Almost a year ago, First Solar (Nasdaq: FSLR) invested$25 million in SolarCity, the exclusive residential installer of the company's thin film panels. Business seems to be booming for Solar City, which has doubled the solar fund it operates in partnership with US Bancorp (NYSE: USB). On Tuesday, the companies announced that they're looking to finance $100 million in solar projects in 2009. That's pretty impressive.

Also on Tuesday, ProLogis unveiled its renewable energy initiative and said it has teamed up with solar project developer Recurrent Energy to develop 4.8 megawatts of Spanish power projects by the middle of next year. Reuters reported that the companies would use "flexible thin-film solar laminates," which possibly points to Energy Conversion Devices (Nasdaq: ENER) as the supplier, though there are other start-ups working in this area.

One such company is Ascent Solar (Nasdaq: ASTI), which has been the focus of some incredibly volatile trading lately. The shares zoomed higher on a series of announcements over the past few weeks, including supply agreements with Provo Craft and TurtleEnergy. The company also signed a cooperation agreement with Energy Technologies to pursue military applications. Ascent followed up with a public offering of 4.6 million shares, priced at a 14% discount to the previous day's closing price. Investors did not respond enthusiastically.

Elsewhere in the solar space, Suntech Power (NYSE: STP) connected China's first utility-scale (i.e., 10-megawatt) solar power plant into the grid this week, which highlights just how tiny the current solar footprint is in the country. That's going to change, of course, thanks to companies like First Solar, with its planned two-gigawattplant.

Speaking of First Solar, it will soon enter the S&P 500, replacing Wyeth . A lot more investors are suddenly going to have a stake in the solar player's success, however infinitesimal, through the index.

Rounding out the week, Trina Solar (NYSE: TSL) extended its supply relationship with GCL and made further headwayin the Italian market with a 73-megawatt supply deal. Canadian Solar (Nasdaq: CSIQ) teamed up with inverter ace SatCon Technology , and ECD implemented a poison pill that it creatively dubbed a "tax benefits preservation plan."

This article was originally published as This Week in Solaron Fool.com

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