Printing Solar Profitability
Solar installations are rocketing worldwide as solar electricity becomes cheaper than electricity from fossil fuels – it’s already happened in 105 countries. This is the tipping point where economics takes over from altruism and solar PV becomes a serious part of the global energy mix.
If you’re a cell manufacturer, though, dropping prices are a double-edged sword: strong demand is good, but you must continuously lower costs by improving your manufacturing processes in order to be profitable.
So, in a fiercely competitive industry, how is this done? A great example of how cell manufacturers can boost profitability is an emerging technique called “double printing”. I first wrote about double printing three years ago, when the technique was in its infancy. Today, it’s rapidly being adopted by cell manufacturers around the world.
Repeatability is also a strong lever: every time you make a substandard cell the bottom line suffers. After all, it costs the same to make a cell whether it works well or not. And obviously, minimizing the amount of raw material in each cell is beneficial.
After the silicon wafer itself, the largest material cost is silver paste, about 140mg of which is used to form the network of contact lines on the front of most cells today. Clearly, using less paste is a good thing. But the contacts are expensive in another way: by taking up real estate on the front of the wafer that would otherwise be harvesting light energy, they also cost efficiency.
Sadly, you can’t just print thinner lines: thinner lines have higher resistance and they’re difficult to print, which can result in broken lines, called “interrupts” which result in lower efficiency cells that will probably be scrapped.
What you can do, though, is print narrower, taller lines by a technique called “double printing”, where a second set of lines is printed on top of the first. This isn’t an easy thing to do, though: it requires precise alignment of the wafer and printing head to ensure the second set of lines is exactly on top of the first.
The benefits are substantial: Esatto improves process control so much that our customers can double print lines just 50μm wide with much better repeatability, leading to better yield. In addition, double printing reduces paste consumption by 20% and boosts absolute cell efficiency by as much as 0.2% (e.g. from 17% to 17.2% efficiency). That might not sound like a lot, but combined, these benefits can add up to a gross profit increase of a whopping 15%.
Fortunately, Applied’s Baccini screen printers were all designed to be upgradeable, which means that most of the world’s cell manufacturing capacity can be upgraded with a very rapid return on investment.
The proof is in the field: three of the world’s top ten module manufacturers are converting their production lines to add double printing. Pretty soon, double-printed lines will be everywhere.
Applied predicts double-printed lines will be everywhere in the near future, helping to fulfill the increasingly-important need for low-cost, rapidly implemented techniques that offer an immediate boost to the bottom line.
(If you’d like to learn about the latest advances in double printing technology, Applied is presenting next week at one of the solar industry’s biggest conferences, EU PVSEC in Frankfurt, Germany. You should drop in if you happen to be in the neighborhood.)
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