WARRANT
      AGREEMENT

    


    Agreement
      made as of _________, 2007 between Tremisis Energy Acquisition Corporation
      II, a
      Delaware corporation, with offices at 11622 Monica Street, Houston, Texas 77024
      (“Company”), and Continental Stock Transfer & Trust Company, a New York
      corporation, with offices at 17 Battery Place, New York, New York 10004
      (“Warrant Agent”).

     

    WHEREAS,
      the Company has received binding commitments from Lawrence S. Coben, Jon Schotz
      and Charles A. Norris (collectively, the “Insiders”) to purchase an aggregate of
      2,000,000 warrants to purchase one share of the Company’s common stock, par
      value $.0001 per share (“Common Stock”) for $6.00, subject to adjustment as
      described herein (“Insider Warrants”); and

     

    WHEREAS,
      the Company is engaged in a public offering (“Public Offering”) of Units and, in
      connection therewith, has determined to issue and deliver up to 10,925,000
      Warrants (“Public Warrants” and together with the Insider Warrants, the
“Warrants”) to the public investors, each Warrant evidencing the right of the
      holder thereof to purchase one share of Common Stock for $6.00, subject to
      adjustment as described herein; and

     

    WHEREAS,
      the Company has filed with the Securities and Exchange Commission a Registration
      Statement on Form S-1, No. 333-145625 (“Reg-istration Statement”), for the
      registration, under the Securities Act of 1933, as amended (“Act”) of, among
      other securities, the Warrants and the Common Stock issuable upon exercise
      of
      the Warrants; and

    


    WHEREAS,
      the Company desires the Warrant Agent to act on behalf of the Company, and
      the
      Warrant Agent is willing to so act, in connection with the issuance,
      regis-tration, transfer, exchange, redemption and exercise of the Warrants;
      and

    


    WHEREAS,
      the Company desires to provide for the form and provisions of the Warrants,
      the
      terms upon which they shall be issued and exercised, and the respective rights,
      limitation of rights, and immunities of the Company, the Warrant Agent, and
      the
      holders of the Warrants; and

    


    WHEREAS,
      all acts and things have been done and performed which are necessary to make
      the
      Warrants, when executed on behalf of the Company and countersigned by or on
      behalf of the Warrant Agent, as provided herein, the valid, binding and legal
      obligations of the Company, and to authorize the execution and delivery of
      this
      Agreement.

     

    
      
         

      

      
         

        
          

        

      

      
         

      

    

    


    NOW,
      THEREFORE, in consideration of the mutual agreements herein contained, the
      parties hereto agree as follows:

    


    1. Appointment
      of Warrant Agent.
      The
      Company hereby appoints the Warrant Agent to act as agent for the Company for
      the Warrants, and the Warrant Agent hereby accepts such appointment and agrees
      to perform the same in accordance with the terms and conditions set forth in
      this Agreement.

    


    2. Warrants.

    


    2.1. Form
      of Warrant.
      Each
      Warrant shall be issued in registered form only, shall be in substantially
      the
      form of Exhibit A hereto, the provisions of which are incorporated herein and
      shall be signed by, or bear the facsimile signature of, the Chairman of the
      Board or President and Treasurer, Secretary or Assistant Secretary of the
      Company and shall bear a facsimile of the Company’s seal. In the event the
      person whose facsimile signature has been placed upon any Warrant shall have
      ceased to serve in the capacity in which such person signed the Warrant before
      such Warrant is issued, it may be issued with the same effect as if he or she
      had not ceased to be such at the date of issuance.

    


    2.2. Effect
      of Countersignature.
      Unless
      and until countersigned by the Warrant Agent pursuant to this Agreement, a
      Warrant shall be invalid and of no effect and may not be exercised by the holder
      thereof.

    


    2.3. Registration.
      

    


    2.3.1. Warrant
      Register.
      The
      Warrant Agent shall maintain books (“Warrant Register”), for the registration of
      original issuance and the registration of transfer of the Warrants. Upon the
      initial issuance of the Warrants, the Warrant Agent shall issue and register
      the
      Warrants in the names of the respective holders thereof in such denom-inations
      and otherwise in accordance with instructions delivered to the Warrant Agent
      by
      the Company.

    


    2.3.2. Registered
      Holder.
      Prior
      to due presentment for registration of transfer of any Warrant, the Company
      and
      the Warrant Agent may deem and treat the person in whose name such Warrant
      shall
      be registered upon the Warrant Register (“registered holder”), as the absolute
      owner of such Warrant and of each Warrant represented thereby (notwithstanding
      any notation of ownership or other writing on the Warrant Certificate made
      by
      anyone other than the Company or the Warrant Agent), for the purpose of any
      exercise thereof, and for all other purposes, and neither the Company nor the
      Warrant Agent shall be affected by any notice to the contrary.

