Operation optimization and dynamic simulation of cogeneration systems with thermal energy storage based on an innovative operation strategy for residential applications

The ever increasing energy consumption of buildings, and of harmful CO2 emission, which causes global warming, necessitate the urgent need of energy conservation. Moreover, because of relatively low combustion efficiency and no abatement measures, emission factors of various pollutants, especially the incomplete combustion products, from buildings are much higher than those in other sectors. For these reasons, energy efficiency in buildings is today a prime objective for energy policy at regional, national and international levels. Polygeneration systems, by generating two or more energy products in a single integrated process, can offer potential benefits to humanity and environment, reducing greenhouse-gas emissions, increasing decentralization of energy supply at lower cost, improving energy security, and avoiding energy losses from electricity transmission and distribution networks. Therefore, in recent years such kind of systems has attracted much interest in building and residential sector applications. However, to address sustainability issues properly, it is important to consider the complexity of polygeneration systems due to the interdependence between different energy products, different types of energy resources and energy conversion devices, as well as the inclusion of storage units. Therefore, polygeneration is mainly associated with generation optimization and related to decision making about production strategies of energy systems. The choice of the operational strategy to use has to be made taking into account the objectives to be achieved, the available devices, and the considered time-period, and often it can strongly depend on local energy policies in terms of costs of energy resources, and provided incentives. This thesis presents a novel approach for improving, from the economical point of view, the operation of polygeneration systems, represented by residential natural gas fuelled Combined Heat and Power (CHP) systems. Optimization problems are formulated to find the optimized operation schedule of the CHP systems prime mover, aimed at the maximization of the economic savings obtained from the CHP systems with respect to the separate generation of electricity and heat. The sustainability of such approach is evaluated by means of environmental impact assessments, and its effectiveness is demonstrated through a dynamic simulation.