Document:

<PAGE>
                                                                   EXHIBIT 10.30

                                SUPPLY AGREEMENT

between           Wacker Chemie AG
                  Hanns-Seidel-Platz 4
                  81737 Munich
                  Federal Republic of Germany

                  - hereinafter referred to as "WACKER" -

and               Tianwei Yingli New Energy Resources Co.Ltd
                  No. 3055 Middle Fuxing Road
                  Bao Ding City
                  P.R.China (071051)

                  - hereinafter referred to as "BUYER" -

PREAMBLE

BUYER has requirements for polycrystalline Silicon. WACKER is willing to supply
BUYER with polycrystalline Silicon.

Now, therefore, in consideration of the foregoing and the mutual premises
hereinafter contained, WACKER and BUYER agree as follows:

1.    PRODUCT

WACKER agrees to sell and deliver and BUYER agrees to purchase and take the
polycrystalline Silicon manufactured by WACKER as defined per specification set
forth in APPENDIX A (hereinafter referred to as "PRODUCT").

2.    QUANTITIES

2.1   The BUYER shall make the agreed prepayment according to the payment
      schedule set forth in APPENDIX A.

      WACKER shall sell and deliver to BUYER and BUYER will purchase and take
      from WACKER the annual quantities of PRODUCT set forth in APPENDIX A.

3.    PRICES / PAYMENT TERMS

3.1   The prices for the PRODUCT are set forth in APPENDIX A.

3.2   The prices under Section 3.1 above shall be firm until 31.12.2013 and only
      subject to change, if the relevant energy price index, defined in APPENDIX
      C, increases or decreases by more than 20%. The agreed prices will be
      adjusted by the rate (Euro/kg) as specified in the table in APPENDIX C.

<PAGE>
                                                                               2

3.3   WACKER shall invoice BUYER with each shipment of PRODUCT. BUYER shall pay
      such invoices net within [-]* ([-]*) days from the date of such invoices.

4.    DELIVERY

4.1   PRODUCT shall be delivered FOB German seaport (Incoterms 2000).

4.2   All deliveries of PRODUCT are subject to WACKER's General Conditions of
      Sale set forth in APPENDIX B and hereby made part of this Agreement,
      provided, however, that if there is any conflict between the terms of this
      Agreement and the said Conditions of Sale the terms of this Agreement
      shall prevail.

4.3   The agreed annual quantities for 2009 will be shipped in the second half
      of the calendar year 2009. The agreed annual quantities for the years
      2010, 2011,2012 and 2013 will be shipped in about equal monthly
      installments.

5.    QUALITY / INSPECTION AND TESTING

5.1   The PRODUCT supplied by WACKER shall conform to the specifications set
      forth in APPENDIX A.

5.2   It is understood and expressly agreed that the PRODUCT delivered by WACKER
      hereunder are PRODUCTS of technical quality only and BUYER is exclusively
      responsible for fitness for purpose, handling, use and application of the
      PRODUCT.

5.3   Upon receipt of each shipment of PRODUCT BUYER shall inspect the PRODUCT.
      Unless BUYER notifies WACKER within [-]* ([-]*) days after the arrival of
      the shipment at Buyer's premises or warehouse, that it does not conform to
      the quantity ordered or WACKER's certificate of quality does not conform
      to the specifications set forth in APPENDIX A, said shipment shall be
      deemed to have been delivered as ordered and WACKER's certificate of
      quality shall be deemed to conform to the specifications.

6.    WARRANTY/LIABILITY

6.1   WACKER warrants solely that the PRODUCT delivered shall conform to the
      specifications set forth in APPENDIX A. Except for the warranty provided
      above, WACKER disclaims any and all other express or implied warranties
      with respect to the PRODUCT, and any warranty of merchantability or
      fitness for a particular purpose is expressly disclaimed.

6.2   BUYER's exclusive remedy and WACKER's sole obligation for any claim or
      cause of action arising under this Agreement because of defective PRODUCT
      is expressly limited to either (i) the replacement of non-conforming
      PRODUCT or the repayment of the

--------
* INFORMATION INTENTIONALLY OMITTED; CONFIDENTIAL TREATMENT HAS BEEN REQUESTED
FOR SUCH INFORMATION, AND SUCH INFORMATION HAS BEEN SEPARATELY FILED WITH THE
SECURITIES AND EXCHANGE COMMISSION.
<PAGE>
                                                                               3

      purchase price of the respective quantity of PRODUCT; OR (ii) payment not
      to exceed the purchase price of the specific quantity of PRODUCT for which
      damages are claimed. Any remedy is subject to BUYER giving WACKER notice
      as provided for in Section 5.3.

