EXHIBIT 10.21

CONFIDENTIAL INFORMATION HAS BEEN OMITTED PURSUANT TO RULE 406 UNDER THE
SECURITIES ACT AND HAS BEEN FILED SEPARATELY WITH THE SECURITIES AND EXCHANGE
COMMISSION. THE LOCATIONS OF THE OMITTED INFORMATION HAVE BEEN INDICATED WITH
ASTERISKS.

                      DEVELOPMENT COLLABORATION AGREEMENT

     This DEVELOPMENT COLLABORATION AGREEMENT (this "Agreement") is entered into
as of July 30,1999, by and between JOH. VAILLANT GMBH U. CO., a German
kommanditgesellschaft ("Vaillant"), having its principal place of business at
Berghauser StraBe 40, 42859 Remscheid, Federal Republic of Germany, and PLUG
POWER, LLC, a Delaware limited liability company ("PP"), having its principal
place of business at 968 Albany-Shaker Road, Latham, New York 12110, USA.

     WHEREAS, Vaillant and PP are contemplating entering into an Umbrella
Agreement (the "Umbrella Agreement") by and among Vaillant, PP and GE Fuel Cell
Systems, LLC, a Delaware limited liability company ("GEFCS"), pursuant to which,
among other things, Vaillant, PP and GEFCS would collaborate to develop,
manufacture, sell, install and service certain FCHAs (as defined in Section 1
below) for providing heat, electricity and hot water for residential
applications worldwide; and

     WHEREAS, in anticipation of entering into the Umbrella Agreement and the
other agreements contemplated thereby, the parties hereto desire to confirm
herein their understandings and agreements in respect to such collaboration and
matters related to the development of FCHAs.

     NOW, THEREFORE, in consideration of the recitals and the mutual covenants
and agreements contained herein, and other good and valuable consideration, the
receipt and sufficiency of which are hereby acknowledged, the parties hereto
agree as follows.

     1.   Definitions. For purposes of this Agreement, capitalized terms used
but not otherwise defined herein shall have the following meanings:

     "Effective Date" shall mean the date of this Agreement.

     "Energy Management System" shall mean a controller which communicates with
the following: the FCHA subsystems (Fuel Cell Subsystem and Heater Subsystem),
the components of the domestic heating system and the communication interface
for the customer to ensure a technically and economically optimized operation of
the FCHA.

     "Europe" shall mean those countries listed on Exhibit A attached hereto.

     "FCHA" shall mean a fuel-cell driven system that generates both usable heat
and electricity, floor standing or wallmounted, packaged in one or more housings
with an electric power output of less than or equal to 10KW, fueled with natural
gas or bio gas, consisting of an integrated Fuel Cell System and Heater
Subsystem.

     "Fuel Cell Subsystem" shall mean a subsystem of an FCHA comprised of the
fuel cell stack, fuel processor, auxiliaries and subsystem controls to convert
natural gas into unregulated DC current.


     "Heater Subsystem" shall mean a subsystem of an FHCA comprised of the
heating components, subsystem controls, energy management system, inverter and
auxiliaries.

     "IP" shall mean any invention, discovery, concept, expression or work,
whether or not patented or patentable, including, but not limited to,
discoveries, compositions, know-how, procedures, technical information,
processes, methods, devices, formulas, protocols, techniques, designs and
drawings, any physical embodiment thereof, and any patent (and applications
therefor), trademark (and applications therefor), copyright (and applications
therefor), trade name, trade secret, know-how or other intellectual property
right related thereto.

     "Party" or "Parties" shall mean Vaillant or PP, or Vaillant and PP.

     "Product" shall mean the Initial Product, the Ultimate Product and any
Additional Products (as each is defined in Section 2).

     "Prototype" shall mean a pre-commercial version of the Initial Product.

     "Regulatory Approval" shall mean, with respect to any country, filing, for
and receipt of all regulatory agency registrations and approvals required for
the marketing, installation and sale of a product for the application for which
it is being marketed in such country.

     "Regulatory Filings" shall mean all applications, filings, materials,
studies, data and documents of any nature whatsoever filed with, prepared in
connection with or necessary to support any Regulatory Approval process in any
country or territory.

     2.   Objectives; Relationship to Other Agreements.

          2.1  Initial Product. The Parties will collaborate to develop a floor
               ---------------
standing FCHA with an output of approximately [***] and an approximately {***]
for use in Europe (the "Initial Product").

