A large part of energy cost on cooling applications is attributable to heat income through external walls. The best way to save energy is to use the optimum insulation thickness. In this study, the optimum insulation thicknesses, insulation-energy costs, and savings resulting from the use of these insulations is calculated in cities selected from four different climate zones in Turkey for four various insulation materials such as foamboard, extruded polystyrene (XPS), rock wool, and expanded polystyrene (EPS) in cold storage applications. Calculations show that rock wool insulation material yields the highest savings. Optimum insulation thicknesses vary between 0.074 and 0.159 m, energy savings vary between 30.59 and 80.61 $/m(2), and payback periods for investment cost vary between 3.15 and 3.73 years for the cooling. DOI: 10.1061/(ASCE)EY.1943-7897.0000085. (C) 2013 American Society of Civil Engineers.
Availability of cooling water has been one of the major issues in the selection of nuclear power plant sites. Cooling water issues have frequently disrupted the normal operation at some nuclear power plants during heat waves and long droughts. One potential solution is to use ice thermal storage (ITS) systems that reduce cooling water requirements and boost the plants' thermal efficiency in hot hours. The ITS uses cheap off-peak electricity to make ice and uses the ice for supplemental cooling during peak demand time. The ITS also provides a way to shift a large amount of electricity from off-peak time to peak time. For once-through cooling plants near a limited water body, adding ITS can bring significant economic benefits and avoid forced derating and shutdown during extremely hot weather. For the new plants using dry cooling towers, adding the ITS systems can effectively reduce the efficiency loss during hot weather so that new plants could be considered in regions with a lack of cooling water. This paper will review light water reactor cooling issues and present the feasibility study results. DOI: 10.1061/(ASCE)EY.1943-7897.0000089. (C) 2013 American Society of Civil Engineers.
An experimental and theoretical study was performed to investigate the thermal performance of heat pipes as a heat exchanger. A series of experiments was conducted using R410A, R134a, R22, and R407C as working fluids. The dimensions of the heat pipes that were used in the test rig included 660 mm length, 20 mm outer diameter and 4 mm fin spacing with staggered arrangements. During the tests, the dry bulb temperature of the evaporator inlet was varied from 35 to 55 degrees C and the condenser inlet dry bulb temperature was varied from 20 to 25 degrees C. The influence of face velocity on the performance of the heat pipe heat exchanger was also studied. Many investigations were made to obtain the thermal performance and to ensure efficient and reliable operation of the heat pipe heat exchanger, and the results are presented in the present paper. Tests showed that using R410A, R134a, and R22 provided comparative results, whereas R407C was the least effective. The experimental thermal effectiveness of the heat pipe heat exchanger obtained from the experiments varied between 25 and 70% for R410A, R134a, and R22, whereas the experimental thermal effectiveness of R407C varied between 15 and 50%. A computer simulation program based on the effectiveness method and the number of transfer units was developed to estimate the thermal performance of the heat pipe heat exchanger and to compare the theoretical and experimental results. DOI: 10.1061/(ASCE)EY.1943-7897.0000091. (C) 2013 American Society of Civil Engineers.
In this work, the performance of proton exchange membrane (PEM) fuel cells has been analyzed for different oxidant (air and oxygen) flow rates (supplied at the cathode side). The performance analysis of a single PEM fuel cell coupled with a direct current (DC) permanent magnet motor (as load) was analyzed for air and oxygen. With an increase in the air flow rate, the maximum current values of the PEM fuel cell increase due to the reduction in the concentration of polarization losses (in the polarization curve) and the voltage regulation for the load increases. The maximum power production in a PEM fuel cell is a logarithmic function of different air flow rates. In this system, a DC permanent magnet motor with a reduction gear was used as a load on the PEM fuel cell. With the increase in air flow supply rates, the starting torque of the DC permanent magnet motor load improves. Also, a performance analysis was conducted for pure oxygen, and it has been observed that the PEM fuel cell provides a very good performance, even at the reduced supply flow rate of pure oxygen. For this work, a test bench was developed at Kocaeli University (Turkey), which consists of a PEM electrolyzer, a PEM fuel cell, and a DC permanent magnet motor with an air pump. The results of this work will be very useful for comparing the performances of the PEM fuel cell for different air and oxygen (as oxidants) flow rates for the dynamic loads (e.g., fuel cell vehicles with a DC permanent magnet motor). DOI: 10.1061/(ASCE)EY.1943-7897.0000090. (C) 2013 American Society of Civil Engineers.
