Document:

Exhibit 10.10

 

Keyarch Acquisition Corporation

 

August [•], 2021

 

Keyarch Global Sponsor, Ltd.

Walkers Corporate Limited 

190 Elgin Avenue 

George Town, Grand Cayman KY1-9008 

Cayman Islands

 

Ladies and Gentlemen:

 

This letter will confirm our agreement that, commencing
on the effective date (the “Effective Date”) of the registration statement (the “Registration Statement”)
for the initial public offering (the “IPO”) of the securities of Keyarch Acquisition Corporation (the “Company”)
and continuing until the earlier of (i) the consummation by the Company of an initial business combination and (ii) the Company’s
liquidation (in each case as described in the Registration Statement) (such earlier date hereinafter referred to as the “Termination
Date”), Keyarch Global Sponsor, Ltd. (the “Sponsor”) shall take steps directly or indirectly
to make available to the Company certain office space, secretarial and administrative services as may be required by the Company from
time to time, situated at 275 Madison Avenue, 39th floor, New York, New York 10016 (or any successor location). In exchange
therefore, the Company shall pay the Sponsor a sum of up to $10,000 per month commencing on the Effective Date and continuing monthly
thereafter until the Termination Date. The Sponsor hereby agrees that it does not have any right, title, interest or claim of any kind
(a “Claim”) in or to any monies that may be set aside in a trust account (the “Trust Account”)
that may be established in connection with and upon the consummation of the IPO and hereby irrevocably waives any Claim it presently has
or may have in the future as a result of, or arising out of, any negotiations, contracts or agreements with the Company and will not seek
recourse, reimbursement, payment or satisfaction of any Claim against the Trust Account or any monies or other assets in the Trust Account
for any reason whatsoever.

 

This letter agreement constitutes
the entire agreement and understanding of the parties hereto in respect of its subject matter and supersedes all prior understandings,
agreements, or representations by or among the parties hereto, written or oral, to the extent they relate in any way to the subject matter
hereof or the transactions contemplated hereby.

 

This letter agreement may
not be amended, modified or waived as to any particular provision, except by a written instrument executed by the parties hereto.

 

The parties may not assign
this letter agreement and any of their rights, interests, or obligations hereunder without the consent of the other party. Any purported
assignment in violation of this paragraph shall be void and ineffectual and shall not operate to transfer or assign any interest or title
to the purported assignee.

 

This letter agreement shall
be governed by, construed in accordance with, and interpreted pursuant to the laws of the State of New York, without giving effect to
its choice of laws principles that will apply the laws of another jurisdiction.

 

    

     

    

 

This letter agreement may
be executed in one or more counterparts, each of which shall for all purposes be deemed to be an original but all of which together shall
constitute one and the same agreement. Only one such counterpart signed by the party against whom enforceability is sought needs to be
produced to evidence the existence of this letter agreement.

 

[Signature Page Follows]

 

    2

     

    

 

	 	Very truly yours,
	 	 
	 	KEYARCH ACQUISITION CORPORATION
	 	 	 
	 	 	By:	             
	 	Name:
		  Title:
	AGREED TO AND ACCEPTED BY:	 
	 	 
	KEYARCH GLOBAL SPONSOR, LTD.	 
	 	 
	By:	               	 
	Name:	 
	Title:	 

 

    3EX-10.1

 Exhibit 10.1 

Execution Version 
 FORM
OF SUBSCRIPTION AGREEMENT 
 ArcLight Clean Transition Corp. II 

200 Clarendon Street, 55th Floor 
 Boston, Massachusetts 02116

 Ladies and Gentlemen: 
 This Subscription
Agreement (this “Subscription Agreement”) is being entered into as of the date set forth on the signature page hereto, by and between ArcLight Clean Transition Corp. II, a Cayman Islands exempted company
(“ArcLight”), and the undersigned subscriber (the “Investor”), in connection with the Business Combination Agreement, dated as of the date hereof (as may be amended, supplemented or otherwise modified from time to
time, the “Business Combination Agreement”), by and among ArcLight and Opal Fuels LLC, a Delaware limited liability company (the “Company”), pursuant to which, among other things, ArcLight will (directly or
indirectly) acquire equity interests and equity-linked securities of the Company in exchange for the consideration described therein, and ArcLight will become the sole managing member of the Company, on the terms and subject to the conditions
therein (such merger, the “Transaction”). In connection with the Transaction, ArcLight is seeking commitments from interested investors to purchase, following the Domestication (as defined below) and prior to the closing of the
Transaction, shares of ArcLight’s common stock, par value $0.0001 per share (the “Shares”), in a private placement for a purchase price of $10.00 per share (the “Per Share Purchase Price”). On or about the date
of this Subscription Agreement, ArcLight is entering into subscription agreements (the “Other Subscription Agreements” and together with this Subscription Agreement, the “Subscription Agreements”) with certain other
investors (the “Other Investors” and together with the Investor, the “Investors”), severally and not jointly, pursuant to which the Investors, severally and not jointly, have agreed to purchase on the closing date
of the Transaction, inclusive of the Shares subscribed for by the Investor under this Subscription Agreement, an aggregate amount of up to 12,500,000 Shares, at the Per Share Purchase Price. 

Prior to the closing of the Transaction (and as more fully described in the Business Combination Agreement), ArcLight will domesticate as a
Delaware corporation in accordance with Section 388 of the General Corporation Law of the State of Delaware and Part XII of the Cayman Islands Companies Law (2020 Revision) (the “Domestication”). The aggregate purchase price to
be paid by the Investor for the subscribed Shares (as set forth on the signature page hereto) is referred to herein as the “Subscription Amount.” 

In connection therewith, and in consideration of the foregoing and the mutual representations, warranties and covenants, and subject to the
conditions, set forth herein, and intending to be legally bound hereby, each of the Investor and ArcLight acknowledges and agrees as follows: 

1. Subscription. The Investor hereby subscribes for and agrees to purchase from ArcLight, and ArcLight agrees to issue and sell to the
Investor, the number of Shares set forth on the signature page of this Subscription Agreement on the terms and subject to the conditions provided for herein. The Investor acknowledges and agrees that the Investor’s subscription for the Shares
shall be deemed to be accepted by ArcLight only when this Subscription Agreement is signed by a duly authorized person by or on behalf of ArcLight; ArcLight may do so in counterpart form. The Investor acknowledges and agrees that, as a result of the
Domestication, the Shares that will be issued pursuant hereto shall be shares of common stock in a Delaware corporation (and not, for the avoidance of doubt, ordinary shares in a Cayman Islands exempted company). 

2. Closing. The closing of the sale of the Shares contemplated hereby (the “Closing”) is contingent upon the
substantially concurrent consummation of the Transaction. The Closing shall occur on the date of, and substantially concurrently with and conditioned upon the effectiveness of, the Transaction. Upon (a) satisfaction or waiver of the conditions
set forth in Section 3 below and (b) delivery of written notice from (or on behalf of) ArcLight to the Investor (the “Closing Notice”), that ArcLight reasonably expects all conditions to the closing of the Transaction to
be satisfied or waived on a date that is not less than five (5) business days from the date on which the Closing Notice is delivered to the Investor, the Investor shall deliver to ArcLight, two (2) business days prior to the closing date
specified in the Closing Notice (the “Closing Date”), (i) the Subscription Amount by wire transfer of United States dollars in immediately available funds to the account(s) specified by ArcLight in the Closing Notice, to be held by
ArcLight until the Closing pursuant to the terms and conditions herein, and (ii) any other information that is reasonably 
  

 requested in the Closing Notice in order for ArcLight to issue the Investor’s Shares, including without
limitation, the legal name of the person in whose name such Shares are to be issued and a duly executed Internal Revenue Service Form W-9 or W-8 of such person, as
applicable. Notwithstanding the foregoing and for the avoidance of doubt, in the case of a Investor that is an “investment company” registered under the Investment Company Act of 1940, as amended, Investor shall deliver to ArcLight on the
anticipated Closing Date the Subscription Amount for the Shares by wire transfer of U.S. dollars in immediately available funds to the account specified by ArcLight in the Closing Notice (which account shall not be an escrow account) against
delivery to the undersigned of the Shares in book entry form, including evidence from ArcLight’s transfer agent of such issuance, on the Closing Date as described below. On the Closing Date, ArcLight shall issue the number of Shares to the
Investor set forth on the signature page to this Subscription Agreement and subsequently cause such Shares to be registered in book entry form, free and clear of any liens or other restrictions (other than those arising under applicable securities
laws), in the name of the Investor on ArcLight’s share register; provided, however, that ArcLight’s obligation to issue the Shares to the Investor is contingent upon ArcLight having received the Subscription Amount in full
accordance with this Section 2. In the event that the consummation of the Transaction does not occur within three (3) business days after the anticipated Closing Date specified in the Closing Notice, unless otherwise agreed to in writing
by ArcLight and the Investor, ArcLight shall promptly (but in no event later than two (2) business days thereafter) return the Subscription Amount so delivered by the Investor to ArcLight by wire transfer in immediately available funds to the
account specified by the Investor, and any book entries shall be deemed cancelled. Notwithstanding such return or cancellation, unless and until this Subscription Agreement is terminated in accordance with Section 8 herein, the Investor shall
remain obligated (A) to redeliver the Subscription Amount to ArcLight in accordance with the applicable timing described above, to be held in escrow following ArcLight’s delivery to the Investor of a new Closing Notice and (B) to
consummate the Closing immediately prior to or substantially concurrently with the consummation of the Transaction. For purposes of this Subscription Agreement, “business day” shall mean a day, other than a Saturday or Sunday, on which
commercial banks in New York, New York and Boston, Massachusetts are open for the general transaction of business. 
 3. Closing
Conditions. 
 a. The obligation of the parties hereto to consummate the purchase and sale of the Shares pursuant to this Subscription
Agreement is subject to the following conditions: 
 (i) that no applicable governmental authority shall have enacted,
issued, promulgated, enforced or entered any judgment, order, law, rule or regulation (whether temporary, preliminary or permanent) which is then in effect and has the effect of making consummation of the transactions contemplated hereby illegal or
otherwise restraining or prohibiting consummation of the transactions contemplated hereby and no such governmental authority shall have instituted or threatened in writing a proceeding seeking to impose any such restraint or prohibition; 