          2.2  Ultimate Product.  The experience gained in the development and
               ----------------
production of the Initial Product will serve as a basis for the Parties'
collaboration on the development, manufacture, sale, installation and service of
an approximately [***] FCHA for use in Europe (the "Ultimate Product"), and such
other FCHA products as the Parties shall mutually agree ("Additional Products").
The timing of such collaboration and work plan shall be mutually agreed upon by
the Parties.

          2.3  Relationship to Other Agreements. The Parties contemplate that
all Products (including the Prototypes described in Section 4.1) to be
manufactured pursuant to this Agreement will be marketed, distributed, sold,
installed and serviced in accordance with the Umbrella Agreement and any
ancillary agreements to the Umbrella Agreement. PP acknowledges that Vaillant
shall be the exclusive manufacturer of FCHAs for distribution in Europe.
Vaillant hereby acknowledges that GEFCS is the exclusive distributor of PP fuel
cell

CONFIDENTIAL INFORMATION HAS BEEN OMITTED PURSUANT TO RULE 406 UNDER THE
SECURITIES ACT AND HAS BEEN FILED SEPARATELY WITH THE SECURITIES AND EXCHANGE
COMMISSION. THE LOCATIONS OF THE OMITTED INFORMATION HAVE BEEN INCLUDED WITH
ASTERISKS.



systems for certain specified stationary applications under 35kW. PP shall sell
Fuel Cell Subsystems to GEFCS pursuant to a Distributor Agreement, dated as of
February 2, 1999 (the "GEFCS Distribution Agreement"), between GEFCS and PP, and
Vaillant shall purchase such Fuel Cell Subsystems from GEFCS. PP represents and
warrants that (i) the sale of Fuel Cell Subsystems hereunder are subject to the
terms and conditions of the GEFCS Distribution Agreement, pursuant to which
GEFCS has exclusive worldwide distribution rights (with the exception of four
states in the United States) and (ii) the Fuel Cell Subsystems supplied to GEFCS
under the GEFCS Distribution Agreement are to be competitively priced.

     3.   Project Management.

          3.1  Steering Committee. The activities of the collaboration shall be
conducted under the direction of a steering committee (the "Steering Committee")
comprised of two (2) named representatives of each Party. Each Party shall
appoint its respective representatives to the Steering Committee from time to
time, and may substitute one or more of its representatives, in its sole
discretion, effective upon notice of such change to the other Party. The
Steering Committee shall meet, in person or by telephone conference, not less
than once each calendar quarter, on such date and at such times and places as
agreed to by the Parties. At such meetings, the Steering Committee shall discuss
and endeavor to resolve any issues that are acting as barriers to progress and
achievement of milestones under the development program. The decisions of the
Steering Committee shall be by unanimous vote, each member of the Steering
Committee having one vote, provided that at least one representative of each
Party is present at such meeting. The approval of the Steering Committee shall
be required for the following actions:

               (1)  any modification or amendment to this Agreement;

               (2)  any modification to the development program outlined in
Sections 4 and 5, the budget plans outlined in Section 7 or the Prototype
Specifications or Initial Product Specifications as outlined in Section 4.3; or

               (3)  any other decisions presented to the Steering Committee by
either Party.

          3.2  Project Managers. Each Party will designate a project manager
(such person or his/her successor referenced herein as a "Project Manager"). The
Project Managers will share overall responsibility for the coordination of the
development of the Initial Product. Each Party's Project Manager will be the
other Party's point of contact for the resolution of any problems which may
arise in connection with this Agreement. Each Party will notify the other Party
within 30 days after the execution of this Agreement of the appointment of its
Project Manager and will notify the other Party as soon as practical upon
changing such appointment. The Project Managers will report to and act on the
direction of the Steering Committee.

     4.   Development Program.


          Project Phases. The development and production program will be
conducted in accordance with the following two phases:

          4.1  Phase I Prototype Development. Phase I will begin on October 1,
1999. Phase I will cover the development effort for a Prototype and production,
sale, installation, service and field testing of [***] Prototype units.

          4.2  Phase 2 Commercial Production.  Phase 2 will begin after the
successful field testing of the [***] Prototype units described in Phase 1.
Phase 2 will include the production, sale, installation and servicing of
commercial Initial Products.

          4.3  Initial Product Specifications.  Preliminary specifications for
the Prototypes (the "Prototypes Specifications") shall be agreed upon by the
Parties on or before July 1, 2000 and attached hereto as Exhibit Al.
Specifications for the commercial Initial Products (the "Initial Product
Specifications") shall be agreed upon by the Parties on or before January 1,
2001 and attached hereto as Exhibit A2.

