Graphene ink laminate structures on poly(vinylidene difluoride) (PVDF) for pyroelectric thermal energy harvesting and waste heat recovery

Thermal energy can be effectively converted into electricity using pyroelectrics, which act as small scale power generator and energy harvesters providing nanowatts to milliwatts of electrical power. In this paper, a novel pyroelectric harvester based on free-standing poly­(vinylidene difluoride) (PVDF) was manufactured that exploits the high thermal radiation absorbance of a screen printed graphene ink electrode structure to facilitate the conversion of the available thermal radiation energy into electrical energy. The use of interconnected graphene nanoplatelets (GNPs) as an electrode enable high thermal radiation absorbance and high electrical conductivity along with the ease of deposition using a screen print technique. For the asymmetric structure, the pyroelectric open-circuit voltage and closed-circuit current were measured, and the harvested electrical energy was stored in an external capacitor. For the graphene ink/PVDF/aluminum system the closed circuit pyroelectric current improves by 7.5 times, the open circuit voltage by 3.4 times, and the harvested energy by 25 times compared to a standard aluminum/PVDF/aluminum system electrode design, with a peak energy density of 1.13 μJ/cm³. For the pyroelectric device employed in this work, a complete manufacturing process and device characterization of these structures are reported along with the thermal conductivity of the graphene ink. The material combination presented here provides a new approach for delivering smart materials and structures, wireless technologies, and Internet of Things (IoT) devices

Characterization and modelling of meshed electrodes on free standing polyvilylidene difluoride (PVDF) films for enhanced pyroelectric energy harvesting

Flexible pyroelectric energy generators provide unique features for harvesting temperature fluctuations, which can be effectively enhanced using meshed electrodes that improve thermal conduction, convection, and radiation into the pyroelectric material. In this paper, thermal radiation energy is continuously harvested with pyroelectric free standing polyvilylidene difluoride (PVDF) films over a large number of heat cycles using a novel microsized symmetrical patterned meshed electrode. It is shown that, for the meshed electrode geometries considered in this paper, the polarization-field and current-field characteristics and device capacitance are unaffected since the fringing fields were generally small; this is verified using numerical simulations and comparison with experimental measurements. The use of meshed electrodes has been shown to significantly improve both the open-circuit voltage (from 16 to 50 V) and closed-circuit current (9 to 32 nA). The pyroelectric alternating current is rectified for direct current storage, and 30% reduction in capacitor charging time is achieved using the optimum meshed electrode coverage. The use of meshed electrodes on ferroelectric materials provides an innovative route to improve their performance in applications such as wearable devices, novel flexible sensors, and large-scale pyroelectric energy harvesters

Liquid vibration energy harvesting device using ferrofluids

Mechanical vibrations can be effectively converted into electrical energy using a liquid type of energy harvesting device comprised of a ferrofluid and a permanent magnet-inductor coil assembly. Compared to solid vibration energy harvesting devices, the liquid nature of the ferrofluid overcomes space conformity limitations which allow for the utilization of a wider range of previously inaccessible mechanical vibration energy sources for electricity generation and sensing. This report describes the design and the governing equations for the proposed liquid vibration energy harvesting device and demonstrates vibration energy harvesting at frequencies of up to 33 Hz while generating up to 1.1 mV. The proposed design can continuously convert mechanical into electrical energy for direct discharge or accumulation and storage of electrical energ

Piezoelectric-silicone structure for vibration energy harvesting: testing and modelling

Mechanical vibrations from heavy machines, building structures or the human body can be harvested and directly converted into electrical energy. In this paper the potential to effectively harvest mechanical vibrations and locally generate electrical energy using a novel piezoelectric-rubber composite structure is explored. Piezoelectric lead zirconate titanate (PZT) is bonded to silicone rubber to form a cylindrical composite-like energy harvesting device which has the potential to structurally dampen high acceleration forces and generate electrical power. The device was experimentally load tested and an advanced model was verified against experimental data. While an experimental output power of 57 μW/cm3 was obtained, the advanced model further optimises the device geometry via a relative optimisation approach. The proposed energy harvesting device generates sufficient electrical power for structural health monitoring and remote sensing applications, while also providing structural damping properties for low frequency mechanical vibrations

