SC 13D/A

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                                  UNITED STATES
                       SECURITIES AND EXCHANGE COMMISSION
                             WASHINGTON, D.C. 20549

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                                 SCHEDULE 13D/A
                                 (RULE 13d-101)

                    UNDER THE SECURITIES EXCHANGE ACT OF 1934
                                 AMENDMENT NO. 5

                       COGENERATION CORPORATION OF AMERICA
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                                (Name of Issuer)

                     Common Stock, par value $.01 per share
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                         (Title of Class of Securities)

                                   628950 10 7
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                                 (CUSIP number)

                                 James J. Bender
                       Vice President and General Counsel
                                NRG Energy, Inc.
                          1221 Nicollet Mall, Suite 700
                              Minneapolis, MN 55403
                                 (612) 373-5300
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                  (Name, address and telephone number of person
                authorized to receive notices and communications)

                               September 10, 1998
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             (Date of event which requires filing of this statement)

     If the filing person has previously filed a statement on Schedule 13G to
report the acquisition which is the subject of this Schedule 13D, and is filing
this schedule because of Rule 13d-1(b)(3) or (4), check the following box  / /.

     Note. Six copies of this statement, including all exhibits, should be filed
with the Commission. See Rule 13d-1(a) for other parties to whom copies are to
be sent.

     *The remainder of this cover page shall be filled out for a reporting
person's initial filing on this form with respect to the subject class of
securities, and for any subsequent amendment containing information which would
alter disclosures provided in a prior cover page.

     The information required on the remainder of this cover page shall not be
deemed to be "filed" for the purpose of Section 18 of the Securities Exchange
Act of 1934 ("Act") or otherwise subject to the liabilities of that section of
the Act but shall be subject to all other provisions of the Act (however, see
the Notes).



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     Item 4 of Schedule 13D is hereby amended and restated as follows:

ITEM 4.   PURPOSE OF TRANSACTION

     NRG Energy, Inc. ("NRG") acquired a 41.86% interest in Cogeneration
Corporation of America (formerly named "NRG Generating (U.S.) Inc." and "O'Brien
Environmental Energy, Inc.") (the "Company") pursuant to the Composite Fourth
Amended and Restated Plan of Reorganization (the "Plan") for O'Brien
Environmental Energy, Inc., confirmed by order of the United States Bankruptcy
Court for the District of New Jersey under Chapter 11 of the United States
Bankruptcy Code on February 22, 1996, and pursuant to the Amended and Restated
Stock Purchase and Reorganization Agreement dated as of January 31, 1996 (the
"Purchase Agreement"). Copies of the Plan and the Purchase Agreement were filed
as exhibits to Schedule 13D filed by NRG on May 10, 1996.

     In connection with the negotiation and consummation of the Plan, on March
8, 1996, NRG entered into a loan agreement (the "Loan Agreement") with O'Brien
(Schuylkill) Cogeneration, Inc. ("Schuylkill"), a wholly owned subsidiary of the
Company, pursuant to which NRG agreed to make a loan in the principal amount of
$10,000,000 available to Schuylkill upon Schuylkill's request. As part of the
consideration for entering into the Loan Agreement, the Company entered into an
option agreement dated March 8, 1996 (the "Option Agreement") with NRG. Pursuant
to the Option Agreement, the Company agreed that, on the date on which NRG made
a loan to Schuylkill pursuant to the Loan Agreement, NRG would have the right,
upon 15 business days' notice, to reduce the outstanding principal amount of the
note payable to NRG by Schuylkill by $3,000,000 in exchange for the 396,255
shares (the "Conversion Shares") of the Company's common stock, par value $0.01
per share (the "Common Stock").

     In June 1997, NRG agreed to allow Schuylkill to borrow funds under the Loan
Agreement on an "as needed" basis rather than requiring that Schuylkill borrow
the full $10,000,000 on the funding date. On August 22, 1997, NRG made a loan of
$2,700,000 to Schuylkill pursuant to the Loan Agreement, bringing the total
outstanding principal amount under the Loan Agreement to $4,500,000 and thereby
vesting in NRG an option, exercisable on 15 business days' notice to the
Company, to acquire the Conversion Shares. On August 28, 1997, NRG notified the
Company of its intention to exercise its option to acquire the Conversion Shares
(the "Exercise Notice"). On November 25, 1997, NRG acquired the Conversion
Shares. Copies of the Option Agreement and the Exercise Notice were filed as
exhibits to Amendment No. 1 to Schedule 13D filed by NRG on August 29, 1997.

