bluuebunny/crossref_metadata_2025 huggingface dataset:
Laser-Induced Incandescence and Smoke Point Measurements to Characterize the Sooting Propensity of Biodiesel Diffusion Flame
Authors: Tran Michael , Pham Trinh
Published: January 2011

Combustion of biodiesel is rapidly expanding around the world, mainly for its significant reduction of emissions such as soot particulates. The presence of carbonaceous soot emitted indicates a reduction in efficiency of practical combustion systems. In addition, sub-micron soot particles can have substantial impact on the environment and human health. Common emission studies of neat and blends of biodiesel and diesel fuels have been investigated using compression ignition engines and capturing soot particles in the post-combustion zone. However, soot particles produced in the primary combustion zone can greatly influence the products in the post-combustion zone. To study soot formation in the primary combustion zone, laser diagnostic is performed on a laminar diffusion wick lamp. In this paper, the sooting propensity of various blends of soybean biodiesel and Ultra Low Sulfur Diesel (ULSD) fuels are investigated using both a traditional ASTM D-1322 standard smoke lamp and modern Laser-Induced Incandescence (LII) technique. Laser excitation is achieved using a pulsed Nd: YAG laser operating at 532nm wavelength. Although ultraviolet and infrared spectra can be used, the choice of an Nd: YAG laser operating at the second harmonic wavelength is preferred because interference from excitation of polycyclic aromatic hydrocarbons (PAHs) and the C2 Swan band can be reduced. A fast-gate Intensified Charge Coupled Device (ICCD) camera and a 450nm narrow band-pass filter are used to detect the spatially resolved LII signal. The qualitative LII signal provides the soot profile of different volume mixtures of biodiesel and diesel diffusion flame. Many researches report show reduction in soot particles emitted in the exhaust when biodiesel is used as a blend in compression ignited engines. The contribution of this research is to investigate whether similar sooting characteristics can be seen in the primary combustion zone by making measurements in the proximity of the flame front. In general, the LII signals and smoke point measurements show a decrease in soot particles produced when blending ratios of 25% biodiesel – 75% diesel (by volume) are used. One limitation of using the ASTM standard wick lamp is flame instability at higher blending ratios due to the increases in carbon deposit on the wick, which reduces the fuel vaporization rate. Therefore, smoke point measurement for blending ratios above B25 is not accurate since the flame height is not stable; hence, future experiments rely on LII technique to characterize soot emission properties. In order to perform LII laser diagnostics using higher blending ratios, comparison between smoke point measurements and LII signals will be characterized in this report using lower blending ratios.
Heat Transfer in Thermocline Storage System With Filler Materials: Analytical Model
Authors: Karaki Wafaa , Van Lew Jon T. , Li Peiwen , Chan Cho Lik , Stephens Jake
Published: January 2011

Parabolic trough power systems utilizing concentrated solar energy have proven their worth as a means for generating electricity. However, one major aspect preventing the technologies widespread acceptance is the deliverability of energy beyond a narrow window during peak hours of the sun. Thermal storage is a viable option to enhance the dispatchability of the solar energy and an economically feasible option is a thermocline storage system with a low-cost filler material. Utilization of thermocline storage facilities have been studied in the past and this paper hopes to expand upon that knowledge. The heat transfer between the heat transfer fluid and filler materials are governed by two conservation of energy equations, often referred as Schumann [1] equations. We solve these two coupled partial differential equations using Laplace transformation. The initial temperature distribution can be constant, linear or exponential. This flexibility allows us to apply the model to simulate unlimited charging and discharging cycles, similar to a day-to-day operation. The analytical model is used to investigate charging and discharging processes, and energy storage capacity. In an earlier paper [2], the authors presented numerical solution of the Schumann equations using method of characteristics. Comparison between analytical and numerical results shows that they are in very good agreement.
Optimal Design of a Biogas Fuelled MCFC System Integrated With an Anaerobic Digester
Authors: Verda Vittorio , Nicolin Flavio
Published: January 2011

In this work, a biogas fuelled power generation system is considered. The system is constituted by a molten carbonate fuel cell (MCFC) coupled with a micro gas turbine for electricity generation and supplying heat to an anaerobic digester which produces biogas from urban wastes. The work starts with a time dependent model of the digester, obtained from measured data, relating the waste characteristics with the biogas mass flow rate. The thermal flux required by the digester is also related to the waste disposal. The optimal design of the MCFC system is then investigated considering both thermodynamic and economic objective functions, calculated in a proper design condition. The effects of variation in fuel quality, ambient temperature and component performances are finally analyzed.
Preliminary Results of a Measurement Station to Characterize the Wind Energy Potential at the Eastern of Mexico
Authors: Soler-Bientz Rolando , Ricalde-Cab Lifter
Published: January 2011

