This is just an idea i had today.
Render to make it look like a mexican(spanish) wall (or look good). E.G:
Inside the wall run water pipes (copper or plastic). In summer the wall will heat up and keep the heat inside the wall, the pipes will let the water go through and heat up. (Recycled water or rain water) and colelct in a boiler of sorts.
Attached to this boiler tank would be a Heat differential motor or stirling engine/motor. like:
This could then turn a compressor (and the water pump) like a normal aircon would, but i would guess its capacity would depend on the power of the stirling motor. And could turn the summer heat into a nice cool breeze. In winter you could use the heat from the wall to heat up your house.
Just an idea that could be investigated i guess.