Document:

Exhibit 10.4

 

REGISTRATION RIGHTS AGREEMENT

 

THIS REGISTRATION RIGHTS AGREEMENT
(this “Agreement”) is entered into as of [________], 2021, by and among CleanTech Acquisition Corp., a Delaware
corporation (the “Company”) and the undersigned parties listed under Investor on the signature page hereto (each,
an “Investor” and collectively, the “Investors”).

 

WHEREAS, the Investors and
the Company desire to enter into this Agreement to provide the Investors with certain rights relating to the registration of the securities
held by them as of the date hereof.

 

NOW, THEREFORE, in consideration
of the mutual covenants and agreements set forth herein, and for other good and valuable consideration, the receipt and sufficiency of
which are hereby acknowledged, the parties hereto agree as follows:

 

1. DEFINITIONS.
The following capitalized terms used herein have the following meanings:

 

“Agreement”
means this Agreement, as amended, restated, supplemented, or otherwise modified from time to time.

 

“Board”
means the board of directors of the Company.

 

“Business Combination”
means the acquisition of direct or indirect ownership through a merger, share exchange, asset acquisition, share purchase, recapitalization,
reorganization or other similar type of transaction, of one or more businesses or entities.

 

“Commission”
means the Securities and Exchange Commission, or any other Federal agency then administering the Securities Act or the Exchange Act.

 

“Common Stock”
means the common stock, par value $0.0001 per share, of the Company.

 

“Company”
is defined in the preamble to this Agreement.

 

“Demand Registration”
is defined in Section 2.1.1.

 

“Demanding Holder”
is defined in Section 2.1.1.

 

“Exchange Act”
means the Securities Exchange Act of 1934, as amended, and the rules and regulations of the Commission promulgated thereunder, all as
the same shall be in effect at the time.

 

     

     

    

 

“Form S-3”
is defined in Section 2.3.

 

“Indemnified Party”
is defined in Section 4.3.

 

“Indemnifying
Party” is defined in Section 4.3.

 

“Initial Shares”
means all of the outstanding shares of Common Stock issued prior to the consummation of the Company’s initial public offering.

 

“Investor”
is defined in the preamble to this Agreement.

 

“Investor Indemnified
Party” is defined in Section 4.1.

 

“Maximum Number
of Shares” is defined in Section 2.1.4.

 

“Notices”
is defined in Section 7.4.

 

“Piggy-Back Registration”
is defined in Section 2.2.1.

 

“Private Warrants”
means the aggregate of up to 7,175,000 Warrants CleanTech Sponsor I LLC and CleanTech Investments, LLC, each an Investor, are privately
purchasing simultaneously with the consummation of the Company’s initial public offering.

 

“Register,”
“Registered” and “Registration” mean a registration effected by preparing and filing
a registration statement or similar document in compliance with the requirements of the Securities Act, and the applicable rules and regulations
promulgated thereunder, and such registration statement becoming effective.

 

“Registrable Securities”
means (i) the Initial Shares and (ii) the Private Warrants (and underlying shares of Common Stock). Registrable Securities include any
warrants, shares of capital stock or other securities of the Company issued as a dividend or other distribution with respect to or in
exchange for or in replacement of such Initial Shares and Private Warrants (and underlying shares of Common Stock). As to any particular
Registrable Securities, such securities shall cease to be Registrable Securities when: (a) a Registration Statement with respect to the
sale of such securities shall have become effective under the Securities Act and such securities shall have been sold, transferred, disposed
of or exchanged in accordance with such Registration Statement; (b) such securities shall have been otherwise transferred, new certificates
for them not bearing a legend restricting further transfer shall have been delivered by the Company and subsequent public distribution
of them shall not require registration under the Securities Act; (c) such securities shall have ceased to be outstanding, or (d) the Registrable
Securities are freely saleable under Rule 144 without volume limitations.

 

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“Registration
Statement” means a registration statement filed by the Company with the Commission in compliance with the Securities Act
and the rules and regulations promulgated thereunder for a public offering and sale of equity securities, or securities or other obligations
exercisable or exchangeable for, or convertible into, equity securities (other than a registration statement on Form S-4 or Form S-8,
or their successors, or any registration statement covering only securities proposed to be issued in exchange for securities or assets
of another entity).

 

“Release Date”
means the date on which the Initial Shares are disbursed from escrow pursuant to Section 3 of that certain Stock Escrow Agreement dated
as of [__________], 2021 by and among the Investors and Continental Stock Transfer & Trust Company.

 

“Securities Act”
means the Securities Act of 1933, as amended, and the rules and regulations of the Commission promulgated thereunder, all as the same
shall be in effect at the time.

 

“Underwriter”
means a securities dealer who purchases any Registrable Securities as principal in an underwritten offering and not as part of such dealer’s
market-making activities.

 

“Units”
means the units of the Company, each comprised of one share of Common Stock, one-half of a Warrant entitling the holder to purchase one
share of Common Stock, and one right entitling the holder thereof to receive one-twentieth (1/20) of one share of common stock upon the
consummation of an initial Business Combination.

 

“Warrant(s)”
means the warrants of the Company.

 

2. REGISTRATION RIGHTS.

 

2.1 Demand Registration.

 

2.1.1 Request for
Registration. At any time and from time to time on or after (i) the date that the Company consummates a Business Combination with
respect to the Private Warrants or (ii) three months prior to the Release Date with respect to all other Registrable Securities, but prior
to the five-year anniversary of the effective date of the Company’s Form S-1 Registration Statement (File No. 333-256578) (the “Effective
Date”), the holders of a majority-in-interest of the Initial Shares, may make a written demand for registration under the
Securities Act of all or part of their Private Warrants or other Registrable Securities, as the case may be (a “Demand Registration”).
Any demand for a Demand Registration shall specify the number of shares of Registrable Securities proposed to be sold and the intended
method(s) of distribution thereof. The Company will notify all holders of Registrable Securities of the demand, and each holder of Registrable
Securities who wishes to include all or a portion of such holder’s Registrable Securities in the Demand Registration (each such
holder including shares of Registrable Securities in such registration, a “Demanding Holder”) shall so notify
the Company within fifteen (15) days after the receipt by the holder of the notice from the Company. Upon any such request, the Demanding
Holders shall be entitled to have their Registrable Securities included in the Demand Registration, subject to Section 2.1.4 and the provisos
set forth in Section 3.1.1. The Company shall not be obligated to effect more than three (3) Demand Registrations under this Section 2.1.1
in respect of all Registrable Securities.

