bluuebunny/crossref_metadata_2025 huggingface dataset:
Multi-Objective Optimization of a Combined Power and Cooling Cycle for Low-Grade and Mid-Grade Heat Sources
Authors: Demirkaya Gokmen , Besarati Saeb M. , Vasquez Padilla Ricardo , Ramos Archibold Antonio , Rahman Muhammad M. , Goswami D. Yogi , Stefanakos Elias L.
Published: March 2012

Optimization of thermodynamic cycles is important for the efficient utilization of energy sources; indeed it is more crucial for the cycles utilizing low grade heat sources where the cycle efficiencies are smaller compared to high temperature power cycles. This paper presents the optimization of a combined power/cooling cycle, also known as the Goswami Cycle, which combines the Rankine and absorption refrigeration cycles. The cycle uses a special binary fluid mixture as the working fluid and produces power and refrigeration. In this regard, multi-objective genetic algorithms (GA) are used for Pareto approach optimization of the thermodynamic cycle. The optimization study includes two cases. In the first case the performance of the cycle is evaluated as it is used as a bottoming cycle, and in the second case as it is used as a top cycle utilizing solar energy or geothermal sources. The important thermodynamic objectives that have been considered in this work are, namely, work output, cooling capacity, effective first law and exergy efficiencies. Optimization is carried out by varying the selected design variables; boiler temperature and pressure, rectifier temperature, and basic solution concentration. The boiler temperature is varied between 70–150 °C and 150–250 °C for the first and the second cases, respectively.
Preliminary Analysis and Testing of the AWOG: A Novel Non-Rotational Wind Energy Extraction Device
Authors: French Jesse J. , Sheets Colton T.
Published: March 2012

This paper highlights the work done by the authors to develop and test a novel, biologically inspired, non-rotational wind energy extraction device. This device capitalizes on the principles of a wind deflected shaft and vortex induced vibrations to generate micro-scale power. Piezoelectric and magnetic flux methods are explored as options to convert the stored energy of mechanical deflection to electrical power. The device is modeled after long-stemmed grasses, grains, and bamboos and geometrically mimics their aspect ratio in order to replicate their movement in low altitude, turbulent flows. This design is based on a significant sampling of the shaft aspect ratios and head shapes of naturally occurring biological samples collected in the field. This concept has been affectionately christened the AWOG (Amber Waves of Grain) and shows promise for use in highly turbulent, low-level air flows close to the ground or mounting surface. Potential operating sites of the AWOG, include locations very close to ground level, along building rooflines, and in urban settings. To determine the efficiency and power output of a single AWOG unit, wind tunnel testing and in-situ field testing were performed. Power stored in a single deflected AWOG has been experimentally determined to be 430 w/m^2, which is comparable to existing wind turbine designs. Initial tests outlined in this paper are only able to recover a fraction of the stored energy. Practical applications of AWOG units would be to use them in formation and examinations are included for several proposed grouping methods. Analysis is performed to determine the ideal arrangement for grouped AWOG units based on experimental and field data from biological specimens and wind tunnel tests. This includes analyzing the effect that different configurations have on individual power output and efficiency of the formation as a whole. Recommendations are made as to the feasibility of use in a variety of settings and consideration is given concerning scaling of the AWOG to the micro-scale and to larger scales.
Estimating Reliability of a System of Electric Generators Using Stochastic Integration of Renewable Energy Technologies (SIRET) in the Renewable Energy Optimization (REO) Method
Authors: Walker Andy
Published: March 2012

The Renewable Energy Optimization (REO) screening method identifies the optimal combination of renewable energy technologies for a site subject to constraints imposed by the organization or by the physical limits of the site. The REO method calculates the life-cycle cost of a combination of renewable energy generators and then uses a solver to iterate until it finds the size of each generator that minimizes life-cycle cost. In 2007, NREL developed a method called “Stochastic Integration of Renewable Energy Technologies” (SIRET) [1, 2, 3, 7] to account for the interactions between multiple generators serving a load. SIRET calculates the quantity of electricity bought from and sold to the utility within a time interval, which allows an accurate economic model when the retail rate and sell-back rate of electricity differ. These two energy quantities calculated by SIRET are used to calculate utility costs in the REO life-cycle cost calculation. When one or more emergency generators and/or the electric grid are included with renewables as generation resources in the analysis, the SIRET algorithm can also be used to estimate the reliability of the system, where reliability is defined as the fraction of time in which any combination of generation resources is sufficient to meet the load. The SIRET algorithm is capable of analyzing any number of generation resources, and currently includes photovoltaics (PV), wind, solar thermal electric, biomass gasification, anaerobic digestion, landfill gas, daylighting, and an arbitrary number of emergency generators as well as the electric grid. An example consisting of PV, wind, and an emergency generator is presented to illustrate the method. This method is based on very simple and heuristic methods, and thus should be regarded only as a relative indicator of reliability, rather than an accurate prediction, but agreement with hourly simulation is presented as one benchmark of the effectiveness of the method.
Measurements and Simulations of Electrical Demand From Residential Buildings for Peak Load Reduction
Authors: Sadineni Suresh B. , Atallah Fady , Boehm Robert F.
Published: March 2012

