Annual report pursuant to Section 13 and 15(d)

Summary of significant accounting policies - Agreement with Digital Energy Corp. (Details)

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Summary of significant accounting policies - Agreement with Digital Energy Corp. (Details) (Financial guarantee, USD $)
Oct. 26, 2011
Financial guarantee
 
Guarantor Obligations [Line Items]  
Letter of credit outstanding $ 180,000
Certificate of deposit securing letter of credit 180,000
Promissory note receivable amount $ 180,000
Promissory note receivable, stated interest rate 6.00%