Optimal Operational Planning of Cogeneration Systems With Thermal Storage by the Decomposition Method

1995 ◽  
Vol 117 (4) ◽  
pp. 337-342 ◽  
Author(s):  
R. Yokoyama ◽  
K. Ito
Keyword(s):  
Energy Demand ◽  
Decomposition Method ◽  
Large Scale ◽  
Numerical Study ◽  
Thermal Storage ◽  
Operational Planning ◽  
Mixed Integer ◽  
Operational Cost ◽  
Cogeneration System ◽  
Method Effects

An optimal operational planning method is proposed for cogeneration systems with thermal storage. The daily operational strategy of constituent equipment is determined so as to minimize the daily operational cost subject to the energy demand requirement. This optimization problem is formulated as a large-scale mixed-integer linear programming one, and it is solved by means of the decomposition method. Effects of thermal storage on the operation of cogeneration systems are examined through a numerical study on a gas engine-driven cogeneration system installed in a hotel. This method is a useful tool for evaluating the economic and energy-saving properties of cogeneration systems with thermal storage.

A Revised Decomposition Method for MILP Problems and Its Application to Operational Planning of Thermal Storage Systems

1996 ◽  
Vol 118 (4) ◽  
pp. 277-284 ◽  
Author(s):  
R. Yokoyama ◽  
K. Ito
Keyword(s):  
Linear Programming ◽  
Heat Supply ◽  
Decomposition Method ◽  
Large Scale ◽  
Storage Systems ◽  
Heat Supply System ◽  
Thermal Storage ◽  
Supply System ◽  
Operational Planning ◽  
Mixed Integer

A revised decomposition method for solving large-scale mixed-integer linear programming (MILP) problems with block angular structure is presented to efficiently conduct the operational planning of thermal storage systems. The fundamental algorithm adopted here is composed of solving large-scale linear programming (LP) master problems by the Dantzig-Wolfe decomposition method and small-scale MILP subproblems by the branch and bound method, and these problems are solved repeatedly until an optimality or suboptimality criterion is satisfied. As one of the revision strategies to improve computation efficiency, a two-phase approach is introduced, by which a next LP master problem can be solved efficiently by utilizing the results of a previous one. An illustrative example on a heat supply system for district heating and cooling is given to show the effectiveness of the above revision strategy. A practical example on a heat supply system with multiple thermal storage tanks for brewing is also presented.

Operational Strategy of a Cogeneration System Under a Complex Utility Rate Structure

1996 ◽  
Vol 118 (4) ◽  
pp. 256-262 ◽  
Author(s):  
R. Yokoyama ◽  
K. Ito
Keyword(s):  
Energy Demand ◽  
Large Scale ◽  
Numerical Study ◽  
Mixed Integer ◽  
Planning Problem ◽  
Total Utility ◽  
Operational Strategy ◽  
Rate Structure ◽  
Cogeneration System ◽  
Utility Rate

An operational planning problem for a cogeneration system is discussed under a complex utility rate structure which imposes demand charges due to total utility consumption over a specified period as well as demand and energy charges due to hourly utility consumption. Operational strategy of constituent equipment and contract demands for total utility consumption are assessed so as to minimize the operational cost over the period subject to energy demand requirement. This problem is formulated as a large-scale mixed-integer linear programming (MILP) one, and it is solved efficiently by a revised decomposition method for MILP problems with block angular structure. Through a numerical study on a gas engine-driven cogeneration system installed in a hotel or an office building, the effect of rate structure on operational strategy is clarified.

Optimal Operation of a Gogeneration Plant in Consideration of Equipment Startup/Shutdown Cost

1999 ◽  
Vol 121 (4) ◽  
pp. 254-261 ◽  
Author(s):  
R. Yokoyama ◽  
K. Ito
Keyword(s):  
Energy Supply ◽  
Large Scale ◽  
Numerical Study ◽  
District Heating ◽  
Computation Time ◽  
Optimal Operation ◽  
Operational Planning ◽  
Mixed Integer ◽  
Planning Problem ◽  
Operational Strategy