     

    
      
         

      

      
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    2.4. Detachability
      of Warrants.
      The
      securities comprising the Units will not be separately transferable until 90
      days after the date hereof unless Merrill Lynch, Pierce, Fenner & Smith
      Incorporated (“Merrill Lynch”) informs the Company of its decision to allow
      earlier separate trading, but in no event will Merrill Lynch allow separate
      trading of the securities comprising the Units until the Company files a Current
      Report on Form 8-K which includes an audited balance sheet reflecting the
      receipt by the Company of the gross proceeds of the Public Offering including
      the proceeds received by the Company from the exercise of the Underwriter’s
      over-allotment option, if the over-allotment option is exercised prior to the
      filing of the Form 8-K. 

    


    2.5 Insider
      Warrants.
      The
      Insider Warrants will be issued in the same form as the Public Warrants but
      they
(i)
      will
      not be transferable or salable until the Company completes a business
      combination, (ii) will be exercisable on a cashless basis by the Insiders or
      their affiliates if the Company calls the Public Warrants for redemption
      pursuant to Section 6 hereof and (iii) may be exercised for unregistered shares
      if a registration statement relating to the common stock issuable upon exercise
      of the warrants is not effective and current.

     

    3. Terms
      and Exercise of Warrants

    


    3.1. Warrant
      Price.
      Each
      Warrant shall, when counter-signed by the Warrant Agent, entitle the registered
      holder thereof, subject to the provisions of such Warrant and of this Warrant
      Agreement, to purchase from the Company the number of shares of Common Stock
      stated therein, at the price of $6.00 per whole share, subject to the
      adjustments provided in Section 4 hereof and in the last sentence of this
      Section 3.1. The term “Warrant Price” as used in this Warrant Agreement refers
      to the price per share at which Common Stock may be purchased at the time a
      Warrant is exercised. The Company in its sole discretion may lower the Warrant
      Price at any time prior to the Expiration Date for a period of not less than
      10
      business days; provided, however, that any such reduction shall be identical
      in
      percentage terms among all of the Warrants. 

    


    3.2. Duration
      of Warrants.
      A
      Warrant may be exercised only during the period (“Exercise Period”) commencing
      on the later of (i) the consummation by the Company of a merger,
      capital stock exchange, asset acquisition or other similar business combination
      (“Business
      Combination”) (as described more fully in the Company’s Registration Statement)
      and (ii) _________, 2008, and terminating at 5:00 p.m., New York City time
      on
      the earlier to occur of (i) _________, 2012 or (ii) the date fixed for
      redemption of the Warrants as provided in Section 6 of this Agreement
      (“Expiration Date”). Except with respect to the right to receive the Redemption
      Price (as set forth in Section 6 hereunder), each Warrant not exercised on
      or
      before the Expiration Date shall become void, and all rights thereunder and
      all
      rights in respect thereof under this Agreement shall cease at the close of
      business on the Expiration Date. The Company in its sole discretion may extend
      the duration of the Warrants by delaying the Expiration Date; provided, however,
      that the Company will provide notice to registered holders of the Warrants
      of
      such extension of not less than 20 days. 

     

    
      
         

      

      
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    3.3. Exercise
      of Warrants.

    


    3.3.1. Payment.
      Subject
      to the provisions of the Warrant and this Warrant Agreement, a Warrant, when
      countersigned by the Warrant Agent, may be exercised by the registered holder
      thereof by surrendering it, at the office of the Warrant Agent, or at the office
      of its successor as Warrant Agent, in the Borough of Manhattan, City and State
      of New York, with the subscription form, as set forth in the Warrant, duly
      executed, and by paying in full the Warrant Price for each full share of Common
      Stock as to which the Warrant is exercised and any and all applicable taxes
      due
      in connection with the exercise of the Warrant, as follows:

    


    (a)
      in
      cash, good certified check or good bank draft payable to the order of the
      Company (or as otherwise agreed to by the Company);

    


    (b)
      in
      the event of redemption pursuant to Section 6 hereof in which the Company’s
      management has elected to force all holders of Warrants to exercise such
      Warrants on a “cashless basis,” by surrendering the Warrants for that number of
      shares of Common Stock equal to the quotient obtained by dividing (x) the
      product of the number of shares of Common Stock underlying the Warrants,
      multiplied by the difference between the Warrant Price and the “Fair Market
      Value” (defined below) by (y) the Fair Market Value. Solely for purposes of this
      Section 3.3.1, the “Fair Market Value” shall mean the average reported last sale
      price of the Common Stock for the 10 trading days ending on the third trading
      day prior to the date on which the notice of redemption is sent to holders
      of
      Warrant pursuant to Section 6 hereof; or

    


    (c)
      with
      respect to any Insider Warrants, in the event of redemption pursuant to Section
      6 hereof and so long as such Insider Warrants are held by the Insiders or their
      affiliates, by surrendering such Insider Warrants for that number of shares
      of
      Common Stock equal to the quotient obtained by dividing (x) the product of
      the
      number of shares of Common Stock underlying the Warrants, multiplied by the
      difference between the exercise price of the Warrants and the “Fair Market
      Value” by (y) the Fair Market Value. Solely for purposes of this Section 3.3.1,
      the “Fair Market Value” shall mean the average reported last sale price of the
      Common Stock for the 10 trading days ending on the third trading day prior
      to
      the date on which the notice of redemption is sent to holders of Warrant
      pursuant to Section 6 hereof.

