Average Load Factor Research Articles

Utilization Rates of Geostationary Communication Satellites:Models of Loading Dynamics

The case can be made that a key metric for the commercial space communication sector is the utilization rate, or load factor, of a satellite or a fleet of satellites. In this paper, we first discuss average load factors of fleet of satellites, and then propose that the loading of a single satellite can be modeled as a stochastic process. To illustrate our proposition, we collected and analyzed load factor data of 20 one communication satellites launched between 1980 and late 1990s. We conducted time series analysis and built analytical models for the evolution of utilization rates, or loading dynamics, of a communication satellite. We found consistent results that exhibit three different loading patterns, with a load factor ramp-up, a steady-state load factor during the service life of the satellite, and a decline in load factor after several years of on-orbit service. We further discuss these results and the factors that drive satellite loading dynamics, from the supply/demand (im)balance of on-orbit bandwidth to customer churn from aging transponders and switching towards newer more powerful units. Results should prove useful to satellite operators and industry observers; they also improve the forecast for determining financially optimal satellite design lifetimes.

Substantiation of a lower estimate for the bunker inventory: Comment on “Updated emissions from ocean shipping” by James J. Corbett and Horst W. Koehler

Substantiation of a lower estimate for the bunker inventory: Comment on “Updated emissions from ocean shipping” by James J. Corbett and Horst W. Koehler

Potential of Hydroelectric Energy

The objective of this article is to investigate the status of hydraulic power plants (HPPs) in Turkey as of the end of 2000. Hydro-resources meet approximately 41% of Turkey's total installed capacity for electric power generation, while 25% of total electricity is generated from HPPs. 128 HPPs belonging to the Turkish Electricity Generation and Transmission Cooperation (TEAS) and its affiliated partnership produce 74.6% of total electricity. Turkey's average load factor is 31.6% while the net unit generation cost is 0.20 cent/kWh. The use of hydro, especially for power generation, is very essential to the continued economic growth of Turkey. Hydraulic electric potential has been estimated to be about 123 TWh for a year with normal hydrological conditions. This hydraulic potential has been concentrated in mainly 26 basins. 25% of total potential has been utilized via HPPs already in operation and construction is in the works for an additional 10% potential. In addition, hydroelectric energy potentials, which has not been utilized, have also been investigated in this study.

Feasibility study on hydrogen refueling infrastructure for fuel cell vehicles using the off-peak power in Japan

It is examined that the technical feasibility, economics of hydrogen, improvement of the load factor and reduction of the carbon dioxide emission in the case where a hydrogen-refueling infrastructure is developed using the off-peak power in the existing electrical power grid in Japan. Hydrogen could be supplied to the fuel cell vehicles, of which cost would be almost the same as the current retail cost of gasoline exclusive of tax. Annual average load factor of 0.72% could be increased in 2020 to meet the hydrogen demand for the fuel cell vehicles in Japan by water electrolysis. The infrastructure cost of 0.12 trillion yen/year in 2020 would be necessary to be invested, which is almost the same as the reduction of annual expenses in the case where the increase of 1% in load factor could attain. Fuel cell vehicles using the electrolysis, hydrogen generated by the off-peak electricity could attain the 37% reduction of carbon dioxide emission compared with middle-sized internal gasoline combustion passenger cars.

Thermal Power Plants in Turkey

The objective of this article is to investigate the status of thermal power plants (TPPs) in Turkey as of the end of 2000. Thermal resources meet approximately 60% of Turkey’s total installed capacity for electric power generation, while 75% of total electricity is generated from TPPs. Of the total thermal generation, natural gas accounts for 49.2%, followed by coal for 40.65%, and 9.9% for liquid fuel. Nineteen TPPs belonging to the Turkish Electricity Generation and Transmission Cooperation (TEAS) and its affiliated partnership produce 74.6% of total electricity. Turkey’s average load factor is 61%, while the net unit generation cost is 4.19 cent/kWh. The availability of low-grade lignites in the country has led to the construction of lignite-fired TPPs. The use of coal, especially for power generation, is very essential to the continued economic growth of Turkey. However, advanced clean coal technologies should be considered for improving the environmental performance of coal combustion.

