Exhibit
10.55


 


PROMISSORY
NOTE


 


	Principal	Loan
    Date	Maturity	Loan
    No	Call/Coll	Account	Officer	Initials
	$1,000,000.00	09-15-2021	On
    Demand	11001	402
    / 326	N9015196621	JXD9P	 
	References
    in the boxes above are for Lender’s use only and do not limit the applicability of this document to any particular loan
    or item Any item above containing “**” has been omitted due to text length limitations.


 


	Borrower:	Mechanical
Technology, Incorporated
 325 Washington Avenue
Ext. Suite 3
 Albany, NY  12205-5535

                                                               

                                                               
	 	Lender:	KeyBank
    National Association

    NY62224F NY-KEY PLAZA CBB

    66 S. Pearl Street

    Albany, NY  12207
	 	 	 	 	 
	Principal Amount: $1,000,000.00	 	 	Date of Note: September
    15, 2021         



  


PROMISE
TO PAY. To repay Borrower’s loan, Mechanical Technology, Incorporated (“Borrower”) promises to pay to KeyBank
National Association (“Lender”), or order, in lawful money of the United States of America, on demand, the principal
amount of One Million & 00/100 Dollars (S1,000,000.00) or so much as may be outstanding, together with interest on the unpaid
outstanding principal balance of each advance. Interest shall be calculated from the date of each advance until repayment of each
advance.


 


PAYMENT.
Borrower will pay this loan in full immediately upon Lender’s demand. Borrower will pay regular monthly payments of all
accrued unpaid interest due as of each payment date, beginning October 1, 2021, with all subsequent interest payments to be due
on the same day of each month after that. Unless otherwise agreed or required by applicable law, payments will be applied to first
pay interest accrued to the day Lender receives the payment, then to bring principal current, then to pay any late fees, and then
Lender will apply any remaining balance to reduce principal. Borrower will pay Lender at Lender’s address shown above or
at such other place as Lender may designate in writing.


 


VARIABLE
INTEREST RATE. The interest rate on this Note is subject to change from time to time based on changes in an index which is
the Prime Rate announced by Lender (the “Index”). The Index is not necessarily the lowest rate charged by Lender on
its loans and is set by Lender in its sole discretion. Lender will tell Borrower the current Index rate upon Borrower’s
request. The interest rate change will not occur more often than each day that the Index changes. The interest rate will change
automatically and correspondingly on the date of each announced change of the Index by Lender. Borrower understands that Lender
may make loans based on other rates as well. The Index currently is 3.250% per annum. Interest on the unpaid principal balance
of this Note will be calculated as described in the “INTEREST CALCULATION METHOD” paragraph using a rate of 0.750
percentage points over the Index (the “Margin”), adjusted if necessary for any minimum and maximum rate limitations
described below, resulting in an initial rate of 4.000% per annum based on a year of 360 days. If Lender determines, in its sole
discretion, that the Index has become unavailable or unreliable, either temporarily, indefinitely, or permanently, during the
term of this Note, Lender may amend this Note by designating a substantially similar substitute index. Lender may also amend and
adjust the Margin to accompany the substitute index. The change to the Margin may be a positive or negative value, or zero. In
making these amendments, Lender may take into consideration any then-prevailing market convention for selecting a substitute index
and margin for the specific Index that is unavailable or unreliable. Such an amendment to the terms of this Note will become effective
and bind Borrower 10 business days after Lender gives written notice to Borrower without any action or consent of the Borrower.
NOTICE: Under no circumstances will the interest rate on this Note be less than 3.000% per annum or more than the maximum rate
allowed by applicable law.


 






    


     

    

 





	PROMISSORY
    NOTE
	(Continued)
	Loan No.
    11001	Page
    2




 


INTEREST
CALCULATION METHOD. Interest on this Note is computed on a 365/360 basis; that is, by applying the ratio of the interest rate
over a year of 360 days, multiplied by the outstanding principal balance, multiplied by the actual number of days the principal
balance is outstanding. All interest payable under this Note is computed using this method.


