9. Stockholders’ Equity

Shares issued

During the three months ended March 31, 2021, the Company issued 543,040 shares of common stock upon vesting of Restricted Stock Units ("RSUs") granted by the Company.

During the three months ended March 31, 2021, the Company issued, when the five-day average of closing prices for the Company’s common stock was $3.95 per share, 5,371 shares of the Company’s common stock pursuant to a cashless exercise of a warrant for 10,350 shares of the Company’s common stock with an exercise price of $1.90 per share.

During the three months ended March 31, 2021, the Company issued, when the five-day average of closing prices for the Company’s common stock was $6.20 per share, 60,219 shares of the Company’s common stock pursuant to a cashless exercise of a warrant for 86,778 shares of the Company’s common stock with an exercise price of $1.90 per share.

During the three months ended March 31, 2021, the Company issued 41,209 shares of common stock upon vesting of RSUs granted to Board members.

During the three months ended March 31, 2021, the Company issued 375,000 shares of common stock pursuant to the Series A Preferred Stock Purchase Agreement dated February 15, 2021.

During the three months ended March 31, 2021, the Company issued 345,818 shares of common stock upon stock option exercises.

During the three months ended March 31, 2021, the Company issued 1,923,614 shares of common stock pursuant to the At The Market Issuance Sales Agreement for net proceeds of $7.5 million.

Stock-based compensation

The stock-based compensation expense was allocated as follows:

There were no options issued during the three months ended March 31, 2021 or the three months ended March 31, 2020.

Restricted stock units

In February 2021, the Company granted 25,000 RSUs, all of which were subject to vesting, with a grant fair value of $151,500 to a contractor. The shares vest in three tranches 1) upon the signing of a licensing agreement 2) delivery of a final engineering package, and 3) full handover of project to site owner. No shares vested during the three months ended March 31, 2021.