Plant optimization program (POP) and its application in rate model for a large district energy and combined beat and power system
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District energy systems provide commercial and residential space heating, air conditioning, domestic hot water, steam, and industrial process energy, as well as sometimes co-generating electricity in systems. Though the district energy system is usually more economical and energy-efficient than individual heating and cooling systems, it is also much more complicated system. The dynamics of the energy markets, changes of building and whole campus load profiles, and increasing discretion of the end users under increasingly higher utility cost make it more challenging for the facility to better plan its operation, such as develop budget for new fiscal year and generate bills for its customers. Therefore, a thorough understanding of the whole system operation, interactions among buildings' load fluctuations and plant operation, impact of the energy price on rates of utilities it produced, and balance between energy efficiency and operation cost, is critical. A reliable thermo-economical simulation model for the existing district energy combined heat and power plants can be a very powerful analysis tool in assisting decision-making of the facility management. This paper discusses the results of efforts to develop the Plant Optimization Program (POP), a program specifically designed to conduct thermal and economical analysis and optimzation for a large district energy and combined heat and power system. Following the description of the conceptual model and procedures developed for the thermo-economic simulation, this paper presents the modeling techniques, cost allocation principles, and optimization principles adoped by the POP. Then this paper presents the Rate Model, an application of the POP to a large university campus in central Texas for energy budget and cost allocation for billing purposes.