The evaluation of wind power systems under real field conditions is essential to predict their actual capacity to convert the energy available in the wind into electrical power contributing to develop more robust applications. Detailed studies of the wind resources play a crucial role to estimate whether electricity can be generated from the wind at a reasonable cost for a specific region, Wind data collected from meteorological stations at the standard height (usually 10m above the ground level) can give a general idea about the energy availability but to obtain more precise estimates systematic data acquisition, analysis and presentation of wind data should be carried out for heights comparable to those of modern wind turbines (typically between 30 and 120m height). This paper presents the results obtained from a wind measurement station installed to monitor the wind speed and direction at 10m and 30m heights over three years at the Yucatan Peninsula in the eastern of Mexico. This study will allow establishing the basics conditions for futures studies about the wind conditions at higher heights.
Thermal Storage Systems for District Heating Networks
Authors: Verda Vittorio , Colella Francesco
Published: January 2011

District Heating is an efficient way to provide heat to residential, tertiary and industrial users. Heat is often produced by CPH plants, usually designed to provide the base thermal load (40–50% if the maximum load) while the rest is provided by boilers. This choice is made on the basis of economic criteria, in fact the investment cost of a CHP plant is much higher than the cost of boiler, thus its use is convenient when it operates for a large number of hours. The use of storage tanks would permit to increase the annual operating hours of CHP: heat can be produced when the request is low (for instance during the night), stored and then used when the request is high. The use of boilers results partially reduced, thus the thermal load diagram is flattered. Depending on the type of CHP plant this may also affect the electricity generation. All these considerations are crucial in the free electricity market. In this paper, the use of storage systems connected to the district heating systems, is examined. A thermo fluid dynamic model of the tanks is considered in order to calculate the amount of energy actually provided, taking the real operating conditions into account. These considerations are applied to the Turin district heating system, in order to determine the impact of storage systems on the primary energy consumption required to supply heat to the users over the entire heating season.
Electric Utility Operational Cost and Emissions Management With Grid-Scale Energy Storage
Authors: Harris Chioke , Webber Michael E. , Meyers Jeremy P.
Published: January 2011

In the United States, installation of emission-free sources of power generation, such as wind and solar photovoltaics, has increased recently. Unfortunately, these generation technologies present unique challenges to utilities and grid operators because they are variable and not dispatchable. While energy storage can provide capacitance to the system and thereby make renewable power more dispatchable, storage implementation at the municipal scale is poorly understood. This paper examines future applications of energy storage to reduce costs and improve system reliability for electric utilities at the local level. The city of Austin, Texas was selected as the study area because the city has set aggressive targets of 30–35% of total electricity generation from renewable sources, primarily wind and solar photovoltaics, by 2020. For this analysis, generation assets currently used and those planned for future development by the local utility, Austin Energy, are treated in a unit commitment model using a mixed integer programming (MIP) approach. The model has been developed such that it can be provided any objective function and generation portfolio, and the results can be used by whatever stakeholder has generated those particular inputs. To best simulate operational dispatch conditions, the model includes ramp rate constraints, generator turn-on penalties, and minimum operation levels. Energy storage is included by allowing the model to assign an unconstrained asset throughout the study period, 24 hours, to whatever values will minimize the objective function. For this initial analysis, storage system efficiency, capital and marginal costs were not included, though they may significantly affect total allocated storage. Modeling results indicate that storage availability yields a reduction of as much as $600,000/day in marginal costs for the study area, based primarily on improved utilization of more efficient generating units. This result does not consider savings associated with NOx reductions. Such reductions were studied with a second objective function. While NOx reductions of approximately 9–23% were observed, these emission reductions were accompanied by significant increases in operating costs. Energy storage requirements and potential cost savings under the scenarios examined might be beneficial to researchers interested in grid-scale storage. These results can also be used to determine appropriate cost targets for storage researchers and manufacturers.
Practical Considerations for Low-Emission Thermal Power Plants
Authors: Galpin David S. , Galpin Theodore S.
Published: January 2011

Thermal power plants provide the majority of electricity used around the world and will continue to do so for some time. The goal of this paper is to provide an understanding of technology and fuels used in thermal power plants and the byproducts they create. The emphasis is on magnitudes of fuels used, emissions created and the sustainability and practicality of methods of production and control. A basic thermal power plant burns fuel to produce steam, which turns a turbine generator to produce electricity. The basic elements of thermodynamics apply to all thermal power plants: a heat source, a heat engine and a heat sink. Heat sources for thermal power plants include boilers fueled by coal, natural gas and biomass; gas turbines fueled by natural gas; and nuclear reactors fueled by uranium. Topics of discussion include the logistics involved in supplying fuels and handling their byproducts, including carbon compounds; types of heat engines utilized; methods to improve efficiency to reduce the fuel consumed; byproducts generated; and the heat sink required. The focus is on Rankine (vapor) and Brayton (gas) cycles. Although not directly affecting carbon byproducts, the heat sink used affects the heat engine efficiency and the consumption of water, a valuable resource. The types of heat sinks discussed include open-cycle water cooling, closed-cycle water cooling and air cooling. Thermal power plants provide many benefits to the electrical power system. They provide power 24 hours a day and 365 days a year, regardless of the weather. They are relatively compact, making them easier to build, operate and maintain. They also can be located close to electrical load concentrations reducing the need for transmission lines that disrupt the environment. The technologies involved in thermal power plant operation are proven effective and in use today. The challenges are to manage the fuel supply and byproduct disposal in an environmentally acceptable manner.
Energy and Exergy Assessments of a New Trigeneration System Based on Organic Rankine Cycle and Biomass Combustor
Authors: Al-Sulaiman Fahad A. , Hamdullahpur Feridun , Dincer Ibrahim
Published: January 2011

