Annual report pursuant to Section 13 and 15(d)

Summary of significant accounting policies - Revenue (Details)

v3.20.1
Summary of significant accounting policies - Revenue (Details) - USD ($)
 12 Months Ended
Dec. 31, 2019
Dec. 31, 2018
Disaggregation of Revenue [Line Items]    
Revenue $ 33,426,448 $ 35,883,684
Payment term on product sales 30 days  
Payment Term on Energy Production Contract Invoices 30 days  
Unbilled revenue recognized $ 2,700,000  
Revenue billed that was recognized in previous periods 2,200,000  
Deferred revenue recognized 2,526,206  
Remaining performance obligations $ 2,800,000  
Performance obligation recognized over next 24 months (percent) 98.00%  
Performance obligation recognized over next 12 months (percent) 3.00%  
Performance obligation recognized in subsequent 12 months (percent) 95.00%  
Products    
Disaggregation of Revenue [Line Items]    
Revenue $ 12,977,896 12,624,867
Installation Services [Member]    
Disaggregation of Revenue [Line Items]    
Revenue 7,505,964 8,097,473
Maintenance Service [Member]    
Disaggregation of Revenue [Line Items]    
Revenue 9,801,754 8,761,818
Energy Production    
Disaggregation of Revenue [Line Items]    
Revenue $ 3,140,834 6,399,526
Light Installation [Member]    
Disaggregation of Revenue [Line Items]    
Payment Term on Installation Services 30 days  
Turnkey Installation [Member]    
Disaggregation of Revenue [Line Items]    
Payment Term on Installation Services 30 days  
Energy Production    
Disaggregation of Revenue [Line Items]    
Revenue $ 3,140,834 6,399,526
Energy Production | Products    
Disaggregation of Revenue [Line Items]    
Revenue   0
Energy Production | Installation Services [Member]    
Disaggregation of Revenue [Line Items]    
Revenue   0
Energy Production | Maintenance Service [Member]    
Disaggregation of Revenue [Line Items]    
Revenue   0
Energy Production | Energy Production    
Disaggregation of Revenue [Line Items]    
Revenue 3,140,834 6,399,526
Product and Service    
Disaggregation of Revenue [Line Items]    
Revenue 30,895,144 30,695,306
Product and Service | Products    
Disaggregation of Revenue [Line Items]    
Revenue 12,977,896 12,624,867
Product and Service | Installation Services [Member]    
Disaggregation of Revenue [Line Items]    
Revenue 7,505,964 8,097,473
Product and Service | Maintenance Service [Member]    
Disaggregation of Revenue [Line Items]    
Revenue 9,801,754 8,761,818
Product and Service | Energy Production    
Disaggregation of Revenue [Line Items]    
Revenue   0
General and Administrative Expense    
Disaggregation of Revenue [Line Items]    
Shipping and handling expenses 480,966 447,546
Operating Segments    
Disaggregation of Revenue [Line Items]    
Revenue 33,426,448 35,883,684
Operating Segments | Energy Production    
Disaggregation of Revenue [Line Items]    
Revenue 3,140,834 6,399,526
Operating Segments | Product and Service    
Disaggregation of Revenue [Line Items]    
Revenue $ 30,285,614 $ 29,484,158