Cost of revenues and general and administrative expenses (Details) - USD ($)	12 Months Ended
	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Cost of revenues and general and administrative expenses [Line Items]
Cost of Revenue	$ 33,624,821	$ 33,807,982	$ 42,086,978
Electricity [Member]
Cost of revenues and general and administrative expenses [Line Items]
Cost of Revenue	9,037,347	10,675,287	14,631,638
Depreciation [Member]
Cost of revenues and general and administrative expenses [Line Items]
Cost of Revenue	5,355,529	5,270,454	5,077,293
Fuel oil [Member]
Cost of revenues and general and administrative expenses [Line Items]
Cost of Revenue	4,210,542	4,974,421	8,726,195
Employee costs [Member]
Cost of revenues and general and administrative expenses [Line Items]
Cost of Revenue	5,541,983	4,287,783	4,274,007
Cost of plant sales [Member]
Cost of revenues and general and administrative expenses [Line Items]
Cost of Revenue	142,151	878,396	1,470,045
Maintenance [Member]
Cost of revenues and general and administrative expenses [Line Items]
Cost of Revenue	3,545,269	3,436,736	3,131,947
Retail license royalties [Member]
Cost of revenues and general and administrative expenses [Line Items]
Cost of Revenue	1,528,914	1,427,073	1,405,067
Insurance [Member]
Cost of revenues and general and administrative expenses [Line Items]
Cost of Revenue	992,374	1,187,097	1,397,799
Materials [Member]
Cost of revenues and general and administrative expenses [Line Items]
Cost of Revenue	1,280,794	0	0
Other [Member]
Cost of revenues and general and administrative expenses [Line Items]
Cost of Revenue	$ 1,989,918	$ 1,670,735	$ 1,972,987