Economic and design analysis of daylighting a commercial tower in a hot and humid climate

Thesis (M. Arch.)--Massachusetts Institute of Technology, Dept. of Architecture, 1981.MICROFICHE COPY AVAILABLE IN ARCHIVES AND ROTCH.A forty story commercial office tower in Tampa, Florida was redesigned for daylighting. The methods are outlined and results illustrated, A cooling load comparison is done to determine the economic feasibility of such a strategy. It was found that the smaller cooling plant and greater perimeter office space could offset the increased building expense. Energy savings were also significant, especially for cooling.by Robert F. Roscow.M.Arch

The unusual case of plastic deformation and high dislocation densities with the cold sintering of the piezoelectric ceramic K0.5Na0.5NbO3

K0.5Na0.5NbO3 (KNN) can be readily densified using the cold sintering process, but despite observing high relative permittivity, the ferroelectric hysteresis is strongly suppressed along with a major suppression in the all-important piezoelectric properties. In this study, KNN is fabricated using a NaOH+KOH transient flux under a uniaxial pressure of 400 MPa and heating to 300 °C for 2 h to drive densification to 93% theoretical. It is only after a secondary heat treatment that we observe improvements of the ferroelectric hysteresis and piezoelectric properties. From a detailed structural-property-processing study using analytical transmission electron microscopy (TEM), X-ray line broadening and high field dielectric characterization methodologies we conclude that there is an unusual in-situ plastic deformation process that takes place in addition to the densification under the cold sintering process. High densities of dislocations within grains were observed that lead to multiple pinning sites that impact both the intrinsic and extrinsic contributions to the high field dielectric and piezoelectric properties. Annealing significantly reduced the dislocation density in the highly defective crystallites, observed directly from the TEM and from the sharpening of the X-ray diffraction peaks, resulting in piezoelectric and ferroelectric properties that approached those of conventionally sintered KNN

Twelve modified figures of merit of 2–2-type composites based on relaxor-ferroelectric single crystals

Twelve modified figures of merit are studied for the first time for 2–2-type composites based on relaxor-ferroelectric single crystals such as [001]-poled (1 – x)Pb(A1/3Nb2/3)O3 – xPbTiO3, where A = Mg or Zn. These modified figures of merit are related to the piezoelectric coefficients d3j* of the composite (j = 1, 2 and 3) and characterise the effectiveness of energy harvesting and transduction along the three co-ordinate axes OXj of a piezoelectric composite under a constant mechanical stress or strain. The volume-fraction dependencies of the modified figures of merit are analysed for parallel-connected 2–2 and 2–2–0 composites, and the effect of porosity (i.e. the volume fraction and shape of air pores in each polymer layer) on these figures of merit is considered for 2–2–0 composites. Linkages between the modified figures of merit and traditional energy-harvesting figures of merit d3j*g3j* are discussed for the studied 2–2-type composites. New diagrams are developed to indicate important volume-fraction ranges that correspond to a large anisotropy of exemplar modified figures of merit. Due to the large effective parameters and large anisotropy of specific figures of merit, the studied composites are of interest in piezoelectric sensor, transducer and energy-harvesting applications

The unusual case of plastic deformation and high dislocation densities with the cold sintering of the piezoelectric ceramic K0.5Na0.5NbO3

K0.5Na0.5NbO3 (KNN) can be readily densified using the cold sintering process, but despite observing high relative permittivity, the ferroelectric hysteresis is strongly suppressed along with a major suppression in the all-important piezoelectric properties. In this study, KNN is fabricated using a NaOH+KOH transient flux under a uniaxial pressure of 400 MPa and heating to 300 °C for 2 h to drive densification to 93% theoretical. It is only after a secondary heat treatment that we observe improvements of the ferroelectric hysteresis and piezoelectric properties. From a detailed structural-property-processing study using analytical transmission electron microscopy (TEM), X-ray line broadening and high field dielectric characterization methodologies we conclude that there is an unusual in-situ plastic deformation process that takes place in addition to the densification under the cold sintering process. High densities of dislocations within grains were observed that lead to multiple pinning sites that impact both the intrinsic and extrinsic contributions to the high field dielectric and piezoelectric properties. Annealing significantly reduced the dislocation density in the highly defective crystallites, observed directly from the TEM and from the sharpening of the X-ray diffraction peaks, resulting in piezoelectric and ferroelectric properties that approached those of conventionally sintered KNN

Energy harvesting from water flow by using piezoelectric materials

As a promising energy-harvesting technique, an increasing number of researchers seek to exploit the piezoelectric effect to power electronic devices by harvesting the energy associated with water flow. In this emerging field, a variety of research themes attract interest for investigation; these include selection of the excitation mechanism, oscillation structure, piezoelectric material, power management interface circuit, and application. Since there has been no comprehensive review to date with respect to the harvesting of water flow using piezoelectric materials, herein relevant work in the last 25 years is reviewed. To ensure that key aspects of the water-flow energy harvester are overviewed, they are discussed in the context of energy-flow theory, which includes the three stages of energy extraction, energy conversion, and energy transfer. The development of each energy-flow process is reviewed in detail and combined with meta-analysis of the published literature. Correlations between the harvesting processes and their contribution to the overall energy-harvesting performance are illustrated, and directions for future research are also proposed. In this review, a comprehensive understanding of water-flow piezoelectric energy harvesting is provided and it is aimed to guide future research and the development of piezoelectric harvesters for water-flow-powered devices is promoted