Concept: Electric power
Direct electric power generation using biological functions have become a research focus due to their low cost and cleanliness. Unlike major approaches using glucose fuels or microbial fuel cells (MFCs), we present a generation method with intrinsically high energy conversion efficiency and generation with arbitrary timing using living electric organs of Torpedo (electric rays) which are serially integrated electrocytes converting ATP into electric energy. We developed alternative nervous systems using fluid pressure to stimulate electrocytes by a neurotransmitter, acetylcholine (Ach), and demonstrated electric generation. Maximum voltage and current were 1.5 V and 0.64 mA, respectively, with a duration time of a few seconds. We also demonstrated energy accumulation in a capacitor. The current was far larger than that using general cells other than electrocytes (~pA level). The generation ability was confirmed against repetitive cycles and also after preservation for 1 day. This is the first step toward ATP-based energy harvesting devices.
Microbial fuel cell (MFC) technology is a promising technology for electricity production together with simultaneous water treatment. Catalysts play an important role in deciding the MFC performance. In most reports, effect of catalyst - both type and quantity is not optimized. In this paper, synthesis of nanorods of MnO2-catalyst particles for application in Pt-free MFCs is reported. The effect of catalyst loading i.e., weight ratio, with respect to conducting element and binder has been optimized by employing large number of combinations. Using simple theoretical model, it is shown that too high (or low) concentration of catalysts result in loss of MFC performance. The operation of MFC has been investigated using domestic wastewater as source of bio-waste for obtaining real world situation. Maximum power density of ∼61mW/m(2) was obtained when weight ratio of catalyst and conducting species was 1:1. Suitable reasons are given to explain the outcomes.
Optical tracking is often combined with conventional flat panel solar cells to maximize electrical power generation over the course of a day. However, conventional trackers are complex and often require costly and cumbersome structural components to support system weight. Here we use kirigami (the art of paper cutting) to realize novel solar cells where tracking is integral to the structure at the substrate level. Specifically, an elegant cut pattern is made in thin-film gallium arsenide solar cells, which are then stretched to produce an array of tilted surface elements which can be controlled to within ±1°. We analyze the combined optical and mechanical properties of the tracking system, and demonstrate a mechanically robust system with optical tracking efficiencies matching conventional trackers. This design suggests a pathway towards enabling new applications for solar tracking, as well as inspiring a broader range of optoelectronic and mechanical devices.
Bulk energy storage is generally considered an important contributor for the transition towards a more flexible and sustainable electricity system. While economically valuable, storage is not fundamentally a “green” technology, leading to reductions in emissions. We model the economic and emissions effects of bulk energy storage providing an energy arbitrage service. We calculate the profits under two scenarios (perfect and imperfect information about future electricity prices), and estimate the effect of bulk storage on net emissions of CO2, SO2, and NOx for twenty eGRID subregions in the United States. We find that net system CO2 emissions resulting from storage operation are non-trivial when compared to the emissions from electricity generation, ranging from 104 kg/MWh to 407 kg/MWh of delivered energy depending on location, storage operation mode, and assumptions regarding carbon intensity. Net NOx emissions range from -0.16 kg/MWh (i.e., producing net savings) to 0.49 kg/MWh, and are generally small when compared to average generation-related emissions. Net SO2 emissions from storage operation range from -0.01 kg/MWh to 1.7 kg/MWh, depending on location and storage operation mode.
Except for comparing the implementation costs of the Paris Agreement with potential health benefits at the national levels, previous studies have not explored the health impacts of the nationally determined contributions (NDCs) by countries and in regional details. In this Lancet Countdown study, we aimed to estimate and monetise the health benefits of China’s NDCs in the electric power generation sector, and then compare them with the implementation costs, both at the national and regional levels.
We suggest electrochemiluminescence (ECL) sensing platform driven by eco-friendly, disposable, and miniaturized reverse elec-trodialysis (RED) patches as an electric power source. The flexible RED patches composed of ion-exchange membranes (IEMs) can produce voltage required for ECL sensing by simply choosing the appropriate number of the IEMs and the ratio of salt con-centrations. We integrate the RED patch with a bipolar electrode on the microfluidic chip to demonstrate the proof-of-concept, i.e. glucose detection in the range of 0.5 - 10 mM by observing ECL emissions with naked eyes. The miniaturized RED-powered bio-sensing system is widely applicable for electrochemical sensing platforms. This is expected to be a solution for practical availability of battery-free electrochemical sensors for disease diagnosis in developing countries.
