HVAC system

Energy use in buildings has a significant influence on the global energy demand and environmental impacts. Among all building systems, heating, ventilation, and air conditioning (HVAC) systems are the most energy-intensive in terms of their total energy requirements. The production and operation of HVAC systems have a significant impact on the environment. These systems are also among the largest consumers of natural resources and materials in the building sector.

It is estimated that HVAC systems represent the highest energy consumption (approximately half of the total energy consumed) and one of the highest cost, especially in non-residential buildings. Therefore, that energy consumption in related to the cost of the building, the energy consumption and the thermal comfort.
Although the comfort of the users should be a factor to be aware of, it may not be the only one. It is advisable to have a balance between this variable and energy consumption, because of its impact on the environment and climate change.

The present paper proposes an optimal operational strategy of an actual HVAC system with a seasonal underground thermal storage system using simulation. The simulation is a powerful tool for the system because it is difficult to try various operational methods experimentally in the actual system due to the long heat transfer time in the underground.

The HVAC system in a real building was simulated by the energy simulation tool being developed (Ito et al. 2007, Sugihara et al. 2007). In order to confirm the practical utility of the tool, the studies are conducted on each phase: Program/Planning/ Design  phase, Construction phase, Pilot-Operation phase and Operation phase.

This paper describes the conversion of equipment characteristics into mathematical formulae, verification of the precision of said mathematical formula, and a concrete simulation tool. The main feature of this simulator is that operation of equipment is solved using temperature and flow, not calories. However, the characteristics of equipment are described using as simple a formula as possible. These formula are verified with actual values, and the simulator was confirmed to provide sufficient accuracy for energy management.

The importance of LCEM (Life Cycle Energy Management) has been recognized from the view of life cycle energy saving of sustainable buildings. The purposes of this research are proposal of an LCEM framework and development of prototype HVAC system simulation tools for LCEM. In this paper, necessity of energy simulation tools for LCEM is discussed, and the outline and solution method of the simulation tool are shown.

The airflow network model in EnergyPlus provides the ability to simulate multizone wind-driven airflows. The model is also able to simulate the impacts of forced air distribution systems, including supply and return air leaks. The air distribution system portion of the model is currently applicable for constant-air-volume systems.