bluuebunny/crossref_metadata_2025 huggingface dataset:
Variable Air Volume System Application in Museums
Authors: Wang Zhan , Zheng Bin , Xu Wenlong , Wang Gang , Liu Mingsheng
Published: February 2009

Relative humidity and temperature control is key in museums, galleries, libraries and archives. Normally constant volume (CV) air handling units (AHUs) with reheat coils are applied in these buildings. Setting a low supply air temperature limits the highest humidity level; however, reheat coils have to be used to maintain space temperature due to constant supply airflow. As a result, simultaneous heating and cooling exists with excessive energy consumption. It is well known that variable air volume (VAV) technologies can reduce simultaneous heating and cooling as well as fan power. This paper presents the detail VAV system retrofit for the existing CV system, control sequence development and system performance evaluation in a museum facility at Omaha, Nebraska. Variable Frequency Drives (VFDs) were installed for the supply fan on the AHUs. Space humidity and temperature, heating and cooling energy consumption, and fan power were measured. The measurements showed that the space humidity and temperature was maintained within the required range under VAV operation while the reheat consumption was reduced by up to 85% and the fan power consumption was reduced by 90% under partial cooling loads.
Study on Operating Condition in Solar-Absorption Refrigerating System in Summer
Authors: Gao Yuefen , Shi Guohua , Wang Songling
Published: February 2009

A solar-absorption refrigerating system using the solar energy as the driving power is an energy efficiency system, which is also friendly to the environment. However, as the solar radiation varies with the season, the day and night and the climate, the solar energy supplying to the system is unsteady, which affects the security and the stability of the system. Here a typical solar-absorption refrigerating system is put forward to. Then the operating conditions in summer and their operating performance are discussed. Different operating modes are chosen according to the cooling loads and the weather. Automatic control system is used to keep the whole system operating steadily. Finally a survey is carried out. The operating record indicates that it is reasonable to adopt different operating mode in different case. This will provide the reference for the design and operation management of the solar-absorption refrigerating system.
Tin as a Possible Candidate for Solar Thermochemical Redox Process for Hydrogen Production
Authors: Vishnevetsky Irina , Epstein Michael
Published: February 2009

The feasibility to produce hydrogen in the Sn-H2O/SnO2-C thermochemical water splitting redox process depends mainly on the efficiency of the tin hydrolysis step which has not been studied adequately so far, whereas the carboreduction step was investigated because of the industrial production of tin from its mineral casseterite using charcoal or anthracite as reducing agents. The present work deals with the hydrolysis process of different kinds of tin powders at different experimental conditions at moderate temperature range of 180–620°C. In spite of the fact that the rate of hydrogen production is lower compared to other metals e.g. zinc, at the same reactor temperature, high conversion and hydrogen yield were obtained in a controllable reaction. Consequently, tin can be a promising candidate considering the advantage of significant lower temperatures required for the solar carboreduction of its oxide.
Improve Thermal Comfort in Concrete Buildings by Using Phase Change Material
Authors: Castello´n C. , Medrano M. , Roca J. , Fontanals G. , Cabeza L. F.
Published: February 2009

Phase Change Materials (PCMs) have been considered for thermal storage in buildings since 1980’s. With the advent of PCM implemented in gypsum board, plaster, concrete or other wall covering material, thermal storage can be part of the building structure even for light weight buildings. The new techniques of microencapsulation opened many possibilities in buildings applications. An innovative concrete with PCM was developed using a commercial microencapsulated PCM, with a melting point of 26°C and a phase change enthalpy of 110 kJ/kg. The first experiment was the inclusion of a microencapsulated PCM in concrete and the construction of a small room-sized cubicle with this new PCM-concrete. A second cubicle with the exact same characteristics and orientation, but built with standard concrete, was located next to the first one as the reference case. In 2005 and 2006 the behaviour of such cubicles was tested. Later on, a Trombe wall was added to the cubicles to investigate its influence during autumn and winter. The increase of the numbers of hours at which the cubicle with PCM is within the comfort zone defined by ASHRAE with respect to the cubicle without PCM is given.
Zero Energy Houses: Geoexchange, Solar CHP, and Low Energy Building Approach
Authors: Platell Peter , Dudzik Dennis A.
Published: February 2009

