Annual report pursuant to Section 13 and 15(d)

Summary of significant accounting policies - Revenue (Details)

v3.20.4
Summary of significant accounting policies - Revenue (Details) - USD ($)
 12 Months Ended
Dec. 31, 2020
Dec. 31, 2019
Disaggregation of Revenue [Line Items]    
Revenue $ 28,254,579 $ 33,426,448
Payment term on product sales 30 days  
Payment Term on Energy Production Contract Invoices 30 days  
Unbilled revenue recognized $ 2,000,000.0  
Revenue billed that was recognized in previous periods 3,200,000  
Deferred revenue recognized 1,512,670  
Remaining performance obligations $ 1,200,000  
Performance obligation recognized over next 24 months (percent) 96.00%  
Performance obligation recognized over next 12 months (percent) 6.00%  
Performance obligation recognized in subsequent 12 months (percent) 90.00%  
Products    
Disaggregation of Revenue [Line Items]    
Revenue $ 10,534,096 12,977,896
Installation Services [Member]    
Disaggregation of Revenue [Line Items]    
Revenue 5,805,497 7,505,964
Maintenance Service [Member]    
Disaggregation of Revenue [Line Items]    
Revenue 10,077,805 9,801,754
Energy Production    
Disaggregation of Revenue [Line Items]    
Revenue $ 1,837,181 3,140,834
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 $ 1,837,181 3,140,834
Energy Production | Products    
Disaggregation of Revenue [Line Items]    
Revenue 0 0
Energy Production | Installation Services [Member]    
Disaggregation of Revenue [Line Items]    
Revenue 0 0
Energy Production | Maintenance Service [Member]    
Disaggregation of Revenue [Line Items]    
Revenue 0 0
Energy Production | Energy Production    
Disaggregation of Revenue [Line Items]    
Revenue 1,837,181 3,140,834
Product and Service    
Disaggregation of Revenue [Line Items]    
Revenue 26,817,142 30,895,144
Product and Service | Products    
Disaggregation of Revenue [Line Items]    
Revenue 10,534,096 12,977,896
Product and Service | Installation Services [Member]    
Disaggregation of Revenue [Line Items]    
Revenue 5,805,497 7,505,964
Product and Service | Maintenance Service [Member]    
Disaggregation of Revenue [Line Items]    
Revenue 10,077,805 9,801,754
Product and Service | Energy Production    
Disaggregation of Revenue [Line Items]    
Revenue 0 0
General and Administrative Expense    
Disaggregation of Revenue [Line Items]    
Shipping and handling expenses 418,180 480,966
Operating Segments    
Disaggregation of Revenue [Line Items]    
Revenue 28,254,579 33,426,448
Operating Segments | Energy Production    
Disaggregation of Revenue [Line Items]    
Revenue 1,837,181 3,140,834
Operating Segments | Product and Service    
Disaggregation of Revenue [Line Items]    
Revenue $ 26,417,398 $ 30,285,614