 

2.1.2 Effective Registration.
A registration will not count as a Demand Registration until the Registration Statement filed with the Commission with respect to such
Demand Registration has been declared effective and the Company has complied with all of its obligations under this Agreement with respect
thereto; provided, however, that if, after such Registration Statement has been declared effective, the offering of Registrable Securities
pursuant to a Demand Registration is interfered with by any stop order or injunction of the Commission or any other governmental agency
or court, the Registration Statement with respect to such Demand Registration will be deemed not to have been declared effective, unless
and until, (i) such stop order or injunction is removed, rescinded or otherwise terminated, and (ii) a majority-in-interest of the Demanding
Holders thereafter elect to continue the offering; provided, further, that the Company shall not be obligated to file a second Registration
Statement until a Registration Statement that has been filed is counted as a Demand Registration or is terminated.

 

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2.1.3 Underwritten
Offering. If a majority-in-interest of the Demanding Holders so elect and such holders so advise the Company as part of their written
demand for a Demand Registration, the offering of such Registrable Securities pursuant to such Demand Registration shall be in the form
of an underwritten offering. In such event, the right of any holder to include its Registrable Securities in such registration shall be
conditioned upon such holder’s participation in such underwriting and the inclusion of such holder’s Registrable Securities
in the underwriting to the extent provided herein. All Demanding Holders proposing to distribute their Registrable Securities through
such underwriting shall enter into an underwriting agreement in customary form with the Underwriter or Underwriters selected for such
underwriting by a majority-in-interest of the holders initiating the Demand Registration.

 

2.1.4 Reduction of
Offering. If the managing Underwriter or Underwriters for a Demand Registration that is to be an underwritten offering advises the
Company and the Demanding Holders in writing that the dollar amount or number of shares of Registrable Securities which the Demanding
Holders desire to sell, taken together with all other shares of Common Stock or other securities which the Company desires to sell and
the shares of Common Stock, if any, as to which registration has been requested pursuant to written contractual piggy-back registration
rights held by other shareholders of the Company who desire to sell, exceeds the maximum dollar amount or maximum number of shares that
can be sold in such offering without adversely affecting the proposed offering price, the timing, the distribution method, or the probability
of success of such offering (such maximum dollar amount or maximum number of shares, as applicable, the “Maximum Number of
Shares”), then the Company shall include in such registration: (i) first, the Registrable Securities as to which Demand
Registration has been requested by the Demanding Holders (pro rata in accordance with the number of shares that each such Person has requested
be included in such registration, regardless of the number of shares held by each such Person (such proportion is referred to herein as
“Pro Rata”)) that can be sold without exceeding the Maximum Number of Shares; (ii) second, to the extent that
the Maximum Number of Shares has not been reached under the foregoing clause (i), the shares of Common Stock or other securities that
the Company desires to sell that can be sold without exceeding the Maximum Number of Shares; and (iii) third, to the extent that the Maximum
Number of Shares has not been reached under the foregoing clauses (i) and (ii), the shares of Common Stock or other securities for the
account of other persons that the Company is obligated to register pursuant to written contractual arrangements with such persons and
that can be sold without exceeding the Maximum Number of Shares.

 

2.1.5 Withdrawal.
If a majority-in-interest of the Demanding Holders disapprove of the terms of any underwriting or are not entitled to include all of their
Registrable Securities in any offering, such majority-in-interest of the Demanding Holders may elect to withdraw from such offering by
giving written notice to the Company and the Underwriter or Underwriters of their request to withdraw prior to the effectiveness of the
Registration Statement filed with the Commission with respect to such Demand Registration. If the majority-in-interest of the Demanding
Holders withdraws from a proposed offering relating to a Demand Registration, then such registration shall not count as a Demand Registration
provided for in Section 2.1.

 

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2.2 Piggy-Back Registration.

 

2.2.1 Piggy-Back Rights.
If at any time on or after the date the Company consummates a Business Combination the Company proposes to file a Registration Statement
under the Securities Act with respect to an offering of equity securities, or securities or other obligations exercisable or exchangeable
for, or convertible into, equity securities, by the Company for its own account or for shareholders of the Company for their account (or
by the Company and by shareholders of the Company including, without limitation, pursuant to Section 2.1), other than a Registration Statement
(i) filed in connection with any employee stock option or other benefit plan, (ii) for an exchange offer or offering of securities solely
to the Company’s existing shareholders, (iii) for an offering of debt that is convertible into equity securities of the Company
or (iv) for a dividend reinvestment plan, then the Company shall (x) give written notice of such proposed filing to the holders of Registrable
Securities as soon as practicable but in no event less than ten (10) days before the anticipated filing date, which notice shall describe
the amount and type of securities to be included in such offering, the intended method(s) of distribution, and the name of the proposed
managing Underwriter or Underwriters, if any, of the offering, and (y) offer to the holders of Registrable Securities in such notice the
opportunity to register the sale of such number of shares of Registrable Securities as such holders may request in writing within five
(5) days following receipt of such notice (a “Piggy-Back Registration”). The Company shall cause such Registrable
Securities to be included in such registration and shall use its best efforts to cause the managing Underwriter or Underwriters of a proposed
underwritten offering to permit the Registrable Securities requested to be included in a Piggy-Back Registration on the same terms and
conditions as any similar securities of the Company and to permit the sale or other disposition of such Registrable Securities in accordance
with the intended method(s) of distribution thereof. All holders of Registrable Securities proposing to distribute their securities through
a Piggy-Back Registration that involves an Underwriter or Underwriters shall enter into an underwriting agreement in customary form with
the Underwriter or Underwriters selected for such Piggy-Back Registration. Notwithstanding the provisions set forth in the immediately
preceding sentences, the right to a Piggy-Back Registration set forth under this Section 2.2.1 with respect to the Registrable Securities
shall terminate on the seventh anniversary of the Effective Date.

