IBPSA2009

This paper describes an open-source library with component models for building energy and control systems that is based onModelica, an equation-based object-oriented language that is well positioned to become the standard for modeling of dynamic systems in various industrial sectors. The library is currently developed to support computational science and engineering for innovative building energy and control systems.

The simulation of the energy performance of buildings has historically been compartmentalized along the lines separating different disciplines or different analysis tools, despite their interrelations. These interrelations motivate the development of integrated analyses, which has often focused on linking preexisting and independent simulation software together. This paper reports on initial work using a different integration strategy in which the ‘pre-existing and independent software’ all exist in the universe of the model description language Modelica.

Over the past 30 years numerous Building Simulation Codes (BSC) have been developed. Nevertheless, none of them has yet become a “standard”. Focusing the attention on the use of advanced Object-Oriented Modelling, a review of the most used BSC is here carried out. First, new requirements have been investigated.

The aim of this study is to accelerate developments of building simulation programs by using Object- Oriented programming. A reusable generalised scheduler classes and interfaces 1 ) for defining schedules in simulation programs were developed. ITermStructure2) the “interface” for a term structure was developed to make complex term structure general. By using a “Composite-Pattern”, all the  concrete term classes that implements ITermStructure could be integrated into a complex tree structure.

This paper presents simulations of the integral coefficients of performance of a heat pump system coupled with a vertical ground heat exchanger (GHE). The GHE is simulated using different assumptions concerning the heat transfer in the ground, heat exchange between the ground and the brine and vertical variation of the brine temperature. The differences in the predicted performance coefficients of the heat pump system using the GHE as the lower energy source are analysed and shown to be significant.

This paper shows the numerical model of an earth-toair heat exchanger. The system is discretized into “n” sections perpendicular to the exchanger pipe. In each section, conduction is solved using response factor method in order to reduce computational time. Each response factor is calculated using a finite element program that solves 2D conduction problems. The particularity of this problem is that time-constants are very high, making it impossible to use classical properties of response factors to reduce the number of calculations.

Common approaches to the simulation of Borehole Heat Exchangers (BHEs) assume heat transfer in circulating fluid and grout to be in a quasi-steady state and ignore fluctuations in fluid temperature due to transport of the fluid around the loop. However, in domestic ground source heat pump systems, the heat pump and circulating pumps switch on and off during a given hour; therefore the effect of the thermal mass of the circulating fluid and the dynamics of fluid transport through the loop has important implications for system design.

Seasonal storage of solar energy in geothermal boreholes has resurfaced as a means of heating housing communities. Typically, these systems operate at relatively high temperatures leading to high heat losses from the ground storage volume and to low solar collector efficiencies. In this paper, a new seasonal storage strategy is proposed. First, the storage temperature is kept relatively low in order to limit heat losses and improve solar collector efficiencies.

The transfer of energy from the ground to buildings through slabs and basements has long been a point of large errors in simulations. Work to increase the accuracy of this ground-coupled heat transfer was started under IEA Task 34/43. Detailed models of the ground heat transfer process were developed in TRNSYS for the IEA task work and refined further after for project work. The detailed models created for TRNSYS will be discussed in the context of the IEA task work as well as in comparison to the simplified methods used in mainstream energy modeling.

The user’s action is a decisive factor in the energy performance of a building. In this paper is demonstrated the necessity of using more specific user’s profiles (UPs) in simulations of building’s energy performance (EP).  The Spanish Technical Code for Buildings (CTE) offers a unique generic residential UP for all sites in the country. With the purpose of achieving more realistic UP, energy data, obtained during seven  years from more than 700 dwellings, are processed by advanced classification tools (Exclusive SOM).