6.3   The parties agree that the remedies provided in this Agreement are
      adequate and that except as provided for above, neither party shall be
      liable to the other, whether directly or by way of indemnity or
      contribution for special, incidental, consequential or other damages
      arising from the breach of any obligation hereunder or for any other
      reason whatsoever, including actions for tort, strict or product
      liability, patent or trademark infringement except as provided for herein.

7.    CONFIDENTIALITY

7.1   BUYER may use all the information disclosed by WACKER under this Agreement
      only for the purposes contemplated herein.

7.2   BUYER agrees to keep secret such information and to take the necessary
      measures to prevent any disclosure to third parties.

7.3   BUYER is responsible for assuring that secrecy is maintained by its
      employees and agents.

7.4   The secrecy obligation does not apply to information

      -  where BUYER can prove that is was known to BUYER prior to its receipt;

      -  which is or has become generally available to the public prior to its
         receipt;

      -  which is or has become generally available to the public without being
         the result of a breach of this Agreement;

      -  which is in accordance with information BUYER received or got access to
         from an entitled person without any obligation of secrecy;

      -  where WACKER approved the disclosure in a particular case in writing.

7.5   The secrecy obligation shall survive the term of this Agreement.

8.    SECURITY INTEREST

      BUYER hereby grants WACKER a continuing security interest in any PRODUCT
      and in the proceeds (including proceeds of sale or insurance) until the
      entire purchase price for the PRODUCT currently or previously sold to
      BUYER is paid and until all late payment interest, legal fees and expenses
      required to enforce WACKER's rights and any costs, expenses, taxes or
      other charges required to be paid by BUYER to WACKER have been paid in
      full. BUYER specifically agrees that WACKER may file one or more financing
      statements or other documents and take all necessary or appropriate in
      order to create, perfect, preserve or enforce WACKER's security interest
      in the PRODUCT pursuant to the Uniform Commercial Code and other
      applicable law, and hereby grants to WACKER a power of attorney to execute
      such statements or documents in BUYER's name. WACKER's reasonable costs
      and expenses (including, but not limited to, attorney's fees

<PAGE>
                                                                               4

      and expenses for pursuing, searching for, receiving, taking, keeping,
      storing, advertising and selling the PRODUCT shall be paid by BUYER who
      shall remain liable for any deficiency resulting from a sale of the
      PRODUCT and shall pay any deficiency forthwith on demand. The requirement
      of reasonable notice of sale shall be met if such notice is mailed and
      addressed to BUYER at its last address appearing on WACKER's records at
      least 30 days prior to the date of sale.

9.    FORCE MAJEURE

9.1   If either party should be prevented or restricted directly or indirectly
      by an event of Force Majeure as hereinafter defined from performing all or
      any of its obligations under this Agreement, the party so affected will be
      relieved of performance of its obligations hereunder during the period
      that such event and its consequences will continue, but only to the extent
      so prevented, and will not be liable for any delay or failure in the
      performance or any of its obligations hereunder or loss or damage whether
      direct, general, special or consequential which the other party may suffer
      due to or resulting from such delay or failure, provided always that
      prompt notice is given by the affected party to the unaffected party by
      facsimile or telephone of the occurrence of the event constituting the
      Force Majeure, together with details thereof and an estimate of the period
      of time for which it will continue.

9.2   The term Force Majeure shall include without limitation strike, labor
      dispute, lock out, fire, explosion, flood, war (accident), act of god or
      any other cause beyond the reasonable control of the affected party,
      whether similar or dissimilar to the causes enumerated above.

10.   ASSIGNMENT

      This Agreement or any part thereof is not assignable by either party
      without the prior written consent of the other party.

11.   ENTIRE AGREEMENT

11.1  This Agreement constitutes the whole agreement between the parties as to
      the subject matter thereof and no agreements, representations or
      warranties between the parties other than those set out herein are binding
      on the parties.

