December 31,
2018

December 31,
2017

Raw material prepayments for equipment production

$

2,686,314

$

916,210

Construction material prepayments

2,776,638

1,037,438

Advances to construction subcontractors

405,203

428,334

5,868,155

2,381,882

Less: allowances for doubtful accounts

(871,030

)

(534,245

)

Less: Advances to suppliers, net, related party (Note 15)

(947,557

)

-

Advances to suppliers, net, third parties

$

4,049,568

$

1,847,637