(2), 105-115.
[38] Fthenakis, V., Kim, H., Frischknecht, R., Raugei, M., Sinha, P., & Stucki, M. (2011). Life cycle
inventories and life cycle assessment of photovoltaic systems. International Energy Agency (IEA)
, 12
... As an example, indicators solely relying on CO 2eq may promote the adoption of technologies based on Rare Earth Elements (REE) without considering the effects of mining on common resources. Another concern is the lack of disclosure regarding the origin of procurement, which prevents open validation of actual allocations (e.g., utility companies claiming to produce renewable energy may use technologies that require non-renewable resources [12]); a deficiency of this kind is found in the Land Use, Land-Use Change, and Forestry (LULUCF) sector and in European regulations applied to the Emission Trading Scheme (ETS), which stated that biomass had an emission factor of 0 and its CO 2 emissions could be withdrawn from total emissions (Part 5, section 2 in No. 601/2012/EU; point 15 in Decision No. 525/2013/EU and No. 529/2013/EU). This kind of uncertainty increases the risks of double expending and misuse of impact assessments in favour of stakeholders benefiting from competitive advantages in negotiation power or exercising exploitation rights. ...
... Particularly, j is the counter for the depth-level of the analysis (at the transaction/procurement level); this refers to the considered stakeholder whose impact is being cumulated. The grouped references Resourcesand N th scope in Equation (12) represent, respectively, the Resource and the N th -scope component of this model. Introducing the definition of the wealth from raw materials (R) from Equation (5) and substituting it into Equation (12), we can write: ...
... To this purpose, let us now proceed to apply both Equations (7) and (12) as planning tools for the landowners to decide which choice among the producible output can maximize their revenue. For Equation (7), we can write: ...
Full-text available
In this paper, a sustainability framework for global and scalable payment systems is introduced. It is based on energy and resource consumption and pollutant classes and is inspired by ISO14040 principles. This paper aims to provide guidance for the implementation of blockchain-based technologies in a Life-Cycle Assessment methodology. The impact criteria adopted in this first approximation are at the stakeholders’ level. Enhancement through Enterprise Resource Planning software integration is considered to extend the impact allocation to the level of products and services. The system is designed on environmental economic models based on resources. A continuous depletion in the quality of exchangeable output is also modelled with respect to raw material consumption. We also consider the geophysical coordinates of pollutant emissions and the concurrent emission of pollutants affecting the quality of such outputs. This framework aims to be initially applied to the CO2eq indicator, which is identified by a set of aerial pollutants with global warming potential as proposed by the Intergovernmental Panel on Climate Change. Nonetheless, an incentive scheme within the so-defined payment system is possible and herein suggested, including the extension to other impact criteria (e.g., pollutants released in water and soil). Multiple approximations are made in order to overcome the difficulty in sampling reservoirs of natural resources, such as (1) disregarding regeneration rate and physical limits of raw material reservoirs and (2) estimating the minimum amount of pollutants affecting the perceived quality of economic transactions. Eventually, sampling policies are outlined as fundamental tactics to foster the effectiveness of this framework.
... While quartz can be used from different regional sources the coal needs to be of special quality. Therefore, European silicon producers can be reliant to coal imports from South America (Troszak, 2019). ...
Full-text available
Silicon (Si) plays a central role in combating climate change. Besides its use as an alloying element or raw material for silicones, it is used for photovoltaic (PV) modules to generate renewable energy (Woodhouse et al., 2019). However, the industrial production of silicon requires a process temperature of 2,000 °C and the use of the natural raw materials quartz and coal. Thus, the production of silicon is resource- and energy-intensive and emits CO2 (Kero et al., 2017; Mannvit, 2015). Therefore, research is being conducted to improve the energy and raw material efficiency by novel raw materials and production processes. In this paper, we present a novel process and first experiments for silicon production based on the synthesis of silicon monoxide (SiO) from quartz and charcoal and the subsequent condensation of SiO to a silicon-containing condensate. The condensate is a fine mixture of silicon and silicon dioxide (SiO2). Heating this condensate will separate silicon from the surrounding SiO2-matrix (Broggi, 2021). Parameters in this study are the particle size of raw materials, flowrate of Argon (Ar), and condensation temperature. The experimental setup allows the production of SiO from quartz and charcoal at 1,610 °C and a brown silicon-containing condensate forms at 1,300 – 1,450 °C. To provide a sufficient condensation area, ceramic balls are added to the condensation zone. A silicon layer covers the ceramic balls and inner reactor walls at the end of the experiments. The silicon layer forms underneath the brown condensate. Therefore, the silicon is supposed to originate from the brown condensate. While extraction of silicon from the ceramic balls to form a silicon bath at the furnace bottom was not possible, crystalline silicon phases were identified by Raman spectroscopy and Xray diffraction (XRD). In contrast to industrial silicon production, it is possible to use powdered raw materials and lower the overall process temperature to 1,610 °C. The work lays the foundation for further research to develop energy- and resource-efficient technologies for silicon production.
Technical Report
Full-text available
Life Cycle Assessment (LCA) is a structured, comprehensive method of quantifying material- and energyflows and their associated impacts in the life cycles of products (i.e., goods and services). One of the major goals of IEA PVPS Task 12 is to provide guidance on assuring consistency, balance, transparency and quality of LCA to enhance the credibility and reliability of the results. The current report presents the latest consensus LCA results among the authors, PV LCA experts in North America, Europe and Asia. At this time consensus is limited to five technologies for which there are well-established and up-to-date LCI data: mono- and multi-crystalline Si, CdTe CIGS, and high concentration PV (HCPV) using III/V cells. The LCA indicators shown herein include Energy Payback Times (EPBT), Greenhouse Gas emissions (GHG), criteria pollutant emissions, and heavy metal emissions. Life Cycle Inventories (LCIs) are necessary for LCA and the availability of such data is often the greatest barrier for conducting LCA. The Task 12 LCA experts have put great efforts in gathering and compiling the LCI data presented in this report. These include detailed inputs and outputs during manufacturing of cell, wafer, module, and balance-of-system (i.e., structural- and electrical- components) that were estimated from actual production and operation facilities. In addition to the LCI data that support the LCA results presented herein, data are presented to enable analyses of various types of PV installations; these include operational data of rooftop and ground-mount PV systems and country-specific PV-mixes. The LCI datasets presented in this report are the latest that are available to the public describing the status in 2011 for crystalline Si, 2010-2011 for CdTe, 2010 for CIGS, and 2010 for HCPV technology. This report provides an update of the life cycle inventory data in Section 5 of the previous report: V. Fthenakis, H. C. Kim, R. Frischknecht, M. Raugei, P. Sinha, M. Stucki , 2011, Life Cycle Inventories and Life Cycle Assessment of Photovoltaic Systems, International Energy Agency(IEA) PVPS Task 12, Report T12-02:2011. Updates are provided for the crystalline silicon PV global supply chain (Section 5.1), thin film PV module manufacturing (Sections 5.2-5.3), PV mounting structures (Section 5.5), and country-specific electricity grid mixes (Section 5.9). Other sections of this report are the same as in the previous report. Electronic versions of the updated tables in Section 5 are available at IEA PVPS (; select Task 12 under Archive) and treeze Ltd (; under Publications).
The predicted energy demand will reach 28TW by 2050 and 46TW by 2100. The deployment of solar cells as a source of electricity will have to expand to a scale of tens of peak terawatts in order to become a noticeable source of energy in the future. Of the current commercial and developmental solar cell technologies, the majority have natural resource limitations that prevent them from reaching a terawatt scale. These limitations include high energy input for crystalline-Si cells, limited material production for GaAs cells, and material scarcity for CdTe, CIGS, dye-sensitized, crystalline-Si, and thin-film Si cells. In this paper, we examine these limitations under the best scenarios for CdTe, CIGS, GaAs, dye-sensitized, and crystalline-Si solar cells. Without significant technological breakthroughs, these technologies combined would meet only a few percentage points (∼2%) of our energy demand in 2100.
The concerns about environmental impacts of photovoltaic (PV) power systems are growing with the increasing expectation of PV technologies. In this paper, three kinds of silicon-based PV modules, namely single-crystalline silicon (c-Si), polycrystalline silicon (poly-Si) and amorphous silicon (a-Si) PV modules, are evaluated from the viewpoint of their life-cycle. For the c-Si PV module it was assumed that off-grade silicon from semiconductor industries is used with existing production technologies. On the other hand, new technologies and the growth of production scale were presumed with respect to the poly-Si and a-Si PV modules.Our results show that c-Si PV modules have a shorter energy pay-back time than their expected lifetime and lower CO2 emission than the average CO2 emission calculated from the recent energy mix in Japan, even with present technologies. Furthermore the poly-Si and the a-Si PV modules with the near-future technologies give much reduction in energy pay-back times and CO2 emissions compared with the present c-Si PV modules. The reduction of glass use and the frameless design of the PV module may be effective means to decrease them more, although the lifetime of the PV module must be taken into account. © 1998 John Wiley & Sons, Ltd.
Nanjing Fangrun Materials, a recycling company in Jiangsu province that collects retired solar panels, said ​ the solar power industry was a ticking time bomb
  • Tian Min
Tian Min, general manager of Nanjing Fangrun Materials, a recycling company in Jiangsu province that collects retired solar panels, said ​ the solar power industry was a ticking time bomb."It will explode with full force in two or three decades and wreck the environment, if the estimate is correct," ig-environmental-problem
general manager of Nanjing Fangrun Materials, a recycling company in Jiangsu province that collects retired solar panels, said ​ the solar power industry was a ticking time bomb
  • Tian Min
Tian Min, general manager of Nanjing Fangrun Materials, a recycling company in Jiangsu province that collects retired solar panels, said ​ the solar power industry was a ticking time bomb."It will explode with full force in two or three decades and wreck the environment, if the estimate is correct,"
Material scarcity prevents most current solar cell technologies from reaching terawatt scales. (…) Scarce materials in solar cells include indium, gallium, tellurium, ruthenium, and silver. -Natural resource limitations to terawatt-scale solar cells "Material scarcity prevents most current solar cell technologies from reaching terawatt scales. (…) Scarce materials in solar cells include indium, gallium, tellurium, ruthenium, and silver. -Natural resource limitations to terawatt-scale solar cells."
Coal from El Cerrajon in Columbia ...for an annual production...of 110,000 tpy [of mg-Si] …would correspond to 605,000 tpy of carbon dioxide…The Environment Agency feels that…such exhaust would significantly increase Iceland's overall emissions
  • Thorsil
Thorsil (2015) "Metallurgical Grade Silicon Plant -Helguvík, Reykjanes municipality (Reykjanesbaer), Reykjanes peninsula, Iceland Environmental Impact Assessment (EIA) Capacity: 110,000 tons" (1) "Thorsil's initial assessment report was based on using...Coal from El Cerrajon in Columbia...for an annual production...of 110,000 tpy [of mg-Si] …would correspond to 605,000 tpy of carbon dioxide…The Environment Agency feels that…such exhaust would significantly increase Iceland's overall emissions" "Leaching from broken panels damaged during natural events -hail storms, tornadoes, hurricanes, earthquakes, etc. -and at decommissioning is a big concern."