Due to extreme summers in the Desert Southwest region of the U.S., there are substantial peaks in electricity demand. Through a grant from the U.S. Department of Energy, a consortium has been formed between the University of Nevada Las Vegas, Pulte Homes, and NV Energy (formerly known as Nevada Power) to address this issue. The team has been developing a series of approximately 200 homes in Las Vegas to study substation level peak electric load reduction strategies. The targeted goal of the project is a peak reduction of more than 65%, between 1:00 PM and 7:00 PM, compared to code standard housing developments. Energy performances of the homes have been monitored and the results were stored for further analysis. A computer model has been developed for one of the homes in the new development using building energy simulation code, ENERGY 10. Influence of different peak reduction strategies on the electricity demand from the home has been analyzed using the developed model. The simulations predict that the annual electrical energy demand from the energy efficient home compared to a code standard home of the same size decreases by 38%. The simulations have also shown that the energy efficient measures reduce the electricity demand from the home during the peak periods. Simulations on the photovoltaic (PV) orientation show that a south oriented PV system is best suited for a home enrolled to flat electricity pricing schedule and a 220°(40° west of due south) orientation is economically optimal for homes enrolled in the time-of-use pricing. The energy efficiency methods in the building coupled with a 220° oriented PV and two degrees thermostat setback for three hours (from 3:00–6:00 PM) can reduce the peak demand by 62% compared to a code standard building of the same size.
Solar Assisted Desiccant Cooling Simulation for Different Climate Zones
Authors: Concina Wendell , Sadineni Suresh , Boehm Robert
Published: March 2012

Evaporative cooling is among the most cost effective methods of air conditioning, but is less efficient in humid climates. An evaporative system coupled with a desiccant wheel can operate effectively in broader climatic conditions. These cooling systems can substitute traditional vapor compression air conditioning systems as they involve environmentally friendly cooling processes with reduced electricity demand (which is commonly generated from fossil fuels) along with no harmful CFC based refrigerant usage. Furthermore, direct utilization of low grade energy sources such as solar thermal energy or flue gas heat can drive the desiccant regeneration process, thus providing economic benefits. This study presents the results of simulations of desiccant cooling system performance for different climate zones of the United States. Solar assisted desiccant air conditioning is particularly useful where there are abundant solar resources with high temperature and humidity levels. Building energy simulations determined cooling energy requirements for the building. Simulation of an evacuated solar hot water collector model provided the heat energy available for regeneration of the desiccant. Solid desiccant of common material such as silica gel used in a rotary wheel is simulated using established validated computer models; this is coupled with evaporative cooling. Transients of the overall system for different cooling loads and solar radiation levels are presented. Finally, feasibility studies of the desiccant cooling systems are presented in comparison with traditional cooling system. Further analysis of the data presents optimization opportunities. Energy savings were achieved in all climatic conditions with decreased effectiveness in more humid conditions.
Comparison of Two Linear Collectors in Solar Thermal Plants: Parabolic Trough vs Fresnel
Authors: Giostri A. , Binotti M. , Silva P. , Macchi E. , Manzolini G.
Published: March 2012

Parabolic trough can be considered the state of the art for solar thermal power plants thanks to the almost 30 years experience gained in SEGS and, recently, Nevada Solar One plants in US and Andasol plants in Spain. One of the major issues that limits the wide diffusion of this technology is the high investment cost of the solar field and, particularly, of the solar collector. For this reason, since several years research activity has been trying to develop new solutions with the aim of cost reduction. This work compares commercial Fresnel technology with conventional parabolic trough plant based on synthetic oil as heat transfer fluid at nominal conditions and evaluates yearly average performances. In both technologies, no thermal storage system is considered. In addition, for Fresnel, a Direct Steam Generation (DSG) case is investigated. Performances are calculated by a commercial code, Thermoflex®, with dedicated component to evaluate solar plant. Results will show that, at nominal conditions, Fresnel technology have an optical efficiency of 67% which is lower than 75% of parabolic trough. Calculated net electric efficiency is about 19.25%, while parabolic trough technology achieves 23.6%. In off-design conditions, the gap between Fresnel and parabolic trough increases because the former is significantly affected by high radiation incident angles. The calculated sun-to-electric annual average efficiency for Fresnel plant is 10.2%, consequence of the average optical efficiency of 38.8%, while parabolic trough achieve an overall efficiency of 16%, with an optical one of 52.7%. An additional case with Fresnel collector and synthetic oil outlines differences among investigated cases. Finally, because part of performance difference between PT and Fresnel is simple due to different definitions, additional indexes are introduced in order to make a consistent comparison.
Improved Switchgrass Gasification Using Molten Carbonate Salts
Authors: Hathaway Brandon J. , Honda Masanori , Davidson Jane H.
Published: March 2012

