Comparison of the indoor performance of 12 commercial PV products by a simple model

The term productintegrated photovoltaic (PIPV) [1, 2] is used for all types of products that contain solar cells in one or more of their surfaces, aiming at providing power during the use of a product. The application of photovoltaics (PV) as a power source for consumer products is already common for more than 30 years, since the first solar calculators. Thereafter, integrated solar cells in consumer products became more popular and at present PV cells are applied in both indoor and outdoor applications, for example, lanterns, chargers, speakers, bike lights, solar watches, etc. A product can be defined as a PIPV product mainly by the existence of integrated PV cell(s) on at least one of its surfaces and the internal use of energy, which is generated by the PV cell(s) [1] (see Fig. 1, example of PIPV). Figure 2A depicts the basic power system of a PVpowered product. Basic elements are solar cell, an energy storage device (i.e., a capacitor or battery), and a diode to prevent discharging of the battery through the solar panel. Matching of the battery voltage with the solar cell is done by creating a small solar panel with the right number of solar cells in series for an appropriate voltage. RESEARCH ARTICLE