Optimisation of mechanical systems in an integrated building energy analysis program: part II: thermal storage-based central plant equipment

This is the second of two papers that describe the development of simulation methods for optimally controlled central plant equipment in IBLAST (Integrated Building Loads Analysis and System Thermodynamics). In Part II, the development and implementation of methods for simulating optimally controlled cold thermal storage in a building energy analysis program are described. The goal of optimising a thermal storage system is to minimise the daily energy cost of operating the system. This means that the amount of ice built during off-peak operation, the quantity of ice used to provide cooling, and the time of use and replenishment must be determined. In this research, the optimal control problem was solved by discretising the allowable chiller part load fractions, only allowing a few to be considered at each time step. As a result, an approximate optimal solution could be found with a small number of search paths.