The use of concentrated solar energy for gasification of biomass is an efficient means for production of hydrogen rich synthesis gas. Utilizing molten alkali-carbonate salts as a reaction and heat transfer medium offers enhanced heat transfer, faster kinetics, and stability for solar transients. The effect of the molten salts on gasification of switchgrass is examined in terms of the reaction rates and product composition. Experiments were carried out in an electrically heated molten salt reactor. Switchgrass was gasified with steam at 1200 K in an inert gas and with salt. Reactivity indexes were calculated from measured gas production rates. Product composition was established via mass spectrometry. In salt, the total useful syngas production increased by 30% while reducing net carbon dioxide production. Reactivity increased 81%. Secondary products, in the form of condensable tar and unreacted char, were reduced by 77%.
Comparative System Analysis of Direct Steam Generation and Synthetic Oil Parabolic Trough Power Plants With Integrated Thermal Storage
Authors: Feldhoff Jan Fabian , Schmitz Kai , Eck Markus , Schnatbaum-Laumann Lars , Laing Doerte , Ortiz-Vives Francisco , Schulte-Fischedick Jan
Published: March 2012

Parabolic trough power plants are currently the most commercially applied systems for CSP power generation. To improve their cost-effectiveness, one focus of industry and research is the development of processes with other heat transfer fluids than the currently used synthetic oil. One option is the utilization of water/steam in the solar field, the so-called direct steam generation (DSG). Several previous studies promoted the economic potential of DSG technology [1–3]. Analyses’ results showed that live steam parameters of up to 500°C and 120 bars are most promising and could lead to a reduction of the levelized electricity cost (LEC) of about 11% [4]. However, all of these studies only considered plants without thermal energy storage (TES). Therefore, a system analysis including integrated TES was performed by Flagsol GmbH and DLR together with Solar Millennium AG, Schott CSP GmbH and Senior Bergho¨fer GmbH, all Germany. Two types of plants are analyzed and compared in detail: a power plant with synthetic oil and a DSG power plant. The design of the synthetic oil plant is very similar to the Spanish Andasol plants [5] and includes a molten salt two-tank storage system. The DSG plant has main steam parameters of 500 °C and 112 bars and uses phase change material (PCM) for the latent and molten salt for the sensible part of the TES system. To enable comparability, both plants share the same gross electric turbine capacity of 100 MWel, the same TES capacity of nine hours of full load equivalent and the same solar multiple of the collector field of about two. This paper describes and compares both plants’ design, performance and investment. Based on these results, the LEC are calculated and the DSG plant’s potential is evaluated. One key finding is that with currently proposed DSG storage costs, the LEC of a DSG plant could be higher than those of a synthetic oil plant. When considering a plant without TES on the other hand, the DSG system could reduce the LEC. This underlines the large influence of TES and the still needed effort in the development of a commercial storage system for DSG.
Geothermal Power Cycle Analysis for Commercial Applicability Using Sequestered Supercritical CO2 as a Heat Transfer or Working Fluid
Authors: Janke Brian , Kuehn Thomas
Published: March 2012

Thermodynamic analysis has been conducted for geothermal power cycles using a portion of deep ground sequestered CO2 as the working fluid. This allows energy production from much shallower depths and in geologic areas with much lower temperature gradients than those of current geothermal systems. Two different system designs were analyzed for power production with varying reservoir parameters, including reservoir depth, temperature, and CO2 mass flow rate. The first design is a direct single-loop system with the CO2 run directly through the turbine. This system was found to provide higher system efficiency and power production, however design complications such as the need for high pressure turbines, two-phase flow through the turbine and the potential for water-CO2 brine mixtures, could require the use of numerous custom components, driving up the cost. The second design is a binary system using CO2 as the heat transfer fluid to supply thermal energy to an Organic Rankine Cycle (ORC). While this system was found to have slightly less power production and efficiency than the direct system, it significantly reduces the impact of design complications associated with the direct system. This in turn reduces the necessity for certain custom components, thereby reducing system cost. While performance of these two systems is largely dependent on location and operating conditions, the binary system is likely applicable to a larger number of sites and will be more cost effective when used in combination with current off-the-shelf ORC power plants.
Sustainable IT Ecosystems: Enabling Next-Generation Cities
Authors: Hoover Christopher , Watson Brian , Sharma Ratnesh , Charles Sue , Shah Amip , Patel Chandrakant , Marwah Manish , Christian Tom , Bash Cullen
Published: March 2012

