My local storage company does not have electricity available in their storage units. They agreed to allow me to install solar panels on their roof (using sand-bags to secure the base, instead of screws or bolts). This way, electricity is available to float charge the car battery. Perhaps something of this sort would be an option for you.
Storm titanium 2005 Elise with carbon fiber spoiler, BWR sway bar, BOE toe links, gPan2, LidBone, sector 111 wheel studs, Grey RAC Monolite wheels with toyo R1R, Team Dynamics 1.4 with Hoosier A6/R6s, Katana2 Supercharger, ECU with 265 flash. PPE headers w/decat, CEL angle eliminator, Silent touch catback, Rear Panel Eliminator, HKS intake, V2 fuel tank, Walbro255 fuel pump. HID lights.