bluuebunny/crossref_metadata_2025_split huggingface dataset:
Design, Construction, and Testing of a Small Scale Solar Chimney for Nomadic Herdsmen
Authors: Chappell Ryan D. , Congdon Michael J. , French Jesse J. 
Published: July 2013

The basic solar chimney concept remains largely unchanged since being proposed nearly a century ago. The air inside a collector heats up, and becomes less dense and begins rising toward the center of the collector as the covering is sloped upward towards a centrally located chimney. Heat and air flow increases as it moves toward the chimney. When a turbine is placed in this chimney, electricity can be generated from the air flow.
Using previously published research [1] on small scale solar chimneys, the authors designed and fabricated a small scale solar chimney. Performance variables were optimized to achieve peak performance and theoretical electrical output. The solar chimney was designed to achieve low material cost, and minimal maintenance effort without the use of heavy machinery.
The solar chimney designed by the authors was constructed and tested for implementation in remote regions where land space is practically unrestricted and electrical power is desired for lighting and communication. The project team conducted an assessment of one likely location for this solar chimney in Northern Mongolia during the summer of 2011. There are nomadic people groups who do not have electrical power but have vast amounts of land at their disposal. The solar chimney is a potential source of electricity for these people groups, as it was also designed to be transportable, lightweight, and inexpensive.
An Unexpected Sustainable Energy Solution
Authors: Keller Michael F. 
Published: July 2013

A recently patented hybrid technology may prove to be an energy game-changer. This innovative integrated combined cycle uses two fuels and a large gas (combustion) turbine in tandem with a small, efficient helium nuclear reactor to cleanly produce electrical power.
The hybrid approach to energy sustainability combines the strengths of individual energy assets to yield an optimal solution to meet the planet’s needs. This integration is more effective than the sum of the individual technologies by themselves. The hybrid is able to efficiently use all of fuel resources available in the US in a single power plant.
The hybrid-nuclear family of technologies is a fail-safe, environmentally friendly and evolutionary new direction for nuclear power and energy production.
Modeling of a High-Temperature Latent Heat Thermal Storage Module for Brayton Cycle Applications
Authors: Gehring Brian , Miller Fletcher 
Published: July 2013

Concentrating solar power (CSP) plants with thermal energy storage offer several advantages to plants without storage. Thermal energy storage (TES) allows CSP plants to produce power for longer periods of time each day, making them produce energy more like traditional, fossil fuel power plants. TES also gives the ability to time shift production of energy to times of peak demand, allowing the plant to sell the energy when prices are highest. A CSP plant with storage can increase turbine performance and reach higher levels of efficiency by load leveling production and can remain productive through cloud transients.
Power tower CSP plants are capable of producing extremely high temperatures, as they have the ability to oversize their solar field and achieve a greater concentration ratio. Studies have been conducted on variable working fluids, leading to higher working temperatures. This theoretically allows power towers to use more efficient, higher temperature cycles including the recuperated air Brayton cycle, although none currently exist on a commercial scale. This research focuses on developing a model of a high temperature TES system for use with an air Brayton cycle for a power tower CSP plant.
In this research we model one module of a latent heat TES system designed to meet the thermal needs of a recuperated Brayton engine of 4.6 MWe capacity for six hours. A metal alloy, aluminum-silicide (AlSi), is considered as the phase change medium. The storage tank is approximately 161 m3, or a cylinder with a 5 m diameter that is 8 m tall filled with AlSi with several air pipes throughout the volume. We model the volume around a single pipe in a 2-D cylindrical coordinate system, for a module size of 0.2 m in diameter and 8 m long. The advantages of using AlSi alloys is that they have variable melting temperatures depending on the relative concentration of the two metals, from 577 C for the eutectic composition of 12.6% silicon to 1411 C for 100% silicon. This attribute is taken advantage of by the TES model as the composition of the AlSi alloy will vary axially. This will allow a cascaded type storage system within one tank and with one material. The use of FLUENT to model this problem is first validated by several analytical solutions including Neumann’s exact solution for a one-dimensional Cartesian geometry and the Quasi-Steady Approximation in a 1-D cylindrical geometry. The model developed will establish charge/discharge times for the storage system, round-trip efficiency of the system, ability of the system to meet the demand of the Brayton cycle, and the validity of using off-eutectic metal alloys in a cascade as a latent heat TES medium.
Shaping Our Future With Sustainable Energy: A Direction From Young Engineers
Authors: Feldhoff Jan Fabian , Hofmann Carina , Hübner Stefan , Kammesheidt Jan Oliver , Kilbane Martin , Bachmann Kulik Julie , Pilli Siva , Schubert Franco , Tsutsui Waterloo , Tung Charlene 
Published: July 2013

