Renew Infrastructure by Surface Engineering: Toward Energy Harvesting, Infrastructure Protection, and Smart Systems

Due to rapid urbanization and population expansion worldwide, addition of new construction in a built environment is not trivial while the existing infrastructure is constantly subjected to increasing demand. Any major disruption, caused by either natural or man-made actions, could have a strong impact on a large part of our nation. Therefore, protection of existing infrastructure, including building, roads, highways, bridges, etc., and enhancement of their performance and lifetime becomes of extreme importance from the viewpoint of security and economy. Inspired by human skin, emerging innovations and technologies are introduced to protect and rejuvenate our aging infrastructure by surface engineering technologies, smart sensing and control, and information management. Specifically, recent advances in energy efficient building, sun powered transportation system, and temperature regulated pavements will be introduced for improved durability and extended lifetime. Multifunctional materials and structures will be developed through physical and virtual experiments. The main approach is to design and develop bioinspired durable, smart skins to protect infrastructure with self-healing, temperature regulation, self-powered sensing and control. The fundamental understanding has been integrated into computer-aided design and manufacture for technology advancement and innovations. Finally, Dr. Yin will introduce his vision on energy in sustainable infrastructure and share some ongoing research at Columbia University

Design and Simulation of a Novel Submerged Pressure Differential Wave Energy Converter for Optimized Energy Harvesting Efficiency and Performance

A novel submerged pressure differential wave energy converter (SPDWEC) has been designed and simulated for energy harvesting under both regular waves and irregular ocean waves. As the waves pass by, the oscillating water pressure on the flexible surface of the SPDWEC moves the pistons of the power take-off (PTO) system, in such a way the wave energy is converted into electricity. Hydrodynamic responses of the SPDWEC are simulated by a numerical model calculating both the linear wave forces and the nonlinear effect of wave height reduction caused by energy extraction. The results show that the SPDWEC can reach a high power capture ratio through system optimization of the stiffness and damping of the PTO system. This innovative SPDWEC exhibits improved lifetime and maintainability by enclosing the PTO inside the WaveHouse, where the overall air pressure keeps nearly constant. As shown in Figure 1, the optimal power capture ratio of the SPDWEC ranges from 0.21 to 0.32, which means the PTO system can extract 20-30% of the incident wave energy. The ideal power capture ratio, which does not consider the nonlinear effect caused by energy extraction, is much larger than the optimal power capture ratio and is larger than one for wave periods larger than 9 s. Please click Additional Files below to see the full abstract

Inclusion-based boundary element method for design of building envelopes

The energy efficiency of a building envelope can be improved by embedding phase change materials (PCM) due to their high latent heat. However, heat transfer in the PCM-embedded composite can be quite complex due to temperature-dependent thermal properties of paraffin-based PCMs and material mismatch between PCMs and the Metrix, especially in transient heat conduction cases. This research presents an novel numerical method to simulate the transient heat conduction through a concrete wall panel containing PCM using the Green’s function. The pioneer work on simulation of PCM and heat equation applied finite element method (FEM), finite difference method (FDM). FDM discretize the time and space domain instead of taking derivatives, and it is usually applied to solve diffusion equations. However, the solutions of FDM are sensitive to time discretization and discontinuity issues. PCM capsules embedded in the domain of the building envelope serve as multiple inhomogeneities with heat source. To treat inhomogeneity problem, the PCM capsules need to be meshed to elements compatible to the matrix domain, which leads to large number of meshed elements. For inhomogeneity problem, Eshelby proposed equivalent inclusion method (EIM), filling inhomogeneities with the same material with the matrix and fictious heat source, eigen gradient of temperature. The inclusion-based boundary element method (IBEM) combines EIM with boundary element method, which only requires to mesh convex surface. Upon experimental validation, the iBEM model is used for energy efficient building design and energy savings prediction. Please click Additional Files below to see the full abstract

Materials and Designs for Heat Harvesting and Thermal Management of Asphalt Pavements

Asphalt pavements are subjected to annual, seasonal, and daily temperature fluctuations, which can lead to cracks and even failure of the pavements. Additionally, snow removal in winter on highways and parking lots in the cold-climate region is often challenging and the current snow removal approaches (salt and plowing) are neither efficient enough nor environmental-friendly. Here we propose a multifunctional system that utilizes solar and geothermal energy for heat harvesting and temperature regulation of the pavements, which allows self-de-icing in winter, cooling in summer, reduced maintenance cost, and extended life span. This new pavement technology consists of an underground heat exchanger, circulation pumps, thermal tubes, a photovoltaic system, and thermally conductive pavement overly. This presentation will focus on investigation of the thermal, electrical, and mechanical performance of the asphalt materials modified with conductive additives including carbon nanotubes and graphene nanoplatelets. Using sonication combined with an oil bath and a mechanical shear mixer, we can achieve a homogenous dispersion of the conductive modifiers in asphalt binders, which is verified by a digital microscope. Our results show that the combination of carbon nanotubes and graphene nanoplates can enhance the thermal conductivity of the asphalt binders more than any of the single-phase addition. More work on the electrical conductivity improvement in using these modifiers are underway. These modified asphalt binders are expected to increase asphalt pavements’ overall thermal conductivity, which is an integral part of the multifunctional pavement system

