4. INVESTMENT IN SALES-TYPE LEASES, NET

Under sales-type leases, Xi’an TCH leases the following systems: (i) BMPG systems to Pucheng Phase I and II (15 and 11 year terms, respectively); (ii) BMPG systems to Shenqiu Phase I (11-year term); and (iii) Shenqiu Phase II (9.5-year term). In addition, as of March 31, 2017, Erdos TCH leased power and steam generating systems from waste heat from metal refining to Erdos (five systems) for a term of twenty years. The components of the net investment in sales-type leases as of March 31, 2017 and December 31, 2016 are as follows:

	2017			2016
Total future minimum lease payments receivable	$	218,176,104		$	217,470,913
Less: executory cost		(66,443,813	)		(66,444,519	)
Less: unearned interest income		(33,638,086	)		(35,312,473	)
Less: realized interest income but not yet received		(6,450,202	)		(4,621,490	)
Investment in sales-type leases, net		111,644,003			111,092,431
Current portion		11,034,452			9,385,453
Noncurrent portion	$	100,609,551		$	101,706,978

As of March 31, 2017, the future minimum rentals to be received on non-cancelable sales-type leases by years are as follows:

2018	$	31,176,332
2019		19,038,721
2020		19,038,721
2021		20,600,876
2022		20,671,489
Thereafter		107,649,965
Total	$	218,176,104