solar panel 
noun
A panel designed to absorb the sun’s rays as a source of energy for generating electricity or heating.The cleanest energy sources of electricity are solar panels and wind turbines, which are only starting to be used in Canada....
- Most robots today draw that energy from electrical cords, solar panels, or batteries.
- Unlike other renewable power sources, solar panels provide the most electricity in the middle of the day, when it is needed most.
- between the devil and the deep blue sea
- between you and me and the bedpost (or the gatepost or the wall)
- between you and me and the gatepost
- between you and me and the wall
- be twice the man/woman (that someone is)
- betwixt
- betwixt and between
- be two a penny
- be two (or ten) a penny
- beun
- be unable to believe one's eyes (or ears)
- be unable to hear oneself think
- be unable to (or be hardly able to) believe one's luck
- be unable to punch one's way out of a paper bag
- be unable to see the wood (or the forest) for the trees
- be under no illusion (or illusions)
- be under the illusion that
- be up shit creek
- be up shit creek (also be up shit creek without a paddle)
- be up the creek
- be up with the lark
- beurre blanc
- beurre manié
- beurre noir
- beurre noisette