On March 29, 2006, the World Business Council for Sustainable Development announced in Geneva, Switzerland, that it is forming an alliance of leading global companies to determine how to design and construct buildings to use zero energy from external power grids, be carbon neutral, and be built and operated at fair market values. This paper is a contribution to the many possible Zero Energy House (ZEH) solutions that deserve further attention. The geoexchange, solar thermal combined heat and power (CHP), and low exergy building approach to ZEH is based on select R&D projects that, together, imply several important synergies. Not using “overqualified” energy in the house (i.e., energy quality, or exergy) is a significant step toward realizing a cost-effective ZEH. Most of the energy conversion and energy storage can be obtained through the appropriate use of purely renewable solar energy. However, a fuel reserve is needed to assure all of the building’s energy needs are met 24 hours a day, 365 days a year. The future ZEH implies the production of this fuel, potentially as hydrogen or alcohol, by using CO2 plus water synthesis, powered by solar heat from concentrating solar power (CSP).
Cost Optimization of Net-Zero Energy House
Authors: Mertz George A. , Raffio Gregory S. , Kissock Kelly
Published: February 2009

Environmental and resource limitations provide increased motivation for design of net-zero energy or net-zero CO2 buildings. The optimum building design will have the lowest lifecycle cost. This paper describes a method of performing and comparing lifecycle costs for standard, CO2-neutral and net-zero energy buildings. Costs of source energy are calculated based on the cost of photovoltaic systems, tradable renewable certificates, CO2 credits and conventional energy. Building energy simulation is used to determine building energy use. A case study is conducted on a proposed net-zero energy house. The paper identifies the least-cost net-zero energy house, the least-cost CO2 neutral house, and the overall least-cost house. The methodology can be generalized to different climates and buildings. The method and results may be of interest to builders, developers, city planners, or organizations managing multiple buildings.
A Rotary Receiver-Reactor for the Solar Thermal Dissociation of Zinc Oxide
Authors: Schunk L. O. , Haeberling P. , Wepf S. , Wuillemin D. , Meier A. , Steinfeld A.
Published: February 2009

An improved engineering design of a solar chemical reactor for the thermal dissociation of ZnO at above 2000 K is presented. It features a rotating cavity-receiver lined with ZnO particles that are held by centrifugal force. With this arrangement, ZnO is directly exposed to concentrated solar radiation and serves simultaneously the functions of radiant absorber, chemical reactant, and thermal insulator. The multilayer cavity is made of sintered ZnO tiles placed on top of a porous 80%Al2O3-20%SiO2 insulation and reinforced by a 95%Al2O3-5%Y2O3 ceramic matrix composite, providing mechanical, chemical, and thermal stability and a diffusion barrier for product gases. 3D CFD was employed to determine the optimal flow configuration for an aerodynamic protection of the quartz window against condensable Zn(g). Experimentation was carried out at PSI’s high flux solar simulator with a 10 kW reactor prototype subjected to mean radiative heat fluxes over the aperture exceeding 3000 suns (peak 5880 suns). The reactor was operated in a transient ablation mode with semi-batch feed cycles of ZnO particles, characterized by a rate of heat transfer — predominantly by radiation — to the layer of ZnO particles undergoing endothermic dissociation that proceeded faster than the rate of heat transfer — predominantly by conduction — through the cavity walls.
Targeting Residential Energy Assistance
Authors: Raffio Gregory , Isambert Ovelio , Mertz George , Schreier Charlie , Kissock Kelly
Published: February 2009

This paper describes a four-step method to analyze the utility bills and weather data from multiple residences to target buildings for specific energy conservation retrofits. The method is also useful for focusing energy assessments on the most promising opportunities. The first step of the method is to create a three-parameter changepoint regression model of energy use versus weather for each building and fuel type. The three model parameters represent weather independent energy use, the building heating or cooling coefficient and the building balance-point temperature. The second step is to drive the models using typical TMY2 weather data to determine Normalized Annual Consumption (NAC) for each fuel type. The third step is to create a sliding NAC with each set of 12 sequential months of utility data. The final step is to benchmark the NACs and coefficients of multiple buildings to identify average, best and worst energy performers, and how the performance of each building has changed over time. The method identifies billing errors, normalizes energy use for changing weather, prioritizes sites for specific energy-efficiency retrofits and tracks weather-normalized changes in energy use. The principle differences between this method and previously defined ones are that this method seeks to use inverse modeling proactively to identify energy saving opportunities rather than retroactively to measure energy savings, it tracks changes in building performance using sliding analysis, and it uses comparisons between multiple buildings to extract additional information. This paper describes the method, then demonstrates the method through a case study of about 300 low-income residences. After applying the method, targeted buildings were visited to determine the accuracy of the method at identifying energy efficiency opportunities. The case study shows that over 80% of the targeted buildings presented at least one of the expected problems from each type of retrofit.
Probabilistic Design and Analysis for Robust Design of Advanced Thermoelectric Conversion Systems
Authors: Hendricks Terry J. , Karri Naveen K.
Published: February 2009