Development of a huge wind-sailing solar cell raft (SCR) with dimensions of 5 x 5 km is proposed, which can generate electricity comparable to a 1,000-MW nuclear power plant in low-latitude Pacific Ocean. Solar energy of 8 k . Wh/m(2)/day or more is targeted because the SCR navigates in fine weather using weather satellites. The generated electricity will be transported by battery tankers loaded with a tremendous number of high-energy-density batteries. Studies based on available data indicate that there are vast open seas in the tropical Pacific Ocean, where the maximum solar energy attains 7 k . Wh/m(2)/day annually on average and conditions of winds, waves, and sea currents are favorable for the solar energy system to operate. Three major technologies for breakthrough to realize this system are discussed from their future perspectives. DOI: 10.1061/(ASCE)EY.1943-7897.0000088. (C) 2013 American Society of Civil Engineers.
Because of the up-front costs of add-on solar collection systems, the cost-effectiveness of solar energy is still in doubt. Building integrated solar thermal systems may improve the cost-effectiveness of add-on collection systems given their ability to expand to cover the entire area of a roof at a reasonable cost. The objective of this study was to evaluate the effectiveness of a newly developed flat plate integrated solar collector system. The developed collector system consists of a low-temperature flat plate collector integrated within a concrete building envelope. To evaluate this system, a full-scale test prototype of the solar collector was constructed and instrumented with thermocouples. Measurements were conducted over a 7-month period in which the solar collector was evaluated over different climatic conditions. On the basis of the results of the experimental program, it was determined that the solar collector provided an efficiency ranging from 49-75% in the range of ambient temperature, solar radiation, and inlet temperature evaluated in this experiment. The estimated efficiency of the system was on the high range as compared with the reported efficiency of similar systems. Depending on the extent of the collection area, the developed solar collector can provide a significant portion of the building's space heating and hot water needs, especially in the spring and summer seasons. DOI: 10.1061/(ASCE)EY.1943-7897.0000093. (C) 2013 American Society of Civil Engineers.
This works aims to develop and study a new reaction microhydro tubular propeller turbine with five blades as a promising answer to solve the lack of energy in rural and remote areas. The first stage is to validate numerical and experimental tests made for the flow behavior for different values of head, discharge, and rotational impeller speed. Using specific mathematical formulations, a blade model configuration is developed based on the velocity triangles at the impeller inlet and outlet and experimental results based on pressure, discharge, and velocity profiles in different turbine sections. Through characteristic parameters, performance curves are obtained allowing comparisons between experimental and computational fluid dynamics (CFD) results. Also, an evaluation of the hydrodynamic behavior is made for a scaled model application by similarity turbo machines theory. (C) 2013 American Society of Civil Engineers.
Cavitation in a valve leads to trouble and inconvenience for factories. Valves in a piping system are ruined, leading to costly replacements every several months. To reduce the cost caused by cavitation in a valve, a cage is utilized to make cavitation occur only in the region adjacent to the cage itself; therefore, only the cage needs to be replaced. To validate the design of a cage, simulation of the turbulent flow field inside a globe valve and the occurrence of cavitation are necessary for a valve designer. To reach this purpose, prediction of the cavitation inside the globe valve with and without a cage is undertaken, and a cavitation model is established in this study. The percentage of vapors in each computational cell is calculated using the proposed cavitation model. Two various cages, the one-stage perforated cage and the one-stage step cage, are considered. Vapor resulting from cavitation appears in the vortices existing inside the valve and at the downstream region of the globe valve without a cage. Nevertheless, vapor does not occur in those regions in the globe valve with those two cages; in other words, cavitation inside the globe valve primarily occurs in the vicinity of the cages. In the valve body and downstream region, ruin from cavitation is prevented when those two cages are installed in the globe valve. In addition to the globe valve, the proposed cavitation model can be applied to prediction of cavitation in other control valves. DOI: 10.1061/(ASCE)EY.1943-7897.0000084. (C) 2013 American Society of Civil Engineers.
