Improved hydronic loop system solution algorithm with a zone-coupled horizontal ground heat exchanger model for whole building energy simulation

Abstract

Whole building energy simulation is a simulation platform which includes any number of aspects of a building. These tools are generally capable of simulating zones, air systems, hydronic systems, electric generation systems, among others. This simulation environment can be leveraged when investigating the integration between simulation domains. This research effort consists of three main foci, each of which is related to the concept of integration of simulation systems, within the context of whole building energy simulation.

A new hydronic system solution algorithm is developed and implemented in EnergyPlus which integrates the component and system simulation models, providing a flexible and robust simulation.

The effects of transport delay in a piping system are investigated, with experimental data being taken at a horizontal borehole test site. Experimental validation implies that transport delay effects can be predicted using a blended set of model results. Bounding studies demonstrate that the effects on a hydronic loop are less sensitive on a particular transport delay model, and more sensitive to the overall loop topology and configuration.

A ground heat exchanger model that integrates the hydronic simulation model, a ground simulation domain, and zone heat balance calculations is developed. The ground heat exchanger model was validated against experimental data to a high degree of accuracy using a coarse grid, providing a low computational burden suitable for implementation in a whole building energy simulation shell.