Recent research investigated the impacts of single- and multi-variable stochasticity on optimum thermoelectric (TE) system design for automotive and industrial energy recovery because many critical design and environmental parameters used in design optimization can be randomly variable. Analysis tools and techniques have been developed to investigate a variety of stochastic behaviors in critical input parameters, including Gaussian, Log-Normal, Weibull, Gamma, or any type of user-defined probability distribution. Recent accomplishments discussed herein show that: 1) Gaussian input probability distributions can create non-Gaussian outcome distributions for optimum TE areas, required cold-side mass flow rates, and expected power generation; 2) optimum deterministically-derived designs (TE areas and cold-side mass flow rates) should be significantly modified in response to stochastically variable inputs; and 3) outcome parameter standard deviations can be significant and magnified relative to input parameter standard deviations. Multiple variable stochastic inputs tend to significantly increase the output design parameter variability (i.e., standard deviations). Interactive effects of multiple stochastic input parameters have demonstrated that reductions of optimum TE areas by 9–10% relative to deterministic optimum values was warranted in key stochastic analysis cases. Reductions in required cold-side mass flow rates may also be justified. Optimum system power output also was characterized by relatively high variability (i.e., standard deviation) resulting from stochastic input effects on the TE design optimization process. This is an important consideration when integrating the overall power system design with power management electronics and energy storage subsystems.
Parametric Effects on the Performance of a Solid Adsorption Solar Refrigerator During Collector Cool-Down and Refrigerant Evaporation/Readsorption Phases
Authors: Ogueke Nnamdi V. , Anyanwu Emmanuel E.
Published: February 2009

The performance analysis of a solid adsorption solar refrigerator during the collector cool-down and refrigerant evaporation/re-adsorption phases is presented. The effects of the condenser pressure, evaporator pressure and initial adsorbate concentration on the collector cool-down and refrigerant evaporation/re-adsorption were tested. The adsorbate concentration re-adsorbed increased from 55% to 98% when the initial adsorbate concentration was dropped from 0.29kg/kg to 0.21kg/kg while the mass of ice produced rose from 0kg to 1.5kg for the same range of variation of initial adsorbate concentration.
An Analytical Solution for Dynamic Thermal Transmission Loads
Authors: Mirza Kazim , Kissock Kelly
Published: February 2009

Thermal mass in building envelopes reduces the magnitude of diurnal conductive loads and, in some cases, reduces energy use for heating and cooling. In general, dynamic simulation is required to estimate the magnitude of these effects. This paper seeks to derive closed-form expressions of thermal time lag and amplitude dampening through building envelope structures, to aid in the design process before detailed simulation is performed, and to improve intuition about the effects of thermal mass in buildings. An analytical solution for the temperature distribution through an infinite wall subjected to a sinusoidal temperature boundary condition is derived. The solution is verified by comparison with a finite element solution. Next, it is hypothesized that the analytical solution for an infinite wall could also describe the temperature variation on the inside surface of a finite wall. The hypothesis is tested by comparing the temperature distribution predicted by the analytical solution to the temperature distribution predicted by a finite element model of a finite wall. The results confirm that analytical solution adequately described the temperature variation in a finite wall. Based on the analytical solution, separate closed-form expressions of time delay and amplitude dampening for thermal load transmission through building envelopes are derived. The use of these expressions is demonstrated for light frame and concrete walls.
Heating of Bee Honey, Olive Oil, Milk and Water in a Solar Cooker Box Type With Internal Reflectors
Authors: Terres H. , Ortega J. A. , Gordon M. , Morales J. R. , Lizardi A.
Published: February 2009

Numerical simulation results are shown to determine the heating in liquids when a solar cooker box type with internal reflector is used to this end. The data evaluated correspond to temperature values from bee honey, olive oil, milk and water when they are heated in the solar cooker. The maximum simulation temperatures reached are 91.8, 91.6, 86.2 and 85.3 °C that correspond to bee honey, olive oil, milk and water respectively. A comparative between simulation and experimental results also are shown. The values presented evidence the influence of the specific heat in each fluid considered. In the numerical simulation were used solar radiation and environment temperature values for February 26, 2006 in Mexico City. The experimental data were acquired using an Eppley piranometer and a Field Point device and were used as initial numerical conditions in the simulation. The processing information acquired was made using the LabView 7.0 software.
Development of Power-Based Fan Airflow Stations
Authors: Wang Gang , Liu Mingsheng
Published: February 2009