The main goal of this research was to develop and understand the performance of a hybrid roof system that combined an amorphous junction photovoltaic panel in combination with copper panel and tubing encased in a low-iron glass. The setup encompassed 160 sq ft of the solar thermal electric panel (STEP) system supplied with a glycol-water closed-loop system. The system was fixed to a simulated roof assembly built at the optimal angle of 61 for winter solstice for the local area (Rolla, Missouri). The encased combination panel provided consistent electrical efficiency and mixed thermal efficiencies based on the hours of operation. In conclusion this paper will discuss experimental performance analysis on the STEP system thermal and overall outcomes. Further testing on the effects of a glazed versus unglazed panel yielded a 23% reduction in solar electric production; however, it increased thermal collection by approximately 200%. The present study shows that the idea of a STEP system is viable. A prototype hybrid solar thermal electric panel system was implemented in the Missouri Univ. of Science and Technology's solar house entry into the 2005 solar decathlon, and today the solar house is part of student housing and the solar research facility at Missouri Univ. of Science and Technology. DOI: 10.1061/(ASCE)EY.1943-7897.0000065. (C) 2012 American Society of Civil Engineers.
As the 21st century continues to unfold, worldwide energy infrastructures face unprecedented challenges. Global energy consumption is projected to grow by more than a third over the next 25 years, largely driven by a rapidly fast growing world population. Fossil fuel reserves are being depleted much more quickly than new ones are generated, which will in turn raise the long-term average and short-term volatility of fuel prices. Unforeseeable attacks and contingencies caused by humans or natural disasters pose constant threats to the security of power systems. As the largest man-made carbon dioxide emitter, the energy industry is undergoing a series of reforms, aiming to reduce its carbon footprint and impact on climate change. Part of this effort involves embracing renewable energy and efficiency to a much greater extent, which will require significant changes to the industry’s traditional business model. Along with grand challenges come grand opportunities. Countries throughout the world are providing various incentives to stimulate research and development, as well as investment in renewable energy. Renewable energy can be particularly suitable for the rapidly growing energy needs in developing countries, most of which have abundant renewable energy resources and the ability to manufacture the labor-intensive infrastructures needed to harness them. Ever-evolving technologies, exemplified by plug-in hybrid electric vehicles and smart-grid utility platforms, have created new interdependencies among the energy infrastructure and others, such as transportation and communication networks. The papers selected for this special issue address a wide range of relevant topics, including distributed generation, wind energy, photovoltaic technology, biofuels, energy storage, energy efficiency certificates, plug-in electric vehicles, and sustainability and resiliency measures. These papers reflect the extensive array of research topics driving efforts towards a more sustainable energy infrastructure. The first two papers discuss energy storage as a remedy to the intermittency of renewable energy. Huang et al. quantify the benefits of distributed photovoltaic panels coupled with batteries in the residential sector, using an agent-based electricity demand model combined with a stochastic unit-commitment model. In this case study, which was based on California’s residential sector, a daily savings of $5 was reported in the month of August, assuming 10% penetration levels for households with a 4 kW solar PV panel and a 0.5 kWh battery. Xie et al. propose amodel predictive-controlbased approach to the scheduling of wind generation with aggregated battery energy storage systems. The authors argue that the current approach of treating wind power as a nondispatchable negative load requires both high backup reserves from conventional generation and provides little incentive for wind farms to improve their forecasts. In contrast, the proposed approach incorporates wind power into the dispatch model, using energy storage to compensate for wind variability and uncertainty. Several numerically efficient algorithms for computing the optimal control strategy are presented, with computational results suggesting that the proposed framework is implementable in real-time electricity market operations. The third paper, co-authored by Brown and Hu, is concerned with biofuels, another type of renewable energy carrier. Fast pyrolysis has been recognized as a promising bioenergy production technology. The economic viability of this technology, however, continues to be a concern for commercial investors. Using data from the