When is increasing consumption of common property optimal? Sorting,congestion and entry in the commons

First-best pricing or assignment of property rights for rival and non-excludable goods is often infeasible. In a setting where the social planner cannot limit total use, we show that common-property resources can be over or under-consumed. This depends on whether the external benefits of reallocating users to less congested resources outweigh the additional costs imposed by new entrants. Importantly, we show that it may be optimal to encourage consumption of some common property resources. Our results have important implications for settings ranging from fisheries and forestry to recreational demand and transportation.     

Multi-objective-based optimal transmission switching and demand response for managing congestion in hybrid power systems

ABSTRACT

This paper proposes a novel congestion management (CM) approach by using the optimal transmission switching (OTS) and demand response (DR) for a system with conventional thermal generators and renewable energy sources (RESs). In this paper, wind and solar PV units are considered as the RESs. The stochastic behavior of wind and solar PV powers are modeled by using the appropriate probability density functions (PDFs). The proposed CM methodology simultaneously optimizes the generation dispatch, demand response, and also the network topology of the power system. The OTS identifies the branches that should be taken out of service by significantly reducing the operating cost of the system while respecting the system security. Here, the total operating cost minimization/social welfare maximization and system losses minimization are considered as the objectives to be optimized. The proposed CM problem is solved using the multi-objective Jaya algorithm and it is used to determine a set of Pareto-optimal solutions. The Jaya algorithm is simple and it does not have any algorithmic-specific parameters to be tuned. This aspect reduces the designer’s effort in tuning the parameters to arrive at the optimum objective function value. A fuzzy logic-based approach is used to identify the best compromise solution. The effectiveness of the proposed CM approach is examined on modified IEEE 30 and practical Indian 75 bus test systems. The obtained simulation results are analyzed and they show the effectiveness of the proposed approach.     

Traffic congestion and ozone precursor emissions in Bilbao (Spain)

GOAL. SCOPE. BACKGROUND: In urban environments, the measured levels of ozone are the result of the interaction between emissions of precursors (mainly VOCs and NOx) and meteorological effects. In this work, time series of daily values of ozone, measured at three locations in Bilbao (Spain), have been built. Then, after removing meteorological effects from them, ozone and traffic data have been analyzed jointly. The goal was to identify traffic situations and link them to ozone levels in the area of Bilbao. METHODS: To remove meteorological effects from the selected ozone time series, the technique developed by Rao and Zurbenko was used. This is a widely used technique and, after its application, the fraction obtained from a given ozone time series represents an ozone forming capability attributable to emissions of precursors. This fraction is devoid of any meteorological influence and includes only the apportion of periodicities above 1.7 years. In the case of Bilbao, the ozone fractions obtained at three locations have been compared on that time scale with traffic data from the area. RESULTS AND DISCUSSION: For the 1993-1996 period, a regression analysis of the ozone and traffic fractions due to periodicities above 1.7 years (long-term fractions), shows that traffic is the main explanatory factor for ozone with R2 ranging from 0.916 to 0.996 at the three locations studied. Analysis of these longterm fractions has made it possible to identify two traffic regimes for the whole area, associated to different profiles of ozone forming capability. The first one favors low ozone forming capability, and is associated with a situation of fluent traffic. The second one shows high ozone forming capability and represents congestion. Joint analysis of raw data of ozone and traffic do not show any clear pattern due to the strong masking effects that seasonal-meteorological effects (mainly radiation) have on the measured ozone signal. If only immission data of ozone are available, as in this case, a comparison between ozone and traffic can only be made on the long-term time scale, since that is the only fraction embedded in the ozone time series that can exclusively be attributed to emissions of precursors. This fact stresses the need to study the different fractions embedded in the time series of ozone measured levels separately. CONCLUSION: Though the coefficients obtained in the regression are only valid for the 1993-1996 period, these traffic regimes represent long-term targets (congestion or fluent traffic) that can inspire policies for a joint management of the traffic and pollution by ozone in the area of Bilbao beyond that period. RECOMMENDATIONS AND OUTLOOK: The results of this work show the need of a joint management of ozone and traffic in Bilbao. Since an accurate knowledge of traffic was not available, the use of emission factors to relate traffic and actual ozone levels has not been possible. For this reason, this study has focused on the long-term fractions of traffic and ozone. In the future, if a more accurate knowledge of traffic is available, it will be possible to find relationships between traffic and ozone on all time scales.     

Wider roads, more cars

The transport policy currently followed in many European cities seems to be a combination of investments in public transport in order to increase, or at least maintain, its market share, and road building in order to keep up with expected traffic growth. Apparently, there is a prevalent belief among policy makers that increased road capacity in urban areas does not in itself cause any growth in car traffic worth mentioning. Such a belief neglects the simple economic theory of supply and demand, as well as more specific theories about the dynamics of traffic under congested conditions. An empirical study of commuting patterns in two transport corridors in Oslo, Norway, shows that a considerable proportion of commuters are sensitive to changes in the speed of the respective modes of transportation. The mode chosen depends to a large extent on the ratio of door-to-door travel times by car and transit. Freer flowing traffic in the road network will induce a higher proportion of commuters to travel by car. Conversely, faster public transport will reduce the proportion of car commuters, but the effects of such improvements will be offset if road capacity is simultaneously increased. In addition to the relative speeds of car and transit, the parking conditions at the workplace are of great importance to the choice of transport mode.     