Experiments and micromechanical modeling of electrical conductivity of carbon nanotube/cement composites with moisture

Carbon nanotube (CNT)/cement composites have been proposed as a multifunctional material for self-sensing and traffic monitoring due to their unique electric conductivity which changes with the application of mechanical load. However, material constituent and environmental factors may significantly affect the potential application of these materials. Therefore, it is necessary to understand an influence of material constituent such as porosity and dispersion of CNT and environmental factor such as moisture on the electrical conductivity of CNT/cement composite. This paper investigates the effect of moisture on the effective electrical conductivity of CNT/cement composites. To prepare the specimens, multi-walled carbon nanotubes (MWCNTs) are well dispersed in cement paste, which is then molded and cured into cubic test specimens. By drying the specimens from the fully saturated state to the fully dry state, the effective electrical conductivity is measured at different moisture contents. As the water in the specimen is replaced by air voids, the electrical conductivity significantly decreases. Different ratios of MWCNTs to cement have been used in this study. Micromechanical models have been used to predict the effective electrical conductivities. A comprehensive model is proposed to take into account the effects of individual material phases on the effective electrical conductivity of CNT/cement composites with moisture effect

Solar window blinds with passive cooling coating and smart controllers

In the recent design of solar window blinds, the flexible solar films are attached to one side of the window blinds, making use of the building facades. As solar films absorb the heat from sunlight, a significant decrease in energy conversion efficiency becomes one obstacle for widespread commercial application. In order to tackle the difficulty, this project yields an improvement, where a passive cooling coating (PCC) is applied to another side of the window blinds. The PCC makes the temperature of window blinds lower than the ambient temperature effectively, by emitting the long-wave infrared to the outer environment. With the aid of PCC, the lower in-room temperature is attained, resulting in less energy required for air conditioners during summers. The solar window blinds involve two work states: (I) solar films are orientated towards the sunlight to harvest energy; (II) PCCs are orientated towards the sunlight to cool down the surrounding temperature. The switch of work states between (I) and (II) is achieved by smart controllers based on temperature data acquired from sensors. A prototype is fabricated to demonstrated how much energy conversion efficiency is promoted with PCCs

Influence of Coalescence on the Anisotropic Mechanical and Electrical Properties of Nickel Powder/Polydimethylsiloxane Composites.

Multifunctional polymer-based composites have been widely used in various research and industrial applications, such as flexible and stretchable electronics and sensors and sensor-integrated smart structures. This study investigates the influence of particle coalescence on the mechanical and electrical properties of spherical nickel powder (SNP)/polydimethylsiloxane (PDMS) composites in which SNP was aligned using an external magnetic field. With the increase of the volume fraction of the SNP, the aligned SNP/PDMS composites exhibited a higher tensile strength and a lower ultimate strain. In addition, the composites with aligned SNP showed a lower percolation threshold and a higher electrical conductivity compared with those with randomly dispersed SNP. However, when the concentration of the SNP reached a certain level (40 vol. %), the anisotropy of the effective material property became less noticeable than that of the lower concentration (20 vol. %) composites due to the change of the microstructure of the particles caused by the coalescence of the particles at a high concentration. This work may provide rational methods for the fabrication of aligned composites

Human Influenza A (H5N1) Cases, Urban Areas of People’s Republic of China, 2005–2006

We investigated potential sources of infection for 6 confirmed influenza A (H5N1) patients who resided in urban areas of People’s Republic of China. None had known exposure to sick poultry or poultry that died from illness, but all had visited wet poultry markets before illness

Modulation of NKT Cell Development by B7-CD28 Interaction: An Expanding Horizon for Costimulation

It has been demonstrated that the development of NKT cells requires CD1d. The contribution of costimulatory molecules in this process has not been studied. Here we show that in mice with targeted mutations of B7-1/2 and CD28, the TCRβ+α-Galcer/CD1d + (iVα14 NKT) subset is significantly reduced in the thymus, spleen and liver. This is mainly due to decreased cell proliferation; although increased cell death in the thymi of CD28-deficient mice was also observed. Moreover, in the B7-1/2- and CD28-deficient mice, we found a decreased percentage of the CD4−NK1.1+ subset and a correspondingly increased portion of the CD4+NK1.1− subset. In addition, the mice with a targeted mutation of either B7 or CD28 had a reduced susceptibility to Con A induced hepatitis, which is known to be mediated by NKT cells. Our results demonstrate that the development, maturation and function of NKT cell are modulated by the costimulatory pathway and thus expand the horizon of costimulation into NKT, which is widely viewed as a bridge between innate and adaptive immunity. As such, costimulation may modulate all major branches of cell-mediated immunity, including T cells, NK cells and NKT cells