U.S. Energy Information Administration’s 2011 Annual Energy Outlook, the authors calculate the internal rates of return on fast pyrolysis facilities under six different policy scenarios. Under the scenario combining a cellulosic biofuel producer tax credit with a renewable fuel standard, which most accurately reflects the current politicoeconomic conditions, the analysis shows a 13.22% rate of return. Energy policy is also explored by the fourth paper in this special issue. Inspired by the successful implementation of tradable white certificate schemes in Italy and other European countries, Norero and Sauma assess the hypothetical implementation of a similar energy efficiency policy in Chile using a socioeconomic valuation methodology. The benefits from energy savings, reduced carbon dioxide emissions, and healthcare related savings are weighed against the cost of implementing the tradable white certificate scheme under low-, medium-, and high-cost scenarios, finding the present net value to be largely positive in all three scenarios. The fifth paper considers energy systems in an emerging and developing economy. As arguably the fastest growing major economy in the first decade of the 21st century, China’s energy systems are facing unprecedented challenges: from energy resource depletion to rapid growth of energy demand, from increasing fuel prices to pressure for reduction of emissions and pollution from fossil-based energy generation. Tan et al. present the status quo of photovoltaic power generation in China from various perspectives, including the growth of the photovoltaic market, solar energy resource distribution, research and applications, policies, and economic feasibility. The sixth paper addresses a fundamental question: how to quantitatively measure the sustainability and resiliency of an energy system. After observing the ambiguities and discrepancies among the descriptions of sustainability and resiliency in the literature, Mejia-Giraldo et al. propose a new model for quantitative measure of sustainability and resiliency from the perspective of long-term infrastructure planning for energy and transportation systems. The proposed model measures sustainability as the period of time that a system can function without violating a predefined set of requirements. The measure of resiliency is the cost of transition from a precontingency state to a postcontingency state. Finally, in the seventh paper, Stadler et al. focus on the optimal interaction of electric vehicles and smart grid facilities, including photovoltaic, solar thermal, stationary batteries, thermal storage, and combined heat and power systems—with and without absorption chillers. The distributed energy resources customer adoption model, originally developed by the Lawrence Berkeley National Laboratory, is extended to accommodate electric vehicles as energy storage devices. This case study examines a large school in the
The importance of water use in thermoelectric power plants is increasing across the nation. For example, power plants in New York and California are forced to deal with cooling systems that pose threats to ecosystems and water availability. The purpose of this paper is to summarize, compare, and contrast previous studies in this subject area using journal articles and government/laboratory reports. This literature review presents a myriad of results obtained from previously conducted research pertaining to (1) power generation in the United States, (2) water use in power plants, (3) power plant cooling technologies, (4) comparisons of cooling technologies (including cost), (5) impact of drought on power generation, and (6) projections of power generation and water use. Among the findings of this study is that whereas water usage data for once-through and wet-recirculating cooling systems are well developed, dry and hybrid cooling system data are not as complete. This review, therefore, serves as an assimilation of existing information and points out gaps in our knowledge base of the systems. DOI: 10.1061/(ASCE)EY.1943-7897.0000076. (C) 2012 American Society of Civil Engineers.
This study examined critical submergence for isolated and dual rectangular intakes. It is shown that the critical submergence for an isolated intake can be predicted by disregarding whole boundary blockages on the complete imaginary critical sink surface that is the combination of imaginary complete critical cylindrical and hemi-spherical sink surfaces. It is proposed that this theory can be applied to the rectangular intakes located in general geometrical and flow conditions (i.e., intake in still water, circulation imposed flow, non-developed cross-flow, multiple intakes, etc.) and that it does not require computation of blockages caused from flow boundaries. The concept of complete sink surface (disregarding whole boundary blockages) developed for an isolated intake was also applied to dual rectangular intakes. The agreement between available test data and theoretical results was found to be satisfactory.
