Annual report pursuant to Section 13 and 15(d)

Project Assets (Details)

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Project Assets (Details) (USD $)
 12 Months Ended
Dec. 31, 2012
Dec. 31, 2011
Dec. 31, 2010
Property, Plant and Equipment [Line Items]      
Property, Plant and Equipment, Other, Net $ 207,274,982 $ 177,854,734  
Grant awards received on project assets 6,023,767 6,695,711  
Deferred grant income 7,590,730 6,024,099  
Rebates from utility company 1,287,000 0  
Project asset depreciation 11,229,380 9,701,399 9,634,891
Renewal Energy Program
      
Property, Plant and Equipment [Line Items]      
Project assets 253,699,036 213,564,483  
Less - accumulated depreciation and amortization 46,424,054 35,709,749  
Property, Plant and Equipment, Other, Net $ 207,274,982 $ 177,854,734