《世界能源展望2009》对我国的启示

本文分析了《世界能源展望2009》中有关450情景对我国参与气候变化的主要影响,指出该情景的减排基准过高,情景中描述的全球减排协议标准对我国工业及交通行业发展影响巨大,所规定的从2021年开始给主要发展中国家实施碳排放总量限额将全面影响我国经济发展。     

The scenario approach for Stochastic Model Predictive Control with bounds on closed-loop constraint violations

Many practical applications in control require that constraints on the inputs and states of the system are respected, while some performance criterion is optimized. In the presence of model uncertainties or disturbances, it is often sufficient to satisfy the state constraints for at least a prescribed share of the time, such as in building climate control or load mitigation for wind turbines. For such systems, this paper presents a new method of Scenario-Based Model Predictive Control (SCMPC). The basic idea is to optimize the control inputs over a finite horizon, subject to robust constraint satisfaction under a finite number of random scenarios of the uncertainty and/or disturbances. Previous SCMPC approaches have suffered from a substantial gap between the rate of constraint violations specified in the optimal control problem and that actually observed in closed-loop operation of the controlled system. This paper identifies the two theoretical explanations for this gap. First, accounting for the special structure of the optimal control problem leads to a substantial reduction of the problem dimension. Second, the probabilistic constraints have to be interpreted as average-in-time, rather than pointwise-in-time. Based on these insights, a novel SCMPC method can be devised for general linear systems with additive and multiplicative disturbances, for which the number of scenarios is significantly reduced. The presented method retains the essential advantages of the general SCMPC approach, namely a low computational complexity and the ability to handle arbitrary probability distributions. Moreover, the computational complexity can be adjusted by a sample-and-remove strategy.     

Scenario-based analysis of the carbon mitigation potential of 6G-enabled 3D videoconferencing in 2030

Videoconferencing and teleworking have become indispensable for many public and private organizations since the appearance of COVID-19. However, the extent to which the pandemic may have a lasting effect on people’s daily life and work remains to be seen. Poor visual and acoustic quality of online meetings could reactivate old communication patterns in the long term. New technologies such as 6G and 3D holography, offering enhanced video quality and online experience, could further drive virtualization in communication. This article investigates the CO₂ mitigation potential resulting from the partial replacement of business travel by 6G-enabled 3D videoconferencing in Germany in 2030. The carbon footprint calculation combined with scenario analysis has shown significant results when direct and indirect energy effects are considered. In the different scenarios investigated, a virtual conference would cause between 0.2% and 0.9% of the emissions of a mean-distance conference trip taken by a German business traveler. Considering the mitigation potential of all German conference travel in 2030, emissions could be decreased by 2.1 MtCO₂eq (8.9%) and 20.5 MtCO₂eq (88.4%), respectively, compared to 2019 under conservative and optimistic assumptions. In terms of current national total emissions, increasing virtualization of conferences could contribute between 0.3% and 2.8% to the German mitigation efforts.     

Stage- and scenario-wise Fenchel decomposition for stochastic mixed 0-1 programs with special structure

Solving stochastic integer programs (SIPs) is generally difficult. This paper considers a comparative study of stage- and scenario-wise Fenchel decomposition (FD) for two-stage SIPs with special structure. The standard FD approach is based on stage-wise or Benders’ decomposition. This work derives a scenario FD method based on decomposing the SIP problem by scenario and performs a computational study of the two approaches. In particular, two algorithms are studied, stage-wise FD (ST-FD) and scenario-wise FD (SC-FD) algorithms. The algorithms use FD cuts generated based on the scenario subproblem under each decomposition setting to iteratively recover (partially) the convex hull of integer points in the neighborhood of the optimal solution. The L-shaped method is used to solve the LP relaxation of the SIP problem in the ST-FD algorithm, while the progressive hedging algorithm (PHA) is used in the SC-FD algorithm. Computational results on knapsack test instances demonstrate the viability of both approaches towards solving large instances in reasonable amount of time and outperforming a direct solver in most cases. Overall, the ST-FD algorithm provides the best performance in our experiments.     