11.2  No waiver, alteration, or modification of this Agreement shall be valid
      unless made in writing and signed by authorized representatives of the
      parties.

12.   SEVERABILITY

      In the event, any provision of this Agreement shall be declared invalid,
      illegal or unenforceable, the validity, legality and enforceability of the
      remaining provisions shall not in any way be affected or impaired thereby.
<PAGE>
                                                                               5

13.   HEADINGS

      The headings of the articles of this Agreement are inserted for
      convenience only and shall not be deemed to constitute a part of this
      Agreement or to affect the construction hereof.

14.   DURATION / TERMINATION

14.1  This Agreement will commence on the 01.10.2006 and will endure for a
      defined period of 7 (seven) years and 3 (three) month.

15.   APPLICABLE LAW/ JURISDICTION

      This Agreement shall be construed and the legal relations between the
      parties hereto shall be determined in accordance with the laws of Germany;
      the application of the 1980 United Nations Convention on Contracts for the
      International Sale of Goods is expressly excluded.

Exclusive place of jurisdiction shall be Munich.

<TABLE>
<S>                    <C>                         <C>
Wacker Chemie AG                                   Tianwei Yingli New Energy Resources  Co. Ltd
WACKER POLYSILICON

Date: August 3, 2006                               Date: August 10, 2006

 /s/ Eward Shindlbeck  /s/ Reimund Huber           /s/ Liansheng Miao
---------------------  --------------------------  --------------------------------------------
Ewald Schindlbeck      Reimund Huber
President              Director Marketing & Sales
</TABLE>

<PAGE>
                                                                               6

APPENDIX A

SOLARQRADE POLYSILICON

SPECIFICATION PCL-NCS (B)

<Table>
<Caption>
Calendar year             2009       2010       2011       2012       2013
                          ------------------------------------------------------
<S>                       <C>        <C>        <C>        <C>        <C>
Annual quantity (kg)      [-]*       [-]*       [-]*       [-]*       [-]*
Price (EURO/kg)           [-]*       [-]*       [-]*       [-]*       [-]*
FOB German Seaport
</Table>

PREPAYMENT SCHEDULE

The BUYER will prepay the amount of [-]* Euro/kg for the total above agreed
contract quantity. The invoices, regarding deliveries up to the annual agreed
quantity, will be reduced by [-]* Euro/kg with each shipment. So WACKER's
invoice will state the above agreed prices on the invoice, but will make note,
that the BUYER has only to pay the invoice amount reduced by [-]* Euro/kg. [-]*
Euro/kg of the prepayment remain at WACKER.

Regarding to the agreed annual quantities the total prepayment amount of Euro
[-]* ([-]*) has to be paid according to the following schedule on the account of
Wacker Chemie AG:

October 2nd, 2006 Euro [-]* ([-]*)

In case the BUYER does fail to take the full amount of the agreed annual
quantity in one respective calendar year, WACKER does not have to repay the not
absorbed outstanding prepayment (regarding the respective calendar year), BUYER
also doesn't have the right to set this prepayment against deliveries of the
following year.

--------
* INFORMATION INTENTIONALLY OMITTED; CONFIDENTIAL TREATMENT HAS BEEN REQUESTED
FOR SUCH INFORMATION, AND SUCH INFORMATION HAS BEEN SEPARATELY FILED WITH THE
SECURITIES AND EXCHANGE COMMISSION.
<PAGE>
                                                                               7

                                   APPENDIX B

                           GENERAL CONDITIONS OF SALE

1.    GENERALLY:

All our supplies and services as well as all contracts concluded with us are
exclusively subject to the following conditions of sale. Terms of the Purchaser
which contradict or which deviate from our sales terms and which are not
expressly recognised by us are not valid even if we do not expressly object to
them. Where a continuing business relationship exists, all future contracts,
supplies and services are also subject to our conditions of sale.

2.    OFFER, CONCLUSION OF CONTRACT:

Our offers are subject to change and non-binding. Orders are only valid if
confirmed by us in writing or if recognised by us through the act of delivery.
Any additional verbal agreements, supplements and modifications are also only
valid if confirmed in writing.

3.    DELIVERY, DEFAULT:

3.1   Unless otherwise agreed, any dates quoted for delivery are non-binding.

3.2   We are entitled to make partial deliveries as far as the Purchaser must
      reasonably accept this in the circumstances of an individual case. The
      corresponding invoices issued are payable without regard to whether
      complete delivery has been made.

