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 December 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 December 31, 2017 and 2016 are as follows:

	2017 (Restated)			2016 (Restated)
Total future minimum lease payments receivable	$	99,155,214		$	96,886,262
Less: executory cost		(6,360,901	)		(6,215,345	)
Less: unearned interest		(23,730,094	)		(28,785,901	)
Less: realized interest income but not yet received		(9,619,278	)		(4,621,490	)
Less: bad debt allowance for net investment receivable		(1,802,822	)
Investment in sales-type leases, net		57,642,119			57,263,526
Current portion		11,531,745			8,103,583
Noncurrent portion	$	46,110,374		$	49,161,943

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

2018	$	31,067,306
2019		13,039,087
2020		13,039,087
2021		13,039,087
2022		11,523,982
Thereafter		17,446,665
Total	$	99,155,214