| Abstract | The building energy conservation is currently aware and promoted since the realization on energy sources become more intense nowadays. Then, the technologies to encourage energy efficient building operation should be contemplated. The conceivable cooling technologies mentioned are Variable Air Volume (VAV) and Variable Water Volume (VWV). These technologies are questioned whether they are suitable for the condition of Bangkok. Then, the investigations were attempted to prove on such suspect. In this study, there are two parts on the investigation. First is to estimate the energy consumption of the building, particularly on the air-conditioning system. The estimation method bases on the Overall Thermal Transfer Value (OTTV) concept which is presently contained in the Thai Energy Law Promotion Act. And second is the determination of VAV and VWV potential savings and impacts on overall energy consumption when both systems are retrofitted on the building. The Petroleum Authority of Thailand, PTT, Head Office Buildings were assigned to perform in this investigation. The important parameters to achieve electric energy consumption of air-conditioning system and overall energy consumption in PTT buildings for this study compose of System Coefficient of Performance (SCOP) of building cooling system, Overall Thermal Transfer Value (OTTV) for walls in all facades, power consumption of lighting and building equipment, and diversity factors. These parameters were accomplished. It is obvious that energy consumption by the air-conditioning system is the largest portion for PTT buildings and in such system, the dominant factor is the external heat gain component. The simulated study on the retrofitting of existing A/C system with VAV and VWV gain satisfaction that they truly help save energy and improve the overall cooling performance. However, on the investment aspect, VAV requires higher cost than VWV and leads to longer payback period. In the upgrading case of A/C systems in Bangkok, the cooled-air distribution systems of VAV which have been generally constructed do not contribute to the bulk of potential saving as compared to their investments. Therefore, the more preferable solution tends to be on VWV systems since less investments are required which match to the potential saving. |