Effectiveness of gain control in EDFAs against traffic with different levels of bursty behaviour

Previous publications have addressed the impact of bursty, self-similar traffic on erbium-doped fibre amplifiers (EDFA). Several gain control techniques have been suggested to combat the gain fluctuations of EDFA with this type of traffic. The effectiveness of two such methods are investigated, namely highly inverted amplifiers and all-optical gain clamping, while varying the parameters characterising the burstiness of the sources. While previous publications have focused on the effect of the average load or activity factor, the paper further investigate the dependence on the relative variability of the packet burst lengths (ON times), and lengths of the interburst idle times (OFF times). Both gain control methods reduce the output power and signal-to-noise ratio excursions with respect to a standard amplifier chain. The authors find that, for an eight channel WDM system and a cascade of six EDFAs, all-optical gain clamping can reduce the variations by a factor of five, provided adequate power is present in the clamping laser, while highly inverted amplifiers have variations reduced by a factor of two. The authors find that, in a clamped chain, the source activity factor does not uniquely determine the required level of lasing power. The authors also deduce that information on the relative variability of ON and OFF times is essential.

Incorporating load factor into the scheduling of soft real-time transactions for main memory databases

Many real-time applications have very tight time constraints which couldn't be met by disk resident databases. For those applications, main memory database where entire database is stored in main memory is the proper choice. It has been shown that coarse-granule locking is better than fine-granule locking for main-memory databases. Coarse-granule locking makes it easy to extract data access patterns correctly from canned transactions of main memory real-time database systems. In this paper, we propose two real-time transaction scheduling algorithms — CCA-ALF (Cost Conscious Approach with Average Load Factor) and EDF-CR-ALF (Earliest Deadline First-Conditional Restart with ALF) — which use both static (e.g., deadline) and dynamic information (e.g., system load) for main memory databases by utilizing data access patterns of transactions. We compare the performance of those algorithms with CCA and EDF-HP which do not use system load information at all. Our simulations on main memory databases indicate that: i) CCA-ALF is better than EDF-HP, CCA, and EDF-CR-ALF in terms of miss percent and mean lateness, and ii) CCA-ALF adapts well to the changes in the system load.

BWR 90—the advanced BWR of the 1990s

The future global role of nuclear power will be determined by its ability to provide economical and safe energy. Nuclear power, like any other substantial contributor to the world's energy needs, must be generated at an acceptable cost and with negligible environmental effects. Besides, it must achieve and maintain a socially reasonable level of public acceptance, which in turn is not necessarily governed by rational assessments of the true safety and environmental impact of nuclear power. The ABB Atom approach to this situation can best be characterized as a `cautious evolution'; for the next decade the company will largely base its offerings to the market on its `evolutionary' light water reactor design, the BWR 90. This design builds closely on the experience from successful construction and operation of its predecessor, the BWR 75 design. In 1995 and 1996, plants of this design achieved an average load factor greater than the 87% set by EUR; the two BWR units at Olkiluoto in Finland are among the very best performing plants in the world, with an average load factor of 94% over the last 7 years. The continued LWR design development focuses on meeting requirements from utilities as well as new regulatory requirements. A particular emphasis is put on the consequences of severe accidents; there shall be no large releases to the environment. Other design improvements involve: all-digital I and C systems and enhanced human factors engineering to improve work environment for operators, optimization of buildings and containment design to decrease construction time and costs, and selection of materials as well as maintenance and operating procedures to even further reduce occupational radiation exposures. Probabilistic safety assessments and life-cycle cost evaluations have become major tools in the design optimization work. The BWR 90 was offered to Finland in the early 1990s, and will now as the first BWR design be reviewed by a number of European utilities with respect to its conformance to the European Utility Requirements (EUR); a specific EUR Volume 3 for the BWR 90 will be the final result. The paper describes some of the unique characteristics of the BWR 90, with emphasis on the features that are most important for achieving improved economy and enhanced safety.

LH*—a scalable, distributed data structure

We present a scalable distributed data structure called LH*. LH* generalizes Linear Hashing (LH) to distributed RAM and disk files. An LH* file can be created from records with primary keys, or objects with OIDs, provided by any number of distributed and autonomous clients. It does not require a central directory, and grows gracefully, through splits of one bucket at a time, to virtually any number of servers. The number of messages per random insertion is one in general, and three in the worst case, regardless of the file size. The number of messages per key search is two in general, and four in the worst case. The file supports parallel operations, e.g., hash joins and scans. Performing a parallel operation on a file of M buckets costs at most 2 M + 1 messages, and between 1 and O (log 2 M rounds of messages. We first describle the basic LH* scheme where a coordinator site manages abucket splits, and splits a bucket every time a collision occurs. We show that the average load factor of an LH* file is 65%–70% regardless of file size, and bucket capacity. We then enhance the scheme with load control, performed at no additional message cost. The average load factor then increases to 80–95%. These values are about that of LH, but the load factor for LH* varies more. We nest define LH* schemes without a coordinator. We show that insert and search costs are the same as for the basic scheme. The splitting cost decreases on the average, but becomes more variable, as cascading splits are needed to prevent file overload. Next, we briefly describe two variants of splitting policy, using parallel splits and presplitting that should enhance performance for high-performance applications. All together, we show that LH* files can efficiently scale to files that are orders of magnitude larger in size than single-site files. LH* files that reside in main memory may also be much faster than single-site disk files. Finally, LH* files can be more efficient than any distributed file with a centralized directory, or a static parallel or distributed hash file.

