Operating Patterns Selection of Dual Combine Cycle Co-generation Power Plant to Achieve the Lowest Cost Using a Non-linear Programming Model

Abstract

At present, natural gas is the main fuel for electricity generation in Thailand. “AAA Co., Ltd.” is a small power producer using natural gas and is a dual power plant which supplies electricity to the Electricity Generating Authority of Thailand and industrial customers. Besides, the steam from power generation is sold to industrial customers. This study aimed to find the optimal patterns of operating the main machines and equipment along with an allocation plan to each industrial customer. A non-linear optimization technique was used to obtain the lowest total cost, i.e. production costs, maintenance costs and opportunity costs under the operation conditions as issued by the Electricity Generating Authority of Thailand. As results, the operating patterns that can be attributed to the lowest total costs are as follows: 1) power plant A1, operated by a gas turbine (GT11), a heat recovery steam generator (HRSG11) and a steam turbine (ST10). The Heat Rate of power plant A1 is 7484.41 BTU per kWh. 2) power plant A2 operated by both gas turbines (GT21 and GT22), both heat recovery steam generators (HRSG21 and HRSG22) and one steam turbine. The Heat Rate of power plant A2 is 7775.29 BTU per kWh. According to this pattern, the company can save 19,620.34 baht per hour or 87,276,183.53 baht per year, accounting for 6.14% of the total cost incurred from the current pattern. Additionally, this study can be extended to other cases including the conditions when a company has more than 2 power plants, when there are more than one steam-electric power customers, or in case of any dual power plants. These findings can also be applied for production planning in other industries in the future.