 


PREPAYMENT.
Borrower agrees that all loan fees and other prepaid finance charges are earned fully as of the date of the loan and will not
be subject to refund upon early payment (whether voluntary or as a result of default), except as otherwise required by law. Except
for the foregoing, Borrower may pay without penalty all or a portion of the amount owed earlier than it is due. Early payments
will not, unless agreed to by Lender in writing, relieve Borrower of Borrower’s obligation to continue to make payments
of accrued unpaid interest. Rather, early payments will reduce the principal balance due. Borrower agrees not to send Lender payments
marked “paid in full”, “without recourse”, or similar language. If Borrower sends such a payment, Lender
may accept it without losing any of Lender’s rights under this Note, and Borrower will remain obligated to pay any further
amount owed to Lender. All written communications concerning disputed amounts, including any check or other payment instrument
that indicates that the payment constitutes “payment in full” of the amount owed or that is tendered with other conditions
or limitations or as full satisfaction of a disputed amount must be mailed or delivered to: KeyBank National Association, NY62224F
NY-KEY PLAZA CBB, 66 S. Pearl Street, Albany, NY 12207.


 


LATE
CHARGE. If a regularly scheduled interest payment is 10 days or more late, Borrower will be charged 5.000% of the unpaid portion
of the regularly scheduled payment or $25.00, whichever is greater. If Lender demands payment of this loan, and Borrower does
not pay the loan in full within 10 days after Lender’s demand, Borrower also will be charged either 5.000% of the unpaid
portion of the sum of the unpaid principal plus accrued unpaid interest or $25.00, whichever is greater.


 


INTEREST
AFTER DEFAULT. Upon default, including failure to pay upon final maturity, the interest rate on this Note shall be increased
by adding an additional 3.000 percentage point margin (“Default Rate Margin”). The Default Rate Margin shall also
apply to each succeeding interest rate change that would have applied had there been no default. However, in no event will the
interest rate exceed the maximum interest rate limitations under applicable law.


 






    


     

    

 





	PROMISSORY
    NOTE
	(Continued)
	Loan No.
    11001	Page
    3


 


LENDER’S
RIGHTS. Upon Lender’s demand, Lender may declare the entire unpaid principal balance under this Note and all accrued
unpaid interest immediately due, and then Borrower will pay that amount.


 


ATTORNEYS’
FEES; EXPENSES. Borrower agrees to pay all costs and expenses Lender incurs to collect this Note. This includes, subject to
any limits under applicable law, Lender’s reasonable attorneys’ fees and Lender’s legal expenses whether or
not there is a lawsuit, including reasonable attorneys’ fees and expenses for bankruptcy proceedings (including efforts
to modify or vacate any automatic stay or injunction), and appeals. If not prohibited by applicable law, Borrower also will pay
any court costs, in addition to all other sums provided by law.


 


JURY
WAIVER. Lender and Borrower hereby waive the right to any jury trial in any action, proceeding, or counterclaim brought by
either Lender or Borrower against the other.


 


GOVERNING
LAW. This Note will be governed by federal law applicable to Lender and, to the extent not preempted by federal law, the laws
of the State of New York without regard to its conflicts of law provisions. This Note has been accepted by Lender in the State
of New York.


 


DISHONORED
ITEM FEE. Borrower will pay a fee to Lender of $20.00 if Borrower makes a payment on Borrower’s loan and the check or
preauthorized charge with which Borrower pays is later dishonored.


 


RIGHT
OF SETOFF. To the extent permitted by applicable law, Lender reserves a right of setoff in all Borrower’s accounts with
Lender (whether checking, savings, or some other account and whether evidenced by a certificate of deposit). This includes all
accounts Borrower holds jointly with someone else and all accounts Borrower may open in the future. However, this does not include
any IRA or Keogh accounts, or any trust accounts for which setoff would be prohibited by law. Borrower authorizes Lender, to the
extent permitted by applicable law, to charge or setoff all sums owing on the indebtedness against any and all such accounts.


