The solar bulls were on parade this week, due in no small part to the annual Solar Power International Expo out in Los Angeles. I didn't make it to the show, as I was busy covering the Value Investing Congress here in New York, but plenty of positive commentary certainly made its way to my computer screen.

Fool colleague Travis Hoium already hit upon one of the biggest reveals from the SPI show: a film from 3M (NYSE: MMM) that's intended to replace glass in the manufacture of thin film modules. I agree with Travis that the potential of roll-to-roll module manufacturing has potentially revolutionary implications. That was a big reason I largely bought into the hype surrounding Nanosolar, which we haven't heard a peep from since Rambus veteran Geoff Tate took the reins in March.

3M, which I spotted entering the solar market earlier this year, is one of the most innovative industrial engineering firms in the world, and I have a great deal of confidence in its efforts here. Other industry titans speaking about expanding in solar this week were DuPont (NYSE: DD) and General Electric (NYSE: GE).

We've watched DuPont tackle the solar space with its encapsulants, pastes, and other materials. The company is now talking about entering the building-integrated photovoltaics market, which would pit it against rival Dow Chemical (NYSE: DOW) and its solar shingle.

GE, with a pair of thin film module offerings, calls solar "the next big phase" in its renewable energy push. I think GE's leading position in the domestic wind turbine market foreshadows how big of a presence this behemoth will have in the solar industry within a few years.

This entry by GE could cause discomfort for leading thin film player First Solar (Nasdaq: FSLR) down the road, but for now, the company is on a tear. Following last week's announcement of a big pile of 2011 orders, First Solar revealed plans to build two more manufacturing facilities: one in Vietnam and one in the United States. The additions will add 500 megawatts of capacity, which is now headed to 2.7 gigawatts in 2012.

LDK Solar (NYSE: LDK) shares took off Monday after the  company raised its outlook for the recently completed third quarter. Revenue, wafer shipments, and module shipments are all expected to come in ahead of previous guidance. Investors again bid up the stock by more than 10% on Wednesday, on no discernible news. That enthusiasm is cooling off today -- the whole solar sector, as represented by the Guggenheim Solar (NYSE: TAN) ETF, is off more than 2% today -- but LDK shares are still up roughly 20% on the week. Longer-term, you know where I stand on that one. With favorable state financing, however, this could just be the beginning of a powerful run by one of China's favored sons.

3M is a Motley Fool Inside Value selection. First Solar is a Motley Fool Rule Breakers recommendation. Try any of our Foolish newsletter services free for 30 days.

Fool contributor Toby Shute doesn't have a position in any company mentioned. Check out his CAPS profile or follow his articles using Twitter or RSS. The Motley Fool has a disclosure policy.

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