(ii) the Shares shall have been approved for listing on the Nasdaq Capital Market (“Nasdaq”), subject to
official notice of issuance, and that no suspension of the listing or qualification for offering or sale or trading on Nasdaq or, to ArcLight’s knowledge, no initiation nor threatening of any proceedings for such purposes, shall have occurred
and be continuing; and 
 (iii) all conditions precedent to the closing of the Transaction under the Business Combination
Agreement shall have been satisfied (as determined by the parties to the Business Combination Agreement and other than those conditions under the Business Combination Agreement which, by their nature, are to be satisfied at the closing of the
Transaction, including to the extent that any such condition is dependent upon the consummation of the purchase and sale of the Shares pursuant to this Subscription Agreement) or waived. 

b. The obligation of ArcLight to consummate the issuance and sale of the Shares pursuant to this Subscription Agreement is subject to the
following conditions: 
 (i) that all representations and warranties of the Investor contained in this Subscription Agreement
shall be true and correct in all material respects (other than representations and warranties that are qualified as to materiality, which representations and warranties shall be true 

  
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in all respects) at and as of the Closing Date (unless they specifically speak as of an earlier date, in which case they shall be true and correct in all material respects (other than
representations and warranties that are qualified as to materiality, which representations and warranties shall be true in all respects) as of such date), and consummation of the Closing shall constitute a reaffirmation by the Investor of each of
the representations and warranties of the Investor contained in this Subscription Agreement as of the Closing Date; and 

(ii) that as of the Closing Date the Investor shall have performed, satisfied and complied in all material respects with all
agreements, conditions and covenants required by this Subscription Agreement to have been performed, satisfied or complied with by it at or prior to the Closing. 

c. The obligation of the Investor to consummate the purchase of the Shares pursuant to this Subscription Agreement is subject to the following
additional conditions: 
 (i) all representations and warranties of ArcLight contained in this Subscription Agreement shall
be true and correct in all material respects (other than representations and warranties that are qualified as to materiality, which representations and warranties shall be true in all respects) at and as of the Closing Date, and consummation of the
Closing shall constitute a reaffirmation by ArcLight of each of the representations and warranties of ArcLight contained in this Subscription Agreement as of the Closing Date; 

(ii) ArcLight shall have performed, satisfied or complied in all material respects with all agreements, conditions and
covenants required by this Subscription Agreement to have been performed, satisfied or complied with by it at or prior to the Closing; and 

(iii) no amendment, modification or waiver of the Business Combination Agreement (as the same exists on the date hereof as
provided to the Investor) or any terms thereof shall have occurred that would materially and adversely affect the economic benefits that the Investor would receive under this Subscription Agreement. 

4. Further Assurances. At or prior to the Closing, the parties hereto shall execute and deliver such additional documents and take such
additional actions as the parties reasonably may deem to be practical and necessary in order to consummate the subscription as contemplated by this Subscription Agreement. At or prior to the Closing, the Investor shall deliver to ArcLight a duly
completed and executed Internal Revenue Service Form W-9 or appropriate Form W-8, as applicable. 

5. ArcLight Representations and Warranties. ArcLight represents and warrants to the Investor that: 

a. ArcLight is an exempted company duly incorporated, validly existing and in good standing under the laws of the Cayman Islands (to the extent
such concept exists in such jurisdiction). ArcLight has all power (corporate or otherwise) and authority to own, lease and operate its properties and conduct its business as presently conducted and to enter into, deliver and perform its obligations
under this Subscription Agreement. As of the Closing Date, following the Domestication, ArcLight will be duly incorporated, validly existing as a corporation and in good standing under the laws of the State of Delaware. 

b. As of the Closing Date, the Shares will be duly authorized and, when issued and delivered to the Investor against full payment therefor in
accordance with the terms of this Subscription Agreement, the Shares will be validly issued, fully paid and non-assessable and will not have been issued in violation of or subject to any preemptive or similar
rights created under ArcLight’s certificate of incorporation or bylaws (each as amended on the Closing Date), by contract or under the General Corporation Law of the State of Delaware. 

c. This Subscription Agreement has been duly authorized, executed and delivered by ArcLight and, assuming that this Subscription Agreement
constitutes the valid and binding agreement of the Investor, this Subscription Agreement is enforceable against ArcLight in accordance with its terms, except as may be limited or otherwise affected by (i) bankruptcy, insolvency, fraudulent
conveyance, reorganization, moratorium or other laws relating to or affecting the rights of creditors generally, or (ii) principles of equity, whether considered at law or equity. 

  
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 d. The execution, delivery, and performance of the transactions contemplated by, this
Subscription Agreement, including the issuance and sale of the Shares hereunder, and the compliance by ArcLight with all of the provisions of this Subscription Agreement and the consummation of the transactions contemplated herein will not conflict
with or result in a breach or violation of any of the terms or provisions of, or constitute a default under, or result in the creation or imposition of any lien, charge or encumbrance upon any of the property or assets of ArcLight or any of its
subsidiaries pursuant to the terms of (i) any indenture, mortgage, deed of trust, loan agreement, lease, license or other agreement or instrument to which ArcLight or any of its subsidiaries is a party or by which ArcLight or any of its
subsidiaries is bound or to which any of the property or assets of ArcLight is subject that would reasonably be expected to have a material adverse effect on the business, properties, assets, liabilities, financial condition or results of operations
of ArcLight and its subsidiaries, taken as a whole (a “Material Adverse Effect”) or materially affect the validity of the Shares or the legal authority of ArcLight to comply in all material respects with the terms of this
Subscription Agreement; (ii) result in any violation of the provisions of the organizational documents of ArcLight or its subsidiaries; or (iii) result in any violation of any statute or any judgment, order, rule or regulation of any court
or governmental agency or body, domestic or foreign, having jurisdiction over ArcLight or its subsidiaries or any of their properties that would reasonably be expected to have a Material Adverse Effect or materially affect the validity of the Shares
or the legal authority of ArcLight to comply in all material respects with this Subscription Agreement. 
 e. There are no securities or
instruments issued by ArcLight or to which ArcLight is a party containing anti-dilution or similar provisions that will be triggered by the issuance of the Shares pursuant to this Subscription Agreement or any Other Subscription Agreement, in each
case, that have not been or will not be validly waived on or prior to the Closing Date. 
 f. ArcLight is not in default or violation (and no
event has occurred which, with notice or the lapse of time or both, would constitute a default or violation) of any term, condition or provision of (i) ArcLight’s organizational documents, (ii) any loan or credit agreement, guarantee,
note, bond, mortgage, indenture, lease or other agreement, permit, franchise or license to which ArcLight is now a party or by which ArcLight’s properties or assets are bound or (iii) any statute or any judgment, order, rule or regulation
of any court or governmental agency or body, domestic or foreign, having jurisdiction over ArcLight or any of its properties, except, in the case of clauses (ii) and (iii), for defaults or violations that have not had and would not reasonably
be expected to have, individually or in the aggregate, a Material Adverse Effect. 
 g. ArcLight has made available to the Investor
(including via the Securities and Exchange Commission’s (“SEC”) EDGAR system) a copy of each form, report, statement, schedule, prospectus, proxy, registration statement, and other document, if any, filed by ArcLight with the
SEC since its initial registration of the Shares (the “SEC Documents”). As of their respective dates, all SEC Documents complied in all material respects with the applicable requirements of the Securities Act of 1933,
as amended (the “Securities Act”), and the Securities Exchange Act of 1934, as amended (the “Exchange Act”), and the rules and regulations of the SEC promulgated thereunder applicable to the SEC Documents. None of
the SEC Documents filed under the Exchange Act (except to the extent that information contained in any SEC Document has been superseded by a later timely filed SEC Document) contained, when filed, any untrue statement of a material fact or omitted
to state a material fact required to be stated therein or necessary in order to make the statements therein, in the light of the circumstances under which they were made, not misleading, in the case of any SEC Document that is a registration
statement, or included, when filed, any untrue statement of a material fact or omitted to state a material fact necessary in order to make the statements therein, in the light of the circumstances under which they were made, not misleading, in the
case of all other SEC Documents; provided, that, with respect to information regarding the Company and its subsidiaries included in the proxy statement to be filed by ArcLight with respect to the Transaction or information regarding
ArcLight’s affiliates included in any SEC Document or filed as an exhibit thereto, the representation and warranty in this sentence is made to ArcLight’s knowledge in the case of all other SEC Documents. The financial statements of
ArcLight included in the SEC Documents comply in all material respects with applicable accounting requirements and the rules and regulations of the SEC with respect thereto as in effect at the time of filing and fairly present in all material
respects the financial position of ArcLight as of and for the dates thereof and the results of operations and cash flows for the periods then ended, subject, in the case of unaudited statements, to normal,
year-end audit adjustments. ArcLight has timely filed each report, statement, schedule, prospectus and registration statement that ArcLight was required to file with the SEC since its inception. There are no
outstanding or unresolved comments in comment letters received by ArcLight from the staff of the SEC with respect to any of the SEC Documents. 