In this paper, energy and exergy analyses of a trigeneration system based on an organic Rankine cycle (ORC) and a biomass combustor are presented. This trigeneration system consists of a biomass combustor to provide heat input to the ORC, an ORC for power production, a single-effect absorption chiller for cooling process and a heat exchanger for heating process. The system is designed to produce around 500 kW of electricity. In this study, four cases are considered, namely, electrical-power, cooling-cogeneration, heating-cogeneration and trigeneration cases. The effects of changing ORC pump inlet temperature and turbine inlet pressure on different key parameters have been examined to evaluate the performance of the trigeneration system. These parameters are energy and exergy efficiencies, electrical to cooling ratio and electrical to heating ratio. Moreover, exergy destruction analysis is presented to show the main sources of exergy destruction and the contribution of each source to the exergy destruction. The study shows that there are significant improvements in energy and exergy efficiencies when trigeneration is used as compared to electrical power. The results show that the maximum efficiencies for the cases considered in this study are as follows: 14.0% for electrical power, 17.0% for cooling cogeneration, 87.0% for heating cogeneration and 89.0% for trigeneration. On other hand, the maximum exergy efficiency of the ORC is 13.0% while the maximum exergy efficiency of the trigeneration system is 28.0%. In addition, this study reveals that the main sources of exergy destruction are the biomass combustor and ORC evaporator.
Configuration Optimization of a Photovoltaic Power Plant in Relation to Cost and Performance
Authors: Lee Kenneth K. , Moore Jared T.
Published: January 2011

The purpose of this paper is to examine the economic benefits of single-axis tracking photovoltaic (PV) power plants for a variety of locations with varying solar resources. Although the photovoltaic industry has been around for decades, the industry has changed dramatically in the past few years. A confluence of overproduction of panels and an economic recession have caused a precipitous drop in panel prices. Additionally, as tracking systems have matured, they have become more acceptable — technically and economically. With all these changes, it is not clear today if and where tracking is appropriate. This paper is to gauge the difference between a tracking and non-tracking configuration of a PV plant. For the purpose of this study, a net 20 MW alternating current (AC) PV plant was assumed to be developed at three different locations: California, Colorado, and New Jersey. The same panel of a moderate efficiency was picked and was used at each site. While a panel is not usually decided before development, a panel of typical characteristics was chosen so that prospective panels’ costs and efficiency could be assessed concerning tracking using a qualitative analysis. Levelized cost of energy (LCOE) of each site was determined using the Life-Cycle Cost Analysis methodology. For fixed mounting structures, the tilt of the panel was optimized based on the respective weather conditions to maximize production. After the tilt was decided, an economic sensitivity study taking shading and land prices into account was used to find the most economical spacing between mounting structures. For tracking, horizontal single axis tracking was assumed, and spacing was optimized as described above. The results of the study show that the benefit of tracking increases with the strength of the solar resource. In Newark, New Jersey, tracking raised the LCOE. In Daggett, California, tracking lowered the LCOE. In Boulder Colorado, the difference in LCOE was not appreciable. The study also showed that the most economical fixed PV power plant used less land on a capacity basis at each site. However, tracking plants, regardless of location or solar resources, produced more energy (kWh) per acre of land and could be described as more efficient on a land use basis.
Comparison of Different Time Series Methods for Short-Term Forecasting of Wind Power Production
Authors: Li Gong , Shi Jing
Published: January 2011

Reliable short-term predictions of the wind power production are critical for both wind farm operations and power system management, where the time scales can vary in the order of several seconds, minutes, hours and days. This comprehensive study mainly aims to quantitatively evaluate and compare the performances of different Box & Jenkins models and backpropagation (BP) neural networks in forecasting the wind power production one-hour ahead. The data employed is the hourly power outputs of an N.E.G. Micon 900-kilowatt wind turbine, which is installed to the east of Valley City, North Dakota. For each type of Box & Jenkins models tested, the model parameters are estimated to determine the corresponding optimal models. For BP network models, different input layer sizes, hidden layer sizes, and learning rates are examined. The evaluation metrics are mean absolute error and root mean squared error. Besides, the persistence model is also employed for purpose of comparison. The results show that in general both best performing Box & Jenkins and BP models can provide better forecasts than the persistence model, while the difference between the Box & Jenkins and BP models is actually insignificant.
Thermoeconomic Study of a Small Parabolic Trough Solar Plant
Authors: Duran M. D. , Rinco´n E. A. , Sa´nchez M.
Published: January 2011