In this paper, we describe an integrated design and management approach for building next-generation cities. This approach leverages IT technology in both the design and operational phases to optimize sustainability over a broad set of metrics while lowering costs. We call this approach a Sustainable IT Ecosystem. Our approach is based on five principles: ecosystem-scale life-cycle design; scalable and configurable infrastructure building blocks; pervasive sensing; data analytics and visualization; and autonomous control. Application of the approach is demonstrated for two case studies: an urban water infrastructure and an urban power microgrid. We conclude by discussing future opportunities to co-design and integrate these independent infrastructures, gaining further efficiencies.
Grid-Independent Air Conditioning Using Underground Thermal Energy Storage (UTES) and Reversible Thermosiphon Technology: Experimental Results
Authors: Kekelia Bidzina , Udell Kent S.
Published: March 2012

Thermal energy storage in subsurface soils can produce both inexpensive capacity and storage timescales of the order of a year. In concept, storing excess ambient or solar heat in summer for future winter use and winter “cold” for summer air conditioning can provide essentially zero-carbon space heating and cooling. An innovative ground coupling using a reversible (pump-assisted) thermosiphon with its high heat flux characteristics, intrinsic to two-phase heat pipes, as an inground heat exchanger is proposed and its performance is evaluated in a series of lab-scale experiments. Extraction and injection of heat from/into the water-saturated sand with a single thermosiphon unit representing a cell in an array of thermosiphons is modeled. These results demonstrate that near freezing point of water, due to weak or no natural convection, heat transfer is mainly due to conduction. Also, due to low energy input requirement for pumping working fluid and high heat transfer potential of the reversible thermosiphon, seasonal thermal energy or “cold” storage can be provided for low energy air conditioning applications.
Enhanced Heat Collection Element Performance Through Surface Geometry
Authors: Webb Rebecca N. , Horvath Julie A. , Boartfield Allen G.
Published: March 2012

Concentrated solar power produces electricity by using a mirror to focus sunlight on a fluid filled tube known as a heat collection element. The fluid inside the element is then used as a heat source for steam generation in a conventional steam turbine power plant. It is possible that adding microstructures to the surface of the conventionally smooth heat collection element could improve system efficiency, motivating the need for an improved understanding of the radiation characteristics of a microstructured surface. The goal of this work was to experimentally determine the impact of different microscale geometries on net radiative heat gain when angle of incidence was varied. Five test pieces, one with a smooth surface and four with microstructured surfaces were compared experimentally for a given infrared energy input and flow rate and five different angles of incidence. Over the entire range of angles the microstructured test pieces absorbed more energy than the smooth test piece.
Uncertainty Analysis and Characterization of the SOFAST Mirror Facet Characterization System
Authors: Finch Nolan S. , Andraka Charles E.
Published: March 2012

Sandia Optical Fringe Analysis Slope Tool (SOFAST) is a mirror facet characterization system based on fringe reflection technology that has been applied to dish and heliostat mirror facet development at Sandia National Laboratories and development partner sites. The tool provides a detailed map of mirror facet surface normals as compared to design and fitted surfaces. In addition, the surface fitting process provides insights into systematic facet slope characterization, such as focal lengths, tilts, and twist of the facet. In this paper, a preliminary analysis of the sensitivities of the facet characterization outputs to variations of SOFAST input parameters is presented. The results of the sensitivity analysis provided the basis for a linear uncertainty analysis which is also included here. Input parameters included hardware parameters and SOFAST setup variables. Output parameters included the fitted shape parameters (focal lengths and twist) and the residuals (typically called slope error). The study utilized empirical propagation of input parameter errors through facet characterization calculations to the output parameters, based on the measurement of an Advanced Dish Development System (ADDS) structural gore point-focus facet. Thus, this study is limited to the characterization of sensitivities of the SOFAST embodiment intended for dish facet characterization. With reasonably careful setup, SOFAST is demonstrated to provide facet focal length characterization within 0.5% of actual. Facet twist is accurate within ± 0.03 mrad/m. The local slope deviation measurement is accurate within ± 0.05 mrad, while the global slope residual is accurate within ± 0.005 mrad. All uncertainties are quoted with 95% confidence.
Initial Development of Optimum Biomass Pellets
Authors: Eggerstedt Kyle , Wang Xia , Leidel James , Kobus Krzytoff
Published: March 2012