     5.   Development Responsibilities.

          5.1  Phase 1 Responsibilities.

               (1)  PP will develop, manufacture and test the Fuel Cell
Subsystem for the Prototypes and provide such test results to Vaillant. On or
before November 30, 1999, PP shall prepare a detailed work plan for PP's
development of the Fuel Cell Subsystem, including a timetable for achieving
milestones under Phase 1 and a budget therefor pursuant to Section 7.1, which
shall be attached hereto as Exhibit B (the "FCS Development Plan").

               (2)  Vaillant will develop, manufacture and test a Heater
Subsystem for the Prototypes and provide such test results to PP. On or before
November 30, 1999, Vaillant shall prepare a detailed work plan for Vaillant's
development of the Heater Subsystem, including a timetable for achieving
milestones under Phase I and a budget therefor pursuant to Section 7.1, which
shall be attached hereto as Exhibit C (the "HS Development Plan").

               (3)  PP and Vaillant will cooperate to integrate the Fuel Cell
Subsystem and the Heater Subsystem into the Prototypes. Vaillant will test the
Prototypes and provide such test results to PP. On or before November 30, 1999,
PP and Vaillant shall prepare a detailed work plan for the joint effort by PP
and Vaillant to integrate the Fuel Cell Subsystem and the Heater Subsystem into
the Prototypes, including a timetable for achieving milestones under Phase I and
a budget therefor pursuant to Section 7.1, which shall be attached hereto as
Exhibit D (the "Integration Development Plan").

          5.2  Phase 2 Responsibilities. The Parties shall conduct the
activities below in order to produce the quantities of Initial Products set
forth in the ancillary agreements to the Umbrella Agreement,




               (1)  PP shall manufacture and quality test the Fuel Cell
Subsystem for the Initial Product and provide such test results to Vaillant. On
or before January 1, 2001, a detailed work plan for PP's development of
manufacturing facilities for the Fuel Cell Subsystem, including a timetable for
achieving milestones under Phase 2 and a budget therefor pursuant to Section
7.2, shall be attached hereto as Exhibit E (the "FCS Production Plan").

               (2)  Vaillant shall manufacture and quality test the Heater
Subsystem for the Initial Product and provide such test results to PP. On or
before January 1, 2001, Vaillant shall prepare a detailed work plan for
Vaillant's development of manufacturing facilities for the Heater Subsystem,
including a timetable for achieving milestones under Phase 2 and a budget
therefor pursuant to Section 7.2, which shall be attached hereto as Exhibit F
(the "HS Production Plan").

               (3)  (i)  Vaillant shall manufacture the Initial Product by
assembling the Fuel Cell Subsystem and the Heater Subsystem into the Initial
Product. Vaillant shall quality, test the Initial Product and provide such test
results to PP. On or before January 1, 2001, Vaillant shall prepare a detailed
work plan for the development of manufacturing facilities for the Initial
Product, including a timetable for achieving milestones under Phase 2 and a
budget therefor pursuant to Section 7.2, which shall be attached hereto as
Exhibit G (the "Initial Product Production Plan").

                    (ii) Vaillant's responsibility to sell, install and service
Initial Products in [***] shall be set forth in the ancillary agreements to the
Umbrella Agreement.

          5.3  Revisions to Work Plans. Revisions to any of the work plans
listed in this Section 5 shall require the approval of the Steering Committee.

     6.   Representations and Warranties.

          6.1  PP represents and warrants that the IP owned by PP prior to the
Effective Date with regard to the Fuel Cell Subsystem belongs to PP and is free
of any third party rights.

          6.2  Vaillant represents and warrants that the IP owned by Vaillant
prior to the Effective Date with regard to the Heater Subsystem belongs to
Vaillant and is free from any third party rights.

          6.3  Neither Party makes any representations or warranties concerning
its developmental efforts hereunder, including, without limitation, any
warranties of fitness or warranties of merchantability with respect to any
particular use or purpose. However both Parties undertake to make commercially
reasonable efforts in order to achieve the objectives of this collaboration.

