Peak Load Capacity Research Articles

Increasing nuclear power at liberalised energy markets- case Finland

Several Finnish projections for future electricity demand and the need for peak load capacity indicate a demand growth of about 2 GW from the present to the year 2030. The retirement of existing fossil fuel plants and old nuclear power plants will cause increased net import needs during 2020's, even when assuming additional energy efficiency measures and the commissioning of two new nuclear power plants recently approved by the Finnish Parliament. By the year 2030, the need for additional new capacity will be about 6 GW. The increased dependence on import is in contradiction with the official Government targets. This situation is not unique to Finland, but rather is likely to be the case in many other European countries as well. Both the energy company Fortum and energy-intensive industry in Finland see nuclear energy as a viable future generation technology. We describe the « Mankala » concept which is successfully used to build new nuclear capacity at liberalised electricity market in Finland.

Crack-damage mitigation and flexural behavior of flexure-dominant reinforced concrete beams repaired with strain-hardening cement-based composite

This paper presents experimental and analytical studies on the cracking behavior and flexural performance of reinforced concrete (RC) beams repaired with strain-hardening cement-based composite (SHCC). Test results demonstrated that RC beams repaired with SHCC showed no concrete crushing or spalling until final failure, but showed a great number of hair cracks, while non-repaired RC beam failed due to crushing. It was noted that the SHCC matrix can improve crack-damage mitigation and the flexural behavior of RC beams, such as moment strength, ductility after peak load and energy dissipation capacity. In the fiber section analysis, the idealized tensile stress–strain curve for the SHCC based on a four-point model was similar to the test result, and it was confirmed that monotonic analytical moment–curvature curves were well-fitted to the experimental moment–curvature curves. Based on the parametric analysis results, it was noted that the curvature of the RC beam was more affected by the matrix ductility of the SHCC than the moment strength.

Signaux-prix et équilibre de long terme : reconsidérer les formes d’organisation sur les marchés de l’électricité

The decentralised electricity market model illustrates several market flaws in the linkage between short-term and long-term decisions. Because of highly specific problems of risk management and market incompleteness, the model does not allow effective allocation of investment in base-load and peak-load capacities leading to an optimal generation system. This makes it necessary to (1) establish regulations to provide a credible basis for remunerating generation capacity, so as to create incentives for investment in peak-load units ; (2) accept vertical arrangements enabling operators to share risk with consumers, even if these arrangements constitute market imperfections that will constrain competition.

Photovoltaic (PV) electricity: Comparative analyses of CO 2 abatement at different fuel mix scales in the US

Photovoltaic electricity has the potential to mitigate CO 2 emissions from the grid. A methodology to more accurately evaluate CO 2 abatement by PV electricity is developed. We develop a capacity factor based dispatching model to evaluate marginal abatement in the load zones of ERCOT and CAISO, and compare it to the abatement using national, regional and state average resource profiles. The average cases over-estimated and under-estimated CO 2 abatement in ERCOT and CAISO, respectively. Marginal abatement was lower by 17% than the average cases in ERCOT, due to the predominant displacement of the low carbon natural gas plants at the margin. In CASIO, marginal abatement was higher (1.3–2.4 times) than that of the average cases due to the displacement of highly inefficient gas plants at the margin. We demonstrate that actual CO 2 abatement of PV electricity is dependent on both peak load resources and capacity of installations. Subsequently, we develop a CO 2 indicator that can be used as a guideline for selecting PV installation sites to derive maximum abatement. Installing photovoltaics in regional areas of MRO, SPP and RFC was determined to be most beneficial. The results of this study can guide energy planning and CO 2 mitigation policy-making using photovoltaics in the future.

