Thesis (M.S.)--Massachusetts Institute of Technology, Dept. of Architecture, 1980. / MICROFICHE COPY AVAILABLE IN ARCHIVES AND ROTCH. / Includes bibliographical references. / The electric utilities in the United States have entered a period of slow growth due to a combination of increased capital costs and a staggering rise in the costs for fuel. In addition to this, the rise in peak power demand continues almost at historical levels resulting in lower plant utilization. Current rate schedules do little to improve the utilities' load factors and,in fact, encourage consumption. Time of day rate structures have been suggested as one load management device. This thesis investigates the impact of commercial cooling systems on the utilities supply picture and describes an off-peak cooling system which would enable a building operator to shift chiller operation to off-peak hours. The chillers draw heat from a water/glycol coolant, cooling it to 20°F. The coolant circulates through a series of coiled pipes inside a water filled storage tank. As heat is drawn from the water, ice forms around the pipe heat exchanger. With a cool ant temperature of 20°F the ice cylinder will form out to a diameter of 3.4" in 10 hours. Optimum pipe spacing is 3.5" on center. Polyethylene pipe is preferred to copper pipe for cost and fabrication reasons. The plastic pipes are grouped in discrete modules which allow flexibility in design. Building cooling loads are managed by circulating the remaining 32°F tank water through a heat exchanger coupled to the air handling units cooling coils. The warm water is returned to the tank where the heat is absorbed by the ice. Economic analysis using the present electric schedules indicate a favorable return on investment Time of day rates would make the system look even more desirable. / by Edward M. Quinlan. / M.S.

Batteries are ubiquitous in modern society, from the portable devices we use daily to the yet-to-be realized integration of batteries into the electrical grid and electrical vehicle markets. One of the primary roles of batteries to date has been to enable portability of devices, and as chemical energy storage becomes more affordable, batteries will play a larger role in how society cares for the environment by enabling technologies that are poised to decrease greenhouse gas emissions. Low cost and environmentally conscious materials are pivotal for the economic feasibility and widespread integration of batteries into new markets. Batteries operate far from equilibrium and may operate under extreme stress and varying loads, therefore, for a material to be successful in an operational battery it must meet multiple design criteria. Here, an in-depth analysis of magnetite, a low cost and abundant iron oxide studied for use as an electrode material in lithium-ion batteries, is presented. In the second Chapter, an in-depth analysis into how magnetite accepts lithium into the solid state at low depths of discharge is examined with density functional theory and a mechanistic understanding of a phase change from the parent spinel to a rocksalt-like material is presented. When magnetite is used as an electrode material in a lithium-ion battery, lithium must enter into and eject from the solid state of the host material, where the direction of lithium movement is a function of the current in the battery. In many electrode materials, magnetite included, large structural rearrangements can occur in the host material as lithium moves into and out of the lattice. These structural rearrangements can be irreversible and can contribute to overpotentials, decreasing efficiency and lifecycle for the battery. The structural rearrangements in bulk magnetite occurring due to lithium insertion are found to be driven primarily by Coulombic interactions. Additionally, the energetics and structural rearrangements for lithium insertion into defective magnetite and maghemite are examined, as these derivative structures commonly co-exist with magnetite, especially when the material is nanostructured. It is found that defective magnetite and maghemite accept lithium by a different mechanism, one that does not initially result in substantial structural rearrangement, as is the case in magnetite. In Chapter three, the effects of nanostructuring magnetite on the reversible potential are examined as a function of nanoparticle size. Due to solid-state mass-transport resistances, active electrode materials in batteries are commonly nanostructured. When a material is nanostructured, the bulk properties are often replaced due to interesting phenomena that can occur as a result of stark differences between the nanostructured material and the bulk counterpart. These differences are often attributed to surface area to volume ratios, the exaggerated role of surface energies, lattice defects, and the variation in electronic behavior, all properties which change between a bulk and nanostructured material. The reversible potential is found to be particle size dependent, and this dependence is explained, in part, by the cationic defective surfaces in the particles and the differences in surface area to volume ratio between varying particle sizes. Evidence for these defects is presented with materials characterization techniques such as XRD and EELS studies. Finally, the reversible potential at low lithiation states is predicted theoretically and found to match well to the experimentally measured potential. A study of the DFT predicted potentials and XRD characterization for multiple metastable pathways is examined in the fourth Chapter. Room temperature and long-time scale persistence of metastable phases is a pervasive phenomenon in nature. Magnetite is known to undergo both phase change and conversion reactions upon lithiation. Due to large mass transport and kinetic resistances, multiple phase changes are often observed in parallel during discharge, resulting in heterogenous phase formation in particles which can have large local lithium concentration variations. Phases which form during discharge can become kinetically trapped and the equilibrium state can therefore follow a metastable pathway. Theoretical potentials and XRD patterns are compared to the experimental patterns taken following 600 hours of relaxation following discharge at the slow rate of C/600. The evidence presented supports a metastable pathway occurring on the first voltage plateau. In the fifth Chapter, the methodologies for the density functional theory calculations are presented in full detail. This includes various studies on the more subtle electronic properties of magnetite and its lithiated derivates studied herein. These studies include examination of the charge and orbital ordering problem related to the Verwey transition in magnetite, the charge and magnetic order in the rocksalt-like lithiated magnetite, and a full theoretical description of the various phases in the Li-Fe-O ternary phase diagram that were calculated to make the relevant conclusions in Chapters 2-4. Finally, corrections to DFT predicted formation energy and volume are presented. The aim of this thesis is to use theoretical techniques to examine the lithiation of magnetite on the atomic scale and make meaningful connections to the experimentally observed electrochemical behavior of the material. To accomplish this, magnetite and the structural derivatives of magnetite that co-exist with the material under physically realistic conditions must be treated theoretically. In this thesis, ties between phenomena occurring on the atomic scale and the measurable properties of the macroscopic system, such as voltage, will be related. It will be illustrated that as a function of nanoparticle size, the magnetite system can vary in its atomic structure and the resultant electrochemistry and phase change characteristics are both affected. The findings indicate the relevance of the atomic properties and nanostructure for magnetite to the observed and measured electrochemical properties of the material.