Airflow measurements are critical for heating, ventilation and air conditioning (HVAC) system operations, energy conservation and fault detection. A fan-head-based fan airflow station, which determines airflow using measured fan head and speed, has been developed. However, the fan-head-based fan airflow station cannot measure the airflow associated with a flat fan head curve. To solve this problem, a motor-power-based fan airflow station is developed in this paper. The motor-power-based fan airflow station determines fan airflow using motor power and speed. Since both the motor power and speed can be directly obtained from the motor Variable Frequency Drive (VFD), no additional sensors are required for implementing a motor-power-based fan airflow station. A motor-power-based fan airflow station was implemented in a laboratory exhaust system. This paper presents the fundamental theory of the motor power-based fan airflow station and the experiment results.
The Effect of Thermal Mass on Thermal Transmission Loads
Authors: Gilbert Robert B. , Kissock Kelly
Published: February 2009

A finite-difference model is used to simulate the effects of thermal mass on thermal load. A sinusoidal function is used to simulate the exterior air temperature. The interior air temperature set point remains constant. The mechanism by which thermal mass affects thermal load is described. Equations are given to calculate thermal load as a function of the exterior air temperature amplitude, the temperature above and below the mean temperature. Equations are given to calculate the minimum thermal load resulting from thermal mass and therefore the maximum thermal load reduction with thermal mass. Equations and methods are given to calculate the minimum thermal load resulting from thermal mass from weather data files, TMY or TMY2 files. A design equation is given as a guideline to determine the amount of thermal mass required to reduce the thermal load with given weather conditions.
Field Evaluation of a Near Zero Energy Home in Oklahoma
Authors: Hendron Robert , Hancock Ed , Barker Greg , Reeves Paul
Published: February 2009

The authors evaluated a Zero Energy Home (ZEH) built by Ideal Homes in Edmond, Oklahoma, that included an extensive package of energy-efficient technologies and a photovoltaic (PV) array for site electricity generation. The ZEH was part of a Building America (BA) research project in partnership with the Building Science Consortium to exhibit high efficiency technologies while keeping costs within the reach of average home buyers, and was a modified version of a production 1584-ft2, three-bedroom, single-story, slab-on-grade design with attached garage. The home included a tight, well-insulated envelope, an energy recovery ventilator, high-performance windows, tankless gas water heater, efficient lights and appliances, and a ground source heat pump (GSHP). We conducted a series of short-term tests beginning in August 2005, and have collected long-term data under occupied conditions since February 2006. The GSHP performance was disappointing until the outdoor unit was replaced, after which time the efficiency began to meet expectations. However, the electricity use of the replacement unit was higher than expected because of an unusually low cooling setpoint. Based on the measured test results, the predicted whole-house energy savings compared to the BA Benchmark was 96%, with savings of 55% for efficiency measures alone.
Conversion and Performance Analysis of a Small Utility Vehicle Operating on Hydrogen Fuel
Authors: Fifield Ronald , Gardner Julian , Boehm Robert
Published: February 2009

Hydrogen as a combustible fuel offers great promise as a renewable alternative to fossil fuels. Test platforms are an important step toward the commercialization of any renewable fuel, as they can highlight more efficient means of implementing new and enhancing existing technologies. One such platform involves the conversion of gasoline fueled engines to operate on gaseous hydrogen. Traditional means for converting an engine to operate on hydrogen consists of port injection with slight modification to the spark timing. Due to stringent emissions standards, control over the production of NOx typically received precedence over volumetric efficiency and ultimately power output. This has been typically accomplished using very lean burn regimens. Through the advancement of computer control for injection systems, significant improvements have been made in the fuel delivery system resulting in better fuel mileage, emissions, and power output while using near-stoichiometric conditions. Highlighted in this paper is the conversion of a single cylinder, 2-seater utility vehicle with special emphasis on the direct injection system and performance results. The latter include operations on three fuels: gasoline, natural gas, and hydrogen. Generally the hydrogen-related components were able to be installed in the areas within the vehicle used for the original gasoline system. Experiences in designing a direct-injection system as well as the application of a computer-control system are described. Also contained are emissions comparisons to similar conversions as well as that of the pre-modified engine operating on gasoline.
Spectral Transmission of a Solar Collector and Fiber Optic Distribution Hybrid Lighting System
Authors: Maxey L. C. , Parks J. E. , Beshears D. L. , Earl D. D. , Lapsa M. V. , Muhs J. D.
Published: February 2009