This paper shares the results of a recent industry-supported study with the aim to develop a practical pricing model for backup reserve and wheeling in the semi-open-market structure of power systems. Instead of a closed-loop optimization framework, a key requirement in the study is to develop a systematic what-if tableau-type analysis with full control over pricing parameters during negotiations among market entities. With the help of newly developed compact and elegant universal distribution factors, the pricing framework attains a balanced strategy that ensures perceived benefits to both the buyer and the seller. The model and the associated computerized algorithm deal collectively with diverse issues, including (1) fulfilling local firm real-power (and reactive-power) demand requirements, (2) fulfilling local power-reserve requirements, (3) buying firm real (and reactive) power from the grid, (4) buying reserve power from the grid, (5) exporting firm real-power (and reactive-power) demand to remote load centers through the grid, (6) exporting reserve power through the grid, (7) wheeling of firm-power demand to remote-owned sites using the grid, and (8) wheeling reserve power to remote-owned sites using the grid. Practical implementation features of the computerized algorithms are also discussed with an illustrative case example. DOI: 10.1061/(ASCE)EY.1943-7897.0000079. (C) 2012 American Society of Civil Engineers.
Microgeneration using solar photovoltaic (PV) systems is one of the fastest growing applications of solar energy in the United States. Its success has been partly fueled by the availability of net metering by electric utilities. However, with increasing solar PV penetration, the availability of net metering is likely to be capped. Households would then need to rely on distributed storage to capture the full benefits of their installed PV systems. Although studies of these storage systems to assess their benefits to the individual household have been examined in literature, the systemwide benefits have yet to be fully examined. In this study, the utility level benefits of distributed PV systems coupled with electricity storage are quantified. The goal is to provide an estimate of these benefits so that these savings can potentially be translated into incentives to drive more PV investment. An agent-based residential electricity demand model is combined with a stochastic programming unit commitment model to determine these effects. A case study on the basis of the California residential-sector shows that at 10% penetration levels for households with a 4-kW solar PV panel with a 0.5-kW. h battery, the daily systems cost savings per household could be over $5 a day in August. DOI: 10.1061/(ASCE)EY.1943-7897.0000064. (C) 2012 American Society of Civil Engineers.
Electricity is a necessity for modern society. Similar to other commodities, electricity is generated and delivered to consumers through a transmission network. In the delivery process, it obeys Kirchhoff’s laws and undergoes losses. To determine a fair pricing in a deregulated electricity market, an exact analysis of loss is required. Several methodologies have been proposed to evaluate the nodal value of the system loss. However, losses over individual lines have different values. Consequently, the effect of losses on price is difficult to evaluate. In this study, analysts present a new methodology for allocating losses at each bus. Real power flow is decomposed into preserved power flow and lost flow, which are established by applying Kirchhoff’s law to each bus. With this procedure, it is possible to attribute how much power injection is used for preserved flow and loss and, consequently, to evaluate the component of losses in prices.
An energy-storage flywheel consists of a large inertia wheel sharing a common shaft with a motor generator (MG) set and with magnetic bearings to support the entire rotating assembly. Flywheels mounted on a special slug car are charged from the local utility grid and from regenerative-braking events. Usage of these power sources reduces fuel consumption and the related NOx emission by the locomotive-mounted Diesel generator sets (DGS). The flywheel-supplied power can replace the DGS-supplied power in one or more of the eight fixed power settings (notches), plus idle and reverse, which are common to most locomotives either for line-haul or switchyard service. The slug cars have separate traction motors to be driven by the flywheel systems so that the flywheel power and DGS power are electrically and physically decoupled. A system model is presented that includes the train dynamics coupled with the electromechanical models for the flywheels and traction motors. The modified Davis equation is employed in the train model to account for windage and other losses. A novel, feedback-based flux-weakening control of the flywheel's motor generator current-torque and speed-back electromotive force (emf) gain is employed to increase the charge capacity, depth of discharge, and regenerative-braking efficiency for the flywheels. The simulation results show significant cost-and emissions-reduction potential for the proposed hybrid DGS-flywheel locomotive power system in line-haul and switcher service. DOI: 10.1061/(ASCE)EY.1943-7897.0000081. (C) 2012 American Society of Civil Engineers.