Converting ubiquitous environmental energy into electric power holds tremendous social and financial interests. Traditional energy harvesters and converters are limited by the specific materials and complex configuration of devices. Herein, it is presented that electric power can be directly produced from pristine graphene oxide (GO) without any pretreatment or additives once encountering the water vapor, which will generate an open-circuit-voltage of up to 0.4-0.7 V and a short-circuit-current-density of 2-25 µA cm-2on a single piece of GO film. This phenomenon results from the directional movement of charged hydrogen ions through the GO film. The present work demonstrates and provides an extremely simple method for electric energy generation, which offers more applications of graphene-based materials in green energy converting field.
A food waste resourceful process was developed by integrating the ultra-fast hydrolysis and microbial fuel cells (MFCs) for energy and resource recovery. Food waste was first ultra-fast hydrolyzed by fungal mash rich in hydrolytic enzymes in-situ produced from food waste. After which, the separated solids were readily converted to biofertilizer, while the liquid was fed to MFCs for direct electricity generation with a conversion efficiency of 0.245 kWh/kg food waste. It was estimated that about 192.5 million kWh of electricity could be produced from the food waste annually generated in Singapore, together with 74,390 tonnes of dry biofertilizer. Compared to anaerobic digestion, the proposed approach was more environmentally friendly and economically viable in terms of both electricity conversion and process cost. It is expected that this study may lead to the paradigm shift in food waste management towards ultra-fast concurrent recovery of resource and electricity with zero-solid discharge.
This paper reports a simple, biogenic and green approach to obtain narrow band gap and visible light-active TiO2 nanoparticles. Commercial white TiO2 (w-TiO2) was treated in the cathode chamber of a Microbial Fuel Cell (MFC), which produced modified light gray TiO2 (g-TiO2) nanoparticles. The DRS, PL, XRD, EPR, HR-TEM, and XPS were performed to understand the band gap decline of g-TiO2. The optical study revealed a significant decrease in the band gap of the g-TiO2 (E g = 2.80 eV) compared to the w-TiO2 (E g = 3.10 eV). The XPS revealed variations in the surface states, composition, Ti4+ to Ti3+ ratio, and oxygen vacancies in the g-TiO2. The Ti3+ and oxygen vacancy-induced enhanced visible light photocatalytic activity of g-TiO2 was confirmed by degrading different model dyes. The enhanced photoelectrochemical response under visible light irradiation further supported the improved performance of the g-TiO2 owing to a decrease in the electron transfer resistance and an increase in charge transfer rate. During the TiO2 treatment process, electricity generation in MFC was also observed, which was ~0.3979 V corresponding to a power density of 70.39 mW/m2. This study confirms narrow band gap TiO2 can be easily obtained and used effectively as photocatalysts and photoelectrode material.
Bioelectrochemical systems (BES) can accomplish simultaneous wastewater treatment and resource recovery via interactions between microbes and electrodes. Often deemed as “energy efficient” technologies, BES have not been well evaluated for their energy performance, such as energy production and consumption. In this work, we have conducted a review and analysis of energy balance in BES with parameters like normalized energy recovery, specific energy consumption, and net energy production. Several BES representatives based on their functions were selected for analysis, including direct electricity generation in microbial fuel cells, hydrogen production in microbial electrolysis cells, nitrogen recovery in BES, chemical production in microbial electrosynthesis cells, and desalination in microbial desalination cells. Energy performance was normalized to water volume (kWh m-3), organic removal (kWh kg COD-1), nitrogen recovery (kWh kg N-1), chemical production (kWh kg-1), or removed salt during desalination (kWh kg-1). The key operating factors such as pumping system (recirculation/feeding pumps) and external power supply were discussed for their effects on energy performance. This is an in-depth analysis of energy performance of various BES and expected to encourage more thinking, analysis, and presentation of energy data towards appropriate research and development of BES technology for resource recovery from wastewater.