FUEL CELL HEAT RECOVERY, ELECTRICAL LOAD MANAGEMENT, AND THE ECONOMICS OF SOLAR-HYDROGEN SYSTEMS

Computer modelling of a solar-hydrogen system to supply heat and power to a remote household in southeast Australia has been conducted. The electrical load management and heat recovery from the fuel cell have been investigated to improve the system's economy. The results reveal that the cost of the solar-hydrogen system can be reduced by over 10% by effectively managing the peak load demand and capacity of the fuel cell while keeping the average daily electrical energy supplied at the same level. Interestingly, increasing the size of the fuel cell up to a certain level above the minimum required actually lowers the average unit cost of energy supplied because the fuel cell operates at lower current densities and hence gives better efficiency. A smaller photovoltaic (PV) array, electrolyser and hydrogen tank are then required as well. Heat recovered from the fuel cell and its utilization to substitute for LPG in a domestic hot water unit could lead to a further reduction in the overall energy costs of the household. While the recoverable heat available was found to be lower if optimal load management is also applied, there remained a net economic benefit of supplying both heat and power from a solar-hydrogen system.

Fracture-Based Method to Determine Flexural Capacity of Concrete Beams on Soil

ABSTRACT A method to predict the fracture response of concrete beams utilizing cohesive crack elements was expanded from a three-point bending beam to a beam on soil boundary condition. The simulations were compared with monotonic three-point bending beam and beam on soil tests, verifying the cohesive elements with a bilinear softening curve defined by the concrete's fracture and tensile strength properties can effectively predict the flexural capacity and post-peak behavior of both specimen configurations. Vertical and horizontal springs idealized the soil support to the beams. Whether the springs were linear or nonlinear elastic had a limited effect on the peak load capacity of the concrete beams on soil. At pre-peak and peak load levels, the two concrete beam configurations had similar stress patterns and crack propagation levels in spite of the different boundary conditions. The method simplicity and accuracy under different boundary conditions offers a promising approach that can be extended to predicting the flexural capacity of concrete slabs.

Structural Performance of Stapled Wood Shear Walls Under Dynamic Cyclic Loads

Wood shear walls are the most common element in the lateral force-resisting system of residential construction. Recent developments have made the use of staples, as a sheathing-to-stud connection, much more feasible and practical. Dynamic cyclic tests of wood shear walls using staples as connectors of sheathing to the studs were performed to determine load and displacement capacities. Enhanced details from standard construction were used to improve the performance of the global system including a double sill plate, a new refined panel corner detail, double staples along blocked edges, and backup bolts for hold-downs. At the strength level, the stapled wood shear walls with enhanced details performed above the International Building Code-IBC (ICC 2006) regarding peak load capacity; however, peak drift capacity was 88% of the specified capacity. The test results were used to determine acceptance criteria, which were compared to the ASCE 41-06 Standard for Seismic Rehabilitation of Existing Buildings (ASCE 2007).

Plastic Hinging Collapse of Periodic Cellular Truss Cores

Periodic cellular metals (PCMs) have considerable potential as a new type of hybrid material for sandwich panel cores, due to their high architectural efficiency and load-bearing capability at relatively low mass. The mechanical performance of these materials is controlled by both architectural and microstructural parameters. In the case of PCM struts that have intermediate slenderness ratios, the peak load capacity is determined by the inelastic buckling stress, in which the rotation of the strut ends is opposed by their plastic hinging resistance. Strut rotation is, therefore, a key component of the overall PCM failure mechanism. In the present study, a method is developed for measuring the plastic hinging strength by allowing the truss core nodes to spread radially outward during collapse. Both finite element (FE) and experimental methods were used to study this behavior in AA3003 truss cores; the effect of work hardening, interfacial friction, and specimen size was examined. Direct measures for the plastic hinging resistance can be obtained and it was possible to demonstrate that while work hardening during PCM stretch-forming fabrication introduces significant work hardening in the near-hinge region, not all of the strengthening is available to resist plastic hinging collapse by virtue of the Bauschinger effect.