Renewable energy has become a major focus in today’s world of depleting energy resources. Biomass is starting to be utilized because it can be continually created within a reasonable period of time. Biomass particles are pressurized together in a pellet shape. The pellets are fed into a combustion chamber (stove) and burnt to create energy. The objective of this research is to test a range of pellet compositions and investigate their corresponding characteristics in the combustion process in order to maximize their energy output. The pellets investigated include single materials such as wood or various mixtures such as wood and grass. The pellets were tested to check the various criteria including the moisture content, density and energy content. Moisture content was found using a scale and desiccators. A thermogravimetric analyzer (TGA) was used to determine the burning temperature of biomass, its weight composition and ash content. A calorimeter was used to find energy content. The Coats-Redfern Method along with a TGA was chosen for the analysis of the activation energy of biomass pellets. Among four types of pellets tested, the hardwood premium pellets has the lowest ash content of .66%. Premium Pellets also had the best energy content of 19.16 MJ/kg. Beet Pulp Pellets had the lowest activation energy of all the materials with 99.92 kJ/mol activation energy. Overall the hardwood pellets performed the best but could be improved with the addition of other biomasses. An optimum pellet may be created with a mixture of multiple materials.
A Methodology to Quantify Residential Energy-Efficiency in a Heating-Dominated Climate
Authors: Casey Sean , Bianchi Marcus , Roberts David , Krarti Moncef
Published: March 2012

A methodology is presented that uses readily available information such as energy consumption data, limited building characteristics, and local daily temperature data to identify energy-inefficient homes in a heating-dominated climate. Specifically, this methodology is applied to 327 owner-occupied, single-family homes in Boulder, Colorado, which are compared to simulated prototype homes. A home’s energy-efficiency is characterized by its construction properties, such as insulation R-values, infiltration rates, and mechanical equipment efficiencies. Previous research indicates a close relationship between these properties and inverse modeling parameters, such as the heating slope (HS) values from variable-base degree-day (VBDD) models. The methodology compares the HS values from VBDD models of monthly natural gas consumption data to simulated HS values of reference homes. The difference, ΔHS, is the primary criterion for quantifying a home’s energy-efficiency and energy retrofit potential. To validate the results of the methodology, the results from a detailed energy assessment of a field-test home are used. Using the natural gas consumption noted in the utility data and historical weather data for the dates of bill, a VBDD model is created and the HSfield-test is calculated. HSreference of a 2009-IECC reference home of identical size is calculated and the difference, ΔHS, is calculated. Using UA-values and mechanical efficiencies from the energy assessment report, the theoretical HS values are calculated for both the assessed home and the reference home. The difference, ΔHStheoretical, is calculated. Overall, a 24% difference is found between the ΔHS and ΔHStheoretical. While the accuracy can be improved, the implication is that the energy-efficiency of homes can be inferred from inverse modeling of utility data under a specific set of conditions.
A Novel Proposed Method for Achieving Cities With Zero Anthropogenic Methane Emissions
Authors: Pinzo´n Coronado Horacio , Corredor Marti´nez Lesme , Barsallo Pacheco Nilma Rosa , Lacera Rinco´n Armando Luis
Published: March 2012

The growth of urban population is increasing quickly worldwide, especially in developing countries. This fact substantially affects the generation of waste, whether liquid, gaseous or solid, which are deposited in places commonly known as landfills. The organic matter in solid residues promotes methane production, which is a high impact greenhouse gas. Researches on uses of biogas from anaerobic fermentation’s processes have been made; nevertheless most have focused on Biogas direct burning or on site generation of electricity, and a few on biofuel production for transportation purposes. Regardless of the development of technologies to use biogas as renewable energy source, there is not wide documentation of projects involving population growth and urban planning with sustainable power generation based on organic residues produced within cities. For the Latin American case the implementation of technologies for biogas utilization is poor and projects that allow the integration of methane production based on population growth with its energy needs would highly promote planning and implementation of policies for sustainable resources exploitation. Their impact in the short, medium and long term would be unprecedented at all levels. The model proposed here serves as analysis tool for developing sustainable energy policies based on urban growth prognostics leading to 100% utilization biogas emissions for both electrical and fuel power generation. In the methodology used is performed an identification and geographic location of the main emissions sources such as landfills and sewage plants. Main solid waste generation sources are identified and an estimation of organic residues amount is made. Based on organic residues and methane production models provided by EPA, it is possible to obtain a long-term estimate of landfill biogas generation according to demographic growth prognostics. The overall power generation provided by a purification and separation plant is obtained from past estimations. Electrical energy and pure methane are produced. Model is validated in Panama City, which authors analyze the implementation of a separation plant whose objective is the adaptation of biogas for automotive purposes covering all their energy demand with electrical energy generated from a percentage of collected biogas. It hopes to have a major impact on the public urban transport fleet of Panama and a future implementation of pipeline that will feed the energy requirements of the city.
Assessment of the Potential of Installing Space Cooling-Only Ground Source Heat Pumps in a Tropical Country
Authors: Cardoza Yves Camelot , Francia Guillermo Xavier , Martinez Luis Aaron
Published: March 2012

