Respuesta :
The correct answer is: A supplemental heating unit for cloudy days, winters, and nighttime.
Answer:
A supplemental heating unit for cloudy days, winters, and night times
Explanation:
Solar energy is the energy obtained from Sun and is the renewable eco-friendly source of energy. It relies on availability of Sun in sky so as to use it for energy production. Since solar energy is not available at night time, there is a need of supplemental heating unit. Similarly, amount of solar energy fluctuates during cloudy days and winters which in turn poses the need for supplemental heating unit.