          6.4  To achieve the defined milestones, (i) PP undertakes to spend at
least the



total budgeted amount provided for in Exhibit B, Exhibit E and portion allocated
to it in Exhibit D and (ii) Vaillant undertakes to spend at least the total
budgeted amount provided for in Exhibit C, Exhibit F, Exhibit G and the portion
allocated to it in Exhibit D, unless: (1) all material objectives in reference
to the work plans mentioned above can be achieved with lower expenditure; (ii) a
Party intends not to spend the total budgeted amount, having determined that the
milestone in issue is not commercially or technically practicable, such
determination being based on reasonable substantiation; or (iii) a Party
determines that the expenditure determined to be necessary to reach the
milestone exceeds the budgeted amount by more than ten percent (10%). In such
cases, as a result of such determination by a Party, the Steering Committee will
promptly meet in order to decide whether to continue the collaboration. If the
Steering Committee fails to reach a decision by unanimous vote within ten weeks
from the date of the first such meeting of the Steering Committee, thereby
resulting in a deadlock of the Steering Committee for purposes hereof, each
Party shall be entitled to terminate this Agreement by notice to the other Party
pursuant to clause (ii) of Section 16.3.

     7.   Development Budget.

          7.1  Phase I Budget.

               (1) PP estimates that it will require approximately [***], which
estimate shall be non binding, to fund PP's FCS Development Plan, including the
direct manufacturing cost of [***] Prototypes.  On or before November 30, 1999,
PP shall provide Vaillant a detailed budget for the FCS Development Plan, which
shall be included in Exhibit B.

               (2) Vaillant estimates that it will require approximately [***],
which estimate shall be nonbinding, to fund Vaillant's HS Development Plan,
including the direct manufacturing cost of [***] Prototype units.  On or before
November 30, 1999, Vaillant shall provide to PP a detailed budget for the HS
Development Plan, which shall be included in Exhibit C.

               (3)  On or before November 30, 1999, PP and Vaillant shall
cooperate to develop a budget for the Initial Product Production Plan, which
shall be included in Exhibit D.

          7.2  Phase 2 Budget.

               (1)  On or before September 30, 1999, PP shall provide Vaillant
with an estimate, which estimate shall be nonbinding, of the amount of money
required to fund the FCS Production Plan. On or before January 1, 2001, PP shall
provide to Vaillant a detailed budget for the FCS Production Plan, which shall
be included in Exhibit E.

               (2)  Vaillant estimates that it will require approximately [***],
               which estimate shall be nonbinding, in order to fund the HS
               Production Plan. On or before January 1, 2001, Vaillant shall
               provide to PP a detailed budget for the HS Production Plan and
               the Initial Product Production which shall be included in
               Exhibits F and G, respectively.




budget for the HS Production Plan and the Initial Product Production Plan, which
shall be included in Exhibits F and G, respectively.

          7.3  Phase I Funding Sources. PP shall obtain funding for the
manufacture of [***] Fuel Cell Subsystems for Prototypes by selling such
subsystems to GEFCS. Vaillant shall agree to purchase such subsystems from
GEFCS. All prices, terms and conditions for such sale shall be determined among
PP, Vaillant and GEFCS in the ancillary agreements to the Umbrella Agreement.
Either Party may use government grants or subsidies to meet its own funding
obligations. The Parties shall make reasonable efforts to support one another in
obtaining such government grants or subsidies. Upon the completion of the
detailed budgets completed by the Parties on or before November 30, 1999, PP may
request that Vaillant fund a portion of its development cost. Any such funding
will be mutually agreed upon on or before December 31, 1999.

     8.   Recovery of Investments. Vaillant and PP shall fund the development to
achieve the objectives of this collaboration in accordance with the provisions
stipulated herein. Both Parties consider this collaboration to be an
entrepreneurial undertaking. Thus both Parties shall recover their funds by
selling the Products and Prototypes resulting from this collaboration. Vaillant
intends to recover its investment by manufacturing and selling FCHAs in
accordance with the Umbrella Agreement and the ancillary agreements to the
Umbrella Agreement. PP intends to recover its investment by manufacturing and
selling Fuel Cell Subsystems through GEFCS in accordance with the Umbrella
Agreement, the ancillary agreements to the Umbrella Agreement and the GEFCS
Distributor Agreement.

     9.   Reporting.

          9.1  Project Status Reports. The Project Manager of each Party shall
provide quarterly written reports to the Steering Committee outlining the work
performed during the preceding quarter, and the work to be completed during the
succeeding quarter, in connection with such Party's development efforts under
this Agreement.

          9.2  IP Disclosure. During the term of this Agreement, each Party
shall promptly disclose to the other Party any IP to be owned by or licensed to
such other Party under this Agreement, the Umbrella Agreement or the ancillary
agreements to the Umbrella Agreement.

     10.  Intellectual Property.

          10.1 Any IP owned by either Party prior to the Effective Date or
developed outside of the scope of this Agreement shall remain the sole property
of such Party.

