Exhibit 24

                               POWER OF ATTORNEY

        The undersigned, as a Section 16 reporting person of ESS, Inc. (the
"Company"), hereby constitutes and appoints Eric P. Dresselhuys, Amir Moftakhar
and Jeff Bodner, and each of them, as the undersigned's true and lawful
attorney-in-fact to:

        1.  complete and execute Forms 3, 4 and 5 and other forms and all
            amendments thereto as such attorney-in-fact shall in his discretion
            determine to be required or advisable pursuant to Section 16 of the
            Securities Exchange Act of 1934 (as amended) and the rules and
            regulations promulgated thereunder, or any successor laws and
            regulations, as a consequence of the undersigned's ownership,
            acquisition or disposition of securities of the Company; and

        2.  do all acts necessary in order to file such forms with the SEC, any
            securities exchange or national association, the Company and such
            other person or agency as the attorneys-in-fact shall deem
            appropriate.

        The undersigned hereby ratifies and confirms all that said attorneys-in-
fact and agents shall do or cause to be done by virtue hereof.  The undersigned
acknowledges that the foregoing attorneys-in-fact, in serving in such capacity
at the request of the undersigned, are not assuming, nor is the Company
assuming, any of the undersigned's responsibilities to comply with Section 16 of
the Securities Exchange Act of 1934 (as amended).

        This Power of Attorney shall remain in full force and effect until the
undersigned is no longer required to file Forms 3, 4 and 5 with respect to the
undersigned's holdings of and transactions in securities issued by the Company,
unless earlier revoked by the undersigned in a signed writing delivered to the
Company and the foregoing attorneys-in-fact.

        IN WITNESS WHEREOF, the undersigned has caused this Power of Attorney to
be executed as of this 15th day of September, 2021.

                                        Signature: /s/ Eric P. Dresselhuys
                                                   -------------------------
                                        Print Name: Eric P. Dresselhuys