3.3   In the event delivery is delayed, the Purchaser may set us a reasonable
      grace period with the notice that he rejects the acceptance of the
      delivery item after expiry of the grace period. After the expiry of the
      grace period, the Purchaser is entitled to cancel the contract of sale
      through written notice or to request damages instead of performance.

      At our request the Purchaser is obligated to state within a reasonable
      period whether he cancels the contract due to delay in delivery, seeks
      damages instead of performance or insists on performance.

3.4   Our liability is set forth in para. 9. Furthermore in the event of slight
      negligence, our liability is limited to the invoice value of the
      respective delivery item.

4.    RETURN OF LOAN PACKAGING:

In the event of delayed return (meaning in the event normal uploading times are
exceeded) of loading equipment, loading banks and other loan packaging we
reserve the right to charge the Purchaser for the costs incurred by us.

5.    PRICES:

5.1   Unless otherwise expressly agreed, prices are quoted "ex works" excluding
      packaging and plus delivery and shipping costs as well as plus any
      applicable Value Added Tax.
<PAGE>
                                                                               8

5.2   The prices valid on the day of dispatch shall apply.

Should the latter be higher than the contractual price, the purchaser is
entitled to cancel the contract with regard to the quantities still to be
delivered. Cancellation shall be made within 14 days after notification of said
price increase.

6.    PAYMENT:

6.1   The payment shall be made in Euro to one of our bank accounts indicated on
      the reverse side.

6.2   Should Purchaser be in arrears with payment, interest for default shall be
      due and payable at 12%, but at least 8% above the respective base interest
      rate. We reserve the right to claim further damages. If the interest we
      claim is higher than the statutory interest for delayed payment, the
      Purchaser has the right to demonstrate lower damages just as we have the
      right to show that greater damages were incurred.

6.3   Should Purchaser be in arrears with payment or should there be reasonable
      doubts as to Purchaser's solvency or credit rating, we are -- without
      prejudice to our other rights -- entitled to require payment in advance
      for deliveries not yet made, and to require immediate payment of all our
      claims arising from the business relation.

6.4   Bills of exchange and cheques shall be accepted upon separate agreement
      and only by way of payment. All expenses incurred in this regard shall be
      borne by the Purchaser.

6.5   Only uncontested or legally proved claims shall entitle the Purchaser to
      set-off or withhold payment.

7.    FORCE MAJEURE:

Events of Force Majeure, in particular strikes, lock outs, operation or
transport interruptions, including at our suppliers, shall suspend the
contractual obligations of each party for the period of the disturbance and to
the extent of its effects. Should the delays caused exceed a period of 6 weeks,
both parties shall be entitled to cancel the contract, with respect to the
contractual performance affected by such delays. No other claims exist.

8.    QUALITY:

8.1   All our data, especially data relating to product suitability, processing
      and use, as well as to technical support, have been compiled to the best
      of our knowledge. The Purchaser, however, must still perform his own
      inspections and preliminary trials.

8.2   The Purchaser undertakes to examine the goods immediately after delivery
      with respect to any defects concerning quality and suitability of purpose
      and object to ascertainable defects. Sample testing shall also be
      performed if this can be reasonably expected of the Purchaser. Failure to
      proceed in aforesaid manner shall result in the goods being regarded as
      accepted.
<PAGE>
                                                                               9

8.3   Complaints must be made within 8 days after receipt of the goods. In case
      of hidden faults, however, complaints are to be made immediately on
      discovery, within one year after receipt at the very latest. Said claims
      shall only be taken into consideration if and when made in writing and
      with the relevant documentation attached. To comply with the time limit it
      shall be sufficient if the complaint is sent in good time.

8.4   We are not liable on the basis of public statements by us, the
      manufacturer or his agents, if we were not aware of the statement or were
      not required to have knowledge thereof, the statement was already
      corrected at the time of the purchase decision or the Purchaser cannot
      show that the statement influenced his purchase decision.

8.5   We are not liable for defects which only marginally reduce the value or
      the suitability of the object. A marginal defect exists in particular if
      the defect can be removed by the Purchaser himself with insignificant
      effort.

