INTERIOR PHOTOVOLTAIC DESIGN
The first idea for this lamp came in 2015. While we were studying materials interacting with light, the acrylic rods amazed us because of their extremities as bright as a light source. Then we verified that, using the light concentrated by the fluorescent sheet, we actually could improve the efficiency of a photovoltaic cell, even when the weather was not so sunny. This is how “interior photovoltaic design” idea was born. Stuff like this lamp: nice to see and energetically self-suffcient. Also: why not use acrylic rods to concentrate solar light inside the buildings while harvesting outside? This may solve many issues from the search for best inclination of the panels to possible thefts or surface maintenance and cleaning…
Acrylic rods are plastic bars made of PMMA and fluorescent molecules. They work as a light guide. Solar rays are harvested from the side and are absorbed by the fluorescent pigments. Then the light, throught multiple total reflections inside, exits from the extremities. These sheets work both with direct light and with the spread one.
We chose to make our lamps with yellow-orange and red-orange sheets because, after accurate misuration, we can say they are more efficient than the yellow-green and violet ones. Using the same amount of light, the first ones can actually concetrate more light on the cells, therefore producing more energy.
THE ROTATION SYSTEM
Our lamp turns from battery charger (during day) into an eco-lamp (during night). The PV cells and the LED strip are fixed on a PVC tube that, rotating thanks to a servomotor controlled by Arduino, alternatively positions them at the border of the sheet. In the “night setting” the sheet spreads the light emitted by the LEDs; while in the “day setting” solar light is absorbed by the sheet and concentrated on the cells that recharge the battery for the night. We planned 3 types of rotation: controlled by a button (manual mode), at settled time slots (timer mode) and according to a light sensor input (automatic mode).
The three positions switch deflects the current flow alternatively letting the rechargeable battery power a LED strip or getting recharged by the energy produced by the photovoltaic cells. Then we added a diode to avoid battery discharge when the cells stop producing energy (at night and during really cloudy days). A diode is an electronic component that allows the current flow only in one selected direction.