 

2.2.2 Reduction of
Offering. If the managing Underwriter or Underwriters for a Piggy-Back Registration that is to be an underwritten offering advises
the Company and the holders of Registrable Securities in writing that the dollar amount or number of shares of Common Stock which the
Company desires to sell, taken together with the shares of Common Stock, if any, as to which registration has been demanded pursuant to
written contractual arrangements with persons other than the holders of Registrable Securities hereunder, the Registrable Securities as
to which registration has been requested under this Section 2.2, and the shares of Common Stock, if any, as to which registration has
been requested pursuant to the written contractual piggy-back registration rights of other shareholders of the Company, exceeds the Maximum
Number of Shares, then the Company shall include in any such registration:

 

(a) If the
registration is undertaken for the Company’s account: (A) first, the shares of Common Stock or other securities that the Company
desires to sell that can be sold without exceeding the Maximum Number of Shares; (B) second, to the extent that the Maximum Number of
Shares has not been reached under the foregoing clause (A), the shares of Common Stock or other securities, if any, comprised of Registrable
Securities, as to which registration has been requested pursuant to the applicable written contractual piggy-back registration rights
of such security holders, Pro Rata, that can be sold without exceeding the Maximum Number of Shares; and (C) third, to the extent that
the Maximum Number of shares has not been reached under the foregoing clauses (A) and (B), the shares of Common Stock or other securities
for the account of other persons that the Company is obligated to register pursuant to written contractual piggy-back registration rights
with such persons and that can be sold without exceeding the Maximum Number of Shares;

 

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(b) If the
registration is a “demand” registration undertaken at the demand of persons other than either the holders of Registrable Securities,
(A) first, the shares of Common Stock or other securities for the account of the demanding persons that can be sold without exceeding
the Maximum Number of Shares; (B) second, to the extent that the Maximum Number of Shares has not been reached under the foregoing clause
(A), the shares of Common Stock or other securities that the Company desires to sell that can be sold without exceeding the Maximum Number
of Shares; (C) third, to the extent that the Maximum Number of Shares has not been reached under the foregoing clauses (A) and (B), collectively
the shares of Common Stock or other securities comprised of Registrable Securities, Pro Rata, as to which registration has been requested
pursuant to the terms hereof, that can be sold without exceeding the Maximum Number of Shares; and (D) fourth, to the extent that the
Maximum Number of Shares has not been reached under the foregoing clauses (A), (B) and (C), the shares of Common Stock or other securities
for the account of other persons that the Company is obligated to register pursuant to written contractual arrangements with such persons,
that can be sold without exceeding the Maximum Number of Shares.

 

2.2.3 Withdrawal.
Any holder of Registrable Securities may elect to withdraw such holder’s request for inclusion of Registrable Securities in any
Piggy-Back Registration by giving written notice to the Company of such request to withdraw prior to the effectiveness of the Registration
Statement. The Company (whether on its own determination or as the result of a withdrawal by persons making a demand pursuant to written
contractual obligations) may withdraw a Registration Statement at any time prior to the effectiveness of such Registration Statement.
Notwithstanding any such withdrawal, the Company shall pay all expenses incurred by the holders of Registrable Securities in connection
with such Piggy-Back Registration as provided in Section 3.3.

 

2.2.4 Registrations
on Form S-3. The holders of Registrable Securities may at any time and from time to time, request in writing that the Company register
the resale of any or all of such Registrable Securities on Form S-3 or any similar short-form registration which may be available at such
time (“Form S-3”); provided, however, that the Company shall not be obligated to effect such request through
an underwritten offering. Upon receipt of such written request, the Company will promptly give written notice of the proposed registration
to all other holders of Registrable Securities, and, as soon as practicable thereafter, effect the registration of all or such portion
of such holder’s or holders’ Registrable Securities as are specified in such request, together with all or such portion of
the Registrable Securities or other securities of the Company, if any, of any other holder or holders joining in such request as are specified
in a written request given within fifteen (15) days after receipt of such written notice from the Company; provided, however, that the
Company shall not be obligated to effect any such registration pursuant to this Section 2.3: (i) if Form S-3 is not available for such
offering; or (ii) if the holders of the Registrable Securities, together with the holders of any other securities of the Company entitled
to inclusion in such registration, propose to sell Registrable Securities and such other securities (if any) at any aggregate price to
the public of less than $500,000. Registrations effected pursuant to this Section 2.3 shall not be counted as Demand Registrations effected
pursuant to Section 2.1.

 

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3. REGISTRATION PROCEDURES.

 

3.1 Filings; Information.
Whenever the Company is required to effect the registration of any Registrable Securities pursuant to Section 2, the Company shall use
its best efforts to effect the registration and sale of such Registrable Securities in accordance with the intended method(s) of distribution
thereof as expeditiously as practicable, and in connection with any such request:

 

3.1.1 Filing Registration
Statement. The Company shall use its best efforts to, as expeditiously as possible after receipt of a request for a Demand Registration
pursuant to Section 2.1, prepare and file with the Commission a Registration Statement on any form for which the Company then qualifies
or which counsel for the Company shall deem appropriate and which form shall be available for the sale of all Registrable Securities to
be registered thereunder in accordance with the intended method(s) of distribution thereof, and shall use its best efforts to cause such
Registration Statement to become effective and use its best efforts to keep it effective for the period required by Section 3.1.3; provided,
however, that the Company shall have the right to defer any Demand Registration for up to thirty (30) days, and any Piggy-Back Registration
for such period as may be applicable to deferment of any demand registration to which such Piggy-Back Registration relates, in each case
if the Company shall furnish to the holders a certificate signed by the President or Chairman of the Company stating that, in the good
faith judgment of the Board, it would be materially detrimental to the Company and its shareholders for such Registration Statement to
be effected at such time; provided further, however, that the Company shall not have the right to exercise the right set forth in the
immediately preceding proviso more than once in any 365-day period in respect of a Demand Registration hereunder.

 

3.1.2 Copies.
The Company shall, prior to filing a Registration Statement or prospectus, or any amendment or supplement thereto, furnish without charge
to the holders of Registrable Securities included in such registration, and such holders’ legal counsel, copies of such Registration
Statement as proposed to be filed, each amendment and supplement to such Registration Statement (in each case including all exhibits thereto
and documents incorporated by reference therein), the prospectus included in such Registration Statement (including each preliminary prospectus),
and such other documents as the holders of Registrable Securities included in such registration or legal counsel for any such holders
may request in order to facilitate the disposition of the Registrable Securities owned by such holders.