Increased use of solar energy will reduce requirements for non-renewable energy sources such as fossil fuels and reduce associated greenhouse gas emissions. The benefits of replacing fossil-based energy with solar energy are often dependent on the application and operational or duty cycle for power demand. One particularly efficient use of solar energy is hybrid lighting. In hybrid lighting, solar light is concentrated into optical fibers and then coupled with supplemental electrical lighting to maintain a constant level of illumination. The system is able to offer reliable lighting with less energy consumption from the electrical grid (which is often driven by non-renewable sources). This technique offers energy efficiency benefits since the solar light is used directly and suffers no conversion losses. Furthermore, the solar spectrum provides an illumination that lighting engineers value for it’s quality; office inhabitants appreciate for its comfort; and retailers believe leads to increased sales. When available solar light is low, the hybrid system allows traditional light sources to reliably meet lighting demands. The success of the solar hybrid lighting system is dependent on the collection and transmission efficiency of the system. In this study, the spectral transmission of a hybrid lighting system is characterized. The system is composed of a 200-sun concentration reflective solar collector and a plastic fiber optic distribution network. The ultraviolet (UV), visible, and near-infrared (NIR) spectral transmission was characterized over a spectral range of 200 nm to 2400 nm. The UV and NIR performance of the system is critical since optical fiber damage can be caused by both UV and NIR light; thus, optimal system design maximizes the collection and transmission of visible light while minimizing the transmission of the UV and NIR light. Spectral transmission data for all components in the hybrid system are presented, and performance properties relative to solar applications are discussed.
Numerical Modeling of Electrochemical Process for Hydrogen Production From PEM Electrolyzer Cell
Authors: Katukota Shanthi P. , Nie Jianhu , Chen Yitung , Boehm Robert F. , Hsieh Hsuan-Tsung
Published: February 2009

Numerical simulations of proton exchange water electrolysis for hydrogen production were performed for the purpose of examining the phenomena occurring within the proton exchange membranes (PEM) water splitting cell. A two-dimensional steady-state isothermal model of the cell has been developed. Finite element method was used to solve the multicomponent transport model coupled with flow in porous medium, charge balance and electrochemical kinetics. The Maxwell-Stefan equation is applied for the multi-component diffusion and convection in water distribution electrodes. The Butler-Volmer kinetic equation is used to obtain the local current density distribution at the catalyst reactive boundaries. Darcy’s law was applied for the flow of species in the porous electrodes. Parametric studies are performed based on appropriate mass balances, transport, and electrochemical kinetics applied to the electrolysis cell. There are significant current spikes present at the corners of the current collector. The current density varies significantly in the cell, being highest at the corners of the current collector. As the water on the anode side flows from the inlet to the outlet, the mass fraction of oxygen increases. This is the effect of oxygen concentration due to the effect oxidation of water. On the cathode side, as the mass fraction of water decreases there is little variation in the hydrogen mass fraction content due to the effect of hydrogen reduction.
VRA Enhancement of Two Stage LiBr Chiller Performance Improves Sustainability
Authors: Ludovisi Daniele , Worek William M. , Meckler Milton
Published: February 2009

Multi-effect LiBr absorption chiller must take advantage of higher temperature heat sources to achieve higher COP so as to be competitive with lower first cost comparable commercially available, efficient electric chillers under current market pricing conditions. Yet a nominal conventional double-effect absorption chiller operating at a COP of 1.0 versus a comparable efficient motor driven centrifugal chiller operating at a COP of 7.0 will consume slightly less than twice the amount of prime natural gas (NG) source energy assuming a local 28% NG fired electric utility plant’s annual average efficiency and a 10% gas distribution leakage and 10% electric transmission loss to user’s meter. However if the COP of the above referenced double-effect LiBr absorption chiller were doubled, it would consume approximately the same amount of prime NG source energy and equally sustainable from an environmental impact standpoint. Consequently research to further improve double-effect LiBr absorption chillers beyond the VRA benefits reported to date was investigated in this study. Former simulation studies of a low differential pressure-vapor recompression absorber (VRA) reported in 2001 indicated a 7% COP efficiency gain, while additional simulation studies reported in 2006 indicated a 38% COP efficiency gain with the VRA operating at elevated differential pressures at the same upper stage concentrator temperature previously considered. Double-effect LiBr absorption chillers are limited by corrosion effects, which have been shown to accelerate significantly above 160 °C. In this paper, a reverse series flow, double-effect LiBr absorption chiller employing a VRA is investigated over a wider range of upper stage concentrator and absorber cooling temperatures but operating at the same low and elevated pressure differential levels reported earlier showed significant improvement in COP efficiency, capacity performance and projected hybrid operational cost.
Application Analysis and Economical Study on and Under-Floor Electric Heating System With Superconducting Liquid in China
Authors: Shi Guohua , Zhang Xutao , Liu Songtao , Zhang Weitang , Wang Hong
Published: February 2009