Effect of Overloaded Heavy Vehicles on Pavement and Bridge Design

A large number of infrastructure projects have been undertaken in Taiwan in recent years because it is a developing country. These large-scale constructions have caused rapid growth in the number of heavy vehicles in service, as well as a dramatic increase in the size and weight of heavy vehicles. A very serious truck overloading problem has resulted, which significantly affects pavement performance and bridge safety. In the described study, weigh-in-motion (WIM) equipment was introduced to Taiwan's freeway systems. After data collection and analysis it was found that the average truck load factor for combined heavy vehicles computed from the WIM data collection was 2.7 times higher than the original design value, which already took into account 30 percent truck overloading. It was also found that computed axle load ratios for various types of heavy vehicles were dramatically different from the ratios given in the bridge design standard specification. Bridge deck designs for a simply supported bridge were studied. It was concluded that the current bridge design standard specification will result in a 28 percent underestimation of steel volume in bridge deck design.

Effect of Overloaded Heavy Vehicles on Pavement and Bridge Design

A large number of infrastructure projects have been undertaken in Taiwan in recent years because it is a developing country. These large-scale constructions have caused rapid growth in the number of heavy vehicles in service, as well as a dramatic increase in the size and weight of heavy vehicles. A very serious truck overloading problem has resulted, which significantly affects pavement performance and bridge safety. In the described study, weigh-in-motion (WIM) equipment was introduced to Taiwan's freeway systems. After data collection and analysis it was found that the average truck load factor for combined heavy vehicles computed from the WIM data collection was 2.7 times higher than the original design value, which already took into account 30 percent truck overloading. It was also found that computed axle load ratios for various types of heavy vehicles were dramatically different from the ratios given in the bridge design standard specification. Bridge deck designs for a simply supported bridge were...

Potential Installed Thermal Power of Direct Uses of Geothermal Energy in Japan

In this paper it is attempted to estimate potential installed thermal power of direct uses of geothermal energy in Japan by computing extractable heat from only existing thermal springs distributed all over the country, under the presumption that no geothermal well is newly drilled. Since the Japanese enjoy the pleasures of natural baths, direct uses of geothermal energy in Japan are required to coexist with bathing. Then, potential installed thermal power is estimated at 2,797.46 MW under some conditions for coexistence and coprosperity with bathing. However, some disqualifying factors and the average load factor may reduce this value by 530 MW, which will be yet about five times large than the present thermal energy used of 104.69 Mw. THe oil saved will be up to 0.35% of national consumption.

Exhaust emissions from work machinery in Finland

This study mapped work machines having internal combustion engines that are used in Finland. The aim of the study was to clarify the number and average engine power of machines in use, their annual operating hours, and their loading properties, in order to calculate the exhaust emissions from these machines. The numerical data were gathered from sales figures, vehicle registration, and statistics on production, import, and export. The average load factor was evaluated on the basis of the real fuel consumption in comparison to nominal fuel consumption. Data on the duration operation are based on the number of working hours and the results of earlier studies. There were about 400 000 diesel engined machines in Finland in 1990. The most common types of machines are agricultural tractors, construction machines, and combine harvesters. The total fuel consumption of diesel machinery was 780 000 m 3 accounting for about 30% of the total amount of diesel fuel consumed in traffic. Nitrogen oxide emissions came to 41 million kg, which is 15% of all nitrogen oxide emissions in Finland. Other studied compounds—unburned hydrocarbons, carbon monoxide, and particulate matter—accounted for 5–10% of all emissions in Finland.