 

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3.1.3 Amendments and
Supplements. The Company shall prepare and file with the Commission such amendments, including post-effective amendments, and supplements
to such Registration Statement and the prospectus used in connection therewith as may be necessary to keep such Registration Statement
effective and in compliance with the provisions of the Securities Act until all Registrable Securities and other securities covered by
such Registration Statement have been disposed of in accordance with the intended method(s) of distribution set forth in such Registration
Statement or such securities have been withdrawn.

 

3.1.4 Notification.
After the filing of a Registration Statement, the Company shall promptly, and in no event more than two (2) business days after such filing,
notify the holders of Registrable Securities included in such Registration Statement of such filing, and shall further notify such holders
promptly and confirm such advice in writing in all events within two (2) business days of the occurrence of any of the following: (i)
when such Registration Statement becomes effective; (ii) when any post-effective amendment to such Registration Statement becomes effective;
(iii) the issuance or threatened issuance by the Commission of any stop order (and the Company shall take all actions required to prevent
the entry of such stop order or to remove it if entered); and (iv) any request by the Commission for any amendment or supplement to such
Registration Statement or any prospectus relating thereto or for additional information or of the occurrence of an event requiring the
preparation of a supplement or amendment to such prospectus so that, as thereafter delivered to the purchasers of the securities covered
by such Registration Statement, such prospectus will not contain an untrue statement of a material fact or omit to state any material
fact required to be stated therein or necessary to make the statements therein not misleading, and promptly make available to the holders
of Registrable Securities included in such Registration Statement any such supplement or amendment; except that before filing with the
Commission a Registration Statement or prospectus or any amendment or supplement thereto, including documents incorporated by reference,
the Company shall furnish to the holders of Registrable Securities included in such Registration Statement and to the legal counsel for
any such holders, copies of all such documents proposed to be filed sufficiently in advance of filing to provide such holders and legal
counsel with a reasonable opportunity to review such documents and comment thereon, and the Company shall not file any Registration Statement
or prospectus or amendment or supplement thereto, including documents incorporated by reference, to which such holders or their legal
counsel shall object.

 

3.1.5 State Securities
Laws Compliance. The Company shall use its best efforts to (i) register or qualify the Registrable Securities covered by the Registration
Statement under such securities or “blue sky” laws of such jurisdictions in the United States as the holders of Registrable
Securities included in such Registration Statement (in light of their intended plan of distribution) may request and (ii) take such action
necessary to cause such Registrable Securities covered by the Registration Statement to be registered with or approved by such other governmental
authorities as may be necessary by virtue of the business and operations of the Company and do any and all other acts and things that
may be necessary or advisable to enable the holders of Registrable Securities included in such Registration Statement to consummate the
disposition of such Registrable Securities in such jurisdictions; provided, however, that the Company shall not be required to qualify
generally to do business in any jurisdiction where it would not otherwise be required to qualify but for this paragraph or subject itself
to taxation in any such jurisdiction.

 

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3.1.6 Agreements for
Disposition. The Company shall enter into customary agreements (including, if applicable, an underwriting agreement in customary form)
and take such other actions as are reasonably required in order to expedite or facilitate the disposition of such Registrable Securities.
The representations, warranties and covenants of the Company in any underwriting agreement which are made to or for the benefit of any
Underwriters, to the extent applicable, shall also be made to and for the benefit of the holders of Registrable Securities included in
such registration statement. No holder of Registrable Securities included in such registration statement shall be required to make any
representations or warranties in the underwriting agreement except, if applicable, with respect to such holder’s organization, good
standing, authority, title to Registrable Securities, lack of conflict of such sale with such holder’s material agreements and organizational
documents, and with respect to written information relating to such holder that such holder has furnished in writing expressly for inclusion
in such Registration Statement.

 

3.1.7 Cooperation.
The principal executive officer of the Company, the principal financial officer of the Company, the principal accounting officer of the
Company and all other officers and members of the management of the Company shall cooperate fully in any offering of Registrable Securities
hereunder, which cooperation shall include, without limitation, the preparation of the Registration Statement with respect to such offering
and all other offering materials and related documents, and participation in meetings with Underwriters, attorneys, accountants and potential
investors.

 

3.1.8 Records.
The Company shall make available for inspection by the holders of Registrable Securities included in such Registration Statement, any
Underwriter participating in any disposition pursuant to such registration statement and any attorney, accountant or other professional
retained by any holder of Registrable Securities included in such Registration Statement or any Underwriter, all financial and other records,
pertinent corporate documents and properties of the Company, as shall be necessary to enable them to exercise their due diligence responsibility,
and cause the Company’s officers, directors and employees to supply all information requested by any of them in connection with
such Registration Statement.

 

3.1.9 Opinions and
Comfort Letters. Upon request, the Company shall furnish to each holder of Registrable Securities included in any Registration Statement
a signed counterpart, addressed to such holder, of (i) any opinion of counsel to the Company delivered to any Underwriter and (ii) any
comfort letter from the Company’s independent public accountants delivered to any Underwriter. In the event no legal opinion is
delivered to any Underwriter, the Company shall furnish to each holder of Registrable Securities included in such Registration Statement,
at any time that such holder elects to use a prospectus, an opinion of counsel to the Company to the effect that the Registration Statement
containing such prospectus has been declared effective and that no stop order is in effect.

 

3.1.10 Earnings Statement.
The Company shall comply with all applicable rules and regulations of the Commission and the Securities Act, and make available to its
shareholders, as soon as practicable, an earnings statement covering a period of twelve (12) months, which earnings statement shall satisfy
the provisions of Section 11(a) of the Securities Act and Rule 158 thereunder.

 

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3.1.11 Listing.
The Company shall use its best efforts to cause all Registrable Securities included in any registration to be listed on such exchanges
or otherwise designated for trading in the same manner as similar securities issued by the Company are then listed or designated or, if
no such similar securities are then listed or designated, in a manner satisfactory to the holders of a majority of the Registrable Securities
included in such registration.

 

3.1.12 Road Show.
If the registration involves the registration of Registrable Securities involving gross proceeds in excess of $5,000,000, the Company
shall use its reasonable efforts to make available senior executives of the Company to participate in customary “road show”
presentations that may be reasonably requested by the Underwriter in any underwritten offering.