  
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 h. ArcLight is not required to obtain any consent, waiver, authorization or order of, give
any notice to, or make any filing or registration with, any court or other federal, state, local or other governmental authority, self-regulatory organization or other person in connection with the execution, delivery and performance by ArcLight of
this Subscription Agreement (including, without limitation, the issuance of the Shares), other than (i) filings with the SEC, (ii) filings required by applicable state securities laws, (iii) filings required in accordance with
Section 13 of this Subscription Agreement, (iv) filings required by the Nasdaq, including with respect to obtaining approval of ArcLight’s shareholders, and (v) filings that the failure of which to obtain would not be reasonably
be expected to have, individually or in the aggregate, a Material Adverse Effect or have a material adverse effect on ArcLight’s ability to consummate the transactions contemplated hereby, including the sale and issuance of the Shares. 

i. Except for such matters as have not had and would not be reasonably likely to have, individually or in the aggregate, a Material Adverse
Effect, as of the date hereof, there is no (i) action, suit, claim or other proceeding, in each case by or before any governmental authority pending, or, to the knowledge of ArcLight, threatened against ArcLight or (ii) judgment, decree,
injunction, ruling or order of any governmental entity or arbitrator outstanding against ArcLight. ArcLight is in compliance with all applicable laws, except where such non-compliance would not reasonably be
expected to have a Material Adverse Effect. 
 j. As of the date of this Subscription Agreement, the authorized capital stock of ArcLight
consists of (i) 500,000,000 Class A ordinary shares, (ii) 50,000,000 Class B ordinary shares and (iii) 5,000,000 preference shares, each with a par value of $0.0001 per share. As of the date of this Subscription Agreement, (A) 31,116,305
Class A ordinary shares of ArcLight are issued and outstanding, (B) 7,779,076 Class B ordinary shares of ArcLight are issued and outstanding, (C) 15,446,522 warrants to purchase Class A ordinary shares of ArcLight are issued and
outstanding, and (D) no preference shares are issued and outstanding. All (1) issued and outstanding Class A ordinary shares and Class B ordinary shares of ArcLight have been duly authorized and validly issued, are fully paid and
are nonassessable and are not subject to preemptive rights and (2) outstanding warrants have been duly authorized and validly issued and are not subject to preemptive rights. Except as set forth above and pursuant to the Other Subscription
Agreements, the Business Combination Agreement and the other agreements and arrangements referred to therein or in the SEC Reports, as of the date hereof, there are no outstanding options, warrants or other rights to subscribe for, purchase or
acquire from ArcLight any Class A ordinary shares, Class B ordinary shares or other equity interests in ArcLight, or securities convertible into or exchangeable or exercisable for such equity interests. As of the date hereof, ArcLight has
no subsidiaries, and does not own, directly or indirectly, interests or investments (whether equity or debt) in any person, whether incorporated or unincorporated. There are no shareholder agreements, voting trusts or other agreements or
understandings to which ArcLight is a party or by which it is bound relating to the voting of any securities of ArcLight, other than (1) as set forth in the SEC Reports and (2) as contemplated by the Business Combination Agreement. 

k. As of the date hereof, the issued and outstanding Shares of ArcLight are registered pursuant to Section 12(b) of the Exchange Act, and
are listed for trading on Nasdaq under the symbol “ACTD” (it being understood that the trading symbol will be changed in connection with the Transaction). Except as disclosed in the SEC Reports, as of the date hereof, there is no suit,
action, proceeding or investigation pending or, to the knowledge of ArcLight, threatened against ArcLight by Nasdaq or the SEC, respectively, to prohibit or terminate the listing of ArcLight’s Shares on Nasdaq or to deregister the Shares under
the Exchange Act. ArcLight has taken no action that is designed to terminate the registration of the Shares under the Exchange Act. 
 l.
ArcLight is not, and immediately after receipt of payment for the Shares will not be, an “investment company” within the meaning of the Investment Company Act of 1940, as amended. 

m. Assuming the accuracy of the Investor’s and Other Investors’ representations and warranties set forth in Section 6 of this
Subscription Agreement, (i) no registration under the Securities Act is required for the offer and sale of the Shares by ArcLight to the Investor under this Subscription Agreement, (ii) the Shares were not offered by any form of general
solicitation or general advertising and (iii) the Shares are not being offered in a manner involving a public offering under, or in a distribution in violation of, the Securities Act or any state securities laws. 

  
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 n. Other than the Other Subscription Agreements, the Business Combination Agreement and any
other agreement contemplated by the Business Combination Agreement, ArcLight has not entered into any side letter or similar agreement with any Investor in connection with such Investor’s direct or indirect investment in ArcLight or with any
Other Investor (other than with respect to terms particular to the regulatory requirements of such subscriber or its affiliates or related funds). No Other Subscription Agreement includes terms and conditions that are more advantageous to any Other
Investor than the Investor hereunder (other than terms particular to the regulatory requirements of such subscriber or its affiliates or related funds), and such Other Subscription Agreements have not been amended or modified in any material respect
following the date of this Subscription Agreement to include any such terms and conditions. 
 o. Other than fees payable to the Placement
Agents (as defined below), ArcLight has not entered into any agreement or arrangement entitling any agent, broker, investment banker, financial advisor or other person to any broker’s or finder’s fee or any other commission or similar fee
in connection with the transactions contemplated by this Subscription Agreement for which the undersigned could become liable. Other than the Placement Agents (as defined below), ArcLight is not aware of any person that has been or will be paid
(directly or indirectly) remuneration for solicitation of purchasers in connection with the sale of any Shares. 
 p. ArcLight and any of its
directors and officers and, to the best of ArcLight’s knowledge, the Company, any of the Company’s directors and officers and any of ArcLight’s and the Company’s employees, representatives, agents and any person acting on its or
their behalf is not (i) a person or entity named on the List of Specially Designated Nationals and Blocked Persons, the Executive Order 13599 List, the Foreign Sanctions Evaders List, or the Sectoral Sanctions Identification List, each of which
is administered by the U.S. Treasury Department’s Office of Foreign Assets Control (“OFAC”), or any other Executive Order issued by the President of the United States and administered by OFAC (collectively “OFAC
Lists”), (ii) owned or controlled by, or acting on behalf of, a person, that is named on an OFAC List, (iii) organized, incorporated, established, located, resident or born in, or a citizen, national, or the government, including any
political subdivision, agency, or instrumentality thereof, of, Cuba, Iran, North Korea, Syria, the Crimea region of Ukraine, or any other country or territory embargoed or subject to substantial trade restrictions by the United States or (iv) a
Designated National as defined in the Cuban Assets Control Regulations, 31 C.F.R. Part 515. 
 q. ArcLight and any of its directors and
officers and, to the best of ArcLight’s knowledge, the Company, any of the Company’s directors and officers and any of ArcLight’s and the Company’s employees, representatives, agents and any person acting on its or their behalf
has not engaged in any activity or conduct which would violate any applicable anti-bribery, anti-corruption or anti-money laundering laws, regulations or rules in any applicable jurisdiction (including, without limitation, the U.S. Foreign Corrupt
Practices Act of 1977, as amended) (the “ABC Legislation”). 
 r. ArcLight and, to the best of ArcLight’s knowledge,
the Company has instituted and maintains systems, policies and procedures designed to prevent violation of the ABC Legislation. 
 s. No
action, suit or proceeding by or before any court or governmental or regulatory agency, authority or body or any arbitrator having jurisdiction over ArcLight or, to the best of ArcLight’s knowledge, the Company with respect to the ABC
Legislation is pending and, to the best of ArcLight’s knowledge, no such actions, suits or proceedings are threatened or contemplated. 

t. ArcLight acknowledges and agrees that, notwithstanding anything herein to the contrary, the Shares may be pledged by Investor in connection
with a bona fide margin agreement, which shall not be deemed to be a transfer, sale or assignment of the Shares hereunder, provided such pledge shall be (i) pursuant to an available exemption from the registration requirements of the Securities
Act or (ii) pursuant to, and in accordance with, a registration statement that is effective under the Securities Act at the time of such pledge, and the Investor effecting a pledge of Shares shall not be required to provide ArcLight with any
notice thereof or otherwise make any delivery to ArcLight pursuant to this Subscription Agreement; provided, however, that none of ArcLight, the Company, or their respective counsels shall be required to take any action (or refrain from taking any
action) in connection with any such pledge and no such pledge or foreclosure by any lender pursuant thereto shall relieve the Investor of its obligations hereunder. 

  
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 6. Investor Representations and Warranties. The Investor represents and warrants to
ArcLight that: 
 a. The Investor (i) is a “qualified institutional buyer” (as defined in Rule 144A under the Securities Act),
an institutional “accredited investor” (within the meaning of Rule 501(a) under the Securities Act), or an “institutional account” (as defined in FINRA Rule 4512(c)), in each case, satisfying the applicable requirements set forth
on Schedule A; (ii) is not an underwriter (as defined in Section 2(a)(11) of the Securities Act); (iii) is acquiring the Shares only for his, her or its own account and not for the account of others, or if the Investor is
subscribing for the Shares as a fiduciary or agent for one or more investor accounts, the Investor has full investment discretion with respect to each such account, and the full power and authority to make the acknowledgements, representations and
agreements herein on behalf of each owner of each such account; and (iv) is not acquiring the Shares with a view to, or for offer or sale in connection with, any distribution thereof in violation of the Securities Act (and shall provide the
requested information set forth on Schedule A). The Investor is not an entity formed for the specific purpose of acquiring the Shares. 

b. The Investor acknowledges and agrees that the Shares are being offered in a transaction not involving any public offering within the meaning
of the Securities Act and that the Shares have not been registered under the Securities Act. The Investor acknowledges and agrees that the Shares may not be offered, resold, transferred, pledged or otherwise disposed of by the Investor absent an
effective registration statement under the Securities Act except (i) to ArcLight or a subsidiary thereof, (ii) to non-U.S. persons pursuant to offers and sales that occur outside the United States
within the meaning of Regulation S under the Securities Act or (iii) pursuant to another applicable exemption from the registration requirements of the Securities Act, and in each of clauses (i) and (iii) in accordance with any applicable
securities laws of the states and other jurisdictions of the United States, and that any certificates representing the Shares shall contain a restrictive legend to such effect. The Investor acknowledges and agrees that the Shares will be subject to
the foregoing transfer restrictions and, as a result of these transfer restrictions, the Investor may not be able to readily offer, resell, transfer, pledge or otherwise dispose of the Shares and may be required to bear the financial risk of an
investment in the Shares for an indefinite period of time. The Investor acknowledges and agrees that the Shares will not be eligible for offer, resale, transfer, pledge or disposition pursuant to Rule 144 promulgated under the Securities Act until
at least one year from the Closing Date. The Investor acknowledges and agrees that it has been advised to consult legal counsel and tax and accounting advisors prior to making any offer, resale, transfer, pledge or disposition of any of the Shares.

 c. The Investor acknowledges and agrees that the Investor is purchasing the Shares from ArcLight. The Investor further acknowledges that
there have been no representations, warranties, covenants and agreements made to the Investor by or on behalf of ArcLight, the Company, any of their respective affiliates or any control persons, officers, directors, employees, partners, agents or
representatives of any of the foregoing or any other person or entity, expressly or by implication, other than those representations, warranties, covenants and agreements of ArcLight expressly set forth in this Subscription Agreement. 

d. The Investor acknowledges and agrees that either (1) the Investor’s acquisition and holding of the Shares will not constitute or
result in a non-exempt prohibited transaction under Section 406 of the Employee Retirement Income Security Act of 1974, as amended (“ERISA”), Section 4975 of the Internal Revenue
Code of 1986, as amended, or any applicable similar law or (2) the Investor is not a Benefit Plan Investor as contemplated by ERISA. 

e. The Investor acknowledges and agrees that the Investor has received and has had an adequate opportunity to review such financial and other
information as the Investor deems necessary in order to make an investment decision with respect to the Shares, including, with respect to ArcLight, the Transaction and the business of the Company and its subsidiaries. Without limiting the
generality of the foregoing, the Investor acknowledges that he, she or it has reviewed the SEC Reports. The Investor acknowledges and agrees that the Investor and the Investor’s professional advisor(s), if any, have had the full opportunity to
ask such questions, receive such answers and obtain such information as the Investor and such Investor’s professional advisor(s), if any, have deemed necessary to make an investment decision with respect to the Shares and have made its own
assessment and satisfied itself concerning relevant tax and other economic considerations. The Investor further acknowledges that the information provided to the Investor may change and ArcLight is under no obligation to inform the Investor
regarding any such changes, except to the extent such changes would reasonably be expected to cause the failure of ArcLight to satisfy a condition to the Investor’s obligations at the Closing set forth in Section 3(c).

