Solar Power Industry Efficiency Opportunities

Posted on May 16th, 2011 by

Dr. Charles Gay Ph.D., President of Applied Solar, discusses how his company is looking at ways to increase solar power production. This is the second part of a two part series.

Full Transcription:

Q1: How close is the solar power industry to achieving a production price of $1-a-watt?
Charlie Gay: Most of the folks that I talk to today working with crystalline silicon, say that’s coming within the next two years. Most people have roadmaps, whether it’s with thin film or crystalline silicon, that get well below that dollar-a-watt terms of manufacturing cost. Where a lot of emphasis is going today is actually on improving efficiency. While the cost of the solar panel has come down by 20% for every cumulative doubling, the cost of the balance of system has only come down about 12-15% for every cumulative doubling. Now, one of the gating items in the cost reduction of an installed system really is related to all that other stuff. The steel, the cement, the copper wire; all of those commodities tend to get more pricey every year that goes by. But with the efficiency, there’s almost two thirds of the cost of a system is, what we say, are area dependent costs: the costs of the steel, the structure to hold the modules and the foundation made of cement. So, we’re working not only to drive down the cost, but to drive up the efficiency and that helps not just minimize cost for a watt at the module, but it minimizes the installed positive system bring down the cost per kilowatt-hour. So, our emphasis in applied materials is really on advanced technologies that enhance not only cost reduction but this big boost in efficiency. And there’s a lot of room for improvement. So, the exciting thing here is, we’re really only beginning to see the beginning of this explosion of ideas come into practice in the manufacturing factories that we serve.
Q2: What areas of solar production do you feel offer the better opportunity for better efficiency or stronger output?
Charlie Gay: Probably the biggest single opportunity is in what we call passivation; minimizing the chance that a positive and a negative charge will accidentally collide with each other rather than get to the wire to go to a power device. The most frequent place where that collision could happen is on the skin of the solar cell. As the electron gets out of the silicon and is moving towards the wire,   to take it away, it ends up maybe hitting a damaged area on the wafer or an imperfection or an impurity. The kind of tools that we make are adapted from the equipment that is used in the integrated circuit business, in many cases, to be operated on a very bigger, much larger scale at 3000 wafers an hour rather than 50 wafers an hour; and get that same quality of control, of uniformity and at the atomic level interface between the layer of the insulator that goes on top of the solar cells and the solar cell itself. So, today I would say that over 50% of the losses in a cell are related to passivation and being able to improve on it. That, by far, in a way is to the lowest hanging fruit. It’s all the most challenging though.
Charlie Gay: What’s nice is the models for the solar cell in itself have been very well refined over the course of the last fifty five years, but particularly in the last few years as it’s become easier to characterize what goes on at the atomic level, what goes on at interfaces. And, being able to then, say, take that loss and probably reduce it by 80% or so. We have very good ideas on what to do and how to do it and how to measure it and how to commercialize it. And so that’s one of several different things we’re doing. Our core business is in cutting off wafers and of putting metal patterns on cells are not standing still either. In the wafering business, much of what we’re working on is optimizing that wire that originated the steel belted radial tires. First, to have some structure in the wire that helps spread more cutting fluid, more silicon carbide abrasive particles through the silicon in order to cut faster, and ultimately we see being able to use diamond-plated wire that reciprocates back and forth multiple times to cut even faster with even cleaner surfaces. In the case of our printing processes, our metallization, much of the foundations, the core technology, is built around what are called linear motors for being able to position a silicon wafer on a table or putting a metal pattern on it. Now we’ve expanded that concept into cleaner motors so that a table roughly three feet by three feet in area can carry moving shuttles on it and each of the shuttles is sort of like going to Disneyland here, each shuttle has got a wafer. That wafer can go to a location with very high precision within about ten microns of alignment, which is about one quarter the diameter of the human hair, to get some physical sense of this.  So that the patterns and the precision of alignment possible on a solar cell allow for minimal loss of light bouncing off the solar cell and allow for maximizing the benefit of films like passivation layers.
Q3: What is the correlation between the probability of imperfection with cutting faster and thinner? How are you tackling this?
Charlie Gay: That’s a very good question. The cutting faster of a brittle material, you’d think may scratch it more, and like scratching abusive glass that’s where you want to break it. In the case of a silicon wafer, one of the attributes of going to these advanced wires is the surface actually is smoother. So, we, in the rare occasions where mother nature’s gulf streams is working for us, we get the benefit of going fast but having fewer surface loss, and the smoother the surface, the easier it is to implement these advanced patterning techniques that improve the performance of the solar cell, minimize these weak combination losses by minimizing how big the metal surface is that touches the silicon wafer. In much the same way, being able to handle the wafer through that printing station, the goal has been to develop the techniques to take thin wafers from the saw, not break them when we get to the next process step, but actually improve the mechanical yields by using optical alignment techniques. Today’s everyday laptop has amazing computer power for being able to identify images way down in very fine pixel size of a few microns so that it’s not necessary to touch the edge of a wafer to line it up. The edge of the wafer, because it’s so thin is the most fragile, brittle part of the wafer. And this shuttle concept allows for the wafers to move around. We don’t have to align it by touching the edges and we can handle wafers that are almost half as thick as the standard wafer today.
Charlie Gay: There’s some great engineering problems and great physics problems. There’s a great optics problem and some chemistry problems, too. But all of these kind of weed itself together with addressing our customer’s problems of scaling at China’s speed, and being able to match the speed of growth of our manufacturing customers, whether they are in China or end up in our backyard. We tend to forget that the cost of labor in China is actually increasing fairly rapidly. And the benefits of automation that we can bring to the tool more or less cancel out any advantages of low cost labor in one region and simultaneously improve over-all factory yield in a region where the laborer and the brainpower maybe more expensive but fewer brains are needed and most of the brains are in the form of computers that are on the factory floor.
Q4: How did you get into the solar industry? And why are you doing what you’re doing?
Charlie Gay: I’ve been in this business for thirty six years. I entered at end of the first oil embargo in 1974. And, at the time, I sort of have this epiphany. I was ready to graduate from school wondering what I was going to do with my wonderful degree, and I saw all of these “A” students going into nuclear engineering. And I thought, you know, one of the things maybe that’s possible here is to see that the cost of solar could come down with scale and some of the ideas that were floating about. In 1974, there was a conference held in Cherry Hill, New jersey, where a few of the folks who had some experience with solar said “You know, if we could work at it, we could get the cost of solar down to $.50 a watt.” And at that level, it would be directly competitive with grid power everywhere. And even just using today’s dollars, we’re getting close to $.50 a watt, and we’re getting very close to good power everywhere. What really inspired me to do this was the recognition that one third of the people on the planet didn’t have electricity. The easiest way to get electricity to those folks was with the solar panel. You could start small. You can have a light. You can have a radio, a TV, a fan, and gradually build that up. Having grown up on a farm, it was easy to relate to a lot of the people living without electricity. We had a wood burning stove in our kitchen. And so, the thought of being able to help improve the lives of others and enjoy doing my job at the same time was like the ultimate combination of a win-win and I’m happy that I chose it.

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