 

3.2 Obligation to Suspend
Distribution. Upon receipt of any notice from the Company of the happening of any event of the kind described in Section 3.1.4(iv),
or, in the case of a resale registration on Form S-3 pursuant to Section 2.3 hereof, upon any suspension by the Company, pursuant to a
written insider trading compliance program adopted by the Company’s Board of Directors, of the ability of all “insiders”
covered by such program to transact in the Company’s securities because of the existence of material non-public information, each
holder of Registrable Securities included in any registration shall immediately discontinue disposition of such Registrable Securities
pursuant to the Registration Statement covering such Registrable Securities until such holder receives the supplemented or amended prospectus
contemplated by Section 3.1.4(iv) or the restriction on the ability of “insiders” to transact in the Company’s securities
is removed, as applicable, and, if so directed by the Company, each such holder will deliver to the Company all copies, other than permanent
file copies then in such holder’s possession, of the most recent prospectus covering such Registrable Securities at the time of
receipt of such notice.

 

3.3 Registration Expenses.
The Company shall bear all costs and expenses incurred in connection with any Demand Registration pursuant to Section 2.1, any Piggy-Back
Registration pursuant to Section 2.2, and any registration on Form S-3 effected pursuant to Section 2.3, and all expenses incurred in
performing or complying with its other obligations under this Agreement, whether or not the Registration Statement becomes effective,
including, without limitation: (i) all registration and filing fees; (ii) fees and expenses of compliance with securities or “blue
sky” laws (including fees and disbursements of counsel in connection with blue sky qualifications of the Registrable Securities);
(iii) printing expenses; (iv) the Company’s internal expenses (including, without limitation, all salaries and expenses of its officers
and employees); (v) the fees and expenses incurred in connection with the listing of the Registrable Securities as required by Section
3.1.11; (vi) Financial Industry Regulatory Authority fees; (vii) fees and disbursements of counsel for the Company and fees and expenses
for independent certified public accountants retained by the Company (including the expenses or costs associated with the delivery of
any opinions or comfort letters requested pursuant to Section 3.1.9); (viii) the reasonable fees and expenses of any special experts retained
by the Company in connection with such registration and (ix) the reasonable fees and expenses of one legal counsel selected by the holders
of a majority-in-interest of the Registrable Securities included in such registration. The Company shall have no obligation to pay any
underwriting discounts or selling commissions attributable to the Registrable Securities being sold by the holders thereof, which underwriting
discounts or selling commissions shall be borne by such holders. Additionally, in an underwritten offering, all selling shareholders and
the Company shall bear the expenses of the Underwriter pro rata in proportion to the respective amount of shares each is selling in such
offering.

 

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3.4 Information.
The holders of Registrable Securities shall provide such information as may reasonably be requested by the Company, or the managing Underwriter,
if any, in connection with the preparation of any Registration Statement, including amendments and supplements thereto, in order to effect
the registration of any Registrable Securities under the Securities Act pursuant to Section 2 and in connection with the Company’s
obligation to comply with Federal and applicable state securities laws.

 

4. INDEMNIFICATION
AND CONTRIBUTION.

 

4.1 Indemnification
by the Company. The Company agrees to indemnify and hold harmless each Investor and each other holder of Registrable Securities, and
each of their respective officers, employees, affiliates, directors, partners, members, attorneys and agents, and each person, if any,
who controls an Investor and each other holder of Registrable Securities (within the meaning of Section 15 of the Securities Act or Section
20 of the Exchange Act) (each, an “Investor Indemnified Party”), from and against any expenses, losses, judgments,
claims, damages or liabilities, whether joint or several, arising out of or based upon any untrue statement (or allegedly untrue statement)
of a material fact contained in any Registration Statement under which the sale of such Registrable Securities was registered under the
Securities Act, any preliminary prospectus, final prospectus or summary prospectus contained in the Registration Statement, or any amendment
or supplement to such Registration Statement, or arising out of or based upon any omission (or alleged omission) to state a material fact
required to be stated therein or necessary to make the statements therein not misleading, or any violation by the Company of the Securities
Act or any rule or regulation promulgated thereunder applicable to the Company and relating to action or inaction required of the Company
in connection with any such registration; and the Company shall promptly reimburse the Investor Indemnified Party for any legal and any
other expenses reasonably incurred by such Investor Indemnified Party in connection with investigating and defending any such expense,
loss, judgment, claim, damage, liability or action; provided, however, that the Company will not be liable in any such case to the extent
that any such expense, loss, claim, damage or liability arises out of or is based upon any untrue statement or allegedly untrue statement
or omission or alleged omission made in such Registration Statement, preliminary prospectus, final prospectus, or summary prospectus,
or any such amendment or supplement, in reliance upon and in conformity with information furnished to the Company, in writing, by such
selling holder expressly for use therein. The Company also shall indemnify any Underwriter of the Registrable Securities, their officers,
affiliates, directors, partners, members and agents and each person who controls such Underwriter on substantially the same basis as that
of the indemnification provided above in this Section 4.1.

 

4.2 Indemnification
by Holders of Registrable Securities. Each selling holder of Registrable Securities will, in the event that any registration is being
effected under the Securities Act pursuant to this Agreement of any Registrable Securities held by such selling holder, indemnify and
hold harmless the Company, each of its directors and officers and each Underwriter (if any), and each other selling holder and each other
person, if any, who controls another selling holder or such Underwriter within the meaning of the Securities Act, against any losses,
claims, judgments, damages or liabilities, whether joint or several, insofar as such losses, claims, judgments, damages or liabilities
(or actions in respect thereof) arise out of or are based upon any untrue statement or allegedly untrue statement of a material fact contained
in any Registration Statement under which the sale of such Registrable Securities was registered under the Securities Act, any preliminary
prospectus, final prospectus or summary prospectus contained in the Registration Statement, or any amendment or supplement to the Registration
Statement, or arise out of or are based upon any omission or the alleged omission to state a material fact required to be stated therein
or necessary to make the statement therein not misleading, if the statement or omission was made in reliance upon and in conformity with
information furnished in writing to the Company by such selling holder expressly for use therein, and shall reimburse the Company, its
directors and officers, and each other selling holder or controlling person for any legal or other expenses reasonably incurred by any
of them in connection with investigation or defending any such loss, claim, damage, liability or action. Each selling holder’s indemnification
obligations hereunder shall be several and not joint and shall be limited to the amount of any net proceeds actually received by such
selling holder.