An under-floor electric heating system with superconducting liquid was manufactured. This system can charge heat by using cheap nighttime electricity and discharge the heat stored at daytime, with the merits of decreasing electricity load. In the present work, the operating principle of the system is discussed, and its characteristics are analyzed. In order to study the system’s thermal property, one prototype room with the system and the other room with a heating cable system were set up in Beijing. The experimental results testify the feasibility and comfort of the heating mode and show that it can save 19% electric energy compared with the heating cable system. To analyze the economical efficiency of the system, an economic comparison was made. The result indicates that the system is most economical in comparison with other radiant floor heating systems.
Site Specific Optimization of Rotor/Generator Sizing of Wind Turbines
Authors: Martin Kirk A. , Schmidt Michael F. , Shelton Sam V. , Stewart Susan W.
Published: February 2009

Economics, including all incentives, is the primary factor that drives the development of wind farms. Optimizing the wind turbine generator size-to-rotor size design based on an economic figure of merit shows that maximum wind turbine capacity factor does not yield the best economics for a given wind resource. A large rotor on a small generator will have a high capacity factor but a low annual output of electrical energy. For the same capital investment a different configuration would produce more electricity making the project more economically sound. This study varied rotor-to-generator size at a fixed capital cost and used a modified blade element momentum model to predict annual electrical energy production for each design at a given wind resource. Optimal design was the design that resulted in the highest annual electrical energy production. This was done at a series of fixed costs and a series of wind resources defined by the Weibull distribution parameters. The results indicated the following: At larger turbine sizes, (higher capital cost per turbine), the economics shifted toward a larger generator and smaller rotor (relatively). This exact relationship is dependent on the wind resource. At large turbine sizes, greater flexibility is shown in optimum generator sizing vs. rotor sizing. Having multiple generator size options for the same rotor size allows developers to more closely match and capitalize on the characteristics of their wind resource. The end result of the research is a set of diagrams developers can use to select the best turbine based on economics for their wind resource. This provides an additional tool they can use to make their projects more cost effective.
Evaluation of Cooling, Heating, and Power (CHP) Systems Based on Building Energy-Rating
Authors: Fumo N. , Mago P. J. , Chamra L. M.
Published: February 2009

Cooling, Heating and Power (CHP) systems are a form of distributed generation that uses internal combustion prime-power engines to generate electricity while recovering heat for other uses. CHP is a promising technology for increasing energy efficiency through the use of distributed electric and thermal energy recovery-delivery systems at or near end-user sites. Although this technology seems to be economically feasible, the evaluation and comparison of CHP systems cannot be restricted to economical considerations only. Standard economic analysis, such as life cycle economic analysis, does not take in consideration all the benefits that can be obtained from this technology. For this reason, several aspects to perform a non-conventional evaluation of CHP systems have to be considered. Among the aspects to be included in a non-conventional evaluation are: power reliability, power quality, environmental quality, energy-efficient buildings, fuel source flexibility, brand and marketing benefits, protection from electric rate hikes, and benefits from promoting energy management practices. Some benefits of these non-economical evaluations can be transferred into an economic evaluation but others give intangible potential to the technology. This paper focus on a non-conventional evaluation based on energy-efficient buildings, which is associated to energy conservation and improvement of the building energy performance rating for government energy programs like Energy Star and Leadership in Energy and Environmental Design (LEED). Results show that the use of CHP systems could improve the Energy Star Rating in more than 50 points. The Energy Star Rating is significant on the LEED Rating as a building can score up to 10 points of the 23 available in the Energy & Atmosphere category on energy efficiency alone. As much as 8 points can be obtained in this category due to the Energy Star rating increment from the use of CHP systems. Clearly the use of CHP systems will help building owners to reach the benefits from these energy programs while improving the overall energy use and energy cost.
Research of Optimal Operation on Micro-Turbine CCHP System
Authors: Bing Wei , Wang Zhiwei , Lu Jiang , Li Li
Published: February 2009

Nowadays the application of MT-CCHP (Micro-Turbine Combined Cooling Heating and Power) systems is becoming more and more popular. Based on the micro-turbine, MT-CCHP systems use the fuels of natural gas, marsh gas and gasoline etc., work via the micro-turbine and surplus heat energy of the gasses and supply the heating, cooling and power to the buildings. MT-CCHP system has the advantages of step utilization in energy, energy conservation and environment protection, and is one of the most important directions of distributed energy system. In this paper, according to the steps of optimal scheme, several operational schemes of CCHP systems for a selected building are studied. The objective functions and their constraints are determined so as to minimize the annual total cost. The selected schemes are optimized using a program. The most suitable scheme to the building is gained and the optimal strategy is proposed. At last, the relationship of the natural gas price, the micro-turbine price and the investment recovery period of CCHP are studied. All these above will be good references to the economic analysis of BCHP (Building Cooling Heating Power) system.
Development of a Cheap and Simple Sensor-Based Polar Tracking System
Authors: Castro Ulises , Vela´zquez Nicola´s , Mora Mario , Herna´ndez Iva´n O. , Cantu´ Jesu´s A.
Published: February 2009