Direct uses of geothermal energy in Japan

The purpose of this review is to outline the present state of direct uses of geothermal energy in Japan as of April 1989. Firstly, the representative examples are briefly illustrated. Secondly, an analysis is carried out to characterize each application, with a diagram combining the inlet temperature with the flow rate of individual direct use facilities. Finally, the total installed thermal power and the total thermal energy used are estimated at 171 MWt and 107 MWt yr, respectively, resulting in a total average load factor of 63%. The oil saved by geothermal direct uses is also evaluated at 0.06% of national consumption.

U.S.A. experience in direct heat use

Direct heat use of geothermal energy in the U.S.A. occurs mainly in the western states. A total of 216 projects is operational, with six under construction and 21 planned. The operational projects account for about 2100 TJ/yr (233 MWt-peak) with an average load factor of 29%. The under-construction and planned projects would approximately double the energy use. Not included are an estimated 10,000 TJ (400 MWt-peak) used in enhanced oil recovery. Space and district heating account for almost half (45.8%) of the annual use, whereas greenhouses account for 20.2%, fish farming for 20.7%, industrial processing for 6.7%, and pools and spas for 6.6%. Future growth is expected to be greatest in district heating, where eight proposed projects will produce 1360 TJ annually (149 MWt-peak). Future growth of all direct heat uses in the U.S. is estimated at 8% annually.

A case for domestic electrical load management

SYNOPSIS There is, nowadays, an increasing social awareness of the need to make better use of all our resources, and one of these resources is our extensive investment in electricity generation and distribution systems. At the present time such systems have sufficient capacity to cope with maximum peak loads that occur infrequently and only for short periods. The average load factor is significantly below unity. Furthermore, as the demand for power inevitably increases, the capacity of the supply and distribution systems simultaneously have to be enlarged to maintain this margin of excess capacity. A case is presented here for the use of existing technology to facilitate a gradual transition to a more cost effective basis for electricity consumption and supply. The basis of the proposed method lies in domestic load management. A research team of architects and engineers is suggested.

Multiproject scheduling: Analysis of scheduling strategies under unequal delay penalties

AbstractThe multiproject scheduling problem is investigated under the assumption that delays corresponding to different projects carry different penalties. Five penalty functions are introduced that simulate typical business behavior. These are: 1) assigning the highest penalty to the project requiring the greatest amount of resources; 2) assigning the highest priority to the longest project; 3) assigning the highest priority to the project requiring the least amount of resources; 4) assigning the highest priority to the shortest project; and 5) random assignment. Justification for each case is provided.Two powerful project summary measures were used to generate the test problems. The first measure, average resource load factor (ARLF), identifies whether the location of the peak requirement of all (i.e., combined) resources is in the first or second half of the project's critical path. If each resource is expressed in terms of dollars, then ARLF identifies the location of the peak cash requirement. Since in practice the choice of the scheduling strategy is influenced by the location of the peak cash requirement, performance of the scheduling strategies is analyzed with respect to values of this measure. The second measure, average utilization factor (AUF), calculates the ratio of resource requirements to availabilities. It is shown that problems tested must have different AUF values in order to be classified different for purposes of experimental design. Thus a factorial model of the form, y = Strategy + Penalty + ARLF + AUF + ϵ was used to generate 385 problems, each requiring 2 to 4 resources, containing 3 to 5 projects and 34 to 63 activities.The computer program used in the study is based on a parallel method of scheduling in which priorities of the activities are determined when the activity is considered for scheduling. Ten scheduling strategies are tested. Some important ones are: 1) to schedule the shortest activity first; 2) to schedule the activity with minimum slack first; 3) to schedule the activity with maximum work content first (i.e., from the project with highest work content); 4) to schedule the shortest activity from the shortest project first; and 5) to schedule the activity with maximum penalty first. Shortest activity first and minimum slack first are popular strategies introduced by other researchers.Using number of times ranked first as our criterion, scheduling the activity with maximum penalty first provides the best results followed by the strategy of scheduling the activity with maximum work content. But when these results are analyzed with respect to existence of a very expensive project (i.e., dominance) in the problem, performance of the maximum penalty strategy improves. When the overall results are analyzed with respect to values of ARLF, a different picture emerges. Then the strategy of scheduling the activity with the highest penalty first provides the best results if the peak requirement is early. When the peak requirement is toward the middle of a project's unconstrained critical path, scheduling the activity with the highest work content provides the best results. When the peak requirement is late in a project's life, scheduling the shortest activity from the shortest project is the best strategy to adopt. These findings were tested for statistical significance by using nonparametric testing procedures and were found to be significant.

