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                                                                    Exhibit 10.8

                                 PROMISSORY NOTE
                                 ---------------

$70,000                                                 As of February 17, 2004
                                                        New York, New York

     Tremisis Energy Acquisition Corporation (the "Maker") promises to pay to
the order of Lawrence S. Coben (the "Payee") the principal sum of Seventy
Thousand Dollars ($70,000) in lawful money of the United States of America,
together with interest on the unpaid principal balance of this Note, on the
terms and conditions described below.

     1. Principal. The principal balance of this Note shall be repayable on the
earlier of (i) February 17, 2005 or (ii) the date on which Maker consummates an
initial public offering of its securities.

     2. Interest. No interest shall accrue on the unpaid principal balance of
this Note.

     3. Application of Payments. All payments shall be applied first to payment
in full of any costs incurred in the collection of any sum due under this Note,
including (without limitation) reasonable attorneys' fees, then to the payment
in full of any late charges and finally to the reduction of the unpaid principal
balance of this Note.

     4. Events of Default. The following shall constitute Events of Default:

          (a) Failure to Make Required Payments. Failure by Maker to pay the
principal of or accrued interest on this Note within five (5) business days
following the date when due.

          (b) Voluntary Bankruptcy, Etc. The commencement by Maker of a
voluntary case under the Federal Bankruptcy Code, as now constituted or
hereafter amended, or any other applicable federal or state bankruptcy,
insolvency, reorganization, rehabilitation or other similar law, or the consent
by it to the appointment of or taking possession by a receiver, liquidator,
assignee, trustee, custodian, sequestrator (or other similar official) of Maker
or for any substantial part of its property, or the making by it of any
assignment for the benefit of creditors, or the failure of Maker generally to
pay its debts as such debts become due, or the taking of corporate action by
Maker in furtherance of any of the foregoing.

          (c) Involuntary Bankruptcy, Etc. The entry of a decree or order for
relief by a court having jurisdiction in the premises in respect of maker in an
involuntary case under the Federal Bankruptcy Code, as now or hereafter
constituted, or any other applicable federal or state bankruptcy, insolvency or
other similar law, or appointing a receiver, liquidator, assignee, custodian,
trustee, sequestrator (or similar official) of Maker or for any substantial part
of its property, or ordering the winding-up or liquidation of its affairs, and
the continuance of any such decree or order unstayed and in effect for a period
of 60 consecutive days.

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     5. Remedies.

          (a) Upon the occurrence of an Event of Default specified in Section
4(a), Payee may, by written notice to Maker, declare this Note to be due and
payable, whereupon the principal amount of this Note, and all other amounts
payable thereunder, shall become immediately due and payable without
presentment, demand, protest or other notice of any kind, all of which are
hereby expressly waived, anything contained herein or in the documents
evidencing the same to the contrary notwithstanding.

          (b) Upon the occurrence of an Event of Default specified in Sections
4(b) and 4(c), the unpaid principal balance of, and all other sums payable with
regard to, this Note shall automatically and immediately become due and payable,
in all cases without any action on the part of Payee.

     6. Waivers. Maker and all endorsers and guarantors of, and sureties for,
this Note waive presentment for payment, demand, notice of dishonor, protest,
and notice of protest with regard to the Note, all errors, defects and
imperfections in any proceedings instituted by Payee under the terms of this
Note, and all benefits that might accrue to Maker by virtue of any present or
future laws exempting any property, real or personal, or any part of the
proceeds arising from any sale of any such property, from attachment, levy or
sale under execution, or providing for any stay of execution, exemption from
civil process, or extension of time for payment; and Maker agrees that any real
estate that may be levied upon pursuant to a judgment obtained by virtue hereof,
on any writ of execution issued hereon, may be sold upon any such writ in whole
or in part in any order desired by Payee.

     7. Unconditional Liability. Maker hereby waives all notices in connection
with the delivery, acceptance, performance, default, or enforcement of the
payment of this Note, and agrees that its liability shall be unconditional,
without regard to the liability of any other party, and shall not be affected in
any manner by any indulgence, extension of time, renewal, waiver or modification
granted or consented to by Payee, and consents to any and all extensions of
time, renewals, waivers, or modifications that may be granted by Payee with
respect to the payment or other provisions of this Note, and agree that
additional makers, endorsers, guarantors, or sureties may become parties hereto
without notice to them or affecting their liability hereunder.

     8. Notices. Any notice called for hereunder shall be deemed properly given
if (i) sent by certified mail, return receipt requested, (ii) personally
delivered, (iii) dispatched by any form of private or governmental express mail
or delivery service providing receipted delivery, (iv) sent by telefacsimile or
(v) sent by e-mail, to the following addresses or to such other address as
either party may designate by notice in accordance with this Section:



         If to Maker:

                   Tremisis Energy Acquisition Corporation
                   1775 Broadway
                   Suite 604


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                   New York, New York 10019
                   Attn.:  Lawrence S. Coben, CEO

         If to Payee:

                   Lawrence S. Coben
                   One Ashwood Ct.
                   Atkinson, New Hampshire 03811

Notice shall be deemed given on the earlier of (i) actual receipt by the
receiving party, (ii) the date shown on a telefacsimile transmission
confirmation, (iii) the date on which an e-mail transmission was received by the
receiving party's on-line access provider (iv) the date reflected on a signed
delivery receipt, or (vi) two (2) Business Days following tender of delivery or
dispatch by express mail or delivery service.

     9. Construction. This Note shall be construed and enforced in accordance
with the domestic, internal law, but not the law of conflict of laws, of the
Commonwealth of Pennsylvania.

     10. Severability. Any provision contained in this Note which is prohibited
or unenforceable in any jurisdiction shall, as to such jurisdiction, be
ineffective to the extent of such prohibition or unenforceability without
invalidating the remaining provisions hereof, and any such prohibition or
unenforceability in any jurisdiction shall not invalidate or render
unenforceable such provision in any other jurisdiction.

     IN WITNESS WHEREOF, Maker, intending to be legally bound hereby, has caused
this Note to be duly executed by its Chief Executive Officer the day and year
first above written.


                                   TREMISIS ENERGY ACQUISITION
                                   CORPORATION



                                   By: /s/ Isaac Kier
                                       -------------------------------------
                                       Isaac Kier, Treasurer and Secretary


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