Systems for pervasive electronics and interfaces

Energy Harvesting Active Networked Tags (EnHANTs) are a new type of wireless device in the domain between RFIDs and sensor networks. Future EnHANTs will be small, flexible, and self-powered devices that can be attached to everyday objects that are traditionally not networked to enable "Internet of Things" applications. This work describes the design and development of the EnHANT prototypes and testbed. The current prototypes use thin-film photovoltaics optimized for indoor light harvesting, form multihop networks using ultra-low-power Ultra-Wideband Impulse Radio (UWB-IR) transceivers, and implement energy harvesting adaptive networking protocols. The current testbed enables the evaluation of different algorithms by exposing individual prototypes to repeatable light conditions based on real-world irradiance data. New approaches to characterizing the energy available to energy harvesting devices were explored. A mobile data-logger was used to record the intensity of ambient light, determine the light source, and record the acceleration from motion during different real world activities. These traces were used to model the behavior of photovoltaic and inertial energy harvesters in real world deployments and can be replayed in the EnHANTs testbed. In addition, new techniques to evaluate the efficiency of different photovoltaic technologies under indoor illumination were developed. A proof-of-concept system was built to characterize photovoltaics under a standardized set of conditions in which the radiant intensity and spectral composition of the light source were systematically varied. Techniques to structure student research projects within the EnHANTs project were developed. Project-based learning approaches were implemented to engage students using real-world system development constraints. A survey of the students showed that this approach is an effective method for developing technical, professional, and soft skills. Open source hardware was also applied to EnHANTs project and extended into other domains. A laboratory-based class in flat panel display technology was developed. The course introduces fundamental concepts of display systems and reinforces these concepts through the fabrication of three display devices. A lab kit platform was developed to enable remote students to use low-cost, course specific hardware to complete the lab exercises remotely. This platform was also applied to external projects targeted at non-university students. A workshop was developed to teach artists, designers, and hobbyists how to design and build custom user interfaces using thin-film electronics and rapid prototyping tools. Surveys of the students and workshop participants showed that this platform is an effective teaching tool and can be easily adapted and expanded

Perovskite photovoltaics on roll-to-roll coated ultra-thin glass as flexible high-efficiency indoor power generators

The internet of things revolution requires efficient, easy-to-integrate energy harvesting. Here, we report indoor power generation by flexible perovskite solar cells (PSCs) manufactured on roll-to-roll indium-doped tin oxide (ITO)-coated ultra-thin flexible glass (FG) substrates with notable transmittance (>80%), sheet resistance (13 Ω/square), and bendability, surpassing 1,600 bending procedures at 20.5-mm curvature. Optimized PSCs on FG incorporate a mesoporous scaffold over SnO2 compact layers delivering efficiencies of 20.6% (16.7 μW⋅cm−2 power density) and 22.6% (35.0 μW⋅cm−2) under 200 and 400 lx LED illumination, respectively. These represent, to the best of our knowledge, the highest reported for any indoor flexible solar cell technology, surpassing by a 60%–90% margin the prior best-performing flexible PSCs. Specific powers (W/g) delivered by these lightweight cells are 40%–55% higher than their counterparts on polyethylene terephthalate (PET) films and an order of magnitude greater than those on rigid glass, highlighting the potential of flexible FG-PSCs as a key enabling technology for powering indoor electronics of the future

University-Community Partnership For Water Technology Deployment And Co-Innovation: A Decade Of Engagement

The Ateneo de Manila University (Philippines), through its Ateneo Innovation Center (AIC), integrated existing simple technologies into one system – the Water-Electricity-Lighting System (WELS) – to respond to the need for potable water, lighting and communication. WELS is a portable clean water system with provision for lighting and cellular phone charging. It can be connected to a rainwater harvesting facility. Ten years of WELS deployments revealed its flexibility for customization in order to address varied water needs, especially for disaster response. Review of documentations done on past installation experiences highlights the value of engagement between university-based technology providers and community-recipients. This engagement leads to technology improvement and sustainability through co-innovation and contributes to community resilience and education through hands-on training. This paper narrates a decade of deployment experiences and presents the process of community involvement. We present a model of engaging the stakeholders that brings mutual benefit to both university and community through this partnership

The Battery Charging Hand-Powered Washing Machine “Project UWash”