 

    11

     

    

 

4.3 Conduct of Indemnification
Proceedings. Promptly after receipt by any person of any notice of any loss, claim, damage or liability or any action in respect of
which indemnity may be sought pursuant to Section 4.1 or 4.2, such person (the “Indemnified Party”) shall, if a claim in respect
thereof is to be made against any other person for indemnification hereunder, notify such other person (the “Indemnifying
Party”) in writing of the loss, claim, judgment, damage, liability or action; provided, however, that the failure by the
Indemnified Party to notify the Indemnifying Party shall not relieve the Indemnifying Party from any liability which the Indemnifying
Party may have to such Indemnified Party hereunder, except and solely to the extent the Indemnifying Party is actually prejudiced by such
failure. If the Indemnified Party is seeking indemnification with respect to any claim or action brought against the Indemnified Party,
then the Indemnifying Party shall be entitled to participate in such claim or action, and, to the extent that it wishes, jointly with
all other Indemnifying Parties, to assume control of the defense thereof with counsel satisfactory to the Indemnified Party. After notice
from the Indemnifying Party to the Indemnified Party of its election to assume control of the defense of such claim or action, the Indemnifying
Party shall not be liable to the Indemnified Party for any legal or other expenses subsequently incurred by the Indemnified Party in connection
with the defense thereof other than reasonable costs of investigation; provided, however, that in any action in which both the Indemnified
Party and the Indemnifying Party are named as defendants, the Indemnified Party shall have the right to employ separate counsel (but no
more than one such separate counsel) to represent the Indemnified Party and its controlling persons who may be subject to liability arising
out of any claim in respect of which indemnity may be sought by the Indemnified Party against the Indemnifying Party, with the fees and
expenses of such counsel to be paid by such Indemnifying Party if, based upon the written opinion of counsel of such Indemnified Party,
representation of both parties by the same counsel would be inappropriate due to actual or potential differing interests between them.
No Indemnifying Party shall, without the prior written consent of the Indemnified Party, consent to entry of judgment or effect any settlement
of any claim or pending or threatened proceeding in respect of which the Indemnified Party is or could have been a party and indemnity
could have been sought hereunder by such Indemnified Party, unless such judgment or settlement includes an unconditional release of such
Indemnified Party from all liability arising out of such claim or proceeding.

 

4.4 Contribution.

 

4.4.1 If the indemnification
provided for in the foregoing Sections 4.1, 4.2 and 4.3 is unavailable to any Indemnified Party in respect of any loss, claim, damage,
liability or action referred to herein, then each such Indemnifying Party, in lieu of indemnifying such Indemnified Party, shall contribute
to the amount paid or payable by such Indemnified Party as a result of such loss, claim, damage, liability or action in such proportion
as is appropriate to reflect the relative fault of the Indemnified Parties and the Indemnifying Parties in connection with the actions
or omissions which resulted in such loss, claim, damage, liability or action, as well as any other relevant equitable considerations.
The relative fault of any Indemnified Party and any Indemnifying Party shall be determined by reference to, among other things, whether
the untrue or alleged untrue statement of a material fact or the omission or alleged omission to state a material fact relates to information
supplied by such Indemnified Party or such Indemnifying Party and the parties’ relative intent, knowledge, access to information
and opportunity to correct or prevent such statement or omission.

 

4.4.2 The parties hereto
agree that it would not be just and equitable if contribution pursuant to this Section 4.4 were determined by pro rata allocation or by
any other method of allocation which does not take account of the equitable considerations referred to in the immediately preceding Section
4.4.1.

 

4.4.3 The amount paid
or payable by an Indemnified Party as a result of any loss, claim, damage, liability or action referred to in the immediately preceding
paragraph shall be deemed to include, subject to the limitations set forth above, any legal or other expenses incurred by such Indemnified
Party in connection with investigating or defending any such action or claim. Notwithstanding the provisions of this Section 4.4, no holder
of Registrable Securities shall be required to contribute any amount in excess of the dollar amount of the net proceeds (after payment
of any underwriting fees, discounts, commissions or taxes) actually received by such holder from the sale of Registrable Securities which
gave rise to such contribution obligation. No person guilty of fraudulent misrepresentation (within the meaning of Section 11(f) of the
Securities Act) shall be entitled to contribution from any person who was not guilty of such fraudulent misrepresentation.

 

5. RULE 144.

 

5.1 Rule 144. The
Company covenants that it shall file any reports required to be filed by it under the Securities Act and the Exchange Act and shall take
such further action as the holders of Registrable Securities may reasonably request, all to the extent required from time to time to enable
such holders to sell Registrable Securities without registration under the Securities Act within the limitation of the exemptions provided
by Rule 144 under the Securities Act, as such Rules may be amended from time to time, or any similar rule or regulation hereafter adopted
by the Commission.

 

    12

     

    

 

6. MISCELLANEOUS.

 

6.1 Other Registration
Rights. The Company represents and warrants that, except as disclosed in the Company’s registration statement on Form S-1 (File
No. 333-256578), no person, other than the holders of the Registrable Securities, has any right to require the Company to register any
shares of the Company’s capital stock for sale or to include shares of the Company’s capital stock in any registration filed
by the Company for the sale of shares of capital stock for its own account or for the account of any other person.

 

6.2 Limitation on Registration
Rights. Notwithstanding anything herein to the contrary, Chardan Capital Markets, LLC and its related persons may not, with respect
to the Private Warrants purchased by CleanTech Investments, LLC, (i) have more than one (1) Demand Registration at the Company’s
expense, (ii) exercise a Demand Registration more than five (5) years from the Effective Date, and (iii) exercise a Piggy-Back Registration
more than seven (7) years from the Effective Date, as long as Chardan Capital Markets, LLC or any of its related persons are beneficial
owners of the Private Warrants held by CleanTech Investments, LLC.