La sécurité de l'approvisionnement électrique

Résumé Les évolutions récentes des prix sur les marchés de l’électricité ne posent pas seulement des problèmes liés à leur forte augmentation, mais aussi, et surtout, à leur extrême volatilité. Celle-ci perturbe les signaux de prix adressés aux investisseurs et peut conduire à un sous-investissement socialement préjudiciable pour la sécurité de l’approvisionnement électrique. Les risques sont d’autant plus élevés que les unités de production appelées à satisfaire les pointes de demande ne peuvent couvrir leurs coûts que durant de courtes périodes de temps. Ceci suppose d’accepter des phases de valorisation extrême des prix de marché. Or, la difficulté de déterminer si celles-ci ne sont pas liées à l’exercice de pouvoir de marché peut conduire à des interventions publiques, notamment sous la forme de plafonds de prix. Ces dernières peuvent accentuer la tendance au sous-investissement des firmes. En effet, de telles interventions ont non seulement pour effet direct de supprimer les rentes de rareté, mais elles ont aussi pour conséquence de créer un sentiment d’insécurité juridique. Celle-ci sera d’autant plus significativement ressentie que la réglementation du secteur est en constante évolution et donc imparfaitement prévisible pour les entreprises. L’analyse des différents mécanismes pouvant être mis en œuvre pour pallier l’insuffisance de l’investissement spontané des firmes, tels les mécanismes d’obligation de capacités, de paiements de capacités ou des marchés de capacités, permet de s’interroger sur la complémentarité nécessaire de l’initiative privée et de l’action publique pour garantir la sécurité de l’approvisionnement électrique.

Efficiency analysis of German electricity distribution utilities – non-parametric and parametric tests

This study applies non-parametric and parametric tests to assess the efficiency of electricity distribution companies in Germany. Traditional issues in electricity sector benchmarking are addressed, such as the role of scale effects and optimal utility size, as well as new evidence specific to the situation in Germany. Labour, capital, and peak load capacity are used as inputs, and units sold and the number of customers as output. The data cover 307 (out of 553) German electricity distribution utilities. A data envelopment analysis (DEA) is applied with constant returns to scale (CRS) as the main productivity analysis technique, whereas stochastic frontier analysis (SFA) with distance function is the verification method. The results suggest that returns to scale play but a minor role; only very small utilities have a significant cost advantage. Low customer density is found to affect the efficiency score significantly, in particular in the lower third of all observations. Surprisingly, East German utilities feature a higher average efficiency than their West German counterparts. The correlation tests imply a high coherence of the results.

Deformation capacity of RC piers wrapped by new fiber-reinforced polymer with large fracture strain

One of the major drawbacks of structure strengthening by fiber reinforced polymer wrapping using materials such as CFRP and AFRP, whose strength and stiffness are high, is the brittle nature of failure mode, which is caused by fracture of the fiber due to low fracturing strain. A series of experiments were conducted to investigate the efficiency of using two new types of fibers, polyethylene naphthalate (PEN) and polyethylene terephthalate (PET) fiber, for seismic strengthening of RC piers. These fibers have the properties of low stiffness and high fracturing strain. Specimens strengthened by PET and PEN fiber sheets wrapping showed considerable improvement in shear capacity and ductility compared to the control specimen. Both PET and PEN showed no tendency to fiber breakage before the pre-defined ultimate deformation. Pier behaviors such as shear deformation and strain development in both fiber and steel shear reinforcement, and the piers, ultimate failure modes, were carefully examined. Shear deformation increases rather rapidly after peak load and concrete shear capacity decreases with the increase in shear deformation. Stiffness of fiber affects the development of shear deformation and the descending branch of the load–deformation curve after the peak load. A simple model to predict the piers deformation capacity, based on the experimental results, was proposed.