A rational method of determining the operational strategy of energy supply plants in consideration of equipment startup/shutdown cost is proposed. The operational planning problem is formulated as a large-scale mixed-integer linear programming one, in which on/off status and energy flow rates of equipment are determined so as to minimize the sum of energy supply and startup/shutdown costs over the period considered. By utilizing a special structure of the problem, an algorithm of solving the problem efficiently is proposed. Through a numerical study on the daily operational planning of a gas turbine cogeneration plant for district heating and cooling, the effectiveness of the proposed algorithm, is ascertained in terms of computation time, and the influence of equipment startup/shutdown cost on the operational strategy and cost is clarified.

scholarly journals Optimal Operation of a Gas Turbine Cogeneration Plant in Consideration of Equipment Startup/Shutdown Cost

1997 ◽  
Author(s):  
Ryohei Yokoyama ◽  
Koichi Ito
Keyword(s):  
Gas Turbine ◽  
Energy Supply ◽  
Large Scale ◽  
Numerical Study ◽  
Optimal Operation ◽  
Operational Planning ◽  
Mixed Integer ◽  
Planning Problem ◽  
Cogeneration Plant ◽  
Operational Strategy

A rational method of determining the operational strategy of energy supply plants in consideration of equipment startup/shutdown cost is proposed. The operational planning problem is formulated as a large-scale mixed-integer linear programming one, in which on/off status and energy flow rates of equipment are determined so as to minimize the sum of energy supply and startup/shutdown costs over the period considered. By utilizing a special structure of the problem, an algorithm of solving the problem efficiently is proposed. Through a numerical study on the daily operational planning of a gas turbine cogeneration plant for district heating and cooling, the effectiveness of the proposed algorithm is ascertained in terms of computation time, and the influence of equipment startup/shutdown cost on the operational strategy and cost is clarified.

scholarly journals Experimental and Numerical Study of a Microcogeneration Stirling Unit under On–Off Cycling Operation

Energies ◽  
2021 ◽  
Vol 14 (4) ◽  
pp. 801
Author(s):  
Gianluca Valenti ◽  
Aldo Bischi ◽  
Stefano Campanari ◽  
Paolo Silva ◽  
Antonino Ravidà ◽  
...  
Keyword(s):  
Numerical Study ◽  
Thermal Storage ◽  
Primary Energy ◽  
Operational Cost ◽  
Cogeneration Plant ◽  
Economic Optimization ◽  
Viable Option ◽  
Heating Value ◽  
Energy Flows

Stirling units are a viable option for micro-cogeneration applications, but they operate often with multiple daily startups and shutdowns due to the variability of load profiles. This work focused on the experimental and numerical study of a small-size commercial Stirling unit when subjected to cycling operations. First, experimental data about energy flows and emissions were collected during on–off operations. Second, these data were utilized to tune an in-house code for the economic optimization of cogeneration plant scheduling. Lastly, the tuned code was applied to a case study of a residential flat in Northern Italy during a typical winter day to investigate the optimal scheduling of the Stirling unit equipped with a thermal storage tank of diverse sizes. Experimentally, the Stirling unit showed an integrated electric efficiency of 8.9% (8.0%) and thermal efficiency of 91.0% (82.2%), referred to as the fuel lower and, between parenthesis, higher heating value during the on–off cycling test, while emissions showed peaks in NOx and CO up to 100 ppm but shorter than a minute. Numerically, predictions indicated that considering the on–off effects, the optimized operating strategy led to a great reduction of daily startups, with a number lower than 10 per day due to an optimal thermal storage size of 4 kWh. Ultimately, the primary energy saving was 12% and the daily operational cost was 2.9 €/day.

Analysis of Optimal Unit Numbers and Sizes for Microturbine Cogeneration Systems

2004 ◽  
Author(s):  
Satoshi Gamou ◽  
Koichi Ito ◽  
Ryohei Yokoyama
Keyword(s):  
Energy Demand ◽  
Large Scale ◽  
Maximum Energy ◽  
Mixed Integer ◽  
Small Scale ◽  
Optimization Approach ◽  
Operational Strategies ◽  
Energy Demands ◽  
Exhaust Heat ◽  
Annual Total

The relationships between unit numbers and capacities to be installed for microturbine cogeneration systems are analyzed from an economic viewpoint. In analyzing, an optimization approach is adopted. Namely, unit numbers and capacities are determined together with maximum contract demands of utilities such as electricity and natural gas so as to minimize the annual total cost in consideration of annual operational strategies corresponding to seasonal and hourly energy demand requirements. This optimization problem is formulated as a large-scale mixed-integer linear programming one. The suboptimal solution of this problem is obtained efficiently by solving several small-scale subproblems. Through numerical studies carried out on systems installed in hotels by changing the electrical generating/exhaust heat recovery efficiencies, the initial capital cost of the microturbine cogeneration unit and maximum energy demands as parameters, the influence of the parameters on the optimal numbers and capacities of the microturbine cogeneration units is clarified.

