Exhibit 4.73
 SUPPLEMENTAL AGREEMENT
 on
 THE POWER PURCHASE AND SALE
CONTRACT
 FOR
 THE YEAR OF 2010
 (Contract Number: De Dian Si 2010-011 )
 BINGLANGJIANG POWER STATION AND BINGLANGJIANG
EXPANDED POWER STATION
 Dehong Power Supply Co., Ltd.
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supplemental agreement on the power purchase and sale
contract for the year of 2010
 Agreement
 I.
    
    The Parties hereby determine that the annual contractual on-grid electricity output for the
year of 2010 is 150,000,000 kwh.
 1.
    
    Considering the annual overhaul plan of the units and the regularity of power
supply and demand, the contractual on-grid electricity output allocated for each month
is set out as follows:
 January:
    
    6,540,000
kwh;February:
    
    5,580,000
kwh;March:
    
    5,030,000
kwh;April:
    
    4,900,000
kwh;May:
    
    6,790,000
kwh;June:
    
    14,060,000
kwh;July:
    
    17,500,000
kwh;August:
    
    19,500,000
kwh;September:
    
    19,500,000
kwh;October:
    
    19,000,000
kwh;November:
    
    18,000,000
kwh;December:
    
    13,600,000
kwh;
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2.
    
    On-grid Tariff during Commercial Operation Period

Upon being approved by the competent price regulatory authority of the local government,
the on-grid tariff for the units of the Power Plant during the commercial operation
period shall be implemented according to the document with the number of [2008] No.
611; in case of any change to the governmental tariff policy, the new policy shall
prevail. The reactive compensation tariff shall be: RMB 0.02/kwh.3.
    
    Under the normal production condition of the silicon smelting enterprises of our
prefecture, the Power Purchaser shall ensure eighty five percent (85%) of the
contractual electricity output of the Power Station could be dispatched out. In case of
abnormal production condition of the silicon smelting enterprises of our prefecture, the
dispatching shall be carried out on the principle of the same proportion for the same
installed capacity. The surplus electricity output generated not in compliance with the
dispatching instructions shall be deemed as invalid electricity output and shall not be
settled.4.
    
    In August of each year after having concluded the Power Purchase and Sale
Contract, after friendly consultations, the Parties may appropriately adjust the annual
contractual on-grid electricity output of that year and the contractual on-grid
electricity output for the rest months based on the actual situation of power supply and
demand, and reach a written agreement; prior to the end of November of each year, the
Parties shall consult with each other to determine the annual contractual on-grid
electricity output for the next year, and enter into a Power Purchase and Sale Contract
for the next year before the end of December.
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5.
    
    The Power Seller shall strictly comply with the dispatching instructions and
provide with the production and operation data upon the request of the Power Purchaser,
such as: the daily electricity output, the overhaul plan, etc.
 II.
    
    Equivalent Available FactorThe condition precedent for the Power Purchaser to purchase from the Power Seller the
electricity output not less than the annual contractual on-grid electricity output is that:
the planned equivalent available factor of the generator units determined in accordance with
the annual contractual on-grid electricity output of that year shall reach 44% or
above. In the event the actual equivalent available factor of the generator units fails to
reach the aforesaid requirement, the Power Purchaser shall be entitled to reduce its annual
contractual on-grid electricity output corresponding to the deficient proportion of the
equivalent available factor.III.
    
    The valid term of this Agreement shall be from January 1, 2010 to December 31, 2010.
 four (4) one (1) two (2)
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Power Purchaser : Dehong Power Supply Co., Ltd.
   /s/ Cun Shijian
 Power Seller: Yunnan Huabang Electric Power Development Co., Ltd.
   /s/ Li Xiaozun
 March 31, 2010
 Mangshi
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