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As the solar industry continues to report impressive growth rates each year, companies with proven solar cells at market price are not having much difficulty finding customers for everything they can produce. This also applies to new technologies such as thin-film solar cells.
Investment in thin-film CIGS-(Copper, Indium, Gallium, and Selenium) based solar cell manufacturers has been very robust, with companies such as MiaSole, Global Solar, NanoSolar, Solyndra and others receiving significant funding to support their growth. This indicates confidence in thin-film CIGS technology.
Thin film is a process where material from a target source is coated onto a substrate via a plasma field. These thin films are minuscule — angstroms to microns thick — and therefore use a very small amount of material to achieve most coating thickness goals. Silicon solar cells use a wafer of Silicon (Si) — a 10 story building in thickness compared to thin films that are just microns thick.
The benefit to using a CIGS process is that it has the potential to dramatically reduce the cost of manufacturing with a high production yield. That means that when the CIGS thin-film process is perfected, the cost of CIGS solar cells will likely come down. [Nanosolar has announced their CIGS cells at an eye popping $.99 /Watt. They have thrown down the financial gauntlet to all other solar cell manufacturers.]
Solar cell production cost is dependent on the cost of the raw materials and the recent silicon shortage is driving material costs up for silicon-based solar cells. The shortage is compounded by the ever increasing demand for silicon in semiconductor industries. This shortage is providing additional incentive for investment in alternative thin-film solar cell technologies. In an attempt to determine some actual costs, I discovered that all solar thin-film companies view their costs as a closely guarded secret. They felt that revealing costs would give competitors an understanding of price elasticity (margin) and therefore they didn't want to talk about it.
Thin-film solar companies must balance target material quality and cost to find the most advantageous combination. Generally, higher quality target material costs more, sometimes significantly higher depending on the material. Material cost is very important because it determines the price of the solar cell and manufacturer's profitability. The lower the production cost, the lower the price. And the lower the price of solar cells the more businesses and home owners can afford to purchase.
Of the companies developing CIGS solar cells, three categorical approaches have emerged so far: using evaporation, nano particles, and thin film targets. How these manufacturers develop their processes in their respective categories will be the greatest area of technical differentiation and in large determine CIGS cell efficiency and cost.
To date, CIGS solar cell production has only made it from the lab to the production floor with evaporation. Each process strategy has limitations in part governed by the material form factor. For example, material for evaporation (the material is heated up until it vaporizes) is easy to obtain and use, however, the process itself can be inefficient in material usage, slow to coat substrates and difficult to control. Soft metals such as Gallium and Indium can be expensive (and difficult) to powderize into nano form, or at least into a usable form for thin-film particle placement in correct stoichiometry.
But there is a process that can lower costs much more quickly and thrust CIGS to the forefront of the PV market. Physical Vapor Deposition (PVD) or "sputtering" is fast, and perhaps ideal for CIGS cell production, however, usable target materials have proven elusive in the past. Targets are made up of material (in this case CuInGaSe or CuInGa) that is attached to a reusable backplate installed in a PVD system.
High density CIG targets are necessary because they have the potential to enable faster development and production of CIGS cell lines. Lower density material will have microscopic voids in the material that can be filled with contaminates such as oxygen or other things that may be present in the manufacturing process.
After years of research and development, I am happy to say that casted CIG targets are now available. Casted targets are most dense targets currently available. High density targets are important because they enable thin-film technicians greater control the plasma field that determines the thickness and consistency of the film.
Obviously, CIGS cell manufacturers need to purchase raw materials at the best possible price and the company that is able to use material the most effectively will have a cost advantage. When target materials are used, the actual utilization can range anywhere from 25% to 75% depending on the target type and system design and operation. This means that only a percentage of the total material on a target is used, the remainder must be machined off and reclaimed (melted down to be re-used).
In our three years of research and development in CIG target casting technology we have found that once casted targets are spent, roughly 95% to 98% of the material can be reclaimed (depending on the target condition). In addition, material loss in the casting process is generally less than 3%. Using casted CIG material should yield upwards of 90% total material utilization when you consider the ability to remove CIG from spent targets and cast it again.
What all this means is that when a CIGS cell manufacturer's investment in raw material should yield 90% real total usage of material in the chamber. In this way a company that invests $100,000 in raw material (Cu, In, Ga) for casting targets can get $90,000+ of that material directly in process. The only difference is an additional casting fee on spent material. In other terms, every 4th to 5th target can be made from reclaimed material. This model of casting services and target consumption should enable more attractive CIGS solar cell prices in the future.
If production costs are key to enabling lower solar cell prices and wider adoption of solar power, then I believe CIGS has an advantage and PVD using casted CIG targets is going to be a very large player in the manufacture of solar cells.
Greg Howard is the Vice President of Sputtering Materials, Inc., a material science company that specializes in PVD materials and is based in Reno, NV. Mr. Howard has over 13 years of experience in high tech industries and has published market research studies, white papers, and other research as an industry analyst. As VP, he now oversees company operations and research and development.