     

    
      
         

      

      
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    3.3.2. Issuance
      of Certificates.
      As soon
      as practicable after the exercise of any Warrant and the clearance of the funds
      in payment of the Warrant Price, the Company shall issue to the registered
      holder of such Warrant a certificate or certificates for the number of full
      shares of Common Stock to which he is entitled, registered in such name or
      names
      as may be directed by him, her or it, and if such Warrant shall not have been
      exercised in full, a new countersigned Warrant for the number of shares as
      to
      which such Warrant shall not have been exercised. Subject to Section 7.4 and
      notwithstanding the foregoing, the Company shall not be obligated to deliver
      any
      securities pursuant to the exercise of a Public Warrant and shall have no
      obligation to settle such Public Warrant exercise unless a registration
      statement under the Act with respect to the Common Stock is effective, or in
      the
      opinion of counsel to the Company, the exercise of the Warrants is exempt from
      the registration requirements of the Act and such securities are qualified
      for
      sale or exempt from qualification under applicable securities laws of the states
      or other jurisdictions in which the registered holders reside. In the event
      that
      a registration statement with respect to the Common Stock underlying a Public
      Warrant is not effective under the Act, the holder of such Public Warrant shall
      not be entitled to exercise such Public Warrant and such Public Warrant may
      have
      no value and expire worthless. In no event will the Company be required to
      net
      cash settle the warrant exercise. Public Warrants may not be exercised by,
      or
      securities issued to, any registered holder in any state in which such exercise
      would be unlawful. The shares of common stock issuable upon exercise of Insider
      Warrants shall be unregistered shares. In the event that a registration
      statement is not effective for the exercised Public Warrants, the purchaser
      of a
      unit containing such Public Warrant, will have paid the full purchase price
      for
      the unit solely for the shares included in such unit.

     

    3.3.3. Valid
      Issuance.
      All
      shares of Common Stock issued upon the proper exercise of a Warrant in
      conformity with this Agreement shall be validly issued, fully paid and
      nonassessable.

    


    3.3.4. Date
      of Issuance.
      Each
      person in whose name any such certificate for shares of Common Stock is issued
      shall for all purposes be deemed to have become the holder of record of such
      shares on the date on which the Warrant was surrendered and payment of the
      Warrant Price was made, irrespective of the date of delivery of such
      certificate, except that, if the date of such surrender and payment is a date
      when the stock transfer books of the Company are closed, such person shall
      be
      deemed to have become the holder of such shares at the close of business on
      the
      next succeeding date on which the stock transfer books are open.

     

    
      
         

      

      
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    3.3.5. Intentionally
      Omitted. 

    


    4. Adjustments.

    


    4.1. Stock
      Dividends - Split-Ups.
      If
      after the date hereof, and subject to the provisions of Section 4.6 below,
      the
      number of outstanding shares of Common Stock is increased by a stock dividend
      payable in shares of Common Stock, or by a split-up of shares of Common Stock,
      or other similar event, then, on the effective date of such stock dividend,
      split-up or similar event, the number of shares of Common Stock issuable on
      exercise of each Warrant shall be increased in proportion to such increase
      in
      outstanding shares of Common Stock.

    


    4.2. Aggregation
      of Shares.
      If
      after the date hereof, and subject to the provisions of Section 4.6, the
      number of outstanding shares of Common Stock is decreased by a consolidation,
      combination, reverse stock split or reclassifi-cation of shares of Common Stock
      or other similar event, then, on the effective date of such consolidation,
      combination, reverse stock split, reclassification or similar event, the number
      of shares of Common Stock issuable on exercise of each Warrant shall be
      decreased in proportion to such decrease in outstanding shares of Common
      Stock.

    


    4.3 Adjustments
      in Exercise Price.
      Whenever the number of shares of Common Stock purchasable upon the exercise
      of
      the Warrants is adjusted, as provided in Section 4.1 and 4.2 above, the Warrant
      Price shall be adjusted (to the nearest cent) by multiplying such Warrant Price
      immediately prior to such adjustment by a fraction (x) the numerator of which
      shall be the number of shares of Common Stock purchasable upon the exercise
      of
      the Warrants immediately prior to such adjustment, and (y) the denominator
      of
      which shall be the number of shares of Common Stock so purchasable immediately
      thereafter.

    


    4.4. Replacement
      of Securities upon Reorganization, etc.
      In case
      of any reclassification or reorganization of the outstanding shares of Common
      Stock (other than a change covered by Section 4.1 or 4.2 hereof or that
      solely affects the par value of such shares of Common Stock), or in the case
      of
      any merger or consolidation of the Company with or into another corporation
      (other than a consolidation or merger in which the Company is the continuing
      corporation and that does not result in any reclassification or reorganization
      of the outstanding shares of Common Stock), or in the case of any sale or
      conveyance to another corporation or entity of the assets or other property
      of
      the Company as an entirety or substantially as an entirety in connection with
      which the Company is dissolved, the Warrant holders shall thereafter have the
      right to purchase and receive, upon the basis and upon the terms and conditions
      specified in the Warrants and in lieu of the shares of Common Stock of the
      Company immediately theretofore purchasable and receivable upon the exercise
      of
      the rights represented thereby, the kind and amount of shares of stock or other
      securities or property (including cash) receivable upon such reclassification,
      reorganization, merger or consolidation, or upon a dissolution following any
      such sale or transfer, that the Warrant holder would have received if such
      Warrant holder had exercised his, her or its Warrant(s) immediately prior to
      such event; and if any reclassification also results in a change in shares
      of
      Common Stock covered by Section 4.1 or 4.2, then such adjustment shall be
      made pursuant to Sections 4.1, 4.2, 4.3 and this Section 4.4. The
      provisions of this Section 4.4 shall similarly apply to successive
      reclassifications, reorganizations, mergers or consolidations, sales or other
      transfers.