  
 7 

 f. The Investor became aware of this offering of the Shares solely by means of direct
contact between the Investor and ArcLight, the Company or a representative of ArcLight or the Company (including the Placement Agents), and the Shares were offered to the Investor solely by direct contact between the Investor and ArcLight, the
Company or a representative of ArcLight or the Company. The Investor did not become aware of this offering of the Shares, nor were the Shares offered to the Investor, by any other means. The Investor acknowledges that the Shares (i) were not
offered by any form of general solicitation or general advertising and (ii) are not being offered in a manner involving a public offering under, or in a distribution in violation of, the Securities Act, or any state securities laws. The
Investor acknowledges that it is not relying upon, and has not relied upon, any statement, representation or warranty made by any person, firm or corporation (including, without limitation, ArcLight, the Company, the Placement Agents, any of their
respective affiliates or any control persons, officers, directors, employees, partners, agents or representatives of any of the foregoing), other than the representations and warranties of ArcLight contained in Section 5 of this Subscription
Agreement, in making its investment or decision to invest in ArcLight. 
 g. The Investor acknowledges that it is aware that there are
substantial risks incident to the purchase and ownership of the Shares, including those set forth in ArcLight’s filings with the SEC. The Investor has such knowledge and experience in financial and business matters as to be capable of
evaluating the merits and risks of an investment in the Shares, and the Investor has sought such accounting, legal and tax advice as the Investor has considered necessary to make an informed investment decision. The Investor is able to fend for
itself in the transactions contemplated herein and has such knowledge and experience in financial and business matters as to be capable of evaluating the merits and risks of the investment. 

h. Alone, or together with any professional advisor(s), the Investor has adequately analyzed and fully considered the risks of an investment in
the Shares and determined that the Shares are a suitable investment for the Investor and that the Investor is able at this time and in the foreseeable future to bear the economic risk of a total loss of the Investor’s investment in ArcLight.
The Investor acknowledges specifically that a possibility of total loss exists. 
 i. In making its decision to purchase the Shares, the
Investor has relied solely upon independent investigation, the Investor Presentation provided to the Investor, and ArcLight’s representations, warranties, covenants and agreements herein. Without limiting the generality of the foregoing, the
Investor has not relied on any statements or other information provided by or on behalf of the Placement Agents or any of their affiliates or any control persons, officers, directors, employees, partners, agents or representatives of any of the
foregoing concerning ArcLight, the Company, the Transaction, the Business Combination Agreement, this Subscription Agreement or the transactions contemplated hereby or thereby, the Shares or the offer and sale of the Shares. 

j. The Investor acknowledges that certain information provided to such Investor was based on projections, and such projections were prepared
based on assumptions and estimates that are inherently uncertain and are subject to a wide variety of significant business, economic and competitive risks and uncertainties that could cause actual results to differ materially from those contained in
the projections. The Investor acknowledges that such information and projections were prepared without the participation of the Placement Agents and that the Placement Agents do not assume responsibility for independent verification of, or the
accuracy or completeness of, such information or projections. 
 k. The Investor acknowledges and agrees that no federal or state agency has
passed upon or endorsed the merits of the offering of the Shares or made any findings or determination as to the fairness of this investment. 

l. The Investor, if not an individual, has been duly formed or incorporated and is validly existing and is in good standing under the laws of
its jurisdiction of formation or incorporation, with power and authority to enter into, deliver and perform its obligations under this Subscription Agreement. 

  
 8 

 m. The execution, delivery and performance by the Investor of this Subscription Agreement
are within the powers of the Investor, have been duly authorized and will not constitute or result in a breach or default under or conflict with any order, ruling or regulation of any court or other tribunal or of any governmental commission or
agency, or any agreement or other undertaking, to which the Investor is a party or by which the Investor is bound, and, if the Investor is not an individual, will not violate any provisions of the Investor’s organizational documents, including,
without limitation, its incorporation or formation papers, bylaws, indenture of trust or partnership or operating agreement, as may be applicable. The signature of the Investor on this Subscription Agreement is genuine, and the signatory, if the
Investor is an individual, has legal competence and capacity to execute the same or, if the Investor is not an individual, the signatory has been duly authorized to execute the same, and, assuming that this Subscription Agreement constitutes the
valid and binding obligation of ArcLight, this Subscription Agreement constitutes a legal, valid and binding obligation of the Investor, enforceable against the Investor in accordance with its terms except as may be limited or otherwise affected by
(i) bankruptcy, insolvency, fraudulent conveyance, reorganization, moratorium or other laws relating to or affecting the rights of creditors generally, and (ii) principles of equity, whether considered at law or equity. 

n. The Investor is not (i) a person or entity named on the List of Specially Designated Nationals and Blocked Persons administered by the
U.S. Treasury Department’s Office of Foreign Assets Control (“OFAC”) or in any Executive Order issued by the President of the United States and administered by OFAC or, any other list of prohibited or restricted parties
promulgated by OFAC, the Department of Commerce, or the Department of State (collectively, the “Sanctions List”), or a person or entity prohibited by any OFAC sanctions program, (ii) owned, directly or indirectly, or controlled
by, or acting on behalf of, one or more persons that are named on the Sanctions List, (iii) a Designated National as defined in the Cuban Assets Control Regulations, 31 C.F.R. Part 515, or (iii) a
non-U.S. shell bank or providing banking services indirectly to a non-U.S. shell bank. The Investor agrees to provide law enforcement agencies, if requested thereby,
such records as required by applicable law, provided that the Investor is permitted to do so under applicable law. If the Investor is a financial institution subject to the Bank Secrecy Act (31 U.S.C. Section 5311 et seq.) (the
“BSA”), as amended by the USA PATRIOT Act of 2001 (the “PATRIOT Act”), and its implementing regulations (collectively, the “BSA/PATRIOT Act”), the Investor maintains policies and procedures
reasonably designed to comply with applicable obligations under the BSA/PATRIOT Act. To the extent required, it maintains policies and procedures reasonably designed for the screening of its investors against the OFAC sanctions programs, including
the Sanctions List. To the extent required by applicable law, the Investor maintains policies and procedures reasonably designed to ensure that the funds held by the Investor and used to purchase the Shares were legally derived. 

o. The Investor acknowledges that no disclosure or offering document has been prepared by Citigroup Global Markets Inc.
(“Citi”), Barclays Capital Inc. (“Barclays”), Credit Suisse (USA) Inc. (“CS”) and BofA Securities, Inc. (“BofA” and together with Citi, Barclays and CS, the “Placement
Agents”) in connection with the offer and sale of the Shares. 
 p. Neither the Placement Agents, nor any of their affiliates nor
any control persons, officers, directors, employees, partners, agents or representatives of any of the foregoing have made any independent investigation with respect to ArcLight, the Company or its subsidiaries or any of their respective businesses,
or the Shares or the accuracy, completeness or adequacy of any information supplied to the Investor by ArcLight. 
 q. In connection with the
issue and purchase of the Shares, the Placement Agents have not acted as the Investor’s financial advisor or fiduciary. 
 r. The
Investor acknowledges and agrees that the Placement Agents shall not be liable to the Investor (including in contract, tort, under federal or state securities laws or otherwise) for any action heretofore or hereafter taken or omitted to be taken by
any of them in connection with this Subscription Agreement. On behalf of it and its affiliates, the Investor releases the Placement Agents in respect of any losses, claims, damages, obligations, penalties, judgments, awards, liabilities, costs,
expenses or disbursements related to this Subscription Agreement. The Investor agrees not to commence any litigation or bring any claim against the Placement Agents in any court or any other forum which relates to, may arise out of, or is in
connection with, this Subscription Agreement. This undertaking is given freely and after obtaining independent legal advice. 

  
 9 

 s. The Investor acknowledges that it is aware that BofA and CS are each a Placement Agent
and are also acting as financial advisor to the Company in connection with the Transaction. 
 t. The Investor has or has commitments to have
and, when required to deliver payment to ArcLight pursuant to Section 2 above, will have, sufficient funds to pay the Subscription Amount and consummate the purchase and sale of the Shares pursuant to this Subscription Agreement. 

u. The Investor acknowledges that (i) the purchase and sale of Shares hereunder meets the exemptions from filing under FINRA Rule
5123(b)(1)(A), (C) or (J) and the institutional customer exemption under FINRA Rule 2111(b); (ii) it is a sophisticated investor, experienced in investing in private equity and capital markets transactions and capable of evaluating investment
risks independently, both in general and with regard to all transactions and investment strategies involving a security or securities; and (iii) it has exercised independent judgment in evaluating its participation in the purchase of the
Securities. 
 v. The Investor acknowledges that the Placement Agents may have acquired, or during the term of the Shares may acquire, non-public information with respect to ArcLight, which the Investor agrees need not be provided to it. 

w. The Investor acknowledges and agrees that ArcLight may complete additional financings in the future to develop its business and fund its
ongoing development, including to finance the Transaction, and such future financings may have a dilutive effect on current securityholders of ArcLight, including the Investor, but there is no assurance that such financing will be available, on
reasonable terms or at all, and if not available, ArcLight may be unable to fund its ongoing development. 
 x. The Investor acknowledges and
agrees that ArcLight continues to review the “Staff Statement on Accounting and Reporting Considerations for Warrants Issued by Special Purpose Acquisition Companies” issued by the SEC staff on April 12, 2021 and its implications,
including on the financial statements and other information included in its SEC Reports, and any restatement, revision or other modification of such filings relating to or arising from such review, any subsequent related agreements or other guidance
from the staff of the SEC shall be deemed not material for purposes of this Subscription Agreement. 
 7. Registration Rights. 

