o

Rule 13d-1(b)

x

Rule 13d-1(c)

o

Rule 13d-1(d)

CUSIP No. 72919P103

13G

(1)

Names of Reporting Persons
Capital Ventures International

(2)

Check the Appropriate Box if a Member of a Group (See Instructions)

(a)

o

(b)

o

(3)

SEC Use Only

(4)

Citizenship or Place of Organization
Cayman Islands

Number of
Shares
Beneficially
Owned by
Each
Reporting
Person With:

(5)

Sole Voting Power
0

(6)

Shared Voting Power **
4,000,000

(7)

Sole Dispositive Power
0

(8)

Shared Dispositive Power **
4,000,000

(9)

Aggregate Amount Beneficially Owned by Each Reporting Person
4,000,000

(10)

Check Box if the Aggregate Amount in Row (9) Excludes Certain Shares (See Instructions)  o

(11)

Percent of Class Represented by Amount in Row (9)
2.3%

(12)

Type of Reporting Person (See Instructions)
CO

CUSIP No. 72919P103

13G

(1)

Names of Reporting Persons
Heights Capital Management, Inc.

(2)

Check the Appropriate Box if a Member of a Group (See Instructions)

(a)

o

(b)

o

(3)

SEC Use Only

(4)

Citizenship or Place of Organization
Delaware

Number of
Shares
Beneficially
Owned by
Each
Reporting
Person With:

(5)

Sole Voting Power
0

(6)

Shared Voting Power **
4,000,000

(7)

Sole Dispositive Power
0

(8)

Shared Dispositive Power **
4,000,000

(9)

Aggregate Amount Beneficially Owned by Each Reporting Person
4,000,000

(10)

Check Box if the Aggregate Amount in Row (9) Excludes Certain Shares (See Instructions)  o

(11)

Percent of Class Represented by Amount in Row (9)
2.3%

(12)

Type of Reporting Person (See Instructions)
CO

CUSIP No. 72919P103

13G

Item 1.

(a)

Name of Issuer
Plug Power Inc., a Delaware corporation (the “Company”).

(b)

Address of Issuer’s Principal Executive Offices
968 Albany Shaker Road, Latham, New York 12110

Item 2(a).

Name of Person Filing
This statement is filed by the entities listed below, who are collectively referred to herein as “Reporting Persons,” with respect to the shares of Common Stock of the Company, $0.01 par value per share (the “Shares”).

(i)            Capital Ventures International

(ii)           Heights Capital Management, Inc.

Item 2(b).

Address of Principal Business Office or, if none, Residence
The address of the principal business office of Capital Ventures International is:

The Harbour Trust Co. Ltd.

Windward 1, Regatta Office Park

West Bay Road

P.O. Box 897

Grand Cayman KY1-1103

Cayman Islands

The address of the principal business office of Heights Capital Management, Inc. is:

101 California Street, Suite 3250

San Francisco, California 94111

Item 2(c).

Citizenship
Citizenship is set forth in Row 4 of the cover page for each Reporting Person hereto and is incorporated herein by reference for each such Reporting Person.

Item 2(d)

Title of Class of Securities
Common Stock, $0.01 par value per share

Item 2(e)

CUSIP Number
72919P103

Item 3.

If this statement is filed pursuant to §§240.13d-1(b) or 240.13d-2(b) or (c), check whether the person filing is a:

(a)

o

Broker or dealer registered under section 15 of the Act (15 U.S.C. 78o).

(b)

o

Bank as defined in section 3(a)(6) of the Act (15 U.S.C. 78c).

(c)

o

Insurance company as defined in section 3(a)(19) of the Act (15 U.S.C. 78c).

(d)

o

Investment company registered under section 8 of the Investment Company Act of 1940 (15 U.S.C. 80a-8).

(e)

o

An investment adviser in accordance with §240.13d-1(b)(1)(ii)(E);

(f)

o

An employee benefit plan or endowment fund in accordance with §240.13d-1(b)(1)(ii)(F);

(g)

o

A parent holding company or control person in accordance with §240.13d-1(b)(1)(ii)(G);

(h)

o

A savings association as defined in Section 3(b) of the Federal Deposit Insurance Act (12 U.S.C. 1813);

(i)

o

A church plan that is excluded from the definition of an investment company under section 3(c)(14) of the Investment Company Act of 1940 (15 U.S.C. 80a-3);

(j)

o

A non-U.S. institution in accordance with §240.13d-1(b)(1)(ii)(J);

(k)

o

Group, in accordance with Rule 13d-1(b)(1)(ii)(K). If filing as a non-U.S. institution in accordance with §240.13d-1(b)(1)(ii)(J), please specify the type of institution:____________________________

CUSIP No. 72919P103

13G

Item 4.

Ownership

Provide the following information regarding the aggregate number and percentage of the class of securities of the issuer identified in Item 1.

The information required by Items 4(a) – (c) is set forth in Rows 5 – 11 of the cover page for each Reporting Person hereto and is incorporated herein by reference for each such Reporting Person.

The Shares reported as beneficially owned herein are issuable upon the exercise of a warrant to purchase Shares.

The Company’s Quarterly Report on Form 10-Q for the quarterly period ended September 30, 2014 indicates that there were 173,125,897 Shares outstanding as of November 5, 2014.

Heights Capital Management, Inc., which serves as the investment manager to Capital Ventures International, may be deemed to be the beneficial owner of all Shares owned by Capital Ventures International. Each of the Reporting Persons hereby disclaims any beneficial ownership of any such Shares, except for their pecuniary interest therein.

Item 5.

Ownership of Five Percent or Less of a Class

If this statement is being filed to report the fact that as of the date hereof the reporting person has ceased to be the beneficial owner of more than five percent of the class of securities, check the following:   x

Item 6.

Ownership of More than Five Percent on Behalf of Another Person

Not applicable.

Item 7.

Identification and Classification of the Subsidiary Which Acquired the Security Being Reported on By the Parent Holding Company or Control Person

Not applicable.

Item 8.

Identification and Classification of Members of the Group

Not Applicable

Item 9.

Notice of Dissolution of Group

Not applicable.

CUSIP No. 72919P103

13G

Item 10.

Certification

By signing below each of the undersigned certifies that, to the best of its knowledge and belief, the securities referred to above were not acquired and are not held for the purpose of or with the effect of changing or influencing the control of the issuer of the securities and were not acquired and are not held in connection with or as a participant in any transaction having that purpose or effect.

CAPITAL VENTURES INTERNATIONAL

HEIGHTS CAPITAL MANAGEMENT, INC.

By: Heights Capital Management, Inc.

By:

/s/ Brian Sopinsky

pursuant to a Limited Power of
Attorney, a copy of which was
previously filed.

Name: Brian Sopinsky

Title:   Secretary

By:

/s/ Brian Sopinsky

Name: Brian Sopinsky

Title:   Secretary

CUSIP No. 72919P103

13G

EXHIBIT

DESCRIPTION

I

Limited Power of Attorney*

II

Joint Filing Agreement*