The present article examines the technical, economic and environmental feasibility of installing a cooling-only ground source heat pump in a tropical country. The study is based on an existing university building at Universidad Centroamericana in El Salvador. The building was modeled using an energy simulation program in order to characterize its energy performance and compare the energy efficiency of the proposed ground source heat pump system to a conventional direct expansion system. In addition to standard energy modeling, a finite-element model was also developed in order to determine ground temperature distribution and heat island effects due to the ground source heat pump system. Modeling results predicted that the proposed system would reduce energy consumption by 23% annually, compared to a conventional system. Additional cost savings, associated with a reduction in maintenance and replacement costs, reduce operational costs by 37% over the life of the project. The proposed design was also optimized using energy modeling and a first cost estimate was obtained. An economic analysis predicted that the simple payback period of the system would be on the order of six years. The paper analyzes the technical, economic and environmental advantages of the concept and the potential barriers for implementation.
Performance Analysis of Solar Chimneys of Different Physical Scales Using CFD
Authors: Shams Ehsan , Gross Andreas , Fasel Hermann
Published: March 2012

The available power of a solar chimney power plant (SCPP) is investigated based on axi-symmetric simulations that are carried out with Ansys Fluent. Different combinations of tower height and collector radius are investigated. The simulations show that the available power is proportional to the product of tower height and collector area. This scaling law holds for a wide parameter range, even for relatively disparate ratios of tower height and collector diameter. Three different turbulence models are employed for the calculations of the large power plants. Results obtained with a Reynolds stress model are found to be most accurate. In addition, experiments with an instrumented laboratory scale model are conducted. Temperature measurements obtained from this model are found to compare well with the simulation data.
Towards Zero Net Energy at a Community-Scale Level: Case Study at UC Merced
Authors: Diaz Gerardo , Elliott John , Coimbra Carlos F. M.
Published: March 2012

The recent establishment of the University of California Merced presents a unique and invaluable opportunity to plan, carry out, and monitor the development and growth of a new university campus utilizing the most advanced sustainable concepts and technologies available today. Although retrofitting and obsolete building construction codes are not an issue, this community-scale project is already facing operational questions related to the integration of renewable resources. The actual operation at a high percentage of renewable power generation and building efficiency provides invaluable information to analyze the operation that mimic or even exceed California’s 20% and future 33% renewable portfolio standards. UC Merced is already working to meet the commitment of zero net energy by 2020 that is part of the triple-zero challenge that also includes elimination of landfill waste and climate neutrality in the same timeframe. In this work, current findings about this integration strategy are provided.
Reactive Ceramics of CexSc1−xO2−Δ for Solar Hydrogen Production by Two-Step Water Splitting
Authors: Lee Chong-il , Meng Qing-long , Kaneko Hiroshi , Tamaura Yutaka
Published: March 2012

This paper describes the enhancement of the H2-generation reactivity by Sc doping in the CeO2. The evolved O2 gas (3.48ml/g) and H2 gas (7.00ml/g) for Ce0.97Sc0.03O1.985 are higher than those of Ce0.9Zr0.1O2, indicating that Sc-doping enhances the two step water splitting reactivity compared to the Zr-doping. The molar ratio of the H2 and O2 gases is nearly two, which suggests nearly completion of each step reaction for the H2O decomposition. The O2-releasing reactivity of Sc-doped ceria (Ce0.97Sc0.03O1.985) is nearly the same as that of Zr-doped one (Ce0.9Zr0.1O2), whereas the H2-generation reactivity is much different due to improvement of the H2-generation reactivity by Sc-doping. To examine the reason for the improvement, the ionic conductivity of Sc-doped and Zr-doped ceria has been measured with AC impedance spectroscopy. The activation energies of bulk conduction estimated from the impedance measurement are 1.09eV (Sc-doped) and 1.48eV (Zr-doped), respectively, in the temperature range of 400–800°C. This indicates that the oxygen deficient site movement of the Sc-doped ceria is more active than Zr-doped ceria. It could be said that the anion site can move more readily toward the surface of the ceramics by Sc-doping. This would facilitate the oxygen storage process (the H2-generation reaction).
Feasibility Study of an Organic Rankine Cycle System Coupled to a Diesel Engine
Authors: DiCarlo Joseph , Wallace James S.
Published: March 2012

A feasibility study has been conducted for an organic Rankine cycle (ORC) system coupled to the exhaust of a Diesel engine generator. The objective of this study was to determine the possible electrical generation of the ORC using the exhaust gas of a 78 kW diesel engine as its energy input. A thermodynamic model was developed to predict the possible electricity generation of the ORC. Using this model it was determined that the preferred working fluid for the ORC was R245ca. The calculated maximum ORC thermal efficiency was 14.3%. The net electrical power generated from the ORC was 5.36 kWe. The ORC would require no additional fuel and would not generate any additional emissions. The most cost-effective and simple means to develop a small packaged ORC system is to high volume production HVAC system components. An ORC system consisting of air conditioning system components, including a scroll expander, yielded a projected ORC efficiency of 10.7%, and a net electrical power of 4.02 kWe. The total capital cost of the ORC system was $2,140 CAD. Three engine usage scenarios were developed, with the time to payback of the initial capital cost of the ORC ranging from 12.8 to 0.58 years, depending on low or high usage.
Organic Rankine Cycle Power Generation for Energy Recovery From Air Compressors
Authors: Borshanpour Babak , Wallace James S.
Published: March 2012

