This is the 2002nd most frequent Catalan word.
solar
A plot of land for building.
In this sentence, 'solar' is an adjective describing the panel, indicating it uses sunlight for operation.
El panell solar genera energia neta.
The solar panel generates clean energy.
Here, 'solar' functions as a noun indicating a piece of land.
Van comprar un solar per construir una casa.
They bought a plot of land to build a house.
'Solar' is again used as an adjective modifying 'radiació', referring to radiation from the sun.