This work describes the thermoeconomic study of an integrated combined cycle parabolic trough power plant. The parabolic trough plant will economize boiler activity, and thus the thermoeconomic optimization of the configuration of the boiler, including the parabolic trough plant, will be achieved. The objective is to obtain the optimum design parameters for the boiler and the size of the parabolic field. The proposal is to apply the methodology employed by Duran [1] and Valde´s et. al. [2], but with the inclusion of the parabolic trough plant into the optimization problem. It is important to point out that the optimization model be applied to a single pressure level configuration. For future works, it is proposed that the same model be applied to different configurations of integrated combined cycle solar power plants. As a result the optimum thermoeconomic design will be obtained for a parabolic trough plant used to economize the HRSG.
Simulation by Means Computational Fluids Dynamics of the Mixing Process Air-Natural Gas in a Turbocharger Diesel Engine
Authors: Bermejo Fabio A. , Corredor Lesme A.
Published: January 2011

Diesel buses of public transportation in the main cities of Colombia are formed by turbocharger engines, such machines could operate in dual Diesel-NG way using the gaseous fuel as main energy source and the liquid fuel to pilot ignition of the air-NG mixture previously formed. This research is centered on the studies about formation process of the mixture in the intake system in a turbocharger dual engine. In this study the transport equations are established, it is associated to the fluids which enter to the intake engine during a period of engine operation. This model is simulated by means of CFD tools, using an electronic injector to provide natural gas. Also it is considered the fluidynamic behavior of mixture. Finally an experimental design applied to the simulations is made with the goal of optimize operational conditions of the injector that allow to get the most homogeneous mixture on the inlet runner to one of the cylinders engine. This mixture was obtained injecting natural gas at a pressure of 10 bars and placing the injector as close to the intake manifold.
Integrating Renewable Energy Technologies to Reduce Large Ship Fuel Consumption
Authors: Gully Benjamin H. , Webber Michael E. , Seepersad Carolyn C. , Thompson Richard C.
Published: January 2011

Fuel costs, which are the single most important driver of marginal costs for marine transportation, account for almost 50% of total voyage costs for typical configurations and operational modes. Hence, there has developed a desire among operators and manufacturers of all classes of ships to embrace innovative ways to reduce the demand for fuels. The luxury yacht segment presents an attractive market for investigating and assessing the impacts of fuel-saving technologies because the large ships benefit from the fuel savings, have more flexible performance requirements and have owners who are more likely to embrace the required premiums for experimental technologies. This report analyzes the effects of fitting such a yacht with a sail system, a solar panel system, and an energy storage system (ESS). Integrating a sail system to reduce propulsion loads provides significant benefit with respect to fuel economy. In contrast, the total amount of power provided by the solar panel system provides very little benefit, even when extensive deck paneling is used and panels are fit to rigid wing sails. Utilizing an ESS in the same manner as with a terrestrial hybrid vehicle to manipulate load distribution provides insignificant benefit for fuel consumption reduction, but seems to present opportunities for emissions reduction, which has played an increasingly important role in marine environmental concerns.
A Roadmap for Rural Electrification in Developing Countries Using MiViPPs (Microutility Virtual Power Plants)
Authors: Pandey Swati , Chauhan Manish
Published: January 2011

In this paper we present a road-map for rural electrification in developing countries by means of Renewable Energy based MiViPPs (Microutility virtual power plants). First and foremost a feasibility and viability analysis of the various upcoming and alternative renewable energy options is performed with respect to rural environmental constraints and demands. Renewable Energy based DDG’s (Decentralized Distributed Generation Units) offer the potential for affordable, clean electricity with minimal losses and effective maintenance and local cost recovery. But Independent DDG projects are fraught with their own issues mainly stemming from the unreliable and intermittent nature of the generated power and high costs. We propose an alternative approach to rural electrification which involves off grid DDG units operated at the local level taking advantage of feasible renewable energy technologies, which can effectively serve rural areas and reduce the urgency of costly grid extension. In MIVIPP model, a multitude of decentralized units (renewable energy based units and a non-renewable energy based unit for last mile backup) are centrally controlled and managed as part of an interconnected network, resulting into a virtual power plant that can be operated as a distributed power plant large enough to reliably serve all the local electricity demands in a cost effective manner. Finally, by a set of simulation results we establish how an automated MIVIPP (based on an Intelligent Auto Control System) effectively addresses all the issues pertaining to Dispersed DDG units by leveraging the scalability achieved by mutually augmenting the supplies from different Renewable Energy Based DDG units.
Designing of Solar Water Bath Heater for Gas Pressure Reducing Station in of 150,000 Nm3/h Capacity in Assaluyeh Region in Iran
Authors: Dalir Fatemeh , Assadi Morteza Khalaji
Published: January 2011