     

    
      
         

      

      
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    4.5. Notices
      of Changes in Warrant.
      Upon
      every adjustment of the Warrant Price or the number of shares issuable upon
      exercise of a Warrant, the Company shall give written notice thereof to the
      Warrant Agent, which notice shall state the Warrant Price resulting from such
      adjust-ment and the increase or decrease, if any, in the number of shares
      purchasable at such price upon the exercise of a Warrant, setting forth in
      reasonable detail the method of calculation and the facts upon which such
      calculation is based. Upon the occurrence of any event specified in Sections
      4.1, 4.2, 4.3 or 4.4, then, in any such event, the Company shall give written
      notice to each Warrant holder, at the last address set forth for such holder
      in
      the warrant register, of the record date or the effective date of the event.
      Failure to give such notice, or any defect therein, shall not affect the
      legality or validity of such event.

    


    4.6. No
      Fractional Shares.
      Notwithstanding any provi-sion contained in this Warrant Agreement to the
      contrary, the Company shall not issue fractional shares upon exercise of
      Warrants. If, by reason of any adjustment made pursuant to this Section 4,
      the holder of any Warrant would be entitled, upon the exercise of such Warrant,
      to receive a fractional interest in a share, the Company shall, upon such
      exercise, round up or down to the nearest whole number the number of the shares
      of Common Stock to be issued to the Warrant holder.

    


    4.7. Form
      of Warrant.
      The
      form of Warrant need not be changed because of any adjustment pursuant to this
      Section 4, and Warrants issued after such adjustment may state the same Warrant
      Price and the same number of shares as is stated in the Warrants initially
      issued pursuant to this Agreement. However, the Company may at any time in
      its
      sole discretion make any change in the form of Warrant that the Company may
      deem
      appropriate and that does not affect the substance thereof, and any Warrant
      thereafter issued or countersigned, whether in exchange or substitution for
      an
      outstanding Warrant or otherwise, may be in the form as so changed.

     

    
      
         

      

      
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    4.8
       Notice
      of Certain Transactions.
      In the
      event that the Company shall propose to (a) offer the holders of its Common
      Stock rights to subscribe for or to purchase any securities convertible into
      shares of Common Stock or shares of stock of any class or any other securities,
      rights or options, (b) issue any rights, options or warrants entitling the
      holders of Common Stock to subscribe for shares of Common Stock or (c) make
      a tender offer, redemption offer or exchange offer with respect to the Common
      Stock, the Company shall send to the Warrant holders a notice of such proposed
      action or offer. Such notice shall be mailed to the registered holders at their
      addresses as they appear in the Warrant Register, which shall specify the record
      date for the purposes of such dividend, distribution or rights, or the date
      such
      issuance or event is to take place and the date of participation therein by
      the
      holders of Common Stock, if any such date is to be fixed, and shall briefly
      indicate the effect of such action on the Common Stock and on the number and
      kind of any other shares of stock and on other property, if any, and the number
      of shares of Common Stock and other property, if any, issuable upon exercise
      of
      each Warrant and the Warrant Price after giving effect to any adjustment
      pursuant to this Article 4 which would be required as a result of such
      action. Such notice shall be given as promptly as practicable after the Board
      has determined to take any such action and (x) in the case of any action
      covered by clause (a) or (b) above at least 10 days prior to the
      record date for determining the holders of the Common Stock for purposes of
      such
      action or (y) in the case of any other such action at least 20 days
      prior to the date of the taking of such proposed action or the date of
      participation therein by the holders of Common Stock, whichever shall be the
      earlier. 

    


              4.9
       Other
      Events.
      If any
      event occurs as to which the foregoing provisions of this Article 4 are not
      strictly applicable or, if strictly applicable, would not, in the good faith
      judgment of the Board, fairly and adequately protect the purchase rights of
      the
      registered holders of the Warrants in accordance with the essential intent
      and
      principles of such provisions, then the Board shall make such adjustments in
      the
      application of such provisions, in accordance with such essential intent and
      principles, as shall be reasonably necessary, in the good faith opinion of
      the
      Board, to protect such purchase rights as aforesaid. 

     

    
      
         

      

      
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    5. Transfer
      and Exchange of Warrants.