About 50% of the solar energy absorbed at the Earth’s surface is used to drive evaporation, a powerful form of energy dissipation due to water’s large latent heat of vaporization. Evaporation powers the water cycle that affects global water resources and climate. Critically, the evaporation driven water cycle impacts various renewable energy resources, such as wind and hydropower. While recent advances in water responsive materials and devices demonstrate the possibility of converting energy from evaporation into work, we have little understanding to-date about the potential of directly harvesting energy from evaporation. Here, we develop a theory of the energy available from natural evaporation to predict the potential of this ubiquitous resource. We use meteorological data from locations across the USA to estimate the power available from natural evaporation, its intermittency on varying timescales, and the changes in evaporation rates imposed by the energy conversion process. We find that harvesting energy from natural evaporation could provide power densities up to 10 W m-2 (triple that of present US wind power) along with evaporative losses reduced by 50%. When restricted to existing lakes and reservoirs larger than 0.1 km2 in the contiguous United States (excluding the Great Lakes), we estimate the total power available to be 325 GW. Strikingly, we also find that the large heat capacity of water bodies is sufficient to control power output by storing excess energy when demand is low. Taken together, our results show how this energy resource could provide nearly continuous renewable energy at power densities comparable to current wind and solar technologies – while saving water by cutting evaporative losses. Consequently, this work provides added motivation for exploring materials and devices that harness energy from evaporation.

Bibliography: leaves 240-248.

"This work was supported by the Center for Energy Policy Research of the M.I.T. Energy Laboratory".

Eduardo M. Modiano and Jeremy F. Shapiro. / Bibliography: p. 57-58.

by Silvia Pariente. / Research supported by the Energy Research and Development Administration through Contract 421072-S. / Bibliography: leaf 37.

An intermediate temperature solid oxide fuel cell (SOFC) is developed and its performance is investigated experimentally and theoretically. In the experimental program, a gadolinium doped ceria based membrane electrode group is developed with the tape casting and screen printing methodology and characterized. An experimental setup is devised for the performance measurement of SOFCs and the performance of produced cells is investigated over a range of parameters including the electrolyte thickness, the sintering temperature, the operation temperature etc. The experimental setup is then further modified to measure the temperature distribution in the large SOFC single cells. The effects of operating parameters on the temperature distribution are investigated and the parameter spaces leading high efficiency without cracking the ceramic membrane are identified. In theoretical study a mathematical model is developed to represent the fluid flow, the heat transfer, the species transport and the electrochemical reaction in intermediate temperature of solid oxide fuel cells.The differential equations are solved numerically with a commercial CFD code which employs a control volume based approach. The temperature distribution and species distribution during theSOFC operation is analyzed. The effects of operation parameters on critical SOFC characteristics and the performance are numerically investigated over a range of parameter space. The experimental and numerical results are compared to validate the mathematical model. The mathematical model is found to agree reasonable with experimental data.

No description available.

This thesis deals with landscape architectural site-planning considerations of on-site alternative energy and material resources. On-site resources are those occurring on nearly every site. In, particular, the energies are solar, wind, water, and organic-waste; the materials are rock and earth. The thesis content includes basic information and guidelines necessary for making preliminary design decisions regarding these alternatives. Emphasis has been placed on analyzing site conditions, on measuring the available resource, on estimating the usable energy resource available, on storing the energy and on the use of the resource.In addition, there is a case study demonstrating the use of the information in the site-design process for a wind machine. The Appendix lists names and addresses of manufacturers concerned with alternative energy resources as well as containing examples of some of the literature for the wind energy industry. / Department of Landscape Architecture