This paper proposes the design of a solar water bath heater for Central Power Plant in Assaluyeh region in south of Iran with the latitude of 27 °N. This heater uses flat plate solar collectors in an open circuit system. Solar intensity, absorbed radiation and ambient temperature are the regional parameters which are known to the designer. The temperature of the bath of water which is the outlet collector temperature (70 °C) belongs to the known parameters in the mentioned station. Flow rate, heat loss factor, the inlet temperature of the collector and the area which is the most important factor to evaluate the economical issues of the system are calculated with modeling the water bath with a shell and tube heat exchanger. The solar water bath heater is then simulated with TRNSYS software. The obtained results are in good agreement with analytical solution based on Duffie and Beckman method.
The Environmental and Economic Impact of IGCC in China, With Comparison to Alternative Options
Authors: Hu Zupan , Pratt Joseph W.
Published: January 2011

The goal of this study is to evaluate the economic and environmental performance of power plants based on integrated gasification combined cycle (IGCC) technology, and to compare it with currently relevant renewable and nuclear power generation options in China, until the year 2020. First, electricity demand is predicted, based on up-to-date policies made by Chinese government organizations. From this, a business as usual (BAU) study, in which coal-fired power plant technology is assumed to be unchanged from 2010 to 2020, is carried out as a reference. Different scenarios of IGCC technology adoption are then studied using a newly developed model, and the result show, for example, that there could be 10.05 billion tons of CO2 emission avoided from 2010 to 2020 if 50% of newly built coal-fired plants are based on IGCC technology with CO2 capture. When compared with other options, the cost of avoided CO2 emissions in this scenario is more expensive than hydroelectric, nuclear, and wind, but cheaper than solar (thermal and photovoltaic). The results also show that IGCC, although more expensive, could still be important in China’s coal-dominated electricity industry.
Heat Recovery From a Microturbine System
Authors: Bailey Caitlin J. , Wallace James S.
Published: January 2011

Previous study of a microturbine-based combined heat, cooling and power system installed on a university campus showed that the turbine exhaust energy must be fully utilized for the economics to be favorable. The system studied combined four 60 kW microturbines with a 110 ton absorption chiller that recovers exhaust waste heat. The chiller, which has the capability of providing either chilled water for cooling or hot water for heating depending on seasonal needs, was found to be mismatched to the local heating and cooling needs. This paper describes the design of an exhaust heat exchanger that will be integrated into the campus steam plant for more efficient utilization of the microturbine waste heat. The hot water generated will be used during heating season to heat a nearby building with a hydronic heating system. This will reduce boiler fuel costs, since this heating load would otherwise be met from a steam heating station. At other times of the year, the hot water generated will be used to preheat condensate return for the campus steam plant, which has a year-round steam demand.
Numerical Study on the Thermal Interaction of Gas-Particle Transport for a Vortex Flow Solar Reactor
Authors: Ozalp Nesrin , JayaKrishna D.
Published: January 2011

Solar reactors, by nature of their high temperature, are nearly experimentally inaccessible. Most instruments capable of measuring fluid flow cannot survive the harsh temperatures inside the reactor. As such, computational fluid dynamics (CFD) has been relied on to provide insight into the flow within the reactor. Because of the size of the computing resources necessary to properly account for all of the physical mechanisms within the solar reactor, the current state of numerical simulations only provide a limited level of insight. The present study provides an analysis of flow behavior and thermal interaction of gas-particle flow for a directly irradiated vortex flow solar reactor. The thermal hydraulics between gas flow and particle has been considered by two way coupled Euler-Lagrange approach. A two band discrete ordinate (DO) model has been considered to solve radiative transport between walls and entrained particles. The effect of main flow, secondary flow, particle loading, particle diameter and residence time are studied to analyze flow physics and heat transfer. Results are presented in terms of static temperature contours, temperature distribution along the center line of the cavity, path lines and particle temperature. It is observed that with the increase in main flow, secondary flow and particle diameter average outlet temperature of the fluid increases, and with the increase in particle loading the outlet temperature decreases. The particle exit temperature is observed to increase with the increase in residence time.
Alternatives to Electricity for GW-Scale Transmission and Firming Storage for Diverse, Stranded Renewables: Hydrogen and Ammonia
Authors: Leighty William C. , Holbrook John H. , Blencoe James G.
Published: January 2011

