Buildings are among the largest consumers of electricity in the US. A significant portion of this energy use in buildings can be attributed to HVAC systems used to maintain comfort for occupants. In most cases these building HVAC systems run on fixed schedules and do not employ any fine grained control based on detailed occupancy information. In this paper we present the design and implementation of a presence sensor platform that can be used for accurate occupancy detection at the level of individual offices. Our presence sensor is low-cost, wireless, and incrementally deployable within existing buildings. Using a pilot deployment of our system across ten offices over a two week period we identify significant opportunities for energy savings due to periods of vacancy. Our energy measurements show that our presence node has an estimated battery lifetime of over five years, while detecting occupancy accurately. Furthermore, using a building simulation framework and the occupancy information from our testbed, we show potential energy savings from 10% to 15% using our system.

[ACM Press the 2nd ACM Workshop - Zurich, Switzerland (2010.11.02-2010.11.02)] Proceedings of the 2nd ACM Workshop on Embedded Sensing Systems for Energy-Efficiency in Building - BuildSys \'10 - Occupancy-driven energy management for smart building automation

Energy harvesting technologies have been explored by researchers for more than two decades as an alternative to conventional power sources (e.g. batteries) for small-sized and low-power electronic devices. The limited life-time and necessity for periodic recharging or replacement of batteries has been a consistent issue in portable, remote, and implantable devices. Ambient energy can usually be found in the form of solar energy, thermal energy, and vibration energy. Amongst these energy sources, vibration energy presents a persistent presence in nature and manmade structures. Various materials and transduction mechanisms have the ability to convert vibratory energy to useful electrical energy, such as piezoelectric, electromagnetic, and electrostatic generators. Piezoelectric transducers, with their inherent electromechanical coupling and high power density compared to electromagnetic and electrostatic transducers, have been widely explored to generate power from vibration energy sources. A topical review of piezoelectric energy harvesting methods was carried out and published in this journal by the authors in 2007. Since 2007, countless researchers have introduced novel materials, transduction mechanisms, electrical circuits, and analytical models to improve various aspects of piezoelectric energy harvesting devices. Additionally, many researchers have also reported novel applications of piezoelectric energy harvesting technology in the past decade. While the body of literature in the field of piezoelectric energy harvesting has grown significantly since 2007, this paper presents an update to the authors' previous review paper by summarizing the notable developments in the field of piezoelectric energy harvesting through the past decade.

https://iopscience.iop.org/article/10.1088/1361-665X/ab36e4/pdf

A review of energy harvesting using piezoelectric materials: state-of-the-art a decade later (2008–2018)

Harvesting ambient wind energy with an inverted piezoelectric flag

Energy harvesting technology may be considered an ultimate solution to replace batteries and provide a long-term power supply for wireless sensor networks. Looking back into its research history, individual energy harvesters for the conversion of single energy sources into electricity are developed first, followed by hybrid counterparts designed for use with multiple energy sources. Very recently, the concept of a truly multisource energy harvester built from only a single piece of material as the energy conversion component is proposed. This review, from the aspect of materials and device configurations, explains in detail a wide scope to give an overview of energy harvesting research. It covers single-source devices including solar, thermal, kinetic and other types of energy harvesters, hybrid energy harvesting configurations for both single and multiple energy sources and single material, and multisource energy harvesters. It also includes the energy conversion principles of photovoltaic, electromagnetic, piezoelectric, triboelectric, electrostatic, electrostrictive, thermoelectric, pyroelectric, magnetostrictive, and dielectric devices. This is one of the most comprehensive reviews conducted to date, focusing on the entire energy harvesting research scene and providing a guide to seeking deeper and more specific research references and resources from every corner of the scientific community.

/pdf/energy-harvesting-research-the-road-from-single-source-to-czdnbdypb5.pdf

Energy Harvesting Research: The Road from Single Source to Multisource.

Rotational energy harvesting for self-powered sensing

This research was supported through the National Science Foundation through CEHMS and Fundamental Research Program. Piezoelectric materials were donated by American Piezo Ceramics Inc. (Mackeyville, PA).

/pdf/floor-tile-energy-harvester-for-self-powered-wireless-4rnz2haa09.pdf

Floor Tile Energy Harvester for Self-Powered Wireless Occupancy Sensing

We report an ultra-low start-up speed windmill that consists of a 72 mm diameter horizontal axis wind turbine rotor with 12 alternating polarity magnets around its periphery and a 60 mm × 20 mm × 0.7 mm piezoelectric bimorph element having a magnet at its tip. This wind turbine operates at very low Reynolds number of around 2×104, but still it has reasonably high power coefficient of about 11% at the optimal tip speed ratio of 0.7. It was found to produce peak electric power of 450 μW at the rated wind speed of 4.2 mph. An extremely low start-up wind speed of 2.4 mph was achieved by operating the bimorph in actuator mode.

Ultra-Low Wind Speed Piezoelectric Windmill

Abstract The goal of this study was to design a micro wind turbine having dimensions on the order of 1–10 cm3 for powering wireless sensor nodes. Using the parametric study based upon a computational model, the coupling factor between the blade and generator section was significantly enhanced. Building upon the formulation for the coupling factor, we derived efficiency metric for the rotational generators. A prototype was designed based upon the analytical study conducted through the combination of blade element momentum theory and ANSYS magnetics to match the performance of the generator to that of the blades. The blade diameter and depth was 72 mm and 9 mm, respectively. The generator diameter was 26 mm with total volume of 18.1 cm3. It was found that the micro wind turbine generated DC output power of 12.39 mW, 49.03 mW and 102.61 mW at 3.7 m/s, 6 m/s and 8 m/s wind speeds, respectively. The power density was computed to be 0.304, 1.204, and 2.52 mW/cm2, respectively, which are higher than all the other results reported in the literature.

Dušan Vučković

Papers

Floor Tile Energy Harvester for Self-Powered Wireless Occupancy Sensing

Ultra-Low Wind Speed Piezoelectric Windmill

Micro Wind Turbine for Powering Wireless Sensor Nodes