In this paper, a novel theoretical analysis is carried out for evaluating the thermal performance, exergy efficiency, and energy efficiency for a typical cylindrical solar water heater under given operating conditions. In this detailed mathematical modeling, a cylindrical coil tube in the shape of spiral rings, serves as a collector to the incident solar energy on the cylinder wall. The energy balance equations for both the fluid and tube have been established separately. The physical parameters that govern the system are identified. The governing differential equations have been solved for various values of the parameters. Because it is difficult to determine these parameters through experiments, the nondimensional theoretical approach has been applied in this research. Finally, the influences of these parameters on exergy and energy efficiency, which are the most significant factors in the design of a cylindrical solar water heater, are investigated. The results of this theoretical analysis are in good agreement with the experimental measurements noted in the previous literature. The energy efficiency and exergy efficiency of the heater will be above 50 and 2%, respectively, after optimizing the key parameters. DOI:10.1061/(ASCE)EY.1943-7897.0000075. (C) 2012 American Society of Civil Engineers.
The first passive house (PH) was built in Germany in 1991. Since then several empirical design solutions have been developed, meeting the requirements of the PH standard proposed by the Passive House Institute (PHI) of Darmstadt, Germany. These design solutions have spread throughout central and western Europe and tend to be implemented in areas with a quite different climate than Germany's, such as southeastern Europe. This paper focuses on the question of whether the German design solutions would ensure the fulfillment of PH standard requirements in the latitudes of Romania. The paper compares general climate conditions for 22 towns in Germany and Romania. Further analysis is performed by estimating the energetic performance of a prototype passive building located in any of those 22 towns. The prototype passive building is AMVIC PH built in 2008 in Bragadiru (near Bucharest, Romania). It appears that the design solutions developed in Germany may be relaxed (for example, the thermal insulation may be reduced) when implemented for latitudes lower than 45 degrees N. DOI:10.1061/(ASCE)EY.1943-7897.0000066. (C) 2012 American Society of Civil Engineers.
Energy harvesting from ambient vibrations in civil structures provides a potential permanent power source for sensor networks used in structural health monitoring. These structures exhibit a narrow, natural frequency-response range, which is generally one to two orders of magnitude lower than the operating frequency spectrum of most piezoelectric-scavenging devices. This considerably limits the levels of harvestable power and thus hinders the implementation of advanced sensing functionalities. In this paper, the improvement of the energy-harvesting characteristics of a bimorph cantilever lead zirconate titanate (PZT) piezoelectric beam is studied. The application of a variable prestress-loading condition is used as a solution to modify the system's properties. A generalized model that takes into account all the vibration-mode shapes of the beam and the back-coupling effect is derived using the Hamiltonian principle. The model describes the effect of the prestress parameters on the harvestable energy levels. An analysis of the variations of the frequency response, amplitude, damping ratio, and efficiency of the device with respect to the preload is presented. Experimental verification of the model is also performed. The time and frequency domain responses of the piezoelectric bimorph are measured and compared with theoretical results. Measured acceleration from a concrete bridge deck under ambient loading and recordings from extreme events (earthquakes) are used to show the variations of the harvested power with respect to different prestress conditions. DOI: 10.1061/(ASCE)EY.1943-7897.0000077. (C) 2012 American Society of Civil Engineers.
The discusser would like to express his appreciation to the authors Glasnović and Margeta (2010) for presenting a possible way to establish sustainable electric energy system in Croatia.The discusser, however, would like to add few points and some literature references that might be of interest for readers.Of the total energy consumed in Croatia, approximately 47% originates from petroleum and petroleum derivatives, 22% from gas, 13% from hydro-energy, 7.5% from coal, 5.5% from nuclear energy, while other sources account for 5% (Feretić et al., 1999).One third of the total energy consumed is transformed into electrical energy.Hydroelectric power plants cover approximately 28.3% of the electricity production (after Boţiĉević Vrhovĉak et al., (2006) between 40% and 60% which depending on the hydrological conditions), followed by thermal power plants with approximately 21.4% (from coal 7.7%, oil 5.5% and natural gas 8.2%) and nuclear power plants with approximately 10.4% (Saner et al., 2010).As seen in Boţiĉević Vrhovĉak et al. (2006), total installed capacity in Croatian electric power system is 4GW (52% in hydro, 29% oil, 8% in nuclear, 8% in coal and 3% in gas).Electricity consumption is about 15 TWh (Schneider et al., 2007).Croatia has a strong but not very efficient co-generation sector,
