*5.1.5 Photovoltaic panels*

Solar panels are easy to purchase and install. The price is getting lower, so they are a good choice for collecting energy from the environment. Since the panels provide a DC output, they can be plugged directly into the electronics' power system. The output power can be from mW to MW depending on the size of the panels as well as the intensity of the light they receive. However, the main limitation is that they need to be exposed to sunlight, so they can only work during the day. Batteries and/or supercapacitors are necessary for power supply at night. Energy storage is also necessary for cloudy or snowy days [40].