The organic Rankine cycle (ORC) is a power generating technology that can enable the utilization of waste heat to generate electric power from different sources, including geothermal hot springs, other power generating technologies, and industrial applications. There is a significant technical challenge in producing financially viable ORC plants, due to the high costs associated with custom heat exchange components and turbo-machinery. In the last few years, however, packaged systems have been developed from commercially available refrigeration systems, which significantly reduce cost. The goal of this project was to evaluate the feasibility of generating electricity using the waste heat from industrial air compression equipment. A simulation program was written to model the thermodynamics of the ORC. Several potential working fluids were surveyed and ranked based on their applicability to the industrial operating conditions. In particular, refrigerant R-236fa has been determined to be the most appropriate working fluid. The decision was made by weighing its thermal properties, as well as environmental and health considerations. Two types of heat rejection technology were considered, namely water-cooling and air-cooling, with emphasis on the effect of ambient conditions on ORC performance. It is concluded that water-cooling can be used for a plant located in Ontario, Canada, with the possibility of utilizing air-cooling during the cooler seasons of the year. An installation cost of U.S. $1,300/kW is feasible, yielding a simple payback period of 6.35 years. The results of this research project encourage further work to be done on this application of waste heat recovery.
Numerical Simulations of Vertical-Axis Wind Turbine Blades
Authors: Plourde B. D. , Abraham J. P. , Mowry G. S. , Minkowycz W. J.
Published: March 2012

A recent research project has been focused on the design, manufacture, and testing of novel, vertical-axis turbines which can be directly attached to existing structures (such as communication towers) for local power generation, particularly in areas of the world where grid-connected electricity is unavailable. The proposed turbine has undergone a multitude of design stages, including the wing design, prototype fabrication, wind-tunnel testing, and manufacture. This report discusses the initial design process utilized to create the turbine wing. That process relied upon numerical simulations of the unsteady flow patterns which occur when the wing rotates. Results from the simulation were used to modify the wing design and significant improvements in performance were realized. Based on wind-tunnel tests, improvements on the order of 300% were obtained, compared to the initial design. Improvements of this magnitude have allowed the progression from prototype testing to large-scale manufacturing. The simulations allowed the implementation of novel design features such as preferentially deployed vents which allowed an increase of torque and a decrease of transverse loads. Results from the simulation were compared with experimental results obtained from a wind-tunnel test. In addition, data was extracted from an in situ test facility which was installed with wind-speed and data acquisition equipment. It was found that the results of the simulation were in close agreement with both the results from the wind tunnel and the in situ tests. The congruence gave added confidence to the veracity of the simulations.
Thermodynamic Characterization and Dynamic Simulation of a Micro Algae Air Lift Photobioreactor
Authors: Avila Adrian , Bula Antonio , Go´mez Rafael , Mendoza Jorge , Verdeza Arnaldo
Published: March 2012

Micro algae production as a source of fatty biomass that can be used to produce biofuels is a promising alternative that needs to be thoroughly evaluated. The tendency to increase production and energy content and to reduce water usage has had an impact in the development of photobioreactors, due to the versatility of this equipment to control and optimize the production parameters. This system requires an adequate scheme for monitoring and controlling the variables such as temperature, light intensity, carbon dioxide and oxygen supply, in order to guarantee the micro algae growth. This paper presents a control strategy for algae growth in an airlift photobioreactor. A thermodynamic characterization was performed and the dynamic behavior of the system is modeled for system analysis and control. A mathematical model is developed using the equations describing the process. A PID controller is set to evaluate the parameters that control algae growth. The results show that the photobioreactor presents a substantial sensitivity to room temperature changes, and this is considered as the main disturbance of the process. For the dynamic characterization a non-linear differential equations-based model was developed, and after tuning a PID controller it was found that the system was robust to changes in ambient conditions.
Low Exergy Heating and Cooling in Residential Buildings
Authors: Jochum Michael , Murugesan Gokulakrishnan , Kissock Kelly , Hallinan Kevin
Published: March 2012

