Design and Optimization of Control Strategies and Parameters by Building and System Simulation

Control parameters for HVAC systems are usually set during the Initial Commissioning Process within the Acceptance Phase of buildings. The quality of the Testing, Adjusting and Balancing (TAB) depends primarily on the specifications of the designer and on the knowledge of the constructor (commissioning personnel). Often the TAB and thus the Initial Commissioning is considered as completed after the functionality and performance of the systems are proven. Therefore, further optimization concerning the energy consumption does not take place. The building and system simulation usually is used during the pre-design of buildings to determine and optimize the influence of the building envelope relating to the energy demand for heating and cooling. Furthermore it is sometimes used for dimensioning the HVAC systems and particular components during the design phase. Additional abilities of the simulation models to predict or even control the building operations are not used. The purpose of the chosen approach is to use the dynamic building and system simulation to design and verify control strategies and determine the exact setup for the control parameters. Therefore the models from the former design phases have to be adapted and extended so that the control strategies can be considered in the right way. This paper presents an example how to use the dynamic simulation to optimize the characteristic of a heating and cooling system of a school building. DESCRIPTION OF THE PROJECT Within the new development of a building for the Gebhard-Mueller-School (GMS), a vocational school center in Biberach (Southern Germany), a very challenging project was created. With limited means a innovative building with a high technical standard and a low energy demand should be built. First meetings with the owner, the future occupants, the architect and the design engineers were held in summer 2001. The building will be ready for occupancy in summer 2004. A depiction and the current state of the building site (August 2003) are shown in Figure 1 and Figure 2. General Building Characteristics The following general building characteristics are given: • 3-story school building for 1,200 students • gross floor area 10,000 m2 (107,640 ft2) • mechanical ventilation system for entire building • heating and cooling by embedded coils in the floors and ceilings Figure 1. Depiction of Gebhard-Mueller-School. Figure 2. Current state of building site (August 2003) ESL-IC-03-10-35 Proceedings of the Third International Conference for Enhanced Building Operations, Berkeley, California, October 13-15, 2003 Energy Performance Target Values Even before any design process had started, the building owner defined a high energy efficiency standard for the building when he published the target of a "2-liter-building". This target of 2 liters of fuel oil per square meter and year means an energy consumption of 20 kWh/(m2·a) for heating, ventilation, and cooling . [1] Due to the limited budget for the building construction and the heating and ventilation system this target was increased to a value of less than 30 kWh/m2a, what is still an ambitious value. By law, the maximum allowable energy consumption for heating and ventilation for this building is 60 kWh/(m2·a).