An Optimal Operational Advisory System for a Brewery’s Energy Supply Plant

1994 ◽  
Vol 116 (1) ◽  
pp. 65-71 ◽  
Author(s):  
K. Ito ◽  
T. Shiba ◽  
R. Yokoyama ◽  
S. Sakashita
Keyword(s):  
Mixed Integer Linear Programming ◽  
Energy Supply ◽  
Numerical Solutions ◽  
Numerical Study ◽  
Optimal Solution ◽  
Mixed Integer ◽  
Operational Cost ◽  
Hierarchical Approach ◽  
Advisory System ◽  
Integer Linear Programming Problem

An optimal operational advisory system is proposed to operate rationally a brewery’s energy supply plant from the economical viewpoint. A mixed-integer linear programming problem is formulated so as to minimize the daily operational cost subject to constraints such as equipment performance characteristics, energy supply-demand relations, and some practical operational restrictions. This problem includes lots of unknown variables and a hierarchical approach is adopted to derive numerical solutions. The optimal solution obtained by this method is indicated to the plant operators so as to support their decision making. Through the numerical study for a real brewery plant, the possibility of saving operational cost is ascertained.

Optimal Operation of a Gas Turbine Cogeneration Plant in Consideration of Equipment Minimum Up and Down Times

2013 ◽  
Vol 135 (7) ◽  
Author(s):  
Ryohei Yokoyama
Keyword(s):  
Gas Turbine ◽  
Energy Supply ◽  
Numerical Study ◽  
Optimal Operation ◽  
Operational Planning ◽  
Mixed Integer ◽  
Cogeneration Plant ◽  
Operational Strategies ◽  
Operational Strategy ◽  
District Energy

It has become important for operators to determine operational strategies of energy supply plants appropriately corresponding to energy demands varying with season and time from the viewpoints of economics, energy saving, and reduction in CO2 emission. Especially, cogeneration plants produce heat and power simultaneously, which increases alternatives for operational strategies. This makes it more important for operators to determine operational strategies of cogeneration plants appropriately. In this paper, for the purpose of assisting operators or operating plants automatically, an optimal operational planning method based on the mixed-integer linear programming is developed to determine the operational strategy of equipment so as to minimize the operational cost, in consideration of equipment minimum up and down times for each piece of equipment to be operated with appropriate numbers of startups and shutdowns. In the numerical study, the proposed method is applied to the daily operational planning of a gas turbine cogeneration plant for district energy supply. It is clarified how the constraints for minimum up and down times affect the operational strategy and cost. Through the study, the validity and effectiveness of the proposed method is ascertained.

Optimal Configuration Design of Gas Turbine Cogeneration Plants by a MILP Decomposition Approach

2007 ◽  
Author(s):  
Ryohei Yokoyama
Keyword(s):  
Gas Turbine ◽  
Gas Turbines ◽  
Large Scale ◽  
Numerical Study ◽  
Optimal Configuration ◽  
Mixed Integer ◽  
Configuration Design ◽  
Design Problems ◽  
Decomposition Approach ◽  
Energy Demands

To attain the highest economic and energy saving characteristics of gas turbine cogeneration plants, it is necessary to rationally determine capacities and numbers of gas turbines and auxiliary equipment in consideration of their operational strategies corresponding to seasonal and hourly variations in energy demands. Some optimization approaches based on the mixed-integer linear programming (MILP) have been proposed to such configuration design problems of energy supply plants. However, with increases in the numbers of the equipment which must be considered as candidates as well as the periods which must be set for variations in energy demands, the optimal configuration design problems become too large-scale and complex to solve. The author has proposed a MILP decomposition approach to obtain quasi-optimal solutions of the optimal configuration design problems in reasonable computation times. However, this approach has been limited to the optimal configuration design problems where equipment capacities are treated continuously. In this paper, the MILP decomposition approach is extended to the optimal configuration design problems where equipment capacities are treated discretely. The effectiveness of this extended approach is investigated through a numerical study on a gas turbine cogeneration plant.

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