Study of operational parameters improvement of natural-gas cogeneration plant in public buildings in Thailand

This paper presents two case studies of performance improvement alternatives. The first one is the 52.5 MWe cogeneration plant at the Suvarnabhumi Airport, and the second is the 9.9 MWe cogeneration plant of the government office building complex. Both plants are located in Bangkok. Performance improvements assume changing system design and operational plans during on-peak and off-peak periods with applying chilled water storage for more flexible operation. Such analysis gives opportunity for improvement of plant efficiency, primary energy saving, emission reduction and economical benefits. In case study 1, the selection of new prime mover results in overall efficiency improvement from 48% to 61%, 24% increase of primary energy saving, and 27% improvement of CO2 emission reduction. Significant amount of primary energy is saved 1451 TJ/a and CO2 emission reduction is 129,271 tCO2/a. The profit is increased to 24.80 Million US$/a and the payback period is 4.77 years. In case study 2, the application of chilled water storage leads to maximum profit of 2.63 Million US$/a. The results show that the selection of plant components should be made very carefully in the design stage, as well as that permanent control and optimization of plant operation in the exploitation phase is essential. Economic aspects of cogeneration plants are more sensitive to changeable input parameters than classical separate heat and power generation since cogeneration plants are more complex in the aspects of process configuration and products costs/values (electricity, steam, hot water, and chilled water). Having in mind the future development of the natural gas distribution network in Thailand, it can be estimated that the potential of power generation in public buildings is around 1.3 GWe. Comparing the Thailand total primary energy supply for commercial buildings, it means reduction of about 9.1%.