Indoor Solar Lamp

Abstract

Solar photovoltaic cells are destined to become an important contributor in the renewable energy sector, also for small electrical systems inside buildings. They can be used to mobilise the electrical infrastructure, by providing an independent energy source for medium-consumption products, like decorative lighting. This thesis shows all aspects of designing and building an interior, solar powered lamp. First, the ideal position for indoor light harvesting has been investigated extensively, by recreating two typical Dutch rooms with 3D modelling software Blender. The light simulation tool RADIANCE was then used to compute the irradiance at various spots in the room, considering three standard sky types. Weather data from the KNMI was used to classify the sky conditions for every hour during two weeks in November, and the results were compared with pyranometer measurements, showing an error of 20% on a daily basis, and 5% over a five day period. The same simulation method was applied to predict the PV energy yield of four common solar cell technologies for a full year, for multiple room orientations and positions on a wall. Based on these results, three concepts were designed, corresponding to three specific room positions with different indoor light characteristics. Ultimately, one concept was chosen to be build as a prototype, with tailor-made, foil-to-foil laminated PV module, consisting of laser cut SunPower interdigitated back contact (IBC) cell technology. At standard test conditions, the measured short-circuit current was 2.37 A, with an open-circuit voltage of 21.5 V and a maximum power point of 35.9 W_p, resulting in an efficiency of 20.3%. Furthermore, a charge controller with maximum power point tracking algorithm was used to charge a 12V polymer lithium-ion battery pack. The combination of pyroelectric infrared (PIR) motion sensor detector and a light sensor module assures a conservative use of a 2.4 W strip of light emitting diodes (LED).