The information and views expressed in this article are those of the author and not necessarily those of RenewableEnergyWorld.com or the companies that advertise on its Web site and other publications.
While the thin films may offer the lowest $/W at the module level, the total installed cost, is what most customers really care about.
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I just;
http://www.google.com/search?hl=en&q=asteroid+indium
and it's quite a page! I think the indium here came from the dino-killer...
then I read something about carbon sheets...
http://www.tgdaily.com/content/view/35379/113/
According to Linjie Zhi of the Max Planck Institute, "It is very stable in the face of heat and acidic conditions, which makes fabrication much easier." Some problems remain, however..." "... Their goal is to get a single atomic layer of graphene. If they could achieve that, they'd have a nearly 100% transparent material, one which is completely suitable for replacing indium.
That's funny, I was just thinking about "what if the asteroids contained indium" when writing earlier... I read a book called "Mining the Sky" by John S. Lewis and he lists "...platinum group...". Ya, every element is within the grasp of robotic asteroid mining. He says that just one 2 km wide M class asteroid would bring in about 20 trillion dollars (and pay for the quadrillions needed at todays space costs)!
But what needs heavy subsidizing is ALL aspects of RE, if only as much as the fossils... so that humanity COULD actually mine the asteroid that will one day slam into us
Any discussion of "long term" supplies of Indium should also recognize reserves off-planet in the asteroids and elsewhere, unless we define "long tem" as less than a decade.
This tiny little dirtball we live on today is not now and can never be our only source of raw materials and energy.
If CIGS cells are a good and economical solution for some of the energy demand on Earth, and maybe for solar power satellites orbiting Earth, people can find ways to obtain more access to more Indium on or off Earth.
Do you have a link to the article you quoted, it looks interesting. It is the first I have heard of having only a 10 year supply of Indium left in the world. It is true that ITO is used in LCDs and plasma screens as the TCO. There are replacements for ITO as a TCO such as AZO (Alumina doped ZnO). I understand that there is a difference in character between the two films. AZO may be a suitable ITO replacement for TCOs. This may lighten demand by that sector if supply is significantly constricted in the future.
It is encouraging that the thin film people have realised that dollars per watt delivered is more important than watts per square metre.
When they can coat solar cells onto long run roofing this technology will sweep the world. The combined savings of not having to put conventional roofing on your house before putting the panels on top and the likelyhood that the solar panels will be cheaper than conventional solar panels (per watt delivered) will suddenly make the whole exercise worthwhile. I doubt if any new house will be ever built again with roofing that is not a solar panel as well.
The article I saw said this:
It is estimated that there is only a 10 years supply of indium left on the entire planet. Indium is a crucial resource in creating solar cells, LCD and other devices which must have transparent electrodes to carry out their function. However, a new discovery related to single atomic layer sheets of carbon (graphene) could prove to be a better replacement, according to researchers at the Max Planck Institute for Polymer Research in Germany.
Graphene will not help GIGS cells where the electronic nature of In is needed, but from the above comments, maybe the "estimate" given is wrong?
Side note: The "sliver cell" is a single crystal silicon cell uses 10% of the silicon of regular cells, but still gets 18% efficiency. CIGS is currently around 15% I have heard.
2,600 metric tons of indium worldwide researve, 5,700 for "researve base", from
http://minerals.usgs.gov/minerals/pubs/commodity/indium/indiumcs96.pdf
that was in 1996, the same deal shows 2,800 and 6,000 respectively during 07
http://minerals.usgs.gov/minerals/pubs/commodity/indium/indiumcs07.pdf
The USGS also says that it is about three time more abundant than silver. But it is definately dependent on zinc, that production oversees is rising and thus feedstocks are being reduced...
We'd be lucky to get a thousand sq miles of solar fields out of this one (at one millionth of a meter thick).
fireofenergy
I (kinda) know the efficiency of my little 3.5 - 5 volt 50 - 90 mA "cells". I've seen them on the web labeled as "copper indium..." also.
55 x 56 mm of CIGS material inbedded in glass puts out about 90 mA at 4.72 volts during winter at 2:30 with perfectly clear, 6,500 ft altitude.
If sunlight = 1,000 watts per square meter, what is the efficiency of mine? I did some math and came to the conclusion of 13.8%. This is in "perfect" sunlight conditions of "clear winter at 6,700 feet altitude at Big Bear, CA". Got to be close enough for a conservative estimate...
The reason I said kinda is because each cell puts out a different reading, some as low as only 3 volts and 40 mA, but most are of the above.
I agree, very little is said about cell efficiency, emphasis has been placed on cost/W. This is likely an indication the cell efficiencies are low. I believe the world record CIGS cell is 19.4% efficient, perhaps no where near what will be produced in early production. I don't believe Nanosolar has published cell efficiency as of yet.
