2,759 research outputs found
Processing and Characterization of Zinc Oxide Nanoparticle Filled Polymeric Nanocomposites
No full textAn Investigation of Polymeric Nanocomposite: Surface Functionalization and Nanofiller Effect
No full text
Investigation of effective material properties in composites with internal defect or reinforcement particles
No full textAbstractThis paper is concerned with the investigation of the effective material properties of internally defective or particle-reinforced composites. An analysis was carried out with a novel method using the two-dimensional special finite element method mixing the concept of equivalent homogeneous materials. A formulation has been developed for a series of special finite elements containing an internal defect or reinforcement in order to assure the high accuracy especially in the vicinity of defects or reinforcements. The adoption of the special finite element can greatly simplify numerical modeling of particle-composites. The numerical result provides the effective material properties of particle-reinforced composite and explains that the size of particles has great influence on the material properties. Numerical examples also demonstrate the validity and versatility of the proposed method by comparing with existing results from literatures
Photovoltaic performance of amorphous silicon flexible solar modules under mechanical loading
No full textThe applications of photovoltaic devices can be significantly expanded by directly integrating them into structures. Solar cells integrated into structures can help to power a variety of devices such as structural monitoring sensors and unmanned aerial vehicles (UAVs). However, little work has been reported in the literature on the performance of solar cells under deformation. Thus, a thorough investigation on the photovoltaic behavior of solar modules under mechanical loading is necessary in order to provide the optimal integration conditions for practical applications. The photovoltaic performance of commercially available amorphous silicon solar modules was tested under applied mechanical stresses. The current density-voltage characteristics were measured at increasing stress levels during a uniaxial tensile test. As strain increased, the short circuit current density decreased, and at strains greater than 1.4%, the fill factor, and maximum power point degraded. The performance degradation is attributed to micro-structural changes in the form of cracking under applied stress. These results are required to determine the allowable loading conditions and failure mechanism in solar module integrated structural systems
Performance of thin-film lithium energy cells under uniaxial pressure
No full textThe objective of this study was two-fold. The first objective
was to determine if the all-solid-state thin-film lithium energy
cells could withstand the minimal 550 kPa uniaxial pressure
required for composite manufacturing, which both specimens
successfully did. The second objective was to determine the
upper boundary uniaxial pressure limit of operation for the
all-solid-state thin-film lithium energy cells. The two all-solid-
state thin-film lithium energy cells tested in the present
study under uniaxial pressure performed well even when
subjected to uniaxial pressures up to about 2.0 MPa. However,
pressures higher than this value led to their degradation.
The observed degradation was due to the mechanical
failure of the sealant. Above this pressure, the sealant was
squeezed out of the space between the two mica substrates
and the lithium-metal anode layer, which in turn allowed the
ambient air to penetrate into the energy cell core, thus leading
to the rapid degradation of the charge and discharge performance
and the ultimate demise of the energy cell. We found
out that, within the observed range, uniformly distributed packaging characteristics, we found that allsolid-
state thin-film energy cells charge/discharge
cycles under upwardly increasing
uniform uniaxial pressure are extraordinarily
robust and resilient to the effects of uniaxial,
uniformly distributed uniaxial pressure had little or no effect on the charge/discharge
performance of the all-solid-state thin-film lithium energy
cells. Other power charge/draws outside of 1 mAh were
not of interest in this study for the reasons already pointed
out, albeit that they may be considered for future studies.
Apart from other considerations for failure due to the current and
constant power charge/sink of 1mAh. If the
overall structure of the energy cell is mechanically
robust, i.e., of high structural integrity,
the maximum pressure that can be
imposed is expected to be much higher than
the maximum values noted earlier.
The present study indicates that all-solidstate
thin-film energy cells can be used as an
integral part of a load-bearing multifunctional,
smart material structure if their packaging
is of sufficiently high structural integrity.
