Exhibit 23.1

Consent of Independent Registered Public Accounting Firm 

We hereby consent to the use in the Prospectus constituting a part of this Registration Statement on Amendment No. 2 to Form S-1 of our report dated June 24, 2021, relating to the financial statements of CleanTech Acquisition Corp., which is  contained  in that Prospectus. We also consent to the reference to us under the caption “Experts” in the Prospectus.

/s/ WithumSmith+Brown, PC