The present work describes the design and construction of a Sensor-Based Polar Tracking System. It was implemented to drive a Photovoltaic module with four panels parallel connected, but it can be used to work with any concentrator with this type of tracking. This system looks for the most incidence radiation region, increasing the amount of collected energy, and therefore increasing the amount of electric energy produced. To control the motion of the electromechanical mounting, a very simple and economic circuit has been developed. Whole system has been tested in different applications like: solar radiation measurement, supplying the energy to a water pump for a Solar Thermal cooling and also to an evaporative cooling system. Experimental results show an increase of the collected energy up to 29% compared with a fixed PV module.
Dynamic Simulation of a Micro-CHP Facility: A Case Study
Authors: Cho Heejin , Luck Rogelio , Chamra Louay M.
Published: February 2009

Combined heating and power (CHP) systems are becoming increasingly popular because of their increased power reliability, thermal efficiency, and reduction of emissions. As with CHP systems, micro-CHP (micro-Cooling, Heating, and Power) system consists of power cogeneration system and thermally-activated components such as absorption chillers, water tanks, boilers, and air handling units. Although much work have been done on using steady-state models that follow load profiles to demonstrate the economic advantage of CHP systems, there has not been much work using dynamic simulation of CHP systems which include the transient response of the building along with the rest of the CHP components. This paper presents the results from the dynamic simulation of the micro-CHP system used to model the test facility at Mississippi State University (MSU) and discusses some important issues that were considered in obtaining a dynamic model. TRNSYS, a dynamic simulation program, is used as a simulation engine to evaluate the performance of the micro-CHP system with respect to transient heating, cooling, and electric power demand of the test facility. Details of the building model include geometric and material information, internal heat generation following the equipment and occupancy schedules, local weather information, and estimated infiltration of the test facility. The building model is connected to dynamic models of the power cogeneration system and thermally-activated components. In the test facility, a four-cylinder internal combustion engine with a 15-kW generator is operated to generate electric and thermal energy, and a 10-ton absorption chiller is used for space cooling.
The Off-Grid Zero Emission Building
Authors: Kramer Justin , Krothapalli Anjaneyulu , Greska Brenton
Published: February 2009

This paper deals with the Off-Grid Zero Emissions Building (OGZEB), a project undertaken by the Sustainable Energy Science & Engineering Center (SESEC) at 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 resulting 1000 square foot building will be partitioned such that 750 square feet will be a two bedroom, graduate student style flat with the remaining 250 square feet serving as office space. This arrangement will allow the building to serve as an energy efficient model for campus designers in student living and office space. The building will also serve as a prototype for developing and implementing cutting edge, alternative energy technologies in both residential and commercial settings. For example, hydrogen will be used extensively in meeting the energy needs of the OGZEB. In lieu of high efficiency batteries, the excess electricity produced by the building’s photovoltaic (PV) panels will be used to generate hydrogen via water electrolysis. The hydrogen will be 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. Although commercial variants already exist, a highly efficient water electrolysis device and innovative PEM fuel cell are currently under development at SESEC and both will be implemented into the OGZEB. 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.
Alignment Strategy Optimization Method for Dish Stirling Faceted Concentrators
Authors: Andraka Charles E.
Published: February 2009

A Dish Stirling parabolic concentrator typically consists of a number of mirror facets that must be aligned to focus the concentrated sunlight on the engine receiver. An alignment strategy must be developed to deliver the energy uniformly to the receiver while maximizing system performance. Several criteria must be met in order to maximize the performance and lifetime of the system. The peak flux should be minimized at the receiver to extend life. This is accomplished by locally optimizing the mirror aimpoints, minimizing overlap of facet images. The energy delivered to each cylinder of a multi-cylinder engine should be balanced to maximize the power production capability of the engine. This is accomplished through globally optimizing the mirror aimpoints. Depending on dish geometry, both of these constraints will be met by moving the aimpoints of certain facets away from a single point at the center of the aperture. However, this often results in a larger aperture or more flux spillage. The larger aperture results in greater thermal and reflective losses from the receiver cavity. This paper proposes and demonstrates a novel approach to optimizing the alignment strategy while obeying these constraints. The method uses an approach similar to molecular dynamics to globally and locally distribute the power on the receiver, while imposing movement constraints at the aperture to limit the focal plane spot size. The method can also impose additional geometric constraints at the receiver plane to accommodate un-cooled surfaces. The method is explored and demonstrated on the Stirling Energy Systems 25kW dish Stirling system at Sandia National Laboratories. The approach provides a receiver flux distribution and power balance equal to the strategy developed by McDonnell Douglas in the early 1980’s, but with an aperture size equal to that of the single aimpoint strategy. This should result in about a 1kW increase in power generated at rated conditions, with no additional cost, due to reduced thermal losses from the receiver. The method can be extended to other point-focus concentrating solar technologies. On a tower, the heliostat aiming strategy could be dynamically updated to accommodate flux profile needs, sun position, or maintenance in the field.
First and Second Law Thermodynamic Analysis of a Domestic Scale Trigeneration System
Authors: Tracy T. , Ordonez J. C. , Vargas J. V. C.
Published: February 2009

