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 June 30, 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 June 30, 2017 and December 31, 2016 are as follows:

	2017			2016
Total future minimum lease payments receivable	$	220,128,619		$	217,470,913
Less: executory cost		(66,859,949	)		(66,444,519	)
Less: unearned interest income		(32,395,946	)		(35,312,473	)
Less: realized interest income but not yet received		(7,695,920	)		(4,621,490	)
Investment in sales-type leases, net		113,176,804			111,092,431
Current portion		12,552,397			9,385,453
Noncurrent portion	$	100,624,407		$	101,706,978

As of June 30, 2017, the future minimum rentals to be received on non-cancelable sales-type leases by years are as follows:

2018	$	34,528,557
2019		19,389,739
2020		19,389,739
2021		20,939,061
2022		21,942,083
Thereafter		103,939,440
Total	$	220,128,619