 

6.3 Assignment; No Third
Party Beneficiaries. This Agreement and the rights, duties and obligations of the Company hereunder may not be assigned or delegated
by the Company in whole or in part. This Agreement and the rights, duties and obligations of the holders of Registrable Securities hereunder
may be freely assigned or delegated by such holder of Registrable Securities in conjunction with and to the extent of any transfer of
Registrable Securities by any such holder. This Agreement and the provisions hereof shall be binding upon and shall inure to the benefit
of each of the parties, to the permitted assigns of the Investors or holder of Registrable Securities or of any assignee of the Investors
or holder of Registrable Securities. This Agreement is not intended to confer any rights or benefits on any persons that are not party
hereto other than as expressly set forth in Article 4 and this Section 7.3.

 

6.4 Notices. All
notices, demands, requests, consents, approvals or other communications (collectively, “Notices”) required or
permitted to be given hereunder or which are given with respect to this Agreement shall be in writing and shall be personally served,
delivered by reputable air courier service with charges prepaid, or transmitted by hand delivery, telegram, telex or facsimile, addressed
as set forth below, or to such other address as such party shall have specified most recently by written notice. Notice shall be deemed
given on the date of service or transmission if personally served or transmitted by telegram, telex or facsimile; provided, that if such
service or transmission is not on a business day or is after normal business hours, then such notice shall be deemed given on the next
business day. Notice otherwise sent as provided herein shall be deemed given on the next business day following timely delivery of such
notice to a reputable air courier service with an order for next-day delivery.

 

    13

     

    

 

To the Company:

CleanTech Acquisition Corp.

207 West 25th Street, 9th Floor

New York, NY 10001

 

with a copy to:

 

Loeb & Loeb LLP

345 Park Avenue

New York, NY 10154

Attn: Giovanni Caruso, Esq.

 

To an Investor, to the address
set forth below such Investor’s name on Exhibit A hereto.

 

6.5 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 that is valid and enforceable.

 

6.6 Counterparts.
This Agreement may be executed in multiple counterparts, each of which shall be deemed an original, and all of which taken together shall
constitute one and the same instrument.

 

6.7 Entire Agreement.
This Agreement (including all agreements entered into pursuant hereto and all certificates and instruments delivered pursuant hereto and
thereto) constitute the entire agreement of the parties with respect to the subject matter hereof and supersede all prior and contemporaneous
agreements, representations, understandings, negotiations and discussions between the parties, whether oral or written.

 

6.8 Term. This Agreement
shall terminate on the seven-year anniversary of the date hereof.

 

6.9 Modifications and
Amendments. No amendment, modification or termination of this Agreement shall be binding upon any party unless executed in writing
by such party.

 

6.10 Titles and Headings.
Titles and headings of sections of this Agreement are for convenience only and shall not affect the construction of any provision of this
Agreement. No amendment, modification or termination of this Agreement shall be binding upon the holders of the Registrable Securities
unless executed in writing by the holders of the majority Registrable Securities.

 

6.11 Waivers and Extensions.
Any party to this Agreement may waive any right, breach or default which such party has the right to waive, provided that such waiver
will not be effective against the waiving party unless it is in writing, is signed by such party, and specifically refers to this Agreement.
Waivers may be made in advance or after the right waived has arisen or the breach or default waived has occurred. Any waiver may be conditional.
No waiver of any breach of any agreement or provision herein contained shall be deemed a waiver of any preceding or succeeding breach
thereof nor of any other agreement or provision herein contained. No waiver or extension of time for performance of any obligations or
acts shall be deemed a waiver or extension of the time for performance of any other obligations or acts.

 

6.12 Remedies Cumulative.
In the event that the Company fails to observe or perform any covenant or agreement to be observed or performed under this Agreement,
the Investor or any other holder of Registrable Securities may proceed to protect and enforce its rights by suit in equity or action at
law, whether for specific performance of any term contained in this Agreement or for an injunction against the breach of any such term
or in aid of the exercise of any power granted in this Agreement or to enforce any other legal or equitable right, or to take any one
or more of such actions, without being required to post a bond. None of the rights, powers or remedies conferred under this Agreement
shall be mutually exclusive, and each such right, power or remedy shall be cumulative and in addition to any other right, power or remedy,
whether conferred by this Agreement or now or hereafter available at law, in equity, by statute or otherwise.

 

6.13 Governing Law.
This Agreement shall be governed by, interpreted under, and construed in accordance with the internal laws of the State of New York applicable
to agreements made and to be performed within the State of New York, without giving effect to any choice-of-law provisions thereof that
would compel the application of the substantive laws of any other jurisdiction.

 

6.14 Waiver of Trial
by Jury. Each party hereby irrevocably and unconditionally waives the right to a trial by jury in any action, suit, counterclaim or
other proceeding (whether based on contract, tort or otherwise) arising out of, connected with or relating to this Agreement, the transactions
contemplated hereby, or the actions of the Investor in the negotiation, administration, performance or enforcement hereof.

 

[REMAINDER OF PAGE INTENTIONALLY LEFT BLANK]

 

    14

     

    

 

IN WITNESS WHEREOF, the parties
have caused this Registration and Stockholder Rights Agreement to be executed and delivered by their duly authorized representatives as
of the date first written above.

 

	 	COMPANY:
	 	 	 
	 	CLEANTECH ACQUISITION CORP.
	 	 	 
	 	By:	 
	 	 	Name: 	Eli Spiro
	 	 	Title:	Chief Executive officer

 

	 	INVESTORS:
	 	 
	 	 
	 	[__]
	 	 
	 	 
	 	[__]
	 	 
	 	 
	 	[__]

 

	 	CLEANTECH SPONSOR I LLC
	 	 	 
	 	By:	 
	 	 	Name: 	Eli Spiro
	 	 	Title:	Managing Member
	 	 	 
	 	CLEANTECH INVESTMENTS, LLC
	 	 	 
	 	By:	 
	 	 	Name: 	[__]
	 	 	Title:	Managing Member

 

[Signature Page to Registration and Stockholder
Rights Agreement]

 

     

     

    

 

EXHIBIT A

 

Name of Investor

 

[__]

 

[__]

 

[__]

 

CleanTech Sponsor I LLC

 

CleanTech Investments, LLCExhibit 10.5

 

[______], 2021

 

CleanTech Acquisition Corp.

207 West 25th Street, 9th Floor

New York, NY 10001

 

Ladies and Gentlemen:

 

CleanTech Acquisition Corp.
(the “Company”), a blank check company formed for the purpose of acquiring one or more businesses or entities (a “Business
Combination”), intends to register its securities under the Securities Act of 1933, as amended (“Securities Act”), in
connection with its initial public offering (“IPO”), pursuant to a registration statement on Form S-1 (“Registration
Statement”).