It is broadly accepted that current energy systems should become more sustainable in both a global and local context. However, setting common goals and shared objectives and determining the appropriate means by which to get there is the subject of heavy debate. Therefore, the American Society of Mechanical Engineers (ASME) and the German Association of Engineers (VDI) initiated a joint project aimed at providing a young engineers’ perspective to the global energy conversation. The young engineer project teams set a common goal of assembling a completely sustainable energy system for the U.S. and Germany by 2050. This includes not only the electricity market, but the overall energy system. Based on the current global energy paradigm, a completely sustainable energy system seems very ambitious. However, multiple analyses show that this path is possible and would in the medium to long run not only be desirable, but also competitive in the market. This future ‘energy puzzle’ consists of many important pieces, and the overall picture must be shaped by an overarching strategy of sustainability. Besides the many detailed pieces, four main critical issues must be addressed by engineers, politicians and everybody else alike. These challenges are:
i) Rational use of energy:
This uncomfortable topic is rather unappealing to communicate, but is a key issue to reduce energy demand and to meet the potentials of renewable energy carriers.
ii) Balancing of electricity demand and generation:
This is a challenge to the electricity markets and infrastructures that are currently designed for base-load, mainly fossil power plants. The overall mix of renewable energy generation, storage technologies, grid infrastructure, and power electronics will decide how efficient and reliable a future energy system will be.
iii) Cost efficiency and competitiveness:
It is a prerequisite for industrialized countries to stay competitive and to establish RE in the market. Developing economic technologies while at the same time establishing a strong RE market is the secret of success.
iv) Acceptance of the system and its consequences:
The best energy strategy cannot be realized without broad public acceptance for it. Therefore, the understanding of the energy technologies and an objective discussion must be promoted — without old fashioned emotionalizing of certain risks.
The paper will present details on the four mentioned aspects, compare the situations between the U.S. and Germany, and propose solutions for appropriate political frame conditions to achieve a sustainable energy system.
Variable Speed Direct Drive Wind Controller for a Rim Driven Wind Turbine
Authors: Hubbard Chase , Hovsapian Rob , Kosaraju Srinivas 
Published: July 2013

Multi-blade shaft driven wind turbines depend greatly on the angle of attack as an important factor that the control system monitors such that a maximum amount of aerodynamic force is seen by the rotor blades. This is one significant difference when controlling a Rim Driven Wind Turbine (RDWT). The controller for a RDWT is required to simply point the tower such that it is facing the wind for maximum power generation. This is achieved by incorporating a Variable Speed Direct Drive (VSDD) wind operation control system to control the power production and safe operation of the RDWT. Another consideration for the control system is its integration with the generator. Since the power generation is rim driven, thus operating at a higher variable speed.
With information related to the wind turbine’s diameter and the wind speed at any given time it can be calculated how much power can be potentially generated. This can then be in turn relayed to the generator from the wind turbine controller. This information can be relayed using controller-controller communication (such as an analog voltage signal or protocol based communication such as MODBUS RTU or TCP/IP) representing the power coefficient from Betz’ Law.
A feasibly controllable system implements a signal from the overall wind turbine controller that in turn supplies the generator with how much power is available in the system to maximize power generation for a broad range of traditionally unrealizable wind conditions (3 m/s to 30 m/s). Rim Driven Wind Turbines represent an evolution in fundamental design of how the wind can be harnessed for power.
This paper will discuss the VSDD’s unique design and aspects of maintaining controllability thorough out the overall system operation.
Optimization Under Uncertainty: A Case Study of a Solar Absorption Cooling and Heating System for a Medium-Sized Office Building in Atlanta
Authors: Hang Yin , Qu Ming , Zhao Fu 
Published: July 2013

Solar absorption cooling and heating (SACH) systems currently still stay at development and demonstration stage due to the nature of the complex system. It is critical for practitioners and engineers to have a correct and complete performance analyses and evaluation for SACH systems with respects of energy, economics, and environment. Optimization is necessarily involved to find the optimal system design by considering these three aspects. However, many assumptions made in the optimization are sensitive to the energy, economic, and environmental variations, and thus the optimization results will be affected. Therefore, the sensitivity and uncertainty analysis is important and necessary to make optimization robust.
This paper uses a case study to explore the influence of the uncertainties on the SACH system optimization results. The case is a SACH system for a medium size office building in Atlanta. The one parameter at a time (OAT) sensitivity analysis method was applied firstly to determine the most sensitive inputs. Monte Carlo statistical method was utilized to generate the data sets for uncertainty analysis. The optimization problem under uncertainty was then formulated and solved. Due to the uncertainty associated with system inputs, the optimization solutions were found with certain types of the distributions. In addition, the scenario analysis on electricity price does not show large sensitivity to the objectives.
Promoting the Development of Concentrating Solar Power in the Middle East and North Africa Regions: Policy and Regulatory Implications
Authors: Gboney William K. 
Published: July 2013