Wind-driven pyroelectric energy harvesting device

Pyroelectric materials have recently received attention for harvesting waste heat owing to their potential to convert temperature fluctuations into useful electrical energy. One of the main challenges in designing pyroelectric energy harvesters is to provide a means to induce a temporal heat variation in a pyroelectric material autonomously from a steady heat source. To address this issue, we propose a new form of wind-driven pyroelectric energy harvester, in which a propeller is set in rotational motion by an incoming wind stream. The speed of the propeller's shaft is reduced by a gearbox to drive a slider-crank mechanism, in which a pyroelectric material is placed on the slider. Thermal cycling is obtained as the reciprocating slider moves the pyroelectric material across alternative hot and cold zones created by a stationary heat lamp and ambient temperature, respectively. The open-circuit voltage and closed-circuit current are investigated in the time domain at various wind speeds. The device was experimentally tested under wind speeds ranging from 1.1 to 1.6 m s−1 and charged an external 100 nF capacitor through a signal conditioning circuit to demonstrate its effectiveness for energy harvesting. Unlike conventional wind turbines, the energy harvested by the pyroelectric material is decoupled from the wind flow and no mechanical power is drawn from the transmission; hence the system can operate at low wind speeds (<2 m s−1)

A modified figure of merit for pyroelectric energy harvesting

This paper reports a new figure of merit for the selection of pyroelectric materials for thermal energy harvesting applications, for example, when the material is exposed to heat or radiation of a specified power density. The figure of merit put forward and developed is of interest to those selecting materials for the design of thermal harvesting devices or the development of novel ceramic, single-crystal and composite materials for pyroelectric harvesting application

Synthesis of barium hexaferrite nano-platelets for ethylene glycol ferrofluids

Recently discovered barium hexaferrite (BaFe12O19) – based nanoplatelets form a ferromagnetic-ferrofluid which exhibits interesting magnetic properties. Manufacturing the barium hexaferrite nano-platelets via hydrothermal synthesis remains of fundamental interest and allows for optimisation of structural, magnetic, and morphological properties, which impact on ferrofluid properties. This report describes a surfactant assisted manufacturing method for an ethylene glycol based ferrofluid using hexadecyltrimethylammonium bromide (CTAB) with barium hexaferrite nano – platelets. A hexagonal nano – platelet morphology with a typical diameter up to 200 nm and thickness of a few nanometres was observed by Transmission Electron Microscopy (TEM) with stable concentrations between 10 – 200 mg/ml, while saturation magnetisation of dry particles was measured at 32.8 Am2 /kg using a Vibrating Sample Magnetometer (VSM). The manufactured barium hexaferrite - ethylene glycol ferrofluid exhibits improved thermal properties compared to previously used butanol based ferrofluids opening the way into new applications in the field of colloidal suspension

Přizpůsobení stávajícího systému zásobování ve s.p. TESLA Ostrava podmínkám tržního mechanismu

Prezenční116 - Katedra marketingu a obchoduNeuveden

Optimization of waste heat utilization in oil field development employing a transcritical Organic Rankine Cycle (ORC) for electricity generation

This study describes the low temperature waste heat exploitation during enhanced crude oil development providing a 600–900 kW continuous electric power supply under deteriorating and oscillating thermal boundary conditions. The aim of this project was to optimize the heat-to-power conversion process by maximizing the net power output employing a transcritical Organic Rankine Cycle (ORC) with R134a as working fluid. Volatile supercritical thermo-physical fluid properties demand a review of heat transfer and expansion procedures. In order to design a comprehensive and dynamic unit configuration, a flexible cycle layout with an adjustable working fluid mass flow is required. The optimization developed a positive heat exchange/pressure correlation for the net power output with reasonable cycle efficiencies of around 10% employing moderate device sizes. Changing ambient temperatures from a winter night with 10 °C to a summer day with 28 °C ambient temperature, on the US West Coast, leads to net power differences of up to 200 kW for an identical cycle configuration. Positive and negative effects result from these temperature oscillations while the heat sink temperature decreases, as does the bottom pressure. Extended available temperature and pressure differences lead to higher power outputs and cycle efficiencies. Considering higher ambient temperatures, the efficiency and power increase per heat transfer performance increase is higher than at low ambient temperatures. For this reason a “large” heat exchanger is more beneficial under warm ambient conditions than under cold ones. In addition, “large” configurations do not easily run the risk of subcritical cycle operation unlike small configurations. It is therefore important to examine the ORC machine performance over a full range of ambients. Considering a likelihood of heat source temperature degradation, an aggressive cycle design does not pay off. The selection of larger heat transfer devices almost equalizes the net power output compared to smaller ones after a heat source temperature deterioration of ∼ 6 K. Sensitivity analyses in the way presented here are an indispensable tool for achieving optimal cycle layout and operation