Exergy is destroyed when work is degraded by friction and turbulence and when heat is transferred through finite temperature differences. Typical HVAC systems use a combination of high quality energy from combustion and electricity to overcome relatively small temperature differences between the building and the environment. It is possible to achieve the heating/cooling necessary to maintain comfort in a building without these high quality energy sources and their high potential-energy destruction. A low-exergy heating and cooling system seeks to better match the quality of energy to the loads of the building and thus to minimize exergy destruction and increase the exergetic efficiency of the building’s heating and cooling system. The method described here for low exergy building system design begins by minimizing overall heating and cooling loads using a tight, highly-insulated envelope and passive solar design strategies. Next a low-exergy heating and cooling system is designed that uses hydronic radiant heating and cooling in floors, along with high thermal mass. The large surface area of the floors enable low fluid flow rates and relatively small temperature differences to achieve heat transfer rates that would traditionally be driven by high temperature differentials and flows. The building uses a solar wall to passively drive ventilation requirements and earth tubes to condition the ventilation air. High thermal mass in the floor reduces peak loads and eliminates the need for solar thermal storage tanks. Thus, this paper begins to explore the practical limits of low-exergy design.
Development of Bio-Mass Fuel for Small Displacement Engine to Reduce CO2: Feasibility of Disposed Alcoholic Beverages as Bio-Mass Source
Authors: Kakihara Takahiro , Yanagihara Kiyoshi
Published: March 2012

This study deals with bio-ethanol distilled from disposed alcoholic beverages. Through the various experiments while using a small displacement engine which is equipped with electric fuel injection (E.F.I.) system, the feasibility of the disposed alcoholic beverages; leftover-beer is investigated as one of the bio-mass sources. Currently bio-masses are classified into the following seven bio-mass sources, livestock excreta, sewage sludge, human waste sludge, waste of food, agricultural residue, wood-based (wood chips) bio-mass and crops. In those bio-mass sources, the authors pay their attention to the amount of leftover-beer after a banquet. Our investigation clarifies that about 12 l of beer is left and disposed after a banquet of 150 people. Since beer contains 5% alcohols, 600 cc of ethanol can be obtained without fermentation process. Thus in order to obtain alcohol as a fuel, in collaboration with some hotels, leftover-beer is collected. As to a fuel, higher concentration of distilled alcoholic beverages is preferable. Therefore a new double distillation system is developed to separate water, and 85.9% bio-ethanol fuel is produced from 5% alcoholic density of leftover-beer. The ethanol evaporation characteristic of this bio-ethanol is investigated, it is equal to 98% ethanol reagent. This showed that it can be mixed with gasoline. Also, in order to confirm its performance as a fuel, the obtained ethanol is experimented with 121 cc of small displacement engine which is equipped with E.F.I. system. The results of this experiment are compared to unleaded gasoline and showed that it has the same performance of engine power, especially in case of before top dead center (B.T.D.C.) 15.0 deg.. We also calculated the volume of CO2 emission discharged in distilled ethanol under driving conditions B.T.D.C. 15.0 deg., 4000 rpm, for 1 hour. The CO2 production of distilled ethanol is 34.4 kgCO2, on the other hand, CO2 production of unleaded gasoline is 2.82 kgCO2. This result shows that the system with high energy efficiency to separate ethanol and water is desired. Furthermore, the density of acetaldehyde from exhaust gas is analyzed. An extremely low reading of 28 ppm is obtained. The results prove the effect of acetaldehyde to the human body is negligible. Finally, employing 50 cc motorcycles with our developed E.F.I. system, experiment with bio-mass ethanol is executed. The results proved the feasibility of our developed bio-ethanol can be a new low emission bio-mass source.
Modeling Heat Generation in a Lithium Ion Battery
Authors: Wu Wei , Xiao Xinran , Huang Xiaosong
Published: March 2012

This paper presents a numerical study on heat generation in a lithium-ion (LiC6/LiPF6/LiyMn2O4) battery cell. The numerical model considered multi-physics including battery kinetics, diffusion, and thermal analysis. The heat generation rate was determined by a local heat generation model. This model enables the investigation of the effects of battery parameters on different heat generation mechanisms and the overall heat generation rate in the battery. The effects of the thickness of the battery components and the size of the electrode particles at different discharge rates were evaluated. The results revealed the relationships between these parameters. A battery with a low heat generation rate and efficient battery utilization may be achieved through parameter optimization.
Design Optimization of Sustainable Off-Grid Power Systems for the Developing World
Authors: Bilton Amy , Kelley Leah , Mazzini Francesco
Published: March 2012

Electrification of remote areas in the developing world can greatly improve the health and economic standing of the population. Unfortunately, providing power to these remote areas can be expensive and determining the most economical solution is not trivial. This paper presents a method to compare the economics of different small-scale power systems for developing world. In this method, models are developed to describe the performance of power systems composed of diesel generators, batteries with photovoltaics or wind turbines, and hybrid systems. These models are coupled to an optimizer to determine the lowest cost solution that meets the desired system reliability. The reliability is expressed as Loss of Load Probability, and is computed using hourly solar and wind data. In this paper, this method is used to design a power system for a small hospital in the developing world. The results are presented for three sample locations in Honduras, Pakistan, and Uganda. Results show that the economic attractiveness of different technologies varies greatly due to local climatic conditions. The variety and soundness of the solutions found using this method show that it can aid in the design of a small-scale power system for any location in the developing world.