Two Questions:
1) Do train stations(Barcelona and Madrid) have lockers to rent to store luggage?
2) My son has spent the semester in Barcelona and has more luggage than we want to travel with for 2 weeks. Is there an easy/inexpensive way to send luggage to the Lisbon Airport from Barcelona?
1) Yes, at Barcelona Sants station and at both Chamartin and P. Atocha stations in Madrid, 10 euros/day. Also consider private companies like www.lockerbarcelona.com.
2) No.
2.) Kind of yes (sorry Laura!)... https://www.seur.com/en/ Cost for 20kg should be under 30€, which is not that inexpensive but it isn't that expensive either. Something else is "who's going to receive the luggage in Lisbon?" as packages are sent to someone somewhere, not to a generic "Lisbon airport".
No problem, Enric. If it exists, then I'm happy to learn that.