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Summary of significant accounting policies - Revenue by Product Line and Services (Details) (USD $)
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9 Months Ended | 12 Months Ended | |||
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Sep. 30, 2013
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Sep. 30, 2012
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Dec. 31, 2012
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Dec. 31, 2011
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Dec. 31, 2010
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| Revenue by Producks and Services [Line Items] | |||||
| Products | $ 3,639,974 | $ 4,191,439 | $ 7,453,222 | $ 4,569,113 | $ 5,543,605 |
| Services | 6,103,044 | 5,498,545 | 7,800,750 | 6,496,097 | 5,767,624 |
| Total revenues | 9,743,018 | 9,689,984 | 15,253,972 | 11,065,210 | 11,311,229 |
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Cogeneration
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| Revenue by Producks and Services [Line Items] | |||||
| Products | 2,441,740 | 2,687,769 | 5,791,412 | 2,737,161 | 4,977,595 |
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Chiller
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| Revenue by Producks and Services [Line Items] | |||||
| Products | $ 1,198,234 | $ 1,503,670 | $ 1,661,810 | $ 1,831,952 | $ 566,010 |
| X | ||||||||||
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- Details
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| X | ||||||||||
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- Definition
Aggregate revenue during the period from the sale of goods in the normal course of business, after deducting returns, allowances and discounts. Reference 1: http://www.xbrl.org/2003/role/presentationRef
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| X | ||||||||||
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- Definition
Total revenue from sale of goods and services rendered during the reporting period, in the normal course of business, reduced by sales returns and allowances, and sales discounts. Reference 1: http://www.xbrl.org/2003/role/presentationRef
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| X | ||||||||||
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- Definition
Aggregate revenue during the period from services rendered in the normal course of business, after deducting allowances and discounts. Reference 1: http://www.xbrl.org/2003/role/presentationRef
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