Project UWash consists of converting the mechanical energy that goes into hand washing laundry into usable electricity. Our proof-of-concept system is composed of: an energy source (salad spinner), an energy harvester (AC generator), a regulating circuit (voltage regulator), a storage component (lithium ion batteries), and an application (charging an iPhone and USB based LED flashlight). The goal is to fully charge the LED flashlight after a one hour use and charge an iPhone to at least 50% after a 6 hour use. We were able to fully charge the flashlight in about 15 minutes but were only able to charge an iPhone to 41% after 8 hours of cranking with the AC generator. With the final UWash product we were able to power the flashlight for one and a half hours after a 15 minute use

Methods and Tools for Battery-free Wireless Networks

Embedding small wireless sensors into the environment allows for monitoring physical processes with high spatio-temporal resolutions. Today, these devices are equipped with a battery to supply them with power. Despite technological advances, the high maintenance cost and environmental impact of batteries prevent the widespread adoption of wireless sensors. Battery-free devices that store energy harvested from light, vibrations, and other ambient sources in a capacitor promise to overcome the drawbacks of (rechargeable) batteries, such as bulkiness, wear-out and toxicity. Because of low energy input and low storage capacity, battery-free devices operate intermittently; they are forced to remain inactive for most of the time charging their capacitor before being able to operate for a short time. While it is known how to deal with intermittency on a single device, the coordination and communication among groups of multiple battery-free devices remain largely unexplored. For the first time, the present thesis addresses this problem by proposing new methods and tools to investigate and overcome several fundamental challenges

Analysis of relevant technical issues and deficiencies of the existing sensors and related initiatives currently set and working in marine environment. New generation technologies for cost-effective sensors

The last decade has seen significant growth in the field of sensor networks, which are currently collecting large amounts of environmental data. This data needs to be collected, processed, stored and made available for analysis and interpretation in a manner which is meaningful and accessible to end users and stakeholders with a range of requirements, including government agencies, environmental agencies, the research community, industry users and the public. The COMMONSENSE project aims to develop and provide cost-effective, multi-functional innovative sensors to perform reliable in-situ measurements in the marine environment. The sensors will be easily usable across several platforms, and will focus on key parameters including eutrophication, heavy metal contaminants, marine litter (microplastics) and underwater noise descriptors of the MSFD. The aims of Tasks 2.1 and 2.2 which comprise the work of this deliverable are: • To obtain a comprehensive understanding and an up-to-date state of the art of existing sensors. • To provide a working basis on “new generation” technologies in order to develop cost-effective sensors suitable for large-scale production. This deliverable will consist of an analysis of state-of-the-art solutions for the different sensors and data platforms related with COMMONSENSE project. An analysis of relevant technical issues and deficiencies of existing sensors and related initiatives currently set and working in marine environment will be performed. Existing solutions will be studied to determine the main limitations to be considered during novel sensor developments in further WP’s. Objectives & Rationale The objectives of deliverable 2.1 are: • To create a solid and robust basis for finding cheaper and innovative ways of gathering data. This is preparatory for the activities in other WPs: for WP4 (Transversal Sensor development and Sensor Integration), for WP(5-8) (Novel Sensors) to develop cost-effective sensors suitable for large-scale production, reducing costs of data collection (compared to commercially available sensors), increasing data access availability for WP9 (Field testing) when the deployment of new sensors will be drawn and then realized

New devices for energy harvesting and storage: integrated third generation photovoltaic solar cells and electrochemical double layer capacitors