The effect of vent size and congestion in large-scale vented natural gas/air explosions

A typical building consists of a number of rooms; often with windows of different size and failure pressure and obstructions in the form of furniture and décor, separated by partition walls with interconnecting doorways. Consequently, the maximum pressure developed in a gas explosion would be dependent upon the individual characteristics of the building. In this research, a large-scale experimental programme has been undertaken at the DNV GL Spadeadam Test Site to determine the effects of vent size and congestion on vented gas explosions. Thirty-eight stoichiometric natural gas/air explosions were carried out in a 182 m³ explosion chamber of L/D = 2 and K_A = 1, 2, 4 and 9. Congestion was varied by placing a number of 180 mm diameter polyethylene pipes within the explosion chamber, providing a volume congestion between 0 and 5% and cross-sectional area blockages ranging between 0 and 40%. The series of tests produced peak explosion overpressures of between 70 mbar and 3.7 bar with corresponding maximum flame speeds in the range 35–395 m/s at a distance of 7 m from the ignition point. The experiments demonstrated that it is possible to generate overpressures greater than 200 mbar with volume blockages of as little as 0.57%, if there is not sufficient outflow through the inadvertent venting process. The size and failure pressure of potential vent openings, and the degree of congestion within a building, are key factors in whether or not a building will sustain structural damage following a gas explosion. Given that the average volume blockage in a room in a UK inhabited building is in the order of 17%, it is clear that without the use of large windows of low failure pressure, buildings will continue to be susceptible to significant structural damage during an accidental gas explosion.     

Detonation transition criteria from the interaction of supersonic shock-flame complexes with different shaped obstacles

The present study is an experimental investigation of the last stages of the deflagration-to-detonation transition. A fast flame following a lead shock was generated by passing a detonation wave through a perforated plate. The shock flame complex then interacts with an obstacle of different shape. We study the influence of the obstacle shape on the transition mechanism to a detonation. The obstacles studied are a single round or square obstacle, a flat plate, a C-shaped and an H-shaped obstacle. The experiments were performed in a thin transparent channel permitting high speed schlieren visualization. Stoichiometric propane-oxygen was investigated at sub-atmospheric conditions. For each obstacle configuration, the initial pressure was changed to modify the flame burning velocity and the Mach number of the leading shock. The burning velocity prior to the interaction was measured experimentally from the displacement velocity of the flame in the videos. This required estimating the speed of the gas ahead of the flame. A linear correction to the speed immediately behind the lead shock was applied using the shock change equations and the measured pressure gradient behind the lead shock in order to account for the non-steadiness of the lead shock and viscous losses to the walls. Three main findings were that the obstacle shape had a minimal influence on the critical flame strength required for transition, although obstacles with a forward facing cavity were able to suppress the transition by isolating the re-initiation event inside the cavity. The main transition mechanism for all geometries was the enhancement of the flame burning velocity through the flame interaction with the shock reflected on the obstacle leading to Richtmyer-Meshkov instability. Finally, it was found that the flame burning velocity of the initial flame required for transition was closely approximated by the Chapman-Jouguet burning velocity. Consistent with the visual observations, this supports the view that transition is favored when the flame is in phase with the acoustic waves, and strong internal pressure waves can be amplified.     

The costs of congestion and wilderness recreation

Existing research on the effects of congestion in wilderness areas suffers from problems associated with asking people directly what they would be willing to pay to avoid congestion under hypothetical circumstances. The work reported here is based on methodologies that infer conclusions from observed behavior. Two inferential methodologies are used to examine visitors' willingness to pay at three California wilderness areas during peak and off-peak use periods. Inferential methodologies do not provide unambiguous measures of consumer surplus. However, they do yield the conclusion that, with the exception of a relatively few individuals, solitude is not of overriding importance. Convenience of timing and the attributes of different wilderness areas appear to be more important than congestion.     

Application of the TNO multi-energy and Baker-Strehlow-Tang methods to predict hydrogen explosion effects from small-scale experiments

Analytical models or abacus are of importance to predict explosion effects in open and congested areas for industrial safety reasons. The goal of this work is to compare overpressure and flame speed values of small-scale deflagration experiments to predicted values from the TNO multi-energy (TNO ME) method and the Baker-Strehlow-Tang (BST) method. Experiments were performed in cylindrical congested volumes of hydrogen – air mixtures varying from 1.77 L to 7.07 L. The reactivity was controlled by the equivalence ratio of hydrogen-air mixtures, ranging from 0.5 to 2.5. The congestion was realized with varying numbers of grid layers and configurations. The influence of the obstacle density and the importance of the mixture reactivity to choose the strength index in order to predict the effects of an explosion has been highlighted for the TNO ME method. Predictive flame speed values from the BST method are in accordance with almost half of the experimental results and the method is conservative in most tested configurations. The use of the TNO ME method has been validated on a small-scale experiment to predict maximal overpressures generated by the deflagration of medium and large-scale H₂/air clouds.