a. In the event that the Shares are not registered in connection with the consummation of the Transaction, ArcLight agrees that, within fifteen
(15) business days after the consummation of the Transaction (the “Filing Deadline”), it will file with the SEC (at the its sole cost and expense) a registration statement registering the offering of the resale of the Shares
(the “Registration Statement”), and it shall use its commercially reasonable efforts to have the Registration Statement declared effective as soon as practicable after the filing thereof, but no later than the earlier of
(i) sixty (60) calendar days after the filing thereof (or ninety (90) calendar days after the filing thereof if the SEC notifies ArcLight that it will “review” the Registration Statement) and (ii) ten (10) business days
after ArcLight is notified (orally or in writing, whichever is earlier) by the SEC that the Registration Statement will not be “reviewed” or will not be subject to further review (such date, the “Effectiveness Date”).
ArcLight agrees to cause such Registration Statement, or another shelf registration statement that includes the Shares to be sold pursuant to this Subscription Agreement, to remain effective until the earliest of (i) the third anniversary of
the Closing, (ii) the date on which the Investor ceases to hold any Shares issued pursuant to this Subscription Agreement, or (iii) the first date on which the Investor is able to sell all of its Shares issued pursuant to this Subscription
Agreement (or shares received in exchange therefor) without restriction under Rule 144 promulgated under the Securities Act, including without limitation, any volume or manner of sale restrictions that may be applicable to affiliates under Rule 144
and without the requirement for ArcLight to be in compliance with the current public information required under Rule 144(c)(1) (or Rule 144(i)(2), if applicable) (the earliest of (i)–(iii) being the “Expiration”). Prior to the
Expiration, ArcLight will use commercially reasonable efforts to qualify the Shares for listing on the applicable stock exchange. The Investor agrees to disclose its ownership and any other information reasonably requested to ArcLight upon request
to assist it in making the determination described above. Notwithstanding the foregoing, if the SEC prevents ArcLight from including any or all of the shares proposed to be registered under the Registration Statement due to limitations on the use of
Rule 415 under the Securities Act for the resale of the Shares by the applicable stockholders or otherwise, such Registration Statement shall register for resale such number of Shares which is equal to the maximum number of

  
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Shares as is permitted to be registered by the SEC. In such event, the number of Shares to be registered for each selling stockholder named in the Registration Statement shall be reduced pro rata
among all such selling stockholders, and Arclight shall use its commercially reasonable efforts to file with the SEC, as promptly as allowed by the SEC, one or more registration statements to register the resale of those Shares that were not
registered in the initial Registration Statement, as so amended, and to have the Registration Statement declared effective as soon as practicable after the filing thereof. The Investor acknowledges and agrees that ArcLight may suspend the use of any
such registration statement if it determines that in order for such registration statement not to contain a material misstatement or omission, an amendment thereto would be needed to include information that would at that time not otherwise be
required in a current, quarterly or annual report under the Exchange Act, provided that (A) ArcLight shall not so delay filing or so suspend the use of the Registration Statement for a period of more than sixty (60) consecutive days
or more than a total of ninety (90) calendar days, in each case in any three hundred sixty (360) day period, (B) ArcLight shall have a bona fide business purpose for not making such information public and (C) ArcLight shall use
commercially reasonable efforts to make such registration statement available for the sale by the Investor of such securities as soon as practicable thereafter. ArcLight’s obligations to include the Shares issued pursuant to this Subscription
Agreement (or shares issued in exchange therefor) for resale in the Registration Statement are contingent upon the Investor furnishing in writing to ArcLight such information regarding the Investor, the securities of ArcLight held by the Investor
and the intended method of disposition of such Shares, which shall be limited to non-underwritten public offerings, as shall be reasonably requested by ArcLight to effect the registration of such Shares, and
shall execute such documents in connection with such registration as ArcLight may reasonably request that are customary of a selling stockholder in similar situations (collectively, the “Questionnaire”),
provided, however, that the Investor shall not in connection with the foregoing be required to execute any lock-up or similar agreement or otherwise be subject to any contractual restriction on
the ability to transfer the Shares. ArcLight will provide a draft of the Registration Statement to the Investor for review at least two (2) business days in advance of filing the Registration Statement. The Investor shall not be identified as a
statutory underwriter in the Registration Statement unless in response to a comment or request from the staff of the SEC or another regulatory agency; provided, however, that if the SEC requests that the Investor be identified as a
statutory underwriter in the Registration Statement, the Investor will have an opportunity to withdraw from the Registration Statement. For purposes of clarification, any failure by ArcLight to file the Registration Statement by the Filing Deadline
or to effect such Registration Statement by the Effectiveness Date shall not otherwise relieve ArcLight of its obligations to file or effect the Registration Statement as set forth in this Section 7. 

b. Prior to the Expiration, ArcLight shall advise the Investor within three (3) business days (at ArcLight’s expense): (i) when a
Registration Statement or any post-effective amendment thereto has become effective; (ii) of any request by the SEC for amendments or supplements to any Registration Statement or the prospectus included therein or for additional information;
(iii) of the issuance by the SEC of any stop order suspending the effectiveness of any Registration Statement or the initiation of any proceedings for such purpose; (iv) of the receipt by ArcLight of any notification with respect to the
suspension of the qualification of the Shares included therein for sale in any jurisdiction or the initiation or threatening of any proceeding for such purpose; and (v) subject to the provisions in this Subscription Agreement, of a suspension
pursuant to Section 7(a) or the occurrence of any event that requires the making of any changes in any Registration Statement or prospectus so that, as of such date, the statements therein are not misleading and do not omit to state a material
fact required to be stated therein or necessary to make the statements therein (in the case of a prospectus, in the light of the circumstances under which they were made) not misleading (provided that any such notice pursuant to this
Section 7(b)(v) shall solely provide that the use of the Registration Statement or prospectus has been suspended without setting forth the reason for such suspension and shall not contain any material
non-public information regarding ArcLight and which notice shall not be subject to any duty of confidentiality). ArcLight shall use its commercially reasonable efforts to obtain the withdrawal of any order
suspending the effectiveness of any Registration Statement as soon as reasonably practicable. Upon the occurrence of any event contemplated in clauses (i) through (v) above, except for such times as ArcLight is permitted hereunder to suspend,
and has suspended, the use of a prospectus forming part of a registration statement, ArcLight shall use its commercially reasonable efforts to as soon as reasonably practicable prepare a post-effective amendment to such registration statement or a
supplement to the related prospectus, or file any other required document so that, as thereafter delivered to purchasers of the Shares included therein, such prospectus will not include any untrue statement of a material fact or omit to state any
material fact necessary to make the statements therein, in the light of the circumstances under which they were made, not misleading. The Investor agrees that it will immediately discontinue offers and sales of the Shares using a Registration
Statement until the Investor receives copies of a supplemental or amended prospectus that corrects the misstatement(s) or omission(s) referred to above in clause (iv) 

  
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and receives notice that any post-effective amendment has become effective or unless otherwise notified by ArcLight that it may resume such offers and sales (which notice shall not contain any
material non-public information regarding ArcLight and which notice shall not be subject to any duty of confidentiality). If so directed by ArcLight, the Investor will deliver to ArcLight or, in the
Investor’s sole discretion destroy, all copies of the prospectus covering the Shares in the Investor’s possession; provided, however, that this obligation to deliver or destroy all copies of the prospectus covering the Shares
shall not apply (x) to the extent the Investor is required to retain a copy of such prospectus in order to comply with applicable legal, regulatory, self-regulatory or professional requirements or in accordance with a bona fide pre-existing document retention policy or (y) to copies stored electronically on archival servers as a result of automatic data back-up. 

c. Prior to the Expiration, ArcLight will use commercially reasonable efforts to file all reports necessary to enable the undersigned to resell
the Shares pursuant to the Registration Statement. For as long as the Investor holds Shares, ArcLight will use commercially reasonable efforts to file all reports necessary to enable the undersigned to resell the Shares pursuant to Rule 144 of the
Securities Act (when Rule 144 of the Securities Act becomes available to the Investor). In addition, in connection with any proposed sale, assignment, transfer or other disposition of the Shares by the Investor pursuant to Rule 144, or pursuant to
any other exemption under the Securities Act, or in connection with a sale or transfer in the manner described in the Registration Statement such that the Shares held by the Investor become freely tradable and upon compliance by the Investor with
the requirements of this Subscription Agreement, if requested by the Investor, ArcLight shall provide the Transfer Agent with customary documentation reasonably acceptable to ArcLight and the Transfer Agent, including, if required by the Transfer
Agent, an opinion of ArcLight’s counsel, in a form reasonably acceptable to ArcLight and the Transfer Agent, as required to remove any restrictive legends related to the book entry account holding such Shares and make a new, unlegended entry
for such book entry Shares sold or disposed of without restrictive legends within two (2) trading days of any such request therefor from the Investor, provided that ArcLight and the Transfer Agent have timely received from the Investor
customary representations and other documentation reasonably acceptable to ArcLight and the Transfer Agent in connection therewith. 
 d.
Indemnification. 
 (i) ArcLight agrees to indemnify and hold harmless, to the extent permitted by law, the Investor, its
directors, trustees, officers, employees, affiliates, advisers, and agents, and each person who controls the Investor (within the meaning of the Section 15 of the Securities Act or Section 20 of the Exchange Act) and each affiliate of the
Investor (within the meaning of Rule 405 under the Securities Act) from and against any and all losses, claims, damages, liabilities and expenses (including, without limitation, any reasonable attorneys’ fees and expenses incurred in connection
with defending or investigating any such action or claim) caused by any untrue or alleged untrue statement of material fact contained in any Registration Statement, prospectus included in any Registration Statement or preliminary prospectus or any
amendment thereof or supplement thereto or any omission or alleged omission of a material fact required to be stated therein or necessary to make the statements therein not misleading, except insofar as and to the extent, but only to the extent, the
same are caused by or contained in any information furnished in writing to ArcLight by or on behalf of the Investor expressly for use therein, including the contents of any Questionnaire. ArcLight shall notify the Investor promptly of the
institution, threat or assertion of any proceeding arising from or based on the matters for which it is obligated to indemnify and hold harmless under this Section 7(d)(i) of which ArcLight receives notice in writing. 