8.6   If the Purchaser requests replacement performance due to a defect, we may
      choose whether we remove the defect ourselves or deliver a defect-free
      object as a replacement. The right to reduce the price or cancel the
      contract in the event of unsuccessful replacement performance shall remain
      unaffected.

8.7   Where complaints are justified, the goods may only be returned to us at
      our expense if after we receive notice of the defect we do not offer to
      collect or dispose of the goods.

8.8   If increased costs arise because the Purchaser has transferred the goods
      to a place other than his commercial place of business, we shall charge
      the Purchaser for the increased costs in connection with the remedying of
      the defect, unless the transfer corresponds to the designated use of the
      object.

8.9   Damage and claims for reimbursement of expenses shall remain unaffected as
      far as not excluded by para. 9.

8.10  All claims due to a defect are subject to a limitation period of one year
      after delivery of the object. No warranty is made for used objects. The
      statutory limitation period for objects which are used for a building
      structure in accordance with their usual manner of use, and which cause
      the defectiveness thereof, shall remain unaffected.

8.11  The rights of the Purchaser under Sections 478, 479 German Civil Code
      remain unaffected.

9.    LIABILITY:

Our liability is excluded, regardless of the legal grounds.

This shall not apply in the event of intentional actions or gross negligence by
us or our legal representatives or agents or in the event of breach of material
contractual duties.

In the event of a slightly negligent breach of material contractual duties, our
liability is limited to twice the invoice value of the respective delivery item.
For damages due to delayed performance para. 3.4 shall also apply. Our liability
for damages due to injury to life, the body or health, the

<PAGE>
                                                                              10

liability based on a guarantee and under mandatory statutory provisions, in
particular the Product Liability Act, remain unaffected.

10.   RESERVATION OF OWNERSHIP:

10.1  The goods that have been sold remain our sole property until all
      outstanding debts arising from the business connection with the Purchaser
      have been paid in full. The Purchaser has power of disposal of the
      purchased goods in the ordinary course of business, or he may process the
      goods until revocation by us.

10.2  Reservation of ownership and power of disposal, as laid down in clause
      10.1, also apply to the full value of the manufactured goods produced by
      processing, mixing and blending or combining our goods. In each case we
      qualify as the manufacturer. In cases where the goods are processed, mixed
      and blended or combined with those of a third party, and where the
      reservation of the latter continues to apply, then we acquire joint
      ownership in proportion to the invoice value of those processed goods. If
      security rights of a third party are in fact or in law below that share,
      the difference will be to our benefit.

10.3  If the Purchaser resells our goods to third parties he hereby assigns the
      entire resulting payment claim -- or in the amount of our joint share
      therein (see para. 10.2) -- to us. In the event the parties agree on a
      current account, the respective balance amounts shall be assigned.
      However, the Purchaser shall be entitled to collect such payment claim on
      our behalf until we revoke such right or until his payments are
      discontinued. The Purchaser is only authorized to make assignment of these
      claims -- even only for the purpose of collection by way of factoring --
      with our express written consent.

10.4  The Purchaser shall immediately give notice to us if any third party
      raises any claim with respect to such goods or claims which are owned by
      us.

10.5  If the value of the collateral exceeds our accounts receivable by more
      than 20% then we will release collateral on demand and at our discretion.

10.6  We are also entitled to take back goods on the basis of the reservation of
      title, even if we have not previously cancelled the contract. If products
      are taken back by way of the exercise of the reservation of ownership,
      this shall not constitute cancellation of the contract.

10.7  If the laws of the country in which the goods are located after delivery
      do not permit the Vendor to retain the title to said goods, but allow the
      retention of other similar rights to the delivery item, the Purchaser
      shall provide us with such other equivalent right. The Purchaser
      undertakes to assist us in the fulfilment of any form requirements
      necessary for such purpose.

11.   PLACE OF FULFILMENT, APPLICABLE LAW AND JURISDICTION:

11.1  The originating point of the goods shall, in each case, be the place of
      fulfilment for the delivery. Munich shall be the place of fulfilment for
      payment.
<PAGE>
                                                                              11

11.2  Exclusively the laws of the Federal Republic of Germany shall apply
      between the parties. The application of the 1980 United Nations Convention
      on Contracts for the International Sale of Goods is expressly excluded.