The potential use of small-scale trigeneration systems in domestic homes, especially for emergency use in the event of a hurricane or natural disaster where electricity and useful power are at a premium, is increasing. They have the ability to produce both useful thermal energy and electricity from a single source of fuel such as gasoline, natural gas, or other alternate fuel. However, small-scale systems present some technological challenges in order to achieve a significant increase in efficiency over conventional systems. This paper addresses the fundamental question of the splitting of a hot exhaust into two heat recovery heat exchangers that are part of a trigeneration system. We consider a system which produces electricity, refrigeration, and hot water by recovering waste energy from a reciprocating internal combustion engine. First and second law analyses were performed on the refrigerator and water heating heat exchangers and on the overall system. An optimal splitting of the available hot exhaust stream between the refrigerator and the hot water heat exchangers is identified. The thermodynamic optima is sharp and robust with respect to the variation of refrigerant and water inlet temperatures.
Self-Starting Hybrid ‘H’ Type Wind Turbine
Authors: Manohar Krishpersad , Rampartap Annil , Ramkissoon Rikhi
Published: February 2009

Wind energy is one of the fastest growing alternative energy resources being taped into worldwide. Vertical axis Darrieus ‘H’ type lift turbines have the potential to compete effectively with the more widely used conventional horizontal axis wind turbines. However, a disadvantage is when the rotor is stationary, no net rotational force arises, even at high wind speed. The rotor must already be spinning to generate torque and the design is normally not self-starting. In this study a hybrid Darrieus ‘H’ type lift turbine was designed to operate as a self-starting drag type turbine at low rotational speed. With increasing rotational velocity the centrifugal force converted the drag type blades to full symmetrical airfoil sections making the turbine lift type. Design calculations, construction and testing of a two-blade prototype with 43 cm long blades, 14 cm wide, which formed a symmetrical airfoil of NACA 0018 profile when closed. The diameter for the turbine was 1.448 m and tests were conducted at six pitch angles with respect to the closed blade section (0°, 15°, 22.5°, 30°, 37.5° and 45°). Test results showed that the wind turbine was self-starting and the shaft speed increased linearly with wind speed at all angles of attack for moderate wind speed up to 10 m/s. However, the rate of change in shaft speed with wind speed showed an increase from 0° angle of attack to a critical 37.5° angle of attack and then decreased at 45° angle of attack. This observation is consistent with airfoil theory that greater drag forces exist at smaller angles of attack. A similar trend was observed for shaft power and turbine efficiency with maximum values of 49.5 W and 24%, respectively, at a wind speed of 8.29 m/s for the 37.5° angle of attack. The tip speed ratio increased from a minimum of 0.83 at 0° to a maximum of 2.66 at 37.5° and then decreased at 45°. This indicated drag type operation (t.s.r. < 1) at small angle of attack and lift type operation (t.s.r. > 1) at higher angle of attack. This trend was consistent with theory as the drag force decreased the aerodynamic lift force increased with increasing attack angle, causing the blade speed to exceed that of the wind speed.
Enhancing the Power Delivery Infrastructure to Support Expanded Energy Efficiency Initiatives
Authors: Gellings Clark W. , Mansoor Arshad
Published: February 2009

The objectives of this paper are to examine the benefits of electric end-use energy efficiency as well as the potential cost to enhancing the current electric distribution system, to examine the quantifiable impact of electric end-use energy efficiency as an energy resource, to suggest critical technological advances that must be made to the current electric distribution system to enable greater use of electric end-use energy efficiency, and to summarize a proposed technology R&D initiative.
Off-Grid Residential Hydrogen Energy System
Authors: Robbins Curtis M.
Published: February 2009

Many energy consuming applications are beyond the realm of a distributed power network. These applications require an economical means for constant and sufficient power. It is the goal of the off-grid Hydrogen project to supply this current and future demand. The project is a mobile unit consisting of inverters, batteries, an electrolyzer, hydrogen storage, propane storage, an internal combustion engine generator, and computer unit. A renewable energy source and a water source from the site are connected to the trailer. A residential load will be met using solar renewable energy in the form of solar panels and wind turbines. The mobile device can be brought to off-grid locations to supply the electricity requirements of a current residential lifestyle.