It is estimated that within the next 40 years, solar thermal power plants would be capable of supplying more than half of the electricity needs of EUMENA. While solar irradiance differs widely in Europe due to seasonal variations, in the MENA region, there is abundant and continuous solar irradiance. This make the MENA region suitable for establishing CSP plants and exporting the electricity generated to Europe. This has driven many institutions and agencies, including the World Bank and the Desertec Foundation, to propose various schemes to promote the use of CSP systems in the MENA region.
The objective of this paper is to examine the existing policy and regulatory frameworks in the MENA countries, identify any barriers and make recommendations on how to surmount these barriers, to increase the scale and scope of utilizing CSPs and other renewable energy technologies (RETs) in the region. The paper concludes by making a number of policy and regulatory recommendations to support utilization of solar thermal energy resource within the MENA region.
Wind Energy and Compressed Air Energy Storage Potential for New York City
Authors: Waite Michael , Modi Vijay 
Published: July 2013

The energy potential from wind is significant in many locations in the U.S., including in some areas of New York State. The intermittent availability of wind — specifically, higher wind potential at night and in the winter in New York — would require extensive storage to make use of that energy during times of peak electricity demand — during the day and in the summer. Although the total energy available from wind may be sufficient and available at a low cost, the cost of implementing traditional storage techniques (e.g. batteries) would be expensive and require large amounts of space to address the offset supply and demand profiles. As such, base electricity loads are likely to continue to be served by a combination of less expensive energy conversion technologies, particularly given the current low cost of wholesale natural gas for gas-fueled power plants. Compressed air energy storage (CAES) has been evaluated — and implemented or proposed at a small number of facilities — as a potential energy storage technology that could be used to reduce the amount natural gas required to operate compressors at natural gas-fueled power plants serving base electricity demands. The result of this strategy is, effectively, an increase in thermal efficiency of the power plant.
This paper presents an evaluation of wind energy available at a site in New York State, its potential to meet the electricity demand in New York City, the expected capital and recurring costs of the overall system, and a comparison to electricity provided by natural gas, a likely alternative large-scale fuel source. Annual wind data for the site and annual New York City electricity usage were analyzed. Available wind energy was first assumed to serve any electricity demand above the New York City base load. Additional available wind energy operates compressors, storing compressed air in underground caverns. The cavern sizes required and associated capital costs was calculated. The expected reduction in natural gas requirements were calculated for gas-fuelled power plants designed to accept compressed air from the caverns, with additional electricity demand met by gas turbine power plants. The recurrent cost reductions associated with reduced natural gas volumes were calculated based on a range of natural gas prices to evaluate the feasibility of the system described above under different market conditions. The potential usage of CAES systems for peak electricity demands was also evaluated.
Macroencapsulation of Sodium Nitrate for Thermal Energy Storage in Solar Thermal Power
Authors: Pendyala Swetha , Sridharan Prashanth , Kuravi Sarada , Jotshi Chand K. , Ram Manoj K. , Rahman Muhammad , Stefanakos Elias , Goswami D. Yogi 
Published: July 2013

Storage systems based on latent heat storage have high-energy storage density, which reduces the footprint of the system and the cost. However, phase change materials (PCMs) have very low thermal conductivities making them unsuitable for large-scale use without enhancing the effective thermal conductivity. In order to address the low thermal conductivity of the PCMs, macroencapsulation of PCMs is adopted as an effective technique. The macro encapsulation not only provides a self-supporting structure but also enhances the heat transfer rate.
In this research, Sodium nitrate (NaNO3), a low cost PCM, was selected for thermal storage in a temperature range of 300–500°C. The PCM was encapsulated in a metal oxide cell using self-assembly reactions, hydrolysis, and simultaneous chemical oxidation at various temperatures. The metal oxide encapsulated PCM capsule was characterized using Fourier transform infrared spectroscopy (FTIR) and scanning electron microscopy (SEM). The cyclic stability and thermal performance of the capsules were also studied.
Yaw- and Trailer Dependence for Rear-Mounted Cooling Installations for Heavy Vehicles
Authors: Larsson Lisa , Wiklund Torbjörn , Dahl Erik , Löfdahl Lennart 
Published: July 2013