     On August 3, 1998, NRG received an irrevocable proxy (the "Proxy") granting
it the right for a limited period of time to vote 147,676 shares of Common
Stock. NRG obtained the Proxy in order to increase its voting control over the
Company. A copy of the Form of Proxy was filed as an exhibit to Amendment No. 4
to Schedule 13D filed by NRG on August 3, 1998. As a result of its receipt of
the Proxy, NRG now beneficially owns an aggregate of 3,254,288, or 47.60%, of
the Common Stock.

     NRG has determined to seek to remove Robert Sherman from the Company's
Board of Directors. Accordingly, NRG has sent a letter, a copy of which is
attached hereto as Exhibit 6, to the Company's Chairman requesting that he call
a special meeting of the Company's stockholders to vote upon this issue. NRG has
also filed preliminary solicitation materials with the Securities and Exchange
Commission pursuant to Section 14(a) of the Securities Exchange Act of 1934, as
amended, relating to a proposed solicitation of proxies and consents from the


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Company's stockholders to remove Mr. Sherman from the Company's Board. If Mr.
Sherman is removed from the Company's Board, four of the remaining seven
directors will be NRG employees. In addition, NRG intends to propose to the
Company's Board that it fill the resulting vacancy with Michael O'Sullivan, who
is a Vice President of NRG's North American division. If Mr. Sherman is removed
from the Company's Board, it is anticipated that Mr. Sherman will also be
removed from his current positions as the Company's President and Chief
Executive Officer.

     Except as described in this Item 4, NRG has no present plans or proposals
which relate to or would result in (i) an extraordinary corporate transaction,
such as a merger, reorganization or liquidation, involving the Company or any of
its subsidiaries, (ii) a sale or transfer of a material amount of assets of the
Company or any of its subsidiaries, (iii) any change in the board of directors
or management of the Company or any of its subsidiaries, (iv) any material
change in the present capitalization or dividend policy of the Company, (v) any
other material change in the Company's business or corporate structure; (vi)
changes in the Company's charter or bylaws or other actions which may impede the
acquisition of control of the Company by any person, (vii) causing a class of
securities of the Company to be delisted from a national securities exchange or
cease to be quoted in an inter-dealer quotation system of a registered national
securities association, (viii) a class of equity securities of the Company
becoming eligible for termination of registration pursuant to Section 12(g)(4)
of the Securities Exchange Act of 1934 or (ix) any action similar to any of
those described above. However, NRG retains its rights to modify its plans with
respect to the transactions described in this Item 4, to acquire or dispose of
securities of the Company and to formulate plans and proposals that could result
in the occurrence of any such events, subject to applicable laws and
regulations and the Company's Certificate of Incorporation.

     NRG intends to review its investment in the Company on a continuing basis
and may, at any time, consistent with NRG's obligations under the federal
securities laws and the Company's Certificate of Incorporation, determine to
increase or decrease its ownership of shares of the Common Stock through
purchases or sales of the Common Stock in the open market or in privately
negotiated transactions. NRG's review of its investment in the Company will
depend on various factors, including the Company's business prospects, other
developments concerning the Company, general economic conditions, money and
stock market conditions, and any other facts and circumstances that may become
known to NRG regarding its investment in the Company. At the time of filing this
Amendment No. 5, NRG has no plans to purchase additional shares of Common Stock
in the open market or in privately negotiated transactions.

                            *      *      *

     Item 7 of Schedule 13D is hereby amended and restated as follows:

ITEM 7.   MATERIAL TO BE FILED AS EXHIBITS

     1.   Composite Fourth Amended and Restated Plan of Reorganization for
          O'Brien Environmental Energy, Inc. (previously filed as an exhibit to
          NRG's Schedule 13D on May 10, 1996).

