Answer and Explanation:
The literary technique that Shelley uses in the poem is the personification because it presents the wind as a human being with the ability to destroy and sow, to carry sadness and joy, that is, the west wind is positioned as something powerful, with human skills and that can be terrible and wonderful.
The speaker of the poem feels an affinity with the west wind, because while the wind is powerful and imposing, the speaker is weak, has no influence and is downcast and melancholy about himself. He wants to be like the wind and therefore establishes an affinity with him. This affinity allows the reader to ask the wind for a little power, because with this power he would write touching poetry and take it to the whole world, leaving him less melancholy.