Whilst I know that the procedures can vary from region to region I would be very surprised if any region introduces an online renewal system as they need to verify your ID etc.
Without being pedantic - the card no longer exists (and hasn’t for nearly 2 years) it was replaced by a Certificado de Registro which you need to apply for after 3 months of permanent living in Spain. The link above I think is for NON EU persons (form EX 00)
There is an application from which varies depending upon your personal circumstances (ie EU, non EU) for EU persons it is the EX-16 obtained online from:
RESIDENCIA (EX16)
Application Forms and the
Regulations Governing EU citizens in Spain document.
http://extranjeros.mtas.es/
For forms - Click: Modelos de Solictudes