    


    5.1. Registration
      of Transfer.
      The
      Warrant Agent shall register the transfer, from time to time, of any outstanding
      Warrant upon the Warrant Register, upon surrender of such Warrant for transfer,
      properly endorsed with signatures properly guaranteed and accompanied by
      appropriate instructions for transfer. Upon any such transfer, a new Warrant
      representing an equal aggregate number of Warrants shall be issued and the
      old
      Warrant shall be cancelled by the Warrant Agent. The Warrants so cancelled
      shall
      be delivered by the Warrant Agent to the Company from time to time upon
      request.

    


    5.2. Procedure
      for Surrender of Warrants.
      Warrants may be surrendered to the Warrant Agent, together with a written
      request for exchange or transfer, and there-upon the Warrant Agent shall issue
      in exchange therefor one or more new Warrants as requested by the registered
      holder of the Warrants so surrendered, representing an equal aggregate number
      of
      Warrants; provided, however, that in the event that a Warrant surrendered for
      transfer bears a restrictive legend, the Warrant Agent shall not cancel such
      Warrant and issue new Warrants in exchange therefor until the Warrant Agent
      has
      received an opinion of counsel for the Company stating that such transfer may
      be
      made and indicating whether the new Warrants must also bear a restrictive
      legend.

    


    5.3. Fractional
      Warrants.
      The
      Warrant Agent shall not be required to effect any registration of transfer
      or
      exchange which will result in the issuance of a warrant certificate for a
      fraction of a warrant.

    


    5.4. Service
      Charges.
      No
      service charge shall be made for any exchange or registration of transfer of
      Warrants.

    


    5.5. Warrant
      Execution and Countersignature.
      The
      Warrant Agent is hereby authorized to countersign and to deliver, in accordance
      with the terms of this Agreement, the Warrants required to be issued pursuant
      to
      the provisions of this Section 5, and the Company, whenever required by the
      Warrant Agent, will supply the Warrant Agent with Warrants duly executed on
      behalf of the Company for such purpose. 

     

    
      
         

      

      
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    6. Redemption.

    


    6.1. Redemption.
      Subject
      to Section 6.4 hereof, not less than all of the outstanding Warrants may be
      redeemed, at the option of the Company, at any time while they are exercisable
      and so long as an effective registration statement covering the shares of common
      stock issuable upon exercise of the Warrants is current and available throughout
      the “30-day redemption period” (defined below) and prior to their expiration, at
      the office of the Warrant Agent, upon the notice referred to in Section 6.2,
      at
      the price of $.01 per Warrant (“Redemption Price”), provided that the last sales
      price of the Common Stock has been at least $12.00 per share (subject to
      adjustment in accordance with Section 4 hereof), on each of twenty (20) trading
      days within any thirty (30) trading day period ending on the third business
      day
      prior to the date on which notice of redemption is given. 

    


    6.2. Date
      Fixed for, and Notice of, Redemption.
      In the
      event the Company shall elect to redeem all of the Warrants, the Company shall
      fix a date for the redemption. Notice of redemption shall be mailed by first
      class mail, postage prepaid, by the Company not less than 30 days prior to
      the
      date fixed for redemption (the “30-day redemption period”) to the registered
      holders of the Warrants to be redeemed at their last addresses as they shall
      appear on the registration books. Any notice mailed in the manner herein
      provided shall be conclusively presumed to have been duly given whether or
      not
      the registered holder received such notice.

    


    6.3. Exercise
      After Notice of Redemption.
      The
      Warrants may be exercised, for cash (or on a “cashless basis” in accordance with
      Section 3.3.1 of this Agreement) at any time after notice of redemption shall
      have been given by the Company pursuant to Section 6.2 hereof and prior to
      the
      time and date fixed for redemption. In the event the Company determines to
      require all holders of Warrants to exercise their Warrants on a “cashless basis”
pursuant to Section 3.3.1(b), the notice of redemption will contain the
      information necessary to calculate the number of shares of Common Stock to
      be
      received upon exercise of the Warrants, including the “Fair Market Value” in
      such case. On and after the redemption date, the record holder of the Warrants
      shall have no further rights except to receive, upon surrender of the Warrants,
      the Redemption Price.

    


    6.4 Intentionally
      Omitted.

     

    
      
         

      

      
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    7. Other
      Provisions Relating to Rights of Holders of Warrants.

    


    7.1. No
      Rights as Stockholder.
      A
      Warrant does not entitle the registered holder thereof to any of the rights
      of a
      stockholder of the Company, including, without limitation, the right to receive
      dividends, or other distributions, exercise any preemptive rights to vote or
      to
      consent or to receive notice as stockholders in respect of the meetings of
      stockholders or the election of directors of the Company or any other
      matter.

    


    7.2. Lost,
      Stolen, Mutilated, or Destroyed Warrants.
      If any
      Warrant is lost, stolen, mutilated, or destroyed, the Company and the Warrant
      Agent may on such terms as to indemnity or otherwise as they may in their
      discretion impose (which shall, in the case of a mutilated Warrant, include
      the
      surrender thereof), issue a new Warrant of like denomination, tenor, and date
      as
      the Warrant so lost, stolen, mutilated, or destroyed. Any such new Warrant
      shall
      constitute a substitute contractual obligation of the Company, whether or not
      the allegedly lost, stolen, mutilated, or destroyed Warrant shall be at any
      time
      enforceable by anyone.