COP15, Copenhagen, December 09, failed partly for lack of a credible, comprehensive vision for how we may, and must soon, “run the world on renewables”. We cannot, and should not try to, accomplish this entirely with electricity transmission. The world’s richest renewable energy (RE) resources — of large geographic extent and high intensity — are stranded: far from end-users with inadequate or nonexistent gathering and transmission systems to deliver the energy. Electricity energy storage cannot affordably firm large, intermittent renewables at annual scale, while gaseous hydrogen (GH2) and anhydrous ammonia (NH3) fuels can: GH2 in large solution-mined salt caverns, NH3 in surface tanks, interconnected via underground pipelines in RE systems for gathering, transmission, distribution, and end use. Thus, we need to think beyond electricity as we plan new “transmission” systems for bringing large, stranded RE resources to distant markets as annually-firm C-free energy, to empower subsequent efforts to COP15. Recent press has extolled the global RE vision, but without adequate attention to the diverse transmission and storage systems required for achievement. [21] At GW scale, renewable-source electricity from diverse sources can be converted to hydrogen and byproduct oxygen, and/or to NH3, pipelined underground to load centers for use as vehicle fuel and combined-heat-and-power generation on the wholesale or retail side of the customers’ meters. The ICE, CT, and fuel cell operate very efficiently on GH2 and NH3 fuels. USA has extensive extant NH3 pipeline and tank storage infrastructure.
Heliostat Canting and Focusing Methods: An Overview and Comparison
Authors: Yellowhair Julius , Ho Clifford K.
Published: January 2011

A central receiver power tower system consists of a field of heliostats that focus the sunlight onto the receiver on the tower. Heliostats typically consist of an array of mirror facets that track the sun throughout the day. To obtain the optimal concentrated solar flux on the receiver, the individual heliostat facets must be properly canted and focused. Several different methods have been used in the past for facet canting and focusing. These demonstrated methods and some new alignment concepts are under consideration for development and alignment of the 218 heliostats at the Sandia National Laboratories National Solar Thermal Test Facility in Albuquerque, NM. In this paper, we provide an overview and comparison of the different methods. The methods we consider are the gauge blocks, inclinometers, photogrammetry, fringe reflection, imaging with theoretical image overlays, laser beam projections, camera look-back, and target reflection methods. The advantages and disadvantages of each alignment method are identified based on several prescribed criteria for aligning the heliostats. Recommendations regarding the alignment method’s potential for efficiently and accurately aligning heliostat fields are provided.
Development of an Hourly Optimization Tool for Renewable Energy Systems
Authors: Lee Christine , Walker Andy , Krarti Moncef
Published: January 2011

An hourly optimization tool is developed to select and size renewable energy (RE) systems to meet the energy needs for various federal facilities. The optimization is based on life cost analysis of various RE technologies including wind and PV systems. The developed hourly optimization tool is used to evaluate the cost-effectiveness of RE technologies using complex energy and demand charges such time-of-use (TOU) rates. The paper compares results obtained using hourly analysis instead of annual based calculations to optimize the sizing of RE systems for residential, commercial, and industrial facilities in three representative US climates.
Simulation of Indoor Air Flow Fields in Buildings With Large Interior Spaces With Stratified Air Conditioning and Perforated Side Wall Diffusers
Authors: Wei Bing , Zhang Li
Published: January 2011

The energy consumption of AC (air conditioning) systems in large buildings is normally higher than the energy consumption in smaller buildings, and its indoor air flow field is also more complex than that in small building. To study the air flow mode and the indoor air flow fields in large spaces is of great significance to the energy conservation of AC systems and thermal comfort of the occupants. This paper presents an example using a large building that uses stratified air conditioning delivered through the linear slot sidewall diffusers and perforated sidewall diffusers. Using CFD simulation methods, three air flow field situations were simulated: (1) total air volume supplied from linear slot diffusers located in the middle of a side wall, (2) 50% flow through the linear slot diffusers the remainder supplied through the perforated sidewall diffusers, (3) 30% of the volume supplied with linear slot diffusers, 70% supplied through the perforated sidewall diffusers. The simulated results show that the third airflow mode is the optimal one for the three modes, which is good for achieving energy conservation and a comfortable building thermal environment in buildings with large spacial areas.
Reducing Energy Demand in Commercial Buildings: Balancing Convection and Radiant Cooling
Authors: Chusak Lee , Harris Andrew , Agarwal Ramesh
Published: January 2011