A worldwide conversion towards renewable energy sources has to be implemented in order to hopefully avoid the irreversible consequences of the global temperature increment caused by the greenhouse gases production. In addition, the current need to benefit from electricity in every moment of daily life, mainly in case of limited access to the electric grid, is forcing the scientific community to an intensive effort towards the production of integrated energy harvesting and storage devices. The topic of this PhD thesis is to investigate and propose innovative solutions for the integration of third generation photovoltaic (PV) cells and electrochemical double layer capacitors (EDLCs), the so-called photo-capacitors. Different photo-capacitor structures have been studied and experimentally fabricated. At first, flexibility was explored, as it is a mandatory requirement to cover non-planar or bendable surfaces, which are more and more common in nowadays portable electronics. Easily scalable fabrication processes have been used for both the harvester and the storage units, employing photopolymer membranes as electrolytes and metallic grids as current collectors and electrodes substrates. For this configuration, the best overall conversion and storage efficiency ever reported for a flexible Dye sensitized solar cell (DSSC)-based photo-capacitor was demonstrated. Subsequently, observing in the literature an evident lack in the exploitation of high voltage photo-capacitors, EDLC electrolytes with broad voltage windows have been examined. These electrolytes allowed to fabricate stable and reliable devices integrating the EDLC with a PV module and not only with a single solar cell, as normally is done. High voltage values, up to 2.5 V, have been obtained employing an ionic liquid electrolyte (Pyr14TFSI) or –alternatively- a solid state electrolyte (PEO-Pyr14TFSI) for storage section fabrication. Moreover, novel electrolyte mixtures of organic solvents and ionic liquids with good physical and electrochemical properties have been employed with the aim to increase energy density and voltage with respect to commercial EDLCs. Finally, a novel polymer-based platform has been suggested for the fabrication of an innovative “two-electrodes” self-powered device. The multifunctional polymeric layer, made of two poly(ethylene glycol)-based sections separated by a perfluorinated barrier, was obtained by oxygen-inhibited UV-light crosslinking procedure. For the energy harvesting section, one side of the polymeric layer was adapted to enable iodide/triiodide diffusion in a DSSC, while the other side empowered sodium/chloride ions diffusion and was used for on-board charge storage. The resulting photo-capacitor results in a planar architecture appreciably simplified with respect to other recently proposed solutions and is definitely more easily exploitable in low power electronics

High-performance large-area blade-coated perovskite solar cells with low ohmic loss for low lighting indoor applications

Emerging hybrid organic–inorganic perovskites with superior optoelectronic property demonstrate promising prospect for photovoltaic (PV) applications, in particular for low-lighting indoor applications e.g. within internet of things (IoT) networks or low-energy wireless communication devices. In order to prepare devices with high power output under low-illumination conditions, scalable fabrication techniques are preferred for large-area perovskite solar cells. In additions, one of the key parameters to achieve high-efficiency large-area perovskite solar cells is to minimize the ohmic loss to further boost the solar cell efficiency. Herein, a one-step blade-coating method assisted by hexafluorobenzene (HFB) was developed to deposit dense, large-area smooth and high- quality perovskite films with low ohmic loss. The as-fabricated devices demonstrated power conversion effi- ciency (PCE) of 20.7% (area of 0.2 cm2) and 16.5% (1 cm2), respectively, under standard (AM 1.5G) illumination conditions. Besides, the large-area (1 cm2) devices demonstrated a remarkable PCE of ~ 33.8% and ~ 30.0% under 1000 lx and 100 lx illumination provided by white light-emitting diode (LED) lamp, respectively. We exhibited a series-connected stack of large-area (totally active area ~ 4 cm2) perovskite photovoltaic device powering up a LED under common indoor environment as an indoor self-power indicator lamp. The analysis using a single diode model suggests that the high performance of the large-area devices under low-lighting in- door conditions is highly associated with the largely reduced ohmic losses, which particularly indicate that the perovskite films by a facile and scalable blade-coating method. The presented scalable approach paves the way to designing high-performance perovskite solar cells for a variety of emerging indoor PV application

Potential of supercapacitors in novel power converters as semi-ideal lossless voltage droppers

Electrical physics text book theory tells us that charging a capacitor is much less efficient than replenishing the energy in a discharged electro-chemical battery. If a fully discharged capacitor is pumped with a charge of Q coulombs, it stores 1/2QV while dissipating the same amount of energy in the loop resistance. However, if the same charge is pumped into a re-chargeable electrochemical cell of voltage V the energy stored in the cell is QV, while the wasted energy is determined by the loop resistance and the voltage difference across the resistance. If a rechargeable battery pack is to be replaced by a supercapacitor module, this difference could seriously affect the design of power converters required, since the power converter should stop charging at a certain point to avoid overcharging the capacitor bank. However, if a useful resistive load such as heater, DC-DC converter, inverter or a lamp load is used as a part of the loop resistance in a capacitor charging loop, a significant part of this loss can be recovered. One example of this is in the supercapacitor assisted low drop-out regulator (SCALDO) technique. This paper will detail the concept of circumvention of RC loop charging loss, theoretically quantifying the same in a generalized circuit, demonstrating how this can be applied in completely novel circuit topologies such as the supercapacitor assisted LED (SCALED) converter. The paper will provide experimental results of selected SCALDO implementations and early results of SCALED technique to support this theory