This thesis explores the field of product-integrated photovoltaics (PIPV), a term which is used for all types of products that contain solar cells in one or more of their surfaces, aiming at providing power during the product’s use. Product-integrated photovoltaics (PIPV) began to be widely introduced around 2000, although the use of PV systems in products dates back to the 70s. PIPV includes products such as PV-powered boats, aircrafts, cars, bicycles, camping tents, street lights, recycling bins, decorative lights, PV-powered watches, calculators, PV-powered lamps, sensors, chargers, toys, low-powered kitchen appliances, entertainment appliances or PV-powered art objects. The incorporation of PV systems in products could offer various benefits, such as enhanced functionality of the product as a result of energy autonomy, and independence and freedom of use due to the absence of a connection to the electricity grid, as well as the opportunity to reduce the capacity of batteries in portable products and therefore making them more sustainable. Furthermore, photovoltaic products represent a very reliable solution for the supply of electricity in areas, which lack access to an electricity grid. This thesis is oriented towards the development of scientific and technological knowledge about product-integrated PV (PIPV), as it focuses on the aspects that designers need to take into consideration when designing PV products. This research is interdisciplinary by nature due to its embedding in the field of industrial design engineering, regarding the technological aspects of PV technologies in products and user interaction with PV products. It combines the technical knowledge of PV technologies, indoor irradiance conditions and performance of PV cells and PV products in environments with low irradiance together with the typical behavior of users with these products and the way this behavior influences the performance of the products themselves. Besides being directed towards researchers, results of this study are useful for industrial designers who are developing PV products. @en

This article presents a simple comparative model which has been developed for the estimation of the performance of photovoltaic (PV) products' cells in indoor environments. The model predicts the performance of PV solar cells, as a function of the distance from a spectrum of artificial (fluorescent light, halogen light, and light-emitting diodes) and natural light. It intends to support designers, while creating PV-integrated products for indoor use. For the model's validation, PV cells of 12 commercially available PV-powered products with power ranging from 0.8 to 4 mWp were tested indoors under artificial illumination and natural light. The model is based on the physical measurements of natural and artificial irradiance indoors, along with literature data of PV technologies under low irradiance conditions. The input data of the model are the surface of the solar cell (in m2), the wavelength-dependent spectral response (SR) of the PV cell, the spectral irradiance indoors, and solar cell's distance from light sources. The model calculates solar cells' efficiency and power produced under the specific indoor conditions. If using the measured SR of a PV cell and the irradiance as measured indoors, the model can predict the performance of a PV product under mixed indoor light with a typical inaccuracy of around 25%, which is sufficient for a design process. Measurements revealed that under mixed indoor lighting of around 20 W/m2, the efficiency of solar cells in 12 commercially available PV products ranges between 5% and 6% for amorphous silicon (a-Si) cells, 4–6% for multicrystalline silicon (mc-Si) cells, and 5–7% for the monocrystalline silicon (c-Si) cells.@en

In order to better understand how ‘lead-users’ interact with PV-powered products, the behaviour of 100 people interacting with six different PV-powered products in their daily life was analysed. The sample of respondents to be observed consisted of 20 groups, each one formed by five students of Industrial Design Engineering at Technical University of Delft (TU Delft). The tested PV products are: the IKEA Sunnan lamp, the Waka Waka light, the Waka Waka power (charger and light), the Little Sun light, the Logitech solar keyboard and the Beurer kitchen weight scale. In this study the design of the six tested PV products was analysed, lead-users’ expectations were outlined, as well as their opinion of the products’ performance during and after use was addressed. Results show that respondents need reliable PV products with appealing design and improved performance.@en