(ii) The Investor agrees, severally and not jointly with any person that is a party to the Other Subscription Agreements, to
indemnify and hold harmless ArcLight, its directors, trustees, officers, affiliates, advisers, and agents and each person who controls ArcLight (within the meaning of Section 15 of the Securities Act and Section 20 of the Exchange Act)
against any losses, claims, damages, liabilities and expenses (including, without limitation, reasonable attorneys’ fees) resulting from any untrue statement of material fact contained in the Registration Statement, prospectus or preliminary
prospectus or any amendment thereof or supplement thereto or any omission of a material fact required to be stated therein (in the case of any prospectus, or preliminary prospectus or supplement thereto, in light of the circumstances under which
they were made) or necessary to make the statements therein not misleading, but only to the extent that such untrue 

  
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statement or omission is contained in any information or affidavit so furnished in writing by the Investor (including any Questionnaire furnished by the Investor) expressly for use therein. In no
event shall the liability of the Investor be greater in amount than the dollar amount of the net proceeds received by the Investor upon the sale of the Shares purchased pursuant to this Subscription Agreement giving rise to such indemnification
obligation. The Investor shall notify ArcLight promptly of the institution, threat or assertion of any proceeding arising from or based on the matters for which it is obligated to indemnify under this Section 7(d)(ii) of which the
Investor receives notice in writing. 
 (iii) Any person entitled to indemnification hereunder shall (1) give prompt
written notice to the indemnifying party of any claim with respect to which it seeks indemnification (provided that the failure to give prompt notice shall not impair any person’s right to indemnification hereunder to the extent such failure
has not materially prejudiced the indemnifying party) and unless in such indemnified party’s reasonable judgment a conflict of interest between such indemnified and indemnifying parties exists with respect to such claim, permit such
indemnifying party to assume the defense of such claim with counsel reasonably satisfactory to the indemnified party. If such defense is assumed, the indemnifying party shall not be subject to any liability for any settlement made by the indemnified
party without its consent (but such consent shall not be unreasonably withheld, conditioned or delayed). An indemnifying party who is not entitled to, or elects not to assume the defense of a claim shall not be obligated to pay the fees and expenses
of more than one counsel for all parties indemnified by such indemnifying party with respect to such claim, unless in the reasonable judgment of legal counsel to any indemnified party a conflict of interest exists between such indemnified party and
any other of such indemnified parties with respect to such claim. No indemnifying party shall, without the consent of the indemnified party, consent to the entry of any judgment or enter into any settlement which cannot be settled in all respects by
the payment of money (and such money is so paid by the indemnifying party pursuant to the terms of such settlement) or which settlement includes a statement or admission of fault and culpability on the part of such indemnified party or which does
not include as an unconditional term thereof the giving by the claimant or plaintiff to such indemnified party of a release from all liability in respect to such claim or litigation. 

(iv) The indemnification provided for under this Subscription Agreement shall remain in full force and effect regardless of any
investigation made by or on behalf of the indemnified party or any officer, director, employee, agent, affiliate or controlling person of such indemnified party and shall survive the transfer of the Shares purchased pursuant to this Subscription
Agreement. 
 (v) If the indemnification provided under this Section 7(d) from the indemnifying party is unavailable or
insufficient to hold harmless an indemnified party in respect of any losses, claims, damages, liabilities and expenses referred to herein, then the indemnifying party, in lieu of indemnifying the indemnified party, shall contribute to the amount
paid or payable by the indemnified party as a result of such losses, claims, damages, liabilities and expenses in such proportion as is appropriate to reflect the relative fault of the indemnifying party and the indemnified party, as well as any
other relevant equitable considerations provided, however, the liability of the Investor shall be limited to the net proceeds received by the Investor from the sale of the Shares giving rise to such indemnification obligation. The relative
fault of the indemnifying party and indemnified party shall be determined by reference to, among other things, whether any action in question, including any untrue or alleged untrue statement of a material fact or omission or alleged omission to
state a material fact, was made by, or relates to information supplied by, such indemnifying party or indemnified party, and the indemnifying party’s and indemnified party’s relative intent, knowledge, access to information and opportunity
to correct or prevent such action. The amount paid or payable by a party as a result of the losses or other liabilities referred to above shall be deemed to include, subject to the limitations set forth above, any legal or other fees, charges or
expenses reasonably incurred by such party in connection with any investigation or proceeding. No person guilty of fraudulent misrepresentation (within the meaning of Section 11(f) of the Securities Act) shall be entitled to contribution
pursuant to this Section 7(d) from any person who was not guilty of such fraudulent misrepresentation. In no event shall the liability of the Investor be 

  
 13 

 
greater in amount than the dollar amount of the net proceeds received by the Investor upon the sale of the Shares purchased pursuant to this Subscription Agreement giving rise to such
contribution obligation. Notwithstanding anything to the contrary herein, in no event will any party be liable for consequential, special, exemplary or punitive damages in connection with this Subscription Agreement or the transactions contemplated
hereby. 
 8. Termination. This Subscription Agreement shall terminate and be void and of no further force and effect, and all rights
and obligations of the parties hereunder shall terminate without any further liability on the part of any party in respect thereof, upon the earliest to occur of (a) such date and time as the Business Combination Agreement is terminated in
accordance with its terms without being consummated, (b) upon the mutual written agreement of each of the parties hereto to terminate this Subscription Agreement, (c) ArcLight’s notification to the Investor in writing that it has
abandoned its plans to move forward with the Transaction, (d) the earlier of (i) one hundred eighty (180) days after the date of this Subscription Agreement and (ii) thirty (30) days after the Termination Date (as defined in the
Business Combination Agreement, as in effect as of the date hereof), in each case if the Closing has not occurred by such date, other than as a result of a breach of the Investor’s obligations hereunder, or (e) if any of the conditions to
Closing set forth in Section 3 of this Subscription Agreement are (i) not satisfied or waived prior to the Closing, or (ii) not capable of being satisfied on the Closing and, in each case of (i) and (ii), as a result thereof, the
transactions contemplated by this Subscription Agreement will not be and are not consummated at the Closing (the termination events described in clauses (a)–(e) above, collectively, the “Termination Events”); provided
that nothing herein will relieve any party from liability for any willful breach hereof prior to the time of termination, and each party will be entitled to any remedies at law or in equity to recover losses, liabilities or damages arising from any
such willful breach. ArcLight shall notify the Investor of the termination of the Business Combination Agreement promptly after the termination of such agreement. Upon the occurrence of any Termination Event, this Subscription Agreement shall be
void and of no further effect and any monies paid by the Investor to ArcLight in connection herewith shall promptly (and in any event within one (1) business day) following the Termination Event be returned to the Investor. 

9. Trust Account Waiver. The Investor acknowledges that ArcLight is a blank check company with the powers and privileges to effect a
merger, asset acquisition, reorganization or similar business combination involving ArcLight and one or more businesses or assets. The Investor further acknowledges that, as described in ArcLight’s prospectus relating to its initial public
offering dated March 22, 2021 (the “Prospectus”) available at www.sec.gov, substantially all of ArcLight’s assets consist of the cash proceeds of ArcLight’s initial public offering and private placement of its
securities, and substantially all of those proceeds have been deposited in a trust account (the “Trust Account”) for the benefit of ArcLight, its public shareholders and the underwriters of ArcLight’s initial public offering.
Except with respect to interest earned on the funds held in the Trust Account that may be released to ArcLight to pay its tax obligations, if any, the cash in the Trust Account may be disbursed only for the purposes set forth in the Prospectus. For
and in consideration of ArcLight entering into this Subscription Agreement, the receipt and sufficiency of which are hereby acknowledged, the Investor hereby irrevocably waives any and all right, title and interest, or any claim of any kind it has
or may have in the future, in or to any monies held in the Trust Account, and agrees not to seek recourse against the Trust Account as a result of, or arising out of, this Subscription Agreement; provided, however, that nothing in this
Section 9 shall be deemed to limit the Investor’s right, title, interest or claim to any monies held in the Trust Account by virtue of its record or beneficial ownership of any equity interests in ArcLight other than the Shares purchased
by it pursuant to this Subscription Agreement, pursuant to a validly exercised redemption right with respect to any such Class A ordinary shares, except to the extent that the Investor has otherwise agreed with ArcLight to not exercise such
redemption right. 
 10. [Reserved]. 

11. Miscellaneous. 
 a.
Neither this Subscription Agreement nor any rights that may accrue to the parties hereunder (other than the Shares acquired hereunder, if any) may be transferred or assigned without the prior written consent of the other party hereto;
provided that (i) this Subscription Agreement and any of the Investor’s rights and obligations hereunder may be assigned by the Investor to (A) any fund or account managed by the same investment manager as the Investor or by an
affiliate (as defined in Rule 12b-2 of the Exchange Act) of such investment manager or (B) one 

  
 14 

 
or more of the Investor’s affiliates, without the prior consent of ArcLight, prior to receipt of the Closing Notice, and (ii) the Investor’s rights under Section 7 may be
assigned to an assignee or transferee of the Shares; provided further that prior to such assignment any such assignee shall agree in writing to be bound by the terms hereof; provided, that no assignment pursuant to clause (i) of this
Section 11 shall relieve the Investor of its obligations hereunder. 
 b. ArcLight may request from the Investor such additional
information as ArcLight may deem necessary to register the resale of the Shares and evaluate the eligibility of the Investor to acquire the Shares, and the Investor shall promptly provide such information as may reasonably be requested, to the
extent readily available and to the extent consistent with the Investor’s internal policies and procedures; provided that ArcLight agrees to keep any such information provided by the Investor confidential except (i) as necessary to
include in any registration statement ArcLight is required to file hereunder, (ii) as required by the federal securities law or pursuant to other routine proceedings of regulatory authorities, or (iii) to the extent such disclosure is
required by law, at the request of the staff of the SEC or regulatory agency or under the regulations of any national securities exchange on which ArcLight’s securities are listed for trading. The Investor acknowledges that ArcLight may file a
copy of this Subscription Agreement that does not identify the Investor with the SEC as an exhibit to a periodic report or a registration statement of ArcLight. 

