Annual report pursuant to Section 13 and 15(d)

Stockholders' equity - Stock Option Activity (Details)

v3.22.0.1
Stockholders' equity - Stock Option Activity (Details) - USD ($)
12 Months Ended
Dec. 31, 2021
Dec. 31, 2020
Exercise Price Per Share [Abstract]    
Outstanding, Exercise Price Lower Range Limit (usd per share) $ 0.71 $ 0.71
Outstanding, Exercise Price Upper Range Limit (usd per share) 10.33 $ 10.33
Granted, Exercise Price Lower Range Limit (usd per share) 1.75  
Canceled and Forfeited, Exercise Price Lower Range Limit (usd per share) 0.08  
Canceled and Forfeited, Exercise Price Upper Range Limit (usd per share) $ 4.50  
Tecogen    
Stock Options Outstanding [Roll Forward]    
Beginning (shares) 2,496,242  
Granted (shares) 258,000 1,440,000
Exercised (shares) 0 (1,000)
Canceled and forfeited (shares) (367,400)  
Ending (shares) 2,386,842 2,496,242
Exercisable (shares) 719,633  
Vested and expected to vest (shares) 2,136,731  
Weighted Average Exercise Price [Roll Forward]    
Beginning (usd per share) $ 1.94  
Granted (usd per share) 1.75  
Canceled and forfeited (usd per share) 2.70  
Ending (usd per share) 1.81 $ 1.94
Vested and expected to vest (usd per share) 1.89  
Exercisable (usd per share) $ 3.53  
Share-based Compensation Arrangement by Share-based Payment Award, Equity Instruments Other than Options, Additional Disclosures [Abstract]    
Outstanding, Aggregate Intrinsic Value $ 697,935 $ 731,744
Exercisable, Aggregate Intrinsic Value 71,785  
Vested and expected to vest, Aggregate Intrinsic Value $ 604,012  
Exercise Price Per Share [Abstract]    
Granted, Exercise Price Lower Range Limit (usd per share) $ 1.75 $ 0.71
Granted, Exercise Price Upper Range Limit (usd per share)   $ 0.78
Stock Options | Tecogen    
Share-based Compensation Arrangement by Share-based Payment Award, Equity Instruments Other than Options, Additional Disclosures [Abstract]    
Outstanding, Weighted Average Remaining Life 7 years 6 months 21 days 7 years 4 months 13 days