05/01588 Modeling technology adoption as an irreversible investment under uncertainty: The case of the Turkish electricity supply industry

This paper studies energy conversion technology adoption in the electricity supply sector from the perspective of irreversible investments under uncertainty, and with a particular interest in environmental sustainability. We develop a dynamic technology adoption model that is firmly rooted in economic theory and that takes important determinants of optimal investment in available technologies (e.g. life-cycle capital and operation cost) explicitly into account. Uncertainty is introduced for the demand for peak-load capacity, unit generation costs, and for the average electricity price. We test the model empirically by applying it to data for the Turkish power supply industry. The model-guided optimal investment results based on net present value considerations exhibit significant deviations from the actual investment outcome. We find that the increased adoption of natural-gas-fired power generation technologies in Turkey in recent years, while contributing to environmental sustainability, has had doubtful merits from an investor’s perspective.

Modeling technology adoption as an irreversible investment under uncertainty: the case of the Turkish electricity supply industry

This paper studies energy conversion technology adoption in the electricity supply sector from the perspective of irreversible investments under uncertainty and with a particular interest in environmental sustainability. We develop a dynamic technology adoption model that is firmly rooted in economic theory and that takes important determinants of optimal investment in available technologies (e.g., life cycle capital and operation cost) explicitly into account. Uncertainty is introduced for the demand for peak-load capacity, unit generation costs, and for the average electricity price. We test the model empirically by applying it to data for the Turkish power supply industry. The model-guided optimal investment schedule based on net present value considerations exhibits significant deviations from the actual investment outcome. We find that the increased adoption of natural-gas-fired power generation technologies in Turkey in recent years, while contributing to environmental sustainability, has had doubtful merits from an investor's perspective.

Kapazitätsdimensionierung durch aktivitätsorientiertes Kostenmanagement am Beispiel eines Fernsehanbieters

Broadcasting companies — whether public or private — face increasing cost pressure. This paper develops a case study that uses information about activity-based cost of used and unused capacity in order to economize on labor and materials costs. The driving choice variable is the adjustment of excess (peak-load) capacity. We show that activity-based cost management performs well for materials cost but less well for labor cost. This is due to the fact that broadcasting companies typically mix of employees and freelancers.

Zoledronic acid improves the mechanical properties of normal and healing bone

Objective. To determine the effects of the bisphosphonate zoledronic acid on the mechanical properties of normal and regenerating bone in a rabbit model of distraction osteogenesis. Background. Bisphosphonate therapy is used for treating osteoporosis and, more recently, to enhance bone healing and reduce stress-shielding osteoporosis in distraction osteogenesis. Methods. Thirty eight rabbits underwent 14 days of distraction osteogenesis on the right rear limb. They received either zero, one or two doses of intravenous zoledronic acid. Four point bending tests were performed to collect mechanical data. Results. The peak load capacity of the regenerating bone was significantly increased by bisphosphonate therapy, but a similar trend in normal bone was not significant. The energy absorbed to failure did not vary significantly in either group. Conclusions. These data suggest that bisphosphonate therapy has a beneficial effect on the load capacity of regenerating bone, without increasing the brittleness of either new or existing bone. Relevance Zoledronic acid administration may be a potentially valuable adjunct to distraction osteogenesis treatment, to enhance bone strength, thus reducing refracture complications.

Compatibility requirements for yield-line mechanisms

Yield-line analysis proves a powerful and convenient method for establishing the peak load capacity of reinforced concrete slabs. Its application requires compatible mechanisms to be postulated, comprising rigid regions intersecting at yield-lines where relative rotations may occur. A systematic procedure is described for checking the compatibility of postulated yield-line mechanisms. The similarity between this method and equilibrium requirements in a plane pin-jointed truss is highlighted, and an analogy between yield-line mechanism compatibility and statical determinacy in pin-jointed trusses is established.