          10.2 The ownership of any IP developed by either Party during the
course of and directly as a result of the performance of this Agreement
("Developed IP"), regardless of the identity of the inventing Party, shall be
allocated as follows:




               (1)  Developed IP that relates to the Fuel Cell Subsystem,
including, without limitation, the fuel cell stack and the fuel processor, and
internal integration and control within such Fuel Cell Subsystem, shall be owned
by PP.

               (2)  Developed IP that relates to the Heater Subsystem,
including, without limitation, the heater components, Energy Management System,
inverter and internal integration and control within such Heater Subsystem shall
be owned by Vaillant. Vaillant shall grant PP a non-exclusive license to make,
have made, use, sell and service Energy Management Systems worldwide. The
license fee for such license shall not exceed [***] of the net sales price of
the Heater Subsystem and shall be mutually agreed upon by the Parties by January
1, 2001, taking into account the Parties' respective contributions to the
development of such Energy Management System.

               (3)  Developed IP that relates to the integration of the Fuel
Cell Subsystem and the Heater Subsystem into the FCHA shall be jointly owned by
PP and Vaillant ("Joint IP"). Each of PP and Vaillant may use and license the
use of the Joint IP without any obligation to the other to account for profits,
royalties or other revenue relating thereto.

          10.3 Each Party agrees to assign, grant and convey to the appropriate
Party all rights, title and interest to any Developed IP which is to be owned by
the assignee Party pursuant to Section 10.2 (the "Owner"). Each Party shall
execute and deliver (and have executed and delivered by its employees) any and
all declarations, assignments and other documents, and provide all other
reasonable assistance, that the Owner reasonably determines may be necessary or
desirable to establish the Owner's ownership of, and to enforce thereafter any
intellectual property rights in, such Developed IP.

          10.4 PP hereby grants to Vaillant a royalty-free license, during the
term of this Agreement, to incorporate the Fuel Cell Subsystems supplied by PP
as components of FCHAs to be manufactured by Vaillant pursuant to the Umbrella
Agreement and the ancillary agreements to the Umbrella Agreement.

     11.  Limitations on Liability.

          11.1 Subject to Section 11.2, the liability of each Party to the other
Party for damages, for any cause whatsoever, regardless of form of action,
whether in contract or tort, including negligence, shall not exceed $ 1,000,000
and shall be limited to direct damages suffered by the injured Party and neither
Party shall be liable to the other Party for any special, indirect or
consequential damage, including lost profits, lost revenues, failure to realize
expected savings, or other commercial or economic losses of any kind.

          11.2 The foregoing limitation of liability shall not apply with
respect to:

               (1)  any loss, claim, demand, damage or cost arising as a result
of any infringement of any IP;




               (2) any disclosure or use by either Party of the other Party's
confidential information in violation of this Agreement; or

               (3) any willful misconduct or gross negligence by either Party in
its performance under this Agreement.

     12.  Trademarks. During the term of this Agreement, Vaillant shall affix,
in addition to the Vaillant trademark but separate from the Vaillant trademark
and smaller than the Vaillant trademark, the Mark (as defined below) on all
FCHAs manufactured by Vaillant and include the Mark in all of Vaillant's FCHA
marketing literature, in each case subject to PP's reasonable quality control
guidelines and procedures. The details shall be agreed upon by unanimous
resolution of the Steering Committee, which shall take into account PP's
standing in the business and the quality of the Mark. Upon the expiration or
termination of this Agreement, Vaillant shall make no further use of the Mark.
Except as set forth in this paragraph, this Agreement shall not grant to
Vaillant any right, title or interest in the Mark. All use of the Mark by
Vaillant shall inure to the benefit of PP. At no time during or after the term
of this Agreement will Vaillant challenge or assist others to challenge PP's
intellectual property rights in the Mark or attempt to register any trademarks,
trade names or other proprietary indicia confusingly similar to the Marks. For
the purposes of this Agreement, "Mark" will mean any proprietary indicia,
trademark, trade name, symbol, logo or brand name that PP has adopted to
identify it and/or its products and services.