Using Computational Fluid Dynamics (CFD) software, three different cooling systems used in contemporary office environments are modeled to compare energy consumption and thermal comfort levels. Incorporating convection and radiation technologies, full-scale models of an office room compare arrangements for (a) an all-air overhead system (mixing ventilation), (b) an all-air raised floor system (displacement ventilation), and (c) a combined air and hydronic radiant system (displacement ventilation with a chilled ceiling). The computational domain for each model consists of one isothermal wall (simulating an exterior wall of the room) and adiabatic conditions for the remaining walls, floor, and ceiling (simulating interior walls of the room). Two sets of computations were conducted. The first set of computations utilized a constant temperature isothermal exterior wall, while the second set utilized an isothermal wall that changed temperatures as a function of time simulating the temperature changes on the exterior wall of a building throughout a 24 hour period. Results show superior thermal comfort levels as well as substantial energy savings can be accrued using the displacement ventilation, especially the displacement ventilation with a chilled ceiling over the conventional mixing ventilation system.
Western Wind and Solar Integration Study Hydropower Analysis: Benefits of Hydropower in Large-Scale Integration of Renewables in the Western United States
Authors: Pete Carson M. , Acker Thomas L. , Jordan Gary , Harpman David A.
Published: January 2011

NREL and research partner GE are conducting the Western Wind and Solar Integration Study (WWSIS) in order to provide insight into the costs and operational impacts caused by the variability and uncertainty of wind, photovoltaic, and concentrated solar power employed to serve up to 35% of the load energy in the WestConnect region (Arizona, Colorado, Nevada, New Mexico, and Wyoming). The heart of the WWSIS is an hourly cost production simulation of the balancing areas in the study footprint using GE’s Multi-Area Production Simulation Model (MAPS). The estimated 2017 load being served is 60 GW, with up to 30 GW of wind power and 4 GW of existing hydropower. Because hydropower generators are inherently flexible and often combined with reservoir storage, they play an important role in balancing load with generation. However, these hydropower facilities serve multiple higher priority functions that constrain their use for system balancing. Through a series of comparisons of the MAPS simulations, it was possible to deduce the value of hydropower as an essential balancing resource. Several case comparisons were performed demonstrating the potential benefits of hydro and to ascertain if the modeled data was within the defined hydro parameters and constraints. The results, methodologies, and conclusions of these comparisons are discussed, including how the hydro system is affected by the wind power for different wind forecasts and penetration levels, identifying the magnitude and character of change in generation pattern at each of the selected hydro facilities. Results from this study will focus on the appropriate benefits that hydropower can provide as a balancing resource including adding value to wind and solar and reducing system operating costs to nearly one billion dollars when offsetting more expensive generation systems as large penetration levels of renewable, especially wind power, are introduced to the grid system.
Construction and Implementation of the Off-Grid Zero Emissions Building
Authors: Kramer Justin , Greska Brenton , Krothapalli Anjaneyulu
Published: January 2011

This paper deals with the construction and implementation of the Off-Grid Zero Emissions Building (OGZEB), a project undertaken by the Energy Sustainability Center (ESC), formally the Sustainable Energy Science and Engineering Center (SESEC), at the Florida State University (FSU). The project involves the design, construction and operation of a completely solar-powered building that achieves LEED-NC (Leadership in Energy and Environment Design-New Construction) platinum certification. The 1064 square foot building is partitioned such that 800 square feet is a two bedroom, graduate student style flat with the remaining 264 square feet serving as office space. This arrangement allows the building to serve as an energy efficient model for campus designers in student living and office space. The building also serves as a prototype for developing and implementing cutting edge, alternative energy technologies in both residential and commercial settings. For example, hydrogen is used extensively in meeting the energy needs of the OGZEB. In lieu of high efficiency batteries, the excess electricity produced by the buildings photovoltaic (PV) panels is used to generate hydrogen via water electrolysis for long term energy storage. The hydrogen is stored on-site until needed for either generating electricity in a Proton Exchange Membrane (PEM) fuel cell stack or combusted in natural gas appliances that have been modified for hydrogen use. The use of hydrogen in modified natural gas appliances, such as an on-demand hot water heater and cook top, is unique to the OGZEB. This paper discusses the problems and solutions that arose during construction and includes detailed schematics of the OGZEBs energy system.
Solute Ion Coulomb Force Monopole Motor and Solute Ion Linear Alignment Propulsion
Authors: Fresco Anthony N.
Published: January 2011