    


    7.3. Reservation
      of Common Stock.
      The
      Company shall at all times reserve and keep available a number of its authorized
      but unissued shares of Common Stock that will be sufficient to permit the
      exercise in full of all outstanding Warrants issued pursuant to this
      Agreement.

    


    7.4. Registration
      of Common Stock.
      The
      Company agrees that prior to the commencement of the Exercise Period, it shall
      use its best efforts to file with the Securities and Exchange Commission a
      post-effective amendment to the Registration Statement, or a new registration
      statement, for the registration, under the Act, of, and it shall use its best
      efforts to take such action as is necessary to qualify for sale, in those states
      in which the Warrants were initially offered by the Company, the Common Stock
      issuable upon exercise of the Warrants. In either case, the Company will use
      its
      best efforts to cause the same to become effective and to maintain the
      effectiveness of such registration statement until the expiration of the
      Warrants in accordance with the provisions of this Agreement. The
      Warrants shall not be exercisable and the Company shall not be obligated to
      issue Common Stock unless, at the time a holder seeks to exercise the Warrants,
      a prospectus relating to Common Stock issuable upon exercise of the Warrants
      is
      current and the Common Stock has been registered or qualified or deemed to
      be
      exempt under the securities laws of the state of residence of the holder of
      the
      Warrants. The
      provisions of this Section 7.4 may not be modified, amended or deleted
      without the prior written consent of Merrill Lynch.

     

    
      
         

      

      
        11

        
          

        

      

      
         

      

    

    


    8. Concerning
      the Warrant Agent and Other Matters.

    


    8.1. Payment
      of Taxes.
      The
      Company will from time to time promptly pay all taxes and charges that may
      be
      imposed upon the Company or the Warrant Agent in respect of the issuance or
      delivery of shares of Common Stock upon the exercise of Warrants, but the
      Company shall not be obligated to pay any transfer taxes in respect of the
      Warrants or such shares.

    


    8.2. Resignation,
      Consolidation, or Merger of Warrant Agent.

    


    8.2.1. Appointment
      of Successor Warrant Agent.
      The
      Warrant Agent, or any successor to it hereafter appointed, may resign its duties
      and be discharged from all further duties and liabilities hereunder after giving
      sixty (60) days’ notice in writing to the Company. If the office of the Warrant
      Agent becomes vacant by resignation or incapacity to act or otherwise, the
      Company shall appoint in writing a successor Warrant Agent in place of the
      Warrant Agent. If the Company shall fail to make such appointment within a
      period of 30 days after it has been notified in writing of such resignation
      or
      incapacity by the Warrant Agent or by the holder of the Warrant (who shall,
      with
      such notice, submit his Warrant for inspection by the Company), then the holder
      of any Warrant may apply to the Supreme Court of the State of New York for
      the
      County of New York for the appointment of a successor Warrant Agent at the
      Company’s cost. Any successor Warrant Agent, whether appointed by the Company or
      by such court, shall be a corporation organized and existing under the laws
      of
      the State of New York, in good standing and having its principal office in
      the
      Borough of Manhattan, City and State of New York, and authorized under such
      laws
      to exercise corporate trust powers and subject to supervision or examination
      by
      federal or state authority. After appointment, any successor Warrant Agent
      shall
      be vested with all the authority, powers, rights, immunities, duties, and
      obligations of its predecessor Warrant Agent with like effect as if originally
      named as Warrant Agent hereunder, without any further act or deed; but if for
      any reason it becomes necessary or appropriate, the predecessor Warrant Agent
      shall execute and deliver, at the expense of the Company, an instrument
      transferring to such successor Warrant Agent all the authority, powers, and
      rights of such predecessor Warrant Agent hereunder; and upon request of any
      successor Warrant Agent the Company shall make, execute, acknowledge, and
      deliver any and all instruments in writing for more fully and effectually
      vesting in and confirming to such successor Warrant Agent all such authority,
      powers, rights, immunities, duties, and obligations.

    


    8.2.2. Notice
      of Successor Warrant Agent.
      In the
      event a successor Warrant Agent shall be appointed, the Company shall give
      notice thereof to the predecessor Warrant Agent and the transfer agent for
      the
      Common Stock not later than the effective date of any such
      appointment.

     

    
      
         

      

      
        12

        
          

        

      

      
         

      

    

    


    8.2.3. Merger
      or Consolidation of Warrant Agent.
      Any
      corporation into which the Warrant Agent may be merged or with which it may
      be
      consolidated or any corporation resulting from any merger or consolidation
      to
      which the Warrant Agent shall be a party shall be the successor Warrant Agent
      under this Agreement without any further act.

    


    8.3. Fees
      and Expenses of Warrant Agent.

    


    8.3.1. Remuneration.
      The
      Company agrees to pay the Warrant Agent reasonable remuneration for its services
      as such Warrant Agent hereunder and will reimburse the Warrant Agent upon demand
      for all expenditures that the Warrant Agent may reasonably incur in the
      execution of its duties hereunder.

    


    8.3.2. Further
      Assurances.
      The
      Company agrees to perform, execute, acknowledge, and deliver or cause to be
      performed, executed, acknowledged, and delivered all such further and other
      acts, instruments, and assurances as may reasonably be required by the Warrant
      Agent for the carrying out or performing of the provisions of this
      Agreement.

    


    8.4. Liability
      of Warrant Agent.

    


    8.4.1. Reliance
      on Company Statement.
      Whenever in the performance of its duties under this Warrant Agreement, the
      Warrant Agent shall deem it necessary or desirable that any fact or matter
      be
      proved or established by the Company prior to taking or suffering any action
      hereunder, such fact or matter (unless other evidence in respect thereof be
      herein specifically prescribed) may be deemed to be conclusively proved and
      established by a statement signed by the President or Chairman of the Board
      of
      the Company and delivered to the Warrant Agent. The Warrant Agent may rely
      upon
      such statement for any action taken or suffered in good faith by it pursuant
      to
      the provisions of this Agreement.

    


    8.4.2. Indemnity.
      The
      Warrant Agent shall be liable hereunder only for its own negligence, willful
      misconduct or bad faith. The Company agrees to indemnify the Warrant Agent
      and
      save it harmless against any and all liabilities, including judgments, costs
      and
      reasonable counsel fees, for anything done or omitted by the Warrant Agent
      in
      the execution of this Agreement except as a result of the Warrant Agent’s
      negligence, willful misconduct, or bad faith.

    


    
      
         

      

      
        13

        
          

        

      

      
         

      

    

    


    8.4.3. Exclusions.
      The
      Warrant Agent shall have no responsibility with respect to the validity of
      this
      Agreement or with respect to the validity or execution of any Warrant (except
      its countersignature thereof); nor shall it be responsible for any breach by
      the
      Company of any covenant or condition contained in this Agreement or in any
      Warrant; nor shall it be responsible to make any adjustments required under
      the
      provisions of Section 4 hereof or responsible for the manner, method, or amount
      of any such adjustment or the ascertaining of the existence of facts that would
      require any such adjustment; nor shall it by any act hereunder be deemed to
      make
      any representation or warranty as to the authorization or reservation of any
      shares of Common Stock to be issued pursuant to this Agreement or any Warrant
      or
      as to whether any shares of Common Stock will when issued be valid and fully
      paid and nonassessable. 

    


    8.5. Acceptance
      of Agency.
      The
      Warrant Agent hereby accepts the agency established by this Agreement and agrees
      to perform the same upon the terms and conditions herein set forth and among
      other things, shall account promptly to the Company with respect to Warrants
      exercised and concurrently account for, and pay to the Company, all moneys
      received by the Warrant Agent for the purchase of shares of Common Stock through
      the exercise of Warrants.

    


    9. Miscellaneous
      Provisions.

    


    9.1. Successors.
      All the
      covenants and provisions of this Agreement by or for the benefit of the Company
      or the Warrant Agent shall bind and inure to the benefit of their respective
      successors and assigns.

    


    9.2. Notices.
      Any
      notice, statement or demand authorized by this Warrant Agreement to be given
      or
      made by the Warrant Agent or by the holder of any Warrant to or on the Company
      shall be sufficiently given when so delivered if by hand or overnight delivery
      or if sent by certified mail or private courier service within five days after
      deposit of such notice, postage prepaid, addressed (until another address is
      filed in writing by the Company with the Warrant Agent), as
      follows:

    


    Tremisis
      Energy Acquisition Corporation II

    11622
      Monica Street

    Houston,
      Texas 77024

    Attn:
      Lawrence
      S. Coben, Chief Executive Officer

    


    Any
      notice, statement or demand authorized by this Agreement to be given or made
      by
      the holder of any Warrant or by the Company to or on the Warrant Agent shall
      be
      sufficiently given when so delivered if by hand or overnight delivery or if
      sent
      by certified mail or private courier service within five days after deposit
      of
      such notice, postage prepaid, addressed (until another address is filed in
      writing by the Warrant Agent with the Company), as follows:

    


    
      	 	 	 	
              Continental
                Stock Transfer & Trust Company 

              
                17
                  Battery Place

              

              
                New
                  York, New York 10004

              

              
                Attn:
                  Compliance Department

              

            


    

     

    
      
         

      

      
        14

        
          

        

      

      
         

      

    

     

    with
      a
      copy in each case to:


     

    
      	 	 	 	
              
                Graubard
                  Miller

                The
                  Chrysler Building

                405
                  Lexington Avenue

                New
                  York, New York 10174

                Attn:
                  David Alan Miller, Esq.

              

              Facsimile:
                (212) 818-8881

            


    

    


    and

     

    
      	 	 	 	
              
                Andrews
                  Kurth LLP

                600
                  Travis, Suite 4200

                Houston,
                  Texas 77002

                Attn:
                  W.
                  Mark Young,
                  Esq.

                Facsimile:
                  (713)
                  238-7111 

              

            


    

     

    and

     

    
      	 	 	 	
              
                Merrill
                  Lynch & Co., Inc.

                4
                  World Financial Center

                250
                  Vesey Street

                New
                  York, New York 10080

                Attn:
                  

                Facsimile:
                  ( ) - 

              

            


    

    


    9.3. Applicable
      law.
      The
      validity, interpretation, and performance of this Agreement and of the Warrants
      shall be governed in all respects by the laws of the State of New York, without
      giving effect to conflicts of law principles that would result in the
      application of the substantive laws of another jurisdiction. The
      Company hereby agrees that any action, proceeding or claim against it arising
      out of or relating in any way to this Agreement shall be brought and enforced
      in
      the courts of the State of New York or the United States District Court for
      the
      Southern District of New York, and irrevocably submits to such jurisdiction,
      which jurisdiction shall be exclusive. The Company hereby waives any objection
      to such exclusive jurisdiction and that such courts represent an inconvenience
      forum. Any such process or summons to be served upon the Company may be served
      by transmitting a copy thereof by registered or certified mail, return receipt
      requested, postage prepaid, addressed to it at the address set forth in Section
      9.2 hereof. Such mailing shall be deemed personal service and shall be legal
      and
      binding upon the Company in any action, proceeding or claim.

     

    
      
         

      

      
        15

        
          

        

      

      
         

      

    

    


    9.4. Persons
      Having Rights under this Agreement.
      Nothing
      in this Agreement expressed and nothing that may be implied from any of the
      provisions hereof is intended, or shall be construed, to confer upon, or give
      to, any person or corporation other than the parties hereto and the registered
      holders of the Warrants and, for the purposes of Sections 2.5, 6.1, 6.4,
      7.4, 9.2 and 9.8 hereof, Merrill Lynch, any right, remedy, or claim under or
      by
      reason of this Warrant Agreement or of any covenant, condition, stipulation,
      promise, or agreement hereof. Merrill Lynch shall be deemed to be a third-party
      beneficiary of this Agreement with respect to Sections 2.5, 6.1, 6.4, 7.4,
      9.2
      and 9.8 hereof. All covenants, conditions, stipulations, promises, and
      agreements contained in this Warrant Agreement shall be for the sole and
      exclusive benefit of the parties hereto (and Merrill Lynch with respect to
      the
      Sections 2.5, 6.1, 6.4, 7.4, 9.2 and 9.8 hereof) and their successors and
      assigns and of the registered holders of the Warrants.

    


    9.5. Examination
      of the Warrant Agreement.
      A copy
      of this Agreement shall be available at all reasonable times at the office
      of
      the Warrant Agent in the Borough of Manhattan, City and State of New York,
      for
      inspection by the registered holder of any Warrant. The Warrant Agent may
      require any such holder to submit his Warrant for inspection by it.

    


    9.6. Counterparts.
      This
      Agreement may be executed in any number of original or facsimile counterparts
      and each of such counterparts shall for all purposes be deemed to be an
      original, and all such counterparts shall together constitute but one and the
      same instrument.

    


    9.7. Effect
      of Headings.
      The
      Section headings herein are for convenience only and are not part of this
      Warrant Agreement and shall not affect the interpretation thereof.

    


    9.8 Amendments.
      This
      Agreement may be amended by the parties hereto without the consent of any
      registered holder for the purpose of curing any ambiguity, or of curing,
      correcting or supplementing any defective provision contained herein or adding
      or changing any other provisions with respect to matters or questions arising
      under this Agreement as the parties may deem necessary or desirable and that
      the
      parties deem shall not adversely affect the interest of the registered holders.
      All other modifications or amendments, including any amendment to increase
      the
      Warrant Price or shorten the Exercise Period, shall require the written consent
      of the registered holders of a majority of the then outstanding Warrants.
      Notwithstanding the foregoing, the Company may lower the Warrant Price or extend
      the duration of the Exercise Period pursuant to Sections 3.1 and 3.2,
      respectively, without the consent of the registered holders.

     

    
      
         

      

      
        16

        
          

        

      

      
         

      

    

    


    9.9
       Severability.
      This
      Agreement shall be deemed severable, and the invalidity or unenforceability
      of
      any term or provision hereof shall not affect the validity or enforceability
      of
      this Agreement or of any other term or provision hereof. Furthermore, in lieu
      of
      any such invalid or unenforceable term or provision, the parties hereto intend
      that there shall be added as a part of this Agreement a provision as similar
      in
      terms to such invalid or unenforceable provision as may be possible and be
      valid
      and enforceable.

    


    
      
         

      

      
        17

        
          

        

      

      
         

      

    

     


    IN
      WITNESS WHEREOF, this Agreement has been duly executed by the parties hereto
      as
      of the day and year first above written.

    
      	 	 	 
	 	
              TREMISIS
                ENERGY ACQUISITION CORPORATION II

            
	 
 	 
 	 
 
	
            	By:  	
            
	 	
              
Name:
	 	
              Title:
                

            


    

     

    
      	 	 	 
	 	
              CONTINENTAL
                STOCK TRANSFER 

              &
                TRUST COMPANY

            
	 
 	 
 	 
 
	
            	By:  	
            
	 	
              
                

              

              
                Name:
Title:

            


    

     

    
      
         

      

      
        18