11.3  If the Purchaser is a merchant or does not have a general place of
      jurisdiction in Germany, the place of jurisdiction is Munich. We shall,
      however, have the right to also bring a claim against the Purchaser at his
      general place of jurisdiction.

Munich, 15th May 2002
<PAGE>
                                                                              12

APPENDIX C, PAGE 1 OF 2

Relevant Energy Price Index:

"BAFA Grenzubergangspreis" for natural gas

Source:

http://www.bmwi.de/BMWi/Navigation/Energie/Energiestatistiken/
energiestatistiken,did=53736.html

Evaluation periods:

-     Arithmetic mean value out of 6 months

-     April to September for price adjustment of 1st half of the following year

-     October to March for price adjustment of 2nd half of year

-     Basis evaluation period: April 2006 - September 2006

Price Adjustment Table:

CB ... Index value of Basis evaluation period
CN ... Index value of New evaluation period

<Table>
<Caption>
CN/CB (%)          Price Adjustment
                   EURO / kg
<S>                <C>
< - 60 %                 [-]*
< - 40 %                 [-]*
< - 20 %                 [-]*

> + 20 %                 [-]*
> + 40 %                 [-]*
> + 60 %                 [-]*
> + 80%                  [-]*
etc.                     etc.
</Table>

On the following example for the calculation of the price adjustment the
procedure is explained in more detail.

--------
* INFORMATION INTENTIONALLY OMITTED; CONFIDENTIAL TREATMENT HAS BEEN REQUESTED
FOR SUCH INFORMATION, AND SUCH INFORMATION HAS BEEN SEPARATELY FILED WITH THE
SECURITIES AND EXCHANGE COMMISSION.

<PAGE>
                                                                              13

APPENDIX C, PAGE 2 OF 2

EXAMPLE FOR CALCULATION OF PRICE ADJUSTMENT

[FLOW CHART]<PAGE>
                                                                               .
                                                                               .
                                                                               .
                                                                   Exhibit 10.31

                                                                     Translation

                                PURCHASE CONTRACT

<TABLE>
<S>                                                                      <C>
Party A: Baoding Tianwei Yingli New Energy Resources Co., Ltd.           Contract No.: YLXG070418
Party B: Sichuan Xinguang Silicon Science and Technology Co., Ltd.       Date of Execution: April 10, 2007
</TABLE>

After friendly discussions, in accordance with the Contract Law of People's
Republic of China, Party A and Party B hereby enter into this contract (this
"Contract") in Baoding, Hebei Province.

I.       Product Description, Specification, Quantity, Unit Price and Total
         Price:

<Table>
<Caption>
     Product         Specification         Time of        Quantity      Unit Price (per         Total Price
   Description                            Delivery                       kilogram, tax
                                                                           included)
------------------ ------------------- ---------------- ------------- --------------------- ---------------------
<S>                <C>                 <C>              <C>           <C>                   <C>
   Solar Grade         Please see        By December      200 Tons            1650          RMB 330,000,000 (In
     Silicon           Exhibit I          31, 2007                                             Words): Three
  Washing-free          (Product                                                             Hundred and Thirty
                     Specification                                                                Million
                    Description) for                                                           (Tax Included)
                        details.
</Table>

<Table>
<Caption>
     Product             Specification            Time of       Quantity       Unit Price (per kilogram, tax
   Description                                   Delivery                                included)
------------------ -------------------------- ---------------- ------------ -------------------------------------
<S>                <C>                 <C>    <C>              <C>          <C>
   Solar Grade       Please see Exhibit I       By December    1,000 Tons   Fluctuates with the Market Price in
     Silicon        (Product Specification       31, 2008                                   2008
  Washing-free     Description) for details.
</Table>

II.      Transportation and Packaging Criteria:

         The seller shall be responsible for delivery of the goods to Baoding
         Tianwei Yingli New Energy.

         Packing Criteria: Plastic Packaging: 5 kilograms/package.

III.     Time of Delivery:

         The shipment shall be made within 30 days after the Contract has been
         signed;

         All goods to be delivered in 2007 shall be delivered in batch to the
         place of delivery designated by the purchaser by December 31, 2007.

IV.      Acceptance Method:

         1.    An acceptance test shall be made with respect to the brand,
               quantity, type, specification and defects in appearance within 15
               days after the goods have been delivered to the purchaser's
               plant.

