Annual report pursuant to Section 13 and 15(d)

Property, plant and equipment - Summary of Property and Equipment (Details)

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Property, plant and equipment - Summary of Property and Equipment (Details) - USD ($)
12 Months Ended
Dec. 31, 2017
Dec. 31, 2016
Property, Plant and Equipment [Line Items]    
Property and equipment, gross $ 14,443,685 $ 1,691,523
Less: accumulated depreciation and amortization (2,177,974) (1,174,380)
Net property, plant and equipment $ 12,265,711 517,143
Minimum    
Property, Plant and Equipment [Line Items]    
Useful life - years 3 years  
Maximum    
Property, Plant and Equipment [Line Items]    
Useful life - years 15 years  
Energy systems    
Property, Plant and Equipment [Line Items]    
Property and equipment, gross $ 12,466,642 0
Energy systems | Minimum    
Property, Plant and Equipment [Line Items]    
Useful life - years 1 year  
Energy systems | Maximum    
Property, Plant and Equipment [Line Items]    
Useful life - years 15 years  
Machinery and Equipment    
Property, Plant and Equipment [Line Items]    
Property and equipment, gross $ 1,215,951 1,009,893
Machinery and Equipment | Minimum    
Property, Plant and Equipment [Line Items]    
Useful life - years 5 years  
Machinery and Equipment | Maximum    
Property, Plant and Equipment [Line Items]    
Useful life - years 7 years  
Furniture and Fixtures    
Property, Plant and Equipment [Line Items]    
Property and equipment, gross $ 205,320 141,874
Useful life - years 5 years  
Computer software    
Property, Plant and Equipment [Line Items]    
Property and equipment, gross $ 115,253 102,415
Computer software | Minimum    
Property, Plant and Equipment [Line Items]    
Useful life - years 3 years  
Computer software | Maximum    
Property, Plant and Equipment [Line Items]    
Useful life - years 5 years  
Leasehold improvements    
Property, Plant and Equipment [Line Items]    
Property and equipment, gross [1] $ 440,519 $ 437,341
[1] Lesser of estimated useful life of asset or lease term