Flight Frequency Determination

An attempt has been made to determine the flight frequency between two cities. The economic effects achieved by the carrier using a particular flight frequency level is measured through the average load factor value. The level of service is measured by the absolute value of the average time difference between the actual and desired time of departure. It is shown that this time difference can be approximately expressed only in the function of flight frequency, without regard to the times of departure in the course of the day and that the error which occurs is not considerable. The interval in which the flight frequency should be located is also determined, as well as the corresponding interval of the average time difference between the actual and desired time of departure in order to achieve a profitable business. A numerical example illustrates the route Belgrade - Zagreb in Yugoslavia.

An Analysis of the Impact of Open Entry on Price and the Quality of Service in the Airline Industry

D URING the past three years there has been a gradual transition toward deregulation of the airline industry by the Civil Aeronautics Board (CAB) as originally proposed in the Federal Aviation Act of 1975 and finally enacted in the Airline Deregulation Act of 1978. This move is intended to allow for competitive pricing and freedom of entry and exit in the domestic airline markets during 1981. So far, the price competition has been restricted by the CAB to the offering of discount and standby fares. The impact on price has been a reduction in revenue per passenger mile from 8.24? in 1977 to 8.02? in June of 1979.1 Over this same period the quality of service has declined as measured by an increase in the load factor from 56.1% to 63.6%. This result is consistent with most predictions regarding the impact of price competition in this industry.2 Alfred Kahn (1978) has argued that price competition by itself would (and should) result in a variety of services for consumers but that it could reduce the average quality of service via higher load factors. Price competition is, however, only one dimension of a fully competitive airline market. While price competition will certainly tend to increase load factors, the effect of entry should be to lower them as firms compete through scheduling frequency. The interaction between these forms of competition produces a technical tradeoff between lower prices and higher quality of service and thus raises the question of what a truly competitive airline market will provide the consumer of airline services. This paper examines this intrinsic tradeoff between price and quality in the provision of airline service and analyzes the implications for a competitive airline industry. The presence of this tradeoff has been suggested in the theoretical models of Douglas and Miller (1974b) and DeVany (1975). In both models there is purported to be an inverse relation between the load-factor and the number of firms in a market due to scheduling competition and an inverse relation between the load-factor and the fare level due to profit-maximizing supply responses of firms serving the market.3 It is these theoretical propositions that produce a tradeoff between fare level and the quality of service and make the effects of competition in the typical airline market difficult to predict. Using these theoretical models as a basis, this paper develops an empirical analysis of the relation between fare level, open entry and the quality of service and its implications for a competitive airline market. This involves, first, estimating the equilibrium price and load factor which results from competition in a market with a fixed number of firms. Then, the independent effect of open entry on the competitive market outcome is identified by varying the number of firms and examining the capacity response due to scheduling competition. This analysis yields the zero-profit price and load factor for varying degrees of market concentration. JThe profitmaximizing and output-maximizing price-quality combinations are also generated for the same market conditions. A comparison of these alternative market solutions provides the basis for analyzing the inherent price-quality tradeoff in the provision of airline service and some insight into the nature of a fully competitive airline market. Crucial to the analysis proposed above is an empirical estimate of the supply response of firms serving a city-pair market to changes in Received for publication April 23, 1980. Revision accepted for publication April 15, 1981. University of Texas at Arlington and Southern University of New Orleans, respectively. I These figures are computed using data on domestic trunk carriers in all U.S. markets. They are taken from Air Transport (1979). 2 This prediction follows from the generally accepted theoretical model as developed by DeVany (1975) and Douglas and Miller (1974b). I Douglas and Miller (1974a,b) provide some empirical evidence of the inverse relation between the average load factor and the number of firms serving the market using a crosssection sample of city-pair markets operating in the United States. Similarly, DeVany (1975) provides some preliminary empirical tests of his model and finds the results to be generally consistent with these theoretical propositions.

A Robust Adaptive Quantizer

A popular method of time-varying quantization involves a multlplicative change in quantizer overload point after each sample time. Although this technique produces an average loading factor that is invariant with rms input, it is vulnerable to transmission errors. Here, we introduce a related quantizer which has the advantage of disipating the effects of transmission errors at any desired rate. On the other hand, adaptation is not perfect. The loading factor now depends on rms input and in designing the quantizer one must compromise between the goal of constant loading factor and the goal of rapid error dissipation. We provide a design method and apply it to the modification of a quantizer currently used for speech. The new quantizer dissipates transmission errors with a 5 ms time constant while maintaining accurate adaptation over a 40 dB input range.