Capacitive deionization relies on carbon aerogel or nanofoam having a surface area of 400 square meters/ gram to attract sodium and chlorine ions to the cathode and anode respectively by applying a voltage of about 1.5 VDC across the anode and cathode. By first physically isolating at least two anodes and two cathodes during charge accumulation, at least two positive monopoles and two negative monopoles are created. Positive/negative monopoles are formed by the enclosure of the cathodes/anodes by an electrically conductive material surrounding the sodium/chlorine ions. At least five or six like charged monopoles are created. At least four of the like charged monopoles (all negative or all positive) can be arranged on a disc. At least one stationary monopole of the same charge is placed adjacent to the disc and positioned so that a repulsive electric field is formed between the stationary monopole and at least one of the monopoles positioned on the disc so that the disc is then forced to rotate a shaft at the center of the disc. The Coulomb force between the monopoles is given by Coulomb’s Law, i.e., F=(k/ε)[(q1)(q2)/(r2)](1) where k = 9E+09 Newtons-meter2/coul2, q1 and q2 are the charge in coulombs, r is the distance between the charges in meters and ε = 75–81 dielectric constant assuming water between the charges (more likely air having ε = 1). Only a very small amount of charge in each monopole is required, i.e., 10 millicoulombs, (less than a milligram) to provide a force of about 44,000 Newtons (almost 10,000 lbs) if monopoles are separated by 0.5 meters (assuming this equation for Coulomb’s Law for this application is directly applicable without modification-this may not be the case). (For air, the force would be multiplied by 75–81). In a related approach, solute ions are accelerated by an electrostatic field from solute ions collected on electrodes +,-. Using an orthogonal electric field, partition electrodes are closed to capture like charged ions. Polarity is reversed via a transverse (longitudinal) electric field. Linear alignment of ions results in vector alignment of Coulomb forces to create an ion jet for propulsion or particle acceleration. The result is ionic marine propulsion and a possible ionic jet engine that obtains propulsion energy from Coulomb repulsion forces of homopolar separated charge. No combustion or jet fuel is required. Details are available in WO 2008/024927 A2 Ref. [1].
Modeling On/Off-Design Performance of Solar Tower Plants Using Saturated Steam
Authors: Colzi F. , Petrucci S. , Manzolini G. , Chacartegui R. , Silva P. , Campanari S. , Sa´nchez D.
Published: January 2011

This works presents a model for the performance prediction of concentrating solar tower plants using saturated live steam at on and off-design. For solar tower plants, the most important and critical element is the steam generator that, in this model, is supposed to produce saturated steam. The solar receiver is thus assumed to comprise several panels, each one of which is formed by a number of pipes. Given some boundary and initial conditions, heat and mass balances for the plant at any rated conditions can be obtained. Off-design operation is then defined by a modified map of the radiative heat flow onto the panels, though other operating conditions featuring new ambient conditions or abnormal operation of the plant can be simulated as well. As a result, a new set of heat and mass balances and performance data — efficiency, steam generation, live steam pressure and temperature, bleed pressures — are obtained. The developed model demonstrates its functionality during the design process in three ways. On one hand it allows to calculate and optimize the performance of the plant at rated conditions, developing a sensitivity analysis of the parameters involved. On the other hand, various off-design conditions can be studied and, consequently, it is possible to carry out a long term — for instance yearly — thermodynamic and economical analysis. Finally, it allows detecting undesirable operating conditions of one or more components that could eventually lead to a not admissible operation of the plant: for example a too high vapor fraction in the steam generator, a too low deaerator pressure, cavitation of pumps or other situations that are not appropriate for the steam turbine.
Implementation of Solar Thermal Driven Absorption Cooling in the Southeast
Authors: Smith Stephen M.
Published: January 2011

A 35,000 ft2 [3,251 m2] Creative Arts instruction building is being constructed on the campus of Haywood Community College in Clyde, NC (∼25 miles [40 km] west of Asheville). The building’s HVAC system consists of a solar absorption chiller, two parallel back-up electric chillers, and radiant floor heating with condensing boiler back-up. Hot water is to be heated by 117 solar thermal panels with thermal energy storage in a 12,000 gallon [45,000 liters] insulated tank and service to both the absorption chiller and the radiant under-floor heating system. Peak cooling loads and unfavorable solar conditions are to be handled by parallel electric chillers, operated in sequence to achieve maximum performance. Emergency radiant under-floor heating hot water back-up is to be handled by gas-fired condensing boilers in the event of unavailable solar heated hot water. This paper will examine the extensive modeling process required of the system as performed in EnergyPlus, how preliminary modeling results influenced the control and design strategy, the annual behavior of the system and the importance of controllability.
Probabilistic Energy ROI Models: Carbon, Energy, and Dollars
Authors: Hill Davion M.
Published: January 2011

A renewable or “clean” energy system pays back the user in three ways. First, it typically avoids the use of hydrocarbon fuel, so for every kilowatt-hour or BTU that it produces it displaces or avoids a quantity of CO2 emission due to combustion of hydrocarbon. Second, the system requires an energy investment during its manufacture, so the embodied energy is paid back over its life cycle, and this aspect of renewable energy systems is often analyzed in standardized life cycle analyses. Third, the system represents a financial investment that should be preferably paid back before the end of the system life in order for the investment to be profitable. Deterministic assessments may inaccurately assess variables that can affect the ROI in any of these three categories, such as resource availability, equipment reliability or failure, and efficiency factors. Probabilistic modeling, on the other hand, can account for some of this uncertainty and reflect the uncertainty in the output. Use of this modeling technique will be demonstrated via examples to show how feasibility or ROI projections can be augmented with the use of probabilistic models.