Game theory based models to analyze water conflicts in the Middle Route of the South-to-North Water Transfer Project in China

This study applied game theory based models to analyze and solve water conflicts concerning water allocation and nitrogen reduction in the Middle Route of the South-to-North Water Transfer Project in China. The game simulation comprised two levels, including one main game with five players and four sub-games with each containing three sub-players. We used statistical and econometric regression methods to formulate payoff functions of the players, economic valuation methods (EVMs) to transform non-monetary value into economic one, cost-benefit Analysis (CBA) to compare the game outcomes, and scenario analysis to investigate the future uncertainties. The validity of game simulation was evaluated by comparing predictions with observations. The main results proved that cooperation would make the players collectively better off, though some player would face losses. However, players were not willing to cooperate, which would result in a prisoners' dilemma. Scenarios simulation results displayed that players in water scare area could not solve its severe water deficit problem without cooperation with other players even under an optimistic scenario, while the uncertainty of cooperation would come from the main polluters. The results suggest a need to design a mechanism to reduce the risk of losses of those players by a side payment, which provides them with economic incentives to cooperate.     

Online assessment of problem solving skills

This overview evaluates the effectiveness of an alternative interactive scenario based assessment system (ISBAS). ISBAS addresses the limitations of traditional assessment methods, allowing students to troubleshoot complex scenarios, ask questions, and make diagnoses through an interactive web interface. The choices the student makes are tracked and scored based on predetermined, objective values. An analysis of student choices/decisions is used to assign a grade/proficiency level and provide the student feedback. ISBAS is efficient, flexible, and objectively evaluates the sophistication of complex knowledge and skills.     

Evaluating the effectiveness of urban energy conservation and GHG mitigation measures: The case of Xiamen city,China

To assess the effectiveness of urban energy conservation and GHG mitigation measures, a detailed Long-range Energy Alternatives Planning (LEAP) model is developed and applied to analyze the future trends of energy demand and GHG emissions in Xiamen city. Two scenarios have been designed to describe the future energy strategies in relation to the development of Xiamen city. The ‘Business as Usual’ scenario assumes that the government will do nothing to influence the long-term trends of urban energy demand. An ‘Integrated’ scenario, on the other hand, is generated to assess the cumulative impact of a series of available reduction measures: clean energy substitution, industrial energy conservation, combined heat and power generation, energy conservation in building, motor vehicle control, and new and renewable energy development and utilization. The reduction potentials in energy consumption and GHG emissions are estimated for a time span of 2007–2020 under these different scenarios. The calculation results in Xiamen show that the clean energy substitution measure is the most effective in terms of energy saving and GHG emissions mitigation, while the industrial sector has the largest abatement potential.     

Stochastic unit commitment of wind farms integrated in power system

Integration of wind power generation creates new concerns for operation engineers in a power system. Unlike conventional power generation sources, wind power generators supply intermittent power due to uncertainty in parameters of wind such as its velocity. This paper presents probabilistic model for load and wind power uncertainty which can be used in operation planning (with durations up to one or two years). A stochastic model is proposed to simulate the status of units that are directly affected by the load and wind power generation uncertainties.     

2020s scenario analysis of nutrient load in the Mekong River Basin using a distributed hydrological model

A distributed hydrological model, YHyM, was integrated with the export coefficient concept and applied to simulate the nutrient load in the Mekong River Basin. In the validation period (1992–1999), Nash–Sutcliffe efficiency was 76.4% for discharge, 65.9% for total nitrogen, and 45.3% for total phosphorus at Khong Chiam. Using the model, scenario analysis was then performed for the 2020s taking into account major anthropogenic factors: climate change, population, land cover, fertilizer use, and industrial waste water. The results show that the load at Kompong Cham in 2020s is 6.3 × 10⁴ tN a^− 1 (+ 13.0% compared to 1990s) and 4.3 × 10³ tP a^− 1 (+ 24.7%). Overall, the noticeable nutrient sources are cropland in the middle region and urban load in the lower region. The installation of waste water treatment plants in urban areas possibly cut 60.6%N and 19.9%P of the estimated increase in the case without any treatment.