All perfect praise be to Allaah, The Lord of the Worlds. I testify that there is none worthy of worship except Allaah, and that Muhammad is His slave and Messenger. We ask Allaah to exalt his mention as well as that of his family and all his companions.
Yes, it is valid to perform ablution when not covering the 'Awrah (parts of the body that must be covered in Islam). So ablution is not void if one performs it while in a state of not covering his 'Awrah. However, many scholars are of the view that it is forbidden to show one's 'Awrah without a need when being alone.
For more benefit, please refer to Fatwa: 84093 on the nullifiers of ablution.
Allaah knows best.