     13.  Confidentiality.

          13.1 Confidential Information. During the term and for a period ending
five (5) years after expiration or termination of this Agreement, each Party
shall maintain in confidence and not disclose to any third party or use for any
purpose except for the purposes of performing under this Agreement, all
confidential and proprietary information of the other Party ("Confidential
Information"). Confidential Information shall include any information which is
disclosed by a Party to the other Party in connection with the performance of
this Agreement. The foregoing use and confidentiality restrictions shall not
apply to (i) information that is or becomes a matter of public knowledge through
no fault of the receiving Party; (ii) information which is obtained lawfully
from a third party not bound to obligations of secrecy to the disclosing party;
(iii) information known to the recipient at the time of disclosure as
substantiated by documented evidence predating the disclosure; or (iv)
information which is required to be disclosed by law or governmental order;
provided that the Party seeking to retain the confidentiality of such
information shall be given a reasonable opportunity to contest any such
disclosure.

          13.2 Disclosure of Confidential Information in Regulatory Filings.
Nothing contained herein is intended to prevent either Party from using the
Confidential Information to make Regulatory Filings and to obtain necessary or
appropriate Regulatory Approvals or in disclosure documents prepared by either
Party to comply with applicable securities laws. Either Party making such a
disclosure shall provide the other Party a reasonable opportunity to review such
disclosure.


          13.3 Return of Confidential Information. Upon termination or
expiration of this Agreement or upon the disclosing Party's request, whichever
is earlier, the receiving Party shall return to the disclosing Party or, at the
disclosing Party's request, destroy, all materials containing the Confidential
Information of the disclosing Party (including, without limitation, any and all
copies extracts and compilations thereof).

          13.4 Disclosure of Confidential Information Not A License. The
furnishing of the Confidential Information of the disclosing Party to the
receiving Party shall not constitute any grant or license to the receiving Party
under any legal rights now or hereinafter held-by the disclosing Party.

          13.5 Subcontractors. Notwithstanding the foregoing, each Party may
disclose to third party subcontractors Confidential Information for the purpose
of performing such Party's obligations under this Agreement, provided that all
such third party subcontractors shall have entered into a confidentiality
agreement providing protection to Confidential Information at least equivalent
to that contained in this Agreement.

     14.  Exclusive Arrangement; Non-Competition.

          14.1 Exclusive Arrangement. During the term of this Agreement, neither
Party shall collaborate, directly or indirectly, with any third party, or
otherwise participate in any business involved in the development or production
of FCHAs, except to the extent provided in this Agreement, the Umbrella
Agreement or the ancillary agreements to the Umbrella Agreement.

          14.2 No Sale Outside Certain Countries. Vaillant shall not, directly
or indirectly, market, sell, service or have serviced FCHAs outside of Germany,
Austria, The Netherlands and Switzerland. Vaillant shall not be deemed to sell
or market, directly or indirectly, FCHAs outside of Germany, Austria, The
Netherlands and Switzerland provided that Vaillant sells FCHAs to wholesalers or
resellers subject to a condition which prohibits such wholesalers and resellers
from offering FCHAs for sale outside the four countries listed above. Vaillant
shall terminate its business relationship with any such wholesaler or reseller,
if permitted by law, if such wholesaler or reseller breaches the aforementioned
restriction.

     15.  Regulatory Approvals.

          15.1 Regulatory Approvals. Vaillant shall be responsible for obtaining
all Regulatory Approvals for all Products and Prototypes to be installed in
Germany, Austria, The Netherlands and Switzerland and for ensuring compliance
with present and future applicable statutes, laws, ordinances and regulations of
European national, federal, state and local governments or other European
regulatory authorities relating to the manufacture, marketing, sale, shipment
and use of such Products and Prototypes in Germany, Austria, The Netherlands and
Switzerland.

          15.2 Fuel Cell Subsystem. PP shall be responsible for ensuring that
the Fuel


Cell Subsystem complies in all material respects with present and future
applicable statutes, laws, ordinances and regulations of European national,
federal, state and local governments or other European regulatory authorities
relating to the manufacture of the Fuel Cell Subsystem that are identified in
writing by Vaillant. In particular, PP will provide reasonable assistance to
Vaillant with regard to research and negotiations with regulatory authorities
and product certification bodies.

     16.  Term and Termination.

          16.1 Term.  The term of the Collaboration Agreement shall commence as
of the Effective Date and shall continue in force until March 2, 2004 unless
terminated earlier pursuant to this Section 16.  The Parties hereto may,
however, extend the term of this Agreement for additional periods under mutually
agreeable terms and conditions evidenced in a written amendment to this
Agreement.

          16.2 Termination for Cause. If either Party commits any material
breach of or default in any of the terms, conditions or provisions of this
Agreement, and fails to remedy such breach or default within 60 days after
receipt of written notice thereof from the other Party, the Party giving notice,
at its option and in addition to any other remedies which it may have at law or
in equity, may terminate this Agreement by sending written notice of termination
to the breaching or defaulting Party, and such termination shall be effective as
of the date such notice is received.