You are right, I was unaware that Solyndra was using a solution-based plating technology. This is a significant 4th method to manufacture CIGS solar cells. I am curious what Solyndra projects their cost structure to be.
Interesting,
When I research indium, no doubt the potential is there with adequate supplies, but not at current time as there are just not enough companies mining for it. Yes, it is a byproduct of zinc mining, so the only suppliers will be zinc mining companies, so this narrows the supply line significantly.
Given the huge investment and envirnmental impact studies required to even start mining in most areas these days, I don't think indium is the answer for decades. This is the typical scenario of being caught in between a rock and a hardplace, or what comes first, the mining or the demand. When solar comapanies are faced with their decision to move into manufacturing, they have to have supplies to support it, and mining will not expend time and money without demand, so I just don't see indium as the answer, no matter how cost effective it is, it will take decades to bring it to market in my opinion.
Low-Cost-WiFi.com
About solar shingles: The problem is shadows. If one cell is shadowed the entire cell sting shuts down. Current cannot get through the shadowed cell. Bypass dides allow the string to continue to operate, at lower voltage. With several strings in parallel (my home has 4) to operate at peak power you reduce the voltage on ALL the strings just because one string has one cell in shadow. A chimney, power pole, or tree casting a shadow across the entire array effecively shuts it all down. You have to pick just that part of the roof that sees few shadows for the panels. This lets out the option of just covering the entire roof with solar shingles.
We would need something else as well, like many DC to DC converters scattered throughout the array, which ups the cost.
Here are 2:
http://www.tgdaily.com/content/view/35379/113/
http://www.dailytech.com/New+Material+Promises+to+Save+LCD+Solar+Power+Industry/article10143.htm
However, neither give their source.
As hinted at by Eugene, there will be big structural impacts on the industry as well. For example, right now professional installers have the installation end of the consumer value chain sewn up. Some of this is due to the inherent need for electrical skills, but most is due to the size and sheer weight of solar panels, and the complexity of the balance of system. And yes, at some point every new home and residential building will have solar cells installed upon construction. But with the CIGS revolution, the whole DIY market for existing homes opens up in a dramatic way -- particularly as the movement to more modular and pre-engineered balance of system components gains momentum. (www.diygreenenergy.com)
While there has always been speculation about whether there is enough Indium and other uniformity issues surrounding the manufacture of the CIGS cell, I don't see discussion here about the packaging problems around non glass applications of the technnology. With CIGS being 100% moisture intolerant, there is material sciences issue to solve before there can be a 20 year warranty for this promising technology.
Does anyone know what the highest operating temperature is for these thin film cells? If a cell could operate at higher temperatures than silicon cells, this would open the possibility of developing combination electrical and thermal hybrid systems. It would be great if we could find a way to use the 80% or more of the solar energy that is not used in photovoltaics.
You bring up an excellent point. If demand for solar cell (of all types) continues to be steep for the foreseeable future, I agree that prices will likely stay high in the market's current iteration. If there are new products (or product categories), such as those pointed out by Wayne Floyd, that target consumers directly (or the home improver), cost dynamics for consumers can change. Home owners that install their own solar panel solution will likely save a lot from a do-it-yourself solar power home improvement kit. While this is speculation, it will likely happen, assuredly so if the likes of Home Depot and Lowe’s start to carry such products.
1. Which is a efficient technology amongst Plasma vapor deposition or Screen printing (Nanosolar, ISET, etc)?
To date Nanosolar has not yet announced or discussed cell efficiency (at least I am not aware of it). Rumor/speculation has been that it is low. PVD CIGS cell developers are also not yet discussing efficiency. I think that we will hear announcements of cell efficiency as both screen printing and PVD companies are pressured to do so.
2. Will efficiency have direct impact if Steel/Al foils are used instead of glass?
This is a question best answered by the thin film cell manufacturers themselves. I wish they would pipe in and give their feedback.
I am fully convinced on CIGS cells offering cost-effective solutions in long-term. Indium shortage is not an issue at all. Its too long to think of it.
Can you provide me more insight on the following 2 aspects:
1. Whcih is a efficient technology amongst Plasma vapor deposition or Screen printing (Nanosolar, ISET, etc)?
2. Will efficieny have direct impact if Steel/Al foils are used instead of glass?
Jaideep Malaviya (Jai)
info@malaviya.in
While CIGS companies like Ascent Solar represent one important aspect of our thin-film solar future, don’t forget that we can get the economies of thin film AND the abundance and non-toxicity of silicon with amorphous silicon thin film solar products available now in commercial quantities from Energy Conversion Devices and others.
Robert Bernal stated: "We'd be lucky to get a thousand sq miles of solar fields". Using 2 square meters as a benchmark panel size, 1,000 sq miles would require 1.28 BILLION modules to cover. CIGS is about 1/2 as efficient as pure silicon modules. Degredation averages roughly 0.5% per year over a 20 year period. Nanosloer offers a 25 year warranty. How do I buy shares in Nanosolar?
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