Behaviour of round steel fibre reinforced concrete panels under point loads

The objective of this investigation was to examine methods of testing round Steel Fibre Reinforced Concrete (SFRC) panels to obtain empirical estimates of post-crack load capacity under point loads. The performance of steel fibre reinforced concrete panels under point loads is of interest because such tests are commonly used to determine the suitability of a concrete mix for use in sprayed tunnel lining construction. This investigation has focussed on experimental obstacles to the reliable determination of post-crack load capacity. To examine possible differences in behaviour between continuousin situ tunnel linings and specimen panels representing portions of a lining, four modes of edge support were used to restrain round specimens that varied in both thickness and diameter. Determinate and simple support conditions were examined as possible modes of panel support for routine laboratory testing. Fully clamped and quasi-continuous edge restrained panels were used as approximations of anin situ lining. Performance was measured in terms of peak load capacity and energy absorption.

Response of Reinforced Concrete Beams at High Strain Rates

A closed-loop servohydraulic testing machine was used to conduct rate tests on reinforced concrete beams. Seven pairs of singly reinforced beams (without shear reinforcement) were tested under displacement control. From each pair, one beam was tested at a rate (piston velocity = 0.00071 cm/sec) and the other at a high rate (piston velocity = 38 cm/sec). The total number of cracks reduced significantly at the rate. Peak load and energy absorption capacity were found to increase with the rate of straining. For three of the pairs tested, final failure mode shifted from shear failure at the static rate to flexural failure at the rate. This phenomenon is the opposite of the brittle transition in the mode of failure reported by some other researchers.

Diaphragm replacement: An experimental animal study

We performed an open experimental study for evaluation of rapidly absorbable material of bovine serosa for diaphragm replacement. A total of 100 Sprague-Dawley rats were randomly assigned to five groups of equal size. In the control group (n=20) incision of the diaphragm was followed by primary suture. The animals of the four other groups underwent partial resection of the left hemidiaphragm. The defects were repaired by lyophilized dura, polytetrafluorethylene (PTFE), autologous transversus muscle or rapidly absorbable bovine serosa. We performed electromyography (EMG) and postmortem physical examinations of elasticity and load capacity of the different materials as well as histologic examinations after three and six months. A total of 89 animals survived and were subject to the analysis. There were no differences between the groups concerning growth and weight gain. The EMG showed normal function for the absorbable material and the transversus muscle. Only scanty physiologic waves were registered in the PTFE group. Load capacity measurements showed the lowest value of 4.71 N for the native diaphragm; all other materials had much higher values (17.66 N – 51.99 N) with a peak load capacity in the PTFE group. Measurements of elasticity displayed similar results. The native diaphragm had the lowest value (1516 N/m); much higher values were found in all the other materials tested (3905 N/m – 7654 N/m) with again peak values for PTFE. The differences of all materials compared to native diaphragm were statistically significant (p<0.05). The histologic examinations revealed strong foreign body reactions in the dura and PTFE groups. The absorbable bovine serosa had vanished three months postoperatively. Short-term absorbable bovine serosa tested successfully as a partial replacement of the diaphragm in this experimental study on rats. There may be additional indications for this material if a temperary replacement is intended.

“New for old”: an argosy of power returns to Connah's Quay

The amount of natural gas now being used for electricity generation has risen from virtually nil in 1989 to around 16% of the total fuel used in the UK today. In 1996, use of gas at CCGT stations saw a 37% rise in electricity production. Didcot A power station, designed for coal burning, has seen one of its units now burning natural gas and other conversions are already underway. A great fillip to the use of gas turbines for power generation came in 1963, resulting from the cascade tripping of a major part of the south-east network. As a consequence, nearly all power stations today have gas turbines installed to support generation and to provide sufficient auxiliary power for a “black start”, as well as useful peak load capacity. However, this was a safety policy undertaken by the CEGB and the gas turbines installed were not utilised for wholesale electricity production. The &apos;dash for gas&apos; campaign did not arrive until electricity privatisation came into being after the passing of the Electricity Act of 1989. This article examines the development of natural gas for the new CCGT technology by looking at one interesting case, Connah&apos;s Quay. It describes how the technology is replacing what was once the only widely accepted means of electricity generation in Britain, namely coal. The history of the Connah&apos;s Quay site is given including demolition of the old power station and construction of the new including its layout and operation.