Ahmet Yucekaya

Scheduling a log transport system using simulated annealing

The log truck scheduling problem under capacity constraints and time window constraints is an NP-hard problem that involves the design of best possible routes for a set of trucks serving multiple loggers and mills. The objective is to minimize the total unloaded miles traveled by the trucks. In this paper, a simulated annealing - a meta-heuristic optimization method - that interacts with a deterministic simulation model of the log transport system, in which the precedence and temporal relations among activities are explicitly accounted for, is proposed. The results obtained by solving a small size problem consisting of four trucks, two mills, three loggers, and four truck trips showed that the best solution could be found in less than two minutes. In addition, the solution method is tested using data provided by a log delivery trucking firm located in Mississippi. The firm operates sixty-eight trucks to deliver loads from twenty-two logging operations to thirteen mill destinations. The routes assigned by a supervisory person are used as a benchmark to compare the manual generated solution to the solution obtained using the proposed method.

Multi-objective Fuel Supply for Coal-fired Power Plants Under Emission, Transportation and Operational Constraints

Coal-fired power plants need to decrease their generation cost in deregulated power markets so as to be selected, dispatched, and compete with other, cheaper, resources. On the other hand, coal prices have risen significantly, and extra costs for SO2 and NOx emission outputs are imposed that force power companies to lower the costs for the fuel-coal supply process. In this article, a multi-objective model for supplier, transportation, and coal order selection is developed for the coal supply of electric power plants in an environment where multiple suppliers, coal contracts, and multimode transportation routes exist. The model simultaneously optimizes multiple objectives such as minimizing purchase, transportation, sulfur dioxide, and nitrogen oxides costs and carbon dioxide and ash outputs of coal. Multi-objective linear programming and analytic hierarchy process are employed to solve the problem. The solution methodology is applied in a case study in the Midwestern United States and the alternative evaluation process is presented. It is shown that the model can be used by the power companies to find a desired solution for their coal supply and hence generate power with coal of lower cost, lower emission, and ash.

Managing Fuel Coal Supply Chains With Multiple Objectives and Multimode Transportation

Abstract: Power companies require sophisticated tools to manage fuel-coal supply chains which include multiple suppliers, coal contracts, and multimode transportation routes. In this article, a multi-objective model which is integrated with multi-attribute decision-making for the selection of suppliers, transportation routes, and coal orders is developed. The model simultaneously optimizes multiple objectives such as minimizing purchase costs, transportation costs, and ash output, and it also presents a decision framework on the selection of suppliers, transportation routes, and coal products that will achieve these objectives. The network and capacity constraints of suppliers and transportation routes are included in the model. The study utilizes multi-objective linear programming and well-known decision rules such as minimax, maximin, and compromise programming, and Analytic Hierarchy Process is employed to determine preferred solutions. The methodology for the solution is illustrated via a case study and an alternative evaluation process is presented. The study demonstrates that the model can be used by power companies to find desired solutions, as it provides an opportunity for the inclusion of the preferences of decision-makers and adjustments of the weights for each objective.Abstract:Power companies require sophisticated tools to manage fuel-coal supply chains which include multiple suppliers, coal contracts, and multimode transportation routes. In this article, a multi-objective model which is integrated with multi-attribute decision-making for the selection of suppliers, transportation routes, and coal orders is developed. The model simultaneously optimizes multiple objectives such as minimizing purchase costs, transportation costs, and ash output, and it also presents a decision framework on the selection of suppliers, transportation routes, and coal products that will achieve these objectives. The network and capacity constraints of suppliers and transportation routes are included in the model. The study utilizes multi-objective linear programming and well-known decision rules such as minimax, maximin, and compromise programming, and Analytic Hierarchy Process is employed to determine preferred solutions. The methodology for the solution is illustrated via a case study an...

Landfill Gas to the Energy Potential of Turkey: A Scenario-based Multi-period Simulation

Turkey is a developing country with increasing power demands and limited energy sources. Municipal solid waste processing, landfilling and utilization of the gas to generate electric power and lower emissions has been used in developed countries for decades, however, it is relatively new in Turkey. The new regulations force municipalities in the country to build landfills to safely store the waste and secure the emission gases. The landfill gas can be utilized to produce energy and heat, or if the quality is high it can be transported to a natural gas pipeline. In this article, an overview of landfill gas-to-energy plants in the world is presented, and the situation in Turkey is analyzed. A multi-period simulation methodology for municipalities is proposed to estimate the potential power generation and amount of methane that can be prevented. The municipalities in Turkey were classified into three categories and a scenario-based simulation is performed to estimate the energy generation and emission reduction that the country can gain if the landfill projects are activated according to the scenarios.

Energy Storage with Pumped Hydrostorage Systems Under Uncertainty

Energy storage is becoming an important problem as the difference between supply and demand becomes sharper and the availability of energy resources is not possible all the time. A pumped hydrostorage system (PHSS) which is a special type of hydroelectric power plant can be used to store energy and to use the water more efficiently. When the energy demand and the energy price are high (peak hours), the water at upper reservoir is used to generate electricity and the water is stored in the lower reservoir. Revenue is gained from the power sale to the market. When the demand and the energy price are low (off-peak hours), the water at lower reservoir is pumped back to the upper reservoir. Cheap electricity is used to pump the water. The hourly market price and water inflow are uncertain. The main objective of a company is to find an operation schedule that will maximize its revenue. The hourly electricity prices and the water inflow to the reservoir are important parameters that determine the operation of the system. In this research, we present the working mechanism of the PHSS to store energy and to balance the load changes due to demand.

A Simulation Approach to Evaluate Operational Economics of Wind Power Investments in Turkey

 Abstract—It is crucial to analyze the wind distribution throughout the year and the expected annual power generation (Mwh) to evaluate a wind power investment. The cut-in and cut-out wind speeds along with the size of the wind turbine should carefully be included to the analysis as they will affect the amount of power generation. On the other hand, the capital cost and cost of power generation each year should be allocated to the economic life of the project using an appropriated discount rate. In this paper, an economic analysis method and a wind simulation approach is developed to evaluate the expected annual power generation of a wind project. The revenue is calculated using expected power amount and the power price (

The operational economics of compressed air energy storage systems under uncertainty

/Mwh) and the net return is found by subtracting the cost. The necessary economic analysis is then performed using net present value and payback method. The weibull distribution is assumed for the wind and operational characteristics of the turbine are included.