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The following HTML text is provided to enhance online readability. Many aspects of typography translate only awkwardly to HTML. Please use the page image as the authoritative form to ensure accuracy. Page 126 a really well understood effect, but under light soaking, the system loses some of its efficiency in the first six months of operation. So, the films start out at 15% and then in six months they drop down to 10 or 12%. This particular degradation mechanism is somewhat understood, but how to control it is not. Dave Cole: Is moisture an issue in temperate zones where it is not always dry? Is water or humidity a factor? John Turner: Water is not an issue with current sealing technologies for single-crystal silicon cells. Dave Cole: Is that true for the amorphous silica also? John Turner: It is the same for amorphous silica. Amorphous silicon uses the same sealing technique. Dave Cole: What do you mean by “sealing technique”? John Turner: Typically, the silicon is deposited either on glass or on stainless steel and sealed with a plastic. The plastic is called ethoxybenzoic acid (EBA), but I've forgotten what that means now. It is a cover that seals everything up. It lasts about 20 years. The degradation of EBA is really what limits the lifetime of silicon solar cells. David Keith, Carnegie Mellon: I think I heard you say that the use of water in electrolysis to make hydrogen would lead to some water shortages. Is that correct? John Turner: It is going to be an issue if you only have water— David Keith: I don't get it. I mean about a meter of water a year falls in the typical temperate zones. That means on each hectare you get 104 square cubic meters of water per year. John Turner: Yes. David Keith: Yet the amount of water that you need to make hydrogen, assuming you— John Turner: Pretty small. David Keith: It is of order 10 cubic meters. So, there is a difference of 103. John Turner: Right, but it is the culmination that makes the difference. Water is used for food, people and industry. If you add hydrogen production to that, there may be a problem. If you take it by itself, you are absolutely right. David Keith: It is down by three orders of magnitude. John Turner: It is going to be an issue.
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