Exhibit 10.40


                                 Lock-Up Agreement

                                 November 1, 1999

Goldman, Sachs & Co.
Hambrecht & Quist LLC
Merrill Lynch, Pierce, Fenner & Smith Incorporated
First Albany Corporation
c/o Goldman, Sachs & Co.
85 Broad Street
New York, NY  10004

	Re:	Plug Power Inc. - Lock-Up Agreement

Ladies and Gentlemen:

The undersigned understands that you, as representatives (the
"Representatives"), have entered into an Underwriting Agreement on behalf of the
several Underwriters named in Schedule I to such agreement (collectively, the
"Underwriters"), with Plug Power Inc., a newly- formed Delaware corporation (the
"Company") that will succeed by merger (the "Merger") immediately prior to the
offering described below to all the assets and liabilities of Plug Power,
L.L.C., a Delaware limited liability company (the "LLC"), providing for a public
offering of the Common Stock of the Company (the "Shares") pursuant to a
Registration Statement on Form S-1 filed with the Securities and Exchange
Commission (the "SEC").

In consideration of the agreement by the Underwriters to offer and sell the
Shares, and of other good and valuable consideration the receipt and sufficiency
of which is hereby acknowledged, the undersigned agrees that, during the period
beginning from the date of the final Prospectus covering the public offering of
the Shares and continuing to and including the date 180 days after the date of
such final Prospectus, the undersigned will not offer, sell, contract to sell,
pledge, grant any option to purchase, make any short sale or otherwise dispose
of any Membership Interests in the LLC or shares of Common Stock of the Company,
or any options or warrants to purchase any Membership Interests in the LLC or
shares of Common Stock of the Company, or any securities convertible into,
exchangeable for or that represent the right to receive Membership Interests in
the LLC or shares of Common Stock of the Company, whether now owned or
hereinafter acquired, owned directly by the undersigned (including holding as a
custodian) or with respect to which the undersigned has beneficial ownership
within the rules and regulations of the SEC (collectively the "MTI Shares").

The foregoing restriction is expressly agreed to preclude the undersigned from
engaging in any hedging or other transaction which is designed to or which
reasonably could be expected to lead to or result in a sale or disposition of
the MTI Shares even if such Shares would be disposed of by someone other than
the undersigned. Such prohibited hedging or other transactions would include
without limitation any short sale or any purchase, sale or grant of any right
(including without limitation any put or call option) with respect to any of the







MTI Shares or with respect to any security that includes, relates to, or derives
any significant part of its value from such Shares.

The undersigned further represents and agrees that the undersigned has not taken
and will not take, directly or indirectly, any action which is designed to or
which has constituted or which might reasonably be expected to cause or result
in stabilization or manipulation of the price of any security of the Company to
facilitate the sale or resale of the Shares, or which has otherwise constituted
or will constitute any prohibited bid for or purchase of the Shares or any
related securities.

Notwithstanding the foregoing, the undersigned may (i) transfer the MTI Shares
as a bona fide gift or gifts, provided that the donee or donees thereof agree to
be bound in writing by the restrictions set forth herein, (ii) transfer the MTI
Shares to any trust for the direct or indirect benefit of the undersigned or the
immediate family of the undersigned, provided that the trustee of the trust
agrees to be bound in writing by the restrictions set forth herein, and provided
further that any such transfer shall not involve a disposition for value, (iii)
pledge the MTI Shares to KeyBank pursuant to that certain Stock Pledge
Agreement, dated as of November 2, 1999, by and among the undersigned and
KeyBank (a copy of which is attached hereto as Exhibit A), provided that KeyBank
executes the letter attached hereto as Exhibit B, agreeing to be bound by the
restrictions set forth herein with respect to the MTI Shares, or (iv) with the
prior written consent of Goldman, Sachs & Co. on behalf of the Underwriters. For
purposes of this Lock-Up Agreement, "immediate family" shall mean any
relationship by blood, marriage or adoption, not more remote than first cousin.
In addition, notwithstanding the foregoing, if the undersigned is a corporation,
the corporation may transfer the capital stock of the Company to any
wholly-owned subsidiary of such corporation; provided, however, that in any such
case, it shall be a condition to the transfer that the transferee execute an
agreement stating that the transferee is receiving and holding such capital
stock subject to the provisions of this Agreement and there shall be no further
transfer of such capital stock except in accordance with this Agreement, and
provided further that any such transfer shall not involve a disposition for
value. The undersigned now has, and, except as contemplated by clause (i), (ii),
(iii), or (iv) above, for the duration of this Lock- Up Agreement will have,
good and marketable title to the Undersigned's Membership Interests in the LLC
(prior to effectiveness of the Merger) and Shares (after effectiveness of the
Merger), free and clear of all liens, encumbrances, and claims whatsoever. The
undersigned also agrees and consents to the entry of stop transfer instructions
with the Company's transfer agent and registrar against the transfer of the MTI
Shares except in compliance with the foregoing restrictions.

The undersigned understands that the Company and the Underwriters are relying
upon this Lock-Up Agreement in proceeding toward consummation of the offering.
The undersigned further understands that this Lock-Up Agreement is irrevocable
and shall be binding upon the undersigned's heirs, legal representatives,
successors, and assigns.

					Very truly yours,
					MECHANICAL TECHNOLOGY INCORPORATED


					By:______________________________________
						Name:	Cynthia A. Scheuer
						Title:	Vice President and CFO

                                   Exhibit A


                             Stock Pledge Agreement


                                   Exhibit B

                            [Letterhead of KeyBank]



Goldman, Sachs & Co.
Hambrecht & Quist LLC
Merrill Lynch, Pierce, Fenner & Smith Incorporated
First Albany Corporation
c/o Goldman, Sachs & Co.
85 Broad Street
New York, NY  10004

Re: Plug Power Inc. - Mechanical Technology Incorporated Lock-Up Agreement

Ladies and Gentlemen:

The undersigned understands that you, as representatives (the
"Representatives"), have entered into an Underwriting Agreement on behalf of the
several Underwriters named in Schedule I to such agreement (collectively, the
"Underwriters"), with Plug Power Inc., a Delaware corporation (the "Company"),
and Plug Power, LLC, providing for a public offering of the Common Stock of the
Company (the "Shares") pursuant to a Registration Statement on Form S-1 filed
with the Securities and Exchange Commission (the "SEC").

The undersigned also understands that in connection with such offering you have
received a Lock-up Agreement dated as of November 2, 1999, from Mechanical
Technology Incorporated ("MTI"), an executed copy of which is attached hereto as
Exhibit A (the "MTI Lock-Up Agreement"). The undersigned further understands
that the MTI Lock-Up Agreement permits MTI to pledge the MTI Shares (as defined
therein) to the undersigned, only upon the execution by the undersigned of this
agreement.

In consideration of the agreement by the Underwriters to offer and sell the
Shares and to permit the pledge of the MTI shares to the undersigned, and of
other good and valuable consideration the receipt and sufficiency of which is
hereby acknowledged, the undersigned hereby agrees, with respect to the MTI
Shares, to be bound by all of the restrictions applicable to MTI and the MTI
Shares under the MTI Lock-Up Agreement, to the same extent and on the same terms
and conditions as would have been applicable to MTI thereunder in the absence of
the pledge of MTI Shares to the undersigned. The undersigned understands that
the Company and the Underwriters are relying upon this agreement in proceeding
toward consummation of the offering. The undersigned further understands that
this agreement is irrevocable and shall be binding upon the undersigned's heirs,
legal representatives, successors, and assigns.

						Very truly yours,

						KEYBANK


						By:_____________________________
						  	Name:
							Title: