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**Exhibit
  4.88**



Second
  Amendment to "OPTION AGREEMENT FOR PUMPERNICKEL
  GEOTHERMAL PROPERTY, HUMBOLDT COUNTY, NEVADA"
  dated October 12, 2004, as amended February 14, 2006

This
  Second Amendment is made and entered into this 12 day of December, 2007(the
  "Effective Date"), by and between:

Nevada
  Geothermal Power Inc.("NGP"), and its US subsidiary Nevada
  Geothermal Power Company(formerly Noramex Corp.) both of 900-409 Granville
  Street, Vancouver, BC, V6C 1T2;

and

Sierra
  Geothermal Power Corp.("SGP"), a Corporation registered in British
  Columbia located at Suite 500 – 666 Burrard St, Vancouver BC, V6P 3P6
  (prior to December 14, 2006 known as Inovision Solution Inc)

sometimes
  and hereinafter referred to singularly as "Party" or collectively
  as "Parties". Whereas:

A.

The
  Parties entered in an agreement "OPTION AGREEMENT FOR PUMPERNICKEL GEOTHERMAL
  PROPERTY, HUMBOLDT COUNTY, NEVADA" on October 12, 2004, which was amended
  by an Amendment Agreement dated February 14, 2006 (collectively, the "Agreement");
  and

B.

The
  Parties hereby agree to further amend the Agreement as
  provided for herein.

Now
  therefore the Parties hereto agree as follows:

1.
  That section 3.2 of the Agreement is hereby deleted in its entirety and replaced
  by the following:



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3.2
    To exercise the Option and thereby acquire a 50% interest in the
  Property, SGP must:

|                                                                                                           |                                                                                                                                                              |                                                                                                                                    |                                                       
|---------------------------------------------------------------------------------------------------------- | ------------------------------------------------------------------------------------------------------------------------------------------------------------ | ---------------------------------------------------------------------------------------------------------------------------------- | ------------------------------------------------------
|(a)
        make cash payments to NGP totalling $120,000 in accordance with the following
        schedule | (b)
        complete Work Programs on the Property totalling $5,000,000, subject to
        paragraph 3 5 hereof, in accordance with the following schedule: | (c)
        issue to NGP a total of 600,000 common shares in the capital of SGP in
        accordance with the following schedule: | Due
        Dates                                     
|$10,000                                                                                                    | NA                                                                                                                                                           | 100,000
        common
        shares                                                                                              | Previously
        completed on or before Jan 15, 2005
|$10,000                                                                                                    | $400,000                                                                                                                                                     | 100,000
        common
        shares                                                                                              | Previously
        completed on or before Dec 15, 2005
|$10,000                                                                                                    | $600,000                                                                                                                                                     | 100,000
        common
        shares                                                                                              | Previously
        completed on or before Dec 15, 2006
|$20,000                                                                                                    | NA                                                                                                                                                           | 100,000
        common
        shares                                                                                              | To
        be completed on or before Dec 15, 2007     
|$70,000                                                                                                    | $4,000,000                                                                                                                                                   | 200,000
        common
        shares                                                                                              | To
        be completed on orbefore Dec 15, 2008      



2.
  Except as specifically amended by this Second Agreement, the Agreement is hereby
  ratified, approved and confirmed to be in full force and effect.

3.
  NGP hereby confirms that SGP has fulfilled the requirements of the Agreement,
  as amended by this Second Amendment, up to the Effective Date of this Second
  Amendment and is not in default under the terms of the Agreement.

The
  terms of this Second Amendment are accepted and agreed to by the parties as
  of the Effective Date.

|                                    
|------------------------------------
|NEVADA
        GEOTHERMAL POWER INC.

|    |                                             
|--- | --------------------------------------------
|By: | /s/
         Brian Fairbank                 
|    | Brian
        D. Fairbank, President and CEO

|
|





|                                      |                                     
|------------------------------------- | ------------------------------------
|NEVADA
      GEOTHERMAL POWER COMPANY
|By:                                   | /s/
         Brian Fairbank         
|                                      | Brian
        D. Fairbank, President







|                                   |                                           
|---------------------------------- | ------------------------------------------
|SIERRA
      GEOTHERMAL POWER CORP
|By:                                | /s/
          Joel Ronne                  
|                                   | Joel
        Ronne, Vice President and COO











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