1. ENERGY SCAVENGING SYSTEM ABSTRACT On a daily basis, energy is constantly being wasted in both large and small scales. In the U.S alone, 56% of energy produced is wasted, and 20% of that comes from households. In an average household, most, if not all, appliances within it waste energy. Individually, the contribution of each of these sources seems trivial, but when aggregated over many users and long periods of time, the unused energy is substantial. This is a problem that energy harvesting aims to address. The purpose of this project is to combine the efforts of energy and heat scavenging systems in the context of a household. We will be focusing specifically on energy being wasted through the use of incandescent lamps, which are at most 10% efficient. The Energy Scavenging System consists of a solar and thermal module embedded in a lamp, as well as a battery charging circuit and USB charger. The solar module consists of solar cells connected in parallel to form a solar panel arranged in a way to increase the output current. The thermal module consists of a thermopile circuit attached to a heat sink in order to increase the temperate gradient it is exposed to, therefore improving the current and voltage it generates. The harvested energy will be stored in a battery for subsequent use. AUTHORS Laura Durrance (EE’12) Jefta Jawi (EE ’12) Agatha Oliveira (EE’12) ADVISOR Dr. Jorge Santiago DEMO TIMES Thursday, April 19 th, 2012 9:30, 10:00 AM 2:30, 3:00 PM Senior Design Team 11 University of Pennsylvania Department of Electrical and Systems Engineering SYSTEM DESIGN The thermopile works by providing a voltage proportional to the temperature difference across its terminals. The hot side was covered in black carbon tape to increase the heat absorbance. The cold side was attached to an aluminum block in order to increase heat capacitance. EH4205 Low voltage booster used to increase voltage to match solar cell output ENERGY STORAGE SUBSYSTEM THERMOPILE SUBSYSTEM Converts light energy into electrical energy by means of photovoltaic effect Sanyo Energy AM 48.1mm x 55.1mm solar cells Solar cell characteristics 5.5V open circuit voltage 10.9412mA short circuit current Two solar cells were connected in series to get providing 12V and 10mA of current. There are 10 sets of the series combinations, providing a current of 123.40mA SOLAR CELL SUBSYSTEM RESULTS The lamp design chosen was a 5 heads floor lamp. Each head uses a 60-watt bulb. Each incandescent bulb is at most 10% efficient. Therefore, the energy wasted by the entire lamp is 270 watts. The solar cells output a typical voltage of 10.63V and a typical current of 123.40mA. Therefore, the energy recovered from the solar cell subsystem is 1.3 watts The thermopile outputs a typical voltage of 0.4 and a typical current of 80mA. Therefore, the energy recovered from the thermopile subsystem is 0.032 watts This means that 0.5% of the energy wasted is recovered by the lamp. This energy was then used to charge the LiPo battery. The TI BQ24650 High efficiency synchronous switch- mode charge controller was used to charge battery One of the main features of this chip is its maximum power point tracking capability The input to the chip is the voltage and current gathered from the energy scavenging system The chip then outputs the voltage and current necessary to charge the battery. The battery utilized in this system was a 7.4V 1300mAh SkyLite LiPo battery LEDs indicate when the battery is being charged and when the charging process has been finalized A USB charger was designed so that the energy harvested can be used to power a small electronic device. Devices such as the iPhone, which requires a voltage of 5V and a current of 1A to be charged. This circuit works by regulating the voltage from the battery from 7.4V to 5V by using the 7805 regulator. The resistor network provides the correct data points for the USB connection. An LED was used to indicate when the level of the battery was too low. If the LED is off, the battery should be removed from the system to avoid over discharging. Since the lamp will always be used for several hours a day, our system allows for energy which would be otherwise lost to be used for different purposes. Several appliances can be charged using our system, eliminating the need to charge them from a wall socket. The table below shows some devices that can be powered with the USB charger, along with their current and voltage requirements (which are met by our system): The charger is also portable, meaning that these devices can be charged wherever the user is, at any time. DeviceVoltage (V)Current (A) iPhone51 Blackberry5.7