     2.   Amended and Restated Stock Purchase and Reorganization Agreement,
          dated as of January 31, 1996, between NRG Energy, Inc. and O'Brien
          Environmental Energy, Inc. (previously filed as an exhibit to NRG's
          Schedule 13D on May 10, 1996).

     3.   Option Agreement, dated March 8, 1996, between O'Brien Environmental
          Energy, Inc. and NRG Energy, Inc. (previously filed as an exhibit to
          Amendment No. 1 to NRG's Schedule 13D on August 29, 1997).

     4.   Option Exercise Notice, dated August 28, 1997, from NRG Energy, Inc.
          to NRG Generating (U.S.), Inc. (previously filed as an exhibit to
          Amendment No. 1 to NRG's Schedule 13D on August 29, 1997).

     5.   Form of Proxy to be executed by Halcyon Alchemy Fund, L.P., Halcyon
          Special Situations, L.P., Gryphon Hidden Values Limited and Gryphon
          Hidden Values II Limited (previously filed as an exhibit to Amendment
          No. 4 to NRG's Schedule 13D on August 3, 1998).

     6.   Letter, dated September 14, 1998, from NRG Energy, Inc. to David H.
          Peterson, Chairman of the Board of Directors of Cogeneration
          Corporation of America.


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                                    SIGNATURE

     After reasonable inquiry and to the best of my knowledge and belief, I
certify that the information set forth in this statement is true, complete and
correct.

                                      NRG ENERGY, INC.

Dated:   September 14, 1998
                                      /s/      James J. Bender
                                      ------------------------------------------
                                      Name: James J. Bender
                                      Title:  Vice President and General Counsel







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EX-6

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                                                                       EXHIBIT 6

                         [NRG ENERGY, INC. LETTERHEAD]

                               September 14, 1998

Mr. David H. Peterson
Chairman of the Board
Cogeneration Corporation of America
One Carlson Parkway, Suite 240
Minneapolis, MN 55447

Dear Mr. Peterson:

     NRG Energy, Inc. ("NRG"), the record holder of 3,106,612 shares
(representing approximately 45% of the outstanding shares) of the Common Stock
of Cogeneration Corporation of America (the "Company"), respectfully requests
that you call a special meeting of the shareholders of the Company to vote upon
the removal of Robert T. Sherman, Jr. from his position as a Director of the
Company. NRG believes that it is in the best interest of the Company and its
shareholders to call such a meeting as soon as possible.

     Mr. Sherman's actions and lack of leadership have demonstrably hampered 
the Company's ability to grow and develop its business.

     NRG put at risk approximately $100 million in connection with acquiring 
its position in the Company and bringing the Company out of bankruptcy and has 
a strong interest in increasing the value of its investment and the investments 
of the other holders of the Company's Common Stock. Mr. Sherman's refusal to 
engage in a constructive dialogue with all members of the Company's Board of 
Directors has created a deadlock at the Board of Directors imperiling the 
Company's prospects for long-term growth and success. NRG has offered to break 
this deadlock by either increasing the size of the Board of Directors or by 
decreasing the size of the Board of Directors to its size prior to the addition 
of Mr. Sherman as a Director in May 1997, but Mr. Sherman and the other 
Directors have refused NRG's offers.

     As the Company's President and Chief Executive Officer, Mr. Sherman has 
failed to keep the Board of Directors adequately informed as to the Company's 
business and financing plans. In addition, NRG believes that Mr. Sherman has 
not developed any viable investment prospects for the Company, is interested 
only in achieving short-term goals, and has not focused on the long-term 
prosperity of the Company. Mr. Sherman's removal as the Company's President and 
Chief Executive Officer is overdue and cannot be accomplished while he remains 
a Director.

     The combination of Mr. Sherman's ineffective leadership and his 
unwillingness to engage in constructive discussions with all of the members of 
the Company's Board threatens the long-term viability of the Company. For these 
reasons, NRG requests that a meeting of the

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Mr. David H. Peterson
September 14, 1998
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shareholders of the Company be called, in order that the shareholders be 
permitted to decide whether they wish the Board to be able to progress in a 
reasonable and informed manner.


                                        Sincerely,

                                        /s/ James J. Bender

                                        James J. Bender
                                        Vice President and General Counsel
                                        NRG Energy, Inc.






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