c. The Investor acknowledges that ArcLight, the Company, the Placement Agents and others will rely on the acknowledgments, understandings,
agreements, representations and warranties contained in this Subscription Agreement, including Schedule A hereto; provided, however, that the foregoing clause of this Section 11(c) shall not give ArcLight or the Placement Agents
any rights other than those expressly set forth herein. ArcLight acknowledges that the Investor, the Placement Agents and others will rely on the acknowledgments, understandings, agreements, representations and warranties contained in this
Subscription Agreement. Prior to the Closing, each party hereto agrees to promptly notify the other party hereto and the Placement Agents if any of the acknowledgments, understandings, agreements, representations and warranties of such party set
forth in Section 5 or Section 6 above, as applicable, are no longer accurate in any material respect (other than those acknowledgments, understandings, agreements, representations and warranties qualified by materiality, in which case such
party shall notify the other party hereto and the Placement Agents if they are no longer accurate in any respect). The Investor acknowledges and agrees that each purchase by the Investor of Shares from ArcLight will constitute a reaffirmation of the
acknowledgments, understandings, agreements, representations and warranties herein (as modified by any such notice) by the Investor as of the time of such purchase. 

d. ArcLight, the Investor, the Company and the Placement Agents are each entitled to rely upon this Subscription Agreement. Each of ArcLight,
the Company, the Placement Agents, and the Investor is irrevocably authorized to produce this Subscription Agreement or a copy hereof to any interested party in any administrative or legal proceeding or official inquiry with respect to the matters
covered hereby. Notwithstanding the foregoing, this clause (d) shall not give the Company or the Placement Agents any rights other than those expressly set forth herein and, without limiting the generality of the foregoing and for the avoidance
of doubt, in no event shall the Company be entitled to rely on any of the representations and warranties of ArcLight set forth in this Subscription Agreement. 

e. All of the agreements, representations and warranties made by each party hereto in this Subscription Agreement shall survive the Closing.

 f. This Subscription Agreement may not be modified, waived or terminated (other than pursuant to the terms of Section 8 above) except
by an instrument in writing, signed by each of the parties hereto, provided, however, that no modification or waiver by ArcLight of the provisions of this Subscription Agreement shall be effective without the prior written consent of
the Company (other than modifications or waivers that are solely ministerial in nature or otherwise immaterial and do not affect any economic or any other material term of this Subscription Agreement, provided that ArcLight provide the
Company with prior written notice thereof). No failure or delay of either party in exercising any right or remedy hereunder shall operate as a waiver thereof, nor shall any single or partial exercise of any such right or power, or any abandonment or
discontinuance of steps to enforce such right or power, or any course of conduct, preclude any other or further exercise thereof or the exercise of any other right or power. The rights and remedies of the parties hereunder are cumulative and are not
exclusive of any rights or remedies that they would otherwise have hereunder. 

  
 15 

 g. This Subscription Agreement (including the schedule hereto) constitutes the entire
agreement, and supersedes all other prior agreements, understandings, representations and warranties, both written and oral, among the parties, with respect to the subject matter hereof. Except as set forth in Section 7, Section 11(c),
Section 11(d), this Section 11(g) and the last sentence of Section 11(l) with respect to the persons specifically referenced therein, this Subscription Agreement shall not confer any rights or remedies upon any person other than the
parties hereto, and their respective successor and assigns, and the parties hereto acknowledge that such persons so referenced are third party beneficiaries of this Subscription Agreement for the purposes of, and to the extent of, the rights granted
to them, if any, pursuant to the applicable provisions. 
 h. Except as otherwise provided herein, this Subscription Agreement shall be
binding upon, and inure to the benefit of the parties hereto and their heirs, executors, administrators, successors, legal representatives, and permitted assigns, and the agreements, representations, warranties, covenants and acknowledgments
contained herein shall be deemed to be made by, and be binding upon, such heirs, executors, administrators, successors, legal representatives and permitted assigns. 

i. If any provision of this Subscription Agreement shall be adjudicated by a court of competent jurisdiction to be invalid, illegal or
unenforceable, the validity, legality or enforceability of the remaining provisions of this Subscription Agreement shall not in any way be affected or impaired thereby and shall continue in full force and effect. 

j. This Subscription Agreement may be executed in one or more counterparts (including by facsimile or electronic mail or in .pdf) and by
different parties in separate counterparts, with the same effect as if all parties hereto had signed the same document. All counterparts so executed and delivered shall be construed together and shall constitute one and the same agreement. 

k. Notwithstanding anything in this Subscription Agreement to the contrary, ArcLight shall not publicly disclose the name of the Investor, its
investment advisor or any of their respective affiliates or advisers, or include the name of the Investor, its investment advisor or any of their respective affiliates or advisers in any press release or in any filing with the SEC or any regulatory
agency or trading market, without the prior written consent of the Investor, except (i) as required by the federal securities law or pursuant to other routine proceedings of regulatory authorities or (ii) to the extent such disclosure is
required by law, at the request of the staff of the SEC or regulatory agency or under the regulations of any national securities exchange on which ArcLight’s securities are listed for trading; provided, however, that ArcLight
shall provide to the Investor a copy of any proposed disclosure under this Section 11(k) relating to the Investor in advance of any publication thereof and shall include such revisions to such proposed disclosure as the Investor shall
reasonably request. 
 l. The parties hereto acknowledge and agree that irreparable damage would occur in the event that any of the
provisions of this Subscription Agreement were not performed in accordance with their specific terms or were otherwise breached. It is accordingly agreed that the parties shall be entitled to an injunction or injunctions to prevent breaches of this
Subscription Agreement, without posting a bond or undertaking and without proof of damages, to enforce specifically the terms and provisions of this Subscription Agreement, this being in addition to any other remedy to which such party is entitled
at law, in equity, in contract, in tort or otherwise. The parties hereto acknowledge and agree that the Company and the Placement Agents shall be entitled to rely on the provisions of the Subscription Agreement of which the Company and the Placement
Agents are each an express third party beneficiary, in each case, on the terms and subject to the conditions set forth herein. 
 m. If any
change in the number, type or classes of authorized shares of ArcLight (including the Shares), other than as contemplated by the Business Combination Agreement or any agreement contemplated by the Business Combination Agreement, shall occur between
the date hereof and immediately prior to the Closing by reason of reclassification, recapitalization, stock split (including reverse stock split) or combination, exchange or readjustment of shares, or any stock dividend, the number of Shares issued
to the Investor shall be appropriately adjusted to reflect such change. 
 n. This Subscription Agreement shall be governed by and construed
in accordance with the laws of the State of New York (regardless of the laws that might otherwise govern under applicable principles of conflicts of laws thereof) as to all matters (including any action, suit, litigation, arbitration, mediation,
claim, charge, complaint, inquiry, proceeding, hearing, audit, investigation or reviews by or before any governmental entity related hereto), including matters of validity, construction, effect, performance and remedies. 

  
 16 

 o. No failure or delay by a party hereto in exercising any right, power or remedy under this
Subscription Agreement, and no course of dealing between the parties hereto, shall operate as a waiver of any such right, power or remedy of such party. No single or partial exercise of any right, power or remedy under this Subscription Agreement by
a party hereto, nor any abandonment or discontinuance of steps to enforce any such right, power or remedy, shall preclude such party from any other or further exercise thereof or the exercise of any other right, power or remedy hereunder. The
election of any remedy by a party hereto shall not constitute a waiver of the right of such party to pursue other available remedies. No notice to or demand on a party not expressly required under this Subscription Agreement shall entitle the party
receiving such notice or demand to any other or further notice or demand in similar or other circumstances or constitute a waiver of the rights of the party giving such notice or demand to any other or further action in any circumstances without
such notice or demand. 
 p. THE PARTIES HERETO IRREVOCABLY SUBMIT TO THE EXCLUSIVE JURISDICTION OF THE UNITED STATES DISTRICT COURT FOR THE
SOUTHERN DISTRICT OF NEW YORK AND THE SUPREME COURT OF THE STATE OF NEW YORK SOLELY IN RESPECT OF THE INTERPRETATION AND ENFORCEMENT OF THE PROVISIONS OF THIS SUBSCRIPTION AGREEMENT AND THE DOCUMENTS REFERRED TO IN THIS SUBSCRIPTION AGREEMENT AND IN
RESPECT OF THE TRANSACTIONS CONTEMPLATED HEREBY, AND HEREBY WAIVE, AND AGREE NOT TO ASSERT, AS A DEFENSE IN ANY ACTION, SUIT OR PROCEEDING FOR INTERPRETATION OR ENFORCEMENT HEREOF OR ANY SUCH DOCUMENT THAT IS NOT SUBJECT THERETO OR THAT SUCH ACTION,
SUIT OR PROCEEDING MAY NOT BE BROUGHT OR IS NOT MAINTAINABLE IN SAID COURTS OR THAT VENUE THEREOF MAY NOT BE APPROPRIATE OR THAT THIS SUBSCRIPTION AGREEMENT OR ANY SUCH DOCUMENT MAY NOT BE ENFORCED IN OR BY SUCH COURTS, AND THE PARTIES HERETO
IRREVOCABLY AGREE THAT ALL CLAIMS WITH RESPECT TO SUCH ACTION, SUIT OR PROCEEDING SHALL BE HEARD AND DETERMINED BY SUCH A NEW YORK STATE OR FEDERAL COURT. THE PARTIES HEREBY CONSENT TO AND GRANT ANY SUCH COURT JURISDICTION OVER THE PERSON OF SUCH
PARTIES AND OVER THE SUBJECT MATTER OF SUCH DISPUTE AND AGREE THAT MAILING OF PROCESS OR OTHER PAPERS IN CONNECTION WITH SUCH ACTION, SUIT OR PROCEEDING IN THE MANNER PROVIDED IN THIS SECTION 11(p) OF THIS SUBSCRIPTION AGREEMENT OR IN SUCH OTHER
MANNER AS MAY BE PERMITTED BY LAW SHALL BE VALID AND SUFFICIENT SERVICE THEREOF. 
 q. EACH PARTY ACKNOWLEDGES AND AGREES THAT ANY
CONTROVERSY WHICH MAY ARISE UNDER THIS SUBSCRIPTION AGREEMENT OR THE TRANSACTIONS CONTEMPLATED HEREBY IS LIKELY TO INVOLVE COMPLICATED AND DIFFICULT ISSUES, AND THEREFORE EACH SUCH PARTY HEREBY IRREVOCABLY AND UNCONDITIONALLY WAIVES ANY RIGHT SUCH
PARTY MAY HAVE TO A TRIAL BY JURY IN RESPECT OF ANY LITIGATION DIRECTLY OR INDIRECTLY ARISING OUT OF OR RELATING TO THIS SUBSCRIPTION AGREEMENT OR THE TRANSACTIONS CONTEMPLATED BY THIS SUBSCRIPTION AGREEMENT. EACH PARTY CERTIFIES AND ACKNOWLEDGES
THAT (I) NO REPRESENTATIVE, AGENT OR ATTORNEY OF ANY OTHER PARTY HAS REPRESENTED, EXPRESSLY OR OTHERWISE, THAT SUCH OTHER PARTY WOULD NOT, IN THE EVENT OF LITIGATION, SEEK TO ENFORCE THE FOREGOING WAIVER; (II) SUCH PARTY UNDERSTANDS AND
HAS CONSIDERED THE IMPLICATIONS OF THE FOREGOING WAIVER; (III) SUCH PARTY MAKES THE FOREGOING WAIVER VOLUNTARILY AND (IV) SUCH PARTY HAS BEEN INDUCED TO ENTER INTO THIS SUBSCRIPTION AGREEMENT BY, AMONG OTHER THINGS, THE MUTUAL WAIVER AND
CERTIFICATIONS IN THIS SECTION 11(q). 
 12. Non-Reliance and Exculpation. The Investor
acknowledges that it is not relying upon, and has not relied upon, any statement, representation or warranty made by any person, firm or corporation (including, without limitation, the Placement Agents, the Company or any of their respective
affiliates or any control persons, officers, directors, employees, partners, agents or representatives of any of the foregoing), other than the statements, representations and warranties of ArcLight expressly contained in Section 5 of this
Subscription Agreement, in making its investment or decision to invest in ArcLight. The Investor acknowledges and agrees that, other than the statements, representations and warranties of ArcLight expressly contained in Section 5 of this
Subscription Agreement, none of (i) any other investor pursuant to this Subscription Agreement or any other subscription agreement related to the 