          16.3 Other Termination. This Agreement shall terminate (i)
automatically (x) in the event the Umbrella Agreement and the ancillary
agreements thereto (as described in that certain Memorandum of Understanding
dated as of July 2, 1999, among PP, Vaillant and GEFCS) are not entered into by
the parties thereto on or before September 30, 1999, unless otherwise mutually
agreed, or (y) upon the filing of a petition in bankruptcy, insolvency or
reorganization against or by either Party, or either Party going into
receivership or otherwise becoming insolvent or (ii) upon notice by either Party
to the other that it desires to terminate this Agreement as a result of Steering
Committee deadlock pursuant to Section 6.4.

          16.4 Change of Control. Either Party may terminate this Agreement
immediately upon giving notice in writing to the other Party of its intent to
terminate if any direct competitor of the terminating Party acquires (whether by
merger, consolidation, sale, assignment, lease, transfer or otherwise, in one
transaction or a series of related transactions), or otherwise beneficially owns
20% or more of the outstanding voting securities of the other Party.

          16.5 Survival.  Sections 10.3, 13 and 17 shall survive the expiration
or termination of this Agreement.

     17.  Miscellaneous.

          17.1 Good Faith Negotiation. Both Parties shall negotiate in good
faith in


order to negotiate and execute the Umbrella Agreement and the ancillary
agreements to the Umbrella Agreement on or before September 30, 1999.

          17.2 Arbitration.

               (1) All disputes between the Parties arising out of or in
connection with this Agreement shall be subject to arbitration by one or more
arbitrators in accordance with the ICC arbitration rules. Arbitration shall take
place in London, England.

               (2) Any award rendered by the arbitrators shall be final and
binding upon the Parties hereto. Judgment upon the award may be entered in any
court of record of competent jurisdiction. Each Party shall pay its own expenses
of arbitration and the expenses of the arbitrators shall be equally shared
unless the arbitrators assess as part of their award all or any part of the
arbitration expenses of one Party (including reasonable attorneys' fees) against
the other Party.

          17.3 Compliance with Laws. Subject to Section 15, each Party shall
perform all of their obligations under this Agreement in accordance with all
applicable laws, rules and regulations.

          17.4 Publicity. Without the prior written consent of the other Party
hereto, neither Party shall, and each of the Parties will cause their respective
representatives not to, make any release to the press or other public
disclosure, or make any statement to any other person other than their
respective representatives, with respect to either the fact that discussions or
negotiations are taking place concerning the collaborations between the Parties
hereto or the existence or contents of this Agreement, except for such public
disclosure as may be necessary for the disclosing Party not to be in violation
of or in default under any applicable law, regulation, government order or as
may be necessary to apply for subsidies or to prepare and execute a
collaboration with development partners of subsystems for the Heater Subsystem
and/or Fuel Cell Subsystem.

          17.5 Notice. Any notice or other communication required or permitted
under this Agreement shall be sent by recognized international courier service,
charges pre-paid, or by facsimile transmission, to the address or facsimile
number specified below:

          If to Vaillant:     Joh. Vaillant GmbH u. Co.
                              Berghauser StraBe 40
                              42859 Remscheide
                              Federal Republic of Germany
                              Attn:
                              Fax:


          If to PP:      Plug Power, LLC
                         968 Albany-Shaker Road
                         Latham, New York 12110
                         USA
                         Attn:  Ana Galeano
                         Fax:  (518) 782-7914

or to such other address or facsimile number as the person may specify in a
notice duly given to the sender as provided herein. A notice will be deemed to
have been given upon receipt.

          17.6  Independent Contractors. The Parties hereto shall be independent
contractors with respect to each other, and neither shall be deemed to be the
agent, principal, employee, servant, joint venturer or partner of the other for
any purpose which could impose liability upon one Party for the act or failure
to act of the other Party.

          17.7  Sole Agreement. Subject to the Umbrella Agreement and any
ancillary agreements thereto, this Agreement and any Exhibits attached hereto
constitute the entire agreement between the Parties concerning the subject
matter hereof and supersedes all prior understandings and agreements, whether
written or oral.

          17.8  No Implied Licenses. No rights or licenses with respect to a
Party's IP, Confidential Information, Trademarks or other proprietary rights are
granted or deemed granted to the other Party hereunder or in connection
herewith, other than those rights expressly granted in this Agreement.

