Heat recovery system control strategy to meet multiple transient demands

As increasing power generation needs are met with gas turbines, it is clear that exhaust heat recovery presents a considerable opportunity to reduce operational costs and enhance thermal efficiency. Typically, a system may provide power, process heat and cooling. However, each utility may have a daily demand curve with peaks that do not necessarily coincide in time. Hence, it is necessary to devise strategies that ensure meeting the needs of each user continually while maintaining high thermal efficiencies. To study these situations, a dynamic model of a system comprising a gas turbine, a heat recovery steam generator, and absorption machine was developed. The transient response of the system was studied to determine the effects of sudden changes in demand. Two control strategies utilizing proportional integral controls were considered. The first strategy relied on operating the turbine to meet the power required by the consumer. When power demands were low and steam and cooling demands high, a secondary control strategy operated the turbine to meet the steam demands, thus maximizing the thermal efficiency of the systemThe first strategy relied on operating the turbine to meet the power required by the consumer. When power demands were low and steam and cooling demands high, a secondary control strategy operated the turbine to meet the steam demands, thus maximizing the thermal efficiency of the system. System control and stability were tested, including simulation of a power distribution network simulating resistive, capacitance and inductive loads.