 


LINE
OF CREDIT. This Note evidences a revolving line of credit. Advances under this Note may be requested either orally or in writing
by Borrower or as provided in this paragraph. Lender may, but need not, require that all oral requests be confirmed in writing.
All communications, instructions, or directions by telephone or otherwise to Lender are to be directed to Lender’s office
shown above. Borrower agrees to be liable for all sums either: (A) advanced in accordance with the instructions of an authorized
person or (B) credited to any of Borrower’s accounts with Lender. The unpaid principal balance owing on this Note at any
time may be evidenced by endorsements on this Note or by Lender’s internal records, including daily computer print-outs.


 


ANNUAL
ADMINISTRATIVE FEE. Borrower will pay an annual administrative fee of $1,000.00 on the date of the Note and $1,000.00 on each
subsequent anniversary date of the Note. This fee does not constitute the commitment of Lender to make advances under the Note.


 






    


     

    

 





	PROMISSORY
    NOTE
	(Continued)
	Loan No.
    11001	Page
    4


 


DEMAND
LINE OF CREDIT. Borrower understands that Lender is authorized to make an annual (or more frequent) credit review based upon
Borrower’s current financial condition in determining whether to continue the line of credit. Nevertheless, Lender may,
at any time, with or without cause, refuse to advance funds or extend credit under the line of credit.


 


AUTHORIZATION
TO CHARGE DEPOSIT ACCOUNT FOR LOAN PAYMENTS. Borrower hereby authorizes Lender automatically to deduct from Borrower’s
designated deposit account (“Account”), payments due on the loan on the date each payment is due.


 


Borrower
authorizes Lender to deduct amounts subject to change without prior notification to Borrower of the new amount to be deducted
due to: (1) late charges assessed; (2) delinquent amounts due or (3) any other payment amount required under the terms of the
loan. If the funds in the Account are insufficient to cover any payment, Lender shall not be obligated to advance funds to cover
the payment. Lender shall not be liable for dishonoring checks or other items due to insufficient funds caused by the honoring
of this Authorization.


 


Borrower
may terminate this authorization by giving not less than three (3) days prior written notice to the Loan Services Department.
This authorization may be terminated at any time by Lender.


 


SUCCESSOR
INTERESTS. The terms of this Note shall be binding upon Borrower, and upon Borrower’s heirs, personal representatives,
successors and assigns, and shall inure to the benefit of Lender and its successors and assigns.


 


GENERAL
PROVISIONS. If any part of this Note cannot be enforced, this fact will not affect the rest of the Note. Lender may delay
or forgo enforcing any of its rights or remedies under this Note without losing them. Borrower and any other person who signs,
guarantees or endorses this Note, to the extent allowed by law, waive presentment, demand for payment, and notice of dishonor.
Upon any change in the terms of this Note, and unless otherwise expressly stated in writing, no party who signs this Note, whether
as maker, guarantor, accommodation maker or endorser, shall be released from liability. All such parties agree that Lender may
renew or extend (repeatedly and for any length of time) this loan or release any party or guarantor or collateral; or impair,
fail to realize upon or perfect Lender’s security interest in the collateral; and take any other action deemed necessary
by Lender without the consent of or notice to anyone. All such parties also agree that Lender may modify this loan without the
consent of or notice to anyone other than the party with whom the modification is made. The obligations under this Note are joint
and several.


 


PRIOR
TO SIGNING THIS NOTE, BORROWER READ AND UNDERSTOOD ALL THE PROVISIONS OF THIS NOTE, INCLUDING THE VARIABLE INTEREST RATE PROVISIONS.
BORROWER AGREES TO THE TERMS OF THE NOTE.


 






    


     

    

 





	PROMISSORY
    NOTE
	(Continued)
	Loan No.
    11001	Page
    5


 


BORROWER
ACKNOWLEDGES RECEIPT OF A COMPLETED COPY OF THIS PROMISSORY NOTE. 


 


BORROWER:


 


MECHANICAL
TECHNOLOGY, INCORPORATED


 





	By:	/s/ Jessica Thomas	 
	 	Jessica Thomas, CFO of Mechanical Technology,
    Incorporate