          17.9  Severability. In the event that any provision of this Agreement
shall be held illegal, void or ineffective, the remaining portions hereof shall
remain in full force and effect so long as such remaining portions do not
materially change the intent of this Agreement or the right or obligations of
the Parties hereunder. If any term or provision of this Agreement is in conflict
with any applicable statute or law in any jurisdiction, then such term or
provision shall be deemed inoperative in such jurisdiction to the extent of such
conflict and the Parties will renegotiate the affected terms and conditions of
this Agreement to resolve any inequities. It is the intention of the Parties
that, if any court or other tribunal construes any provision or clause of this
Agreement, or any portion thereof, to be illegal, void or unenforceable because
of the duration of such provision or the area or matter covered thereby; such
court shall reduce the duration, area or matter of such provision and enforce
such provision in its reduced form.

          17.10 No Third Party Benefits. Nothing in this Agreement, express
or implied, is intended to confer on any person other than the Parties hereto or
their permitted assigns, any benefits, rights or remedies.

          17.11 Governing Law. This Agreement shall be governed and
construed in the accordance with the laws of England without giving effect to
any conflicts of laws or other principles of any jurisdiction which would result
in the application of any law other than the law of England.


          17.12 Assignments.  Neither Party shall assign or transfer any
right and/or obligation under this Agreement to any other third party, whether
voluntarily or by operation of law, without the prior written consent of the
other Party, provide that a Party, except in the case of an assignment to a
competitor of the other Party, may assign this Agreement without the consent of
the other Party in connection with a merger, consolidation or other change in
control of such Party or a sale of all or substantially all of such Party's
assets. Any prohibited assignment shall be null and void. Subject to the
foregoing, this Agreement will inure to the benefit of the Parties and their
respective permitted successors and assigns.

          17.13 No Waiver. A waiver by either Party of a breach or violation
of any provision of this Agreement will not constitute or be construed as a
waiver of any subsequent breach or violation of that provision or as a waiver of
any breach or violation of any other provision of this Agreement.

          17.14 Amendments. This Agreement may not be amended, supplemented
or otherwise modified except by an instrument in writing signed by both Parties.

          17.15 Specific Performance. The Parties agree that breach by
either Party of Sections 10, 12, 13 and 14 could result in irreparable harm to
the other Party. Accordingly, in the event that either Party breaches its
obligations hereunder, the other Party shall be entitled to enjoin any further
breach in addition to any other rights such Party may have at law or in equity.

          17.16 Headings. Any headings and captions included herein are for
convenience of reference only and shall not be used to construe this Agreement.

          17.17 Counterparts. This Agreement may be executed in any number
of counterparts, each of which shall be deemed an original, but all of which
together shall constitute but one in the same instrument.

     IN WITNESS WHEREOF, the Parties hereto, by their duly authorized officers,
have executed this Agreement as of the date first above written.

                                    JOH. VAILLANT GMBH U. CO.


                                    By:       /s/ Manfred Ahle
                                       ----------------------------------
                                    Title: Managing Director


                                    PLUG POWER, LLC


                                    By:       /s Gary Mittleman
                                       ----------------------------------
                                    Title: President and CEO


                                   Exhibit A

                      List of Countries Comprising Europe

Albania Macedonia (The Former Yugoslav Republic of Macedonia) Andorra Malta
Austria Moldova Belarus Monaco Belgium Netherlands Bosnia and Herzegovina Norway
Bulgaria Poland Croatia Portugal Czech Republic Romania Denmark Russia Estonia
San Marino Finland Slovakia France Slovenia Germany Spain Greece Sweden Hungary
Switzerland Iceland Turkey Ireland Turkmenistan Italy Ukraine Latvia United
Kingdom Liechtenstein Vatican City Lithuania Yugoslavia (Serbia and Montenegro)

Luxembourg


                                  Exhibit A1

     Prototype Specifications [To be attached on or before July 1, 2000.]


                                  Exhibit A2

 Initial Product Specifications [To be attached on or before January 1, 2001.]


                                   Exhibit B

     FCS Development Plan [To be attached on or before November 30, 1999.]


                                   Exhibit C

     HS Development Plan [To be attached on or before November '30, 1999.]


                                   Exhibit D

 Integration Development Plan [To be attached on or before November 30,
1999.]


                                   Exhibit E

      FCS Production Plan [To be attached on or before January 1, 2001.]


                                   Exhibit F

       HS Production Plan [To be attached on or before January 1, 2001.]


                                   Exhibit G

Initial Product Production Plan [To be attached on or before January 1, 2001.]