                                       1
<PAGE>

         2.    Acceptance Method: Sample Test.

         3.    In the event of any dispute in connection with the acceptance,
               the relevant State inspection authority shall conduct a test for
               the products in accordance with the inspection criteria and
               methods for solar grade silicon washing-free materials,

V.       Terms of Payment:

         100% Advance Payment: the seller shall give notice to the purchaser at
         least 7 days prior to delivery, and the purchaser shall make advance
         payment for all goods in this batch within 7 days; and the seller shall
         issue the VAT invoice (at a tax rate of 17%).

VI.      Liability for Breach

         In the event that either party breaches this Contract during the term
         hereof, the breaching party shall be liable for all responsibilities,
         including, but not limited to, actual losses, and litigation fees,
         attorney's fees and travel fees in connection with such liability.
         During the effective term hereof, Party A and Party B shall fully
         perform their obligations hereunder. In the event that either party
         fails to perform this Contract for any special reason, it shall give
         written notice to the other party hereto at least 90 days in advance;
         provided that the obligations of the parties hereto may only be revoked
         upon mutual agreement after friendly discussions with the other party
         hereto; and provided further that the liquidated damages shall be
         settled by the parties hereto through consultation.

VII.     Anything not addressed herein shall be solved by the parties through
         consultation. If no settlement can be reached through such
         consultation, the parties agree that either party may bring such
         dispute for judgment before the People's Court of competent
         jurisdiction where this Contract is executed.

VIII.    This Contract shall be executed in two (2) copies with each of the
         Party A and Party B holding one (1) copy, all of which shall become
         effective upon execution by the parties (a faxed copy of which shall be
         valid).

<Table>
<S>                 <C>                                   <C>               <C>
Purchaser:          Baoding Tianwei Yingli New Energy     Seller:           Sichuan Xinguang Silicon Science
                    Resources Co., Ltd. (Seal)                              and Technology Co., Ltd. (Seal)
Representative:     /s/Zhao Zhiqiang                      Representative:   /s/Chen Shaoping
Address:            3055 Fuxingzhong Road, Baoding,       Address:          Leshan High&New Tech Industrial
                    Heibei                                                  Development Zone, Leshan
Telephone:          0312-8929869                          Telephone:        0833-2596403
Fax:                0312-8929800                          Fax:              0833-2596408
</Table>

                                       2
<PAGE>

                             SUPPLEMENTAL AGREEMENT

Party A:   Baoding Tianwei Yingli New Energy Resources Co., Ltd.

Party B:   Sichuan Xinguang Silicon Science and Technology Co., Ltd.

Date:      April 10, 2007

With respect to the purchase contract entered into by Party A and Party B on
April 10, 2007 (Contract No: YLXG070418) (the "Purchase Contract"), the parties
hereby further agree as follows:

The quantity of the goods to be delivered as set forth in Article I of the
Purchase Contract (Contract No: YLXG070418) shall be subject to the actual
quantity produced by Party B, and shall not be contractually binding upon Party
B. The parties shall have the friendly cooperation spirit, and Party B shall use
its best endeavors to assist Party A with the purchase of polycrystalline
silicon.

<TABLE>
<S>                 <C>                                   <C>               <C>
Party A:            Baoding Tianwei Yingli New Energy     Party B:          Sichuan Xinguang Silicon Science
                    Resources Co., Ltd. (Seal)                              and Technology Co., Ltd. (Seal)
Representative:     /s/Zhao Zhiqiang                      Representative:   /s/Chen Shaoping
Address:            3055 Fuxingzhong Road, Baoding,       Address:          Leshan High&New Tech Industrial
                    Heibei                                                  Development Zone, Leshan
Telephone:          0312-8929869                          Telephone:        0833-2596403
Fax:                0312-8929800                          Fax:              0833-2596408
</Table>

                                       3
<PAGE>

                                    Exhibit I

                        Product Specification Description

1.       Phosphorus test: type N, resistivity >100 OMEGA.cm; Boron test: type
         P, > 1000 OMEGA.cm; minority carriers lifetime >100 OM s; oxygen
         content: less than 10 to the 17th power/cm cubed; carbon content: less
         than 10 to the 16th power/cm cubed

2.       There shall be no oxidizing layer or insoluble substance.

3.       Chunk: diameter >40mm

                                       4

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