  
 17 

 
private placement of the Shares (including the investor’s respective affiliates or any control persons, officers, directors, employees, partners, agents or representatives of any of the
foregoing), (ii) the Placement Agents, their affiliates or any control persons, officers, directors, employees, partners, agents or representatives of any of the foregoing, or (iii) any other party to the Business Combination Agreement (other
than ArcLight) or any Non-Party Affiliate, shall have any liability to the Investor, or to any other investor, pursuant to, arising out of or relating to this Subscription Agreement or any other subscription
agreement related to the private placement of the Shares, the negotiation hereof or thereof or its subject matter, or the transactions contemplated hereby or thereby, including, without limitation, with respect to any action heretofore or hereafter
taken or omitted to be taken by any of them in connection with the purchase of the Shares or with respect to any claim (whether in tort, contract or otherwise) for breach of this Subscription Agreement or in respect of any written or oral
representations made or alleged to be made in connection herewith, as expressly provided herein, or for any actual or alleged inaccuracies, misstatements or omissions with respect to any information or materials of any kind furnished by ArcLight,
the Company, the Placement Agents or any Non-Party Affiliate concerning ArcLight, the Company, the Placement Agents, any of their controlled affiliates, this Subscription Agreement or the transactions
contemplated hereby. For purposes of this Subscription Agreement, “Non-Party Affiliates” means each former, current or future officer, director, employee, partner, member, manager, direct or indirect
equityholder or affiliate of ArcLight, the Company, the Placement Agents or any of ArcLight’s, the Company’s or the Placement Agents’ controlled affiliates or any family member of the foregoing. 

13. Disclosure. ArcLight shall, by 9:00 a.m., New York City time, on the first (1st) Business Day immediately following the date of this
Subscription Agreement, issue one or more press releases or file with the SEC a Current Report on Form 8-K (collectively, the “Disclosure Document”) disclosing all material terms of the
transactions contemplated hereby and by the Other Subscription Agreements, the Transaction and any other material, nonpublic information that ArcLight or any of its representatives has provided to the Investor at any time prior to the filing
of the Disclosure Document. Upon the issuance of the Disclosure Document, to the actual knowledge of ArcLight, the Investor shall not be in possession of any material, non-public information received from
ArcLight or any of its officers, directors, or employees or agents. 
 14. Several Obligations. The obligations of the Investor under
this Subscription Agreement are several and not joint with the obligations of any other investor under the Other Subscription Agreements, and the Investor shall not be responsible in any way for the performance of the obligations of any other
investor under any Other Subscription Agreement. The decision of the Investor to purchase the Shares pursuant to this Subscription Agreement has been made by the Investor independently of any other investor and independently of any information,
materials, statements opinions as to the business, affairs, operations, assets, properties, liabilities, results of operations, condition (financial or otherwise) or prospects of ArcLight, the Company or any of their respective subsidiaries which
may have been made or given by any other investor or by any agent or employee of any other investor, and neither the Investor nor any of its agents or employees shall have any liability to any other investor relating to or arising from any such
information, materials, statements or opinions. Nothing contained herein or in any Other Subscription Agreement, and no action taken by the Investor or any other investor pursuant hereto or thereto, shall be deemed to constitute the Investor and any
other investor as a partnership, an association, a joint venture or any other kind of entity, or create a presumption that the Investor and any other investor are in any way acting in concert or as a “group” (within the meaning of
Section 13(d) of the Exchange Act) with respect to such obligations or the transactions contemplated by this Subscription Agreement and the Other Subscription Agreements. The Investor acknowledges that no other investor has acted as agent for
the Investor in connection with making its investment hereunder and no other investor will be acting as agent of the Investor in connection with monitoring its investment in the Shares or enforcing its rights under this Subscription Agreement. 

15. Notices. Unless otherwise provided herein, any notice or communication required or permitted hereunder shall be in writing and
either delivered personally, emailed or telecopied, sent by overnight mail via a reputable overnight carrier, or sent by certified or registered mail, postage prepaid, and shall be deemed to be given and received (a) when so delivered
personally, (b) upon receipt of an appropriate electronic answerback or confirmation when so delivered by telecopy (to such number specified below or another number or numbers as such person may subsequently designate by notice given
hereunder), (c) when sent, with no mail undeliverable or other rejection notice, if sent by email, or (d) five (5) business days after the date of mailing to the address below or to such other address or addresses as such person may hereafter
designate by notice given hereunder to the address or addresses set forth on the signature pages hereto. 
 [SIGNATURE PAGES FOLLOW]

  
 18 

 IN WITNESS WHEREOF, the Investor has executed or caused this Subscription Agreement
to be executed by its duly authorized representative as of the date set forth below. 
  

			
	Name of Investor:	  	State/Country of Formation or Domicile:
		
	By:                                     
                             	  	
	Name:                                     
                        	  	
	Title:                                     
                          	  	
		
	Name in which Shares are to be registered (if different):	  	Date: ________, 2021
		
	Investor’s EIN:	  	
		
	Business Address-Street:	  	Mailing Address-Street (if different):
		
	City, State, Zip:	  	City, State, Zip:
		
	Attn:                                     
                       	  	Attn:                                     
                       
		
	Telephone No.:	  	Telephone No.:
	Facsimile No.:	  	Facsimile No.:
		
	Email address for Closing Notice:	  	
		
	Number of Shares subscribed for:	  	
		
	Aggregate Subscription Amount: $	  	Price Per Share: $10.00

 You must pay the Subscription Amount by wire transfer of United States dollars in immediately available funds
to the account specified by ArcLight in the Closing Notice. 
  

  
 [Signature Page to
Subscription Agreement] 

 IN WITNESS WHEREOF, ArcLight has accepted this Subscription Agreement as of the date set
forth below. 
  

			
	ARCLIGHT CLEAN TRANSITION CORP. II
		
	By:	 	  

	Name:	 	
	Title:	 	

 Date: [•], 2021 
  

  
 [Signature Page to
Subscription Agreement] 

 SCHEDULE A 

ELIGIBILITY REPRESENTATIONS OF THE INVESTOR 
  

			
	 A. QUALIFIED INSTITUTIONAL BUYER STATUS

	
	 (Please check if applicable):

 ☐ The Investor is a “qualified institutional buyer” (as defined in Rule 144A under the
Securities Act (a “QIB”)). 
  

			
	 B. INSTITUTIONAL ACCREDITED INVESTOR STATUS

	
	 (Please check the applicable subparagraphs, to the extent applicable):

  

			
	 1.  ☐ The Investor is an “accredited investor” (within the
meaning of Rule 501(a) under the Securities Act or an entity in which all of the equity holders are accredited investors within the meaning of Rule 501(a) under the Securities Act), and has marked and initialed the appropriate box below indicating
the provision under which the Investor qualifies as an “accredited investor.”

  

	
	 2.  ☐ The Investor is not a natural person.

 Rule 501(a), in relevant part, states that an “accredited investor” shall mean any person who comes within any of
the below listed categories, or who the issuer reasonably believes comes within any of the below listed categories, at the time of the sale of the securities to that person. The Investor has indicated, by marking and initialing the appropriate box
below, the provision(s) below which apply to the Investor and under which the Investor accordingly qualifies as an “accredited investor.” 

☐ Any bank, registered broker or dealer, insurance company, registered investment company, business development company, or small
business investment company; 
 ☐ Any plan established and maintained by a state, its political subdivisions, or any agency or
instrumentality of a state or its political subdivisions for the benefit of its employees, if such plan has total assets in excess of $5,000,000; 

☐ Any employee benefit plan, within the meaning of the Employee Retirement Income Security Act of 1974, if a bank, insurance company, or
registered investment adviser makes the investment decisions, or if the plan has total assets in excess of $5,000,000; 
 ☐ Any
organization described in Section 501(c)(3) of the Internal Revenue Code, corporation, Massachusetts or similar business trust, or partnership, not formed for the specific purpose of acquiring the securities offered, with total assets in excess
of $5,000,000; 
 ☐ Any trust with assets in excess of $5,000,000, not formed to acquire the securities offered, whose purchase is
directed by a sophisticated person; or 
 ☐ Any entity in which all of the equity owners are accredited investors meeting one or more
of the above tests. 
 This page should be completed by the Investor 

and constitutes a part of the Subscription Agreement. 

  
 [Schedule A to
Subscription Agreement]

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