Hence, the goal of using fiber reinforced
laminated composites as the packaging
material for all-solid-state thin-film batteries
in multifunctional smart materials structures
is well within reach
Risk analysis of High-Temperature Aquifer Thermal Energy Storage (HT-ATES)
No full textThe storage of heat in aquifers, also referred to as Aquifer Thermal Energy Storage (ATES), bears a high potential to bridge the seasonal gap between periods of highest thermal energy demand and supply. With storage temperatures higher than 50 °C, High-Temperature (HT) ATES is capable to facilitate the integration of (non-)renewable heat sources into complex energy systems. While the complexity of ATES technology is positively correlated to the required storage temperature, HT-ATES faces multidisciplinary challenges and risks impeding a rapid market uptake worldwide. Therefore, the aim of this study is to provide an overview and analysis of these risks of HT-ATES to facilitate global technology adoption. Risk are identified considering experiences of past HT-ATES projects and analyzed by ATES and geothermal energy experts. An online survey among 38 international experts revealed that technical risks are expected to be less critical than legal, social and organizational risks. This is confirmed by the lessons learned from past HT-ATES projects, where high heat recovery values were achieved, and technical feasibility was demonstrated. Although HT-ATES is less flexible than competing technologies such as pits or buffer tanks, the main problems encountered are attributed to a loss of the heat source and fluctuating or decreasing heating demands. Considering that a HT-ATES system has a lifetime of more than 30 years, it is crucial to develop energy concepts which take into account the conditions both for heat sources and heat sinks. Finally, a site-specific risk analysis for HT-ATES in the city of Hamburg revealed that some risks strongly depend on local boundary conditions. A project-specific risk management is therefore indispensable and should be addressed in future research and project developments.Accepted Author ManuscriptWater Resource
Improving identification of HT-ATES performance drivers and -barriers
No full textHigh temperature aquifer thermal energy storage (HT-ATES) can potentially solve the mismatch between heat supply and demand. It can provide a large scale seasonal heat storage solution. Thereby it enables an increase in full load hours of the base heat source, which can benefit project performance on both costs and emissions. However, the limited number of successful pilot projects indicates the technology has not escaped its state of infancy. There is a gap from concept to implementation, which is signified by the disagreement of experts on performance drivers and barriers of HT-ATES. This research aims to narrow the described knowledge gap, by improving identification of HT-ATES performance drivers and barriers. Thereby it strives to improve decision making of HT-ATES implementation, and further enhance future HT-ATES application in heating projects. The broad scope of research demands both a diagnostic and design-orientated approach, and fits seamlessly with a multi-criteria decision analysis. The analysis entails the stages of creating, evaluating, comparing and ranking of case-specific scenarios. Parametric variation changes the conditions for HT-ATES implementation across the scenarios. A simulation model is developed and connected to a groundwater model to apply the parametric variation, to create the different scenarios, and consequently to produce the quantitative information for further evaluation. During the stages of creating, evaluating, comparing and ranking, the methodology systematically produces new results on the opportunities and risks introduced by HT-ATES, and additionally on the HT-ATES performance drivers and barriers. The results show that HT-ATES enables the opportunity of improving project performance with respect to the internal rate of return and emissions. Groundwater impact remains the greatest risk, but it can be minimised with smart decision making. To support the decision maker and to overcome the risk of groundwater impact, the research proposes several performance-enhancing, non-explicit guidelines. The guidelines focus on realising an HT-ATES implementation, where project performance with respect to internal rate of return, emissions and groundwater impact are balanced. Thereby they explain the major HT-ATES performance drivers and barriers. The guidelines are summarised below. The decision maker is recommended to .. 1. .. minimise the uncertainty, through thorough subsurface characterization before implementation. Secondly, to focus on aquifers with a minimum depth of 200 [m] and a minimum hydraulic conductivity of 5 [m/d] 2. .. assure network return temperatures during peak demand are below expected storage temperatures 3. .. not consider project life-times exceeding 20 years 4. .. assure yearly maximum base source heat production is always lower than yearly consumer heat demand 5. .. to strive for a flat demand curve and apply peak-shaving, by means of, for example, variable heat prices Currently, the guidelines have the purpose of giving direction to the decision maker, but they will become more explicit once the methodology is improved, and the uncertainty and number of assumptions in the model is decreased.Electrical Engineering | Sustainable Energy Technolog
Transforming Ates To Ht-Ates, Insights From Dutch Pilot Project
No full textAquifer Thermal Energy Storage (ATES) systems combined with a heat pump save energy for space heating and cooling of buildings. In most countries the temperature of the stored heat is allowed up to 25-30°C. However, when heat is available at higher temperatures (e.g. waste heat, solar heat), it is more efficient to store higher temperatures because that improves heat pump performance or makes it unnecessary. Therefore, interest in HT-ATES development is growing. Next to developing new HT-ATES projects, there is also a large potential for additional energy savings by transforming ‘regular’ low-temperature LT-ATES systems to a HT-ATES. Such a transformation is tested for a greenhouse system in the Netherlands. This greenhouse has a LT-ATES system operational since 2012, and from 2015 onwards heat is stored in the warm well at temperatures up to 45°C. In this HT-ATES transformation pilot, water quality parameters are closely monitored as well as temperature distribution in the subsurface (using DTS). Together with the operators, the results from the ATES monitoring are used to continuously improve system performance. Numerical groundwater and heat flow simulations of actual and expected well pumping data are used to evaluate how well operation can be optimized. In this paper, the optimization using monitoring results and simulations is discussed as well as general and site specific lessons/conclusions for such transformations.Water Resource
Development of a pilot site for high temperature heat pumps, with high temperature mine thermal energy storage as heat source
No full textA pilot plant for high temperature heat pumps (HTHP’s) combined with high temperature mine thermal energy storage (HT-MTES) is developed at the Fraunhofer IEG location of Bochum. The aim of the plant is to inject renewable heat into the district heating (DH) grid. The HT-MTES is a seasonal thermal storage: heat is injected during the summer and successively extracted during the cold season. A HTHP, hydraulically connected to the storage, transfers heat to the DH gri
- …