Due to stricter emissions legislation and increasing fuel prices vehicle efficiency must be improved. A trend that has been seen in recent years is increased engine power for heavy vehicles. Different exhaust gas after-treatment systems have also been introduced to be able to meet the emission demands. Though, these implementations do not only affect the engine power and the emission levels, they also tend to increase the cooling demand. Therefore, the cooling performance for vehicles has to be increased. At the same time the cooling installation in the front of the vehicle accounts for a substantial part of the total aerodynamic resistance of the vehicle. To reduce the fuel consumption the grill in the front could be covered and the cooling module could be relocated elsewhere. This would decrease the aerodynamic resistance; but a more frequent fan operation would most likely be needed to achieve the same cooling performance in different driving conditions.
This paper presents a comparative study of front-mounted and rear-mounted cooling package installations, using three different configurations for the rear installation on a rigid truck. For each case the cooling performance, fan demand and aerodynamic resistance were compared for different operating conditions at both lower and higher vehicle speeds and engine loads. The study was based on Computational Fluid Dynamics (CFD), where the simulations were performed in zero and five-degree yaw conditions, with and without a trailer added behind the truck.
It was seen that a relocation of the cooling module has a potential for fuel savings at higher vehicle speeds, due to the reduction in power to overcome the aerodynamic resistance. At lower vehicle speeds the cooling performance was increased since a lower system restriction was observed for the rear-mounted configurations. Results also showed that both the cooling performance and the aerodynamic drag was affected by the yawed air condition and when adding a trailer behind the truck. The mass airflow was increased when the air was directed towards the air intake, while it was decreased when the air intake was positioned at the leeward side of the vehicle. When the trailer was added behind the vehicle less air entered the cooling module at a higher vehicle speed. But for the critical cooling situation the trailer did not affect the amount of air entering the cooling module.
Stability of an Evaporating Liquid Film Under Nonequilibrium Conditions With Variable Gravity
Authors: Narendranath Aneet D. , Hermanson James C. , Struthers Allan A. , Kolkka Robert W. , Allen Jeffrey S. 
Published: July 2013

An evolution equation describing the dynamics of an evaporating liquid film has previously been developed from the governing equations of fluid dynamics after the application of the lubrication approximation and the choice of a viscous time scale.
The authors have solved the evaporating liquid film evolution equation with a validated numeric program. Different mechanical boundary conditions were successfully applied and their effect on the film dynamics was examined. The evolution equation has also been modified to include buoyancy driven instabilities.
This paper outlines a linear stability analysis that was performed on the time dependent, evaporating liquid film evolution equation. The effect of the evaporation rate, departure from equilibrium at the interface and variable gravity is examined by solving the equation as an initial value problem.
The Effect of Nozzle Shape and Configuration on Bubble Formation in a Liquid Cross Flow
Authors: Hassanzadeh Jobehdar Mona , Gadallah Aly H. , Siddiqui Kamran , Chishty Wajid A. 
Published: July 2013

Gas injection into a liquid cross flow from a nozzle causes bubble formations which have potential applications in industry such as chemical plants, waste water treatment and bio- and nuclear-reactors. The purpose of this study is to experimentally investigate the effects of nozzle shape and configuration with respect to the liquid cross-flow direction, on the bubbly flow characteristics such as bubble formation, detached bubble size and frequency at different gas and liquid flow rates. The experiments were conducted in a Plexiglas two-dimensional rig using a high speed camera. High speed imaging and an image processing algorithm were used to track each individual bubble and to quantify the bubble growth as well as the detachment frequency and the bubble velocity. Back light shadowgraphy which utilizes a low intensity diffuse light source to illuminate the background was used to image bubbles. Nozzles were mounted in the test section which was designed such that the flow in this section has a two-dimensional profile.
The results showed that the bubble size increases with an increase in GLR (gas to liquid flow rates ratio). Furthermore, the bubble formations and detached bubble size were strongly influenced by the nozzle shape and configuration.
Optimal Disturbances in Three-Dimensional Natural Convection Flows
Authors: Merzari Elia , Fischer Paul , Pointer W. David 
Published: July 2013

Buoyancy-driven systems are subject to several types of flow instabilities. To evaluate the performance of such systems it is becoming increasingly crucial to be able to predict the stability of a given base flow configuration. Traditional Modal Linear stability Analysis requires the solution of very large eigenvalue systems for three-dimensional flows, which make this problem difficult to tackle.
An alternative to modal Linear stability Analysis is the use of adjoint solvers [1] in combination with a power iteration [2]. Such methodology allows for the identification of an optimal disturbance or forcing and has been recently used to evaluate the stability of several isothermal flow systems [2]. In this paper we examine the extension of the methodology to non-isothermal flows driven by buoyancy. The contribution of buoyancy in the momentum equation is modeled through the Boussinesq approximation.
The method is implemented in the spectral element code Nek5000. The test case is the flow is a two-dimensional cavity with differential heating and conductive walls and the natural circulation flow in a toroidal thermosiphon.