 

The undersigned hereby commits
that it will purchase an aggregate of [_____] warrants of the Company (“Private Warrants”), at a price of $1.00 per warrant
for an aggregate purchase price of $[_____] (the “Private Warrant Purchase Price”).

 

At least twenty-four (24)
hours prior to the effective date of the Registration Statement, the undersigned will cause the Private Warrant Purchase Price to be delivered
to Loeb & Loeb, LLP (“Loeb”), as escrow agent, by wire transfer as set forth in the instructions attached as Exhibit A
to hold in a non-interest bearing account until the Company consummates the IPO.

 

The consummation of the purchase
and issuance of the Private Warrants shall occur simultaneously with the consummation of the IPO. Simultaneously with the consummation
of the IPO, Continental shall deposit the Private Warrant Purchase Price, without interest or deduction, into the trust fund (“Trust
Fund”) established by the Company for the benefit of the Company’s public stockholders as described in the Registration Statement.

 

Each of the Company and the
undersigned acknowledges and agrees that Loeb is serving hereunder solely as a convenience to the parties to facilitate the purchase of
the Private Warrants.

 

Additionally, the undersigned
agrees:

 

	 	●	not to propose, or vote in favor of, an amendment to the Company’s Amended and Restated Certificate of Incorporation that would affect the substance or timing of the Company’s obligation to redeem 100% of the Company’s shares of Common Stock sold in the IPO if the Company does not complete an initial Business Combination within 12 months (or up to 18 months, if the time to complete a Business Combination is extended as described in the prospectus) from the closing of the IPO, unless the Company provides the holders of shares of Common Stock sold in the IPO with the opportunity to redeem their shares of Common Stock upon approval of any such amendment at a per-share price, payable in cash, equal to the aggregate amount of the Trust Fund, including interest earned on Trust Fund and not previously released to the Company to pay the Company’s franchise and income taxes, divided by the number of then outstanding shares of Common Stock sold in the IPO;

 

     

     

    

 

	 	●	the undersigned will not participate in any liquidation distribution with respect to the Private Warrants (but will participate in liquidation distributions with respect to any units or Common Stock purchased by the undersigned in the IPO or in the open market) if the Company fails to consummate a Business Combination;
	 	 	 
	 	●	that the Private Warrants and underlying securities will not be transferable until 30 days after the consummation of a Business Combination except (a) to officers or directors of the Company, any affiliates or family members of any of officers or directors of the Company, any members of CleanTech Sponsor I LLC or CleanTech Investments, LLC, or any affiliates of CleanTech Sponsor I LLC or CleanTech Investments, LLC; (b) in the case of an individual, by gift to a member of the individual’s immediate family or to a trust, the beneficiary of which is a member of the individual’s immediate family, an affiliate of such person or to a charitable organization; (c) in the case of an individual, by virtue of laws of descent and distribution upon death of the individual; (d) in the case of an individual, pursuant to a qualified domestic relations order; (e) by private sales or transfers made in connection with the consummation of an initial business combination at prices no greater than the price at which the shares or warrants were originally purchased; (f) in the event of  liquidation of the Company prior to the completion of its initial business combination; or (g) by virtue of the laws of Delaware or the applicable limited liability company agreement upon dissolution of CleanTech Sponsor I LLC or CleanTech Investments, LLC, provided, however, that in the case of clauses (a) through (e) or (g), these permitted transferees must enter into a written agreement agreeing to be bound by these transfer restrictions and the other restrictions contained in the insider letter agreements with respect to such securities (including provisions thereof relating to voting, the trust account and liquidation distributions) to be entered into by CleanTech Sponsor I LLC, CleanTech Investments, LLC, and officers, directors and advisors of the Company; and
	 	 	 
	 	●	the Private Warrants will include any additional terms or restrictions as is customary in other similarly structured blank check company offerings or as may be reasonably required by the underwriters in the IPO in order to consummate the IPO, each of which will be set forth in the Registration Statement.

 

The undersigned acknowledges
and agrees that the purchaser of the Private Warrants will execute agreements in form and substance typical for transactions of this nature
necessary to effectuate the foregoing agreements and obligations prior to the consummation of the IPO as are reasonably acceptable to
the undersigned, including but not limited to an insider letter.

 

    2

     

    

 

The undersigned also acknowledges
to be bound by terms of the private warrants described in the warrant agreement between the Company and Continental Stock Transfer &
Trust Company that will be executed in connection with the Company’s IPO.

 

The undersigned hereby represents
and warrants that:

 

(a) it has been advised
that the Private Warrants have not been registered under the Securities Act;

 

(b) it will be acquiring
the Private Warrants for its account for investment purposes only;

 

(c) it has no present
intention of selling or otherwise disposing of the Private Warrants in violation of the securities laws of the United States;

 

(d) it is an “accredited
investor” as defined by Rule 501 of Regulation D promulgated under the Securities Act of 1933, as amended;

 

(e) it has had both the
opportunity to ask questions and receive answers from the officers and directors of the Company and all persons acting on its behalf concerning
the terms and conditions of the offer made hereunder;

 

(f) it is familiar with
the proposed business, management, financial condition and affairs of the Company;

 

(g) it has full power,
authority and legal capacity to execute and deliver this letter and any documents contemplated herein or needed to consummate the transactions
contemplated in this letter; and

 

(h) this letter constitutes
its legal, valid and binding obligation, and is enforceable against it.

 

This letter agreement constitutes
the entire agreement between the undersigned and the Company with respect to the purchase of the Private Warrants, and supersedes all
prior and contemporaneous understandings, agreements, representations and warranties, both written and oral, with respect to the same.

 

	 	Very truly yours,
	 	 
	 	[_____]
	 	 
	 	By:	 
	 	 	Name:  	    
	 	 	Title:	 

 

	Accepted and Agreed:	 
	 	 
	CLEANTECH ACQUISITION CORP.	 
	 	 
	By:	 	 
	 	Name: 	Eli Spiro	 
	 	Title:	Chief Executive Officer	 

 

    3

     

    

 

Exhibit A

 

Wire Instructions

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