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) BMPG systems to Shenqiu Phase II (9.5-year term). In addition, as of June 30, 2018, 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, 2018 and December 31, 2017 are as follows:

	2018 (Restated)			2017 (Restated)
Total future minimum lease payments receivable	$	94,187,347		$	99,155,214
Less: executory cost		(6,042,207	)		(6,360,901	)
Less: unearned interest		(21,854,351	)		(23,730,094	)
Less: realized interest income but not yet received		(9,241,978	)		(9,619,278	)
Less: allowance for net investment receivable		(2,586,479	)		(1,802,822	)
Investment in sales-type leases, net		54,462,332			57,642,119
Current portion		12,220,921			11,531,745
Noncurrent portion	$	42,241,411		$	46,110,374

As of June 30, 2018, the future minimum rentals to be received on non-cancelable sales-type leases by years are as follows:

2019	$	33,385,727
2020		12,876,704
2021		12,876,704
2022		12,876,704
2023		8,387,994
Thereafter		13,783,514
Total	$	94,187,347